Structures Congress 2019: Buildings and Natural Disasters

This paper presents an “innovative” structural system, aiming to provide a cheap yet reliable, and very effective seismic protection to residential houses/buildings, characterized with abundance of masonry infill wall panels. This is achieved through use of innovative IDRIZI seismic devices (based on a combination of two-layered friction/sliding mechanism), which are placed at characteristic locations between the masonry infill walls and the structural frame system of the building. An analytical study, supported by experimental research, indicates that buildings utilized with this innovative frame/wall system, dissipate up to 80% of earthquake energy input through the friction mechanism of IDRIZI seismic devices.

The Independent—the latest high-rise in Austin, Texas—is the tallest concrete residential high-rise west of the Mississippi. LAM+DCI was the engineer of record for the 63-story high-rise totaling 89,930.5 m² (968,000-gsf); 360 residential units; and 728 parking stalls. This paper covers the design challenges required to develop a simple and cost-efficient structural system for The Independent; to accommodate wind loads based on the building’s shape and orientation; and to maintain the leading edge architectural design of the building with an economical solution. These results were achieved through coordinating the construction sequencing, including contractor means and methods; a basic grid of concrete corner columns and mega columns supporting post-tension slab and tension rods supporting extended cantilevers; a lateral design with a thin concrete building core, an outrigger system, and tuned liquid sloshing damper tank.

As the population of the United States both grows and ages, the demand for healthcare facilities has grown steadily. Within the healthcare industry, new construction has been trending towards outpatient facilities, like medical office buildings (MOBs) and skilled nursing facilities (SNFs). In this paper, the special structural engineering considerations common to MOB design are discussed. With healthcare buildings, flexibility of future use is an important consideration. MOBs, in particular, are often delivered in two phases. The first phase delivers a core and shell package, and the second addresses tenant improvements (finishes). Strategies for success with this delivery method will be discussed. Additionally, code minimum design loads are often insufficient for heavy imaging equipment. X-rays, CTs, and MRIs can have special requirements for vibration response, structure levelness, and magnetic interference. Final designs require an understanding of the manufacturer’s equipment specifications and specific building criteria. However, those specifications are not always available to the design team during the core and shell design. For that reason, this paper provides appropriate design assumptions and highlights best engineering practices for successful MOB design.

Seismic friction damper application for the seismic retrofit of a concrete building in a high seismic zone. The system is designed using a conventional force-based method and reduction factor. For the first time the yielding restrained brace (YRB) concept is presented, relying on limiting the forces in braces by using Ten-Co friction dampers. The system is compared against two alternatives, concrete shear walls and Buckling restrained braces (BRBs). Effectiveness of the method and system is then confirmed by a NLTH. Results show high seismic performance of the proposed system with little to no ductile damage in the structure.

Topology optimization is a free-form approach to designing efficient structural layouts. Although highlighted repeatedly in literature for its ability to identify creative, high performance designs, it is also well known that oversimplification of the underlying optimization formulation can lead to impractical structural solutions. A common truss optimization problem formulation is to minimize linear elastic strain energy for to a given structural mass (or minimize mass subject to a linear elastic deformation constraint). The optimal solutions obtained from such a formulation may often include thin members that cannot resist yielding or local buckling, and/or may include colinear members with unbraced hinges that destabilize the structure. Such solutions are, of course, impractical from structural engineering perspective. Incorporating stress and local (member) buckling constraints into the problem formulation to satisfy strength and stability requirements has been studied in literature and involves significant fundamental challenges. The authors review and discuss these challenges in this paper and extend an existing disaggregated formulation to include global (system) buckling constraints. The impact of each of these constraints on the optimized solution when applied independently as well as simultaneously is demonstrated for simple truss design problems. Although the algorithm is currently being scaled up to large design domains, the presented results clearly show that the incorporation of stress and local and global stability constraints results in more realistic design solutions.

Chevron bracing is a common configuration for concentrically braced frames. Typically gusset plates are used to connect the braces to the frame in such braced frames. One of the common issues in brace connections is the uneven stress distribution across the welded gusset edge. The development of a peak stress induced at some point across the welded connection might cause the weld to fail at the point where the stress is concentrated causing an unzipping of the weld and a progressive failure of the welded connection. A weld ductility factor has been used to account for the uneven connection stress distribution. However, the limited experimental work on which the ductility factor is based was performed considering only corner gussets. This study evaluates the ductility factor value for chevron (middle) gusset plate connections. In order to do so, a group of twenty assemblies, each consisting of a beam, rectangular gusset(s) with chavron V- and X-type bracing configuration, and the beam to gusset(s) weld connections are designed, and then modeled in a finite element software to check the stress distribution along the weld line. Based on the obtained results, the common weld ductility factor value should be increased to a larger amount for the case of chevron gusset plate.

