New Horizons and Better Practices

Large-scale subassembly tests were conducted to investigate the behavior of an innovative post-tensioned wide flange beam-to-column moment connection for steel moment resisting frames with concrete-filled HSS columns subjected to seismic loading conditions. The connection includes top and seat angles bolted to the beam and column. Strands are placed along the length of the beam, passing through the column and post-tensioned to provide a precompression of the beam against the column. The parameters investigated in the study include the angle thickness, angle gage length, beam flange reinforcing plates, connection shim plates, and post-tensioning force. The test results demonstrate that post-tensioned connections provide excellent elastic stiffness, strength, and ductility under cyclic loading, with energy dissipation occurring primarily in the angles. The connection initial elastic stiffness is comparable to that of a fully restrained welded connection. In addition, the connection has essentially no residual deformation following several cycles of inelastic story drift. Simple design models are developed and verified by the test results for estimating the connection decompression moment and moment capacity, as well as the increase in post-tensioning strand force due to connection deformation.

The use of hollow structural sections (HSS) in the design and construction of truss structures has been a common practice for many years. The ease of constructability and the pleasing aesthetic qualities of HSS construction are the primary reasons for their popularity. In this type of construction, one of the primary challenges for design engineers is the proper design and detailing of the welded connections between the truss chord and branch members. In North America, the applicable connection design specifications have been criticized by the design engineers because of the restrictive limitations on the range of applicability. These limitations often restrict the use of the preferred HSS chord and branch members because they have wall slenderness ratios larger than the limitation of a particular connection design method. To investigate the feasibility of expanding the range of applicability, the geometric parameters of HSS chord and branch members in welded overlap and gap connections need to be investigated.

The behavior of reinforced concrete structures under blast load is analyzed by LS-DYNA. A new load generation method is proposed so that blast load can be applied to large civil engineering structures, such as highway bridges. The influence of time step and mesh size on simulation results is investigated. Three examples including flexural failed beam, brittle failed beam and undamaged column under blast load are presented. Numerical results match reasonably well with experimental data.

The first step in protecting the occupants of a building from the effects of the detonation of an explosive device by a terrorist is to determine the maximum charge weight that the terrorist could reasonably be expected to use. The next step is to determine a set of possible detonation locations that could cause critical design loads on the structure. For each charge weight and location selected, the design engineer typically uses design-manual-, engineering-code- or hydrocode-calculations to predict a deterministic set of pressure-time histories at various locations on the building. The load prediction method used depends primarily on the complexity of the explosive structure geometry. For simple geometries (an explosive charge placed on the ground at a reasonable standoff distance in front of a flat-faced building), the design manual or engineering code approaches are appropriate. For more complicated structures, or for structures very close to other structures, hydrocode calculations may be needed to accurately predict the loads because of shock wave reflection of other structures. Once the loads are predicted, a deterministic dynamic analysis is then performed to predict the response of the building.

In this paper, we will focus on the development of analytic tools for the design of blast-resistant structures that incorporate uncertainties into their use. These tools are often the primary or only means available to practitioners for computing structural responses and selecting design parameters. Such tools need to be specially developed because of the complex behaviors engendered by blast loads, which cannot be captured with conventional analytic models. Moreover, it is more realistic to produce response calculations that are accompanied with uncertainty bands because of the complexities of the behaviors and the uncertainties in the loads—that is, a single deterministic response is inherently misleading as to the actual nature and specificity of realistic threats.

The majority of injuries in a terrorist bombing are due to glass shards. Historically, glazing hazards have been characterized by pressure-impulse (P-i) curves that identify the peak overpressure and impulse levels at which window debris can be classified as being high hazard, low hazard, or non-hazardous. Hazard levels have been defined as a function of the overall distance that fragments are projected from the window. The problem with this "smeared" approach to window hazard characterization is that it fails to take into consideration the mass or shape of window fragments and only indirectly accounts for fragment velocity. The resulting "hazard" characterizations are inaccurate and misleading. Under funding from the Defense Threat Reduction Agency and the Technical Support Working Group, Applied Research Associates addressed this shortfall through a stochastic predictive model, the Shard Fly-Out Model (SFOM), that characterizes the size, shape, and velocity distributions of the shard fields from shock-loaded windows. The model is semi-empirical, based mostly on the data from sixty nine tests of windows performed at the Shock Tube Facility operated by Wilfred Baker Engineering. This paper summarizes the empirical and analytical methods used to develop the SFOM, provides a summary of the distributions used to characterize the window debris-field and offers suggestions for further development and model validation. Additional details on the software coding of the Shard Fly-Out Model are presented in the Technical Documentation, while instructions on the use of the software are presented in the User's Guide.

Performance assessment of blast resistance for buildings which are seismically designed as per code provisions is conducted. These provide a qualitative idea of the performance of seismically designed structures in external blast loading scenarios. These can be used for order of magnitude assessment of blast performance, followed by detailed nonlinear dynamic finite element analyses. For illustration purposes, a representative low-rise RC frame structure is designed to meet current IBC provisions for wind and seismic resistance. The primary loading characteristics of seismic and blast hazard scenarios are parameterized and the level of resistance to blast obtained from seismic design is characterized.

Structures in civil engineering may be analyzed using the displacement method, which is based on a stiffness approach, or the flexibility method, which is based on the flexibility approach. In the displacement method of analysis, the stiffness matrix for a structure is determined based on material and geometrical properties of the members and the connections. The flexibility matrix for a structure is the inverse of the stiffness matrix. This paper examines the fundamental characteristics of the stiffness and flexibility matrices of civil structures based on modal properties, specifically, mode shapes and natural frequencies. Typically, in modal testing of civil structures, only the lowest modes are measured. The modal properties of a damped free structure are examined herein. The stiffness and flexibility matrices of a structure based on limited mode shapes and natural frequencies are examined and compared with the exact analytical matrices. Based on the results of a simple structure, the stiffness matrix is shown to be strongly influenced by the highest "practical" modes, while the flexibility matrix is strongly influenced by the lowest modes. But is this true of more complicated structures? And, what role does this have in terms of Modal Design and Analysis (MDA) of structures? By understanding the modes of vibration, civil engineers can better design structures. The findings are of value to the practicing structural engineering community.

This paper summarizes the technical bases for recent initiatives aimed at providing structural engineering alternatives to the traditional prescriptive approaches to fire safety assurance. As a case in point, Appendix 4 of the 2005 edition of the AISC Specification includes, for the first time, guidance in designing steel-framed building systems and components, including columns, floor and truss assemblies, for fire conditions. The criteria provide for the determination of heat input, thermal expansion, and degradation in strength and stiffness of materials at elevated temperatures that cause progressive decrease in strength and stiffness at elevated temperatures. The design of building components and system that allows designers to address fire-induced structural actions explicitly leads to more robust structural designs for fire conditions.

The Ivana Condominium Tower, which will be referred to as The Ivana for the remainder of this document is a 75 story reinforced concrete structure in design. The residential tower section will stand 973 feet tall and have an 11 story mixed use podium. Figure 1 is a rendering of the Ivana. Figures 2 and 3 provide architectural drawings of an elevation and typical plan.

This paper presents recent progress in the development and implementation of the database-assisted design (DAD) methodology for low-rise buildings. The DAD methodology involves making direct use of pressure time series measured in the wind tunnel, rather than using simplified wind load cases such as those in ASCE/SEI Standard 7-05. To facilitate more widespread implementation of DAD, an aerodynamic database is being assembled at NIST. Procedures and software have been developed to automate the handling of aerodynamic data in the database, and an interpolation scheme has been developed to enable the use of DAD for cases in which a wind tunnel model with matching dimensions is not available in the database. This paper also presents comparisons of peak bending moments computed using DAD with those resulting from the simplified wind load cases in ASCE 7-05. The agreement is found to be quite good for bending moments that were considered in the development of the simplified load cases used in ASCE/SEI 7-05. However, when an intermediate location is considered, the maximum bending moment from DAD is found to be more than twice as large as that from ASCE/SEI 7-05, indicating unconservatism.

Recent trends in the design of tilt-up wall buildings has been toward the use of segmented wall panels that are connected by welded plates at two or three locations over the height of the panel. It has also been suggested that in seismic regions panels should be connected in pairs or at most in groups of three. In both conditions, chord steel at the top if the panel is provided. The purpose of this study is to evaluate the effects of strong ground motions having pulse type displacement characteristics on this type of tilt-up wall construction. In order to investigate the seismic behavior, three dimensional, linear and nonlinear models of a prototype building are developed within the constraints of the computer program, SAP2000. Nonlinear elements are incorporated for the connections of the glulam beams and purlins to the wall panels and the nonlinear behavior of the diaphragm is modeled using a Hrennikoff model of the continuum. A third building model was developed having cast-in-place connections (pilasters) between the panels. This modeling permitted a comparison between the traditional pilaster construction and the more modem segmented wall construction. In addition, the effects of dense nailing and sparse nailing in the diaphragm are considered. Results of these analyses indicate that the use of segmented panels in tilt-up wall construction is a viable procedure for buildings located in seismic regions. However, it is important that tests be conducted on the various connections used to tie the components of this system together and that their strength and ductility in the post yield region be determined. Based on the results of these tests some additional strengthening of critical connections may be required to provide the necessary strength and ductility.

This paper examines the sensitivity of the motions obtained at non-instrumented floors by piece-wise cubic-spline interpolation procedure to the location of instrumented floors. It is found that the cubic-spline interpolation procedure may be used to accurately predict motions at non-instrumented floors of buildings with approximately uniform height-wise distribution of stiffness if the instrumented floors are distributed at regular intervals over the building height. For buildings with very-stiff or very-soft condition at few stories, this interpolation procedure may lead to poor prediction of motions at non-instrumented floors. For such buildings other means of interpolation such as a combination of linear-cubic interpolation should be used.

Beating effects observed in the recorded responses of buildings are examined in this paper. Beating is a periodic, resonating and prolonged vibrational behavior caused by distinctive close coupling of translational and torsional modes of a lightly damped structure. Repetitively stored potential energy during the coupled translational and torsional deformations turns into repetitive vibrational energy causing the ensuing prolonged motions. Beating, if a dominant response characteristic, may impact the instantaneous and long-term shaking performances of the buildings during earthquakes. In many cases, it is noted that resonance caused by site effects also contributes to accentuating the beating effect. Records from the buildings exhibit structural responses with beating effects. Spectral analyses and system identification techniques are used to quantify dynamic characteristics used in computing beating periods. The beat frequency generally known in acoustical physics is denoted by the absolute value of the differences in frequencies that cause the phenomenon. Engineering implications of the beating may be summarized as (a) prolonged cyclic shaking due to beating effect may take its toll on the structural system, (b) repetitive shaking can accentuate fatigue and low-cycle fatigue, and (c) resonating beating cycles can and do cause discomfort to occupants. Identification of beating effects is the key to find remedial action in modification of dynamic characteristics in order to attenuate or eliminate such effects.

When designing buildings for wind loads, both strength and serviceability limits states must be addressed. Codes and specifications such as ASCE 7-05 and the AISC Specification provide mandatory requirements for the strength design, but not for serviceability. This is because strength is a life-safety issue, and serviceability is not. The result of this situation is consistency in design for strength, and inconsistency in design for serviceability. This inconsistency was evident in responses of a practice survey, the results of which were published in 1988. This survey showed very wide discrepancies in loads used for drift calculations, how drift is measured, why drift is limited, what drift limits are used, and what aspects of structural behavior are or are not included in the structural analysis. Many advances have occurred since the survey was taken. These advances include improved understanding of structural and nonstructural behavior, improved mathematical modeling techniques, availability of optimization and sensitivity analysis tools, orders-of-magnitude increases in computational speed and storage capacity, and advances in design philosophy (e.g. performance based design concepts). Because of these advances, the ASCE/SEI Committee on the Design of Steel Building Structures developed a new survey to dermine how the state of the practice in wind drift serviceability design has changed over the past thirty years. This survey, taken in March through July of 2006, was made available on-line and was completed by more than fifty individuals. While the number of respondents was far less than desired, it is felt that a sufficient number of responses were obtained to provide a sense of the current practice. Additionally, the state of the practice may be compared to the committee's assessment of the state of the art, and recommendations can be forwarded to advance both the state of the practice and the state of the art. This paper presents a preliminary overview of the results of the latest survey. A more thorough report is in preparation. The educational level of the respondents for the latest survey was 41 percent bachelor's degree, 46 percent master's degree, and 13 percent Ph.D. Fifty percent of those surveyed was a P.E., and 14 percent indicated that they were licensed as a S.E. Sixty percent of the respondents stated that drift was a common design issue in their firm, 13 percent said it was somewhat common, and 18 percent indicated that designing for wind drift was uncommon. Only twenty percent of those surveyed said that their firm had written procedures for wind drift serviceability related design.

Present day computers and software are powerful tools for the design engineer but require accurate input to produce reliable results. For a given structure there are a number of assumptions regarding structural modeling that affect the building's lateral stiffness. Many of these assumptions, such as included sources of deformation, beam-column joint modeling, composite action, nonstructural components and second order effects are discussed in this paper, which is based on the Master of Science thesis by Berding. The structural system of the analytical building is discussed first, along with the design of the gravity and lateral load resisting system. The lateral loads used for the analysis (not shown herein) were calculated using Method 2 of ASCE 7-05, the Analytical Method. The wind loads were determined for a serviceability based 10 year mean recurrence interval, with no load factor. Finally the analytical models are presented. Points of comparison between the models are made based on displacement vs. height. Observations are made and the relative merits of each model are examined.

