Journal of Performance of Constructed Facilities

The present paper discusses the challenges of retrofitting buildings to meet current progressive collapse guidelines. The knowledge of the structural capacity depends on the quality of information available. The existence of original drawings greatly facilitates the understanding of the design intent. However, drawings are not always available and information must be also obtained through on-site testing. A case study of the retrofit of a 5-story flat plate concrete structure is presented, where the floor slabs are hung from a new steel girder located above the roof using high strength steel rods. Neglecting the contributions of the existing structure, the failure mode of this system is ductile beam flexural mode. However, the analysis presented show that a brittle shear failure at the slabs can occur when the existing concrete column and its reinforcement are incorporated into the analysis.

The main function of a façade system is to provide comfort and protection to occupants inside the building. Glass façades are susceptible to severe damage due to their direct exposure to extreme loading conditions, such as blast. There is increasing popularity in the application of double-skin façade systems (DSFSs) in modern façade construction practice due to their high energy efficiency. In addition, when designed correctly, DSFSs exhibit a potentially higher capacity for blast resistance as opposed to single-layer façade systems. However, due to the complex fluid–structure interaction (FSI) between DSFSs and blast waves, there is a lack of design codes that address the structural response of DSFSs subjected to blast pressures. Understanding the behavior of the pressure within the DSFS cavity will facilitate the analysis of the blast performance of DSFSs. This paper reports an experimental program on analogical DSFSs made of steel as opposed to glazing panels, subjected to 250-kg equivalent TNT explosives at a standoff distance of 52 m. The test module contains three DSFS units. One of the DSFS units is sealed and the other two DSFS units are ventilated with a varying ventilation area. The computational fluid dynamics (CFD) code Air3D was used to simulate the cavity pressure behavior of the ventilated DSFS units. By analyzing the pressure time histories from the CFD analysis and the experimental results, the concepts of shock wave transfer and blast pressure ingress formed within the cavity were introduced to interpret the cavity pressure behaviors. A parametric study was conducted to investigate the influences of the ventilation area and the cavity volume on pressure changes within the cavity.

Rapid analytical methods for the calculation of gas explosion overpressures in confined and congested regions are of great value where a benchmark value is sought rather than a time consuming detailed analysis obtainable by computational fluid dynamics (CFD). While earlier correlations have been compared directly to experiments, the geometries used were often simplistic and displayed homogeneity in confinement and congestion. Realistic geometries typically display a high degree of inhomogeneity in confinement and congestion. Here the authors examine geometries where the confinement and congestion were deliberately varied such that some of the geometries possessed inhomogeneity of both parameters. Little experimental data exists for such configurations and hence the authors examine these configurations using CFD. The CFD overpressure predictions at various target locations for 400 scenarios are compared with the results from a newly derived correlation and the correlation of the guidance for the application of the multi-energy method (GAME). It is found that the overpressure predictions obtained using the correlation still better agrees with the CFD modeling results compared with the GAME correlation suggesting. To show the importance of increased accuracy in these cases, a structural damage level evaluation process is used to place the damage levels for four monitor points on a $p\text{-}i$ curve, and the results show that often these damage levels are near critical, demonstrating the need for improved accuracy.

This paper investigates the influence of unreinforced masonry panels on the robustness of multistory buildings under sudden column loss scenarios. A recently developed multilevel framework is employed to evaluate the resistance to progressive collapse under such scenarios, which is applied in this paper at story level allowing for the resistance of the floor system and the infill panels. The response of various structural components under pushdown deformation is obtained using high-fidelity finite-element analysis, where an accurate mesoscale description is utilized for the masonry infill, elastoplastic beam-column elements are used for the floor system, and component-based nonlinear mechanical models are employed for the joints. This methodology is applied to a 7-story composite steel-concrete benchmark building, where it is established that the use of masonry infill panels for exterior cladding can considerably increase progressive collapse resistance, even in the case of perforated walls. Furthermore, the results indicate that the maximum dynamic deformations under sudden column loss are relatively small due to the significant resistance of the infill, which is particularly relevant when considering the retrofitting of structures affected by column loss.