Wood is one of our most sustainable materials. It requires less energy to produce and deliver to the project location than steel, concrete, masonry, or other materials. Timber products sequester a significant amount of carbon in comparison to the amount of carbon expended during harvest, manufacture, and transport. Timber structures have generally performed well in earthquakes and wind storms if constructed according to the building codes and good construction practice. Timber structures often have a cost advantage over other types of structures. However, “sustainability” is not an “either/or” proposition. A sustainable material can become more sustainable or less sustainable depending on a number of factors. In wood construction, some methods or techniques of manufacture and construction are more sustainable than others. Wood is a sustainable material, and wood structures can be sustainable, but many of these advantages are lost when timber structures perform poorly, fail prematurely, or when the structure needs substantial repair or replacement early in its life cycle. The ASCE/SEI Committee on the Performance of Wood Structures has been charged with determining the controllable effects of material conditions, fabrication, and workmanship on the life-cycle performance of wood structure. The task has been broken into several portions: moisture effects, construction and fabrication, fire, and QA/QC methods. This part examines how fabrication and construction methods or techniques affect the overall performance of a wood structure. Better performance leads to a longer structural life, hence keeping the sequestered carbon bound for a longer period of time. If the useful lifespan of typical wood buildings is increased by reducing the number of defective buildings demolished, then the built wood infrastructure increases. Then the total sequestered carbon in all wood construction increases. This study examines fabrication practices include the effects of poor lumber storage, tolerances in fabrication and fit-up and the effects of assembly and construction error repairs, and how better practices can improve the sustainability of wood structures. These practices will also create a heightened expectation of sustainable wood construction quality and fabrication professionalism which could lead to sustainable wood being used for structures where steel or concrete would otherwise be employed. Lessons learned from these studies can lead to reduced defects in the future and to enhancing the sustainable nature of wood construction. This paper will broaden the knowledge of practicing engineers, preparing them for the challenges of the 21st century. It will assist them to be knowledgeable in factors affecting sustainability and to become better stewards of materials and the built environment.

The precision of wood construction and quality of wood structures are perceived as being lower than those of steel, and reinforced concrete, and masonry structures. These latter materials have well-established, detailed standards of practice, where the existing standards for wood are mostly product-specific and aimed at manufacturing tolerances and methods. Forensic studies conducted on wood structures substantiates this perception, more often pointing to poor construction execution or material specification in lieu of a flawed design. This paper examines the role of damage mechanisms caused by decay fungi. The state of the art in research regarding non-destructive detection and wood preservation is briefly reviewed, followed by a review of the state of current practices regarding the biodeterioration of structural wood by decay fungi, including initial deterioration identification, determination of decay severity, and damage mitigation measures. A case study of multiple residential condominium buildings is included to highlight these processes. Leveraging findings from research, practice, and the case studies, preliminary recommendations are offered for adoption into a standard of practice for wood structures for design, construction, and service.

The Hospital for Special Surgery (HSS) new River Building consists of eleven stories plus a mechanical penthouse covering a footprint area of approximately 804 m² (8650 ft²) which will be connected to the existing HSS buildings. The River Building will span over the FDR Drive, one of the busiest roadways in Manhattan. The building frame consists of entirely structural steel with a total weight of approximately 2500 tons. This paper discusses the major challenges faced in designing and planning the construction of the new HSS building. Not only must the building span 31 m (100 ft) across the FDR, but it is also required to maintain 6.10 m (20 ft) clear height for underneath vehicles. This results in using a mix of transfer girders and multi-story high trusses along the north-south faces of the building in addition to moment frames to enable the structure to span over the FDR. Due to the sloping rock profile underneath the building and the limited footprint available for the foundations, a combination of reinforced concrete caissons with rock anchors are used on the east side. On the west side, spread footings bearing on shallow bedrock are used. Computational fluid dynamics (CFD) analysis is performed to demonstrate that the building can withstand an extreme event such as car fire right adjacent to the building. The CFD analysis results provided transient temperature variations for the exposed steel members. These data were then used to calculate the reduction in steel strength and stiffness. The reduction in steel material properties due to fire was considered in the analysis and design of the building for both strength and serviceability. The structural framing system is designed for off-site modular construction due to the limited work area available, crane pick limitations, and to minimize disruption to the FDR. The modular construction plan involves utilizing the East River to transport pre-fabricated modules via a barge then lifting them into place above the FDR.