Structural engineers practicing in regions of high seismicity have been wrestling with the complexities of designing safe structures to resist seismic activity for 100 years beginning with the rebuilding effort following the 1906 San Francisco earthquake. It is likely that no aspect of structural design is more scrutinized economically and practically while the science of the practice is many years away from being complete. Less than a year after rebuilding efforts commenced in San Francisco, under a new Building Ordinance requiring structures to withstand 10% of their weight applied as a lateral force, contractors and owners were ignoring the requirement, declaring it too costly and/or schedule-impeding to their goals. For the past ten years most structural engineers across the United States, even in regions of low seismicity, have had include seismic design in their structures as a result of the provisions included in IBC following the 1994 Northridge earthquake. If human nature can deflect safeguards recommended by trained professionals while knee-deep in the after-effects of a disaster, imagine the difficulty to integrate these same provisions in areas which have not experienced significant seismic activity in modern times.

A team of design professionals and structural engineers were retained to renovate US Cellular Field in Chicago, Illinois. US Cellular Field is a major league baseball stadium and home of the Chicago White Sox. The structure is a three concourse (or tiered) structure that has seats for approximately 45,000 people including 84 luxury suites located on the middle club level. The stadium was originally built in 1991 for $120 million dollars. The purpose of the renovation was to bring a friendly retro style feeling to the ballpark using structurally exposed elements. The renovation was completed in 2005 at a cost of approximately $70 million dollars. The major points of the renovation included the following: 1 Relocation of both bullpens. 2 Addition of 600 club level seats. 3 Renovation of the batters eye section. 4 Integrate new brick and signage along the concourse areas. 5 Removal of a portion of the upper deck seating area, and addition of a canopy.

In recent years, braced-frame construction has gained considerable popularity for lateral load resisting systems in regions of high seismic activity. Concentrically Braced Frames (CBFs) have been one of the more prominent systems in this classification, relying on the inelastic cyclic buckling and yielding to resist seismic loads and dissipate energy. During tensile cycles, the brace places large demands on the brace-gusset plate, and in turn the gusset plate-beam or column, connections. While failures in this region have not been observed in previous earthquakes, studies suggest that net-section fracture may be a potential mode of failure in these connections. This paper focuses on investigating the inelastic seismic response of typical slotted net section connections of hollow structural sections (HSS) and round pipe under earthquake type monotonic and cyclic loads. Specifically, experimental observations from a Network for Earthquake Engineering Simulation and Research (NEESR) project on nineteen large-scale bracing members in the context of net section performance are presented. In addition to providing insights into behavior, the experiments also serve to validate micromechanics-based modeling approaches that predict ductile fracture. One such approach, utilizing the Void Growth Model (VGM) is discussed and presented as an analytical and general alternative to costly experimentation.

In conventional building design, structural strategies are aimed at creating a cost-effective system that meets the goals of the building owner. With sustainability, the design team introduces the goals of using the right materials, in the right way, to achieve the right building. Several factors that the structural engineer may not have traditionally considered in his or her design become more important, and the structural engineer must more actively integrate the structural aspects of building design with the other building systems and processes that will have an impact on the environment. This paper will discuss some of the key strategies a structural engineer can take to meet the design team sustainability goals, as well as better integrate his or her practice and personal habits into the sustainable building movement. The concept of sustainability is not new. Many engineers who are now principals in their firms saw the passing fads and green movements of the sixties and seventies. Those that experienced this often equate "sustainability" and "green building" with hippies living in structures made of soil, bamboo, or tires. They see the current movement as something similar; something that would be difficult to integrate into their current engineering practice. Even if they think this integration were possible, it would increase the number of non-billable hours, decrease the profitability of their projects, and in the long run, have a negative impact on the bottom line. Other structural engineers have seen the sustainable movement as a great selling point for their firms and clients, as well as a tool to help recruit bright engineers with a vision for a better future. They see this as an opportunity to make a positive difference in their world, while at the same time making more profits for their companies. This is, however, achievable only if the structural engineer makes a commitment to integrating their design with other systems early in the conceptual design process, learning about the elements of sustainability that affect his or her practice, and learning how to educate others on the design team to appropriately integrate the structural engineer in their design decisions.

"Just tell me which the most sustainable material is: Wood, Steel, or Concrete?" Have you ever heard (or asked) a question like this? It epitomizes the problem many engineers have with the study of sustainability; the fact that sustainability is not an inherent property of a material. One cannot attribute a number to sustainability, so there's no modulus of elasticity to measure, no strength-to-weight ratio to compare. And even if you could make an apples-to-apples comparison between materials, somehow comparing the recycled content of steel with the renewable aspect of timber, for example, it would not give a meaningful answer in deciding which material is best for a particular application, or, in our case, a particular building.

Back in the 1960's Bill Cosby made a comedy record album titled "Why is There Air?". The titled routine involved college philosophy majors asking "Why is there air?", and poked fun at the question because as every physical education major knew there was air to "blow up basket balls and volley balls". So it seems in 2007, that to make a case for sustainable design is equally obvious, at least to the "physical education majors" of the architectural and engineering community. But sustainable design has not been wholly embraced and incorporated into every day structural engineering practice, nor into everyday architectural practice, and is only now emerging as a mainstream design philosophy. Tenants of sustainable design are incorporated into today's building codes in only a limited way, in requirements for energy efficiency, and as they apply to structural engineering, not at all. Why do we care about sustainable design, and why do we see at every turn the word "sustainable", in advertisements for financial investments, in descriptions of new office buildings, and as a topic for an entire track of a structural engineering conference? Has the United States, along with the rest of the modern world, reached a point of understanding, where we can no longer deny the impact of modern societies' activities on the organism of life?

Reinforced concrete structural walls are commonly used as the primary lateral-load resisting system in buildings. The research presented here represents the first-phase of a multi-year research effort aimed at developing tools to enable performance-based design of structural walls. The first-phase of the research effort focused on the seismic behavior and analysis of slender planar walls. To design the experimental investigation, including a reference specimen and test matrix: 1) drawings for 18 walls from 10 buildings designed for construction on the west coast since 1991 were reviewed to determine representative design details, 2) practicing engineers were consulted to establish the wall design process for the test specimens, 3) the results of previous experimental studies were reviewed to determine the parameters that control response, and 4) elastic, effective-stiffness analyses of a representative 10-story building were conducted to determine representative load patterns. These results are used to support experimental testing of wall sub-assemblages which will be conducted using the MUST-SIM NEES facility. Data generated from testing and analysis will provide for an improved understanding of wall behavior, provide a basis for advancing simulation and design of walls, and be used to support the subsequent phases of the research effort, and address different wall configurations.

This paper describes the observed nonlinear reversed cyclic behavior of a half-scale precast concrete coupling beam subassembly for seismic regions. In this new system, coupling of concrete walls is achieved using unbonded post-tensioning. The test specimen includes a coupling beam and the adjacent concrete wall regions at a floor level. Under lateral loads, the nonlinear deformations of the coupling beam occur primarily due to the opening of gaps at the beam-to-wall interfaces. Steel top and seat angles are used at the beam ends to yield and provide energy dissipation. Prior to the testing of the specimen, the concrete at one end of the beam had to be patched due to poor consolidation during casting. The beam was able to sustain three cycles of displacement at 6.4% chord rotation and failed during the second cycle to 8% rotation due to the low cycle fatigue fracture of one of the top and seat angles. Most of the damage in the beam was concentrated in the angles (which can be replaced after an earthquake) and the patched concrete. The unpatched end of the beam received almost no damage other than a small amount of cover concrete crushing at the corners. The mild steel reinforcement in the beam performed well throughout the entire displacement history; however, premature fractures of post-tensioning strand wires occurred inside the anchors.

Recent advances in structural engineering have lead to an increased interest in performance-based design of structural systems. Here the performance of reinforced concrete coupled wall systems, designed in accordance with current practice, is investigated. The research presented represents the second phase of an on-going NEESR research effort to advance performance-based design of slender wall systems. The project includes laboratory testing of a series of 1/3-scale wall sub-assemblages that represent the lower three stories of a ten-story building; planar, coupled, c-shaped and core configurations will be considered. This paper focuses on the coupled wall specimens, the performance of the coupling beams, nonlinear finite element modeling methods, and their contribution to the overall performance of the wall system.

Performance-based earthquake engineering was utilized to ascertain the seismic performance of an existing two-story non-ductile reinforced concrete building with a proposed new third floor steel-framed addition. The structure, hereafter referred to as the Capital Unity Center, is located in downtown Sacramento. California, and was designed and constructed in early 1940s per the applicable building codes at the time of construction. Capitol Unity Center is a remodel and addition to an existing warehouse structure and is an integral part of the city's attempt to renovate the older downtown. buildings. The new center will house a museum with space for exhibits, performing area, and workshops. Since the renovation constitutes major structural changes, the structure in the new configuration must comply with the current seismic provisions of the California Building Code. In addition, since the facility and will be used by the California Department of Education, it must comply with the more stringent requirements of the California Division of State Architecture (DSA). Provisions of FEMA 356, ACI 318 and CBC 2001 were used for a detailed investigation. Comprehensive material testing, detailed geotechnical investigations, site-specific seismic hazards, and state-of-the-art nonlinear structural analysis were performed to assess the seismic performance of the building, identify deficiencies, and evaluate efficacy of seismic retrofit techniques. Analysis showed that the existing structural elements with the architectural renovations did not meet the required performance goals. To obtain satisfactory behavior, both the superstructure and substructure have to be retrofitted. In its retrofitted configuration, the building would then meet the performance objectives.

Structural engineers sometimes wonder what they can do to advance the practice of "sustainable" or "green" design. While for building design it is true that the architect and mechanical engineer tend to play larger roles than the structural engineer, the structural engineer can contribute in a number of significant ways. For example, designing efficient structures and using recycled and salvaged materials conserve non-renewable resources. One emerging strategy with far-reaching consequences is Design for Adaptability and Disassembly (DfAD). DfAD may in fact be the most important strategy we can use to conserve materials, thereby reducing the energy consumed and the pollution and global warming gases emitted during their extraction and manufacture. Applying these strategies should greatly increase the probability that (1) the life of the structure will be extended, and (2) at the structure's end-of-life the materials will be reused or recycled. Adaptability is a measure of how easy it is to modify a building during the course of its life. One recent study of demolished buildings in Minnesota found that only about 40% of the demolitions were due to the building's physical condition. The remainder were due to factors such as neighborhood redevelopment and suitability for a desired use. Stewart Brand's book. How Buildings Learn, leads the reader through the lives of many different types of buildings, and demonstrates that most long-lived buildings undergo changes during their lives, such as changes in use, upgrades to facades and mechanical systems, and additions. Buildings that cannot adapt, die. If the costs of making the changes that the building users demand exceed the cost of building from scratch, the older, non-adaptable, building is likely doomed, and the materials in that building either wasted or, at best, recycled. Deconstruction is a demolition method whereby a structure is carefully and methodically disassembled so as to salvage as many components as possible. The goal here is not merely to recycle, but to reuse. Recycling is certainly beneficial, in that it conserves virgin resources, but recycling also can consume large amounts of energy and produce significant pollution. Reuse, on the other hand, requires no re-manufacturing, and therefore has a much lower environmental impact. Often the impact is limited to transportation, such as moving materials from the site of a former use to the site of a new use, perhaps with an intermediate stop at a materials storage site or a refurbisher's shop.

Walter Payton was known on and off the football field as "Sweetness." In 1985, he led the Chicago Bears Football Club to the Superbowl. His thirteen year professional career set the standard for productivity. Following the announcement that he suffered from a rare liver disease, Walter Payton dedicated himself to advocacy of organ transplantation (Walter Payton Cancer Fund). Walter Payton's legacy is remembered through the charity foundation he founded and honorary naming of many public works in Chicago. The indoor practice facility for his team is among those structures honored by his namesake. The Walter Payton Center was constructed in 1997 to provide an indoor protected practice area for the Chicago Bears. At the time, it was the only timber structure in use by the National Football League. By the summer of 2004, water infiltration through the roof had grown from a nuisance to a safety hazard in the eyes of the team ownership. A limited preliminary investigation revealed that the wood substructure had become saturated and was experiencing decay. Appropriately, the plan for remediation of the structure included removing deteriorated sections of timber and transplanting with new material. This paper intends to provide a thorough account of the investigation, design, and construction phases that eventually returned the Walter Payton Center to a state of the art practice facility. First, the background will be set with a thorough description of the existing structure. Then, the investigation into the cause and extent of the timber deterioration will be explored. Much of the repair design and construction happened concurrently as the remediation process uncovered greater extents of deterioration. Throughout the project, the exacting standards of the National Football League were expected of the design and construction team, namely, to provide a quality product in time for the next playing season.

The confidence and competence of any professional is built upon a solid foundation of theory and practical knowledge. For the structural engineer, these building blocks are discovered at a young age through the process of trial and error, as a child learns which shapes carry the greatest number of jelly beans and how to fasten boards together to create an impenetrable fortress against plastic bats and flour bombs. A basic curiosity for how things work and hold together spurs a maturing child to discover more, even to make a profession out of it. It is this curiosity that keeps the profession interesting and helps long-time engineers feel young and somewhat giddy again. Competence in the field of engineering can only increase as one's confidence is built up, beginning with established principles that are learned at the university and continuing with valuable experience gained in all areas of the profession, from business practice to societal involvement.