Disproportionate collapse of structures can lead to catastrophic economic loss and casualties, and thus, it is of utmost concern to mitigate the risks of such events. Flat-slab structures are much more vulnerable to disproportionate collapse than moment-frame structures as there are no beams to redistribute the loads initially resisted by the lost column. Moreover, the propagation of punching-shear failure at slab–column connections due to load redistribution may result in the collapse of the entire slab. Thus, increased attentions should be paid toward assessing the disproportionate collapse performance of flat-slab structures. However, to date, limited knowledge exists regarding the risks of disproportionate collapse in flat-slab structures, especially in terms of dynamic tests. For this purpose, a series of one-third-scaled flat-slab substructures were subjected to the simulated sudden-column-removal scenario and the failure mode, acceleration, and displacement responses were presented and discussed. To attain a deeper understanding of the dynamic load–redistribution capacity of flat-slab structures, numerical and parametric analyses were also carried out. The possible load-resisting mechanism (membrane action, postpunching behavior, and flexural strength) of flat-slab structures to mitigate disproportionate collapse is also discussed.

Innovations in the U.S. construction and precast concrete manufacturing industries have resulted in efficient methods of constructing multistory buildings that are entirely supported by precast concrete walls (i.e., no structural frame). Simultaneously, the U.S. government has mandated overarching requirements and incentives that promote energy efficiency in all government buildings and facilities. The combination of construction efficiencies and relatively recent requirements for improving energy efficiency makes total precast construction an attractive option for constructing government, diplomatic and U.S. Department of Defense (DoD) buildings and facilities. However, to design load bearing wall panels for DoD blast response criteria, engineers need a relatively simple method for analyzing dynamic response under combined lateral and axial load effects. This paper presents methods for incorporating the P-delta and P-M interaction effects into the single-degree-of-freedom (SDOF) framework that is widely used for blast analysis and design, and evaluates the developed methods using high-fidelity nonlinear static and explicit nonlinear dynamic finite element models of load-bearing precast panels. The work demonstrates that currently used methods that do not properly consider the effects of axial loads on resistance may be grossly over conservative, and demonstrates that the easily-implemented methods developed through this research provide accurate results.

Given the catastrophic consequences following progressive collapse, designs to mitigate such events are of great interest to both the academic and engineering communities. This has led to the development of numerous design guidelines across the world to facilitate such efforts. Many authoritative papers were prepared, especially in the past decade, to evaluate the reliability of existing design methods for progressive collapse assessment. The deficiencies in existing guidelines on critical issues, such as dynamic effects, tie force and integrity approaches, slab effects, and acceptance criteria, are addressed based on the findings from some significant technical papers. Recommendations are included to identify the current concerns on developing existing design guidelines and also present a state-of-the-art review of the proposed refinements. Potential areas for future research are also explored.

This paper examines the deflected shape assumptions built into the single-degree-of-freedom (SDOF) methodology used for analyzing structural components subject to blast loading. Design professionals use the SDOF models to analyze blast effects on components. It is common knowledge that the SDOF method is an approximation, and is not suitable for large charges with short distances (lower scaled distance $-Z$). Current design guidelines establish the limit of $Z=1.2\mathrm{m}/{\mathrm{kg}}^{1/3}$ for using SDOF methodologies for blast-loaded components, which is equivalent to a peak pressure of 5,000 kPa; however, this paper shows that the limit may be significantly higher in $Z$ value (or lower in peak pressure). Higher air-blast pressure and impulse combinations cause hinges to form before the assumed deflected shape dominates the response. Because transformation factors for SDOF are derived using static deflected shapes and the static collapse mechanism, the factors may not produce accurate or conservative responses for blast loading at lower scaled distances. Using the finite element multi-degree-of-freedom (FE-MDOF) model, the paper validates the accuracy of SDOF shape factors for large scaled distances, and shows that the static deflected shape assumptions do not apply at lower scaled distances with higher impulses. Limits to SDOF are established based on the equivalent shape factors, and the variability in the limits based on damping and mass are also discussed.

Most vulnerability assessments assume that an improvised explosive device (IED) will reach maximum TNT equivalency, and that the IED will successfully detonate. These assumptions will tend to overestimate actual blast-load effects. The paper develops an IED probabilistic risk-assessment model using a systems model for IED attacks based on the reliability of IEDs and by characterizing the human aspects of an IED attack’s operational effectiveness from existing databases of terrorist incidents. The analysis includes estimates of the probability of threat, hazard, and loss for large commercial buildings in the United States. It was found that annual fatality risk for building occupants is similar to acceptable risk criteria. This suggests that strengthening buildings against progressive collapse may not be warranted unless there is a specific threat against a building.