Steel multi-tiered concentrically braced frames (MT-CBFs) are commonly used in North America as lateral load-resisting systems of tall single-story buildings. MT-CBFs are composed of multiple tiers of diagonal braces stacked on top of each other along the height of a story. Past research showed that MT-CBF columns designed in accordance with the 2010 U.S. Seismic Provisions are prone to column buckling due to non-uniform distribution of inelastic seismic demands along the frame height. Special design provisions have been introduced in the current AISC Seismic Provisions to address limit states and ensure columns remain stable under seismic load effects. Nevertheless, the recent improvements lack full-scale experimental testing and comprehensive finite element simulations to validate the proposed design requirements further and improve design provisions. In this paper, the current seismic design provisions for multi-tiered special concentrically braced frames (MT-SCBFs) are evaluated using the finite element method. A two-tiered SCBF was first designed in accordance with the 2010 and 2016 AISC Seismic Provisions. A detailed finite element model of the frame was then created using the Abaqus program. The model was used to perform nonlinear history response analyses. The analysis results showed that the inelastic deformations in the frame, designed as per the 2010 AISC Seismic Provisions, are not uniformly distributed but rather concentrated in one of the tiers, which leads to column yielding and buckling. Whereas, the current design method led to distributing the frame’s inelastic deformation along the frame height. Furthermore, it was found that column in-plane flexural demands are overestimated when the current seismic provisions are employed; however, the out-of-plane flexural demand of columns exceeded the code-specified demands.

The rapid spread of high temperature within the steel material results in low fire resistance of steel structures. Various types of methods have been utilized in order to improve the stability and load-bearing capacity of the steel structure during fire incidents. Passive fire protection (PFP) is a popular method used in industrial and residential buildings to protect steel structures against fire. In PFP method a material with high thermal capacity is applied around the steel sections to reduce the heat transfer to structural steel elements. Spray-applied fire protection, concrete encasement, and gypsum boards are different types of PFP methods. Spray-applied fire-resistive materials (SFRM) are commonly applied material to protect steel structures from fire exposure. Some of the widely used SFRMs include CAFCO, Carboline, and Tyfo. SFRM offers many advantages over other types of fire insulation methods such as cost-effectiveness, lightweight, and ease of application. However, the applied fire protection material may be removed due to inappropriate applications and accidents. The direct exposure of the steel material at damaged regions can result in failure of the structural steel elements before the required fire rating of the structure is achieved. The primary goal of this study is to investigate the reduction in the fire resistance of steel beams with damages in the fire protection material. Steel beams protected with fully protected and damaged Tyfo, CAFCO, and Carboline fire protection material were simulated. The fire resistance of different steel beam sections with damaged fire protection has been investigated. The fire protections were designed for one-hour fire rating. Nonlinear thermal and structural finite element models of beams with damaged fire protection were developed. The temperature of various parts of steel beams, as well as mid-span deflection of damaged cases, were tracked and compared with cases with full protection. The results have shown that the fire protection loss can result in significant fire resistance reduction of the beams. This study’s contribution highlights the need for considering the influence of such damages in fire protection material in the design of fireproofing of steel structures.

Conventional building codes address a wide range of facilities that have various performance requirements, hence, facilities are assigned risk categories (RC) ranging from RC I to RC IV. However, there are certain groups of facilities that are required to go above and beyond RC IV, consequently, United Facilities Criteria 3-301-01 introduces an additional risk category designated as RC V. Such facilities are classified as national strategic military sssets that don’t tolerate business interruption. This article discusses the design provisions for Risk Category V structures, and the certification process for the mission critical non-structural components. Also, the construction and design challenges are highlighted.