When people my age were in college, the calculator of necessity was the slide rule. From that statement, you can determine my age and that of my generation. We didn't know at the time but the use of the slide rule was preparing us as students for the life of the engineer with a great intuition as to what made sense relative to decimal point, units, and a gut sense as to the correctness of an answer. A student couldn't take forever to obtain the solution to a homework assignment or a quiz answer and there was no use for a "what if" results should I tinker with this or tinker with that. Rough approximations and rounding of numbers was a way of engineering practice. Within a very few years of starting my career as an Engineer-In-Training and then as a professional engineer Hewlett Packard produced the most amazing (slide rule) calculator. I recall waiting with anticipation as the price came down from over $700 so that I could open the piggy bank to spend $ 435 for my HP. With our background from training with the slide rule, the calculator didn't make us callus, it made us more efficient. We carried into that new electronic generation a strong background in understanding of the principals in getting it right. Then came those huge chugging main frames that produced reams of paper that no one really wanted to look through nor had the time to; we were still using approximations to make sure that we got it right. You may recall sitting in front of the key punch after you worked out your fortran code, essentially writing your own software to analyze a beam. 300 cards later, stuffed into the chugging main frame you had your "what ifs" and thought this is really great. Some of us thought that was the utmost in technology until software engineers began to produce sub routines that we could buy off the shelf and put into the mainframe. As technology ramped up and moved along it warp speed, main frames reduced to desk tops and then to lap tops and now to Black Berry size, along with new problems. Small buttons and small screens, my eye sight has gotten worse and my fingers larger, but that's another story. Education has followed suit with large computer laboratories in engineering schools that require students to work on sophisticated computer equipment having no idea how the equipment was developed, using software they have no clue as to its limitations, and all assisting in the creation of students and instructors having almost blind faith in a console. They apply "what ifs" to engineering problem until they think they've got it right. This can be somewhat unnerving for seasoned practitioners when reviewing work of new hires who have just provided a W8 steel section to span some unusual length without realizing that it is going to be like a spring board. But that being said, technology is fast coming to the engineers aide by putting warnings and flags on output that force the engineer to question what's going on. The new technology is creating in many areas a greater reliance on the black box. But is this wrong? Are we engineering relics responding or reacting in a certain way because our training and development process was different? Astronauts put their total faith in the black box. We think it unbelievable that we are seeing pictures of the surface of Mars sent to us by the Mars Lander, that as adolescences were only stories of fantasy. Every day we step into jet liners that can take off and land without any humor intervention. Bring it closer to home, lift the hood of your car and try to locate the carburetor.

For many years, AISC has published the Seismic Provisions for Structural Buildings, as a companion specification to the main structural steel design specification. Specification for Structural Steel Buildings. The latest editions of these two documents were published in 2005 as ANSI/AISC 341-05 and ANSI/AISC 360-05, respectively. To assist designers in applying the Seismic Provisions, the AISC Seismic Design Manual is a first edition publication by AISC to provide applied design examples illustrating the application of the AISC Seismic Provisions and other Seismic Standards. The Manual, for the most part, focuses on the design of the lateral system for the same simple, regular rectangular bay frame with each of the major braced- and moment-frame lateral system types, in both R = 3 and high-seismic applications. Detailed design examples are provided to highlight special design and detailing requirements for these systems when designed to resist seismic demands. The manual examples are only presented using the LRFD design method; however it should be noted that ASD design is also permitted by the 2005 edition of the AISC Seismic Provisions. In addition to the detailed design examples, the Seismic Design Manual contains general guidance on the basics of seismic design forces and the application of ASCE 7 code requirements using the Equivalent Lateral Force Method. Tables have also been provided for the quick selection of seismically compact sections in various frame configurations, and for the selection of common design variables required for the application of the Seismic Provisions. The final portion of the document discusses the design of other elements, design concepts and systems that are not presented in detail in the first edition of the Manual. These items include the following: 1 Design of diaphragm chords and collectors 2 Discussion how to properly apply the term "Maximum Force that can be Delivered by the System" that is used in the Seismic Provisions 3 Design of Buckling Restrained Braced Frame (BRBF) systems 4 Design of Special Plate Shear Wall (SPSW) systems 5 Design of Special Truss Moment Frame (STMF) systems 6 Design of systems that included supplemental damping elements. The document has been developed to be consistent with ASCE 7-05 Minimum Design Loads for Buildings and Other Structures.

The AISC Seismic Design Manual provides design examples illustrating the application of the AISC Seismic Provisions and other design standards related to the seismic design of structural steel. Though this paper only addresses braced frame systems, the Seismic Design Manual, presents complete examples on the design of braced frame and moment frame systems, in both R = 3 and high-seismic applications. Generally, the examples in the Seismic Manual present the design of lateral systems to support the same simple, regular rectangular building frame (shown below). The Seismic Manual, in its introduction, contains general guidance on the basics of seismic design and the application of ASCE 7 code requirements using the Equivalent Lateral Force method. Tables have also been provided for the quick selection of seismically compact sections in various frame configurations, and for the selection of common design variables required for the application of the Seismic Provisions.

Cold-Formed Steel framing (CFSF) has been used in North America and England since the mid 19^th century. The first design code was published in 1946 by the American Iron and Steel Institute (AISI) with subsequent editions issued as new research was made available. The current edition of the specification covers all types of cold-formed structural members, and a series of framing-specific standards has been developed for building code adoption. These standards, as well as product innovations and market conditions, have helped make CFSF an ideal structural solution for mid-rise construction: hotels, apartments, condominiums, assisted living facilities, dormitories, and other construction with regular, repetitive units in three- to eight-story structures. This paper will discuss the current code-adopted standards for CFSF, and specific examples of mid-rise structures and specific detailing of the structural systems. Details will include using cold-formed steel for bearing walls, floor systems, lateral systems, and other portions of the structure. The integration of CFSF with other types of structural elements, such as wood roof framing and structural steel for lateral systems, will be discussed as well.

A proposed supplement to ASCE/SEI 41 Seismic Rehabilitation of Existing Buildings has been developed for the purpose of updating provisions related to existing reinforced concrete buildings. The proposed revisions are primarily based on new research presented at an EERI/PEER technical seminar series titled, "New Information on the Seismic Performance of Existing Concrete Buildings." The proposed supplement includes revisions to modeling parameters and acceptance criteria for reinforced concrete columns, structural walls, beam-column joints, and slab-column moment frames. A summary and discussion of the proposed supplement revisions is presented.

The ASCE/SEI Standards Committee on Seismic Rehabilitation is pleased to announce the completion of the new standard, ASCE/SEI 41-06, Seismic Rehabilitation of Existing Buildings. This new national consensus standard represents state-of-the-art knowledge in earthquake engineering and is a valuable tool for the structural engineering profession to improve building performance in future earthquakes. The ASCE/SEI 41-06 standard is the latest generation of a performance-based seismic rehabilitation methodology that began with the ATC-33 project in the early 1990's and was published as FEMA 273. ASCE/SEI 41-06 was developed from the FEMA 356, Prestandard and Commentary for the Seismic Rehabilitation of Buildings, which was based on FEMA 273, and published in 2000 as a starting point for the formal standard development process. While the FEMA 356 prestandard was a valuable document and represented a significant milestone in earthquake engineering, it is quickly becoming obsolete. The evolution from prestandard to standard took place in the form of extensive committee review, discussion, and revisions conducted in accordance with the ASCE Rules for Standards Committees, which have been approved by the American National Standards Institute. The performance-based design philosophy has been maintained, but many significant improvements have been made by the committee to reflect current understanding of building behavior in earthquakes. A few such improvements found in ASCE/SEI 41-06 include: 1 Improved C-coefficients for calculation of the pseudo-lateral force and target displacement based on recommendations in FEMA 440. 2 Comprehensive soil-structure interaction provisions including kinematic effects and foundation damping effects. 3 Revised acceptance criteria for steel moment frames to reflect final conclusions of the SAC Joint Venture research. 4 Expanded acceptance criteria for concentrically braced frames defined as a function of brace slenderness, compactness and level of connection detailing. 5 Updated nonstructural provisions to be consistent with current NEHRP Provisions for new buildings.

This paper concerns a unique failure during the 1999 Kocaeli, Turkey earthquake. With an unusually large rectangular duct opening located about 1/3 of the height above the base, a 115 meter high reinforced concrete chimney collapsed during the earthquake while several other similar structures survived with only moderate damage. This case study provides interesting results, considering that the stack was designed and constructed according to international standards and is representative of similar structures at refineries throughout the world. The main focus of the study is the dynamic response of the stack due to an earthquake motion recorded at a nearby site, named the YPT record. A new 3-D pushover analysis procedure is proposed in this paper and the results will be compared with those of a nonlinear dynamic analysis. Higher mode effects are also considered in the proposed 3-D pushover analysis procedure. Results are presented that show the importance of the 3-D interaction effects in the dynamic response of the stack. The results also confirm that the stack could readily fail under the considered earthquake and are consistent with the debris pattern.

The current boom in the region's construction industry has created a need for more efficient and cost effective methods of construction that could be used in a variety of different projects. Also, concrete is the most widely used construction material here in the UAE and is used in virtually all projects regardless of the nature of size of the project. However, there are different ways of producing and using concrete when it comes to the construction of a multi-storey building. The most common method used is known as in-situ concrete construction and involves the casting and curing of the concrete on-site. The concrete is poured into forms where it is cured and allowed to harden before the forms are removed and used elsewhere. The alternative method being evaluated is known as precast concrete construction. Pre-cast concrete is manufactured in a plant and is later transported to the jobsite where it is installed. While pre-cast concrete is a relatively new concept here in the UAE that is not applicable to many types of construction, it has still managed to replace more conventional methods in several projects. The scope of paper includes comparison of two buildings constructed in UAE; one using in-situ and the second using pre-cast concrete. It will focus on the evaluation of the two forms of construction and ultimately, which construction method would we recommend at the end of the day. The major categories which are utilized for the final recommendation on are the following: 1 Budget (Cost) 2 Work Schedule (Time) The fine details of how this is done and what tools were used during the different evaluation processes are included later on in the report. For now, it will suffice to say that an extensive Bill of Materials (BOM) was generated for each construction project; this is done through an exhaustive process of quantity surveying. This BOM is used in order to find out the cost of the project as well as how long it would take to complete the entire project. Also, specialized computer software is used in order to calculate the durability of both types of concrete and provide us with an estimate of maintenance costs for the entire life span of the project.

This study investigates the effect of amplitude-dependence on the dynamic properties of a 865 ft (264 m) tall residential building. The amplitude-dependent features of this building are investigated using a time domain approach and are compared to existing models in the literature. In particular, this study highlights the impact of amplitude-dependent frequency on damping estimates by traditional spectral methods.

This study examines the dynamic properties extracted from a suite of reinforced concrete buildings in South Korea, with emphasis on the performance of system identification approaches applied to short duration ambient records. The resulting extracted properties are then analyzed to identify trends relating damping and frequency to parameters characterizing the structural system and building geometry to highlight underlying behaviors and establish predictive tools suitable for use in the design stage. Comparisons between finite element models and in-situ values are provided in select cases to demonstrate challenges associated with modeling reinforced concrete structures.

The paper describes observations and lessons learned from more than six months on the ground in Mississippi after Hurricane Katrina, with special emphasis on the performance of heritage structures. Field assessment, damage types, stabilization and lessons learned will be discussed. On August 29, 2005, Hurricane Katrina made landfall near the Louisiana/Mississippi border as a Category 4 hurricane. In the coastal region of Mississippi, the hurricane produced the largest and most extensive storm surge ever recorded in the United States, reaching a height in excess of 30-feet at the Bay of St. Louis. In coastal Mississippi, this storm was about structural damage to buildings in vast numbers, to a greater extent than any previous natural disaster in the U.S. The closest analogue in damage severity in the United States was the Galveston Storm of 1900 in which most of that city was destroyed. The physical forces and their results were in most ways identical to those of coastal Mississippi. Katrina surge created a zone of destruction across the entire coastline of Mississippi where the physical damage was extreme, having more in common with earthquake or blast damage than with most hurricanes in modern memory. The result was the complete destruction of tens of thousands of homes and hundreds of commercial buildings. The conditions are almost impossible to communicate in words or with a few photos.

During the period of the Ottoman Empire, there have been built a numerous mosques in the Balkan area. Skopje (the capital city of Macedonia, and part of the Balkan region), is one of the many cities that prove the `mosque architecture development' during the Ottoman Empire. Since the XV century, there have been built a numerous mosques in the city of Skopje, while today only a part of them have preserved their structural integrity. However, the mosques that are present today, in the Skopje area, are evaluated with partial damages that need repairing, and in some cases reconstruction as well, in order to ensure their existence and proper functioning in the future. In this paper is shown the architecture of the `Mehmed Kebir Çelebi' mosque before and after rehabilitation, its damage characteristics evident before repairing of the mosque and the structural modification during its repair and reconstruction. In this paper is also described the structural analysis and process of rehabilitation and reconstruction of the `Mehmed Kebir Çelebi' mosque. Preceding to this issue, it is briefly presented the `3D finite element based' analysis results of the mosque with application of SAP 2000 computer software. A comparison between the two different states of the mosque (before and after rehabilitation) considering the structural modelling, points out the level of analysis and design accuracy of the mosque structure as well as its proper rehabilitation process.