Reliability-based design allows the decision maker to select the level of reliability for a specific blast loading scenario and key to this is an understanding of airblast uncertainty. Hence, explosive field trials have been conducted in Australia that measured the variability of free-field blast loading caused by military standard plastic explosives. The results have revealed a high level of variability of peak incident pressure, impulse, and time of positive phase duration for repeatable tests where variability would be expected to be a minimum. The accuracy of predictive blast load models (model error) was also assessed. A probabilistic blast load computer model is revised to capture these observed variabilities. The effect of a 20% mass-increase safety factor typically applied to explosive mass on the probability of exceeding a design blast load is assessed. Reliability-based load factors are calculated where the nominal load is multiplied by the load factor to ensure that the actual load is equal to the reliability level. Reliability-based load factors are estimated for reliability levels of 0.05–0.99, for a range of scaled distances for military munitions. The load factor can be as low as 0.66 for a 0.05 reliability level and as high as 1.30 for a 0.99 reliability level.

A general reflection coefficient (GRC) is defined to determine the equivalent uniform stress on an underground arched structure subjected to a subsurface explosion. The single-degree-of-freedom model approach is adopted and the structure–medium interaction and curvature effect are considered. The derivation lies on a virtual work method, which provides the GRC of the buried arch-shaped underground structure. The GRC is also suitable for box-shaped underground structures when the curvature of the arch tends to be zero. Case studies are discussed to investigate the effect of dimensionless parameters. The developed method is applied to a practical example. It is shown that the present approach is effective and applicable for practical use designing buried underground structures subjected to subsurface explosions. It also complements the current design codes, which lack details for designing arch-shaped buried protective structures.

Concrete-filled double-skin tubes (CFDST) have been widely used in constructing high-rise buildings, arch bridges, and factories over the past years. Although a number of researches have been conducted to study the behavior of CFDST columns under a variety of loading conditions, their performance when subjected to lateral impact load is still lacking. In this paper, numerical models of CFDST columns with two different cross sections are developed: one is with a CHS (circular hollow section) outer and CHS (circular hollow section) inner, and the other one is with SHS (square hollow section) outer and SHS (square hollow section) inner. Conventional concrete is filled in double-skin steel tubes. Different blast loads are applied to the surface of these columns for dynamic analysis. In addition, different axial loads are also applied to simulate combined load conditions. The displacement-time history obtained from each simulation is recorded and then compared. The key parameters that affect the performance of CFDST columns under blast load are also investigated.

Blast loads acting on structural components under close-in explosions are nonuniform; therefore, the damage to structural members under such blast loads is local and the failure mechanism is more complex as compared with that of distance explosions. Because of the lack of an accurate blast load model, a precise damage analysis method, an efficient damage assessment method, and practical protective measures, the blast-resistant design of structural members under close-in explosions faces great challenges. In this paper, a fluid-solid coupling numerical method is proposed and then used to investigate the failure mechanism of reinforced concrete (RC) columns under close-in explosions. The results show that local failure, such as crushing, cratering, and spall of concrete, is more likely to happen when the RC column is subjected to close-in blast loads. Parametric studies are carried out to investigate the influences of column dimensions and the reinforcement ratio on the damage degree of RC columns. Based on the numerical results, a rapid damage assessment method is also proposed and validated in this paper. The results show that the proposed method can efficiently evaluate the damage degree of RC columns and can be used in the blast-resistant design of RC columns to protect against close-in explosions.

Methods for the assessment of structural designs or existing structural systems for susceptibility to disproportionate (progressive) collapse and prescriptive methods intended to mitigate or decrease the likelihood of progressive (disproportionate) collapse are approaching adolescence as compared to the age and maturity of other engineering design standards and approaches. U.S., British, and Eurocode standards such as ASCE–7, BS EN 1991–1–7, 2006, and Eurocode 1: Actions on structures first established design philosophies and some prescriptive approaches, while later U.S. guidelines and IBC code provisions have attempted to fill in the gaps with refined prescriptive methods or detailed static and dynamic analysis approaches. The U.S. Department of Defense (DoD) and the U.S. General Services Administration (GSA) have published design and analysis guidelines in recent years. The DoD guidelines have been updated three times since inception, and GSA guidance is currently being updated to take advantage of the DoD improvements through adaptation of DoD methods within GSA applicability requirements. Additionally, the Structural Engineering Institute (SEI) in the United States has focused on the efforts of several technical experts within their Disproportionate Collapse Mitigation Standards Committee. This paper provides updates on the steadily converging approaches and documents. Specifics of analysis approach updates as well as design philosophy and applicability direction are presented and discussed.