Special concentrically braced frames (SCBFs) rely on yielding and buckling of the braces to achieve ductility of the system. AISC 341, Seismic Provisions for Structural Steel Buildings, requires designers to evaluate the columns, collectors, and connections in SCBFs for the capacity-limited seismic load effect associated with the expected strengths of the braces. In practice, especially for simple or regularly-shaped buildings, designers often compute these force demands by hand and manually combine them with the demands from other loads. However, for irregularly-shaped or atypical buildings, such as large industrial buildings without diaphragms or structures with unevenly distributed mass or stiffness, this can become an arduous task, especially during an iterative design process. The method described in this paper allows designers to automate a plastic mechanism analysis of an SCBF in an analysis model by imposing artificial self-straining (thermal) loads to emulate the capacity-limited seismic load effect.

Steel trusses are very efficient structural members. Steel trusses in this paper, commonly referred to as open web steel joists, can span long distances and support large loads relative to the weight of the steel joists. In the past 30 years research has been completed looking at the additional benefits associated with making the steel joists composite with the supported steel deck and concrete slabs. This paper outlines advantages for utilizing the Steel Joist Institute’s (SJI’s) CJ-Series composite joists, optimal joist spacing, suggested loading designations, typical vierendeel panel configurations and locations, calculation of a CJ-Series joists ultimate moment capacity, design of welded shear studs on CJ-Series joists, typical referenced UL fire ratings, methods for predicting floor vibration, SJI’s floor bay tool, and description of typical projects in the Boston, MA, area recently utilizing SJI CJ-Series joists.

There is an increasing awareness in the engineering and stakeholder community to include seismic resiliency and eco-sustainable construction practices in the design of building structures within densely urbanized cities in regions of high seismic risk. Mass-timber construction has risen as one type of system to meet both these challenges. Recent studies on self-centering cross-laminated timber (SC-CLT) walls have shown high promise for use in multi-story mass-timber construction subjected to large earthquake loadings. These walls provide self-centering through wall rocking in combination with elastic elongation of vertical post-tensioned elements. Inelastic seismic energy dissipation is provided through structural fuses that are decoupled from the gravity frame. One area of limited knowledge in these wall systems is the effect of large wall openings. This paper presents preliminary results on an ongoing study by the authors investigating SC-CLT walls with CLT and steel coupling beams at large wall openings. Here, the steel coupling beams are detailed with replaceable structural fuses and compared to walls with monolithic constructed CLT coupling beams. Furthermore, an innovative wall base uplift friction damper is proposed as an alternative to steel yielding anchorage elements providing additional energy dissipation and self-centering capability. Nonlinear pushover analyses results of finite element models are presented providing insight in the fundamental behavior of this rocking wall system.

Concrete slabs are common members in building structures. Hardened concrete materials are strong in compression and relatively weak in tension and are used to withstand compressive stress in structures. Cracks in concrete occur when tensile stress exceeds the strength of concrete in tension. Significant cracks prompt the project stakeholders to question the integrity of the structure and to retain investigation teams to determine the extent of defects or distresses, identify potential causes, and assist in developing a remediation plan. Non-destructive evaluation (NDE) techniques have been gaining interests for field assessment. Properly conducted NDE shortens the time of assessment, saves cost, and provides information that is not visible to human eyes. The authors have served in many projects of structural assessment and realized the lack of knowledge on NDE techniques in the field. It is the intent of this study to discuss the advantages and limitations of NDE techniques. The projects presented include investigations of a reinforced concrete floor slab, concrete slab-on-grade system, a composite floor system, and a reinforced concrete pad foundation.

Heightened public awareness regarding carbon footprints has dramatically increased the demand for sustainable construction and has initiated resurgence in the use of wood in tall residential and non-residential buildings. Together with the development of advanced connectors, the introduction of cross-laminated timber (CLT) represents tremendous potential. Reliable design guidance is needed for a successful implementation of CLT in the construction market. While designing CLT panels for ultimate limit states is straight-forward, designing for serviceability limit states as well as designing the connections between panels and the anchoring of the panels to the foundation is a challenge. This paper and the presentation give an overview on the CLT design provisions that were included in the 2016 supplement to the Canadian Wood Engineering Design Standard and the revisions included in the 2019 updated version of the standard. These provisions are limited to platform-type construction with CLT panels exhibiting a certain aspect ratio. The provisions from other leading standards of the world, notably the U.S., New Zealand, Japan, and Europe will also be compared. Considering the global need for more sustainable building solutions, this session is of international interest. Furthermore, the presentation will summarize the findings of several research projects that developed design guidance for CLT structures. Amongst there are the design of CLT shear walls with openings, shear connections with self-tapping screws between wall panels, and novel hold-down solutions to the foundations. Ongoing research is providing findings that are ready for code implementation and can directly adopted by design practitioners.