The four-story South Building at Case Western Reserve University (CWRU), a prominent school located in the eastern suburbs of Cleveland, Ohio, sits on a 67,760 m² (14 acre) site that contained approximately a dozen buildings. The entire site comprised the former Mount Sinai Hospital before CWRU purchased the property in the early 1990s for expansion of the campus offices and laboratories. The South Building was originally built in 1914 as a collection of wings that jutted out from a central stem running in the east/west direction. After an extensive feasibility study of all the buildings on the property, the easternmost wing of the South Building was identified for rehabilitation, while the remaining portions of the building were to be demolished. This portion of the building was selected to remain largely because of the classic architecture of its east façade and for its existing floor live load capacities.

In this paper the maximum load carrying capacity of masonry arch bridges are assessed. Particularly, stone bridges under investigation have a perfect semicircular geometry and no binding material is used between voussoirs. Analytical methods adopted in this study are the method of virtual work and the mechanism method. In both cases the maximum concentrated load that the bridge can withstand is obtained. Drawing thrust lines for stone arches has a key role in the methods used. Additionally the concept of geometrical factor of safety is also addressed. As a case study, the first century A.D. Roman arch bridge; namely the Titus Tunnel Bridge, is investigated using the methods developed.

A team of professionals, including structural engineers, were retained to renovate Concourse B at the Memphis International Airport for a new retail configuration. The reconfiguration work required the removal of four existing interior columns, and the replacement of an 80 foot by 80 foot portion of the roof for a new glass skylight. The airport authority requested that the reconfiguration program include upgrades to the entire structure to meet current seismic design criteria. This report attempts to compare the SBC 1999 Building Code to the IBC 2000 building code, and summarize the seismic upgrade strategy chosen for this project.

This paper describes the seismic retrofit of the Huntington Beach City Hall Administration Building located in Huntington Beach, California. The existing 6-story 71,000 square foot structure was constructed circa 1971 and is located in close proximity to the Newport-Inglewood fault. The lateral system for the building consists of a non-ductile reinforced concrete beam-column moment frame system in each of the principal building directions with concrete shear walls at the stairwells. The building is supported on a pile foundation system. A preliminary evaluation of the building revealed several seismic deficiencies, including the following: (1) non-ductile detailing, such as strong beam-weak column configurations and lack of column and beam confinement reinforcement, (2) flexible lateral system with excessive building deflections, (3) inadequate shear capacity of the beam-column joints, and inadequate strength of the shear walls at the stairwells. In addition to addressing the structural seismic deficiencies of the existing building, the City of Huntington Beach required that a seismic retrofit solution be developed that is: (1) aesthetically acceptable, since it is a large building occupied by city staff and frequently visited by the public, (2) non-intrusive, (3) minimizes interior construction work, and (4) allows open views for the building occupants. After considering several alternate retrofit schemes, which included adding exterior and/or interior concrete shear walls and exterior conventional steel braced-frames, two hi-tech seismic retrofit solutions were proposed: (1) Addition of exterior buckling restrained steel braced frames and (2) Addition of viscous dampers in exterior conventional steel braced frames. The intent of both solutions is to reduce the deformation demands on the existing non-ductile concrete frames to below acceptable levels; however, the two proposed retrofit solutions accomplish this from two different approaches. The solution utilizing the buckling restrained braces provides added stiffness to the building, whereas, the viscous damper solution provides added damping to the building. In both cases, the new buckling restrained braces or viscous dampers were incorporated into a new concrete beam-column frame connected to one-bay at the exterior of the building on all four sides of the building.

The 55 East Monroe Building is a forty story high rise within the central business district of Chicago with office space over a nine level internal parking structure. The building was a significant leap in concrete technology with 9,000 psi concrete for columns and walls with lightweight concrete floor slabs. The 9,000 psi concrete was some of the first produced for high rise buildings. The garage level slabs and the entry ramps were also constructed from a 5,000 psi light-weight concrete. A parking garage at the base of the 55 East Monroe Building is integral with the main structural frame, and column grid for the upper office floors is the same for the parking areas. The building's lower parking slabs were constructed in winter 1969–1970. These parking slabs are connected to the main entry and exit by way of a two helical ramps. The ramps were designed to support a single lane of traffic, one up and one down.

Performance-based earthquake engineering was utilized to ascertain the seismic performance of a group of hospital buildings located in the regions of high seismicity in Southern California. The structures were designed and constructed in early 1970's per the applicable building codes at the time of construction. Seismic evaluation of the structures, per current version of California Building Code or FEMA's seismic evaluation procedures, indicated that buildings had severe structural deficiencies and would not survive the type of ground shaking anticipated at the sites. The design team developed an evaluation procedure and acceptance criteria for the buildings. The hospital complex consisted of a large four-story structure and two adjacent one-story buildings. Different framing systems were used to provide resistance to lateral loading for the three buildings. The four-story structure used Pre-Northridge connections and small wide flange column sections. It was supported on a one-story reinforced concrete basement. The owner initially investigated adding full-length cover plates to the majority of the columns. The retrofit cost and loss of functionality proved prohibitive. However, nonlinear response history analysis showed that when supplementary damper elements were strategically added to the building, the building response would markedly improve, and the story drifts and member flexural rotations were significantly reduced. For this structure, three performance objectives were developed. They included limiting: story drifts, steel member plastic rotations, and the lateral displacement of the first floor. One of the single story structures had masonry walls placed asymmetrically along the perimeter and showed large torsional response. The torsional response and story drifts were controlled by adding stiffness elements along the perimeter. The rehabilitated structures would meet the current seismic codes.

In Taiwan, un-reinforced masonry (URM) was a common type of construction for low-rise buildings due to their low cost and ease of construction. At 1970s and 1980s, an improved type known as "confined masonry" became the mainstream. Confined masonry consists of pre-laid URM brick walls and post-constructed reinforced concrete (RC) boundary beams and columns. It is believed that the RC boundary elements provide confinement to the walls because of shrinkage of concrete. Usually the URM walls in confined masonry are 1-brick thick (24cm), but a confined masonry building is not allowed to exceed 3 stories or 10m high by the Taiwan Building Code. So after 1990s, URM walls are mostly used as pot-laid partition walls for RC buildings. However, there are still many existing confined masonry buildings, include residence, school, and public buildings in Taiwan. Former researches have confirmed the in-plane seismic capacity of URM walls. But in typical school and street side buildings that only have walls in one direction, the out-of-plane direction of the walls becomes the weak direction and the walls fail in their out-of-plane direction before the in-plane strength can fully contributed. Therefore this paper presents an experimental investigation and an analytical approach for out-of-plane behavior and strength of URM walls in-filled in RC buildings subjected to lateral force. The experimental data comes from 2 in-site push over tests of typical school buildings by National Center for Research on Earthquake Engineering.

This paper documents the design and construction of a voluntary seismic upgrade for a four-story, nonductile concrete flat slab structure. The structure was designed in the early 1970s and lacked detailing necessary to ensure ductile behavior — both in the lightly reinforced concrete columns and in the flat post-tensioned concrete slabs. Since the structure is a modernist landmark and is located in the historic Fisherman's Wharf area of San Francisco, any strengthening had to have minimal impact on the historic fabric of the structure. After examining a number of possible options, addition of column capitals and fiber-wrapping of the non-ductile columns were selected as the upgrade that best suited the project. The new column capitals use a relatively unusual design that relies on shear-friction between the capital and the column — rather than typical epoxy-dowels — and this method of construction is described in detail. The intent of the upgrade was to satisfy prescriptive requirements as well as desired performance goals.

As the AEC industry strives to establish integrated knowledge exchange protocols utilizing building information models (BIMs), structural engineering practices of all sizes will profit from the ability to effectively communicate with the design team supported by a strongly integrated structural design process. At Thornton Tomasetti, custom tools are developed to automate the exchange of structural design data between 2D and 3D analysis models and BIMs. These tools are unique because they allow the engineer to manage partial models and data sets as independent sub-systems of complete virtual models. These sub-systems are often described in plan or elevation, while their counter parts reside in the 3D setting of the overall BIM. Custom automation of processes at Thornton Tomasetti helps to meet deadlines, exceed expectations of clients, and increases the quality of the work product. We cite three examples illustrating custom usage of application programming interfaces (APIs) and address typical challenges met when pursuing in-house development projects. The case studies include the utilization of conventional CAD documents as basic structural information models (SIMs), the automatic assembly of structural elements of complete towers in a BIM, and efficient bent management assisting the design process of stadium-like structures.

Historical aspects of the Massachusetts State Building Code make the Boston Area particularly appropriate for this discussion of strength versus ductility. Since the 1970's, engineers, seismologists and public officials have worked to prepare Boston and other cities in Massachusetts for a destructive seismic event similar to the 1755 Cape Ann Earthquake. The success of these previous efforts, drawing heavily from the Seismic Design Decision Analysis project at MIT, is evidenced both in the creation and adoption of the "first seismic criteria developed specifically for a jurisdiction in the eastern Unites States" and in the Hazus Pilot Study conducted for Boston in the late 1990's. Luft and Simpson summarized the philosophical conclusions of this work as follows. The primary finding of these studies was that the probable maximum earthquake intensities for Massachusetts are as large as those for Zone 3 regions in California, but have much longer return periods. Because of the long return periods for destructive earthquakes, it was found that the cost to society of the earthquake-resistant design is considerably greater than the projected savings in damage and loss of life due to an earthquake. Nevertheless, the committee felt that society would insist on reasonable measures to mitigate the number of casualties from a major seismic event. It was therefore considered necessary to develop a set of criteria which would minimize the projected loss of life resulting from such an event, without causing construction costs to increase by an unacceptable amount. These conclusions distinguished seismic design philosophy for Massachusetts from the contemporary SEAOC provisions for California by placing exclusive emphasis on protection against loss of life in an extreme event, and ignoring the need to minimize the cost of damage in minor and moderate earthquakes.

Current building codes require nonlinear dynamic analyses to design most base-isolated structures. This necessitates extensively detailed and well-defined structural models that require heavy computational effort. Unfortunately, many decisions regarding the building's lateral force resisting system are made during the early stages of design, when much of the structure is not fully, well-defined. The benefits of base-isolation may not be as apparent if practicing engineers are not able to effectively approximate the building's performance based on limited knowledge of its final design. Even under circumstances where the structural engineers have enough information to construct elaborate analytical models, most engineering firms reserve the time and the financial resources needed to create such models for the latter stages of design and not for proposing design alternatives that may never be implemented. Furthermore, there are different types of isolation bearing systems currently available that can perform very differently from one another. Decisions regarding the type of bearings are also usually made during preliminary design are require substantial resources and computational effort to make a comparison that would yield the best isolation alternative. A simplified method of analysis that provides reasonably accurate results, based on limited knowledge of the structure, would facilitate these types of decisions during preliminary design. The 1997 Uniform Building Code currently provides a statically equivalent method of analysis that is often used for preliminary design; however, this procedure is very limited and has many shortcomings. The static procedure does not capture the dynamic effects of structural response when subjected to seismic ground motions. It oversimplifies the response of the superstructure (the structural system above the isolators) by assuming a simplified and often unrealistic lateral force distribution. The analysis only considers the first mode response and ignores higher mode effects that contribute to acceleration demands. There is no procedure for estimating acceleration demands. The intrinsic nonlinear behavior of isolators is poorly approximated by using equivalent linear procedures. For these and other reasons, isolation experts often consider the 1997 UBC procedure overly complicated and conservative. Miranda, Miranda and Reyes, and Miranda and Taghavi have shown that a simplified method of analysis, using a continuum model that approximates the dynamic characteristics of buildings, can predict reasonably accurate displacement, drift and acceleration demands on a multistory building when subjected to seismic ground motions. The continuous model is very useful in preliminary design because it only requires a three or four structural parameters that are typically known or can be estimated during the early stages of design. The objective of this paper is to present a simplified method of analyzing base-isolated multistory buildings for preliminary design. The procedure uses the continuous model's dynamic properties to approximate a structure's response parameters when experiencing earthquake excitation. The procedure also attempts to improve estimating the inherent nonlinear behavior of isolator bearings by deriving a nonlinear element that is based on Menegotto and Pinto's hysteretic model. The method's accuracy is assessed by comparing the results of the approximate method, to those produced by using the dynamic properties of two example structures, which have been calculated by more rigorous analytical techniques and documented in previous research literature.

The lateral design force distribution given by the IBC equivalent lateral force method for base-isolated buildings is often regarded as very conservative. These provisions neglect the inertia at the base mass entirely, and apply the same triangular force distribution as for a short period fixed-base building, even though the first mode shape of an isolated building is closer to uniform than linear. However, the nonlinearity of the isolation system, which can induce a higher mode response, is often overlooked. Using nonlinear regression analysis of median response data from nonlinear response history analysis of representative systems, improved equations are developed to estimate the seismic force at the base level and the distribution of lateral loads in the superstructure. The IBC distribution and the improved distribution developed here are evaluated in comparison to seismic response data. While the IBC distribution is conservative for many systems, the improved equations are accurate over a wide range of system parameters.