Condition-ratings in bridges have been used by the Federal Highway Administration as a way to classify structural deficiencies and structures that are functionally obsolete. These ratings are determined by evaluating the severity of the deterioration or nonconforming issues in affected bridges. The quality of the condition-rating practice is subjective (visual inspection based on the inspector’s view) and time delayed due to inspection cycles, which are scheduled for every two years. However, some deterioration may not be visible to the inspector. For instance, concrete substructures exposed to deicing salts or those in marine environments may begin experiencing deterioration or corrosion without showing any external damage. In addition, once a concrete substructure begins to experience these types of defects, the substructure’s durability becomes compromised. Consequently, it is important to evaluate damaged substructures and analyze the severity of the substructure’s degradation, the decrease in performance over time. This paper uses a risk-based approach (a nondestructive evaluation technique) to calculate and analyze some probabilities of failure associated with degradation factors. Overall, the objective of this research was to develop a generalized procedure, through the integration of deterministic and stochastic durability design methods, which analytically evaluates the durability of deteriorated reinforced concrete (RC) substructures. Furthermore, a decision tree is created to help inspectors exemplify the current condition or remaining strength of concrete substructures that have experienced degradation.

The population and economy in the State of Qatar have been increasing in the past 5 years. Accordingly, traffic loading has also increased rapidly, which affected the performance of existing roads and highways. This high traffic loading merits consideration of the design and construction of long-lasting pavements that require minimal maintenance. The Transport Research Laboratory (TRL) in collaboration with the Public Works Authority (PWA) of Qatar constructed a field experiment that consisted of six different pavement sections in order to investigate the influence of using different materials and asphalt mixture designs on performance. This paper presents a comprehensive study for the field evaluation of the performance of these trial sections. The evaluation involved the use of the falling weight deflectometer (FWD) and a vehicle equipped with instruments for measuring permanent deformation and cracking. These field measurements were complemented with laboratory measurements on field cores: the dynamic modulus, flow number, and semicircular bending tests. The results revealed that the increase in temperature between winter and summer in Qatar reduced the stiffness of asphalt mixtures by about 80%. The sections in which polymer-modified bitumen was used had the lowest temperature susceptibility. Moreover, the results showed that the bitumen and aggregate type significantly affected the stiffness and the trial sections’ resistance to rutting and fracture.

The objectives of this study are to determine the short-term performance for shallowly buried [2,438 mm (up to 8-ft burial depth)] flexible pipes, evaluate joint performance requirements, and verify AASHTO design assumptions in the light of field test data from in situ measurements. The installation, instrumentation, and field test procedures are presented for high-density polyethylene (HDPE), PVC, and metal pipes under 2D, 1D, and 0.5D burial depths, where D is the pipe diameter. The field test is performed on 914 mm (36 in.) and 1,219 mm (48 in.) pipe diameters. A tandem dump truck is selected for the pipes under 2D burial depth, while the Florida Department of Transportation truck is adopted for the pipes under 0.5D and 1D burial depths. The field test results are presented in terms of the soil pressure distribution around the cross section, as well as the vertical and horizontal pipe diameter changes during construction and under the live load. Special emphasis is given to circumferential wall strains. The validity of the modified Iowa and Meyerhof formulae proposed to predict the horizontal deflection of buried pipes is also investigated.

On October 23, 2011, an earthquake ($M_w=7.2$) hit the eastern province of Van, Turkey, at local time 13.41 (GMT 10.41). According to records, this was the biggest earthquake after the one in Kocaeli, Marmara, on August 17, 1999, The Van earthquake claimed 604 lives near the epicenter and caused extensive structural damage. Recorded ground accelerations were surprisingly low compared to the structural damage observed within the region and recent Turkish earthquakes. Its peak value was approximately $1.78\mathrm{m}/{\mathrm{sn}}^2$. The objective of this article is to examine the existing reasons for damages to reinforced-concrete and masonry buildings. Additionally, general characteristics of the Van earthquake, seismo-tectonic characteristics of the region, and evaluation of peak acceleration value are presented. All factors that caused damage and collapse are presented as sections, and the observations are compared to the Turkish Earthquake Code and Turkish Building Code terms.

This paper presents the investigations carried out on the backbone curves of reinforced concrete (RC) columns with light transverse reinforcement. An experimental program consisting of five half-scale RC columns with light transverse reinforcement was carried out. The specimens are tested to the point of axial failure to obtain the backbone curves of such columns. Quasi-static cyclic loading simulating earthquake actions is applied. The backbone curves obtained from the tested specimens are then compared with the existing seismic assessment guidelines. The test results indicate that the initial column stiffness and ultimate displacements (displacements at axial failure) are overestimated and underestimated by some guidelines and provisions. The existing initial stiffness and ultimate displacement models are briefly reviewed and compared with the experimental results. The results show that the existing initial stiffness and ultimate displacement models produced better results than the existing seismic assessment guidelines.