Slag aggregate has been used extensively in the concrete mixtures as coarse aggregate due to its economic and environmental benefits, especially in the north of Ohio, where steel factories produce a high amount of it. To improve the mechanical properties of concrete such as flexural, shear, and tensile strength, synthetic fibers have been used for decades. However, there are limited studies regarding the shear performance of slag aggregate concrete reinforced with synthetic fiber. The objective of this study is to evaluate the performance of synthetic fiber reinforced concrete beams under pure shear loading. Fiber contents of 0.25, 0.5, 0.75, and 1.0% with three different lengths, 0.75 in. (19 mm), 1.5 in. (38 mm), and 2.25 in. (57 mm) were used to investigate the effects of fiber length and content on the shear performance of concrete. Concrete prisms with a dimension of 3×3×14 in. (75×75×356 mm) (width×depth×length) were tested. An innovative test method was utilized to apply a pure shear force on the concrete specimens. Results showed that using synthetic fiber improved the shear strength of slag aggregate concrete specimens. This improvement was proportional to the fiber content and length. As the fiber content increases, the post-cracking behavior enhanced due to the increase the number of fiber bridging propagate cracks. It was observed that fiber length has a significant impact on the post-cracking behavior. As the fiber length increases, it was observed that tested specimen sustained load even though the crack width increased. This behavior mainly is attributed to that long fibers have more embedded length compared to the short fiber, resulting in higher bond strength and higher post cracking. Also, it was observed that specimens reinforced with fiber length of 1.5 in. and 2.25 in. (38 and 57 mm) experienced fiber pull out and breakage. On other hand, specimens reinforced with fiber length of 0.75 in. (19 mm) experienced fiber pullout. Therefore, it is recommended using fiber with a concrete mixture containing slag as coarse aggregate due to its high impact on the shear performance.

Extended shear tab connections have been more in use today in the industry due to the solutions it provides to some construction issues. As well AISC specifications allow the use of some extended connection configurations as long as they satisfy simple shear connection requirement of adequate shear strength and flexible end beam rotational ductility. By AISC, single plate shear tab connections are required to accommodate beam end rotation of 0.03 radians. The objective of this study is to investigate the rotational ductility of extended shear tab connections framed to flexible supports. The behavior of extended shear tab connections is observed to change with the type of support and it becomes a concern when the connection flexibility is not satisfied. As flexible support like column webs would possess substantial distortions resulting in yield line mechanism failure. To address these concerns finite element models were prepared and a parametric study was performed on the models. This study helps analyze the effects of parameter variation on the rotational ductility of the connection, define parameter ranges, specify design constraints, and nominate parameters for further evaluation.

The increasing number of natural disasters affecting communities worldwide is pushing the limits of existing residential and infrastructure resiliency during storm events. The New York City Build It Back program, administered by the Mayor's Office of Housing Recovery Operations, was created to assist homeowners, landlords, renters, and tenants affected by Hurricane Sandy within the five boroughs. The primary goal of the program is to make Sandy-affected New Yorkers and communities safer and more resilient. In the hardest hit waterfront communities, Build It Back is rebuilding and elevating almost 1,400 homes to today’s stringent regulations for flood compliance. The scope of the paper is to share the knowledge gained in this program showcasing the experience acquired and the methodology applied in the phase of construction of the project.

The roof of the New International Airport for Mexico City is a lightweight steel shell structure and an architectural centerpiece of the new 4,432 hectare greenfield airport development. Visually exposed and structurally independent from the building beneath, it supports a 500,000 m² envelope that reaches a peak height of 45 m above ground level and maximum span-to-depth ratio of nearly 60:1. While it is comprised of several subassemblies, including a 2-layer tetrahedral ball-node space frame and single-layer welded CHS shells, the roof was designed and detailed with the overt intent of achieving seamless visual continuity across the entire system. It is a mile long, nearly half a mile wide, and is achieved with no movement joints. This paper outlines the team’s approach to form-finding and design of the system’s sub-assemblies. It provides an overview of the most significant structural hazards and the analytical methods employed to optimize the system for steel tonnage.