The seismic design provisions for structural components of the lateral force resisting system have undergone changes in recent years to progress towards performance-based design. Current seismic design provisions for structural components take into account nonlinear behavior and displacement capacity instead of an allowable stress and displacement methodology. During this time, changes in the seismic design provisions for nonstructural components have focused primarily on the magnitude of applied forces and have not explicitly considered the behavior of the nonstructural components or their attachments. Because of the diversity of types and configurations of nonstructural components, it has been difficult to develop a set of guidelines for seismic design of nonstructural components that can be applied to all types of nonstructural components and their various means of attachment. There are however, some configurations of nonstructural component anchorage and bracing whose seismic behavior can be considered similar to that of building structural systems. Where this behavior can be identified, seismic design methodologies for structural component bracing and anchorage can employ similar methodologies as applied to structural systems. Changes are proposed for the seismic design of nonstructural components that incorporate design concepts that are currently used for the design of structural components, such as capacity design and ductile detailing. Examples are provided to demonstrate how the use of these structural design concepts can improve the expected performance of nonstructural components subjected to earthquake forces.

This paper details the role that a building code recognized shake table test protocol for nonstructural building components serves to insure clarity for both the manufacturer and design professional to simplify compliance. Without a building code recognized test protocol it will be shown that qualification testing is inconsistent, at best, leading to confusion for verification of specification compliance. Also discussed will be the importance of seismic anchorage and the implementation of an ongoing mitigation program for the life of the facility.

Special fire sprinkler system installation guidance intended to guard against damage due to earthquakes first appeared in the North American sprinkler installation standard in 1947, and was largely based on experience in the Long Beach earthquake of 1930. At that time many building codes in use in the United States did not even address the subject of earthquakes. Insurance reports of the Long Beach earthquake had indicated 90 damaged sprinkler systems. The first guidance, contained only in the appendix, called for 1 to 2 inches clearance around pipes, flexible couplings in risers and "some form of lateral and longitudinal bracing" for feed and cross mains. In the 1951 edition requirements were placed in the body of the standard for placement of longitudinal and lateral braces with spacing indicated as "30 to 40 ft", a maximum slenderness ratio of brace members of 200, and flexible couplings on risers where it was necessary to protect systems against earthquakes. The stated intent was to laterally brace for 50% of weight of water-filled piping and attachments. In the decades since then deliberate efforts have been made to clarify the rules and improve protection within the text of NFPA 13 — Installation of Sprinkler Systems, but always with the intent of addressing "how" systems are to be protected against earthquakes, not "where" such protection is to be provided. It was recognized that building codes and other authorities made the basic decisions with regard to the location of earthquake-prone areas. Although the earliest guidance contained in NFPA 13 came from the insurance industry in the western states, the NFPA Committee on Automatic Sprinklers formed an Earthquake Protection Subcommittee in 1985. One of the goals of this subcommittee was to develop a means to address the bracing of sprinkler systems in the same manner that the application of system hydraulics had been accomplished. Although a complex subject, it was believed that many of the design aspects could be pre-engineered into tables and then properly applied by the technicians who normally lay out and detail fire sprinkler systems. The 1983 standard contained no information on the sizing or fastening of bracing relative to loads. A method was proposed in 1984 whereby "zones of influence" could be evaluated to determine total loads for proposed brace locations. Tables were proposed for determining maximum brace loads and allowable fastener loads based on six different combinations of brace and fastener orientation and angle from vertical. This concept and the accompanying tables were accepted into the appendix of the standard in the 1987 edition, and in the 1989 edition the tables were expanded to nine combinations of orientation and angle and moved into the body of the standard.

Many ports in the Pacific are experiencing significant growth as a result of increased business trade. In these areas of the world, container wharves need to be designed for a combination of gravity loads and seismic loading. The connection between the pile and the wharf is critical as large ductility requirements may be relied upon these connections. This paper discusses the results of an experimental program funded by the Port of Los Angeles (POLA) to improve and enhance the performance of pile-deck connections that will satisfy the requirements of the new Performance based Seismic Design Code for Container Wharves issued by the port. Two full-scale units, representing typical seismic and nonseismic pile-deck connections were tested under reversed cyclic loading. The tests units showed lateral displacement reserves significantly greater than those that corresponded to the structural strain-limits in the new Seismic Design Code for the Port of Los Angeles.

The American Petroleum Institute (API) Standard 650 "Welded Steel Tanks for Oil Storage" has become a leading specification for the design of field erected aboveground storage tanks (AST) worldwide. Tanks designed and erected under this standard store a wide variety of products. These include crude and refined petroleum products (gasoline, fuel oils, and asphalt), chemicals (fertilizers, pesticides, solvents and sulfuric acid), animal fats and oils (used in cosmetics and soaps), vegetable oils (used in food products), molasses and alcohols. The proper design and detailing of large field erected AST's is not only important from the potential environmental and safety impact in the event of a failure, but becomes a serious issue for our public security as many of these tanks constitute a vital link in our critical infrastructure. Appendix E of API Standard 650 deals with the seismic design of storage tanks. The latest revision to the standard, released in early 2006, is Addendum 4 of the 10th Edition. This was an extensive revision of Appendix E which incorporated new definitions, more open and expanded equations, as well as analytical methodologies and ground motion requirements that are consistent with ASCE 7-02 "Minimum Design Loads for Buildings and Other Structures". The revision also provides new detailing recommendations for serviceability limits for items such as pipe flexibility and freeboard. This paper will briefly review the applicability of the API 650 Standard, summarize the specific Addendum 4 changes to Appendix E, and provide a complete seismic design example based on the new provisions.

A set of engineering standards has been completed for the design and maintenance of marine oil terminals. These "Marine Oil Terminal Engineering and Maintenance Standards (MOTEMS) became regulatory in February 2006. The Standards were developed by the Marine Facilities Division of the California State Lands Commission and include criteria for above and under water inspection, structural (and seismic) rehabilitation, as well as new design, fire, piping, mechanical and electrical systems. These standards address both new terminals or new components as well as existing facilities.

Designers and owners are frequently confronted with situations where multiple codes might be used for the same application. This is especially prevalent on international projects, where local codes may differ significantly from a company's own standards. This also occurs when international vendors request exceptions to project specific criteria in order to use design codes that are more familiar to that particular vendor or design codes that are embedded into design software. This paper intends to provide guidance for situations such as those described above, where the design engineer may be required to understand and evaluate multiple seismic design criteria or codes. This paper is not intended to provide step-by-step guidance for the application of various international seismic design codes.

Codes and standards have generally provided conservative guidelines for design of tall reinforced concrete chimneys because of their inherent brittle nature and low redundancy. This paper reviews the state-of-the-practice for seismic design of concrete chimneys. The codes and standards reviewed in this paper are the American Concrete Institute's Committee for Design and Construction of Reinforced Concrete Chimneys, the International Committee on Industrial Chimneys, Eurocode 8-6, International Conference of Building Officials and the International Building Code. The paper discusses the provisions presented in the above codes and standards and compares them from the point of view of design philosophies, expected chimney behavior, required detailing, economy of design and design rationality. Based on this review, some concluding remarks are presented for design of RC chimneys in the United States.

This paper provides an overview of remediation techniques currently in use to improve liquefiable soils. An overview of liquefaction and hazard reduction methods is presented including methods of implementation, suitability, and practical considerations. Techniques include soil replacement, vibro-compaction, vibro-replacement, dynamic compaction, explosive compaction, and site drainage enhancement.

A new definition of dynamic participation factor is proposed for analysis and design of structures supporting rotating machines. Compared with the traditional dynamic participation factors, the new dynamic participation factors can indicate accurately the contribution of each mode under the machine excitation, and thus identify the possible resonant local modes. An example of a table-top foundation of a steam turbine generator is presented and the results are compared with the result from harmonic analysis (frequency sweep).

Earthquakes pose a considerable threat to lifeline systems in regions of high or moderate seismicity, such as Charleston, SC. In particular, in areas such as Charleston, where the last significant earthquake occurred over 120 years ago, most of the existing transportation facilities were designed with little to no seismic consideration. However, a growing public awareness of the seismic threat has motivated an assessment of the potential risk to the transportation network to support decision-making on mitigation strategies and emergency planning and preparedness efforts, such as emergency route (lifeline) selection. This paper presents the findings of the first phase of the project, which applies the seismic risk assessment framework with state-of-the-art tools and relevant data specific to the region of interest. This includes an inventory analysis of the roughly 340 bridges in Charleston County, and convolution of the seismic hazard with fragility curves analytically derived for classes of bridges common to this part of the country, and bridge damage-functionality relationships using region-specific data. The study includes assessment and comparison of the distribution of bridge damage for a number of different hazard levels or scenario events. The potential bridge functionality is also presented to aid in identification of emergency routes. The results provide insight for decision-makers as to the potential seismic risk to the transportation network in Charleston, and identification of emergency routes or regions in need of strengthening.

This paper provides a summary of the challenges and lessons learned during the design and construction phases of the seismic retrofit of the North Queen Anne Drive Bridge, which is located just north of downtown Seattle, Washington. Some of these challenges included difficult site access, environmental concerns, minimizing the visual impact of the retrofit, as well as modifying an existing structure with limited as-built information. The lessons learned during this project may offer valuable insight for projects elsewhere with similar constraints. The North Queen Anne Drive Bridge, an historic steel structure built in 1935, is owned and maintained by the City of Seattle Department of Transportation (SDOT). It is comprised of seven spans, the main span of which is a 140-foot long three-pin steel arch (Figure 1). The six approach spans consist of steel girders and stringers supported by steel columns cross-braced in the transverse direction. This 327-foot long bridge crosses a steep ravine, at the base of which is a wetland. The structure is 45-feet wide with a 2000-foot horizontal curve.

Large rectangular box Caissons are used occasionally to support bridge superstructures. This paper presents a simplified method for evaluating the seismic performance of caissons. A theoretical approach was developed, using basic principles of structural mechanics and the half-space theory, to determine the deformation capacity curve. The capacity spectrum approach was used to evaluate the performance for a specific seismic event. This simple method compared favorably to finite element (FE) methods.

This paper presents a study of skewness effect on live load reactions at piers of continuous prestressed concrete bridges. Two prestressed concrete bridges were selected for the study, one bridge with two-span and the other with four-span. To study the effect of skewness, the skew angles of the bridges were varied from 0° to 60°. Finite element modeling and analysis were performed on the selected bridges. The comparison for live load reaction and shear revealed that the distribution factor of reaction at piers was higher than that of shear at beam ends near the same support location. The increase in reaction distribution factor was more significant than that in shear distribution factor on the interior beam line when skew angle was greater than 30°. It is recommended that more research be performed for the distribution factor of live load reaction to quantify the responses.

This paper describes the measured behavior of a two span, live-load continuous bridge made with precast, prestressed, self-consolidated concrete girders. The lengths of each span are 27.2 m (89 ft 3 in.). The self consolidated concrete was considered high-performance, because of its high early compressive strength of 69.5 MPa (10.1 ksi) at release and 76.2 MPa (11.1 ksi) at 28 days. By using this high strength, self-consolidating concrete, the bridge designer is able to reduce the number of girder lines. These girders are among the first to be constructed in state of Utah using self-consolidating concrete. In order to monitor the behavior of the bridge, instrumentation was embedded in four of the twelve girders. Two interior girders in each span were chosen as representative girders. The instrumentation consists of vibrating wire strain gages with integral thermistors. The gages were placed at the centroid of the prestressing strands, girder centroid and composite girder centroid. Each of the gages has been monitored continuously since the time of casting. Data collected from each girder encompass the following phases: casting, de-stressing, curing, and deck placement. The measured changes in strain have been used to determine prestress loss values for each of the instrumented girders. These measured values are compared with predictive values using a newly proposed NCHRP method. The differences between the measured and predicted prestress losses are compared and recommendations for designers are provided.

China is about the size of the United States. Three major rivers, the Huanghe in the north, the Yangtze in the middle and the Pearl in the south, all flow from west to the east. Moreover, most of China is mountainous. Building any highway and railway will require many major bridges over these rivers and gorges. The modernization of China calls for seven major east-west highways and five north-south highways. Currently, China has about 1.95 million kilometers of highways and 41,000 kilometers of freeways. It is estimated that by 2010, these numbers will increase to 2.30 million and 65,000. And by 2020, China will have 3.00 million kilometers of highways and 85,000 kilometers of freeways. Undoubtedly, there will be many major bridges along these routes.

The concrete deck w/overhang structure is widely used in bridge design. The research model used in this study is a one-span concrete deck and barrier w/overhang. It is placed under a simulated static transverse load of TL-6 of the American Association of State Highway & Transportation Officials (ASHTTO) at the top of the barrier. Finite Element Method (FEM) will be used to analyze the model. This paper presents that the distribution of the transverse load from the top of barrier extends to bottom of the barrier, then from the junction of the barrier and the deck to the first support (nearby the barrier). This distribution of the load then extends to the second support (away from the barrier). The reactions on the support are dynamic. Theses vary from positive and negative according to the distance from an observed point to the center of the load. The contours of the stress distribution are used to observe and evaluate the load distribution. The stem of the barrier and the inner corner of the barrier and the deck are indicated as regions of complex stresses. The load distributed on the model does not seem to match an assumption load distribution by the conventional structural analysis method, which has 45-degree spread angle. The results of this research show that the spread angle of load distribution is greater than a 45-degree spread angle that is an assumption of the conventional design method. This phenomenon is due to the integrity of structure to the transverse load. Recommendations and conclusions are included in this paper. These will assist engineers and researchers in re-recognizing and reassessing this type of structure from a different viewpoint.