Different in situ and laboratory tests are commonly used to determine the nature of salts and to improve the comprehension of degradation mechanisms. Although laboratory tests are more accurate, in situ tests yield faster results and require a significantly lower budget. This study aimed at collecting data on nine case studies of buildings (26 sample’s analysis) showing salt induced damage and assessing the potential of diagnosis techniques. Two in situ (test strips and a spectrophotometer-field kit) and three laboratory techniques [X-ray diffraction (XRD), X-ray fluorescence (XRF) and infrared spectroscopy (FTIR)] were carried out. The results showed the importance of collecting samples from different materials and locations. It is concluded that the combination of a thorough description of the areas affected by salt damage, a survey of the building’s history, the consideration of its surrounding environmental conditions, and simple in situ tests is a useful and straightforward diagnostic tool. Although results of in situ tests agreed with the global results from the set of laboratory analyses, no single analytical method was considered sufficient to accurately identify all the damaging salts in a sample because each one showed intrinsic limitations.

In 2007, the Portuguese government launched a modernization program for the public network of secondary schools. This comprised a comprehensive survey on 56 large secondary schools aiming at identifying the main building anomalies to be considered in the rehabilitation projects. Based on this survey, this paper presents the building characterization and the analysis of the degradation patterns of 15 Portuguese secondary industrial schools, a particular and homogeneous typology of secondary schools. A set of information about each school was collected first, gathering, among other elements the (1) identification of the anomaly, (2) building element affected and its location in the building, (3) extent and severity level of the anomaly, (4) causes, and (5) repair solutions. From the resulting database, the degradation condition of these schools was assessed in terms of the (1) most frequent degradation occurrences, (2) influence of the relative location of building elements (envelope versus interior), (3) influence of the type of building, and (4) maintenance and rehabilitation recommendations. The results presented in this paper show that the overall condition of the schools analysed is reasonable to good, particularly taking into account their age (42–61 years old); a relatively small number of critical situations was detected, most of which were localized. This paper also shows that in most situations the two main types of anomalies detected, i.e., (1) structural, and (2) moisture-related, could have been avoided if properly addressed during the design and construction stages. Several situations stem also from lack of maintenance, which in some cases was hindered by difficult access to the construction elements.

This paper presents the findings from both the detailed site investigations and the computational analyses on the Zipingpu concrete-faced rockfill dam (CFRD), a 156-m high dam in which 100-cm permanent settlement and 60-cm horizontal displacement occurred during the 2008 Wenchuan, China, earthquake. The Zipingpu CFRD was 17 km away from the epicenter and was considerably damaged by the Wenchuan earthquake. It was estimated that the peak acceleration in the top of the dam along the axial and vertical direction was about $20.0\mathrm{m}/{\mathrm{s}}^2$, and the peak acceleration at the river level was about $16.0\mathrm{m}/{\mathrm{s}}^2$. It was calculated that peak acceleration of dam bedrock was more than $5.0\mathrm{m}/{\mathrm{s}}^2$, and the intensity (Chinese scale) was more than IX. Based on an in-situ investigation, the peak value of settlement of the dam crest reached 744.3 mm, and the peak value of horizontal displacement toward the right and left abutment are 226.1 mm and 106.8 mm, respectively. The actual experience of the peak acceleration and seismic intensity of the Zipingpu CFRD in this earthquake was considerably beyond criteria used for the original design standards. To simulate the seismic activity and damage, a three-dimensional (3D) numerical model of the Zipingpu CFRD is established and the numerical simulation analysis of Wenchuan earthquake damage is presented. The calculated results show that the numerical analyses are consistent with the in-situ investigation. The seismic performance of the Zipingpu CFRD during the Wenchuan earthquake is reproduced in the numerical model. The acceleration response, permanent deformation, and damage characteristics of the Zipingpu CFRD in the Wenchuan earthquake are understood as a result of this study. It should also be highlighted that the valuable and rare data from the seismic response of such a large dam will be useful for further case studies.