External confinement of concrete columns by means of carbon fiber reinforced polymer (CFRP) wraps have proven to be an efficient technique for structural retrofitting and strengthening. This paper presents experimental investigation to assess the residual compressive strength of CFRP wrapped 1/6-scale concrete columns using strips to enhance confinement while still enabling visual column inspection. The experimental work is carried out to evaluate the remaining strength and stress-strain behavior of partially damaged concrete columns externally retrofitted with CFRP strips. Fourteen (14) cylinder specimens are constructed, instrumented, and tested in seven groups, including fully double-layer vertically and horizontally wrapped, partially wrapped with 2-strip, partially wrapped with 3-strip, fully single-layer vertically and horizontally wrapped, and unwrapped concrete column specimens with 4 in. diameter and 16 in. height. The same concrete mix and curing conditions are used throughout the study to achieve 4,000 psi compressive strength in 28 days. All test specimens are subjected to monotonic uniaxial compression loads in two steps: (1) before retrofitting and loading up to 70% of failure point, and (2) after retrofitting and loading up to failure. Several parameters that influence confinement effectiveness of CFRP and increase the residual compressive strength of retrofitted column were evaluated including the number of CFRP composite layers and fiber orientations with respect to the circumferential direction. A finite element model was developed using ANSYS 19.2 to compare with the test results, and a close agreement achieved.

FEMA P-58 is comprehensive performance-based earthquake engineering (PBEE) loss estimation framework which incorporates a three-module Monte Carlo simulation (MCS) procedure to assess the seismic performance of buildings. Although the framework is component-based—it accumulates damage from all building components to estimate the building-level losses, each simulation first checks for two system—or building-level damage states, namely, collapse and irreparability. The current version of FEMA P-58 estimates irreparability solely based on the residual drift of the building, but in reality an impacted building may be condemned for demolition depending on a variety of factors which include structural, strategic, and financial decision variables. In order to overcome the observed shortcomings, a revised loss assessment framework is proposed in this paper. Thereafter, two illustrative examples are presented whereby the vulnerability functions for two select building types are assessed and compared using the proposed new method and the FEMA P-58 approach. The analysis results show that the inclusion of the FEMA P-58 irreparability model often results in overestimation of direct building losses.

Investigations of construction related metal-plate-connected wood truss collapses may involve multiple engineers or other experts. Often, one or even all of the investigators will determine the temporary truss bracing and anchoring did not satisfy relevant guidelines. One or more investigators may then prematurely and incorrectly conclude the collapse was caused by inadequate anchoring or bracing. Many long-standing buildings have trussed roofs with only minimal bracing, far below current industry norms. Inadequately braced truss systems that have stood for years or decades are sometimes discovered in a pre-collapse condition. Often, it is feasible to repair resultant damages and install appropriate bracing to restore the roof truss system to a functional and safe condition. Thus, lack of recommended bracing does not always result in collapse but may be the cause of the collapse being investigated. “Adequacy” and “conformance with a guideline” are not interdependent concepts. Examples of well braced truss system collapses are reviewed to illustrate how other, equally important factors can contribute to truss collapses. It is necessary to evaluate all of the possible causes of a collapse to reach a definitive conclusion about the actual cause(s). Concluding that the truss bracing did not conform to a particular guideline or design is not the same as concluding that inadequate bracing was the cause of the collapse. It is not that simple.

For nearly two decades buckling-restrained braces (BRBs) have been used in the United States as bracing elements in the main lateral force resisting system of braced frame buildings. However, only recently have BRBs been used in alternative structural applications, including in stiff spine frame systems and as fuses to limit the force imparted into other lateral force resisting elements. Given the versatility of BRBs, it is only a matter of time before the industry starts to use them in other structural systems. The creation of multiple BRB components by arranging BRBs in various configurations could replace the yielding regions of other lateral force resisting systems, providing more control over the post-yield behavior of a building and easier replacement of yielded regions after an earthquake. These components could be used in coupled shear walls, eccentrically braced frames, and moment frames.

When the building in question has historic significance, there is the added question of sustaining cultural heritage. Retrofitting and reusing such historic structures instead of demolishing and rebuilding them is an appropriate response to sustaining heritage. The integrated structural solution to each building is specific and creates unique challenges in design and construction. The challenges are presented herein for the Strand Theater in San Francisco, the Desmond Building in Los Angeles, and the Veterans Affairs Medical Office Buildings in San Francisco.