Bridge load rating involves performing a series of calculations synonymous with bridge design calculations in order to determine if a bridge is safe for public traffic loads. The AASHTO Load Factor Rating (LFR) is the currently used method in bridge load rating. The Load and Resistance Factor Fating (LRFR) is a new guide manual adopted by the American Association of State Highway and Transportation Officials (AASHTO) in 2001 for condition evaluation of highway bridges. The guide manual reflects the most current technologies and builds on the structural reliability approach inherent in specifications for Load and Resistance Factor Design (LRFD). In this paper, seven prestressed concrete bridges of moderate span length (50 – 117 ft) are analyzed and rated using the AASHTO LFR and AASHTO LRFR methods. The selected bridges include one straight simple span Bulb Tee-girder, three skewed simple span I-girder, and three skewed continuous multi-span I-girder bridges. The comparison study for the prestressed concrete I-section bridges reveals some differences between the rating results using LFR and new LRFR methodologies. The majority of load ratings achieved using the LRFR approach for the prestressed concrete bridges are governed by shear rather than flexure, which is a substantial difference from the LFR method where flexural ratings typically govern for all bridge types.

This research experimentally investigates the behavior of circular reinforced concrete columns under reversed cyclic torsion. The columns are reinforced using a new confinement technique which uses two opposing spirals (cross spirals) in order to enhance strength and ductility or to increase spiral spacing (pitch) to facilitate the passage of concrete during construction. Eighteen reduced scale R/C circular columns with four different length to depth ratios and several spiral spacings and patterns were built and tested. The columns were subjected to reversed cyclic twist to study the behavior of the new confinement technique. The torsional strength and ductility of these columns are compared to columns confined with a conventional single spiral reinforcement layout.

This paper presents the findings from a research project funded by the NCHRP — IDEA Program. This paper discusses the experimental results from the studies which involved a defect sensitivity study of an Impact-Echo (IE) Scanner to detect and image discontinuities in post-tensioned ducts of a mockup U-shaped bridge girder and a mockup slab. Different sizes of ducts were included in this study as well as varying sizes of void defects. Detailed sensitivity study of nondestructive grout defect detection with Impact-Echo Scanning of 8-four inch diameter ducts with constructed defects was the main focus in this study. Comparisons of the IE defect interpretation and the actual design conditions of the ducts inside the bridge girder/slab are presented. The IE results are presented in a three-dimensional fashion using thickness surface plots to provide improved visualization and interpretation of the internal grout to void defect conditions inside the ducts of the girder. The Impact-Echo tests were performed with a Scanner which greatly facilitates the Impact-Echo test process by allowing for rapid, near continuous testing and true "scanning" capabilities to test concrete structures. The paper summarizes the general background of the Impact-Echo technique and the Impact-Echo Scanner. Descriptions of two mock-up specimens used in the experiment and the discussion of the results from the Impact-Echo Scanner are presented herein. Finally, a case study using an Impact Echo Scanner to locate grout voids inside the Orwell Bridge in UK is included in this paper.

Prestressed and post-tensioned concrete structures are susceptible to corrosion if the tensioned steel is exposed to chlorides or a neutral pH environment. Since the mid 1970's many advancements have been made in the understanding of the corrosion protection requirements for prestressed and post-tensioned concrete structures. Simultaneously, research and application of galvanic corrosion protection systems to address corrosion in these structures has resulted in the development of galvanic systems that are available to provide a full range of corrosion protection levels without risk to the prestressing steel.

This paper focuses on the heat straightening repair and rehabilitation of steel bridge girders damaged by collision with overheight trucks. The paper presents an numerical approach for simulating the damage, and the heat straightening repair of composite steel bridge girders. This approach is used to investigate the effects of damage followed by heat straightening repair on the: (a) residual stresses, (b) serviceability, and (c) ultimate load capacity of composite steel girders and bridges. Additionally, the effects of steel material and girder geometric properties, damage magnitude and location, and heating patterns and distribution are also evaluated. The results from the numerical parametric studies provide guidelines for designing heat straightening repairs, estimating final residual stresses, and evaluating the state (performance) of damaged-repaired steel bridges. These results are based on simulation only, and need further experimental investigations and validation, which is ongoing.

This paper will describe existing bridges in service that were "Built Big" or with the largest pieces practicable. The FHWA has promoted innovative Accelerated Bridge Construction Techniques for bridges. Large Steel Orthotropic Bridges built and in operation maximize these techniques as will be clarified with case histories. Orthotropic steel decks in North America are very rare, but are successful. The landmark twin bridges of Long Beach are the Queensway Orthotropic Steel Bridges built by Murphy Pacific. The advantages of lowest mass for very large piece erection are fewer pieces plus smaller impact to others traveling beside or below bridge construction. The four basic techniques of ABC erection processes are Launching, Lifting, Heavy Moving on Multi Wheeled Trailers and Floating. 1: The largest launched bridged from around the world include the Millau Viaduct of France is described. 2: Lifted bridges selected from around the world include the Fremont bridge of Portland, Oregon, San Diego Coronado Bridge; Alfred Zampa, Crockett, CA and Tacoma Narrows Three. 3: Bridges Moved on Multi Wheeled Trailers discussed from around the world include Maritime Off-Ramp Bridge, 4: Floated bridges of discussed from around the world include the Tatara Cable Stayed Bridge, and the floating tied arch Yumemai bridge in Osaka Harbor. Innovative bridges were selected demonstrate the complete range of all types. Bridges are organized in this paper by main span type. A useful reference list is provided. ASCE's www.orthotropic-bridge.org is currently planned for August 2008 in Sacramento, CA to continue in exchanging data.

As Miami-Dade County continues its rapid growth west towards the Everglades, local transportation officials find themselves in need of significant capacity improvements to accommodate the increase in vehicular traffic. To address this need, the Miami-Dade Expressway Authority (MDX) has embarked on an expressway expansion program that consists of three design-build contracts. The goal of the expansion program is improved service and heightened aesthetics. This project is the first of the three design-build contracts, is approximately 2.6 miles long and includes the SR 836 Flyover bridges. Within the project limits there are four bridge sites and several innovative sign structures. Three of the bridges in the project are completely new structures employing aesthetic features such as concrete formliners for piers and retaining walls, smooth and flowing structural lines, unusual color schemes, and inlaid tile. The two largest and most innovative bridges in the project. Bridge Nos. 11 and 12, consist of long-span steel box girder superstructures with post-tensioned integral concrete diaphragms, aesthetically enhanced piers founded on spread footing foundations, and spread footing abutments. Prime contractor Condotte America, Inc. teamed with HNTB Corporation for this design-build project. By electing to utilize innovative construction methods and structural elements, the project team won the project with a final bid of $36 million, a construction schedule of 775 days, and a score of 83 on the technical proposal. Four months into the contract, the Owner elected to add a lane to the eastern portion of the project, which increased the contract value to $39 million and added 122 days to the schedule.

The Marquette Interchange, located in the midst of Downtown Milwaukee, has become the cornerstone of Southeastern Wisconsin's freeway system. IH-94, IH-794 and IH-43 converge to form a vital link in the state's economy and transportation system. Over 300,000 vehicles pass through the interchange daily. In an effort to keep as much of the interchange open during construction, a complex construction staging and traffic control plan is being successfully implemented. This complex staging, as well as the overall complex geometry of the system, required the designers to implement many innovative solutions. Originally opened to traffic on December 23, 1968, the interchange is currently being completely reconstructed and reconfigured to replace the deteriorated and obsolete interchange. Construction began in early 2005 and is on schedule for completion in December of 2008. The five-level interchange and legs in each direction are shaped by the numerous bridges and retaining walls. Accordingly, given the urban setting, an extensive Community Sensitive Design process was incorporated into the project design. The structure shapes and features reflect themes drawn from the surrounding community. Ultimately, the 8 high level curved system ramps will become the focal point of the interchange as they become a permanent fixture in the Milwaukee skyline.

Four steel bridges in Texas have been designed and will be constructed using lean-on bracing systems where individual cross-frames provide bracing to multiple girders. The detailing used in these bridges includes top and bottom lateral struts in girder bays adjacent to a cross-frame to allow several girders to lean on the cross-frame. Utilization of lean-on concepts should reduce fabrication costs since there will be fewer bracing members that need to be constructed, and also provide maintenance benefits over the life of the bridges since there will be fewer cross-frames to inspect. However, the most significant benefit from use of lean-on cross-frame concepts in bridges with skewed supports is that the bracing system can be laid out such that the cross-frames will pick up smaller forces under truck traffic in the completed bridge, than those that would occur with a conventional cross-frame layout. The bridge systems in which the lean-on bracing system is being implemented in Texas include three severely skewed bridges and one bridge with normal supports. This paper provides details of the specific system implemented in one of the skewed bridges.

In this study, the static response and dynamic modal properties of a cable-stayed bridge with a main span of 1088m under strong winds are addressed focusing on the effect of cable vibration on overall bridge behavior. Two modeling systems for stay cables are considered in the finite element modeling of the overall bridge, i.e., one element cable system (OECS) and multiple element cable system (MECS). The aerostatic analysis under varying wind speeds and angles of attack is conducted with an iterative procedure taking into account the nonlinearities of wind forces and cables. The modal analysis is then performed under the statically deformed conditions to quantify the changes in bridge modal properties with increasing wind speed. The analysis results are further compared with the measurements using a full aeroelastic bridge model in a wind tunnel. The results of this study revealed the importance of using the MECS for accurate modeling and response prediction of long span cable-stayed bridges to strong winds.

The University of Nebraska's I-girders, known as NU girders, are precast prestressed concrete girders that have unique characteristics. NU girders have a wide top flange (48.2 in) to provide a better platform for workers and shorter span for deck; and a wide and thick bottom flange (38.4 in) to accommodate a large number of prestressing strands. The depth of NU girders varies from 20.3 in. to 63.6 in. to allow the construction of bridges. that spans up to 210 ft with a high economic competency. These unique characteristics significantly affect the flexure and shear resistance of NU girders, and consequently, influence their reliability when the uncertainty of loads, material properties, and fabrication parameters are considered. This paper presents the reliability analysis of NU girders designed using the strength I limit state of the AASHTO LRFD bridge design specifications. Resistance models are developed for several types of NU girders (NU1600, NU1800, and NU2000) and considering different combinations of girder span (120 to 200 ft) and girder spacing (8 to 12 ft). The variability of flexure and shear resistance is calculated based on the uncertainty of: i) material properties, such as cast-in-place concrete strength, precast concrete initial and final strength, reinforcing steel yield strength, and prestressing strands ultimate strength; and ii) fabrication parameters, such as the dimensions of concrete sections, area of reinforcing steel, and area of prestressing strands. Load models are developed to account for the uncertainty in dead load, wearing surface load, live load, and impact load. The calculated reliability indices are examined for consistency and compared against the target reliability index for various combinations of girder type, span, and spacing.

In December, 2000, the Rollins Road Bridge in Rollinsford, New Hampshire was opened to traffic. The Rollins Road Bridge was constructed with funding from the Innovative Bridge Research and Construction (IBRC) program administered by the Federal Highway Administration (FHWA). A requirement of the IBRC program is the use of high performance and innovative materials. The deck of the ,Rollins Road Bridge is high-performance concrete (HPC) reinforced with carbon fiber reinforced polymers (CFRP). These materials were selected to create a durable concrete superstructure that is free of metallic reinforcement. Also as part the IBRC program, Rollins Road Bridge was instrumented with a series of strain and temperature sensors to monitor and study the structural behavior of the bridge deck. This paper describes a program of structural health monitoring for the Rollins Road Bridge, the first bridge in the United States to contain high performance concrete (HPC) and state-of-the-art carbon fiber reinforced polymeric (CFRP) grids). Over 80 fiber optic sensors, measuring strain and temperature, were installed in the bridge during construction, including both the CFRP and concrete material in the deck and the concrete girders. Strain distributions collected from these fiber optic sensors shows that the maximum strains in the actual bridge were less than 100 micro strains, while deflections of the girders and deck were less than 0.1 in (2.5 mm) under a sustained truck load within the first two years of service in 2002. This paper focuses on the potential use of the collected data, from both strain and temperature sensors to conduct in-service performance monitoring. The recent data will be compared with the baseline data collected in 2002.

The University Of Connecticut and the Division of Research in the Connecticut Department of Transportation have been involved in monitoring both steel and concrete bridges during the past two decades. This paper will report on the operation of permanent monitoring systems on four different bridges in the State of Connecticut during the past decade. The monitoring systems have been tailored to each bridge, using sensors for strain, temperature, tilt and vibration. Monitoring is conducted on a continuous basis, with excitation provided by normal traffic loading. The bridges are monitored remotely from the University of Connecticut and the Connecticut Department of Transportation. The extensive data has been used to characterize the performance of each bridge and to provide information for long-term structural health monitoring. This has required significant data management, based on what has been learned in previous research at the University of Connecticut.