This study presents the experimental results for seven different tests carried out on high-density polyethylene (HDPE), PVC, and metal pipes with medium-size diameters. The main objective of the experimental program is to evaluate and characterize, under laboratory conditions, the performance and mechanical properties of the various flexible pipes considered in the study. The diameters of the pipes studied are 36 in. (914 mm) and 48 in. (1,219 mm). The laboratory tests conducted are the simple-beam test, parallel-plate test, flattening test, curved-beam test, joint-integrity test, and tensile test, as well as an environmental stress-cracking test. The results of the tests are presented in terms of load-deflection relations, load versus longitudinal and transverse strains, failure modes, and pipe stiffness. The test results indicate that HDPE and PVC pipes show good performance compared with metal pipes. In addition, the experimental results for flexible pipes meet AASHTO specifications. The HDPE and PVC pipes tested according to the ASTM and AASHTO Standards show pipe stiffness values higher than the minimum specified by the standards. The pipe stiffness values of the HDPE specimens based on the curved-beam test are two to three times greater than those based on the parallel-plate test. It was found that for a given vertical deflection, the HDPE pipe stiffness substantially increased with an increase of loading rate.

The facilities management industry is growing fast due to the increasing importance of quality, value for money, and effective utilization of the workplace. However, the implementation and development of facilities management in Malaysia has been relatively slow due to a lack of understanding and education. The aim of this study is to identify the perception of user requirements toward building facilities in the University of Malaya research and development building known as Wisma R&D. A questionnaire survey was used to collect data from the respondents. This study finds that the building users were satisfied with the performance requirement and facilities in the building. Statistically it shows that the 26 building performance requirements have a significant relationship with building user overall satisfaction. It is generally hoped that this study benefits the parties who are involved in the building construction industry, namely designers, engineers, developers, and facility managers.

The purpose of this paper is to study the dynamic behavior of a pedestrian bridge in Alicante, Spain, which showed vertical and horizontal vibration problems. Moreover, the deck’s structural steel showed severe corrosion damage. Hence, two cases were analyzed: before retrofitting the structure using glass fiber-reinforced polymers (GFRPs) and after. While the GFRP was designed for aesthetic and durability purposes only—and not for structural retrofitting—it changed the mass and stiffness of the footbridge, affecting its dynamic characteristics. The natural frequencies, mode shapes, and modal damping factors of the bridge were calculated based on accelerations recorded at 11 points on the bridge under different conditions—i.e., ambient vibration and forced vibration produced by a fixed number of pedestrians walking on the bridge at a certain speed and frequency. A numerical model was also designed in order to compare the experimental and numerical results.

The objective of this study is to investigate the effects of a new type of infill—called locked brick infill adopting horizontal sliding joints—in reducing the soft-story formation in reinforced concrete (RC) frames with code-conforming seismic detailing. Nonlinear static time-history analyses were performed on multistory planar frames with only the upper stories infilled in order to force the soft-story irregularity. The parameters of frame and infill elements that were used in numerical simulations were obtained from half-scale RC infilled frame tests that had been performed by the author covering single story–single bay frames infilled with standard and locked bricks. The numerical simulations showed that the use of locked bricks to form infill walls has the potential to decrease the soft-story/weak-story formation in comparison to standard bricks due to its shear sliding mechanism and decreased upper-story/first-story stiffness, even in buildings that have noninfilled first stories.

Prestressed concrete sleepers (or railroad ties) are designed to carry and transfer the wheel loads from the rails to the track foundation. Over a period of time, a railway track could experience various types of static and dynamic loading conditions, which are attributable to commercial train operations. Previous studies have established two main limit states for the design consideration of concrete sleepers: ultimate limit states under extreme impact and fatigue limit states under repeated probabilistic impact loads. Prestressed concrete has played a significant role in maintaining the high endurance of the sleepers under low to moderate repeated impact loads. Despite the most common use of the prestressed concrete sleepers in railway tracks, their remaining lives are not deeply appreciated nor taken into account for track maintenance and renewal. The present experimental investigation was aimed at determining the residual prestressing force of railway concrete sleepers after revenue services using the dynamic relaxation technique. Fifteen sleepers were extracted from a heavy-haul rail network for testing using experimental facilities at the University of Wollongong in Australia. The structural evaluation program included quasi-static bending tests, dynamic impact tests, and tests to establish the current level of prestress in the steel wires using the dynamic relaxation technique. Two of the sleepers were evaluated for the level of prestressing forces in accordance with Australian standards. It was found that the level of prestress determined using the dynamic relaxation technique was significantly lower than that expected from the theoretical analysis of time-dependent prestressing losses for the concrete sleepers.