This paper aims at delineating the various aspects of resilient design of single or multi-family houses subjected to extreme environmental loads with a focus on Hurricane Sandy in New York City area. Emphasis of the case study is on the design of resilient foundations. Due to proximity of the buildings to the profoundly deteriorating bulkheads at the shore line and potential risk of failure as a result of flooding, lateral stability of the structures is a significant aspect of the resilient design. In this paper, the approach taken to ensure resiliency of the foundations against lateral loads is discussed. Other design aspects such superstructure and foundation connection and roof framing design is briefly discussed. A reliability analysis method is adopted to assess the degree of resiliency of the structures against the same wind load as in Hurricane Sandy. Response surface method based on first order reliability method (FORM) is employed to compute the reliability index for soil friction angle and pile head rotational stiffness as stochastic variables. The analysis results ensure resiliency of the structures constructed based on current design.

Elevated buildings, such as those on stilts or piers, have found a common use particularly in coastal regions for avoiding floodwaters and to minimize hydrodynamic loading from storm surge during high wind events or otherwise. Though these raised structures are typically well-designed for the hydrodynamic loading from flooding waters, storm surge, and carried debris, there is limited code guidance on the wind loading. An experimental program was conducted at the Florida International University Wall of Wind Experimental Facility using a scaled model of a single-story residential home elevated to various heights, during which wind loading was measured for different wind directions. Wind pressure coefficients on the elevated building model surfaces were found to be generally greater than or equal to those for the non-elevated model, and measured floor pressures were comparable to those on the roof. These findings provide critical impetus for continued research, and potential for updating relevant code provisions.

This paper presents a conceptual framework for improved situational awareness in severe rainfall events like hurricanes or tropical storms by coupling a flood alert system (FAS) with a model for transportation infrastructure performance assessment referred to as the access to critical facilities (ACF) model. The FAS is a flood modeling and alert system that leverages state of the art flood modeling and rainfall radar data in an efficient manner. The ACF model comprises of a road network of the study area, census data, locations of critical facilities like hospitals and fire stations, and a spatial and network analysis toolbox written in Python. The proposed framework can be used to evaluate, in near real-time, system level performance such as accessibility to critical locations and component level performance such as potential impacts on roadways. As a proof of concept, the coupled framework is applied to the White Oak Bayou watershed, Houston, Texas. First, the hydrologic and hydraulic characteristics of the watershed are captured through inundation maps forming a floodplain map library (FPML). Second, five accessibility measures quantifying mobility and accessibility are evaluated for each inundation map to develop the accessibility map library (AML). During a storm event, real-time radar rainfall data is used to identify the pertinent scenario from the FPML and AML. The selected maps are then communicated to stakeholders to support emergency response and situational awareness. Further, the results from the framework can also be used for disaster mitigation planning. Although demonstrated on a single watershed, the methodology developed in this study is transferrable to other regions to develop an integrated flood alert system in support of emergency response and longer-term resilience goals.

The M_w 5.3 Sulphur Peak earthquake in Idaho occurred on September 2, 2017. The epicenter was located in the east of Soda Springs in Idaho. The earthquake caused moderate shaking in southeastern Idaho, northern Utah, and western Wyoming. There were no reports of damage or death following the main shock. An active sequence of smaller aftershocks followed the main shock. This was very uncommon for an earthquake magnitude of this scale. The region is known to have moderate-to-high seismic hazard. Following the main shock, the United States Geological Surveying (USGS) had a scenario where it was likely that an earthquake of M_w 7.0 could happen in the region. The area’s seismicity and vulnerability of civil infrastructure in the nearby cities as well as potential for liquefaction, have not been studied in detail. This paper presents available data on seismicity of southeast Idaho. It uses ground motion records from the Sulphur Peak earthquake sequence to build the response spectra in accordance with ASCE 7-16. Preliminary findings from the response spectra and lessons learned from past earthquakes are discussed.

Hurricane Harvey devastated the Gulf Coast of Texas when it made landfall as a Category 4 hurricane in August of 2017. Several research teams, including one supported by the Geotechnical Extreme Events Reconnaissance (GEER) Association, performed structural assessments to evaluate the damage caused by the storm event. One of the many observations by the research team was the disproportionate damage to residential roofs, depending on the roof covering type (i.e. asphalt shingles, tiles, or metal). The team evaluated and categorized damage by roofing material to better understand the performance of each system. For residential structures, the percent of each roof type within a damage category was determined. The damage categories were determined by the structural assessments where each structure was categorized by the percent damage for each element (i.e. roof cover, roof sheathing, etc.). The results show that metal roof systems perform the best, followed by asphalt shingles, with tile systems performing the worst.