Structural Composite Lumber (SCL) was designed to achieve maximum strength, stiffness and efficient use of wood. Product variations of SCL are currently being used in transportation sector, especially for rural and other low traffic volume roads. Commercially available pre-built SCL bridge girders are gaining increased popularity. As these girders are repeatedly subjected to numerous cycles of wheel loads, their fatigue behavior becomes a serious concern. The current study tests 12 newly procured, 20 ft long SCL T-beam bridge girders for flexural fatigue under a stress controlled test setup. AASHTO LRFD loading was applied on the girders. The number of load application cycles was consistent with expected traffic volume for a sixty year time span. Transverse post-tension was applied to the girders to simulate the stress laminated deck effect as in an in-service girder. Results from the study indicate that the SCL T-beam bridge girders are capable of withstanding the repetitive loads. Most of the beams did not suffer any severe physical damage. Some girders experienced cracking and separation at the SCL-epoxy interface. The girders without any significant damage due to fatigue were loaded statically up to failure. The residual strengths of the fatigued girders were compared to the ultimate flexural strengths of fresh beams of similar material type.

Wood preservatives are required by AASHTO specifications in bridge applications to extend the service life of the wood members. The only exception is for naturally durable species, which are significantly more expensive. While the majority of wood used in bridge applications is treated with oil-type preservatives, wood treated with waterborne preservatives has been used in timber bridge applications. Many design engineers are choosing waterborne preservatives due to oil-type exudation concerns. As of January, 2004, the most common waterborne preservative of the past thirty years, Chromated Copper Arsenate (CCA), was voluntarily withdrawn from use in residential applications. While this withdrawal does not directly affect bridge applications, some designers are choosing to use alternative treatments to CCA, such as Alkaline Copper Quaternary (ACQ), Copper Azole (CuAz). It is believed that these preservatives are more corrosive towards metal than CCA because CCA contains hexavalent chromium and arsenic, both of which typically act as corrosion inhibitors, and are not contained in the CCA alternatives. In addition, these preservatives contain more copper than CCA, and the mechanism of corrosion of metals in contact with treated wood is believed to be related to the free copper within the wood. Unfortunately, there has been very little published research on the corrosiveness of wood treated with these preservatives because of the difficulties of measuring the corrosion rate in these environments. This work will briefly review published literature and current research activities on the corrosion of metals in contact with wood treated with waterborne alternatives to CCA. In addition, recommendations to minimize these corrosive effects in timber bridges will be discussed.

The allowable-stress design methodology that has been used for decades to design timber bridge superstructures is being replaced in the near future. Beginning in October 2007, bridge designers will be required by the Federal Highway Administration (FHWA) to utilize the Load and Resistance Factor Design (LRFD) design specifications published by the American Association of State Transportation and Highway Officials (AASHTO). Until recently, significant discrepancies existed between the two design methodologies as they pertain to the design of timber bridges. However, several modifications and improvements to the LRFD bridge design specifications were recently incorporated into the latest edition of the LRFD bridge design standards in an effort to mimic allowable-stress design techniques using current timber design standards. Timber bridge supstructures designed using the latest LRFD design requirements will still not be identical to those designed with allowable-stress design procedures, primarily due to new requirements for higher design vehicle live-loads and modified live-load distribution equations within AASHTO-LRFD design specifications. In addition, timber bridges designed using allowable-stress design methods prior to 2007 will be not be required to use AASHTO-LRFD methods for load rating purposes.

After being closed to traffic for 25 years and allowed to fall into an advanced state of deterioration, the Lowell Covered Bridge in Lane County, Oregon, has recently been renovated as a recreational/informational facility. The site is now a highway wayside, complete with off-road parking, restrooms, an espresso stand, and an ADA-compliant promenade that provides access to a beautiful lake in the foothills of the Cascade Range. Interpretive exhibits provide visitors with information about Oregon covered bridges, local recreation opportunities, and bridge-building history and technology. OBEC Consulting Engineers has been involved in the rehabilitation of many of Oregon's historic covered bridges, but this project represented a long-shot that may never have succeeded. The bridge was no longer open to traffic and therefore not eligible for highway funds, so there was no single source of funding available to repair and refurbish the structure. However, there were key people in strategic positions who recognized the value of saving this bridge and there was a spirit of cooperation among the members of the multi-disciplinary development team.

Currently, design of continuous bridges normally takes into account the dynamic restrain provided by fixed support without considering the friction force at the movable supports to simplify the design calculation. Nevertheless, the energy dissipation at movable supports can be significant in assessing the dynamic behavior of continuous bridges under certain conditions. A comprehensive study is conducted to investigate the contributing factors to friction forces at movable supports and their influence on seismic response of continuous bridges. A nonlinear 3-D Finite Element Analysis (FEA) is performed to simulate the seismic performance of a six-span box girder concrete continuous bridge. Three models are chosen to simulate the common analysis models of continuous bridges. The time-history analysis is performed based on the response spectra of three earthquakes: N-S component of the El Centro earthquake (1940), Taft earthquake (1952), and Tianjing earthquake (1976 Ninghe earthquake, Tianjing, China). Effect of parameters such as friction coefficients, pier diameter, and initial shear stiffness of supports on the seismic performance of bridges are studied. The results show that the natural period of continuous bridge could be close to the dominant period of the subsurface soil. It significantly increases the dynamic response of bridges. Based on the results of this study, seismic design recommendations for continuous bridges are proposed.

This paper investigates the bearing forces and shears for typical Illinois bridges, using both field testing and analysis. Based on a survey of the literature, as well as information presented at Illinois Department of Transportation (IDOT) seminars on Load and Resistance Factor Design (LRFD), using the LRFD Specification for bridges in Illinois can result in bearing shears of up to 40% greater than those calculated using Load Factor Design (LFD). Two factors in the LRFD Specification contribute most strongly to this increase: 1 The requirement that the lane loading be considered simultaneously with the truck loading, designated as HL-93, and 2 The effect of the revised girder shear distribution factors This paper will examine the suitability of the revised LRFD shear distribution factors. Twelve bridges along the Interstate 55 (I-55) and Interstate 270/70 (I-270/70) corridors have been selected and monitored. The candidate structures were chosen to vary as many parameters as possible. Factors such as skew angle, beam material, bearing material, beam spacing, design methodology, age, traffic factors, and environments are some of the factors that were considered when selecting the candidate structures. These structures were instrumented with strain gages and monitored for six months during two different time intervals. Data were collected and analyzed to determine if the LRFD design factors are realistic in terms of actual Illinois loading conditions.

The Federal Highway Administration (FHWA) is requesting that all states implement the American Association of State Highway and Transportation Officials (AASHTO) Load Resistance Factor Design (LRFD) specifications for bridge design beginning in 2007. The LRFD specifications is considered to be state-of-the-art and was developed to improve the reliability of bridges and increase safety of highway structures [FHWA 2004]. In the design of bridges, the LRFD specifications require an increase in bearing forces. As a result, the required shear and reaction forces in bridge girders may increase to over twice the Load Factor Design (LFD) specifications. This is caused by the HL-93 truck loading requirement along with the lane loadings to be considered together in the LRFD code, as well as an increase in the shear distribution factor for some girder spacings. The purpose of this study was to examine the live loads on Illinois Bridges. Shear forces were measured and recorded in several bridges for a duration from six to eleven months. This required the instrumentation of several strain gage rosettes on two girders for each bridge. Twelve bridges were selected to be tested; six were located along the I-55 corridor and the other six were located along the I-70 / I-270 corridor in Illinois. These bridges were chosen such that the sample of bridges included a variety of characteristics, which included number of spans, span lengths, skew angles and girder materials, steel and concrete.

Coastal bridges are exposed to severe wind and wave loads during a hurricane. Because the density of water is much larger than the density of air, the magnitude of wave loads is much larger than wind load, and can demolish the bridge superstructure if it was not specifically designed to withstand wave loads. In September 2004, the 2.5-mile-long I-10 twin bridges over Escambia Bay near Pensacola, Florida suffered extensive structural damage during Hurricane Ivan, 58 spans of the eastbound and westbound bridges were knocked off the piers and another 66 spans were misaligned. During Hurricane Katrina in August 2005, several bridges in Louisiana and Mississippi were damaged. The bridge decks were lifted by the large uplift wave load and pushed off the piers by the horizontal wave load. In this research, the uplift wave load is calculated by the velocity potential and diffraction theory with finite difference method. The analytical model is validated by laboratory measurements. The extreme sea state around the damaged I-10 Bridges during Hurricane Ivan, including the wave height, wave period and direction, is hindcasted with wave model SWAN and achieved historical wind data. The calculated wave parameters are then used to calculate the uplift wave load on the superstructure of the I-10 Bridges. The influence of wave height, wave period and water depth on uplift wave load is also investigated.

A recently completed study by Goode and van de Lindt, which developed a performance-based approach for the selection of high-mast lighting structural supports, demonstrated numerically the potential for fatigue problems on slender steel structures due to high winds when considering along-wind displacements only. The most commonly used parameter for determining wind loads for design is the 3-second gust design wind speed. However, the 3-second gust provides little, if any, information relative to the statistical distribution of the wind speed during the lifetime of the structure, and thus it does not allow for the analysis of fatigue life. Although much attention has been given to determining this design gust wind speed for use in the design of structures, less attention has been paid to finding a lifetime distribution of wind speeds for use in determining fatigue life. With the exception of raw data, very little statistical information is available for any particular area except for the contiguous United States as a whole. In order to calibrate the performance-based, or fatigue-based, selection method this lifetime statistical information of wind speed for specific areas is needed. Often the record of wind speed available at a particular site is not of significant length, and simply fitting an appropriate distribution to available data is not adequate. This paper discusses a technique for determining lifetime distributions of wind speeds from relatively short records. The technique is verified using five comparatively long wind speed records at locations within the state of Colorado. After verification, the technique is used to project lifetime distributions for these sites. These distributions are directly applicable to the high-mast lighting structural support selection method developed by Goode and van de Lindt. The distributions developed may also be used in any fatigue-performance evaluation or design such as cantilever signal and signing supports. Furthermore, these distributions allow for the development and application of performance-based design codes for fatigue.

Traffic signs and signals are often supported by flexible cantilevered structures that are susceptible to wind-induced vibration and fatigue. Following the collapse of a cantilevered structure in Michigan, research efforts were undertaken to better understand fatigue loading and resistance of welded details in these structures. However, minimal resistance testing was performed, and many of the details published in the AASHTO design code were untested and extrapolated from other design codes. In the past eight years multiple research programs have been undertaken to perform resistance testing of traffic signal structure details, most of which has been focused on socket connection details. The socket connection is an efficient tube-to-transverse plate connection by which a plate with a hole the same diameter as the outside diameter of the tube is cut into the plate. The tube is partially slid into the plate and circumferential welds join the plate and tube on the outside and inside of the connection. This paper will discuss a finite element parameter study that characterized how socket connection geometry affects the stress concentration factor (SCF) at the weld toe where fatigue cracks occur.

This paper presents the results of an effort to scale a woodframe structure to one-half scale for shake table testing using similitude theory. It is widely felt that woodframe structures cannot be scaled because there is no way to scale a naturally occurring fibrous material. Wood shearwalls are the primary lateral force resisting systems for woodframe structures and their dynamic behavior dominates the dynamic behavior of the system, i.e. building. Subsequently, because the dynamic behavior of wood shearwalls is dominated by the behavior of the sheathing-to-framing connector behavior, energy-based similitude was utilized at the connector/fastener level. Once the connector level was selected based on similitude of the energy in the hysteresis, a scale system/building model was developed. Shake table tests were performed for both the full-scale prototype (2.6 m x 4.88 m) and half-scale model (1.3 m x 2.44 m). Peak displacements at roof level were found to be very close, i.e. within 2%, for the largest simulated ground motion and only within 30% for the smallest simulated ground motions. Energy-based similitude is shown to provide similar displacement records. However, observed damage did not scale linearly. Specifically, the model had significantly less damage leading to the conclusion that deformation can be scaled based on energy dissipation but damage is a function of not only energy dissipation but deformation. This reinforces the notion of using a linear (or other) combination of these two quantities for damage prediction in woodframe structures such as that in the Park-Ang damage model.

This paper addresses methods and guidelines for assessing damages and distinguishing between damages caused by wind, flood and storm surge to homes and buildings from a hurricane event. These methods are based on an engineering approach that utilizes forensics, engineering science along with codes and standards to determine the extent of the damages and the various causations. A general approach to the examination of the risks is outlined, and the elements that a report should contain are addressed. Emphasis is placed on the decisive role that corroborating information plays in determining the extent and the proximate cause of damages.

This paper highlights aspects of the development of self-stabilizing links having tubular cross-sections for use in eccentrically braced frames (EBF's). EBF's utilizing this type of link could be used in bridge piers or other applications where lateral bracing to prevent lateral torsional buckling is difficult to provide. The development of design recommendations for these types of links consisted of three parts, namely, a proof-of-concept experiment, a finite element parametric study, and testing of links with various cross-sectional properties and lengths; the latter two parts are discussed in this paper. The finite element parametric study involved over 200 links with various. cross-sections, lengths, and yield strengths and resulted in recommendations for compactness ratio limits for webs and flanges of links with tubular cross-sections which were valid for a range of typical steel yield strengths. Links with three different tubular cross-sections having compactness ratios near and well below the proposed limits were then investigated experimentally. These links also had various lengths covering the full range of link behavior (i.e., shear to flexural dominated yielding). Fourteen links in total were tested. The results indicated that the proposed design recommendations were adequate to ensure tubular links can achieve plastic rotation levels equivalent to the maximum allowed for wide-flange links considering the loading protocol from the 2005 AISC Seismic Provisions.