Recent major earthquakes in the Italian territory have reaffirmed the seismic vulnerability of precast industrial buildings typical of past Italian building practices, highlighting structural deficiencies observed during previous events and primarily related to the transfer of horizontal forces between structural and nonstructural elements. An intrinsic lack of shear and ductility capacity has been observed in simply supported beam-to-joist and beam-to-column connections, primarily constituted by vertical steel dowels or solely relying on shear friction, with or without neoprene pads. These connections were designed neglecting seismic loads and their premature failure was observed during recent seismic events to cause a loss of support of beam elements, owing to the relative movements of elements, and the collapse of part of the buildings, primarily the roof. The seismic displacement demand of the industrial buildings under consideration is larger than traditional RC frame structures owing to their higher flexibility, according to both higher interstory height and to a cantilevered static scheme. Furthermore, this high flexibility may also result in displacement incompatibility between structural and nonstructural elements, such as precast cladding panels, causing their connection failure. On the basis of detailed field observations on a relevant number of buildings, collected just after the earthquakes, seven representative industrial facilities are examined to outline the primary vulnerabilities of one-story precast concrete structures not designed and detailed for seismic loads.

This article discusses the use of nondestructive and subsequent laboratory materials testing techniques in evaluation of extent of fire damage to a precast prestressed parking structure. The nondestructive and laboratory testing findings were used in determination of extent of fire damage to concrete and potential effects on the prestressing tendons. The in-situ nondestructive testing phase consisted of scanning affected areas using ultrasonic pulse velocity through concrete members and use of impact echo on a confirmatory limited basis. Subsequently, cores were removed and tested for resonant frequency-based dynamic modulus in accordance with ASTM C 215. Upon determination of dynamic elastic modulus of the entire core per ASTM C 215, the cores were sawn into 25-mm (1-in.) disks. Young’s modulus of individual disks was determined by utilizing nondestructive measurement of resonant frequency. Determination of Young’s modulus at small depth increments permitted assessment of the heat-induced damage gradient into the concrete and more importantly at the level of the prestressing tendons. The data from multiple techniques provided a means of comparison between constrained in-situ ASTM C 597 pulse velocity to unconstrained compression wave velocity obtained from ASTM C 1383, and an estimated unconstrained compression wave velocity based on dynamic modulus based on disks. The results of these comparisons should be of value to practicing engineers utilizing these techniques in forensic evaluations.

Field observations following the May 2012 Emilia, Italy, earthquakes have revealed the seismic vulnerability of storage steel tanks typical of the past Italian design practice, highlighting structural deficiencies observed during previous events in other areas and mostly related to lack of structural seismic design and detailing, lack of redundancy, and inadequate anchorage design and execution. Damage was disproportionately high, considering the moderate size of the events ($M_W=6.11$ and $M_W=5.96$ on 20th and 29th May, respectively). Failure modes observed are reported and classified. Comparison is provided with the results of high-definition finite element (FE) dynamic simulations, performed on tanks representative of those inspected. Numerical analyses, accounting for material and geometrical nonlinearities, at the element level, as well as for fluid-structure interaction through highly nonlinear methods, were able to capture the stress/strain concentrations that caused them to collapse. Elephant’s foot and diamond buckling induced by hydrodynamic pressures as a result of inertial forces imparted during the earthquakes were reproduced, as well as shear-buckling failure of leg-supported tanks or sliding of unanchored systems.

This paper presents the results of a comparative study of biological damage to wooden structural elements of truss structures in a group of typologically similar buildings: small-sized and medium-sized baroque churches in the Czech Republic. Within the study, the data on the genus composition of wood-damaging fungi, locations where they were identified, and their activities are reported. The data were obtained during structural and mycological surveys of the condition of wooden structural elements carried out, in most cases, before planned reconstructions of their roof structures. The data on the genus composition of wood-damaging fungi were obtained either directly in the structures—based on the evaluation of macroscopic indications of biological damage—or in the laboratory by means of cultivation and microscopic analyses of wood samples. The result, in terms of biological damage, is the ascertainment of the genus composition of wood-damaging fungi active at typical high-risk locations of typologically similar truss structures.

A number of steel girder-RC bridges built in the past have noncomposite bridge decks. Many currently have load postings because of increased traffic loads. The main objective of this case study was the performance evaluation of a single span steel girder bridge with a noncomposite RC deck before and after strengthening using postinstalled shear studs and ultra high modulus (UHM) carbon-fiber-reinforced polymer (CFRP) laminates. The postinstalled shear studs were used to obtain a partial composite action between the concrete deck and steel girders to increase the load-carrying capacity and utilize the UHM CFRP laminates more efficiently. An AASHTO load-rating analysis carried out for an interior girder under an HS25 truck load showed an inventory level rating factor of 0.46 for the noncomposite bridge. Field tests were conducted before and after the installation of the shear studs and UHM CFRP laminates to determine the increase in the load-carrying capacity and reduction in maximum deflection. A finite-element model of the bridge was developed to validate the experimental data and analyze the bridge under varying wheel loads. Postinstalled shear studs are found to be capable of significantly increasing the load-carrying capacity of noncomposite bridges. The use of UHM CFRP laminates strengthened the steel bridge girders, reduced overall deflections, and increased the load-carrying capacity. The postinstalled shear studs and UHM CFRP laminates increased the load rating and removed the load posting on the bridge.

For steel-framed structural systems, strength and deflections have been the two fundamental limit states for the design. However, the use of high-strength steel, lighter sections, and low inherent damping resulted in more lively structures, and floor vibration serviceability has become a governing factor for structural design. While annoying floor vibrations can be significant in open web steel joist-supported footbridges; a common application in the North American construction industry is the installation of bottom chord extensions in an attempt to strengthen the floor and increase the natural frequency of the floor systems. Even though extending joist bottom chords is very common, there has not been any publication on the topic studying the dynamic effects of this application. The study presented in this paper aims to fill this gap and identify the effect of bottom chord extensions on the modal parameters of joist-supported structures, by studying two laboratory footbridges. The goal is not to solve a potential vibration problem of a footbridge but to identify the modal parameter variations due to bottom chord extension installations. Extensive experimental and analytical studies were conducted on single-span and three-span joist-supported laboratory footbridges with different bottom chord extension configurations. Three-dimensional finite-element computer models were created to simulate and compare the results of stiffness and dynamic tests with the philosophy of testing the footbridges and updating the finite-element models, thus minimizing the discrepancies between the test results and the finite-element models for better prediction. Results from the static and dynamic tests on the single-span and three-span footbridges indicate that installing the bottom chord extensions to the joists increases the natural frequencies of the flexural stiffness and flexural bending. Considering the low cost, and quick and easy application at the construction site, extending bottom chords can be considered as an option to reduce the deflections and increase the governing bending mode natural frequencies of footbridges. While bottom chord extensions do not guarantee that the vibration problem (if any) would be solved, with the higher natural frequencies, the footbridges are relatively less vulnerable to be put in resonance by human induced excitations. As a result, extending bottom chord extensions is an advantage; however, the acceleration response of the footbridges needs to be checked separately, for conformance with the code limits.

Low-rise concrete and masonry structures can provide excellent seismic resistance when they are designed by an engineer, are made of quality materials, and are built by well-trained workers in conformance with building codes. Unfortunately, this is not the way many of the structures are being built in developing regions. Property owners themselves are building low-rise nonengineered structures, paying little attention to building codes or seismic resistance. Adding to the problem, when building with concrete and masonry construction, it is possible to have relatively long spans, large openings, and irregular shapes, all of which impact their earthquake performance. These nonengineered buildings are deceptive because they seem safe, they perform well under gravity loads, and they do not sag or lean. In this study, several typical concrete and masonry low-rise residential buildings were modeled and subjected to seismic loads. These models were then manipulated to determine which low-cost changes will have the greatest effect on earthquake performance.

The Taiwanese population continues to grow despite a decreasing useable land area. Natural disasters, such as earthquakes, typhoons, and floods, can happen throughout the year. Such disasters often result in loss of life and property damage. Hazard mitigation and prevention research is extremely important. This paper describes the recovery plans and emergency grouting performed on Shih-Kang Dam after the 921 earthquake. This information can be used by engineers to improve the efficiency of crisis treatments using emergency grouting.

Residential shelter performance, in the aftermath of the devastating May 20, 2013, EF5 tornado that struck Moore, Oklahoma, was investigated by a reconnaissance team comprised of researchers from several universities. The team observed and documented 75 residential shelters along the tornado damage path and noted that the concept of shared shelter use was responsible for saving many lives. All belowground shelters performed well with no evidence of structural compromise or shelter breach from debris missiles; however, debris was occasionally observed blocking the opening of the garage slab residential shelters and flooding was also noted in a few cases. Although less common, the majority of above ground residential shelters observed were found in areas that experienced EF3–EF4 estimated wind speeds. In all cases but one, the above ground safe rooms performed well. A debris missile breach of an insulated concrete form (ICF) safe room was documented. While poor construction quality, specifically poor concrete consolidation in areas where plastic cross-ties held the form together, was found to be the major contributing factor in this failure, other factors such as safe room placement within the house and the type of missile (thin-walled steel square tubing) also contributed to this failure.