Differential column shortening in a building structure causes axial force redistribution among columns and walls, and introduces additional forces in the horizontal members such as beams and slab. Thus, it needs to be considered in the design, especially for medium to high-rise buildings. Extensive research has been conducted to investigate this phenomenon. It has been shown that differential column shortening is affected by the relative axial stiffness and the tributary area of columns and walls. Moreover, the ratio between beam and column stiffness and the construction sequence also have significant influence on the axial force redistribution. The best way to illustrate differential column shortening phenomenon is to conduct floor-by-floor analysis, generally known as construction sequence analysis. To this end, several methods have been proposed and commercial software is available. However, to the knowledge of the authors no general conclusions appropriate for design practice have been drawn regarding differential column shortening behavior in typical medium- to high-rise buildings. General building codes do not give a specific guideline about when and how differential column shortening should be considered. Consequently, this issue is usually left to the judgment of structural engineers. Aimed at providing structural practitioners with a guideline to determine how important the differential column shortening behavior may be for a typical building system, a systemic study is conducted and reported in this paper. First, typical structural systems for medium- to high-rise buildings are identified. Next, using construction sequence analysis method, studies are conducted to investigate the influence of the variation of controlling parameters such as floor levels and beam to column stiffness ratio to the effects of differential column shortening. The results obtained in this research can serve as an aid to the structural engineers during schematic design.

Corrugated steel culverts are increasingly used in road and railway projects as an alternative solution to small bridges and tunnels. This paper describes full-scale static tests of a corrugated steel box-type culvert 1.42 m high with a span of 3.55 m. Dimensions of the corrugated sheet were 150 x 50 mm with a thickness of 5.0 mm. Two concrete strip foundations were laid under each end of the arch. The structure was tested under different standardised (Polish Standard PN-85/S-10030) and over-standardised . configurations of the road loads and various soil covers (from 0.6m to 0.0m). Deformations and strains of the steel structure were measured during tests. In order to specify displacements and stresses in the steel structure, three inductive gauges and twenty two strain gauges were installed on the inside surface of the culvert. In addition, earth pressure around the steel structure and strip foundations was measured by earth pressure cells. The prevented test was carried out at the Road and Bridge Research Institute (RBRI) Wroclaw Branch — Poland for Via-Con Company, a Norwegian culvert producer. Several full-scale tests have been performed in the field to validate the long-term performance and great load bearing capacity of these structures, but not very many structures have been tested under laboratory controlled conditions at a test facility like the one in Poland. Results of such tests carried out at RBRI have been presented in several papers.

Palm trees are located in the NW of the Persian Gulf and boundary lines of Iran and Iraq. Trees were infected by war weapons during the 8 years fight and Palms stabled during the war through the natural stability. Resistance occurs against palm trees by war weapon to prove super buckling behavior. Trees would be defined to model simulation items through the Roots (foundation system). Trunk (high building) and Head (Mass of vibration). In collapsing phase, waiting time is defined through the duration to provide structure stable and vertical. Simulation behavior is the main parameter to compute waiting time. Therefore function of convolution probability should be analyzed to obtain the simulation degree per height of tall building. Slender ratio of palm tree will consider more than 20 and height of building simulates 1000 m.

In Hong Kong, reinforced concrete columns can be designed without seismic provisions. Typical reinforced concrete columns in Hong Kong are subjected to high axial load ratio, have high main reinforcement ratio, but have very low volumetric transverse reinforcement ratio. Based on the data obtained from cyclic behavior of reinforced concrete columns specimens, a hysteresis model for low volumetric transverse reinforcement ratio was developed. It includes the effect of pinching and provides accurate overall prediction in comparison with test data on cyclic response of reinforced concrete columns with low volumetric transverse reinforcement ratio and high axial load ratio. The model will be refined after a series of 12 columns tests to be conducted in the Heavy Structural Laboratory of the South China University of Technology in March 2007.

This study focuses on the evaluation of the calculated nonlinear displacement demands for single degree of freedom (SDOF) systems. The SDOF systems, which are subjected to ground motions recorded in Turkey during Marmara Earthquake (August 17^th, 1999) and Duzce Earthquake (November 12^th, 1999), have a variety of initial period, T values ranging from 0,1 sec. to 2,0 sec. In addition, nonlinear displacement responses of the SDOF systems are investigated for different base shear strength coefficients, C_y using both Reducing Stiffness and Elasto-Plastic models. A viscous damping of 2% of critical damping is assumed. The nonlinear displacement requirements are compared to the linear displacement response spectra developed by Lepage. In the light of the findings from the earthquake records; considering the velocity increment, ΔV, an approach regarding the energy input to a system during the strong motion shaking is introduced. The concept of ground velocity increment, ΔV and its effects on the nonlinear displacement response of SDOF systems will be investigated. The correlation between maximum nonlinear displacement response and ground velocity increment, ΔV will be evaluated. The change in displacement corresponding to a velocity increment will be estimated by using an idealized model similar to those used by Westergaard and Newmark, considering a rectangular pulse of acceleration.

Stochastic finite element methods applied to large structures usually require an explicit discretization of random, fields into random variables. The computational effort required in these studies, increase with the increase in number of random variables that enter into the analysis. Based on the global importance measure, it will be possible to identify the probabilistically non-significant variables and reduce the dimension of a random design space. Kullback-Leibler (K-L) entropy measures the divergence from one probability distribution to another, and can be applied both globally and regionally. Global sensitivity analysis (GSA) with respect to basic random variables based on K-L entropy measure is applied to reduce the random variables. This procedure is done before the probability of failure is computed using global response surface. This procedure is very important in the structural reliability analysis involving performance functions with multiple design points and/or regions that influence the failure probability. This eventually reduces the computational effort associated with uncertainty assessment without sacrificing the optimum solution. The present paper deals with such probabilistic model reduction of the stochastic structural dynamic problems in the reliability analysis within the framework of response surface method.

The present paper deals with the reduction of the large stochastic finite element model with the reduction in its mechanical degrees of freedom. The procedure is based on the available reduction/condensation procedures. The response sensitivity is computed based on first and/second order sensitivities of eigensolution. The joint probability distribution of the response process is estimated using maximum entropy method. The response from the reduced FE model is compared with the response from full FE model. The analysis solution is validated with Monte Carlo Simulations.

Load combinations in Section 2 of ASCE Standard 7 are provided for both Load and Resistance Factor Design (LRFD) and for Allowable Stress Design (ASD). Included in Section 2 are combinations addressing counteracting load effects, where the permanent gravity (dead) load stabilizes the structural system. Counteracting effects occur most commonly when destabilizing forces occur due to wind uplift or lateral wind or earthquake effects. In the 1998 and subsequent editions of ASCE Standard 7, the load factor on nominal dead load in the corresponding ASD combinations has been 0.6 rather than 1.0 to achieve some measure of consistency between ASD and LRFD. This reduction has been questioned by some engineers. This paper examines the treatment of counteracting loads in ASD from a structural reliability viewpoint similar to that used to develop the ASCE 7-05 load combinations for LRFD, and explains why the reduction in the dead load factor was necessary to achieve consistent reliability between ASD and LRFD.

The evolution of spiral requirements for precast prestressed concrete piles in areas of high seismicity are the direct result of extensive engineering research over the past 20 years that has shown that pile ductility is directly related to the confinement provided by the spiral. Most codes and standards specify a minimum volumetric ratio of spiral that is a function of the applied axial load, material properties, and geometric configuration of the pile. Such prescriptive requirements are not performance based and may not ensure a ductile response of the structure. In many cases, piles designed prescriptively may be way overdesigned for the actual seismic displacement demand. Most research to date has focused on large dimensional piling (i.e., greater than 15 in. diameter) that is applicable primarily to bridge and pier/wharf type structures. Building typically use much smaller piling and the results of bridge and pier/wharf piling research has been too conservatively extrapolated to 10 in., 12 in., and 14 in. square piling commonly used in the building industry. Based on a target curvature ductility value of 20 for pile-to-pile cap connections, the results of a comprehensive parametric study of over 2,500 pile configurations is presented for 10 in., 12 in., and 14 in. square piles. Moment curvature analysis that neglects the contribution of soil confinement is utilized and the results are presented with respect to building foundations.

A large number of reinforced concrete (RC) buildings and bridges is deemed structurally deficient. This is either because the infrastructure continues to age and deteriorate or the strength or deformation capacity of the existing older infrastructure does not meet the current code requirements, e.g., in high seismic regions. Thus, the need for more efficient retrofit methods has increased in recent years. Currently, there are only a few methods used for strengthening or retrofitting columns. Steel jackets and Fiber Reinforced Polymer (FRJP) composites are the two most commonly used methods. In this study, along with these two retrofit methods, concrete jackets reinforced with spiral rebar, Welded Wire Fabric (WWF), and a new steel reinforcement termed PCS are investigated under different axial load conditions.

In applications where structures are subjected to moderate earthquake or when small inter-story displacement are expected, the conventional usage of energy dissipation devices may not be suitable. In this paper, a hydraulic displacement amplification damping system (HDADS) is proposed to retrofit non-seismic reinforced concrete beam-column joints. HDADS is based on a group of hydraulic cylinders connected to fluid viscous dampers. Two 1/2 scale reinforced concrete beam-column joint specimens designed for gravity loads only and without seismic provisions were constructed. At the end of October 2006, the specimens were tested under reverse cyclic displacements at low frequencies. Based on the hysteresis responses of the specimens, performance of HDADS under repeated cyclic displacements were assessed. The experimental results indicate that HDADS is an effective and convenient energy dissipation system for the strengthening of reinforced concrete beam-column joints.

The shear failure of reinforced concrete (RC) beams is due to the combined action of shear and flexure. Because of the presence of shear, beam flexural strength may result greatly reduced with respect to the pure flexure case, and failure may happen in a brittle way and without premonitory signs. Due to the complexity of the phenomenon, much research has been addressed to evaluate the resisting mechanisms of only longitudinally reinforced beams, currently called concrete mechanisms. The analysis of shear strength of reinforced Normal Strength Concrete (NSC) and High Strength Concrete (HSC) beams with only longitudinal reinforcement, in which a constant shear force acts throughout the shear span, has led the author to recently propose a shear strength formula [Russo et al., 66–74] predicting the experimental behavior in a more accurate and uniform way than other authors and Codes expressions. The shear mechanism has found to be governed by a second order differential equation, whose solution provides the internal lever arm in function of the distance from the support. The strength provided by any transverse reinforcement, which is supposed to be constituted by stirrups in almost every study, is hence taken into account by adding the resisting contribution of the truss mechanism to that due to the concrete mechanisms. In the transverse reinforcement contribution the stirrup effectiveness is taken into account.

The principal metal shop for Eastman Chemical Company produces many very large tanks and other kinds of vessels for the company. Arguably the most important machine in the shop is the CNC plasma arc metal cutting machine because every tank starts with the cutting of the plates for the project. The management of the shop requested that I design a structural system to allow more floor space in the shop to make room for a new larger CNC plasma arc machine. The old machine was getting worn, breaking down often, and threatening to shut the shop down. The problem was that the new machine would not fit in the shop without cutting a W21 x 111 main column supporting three large bridge cranes, and the high and low roof, with a total design load of over 200,000 pounds. This paper will describe the details of the tubular steel arch that I designed to .carry this concentrated load allowing removal of the W21 column, creating floor space for the new CNC machine. The arch was required to carry the loads with a minimum of deflection to limit crane girder sag. The method of design, including the handling of the leg thrust reactions, and foundation modifications are covered. The details of fabrication of the arch in place, including the design of the weld splice details are presented. Once the arch was completed and the column removed the needed space was created with minimal interference with the operations of the shop. The arch spans over 40 feet, is approximately 18 feet high at the crown and is loaded entirely at the crown.

Water seepage is a potential hazard to multi-story buildings worldwide and in particular Hong Kong. It has led to lots of civil actions and the Court general relies on expert opinion on the finding of facts. In establishing the cause of action, identification of the sources of water seepage is usually more important than that of the causes of water seepage. Both the external sources and the internal sources of water seepage may be identified by carrying out infrared thermo-graphic inspections after conducting water tightness tests, flooding tests or hydraulic tests as appropriate. Color dye tests may lead to non-conclusive results since it could take a few weeks before the colored water to finally appear on the surface. As for the internal of a building, bathroom is probably the area where majority of the water seepage problems occur. This is due to the use of sea-water in the flushing system. Thorough understanding of the causes of water seepage is useful to identity the appropriate means of repair. Applications of injection grouting or cementitious based material with ability of capillary action or in-depth crystal growth are recommended for the repair of concrete against water seepage.

In recent years, new combinations of shape, height and configuration of buildings have induced intense near ground wind flows, which can cause unacceptable human discomfort. Therefore, the wind environment in public access ways and leisure areas has become a major design consideration in new and existing building complexes. Recently, Computational Fluid Dynamics (CFD) has become a powerful tool for the study of environmental problems, as this technique is more feasible and cheaper than other methods, namely the wind tunnel technique. This paper deals with one of the most common situations of urban planning, which lead to the amplification of the ground level wind speed around a 56-story tall building with especial architectural plan which consists of three wings with identical plan dimensions of nearly 48 meters by 22 meters which are placed at 120 degree from one another in the vicinity of three other 36-story tall buildings with rectangular architectural plan. A CFD program FLUENT, is used to illustrate the effectiveness of these building arrangement in increasing the wind speed and the correspondent discomfort level. Some design practices for the avoidance of severe induced wind speeds around buildings will be inferred from the present analysis, which can be useful for engineers, architects and urban planners.