Journal of Structural Engineering

This paper presents the results of an experimental program conducted to evaluate the local damage behavior of steel-plate composite (SC) walls subjected to missile impact. There is significant interest in the use of SC walls for protective structures particularly to resist impactive and impulsive loading. The behavior of SC walls subjected to these loads differs from that of reinforced concrete (RC) walls due to the placement of steel plates on the surfaces, which prevents concrete scabbing and enhances local perforation resistance. The results from the experimental program are used to demonstrate and explain progression of damage modes leading to local perforation, and to validate and quantify the conservatism of a recently developed design method. Laboratory-scale SC wall specimens were fabricated and tested in an indoor missile impact facility specially built and commissioned for this research. Sixteen tests were conducted with varied parameters: the steel plate reinforcement ratio ($\rho :3.7\%–5.2\%$); tie bar spacing, size, and reinforcement ratio (${\rho }_t:0.37\%–1.23\%$); steel plate yield stress ($f_y^{nom}:\mathrm{Gr}·50–\mathrm{Gr}·65$); and missile diameter ($D_m:25.4$, 38.1 mm), weight ($W_m:0.59$, 0.91, 1.59 kg), and velocity ($V_m:125–232\mathrm{m}/\mathrm{s}$). Experimental results include the measured missile velocity, penetration depth, rear steel plate bulging deformation, and test outcome (stopped or perforated). The observations of behavior and progression of damage (missile penetration and local perforation) are used to quantify and explain the sources of conservatism in the design method, which include the dimensions of the concrete conical frustum (breaking out) and the assumed penetration depth equations.

Large-scale reinforced concrete columns with high-strength reinforcement and concrete were tested. The nominal compressive strength of concrete was 70 MPa. The nominal yield strengths of longitudinal and shear reinforcement were 690 and 790 MPa, respectively. The columns were subjected to double-curvature lateral cyclic loading under constant axial compression. Test variables included the amount of shear reinforcement and level of axial compression. Test results showed that all the nine columns tested failed in shear and showed a successful redistribution of internal forces at diagonal cracking. The stress of shear reinforcement at the peak load increased with an increasing amount of shear reinforcement. Three of four columns with the highest amount of shear reinforcement (0.56%) showed yielding of shear reinforcement at the peak load. By comparing with the test results of 86 high-strength columns from this research and the literature, the minimum shear reinforcement equation of the ACI 318 code was found not able to prevent failure at diagonal cracking and failed to provide a clear trend between the reserve shear strength and the amount of shear reinforcement. A minimum shear reinforcement equation is thus proposed. The equation is based on the $V_c$ equation of the ACI 318 code and can consider the effect of axial compression. Comparing 86 columns shows that the columns that failed at diagonal cracking do not satisfy the proposed equation. Moreover, the proposed equation can provide a clear trend between the reserve shear strength and the amount of shear reinforcement.

To assess the time-variant performance of RC structures, it is important to model the various deterioration processes as well as their interactions in addition to the associated uncertainties. Besides earthquakes and corrosion, RC structures can also be subject to deterioration due to alkali-silica reaction (ASR), which could impact the corrosion process. This paper develops a novel deterioration model for RC structures that captures the joint effects of deterioration due to earthquakes, corrosion, and ASR. The model is constructed using a novel stochastic formulation that captures the interaction of different deterioration mechanisms by modeling deterioration as both age/time and state dependent. The developed deterioration model is then used to estimate the time-variant seismic fragility and reliability of an example RC bridge. The impacts of interactions between deterioration processes on the time-variant performance are investigated in detail under different earthquake occurrence rates, different levels of ASR, and different levels of interactions. The results highlight the importance of incorporating different deterioration processes and their interactions when estimating the time-variant performances of RC structures.

Combined loading of blast and fragments involves various loading mechanisms on a structural element. It includes the momentum inflicted by the blast load and the penetration of the fragments, as well as the structural damage due to fragment penetrations. A model to account for the fragmentation loading in a realistic, yet simplified approach was suggested and validated in previous experimental and analytical studies. However, the dynamic response of a structural element subjected to combined loading considering a nonuniform fragmentation distribution has not been studied. A finite-difference model is presented in this paper to solve the dynamic response of a one-way reinforced concrete (RC) element. The simplified method to consider the strain-rate effects in the section (macro) level is proposed. It is based on static analyses of the section at different loading rates, thus making the dynamic solution relatively quick. The model is validated with analytical and experimental data that included blast loads. The finite-difference model is used to simulate the response of a RC element to combined loading. Three design approaches, one of which neglects the fragmentation on the one hand and on the other hand considers a higher magnitude of blast load, are studied. It was shown that for the presented case studies, the fragmentation must be considered for a more realistic prediction of the structural response. For short standoffs, a nonuniform fragmentation distribution should be considered to get more realistic predictions, whereas for larger standoffs, a uniform fragment distribution can be assumed. In both standoff ranges, a design approach that is commonly used, in which the fragmentation effect is neglected, leads to less conservative results.

Cold-formed steel (CFS) framed construction has been widely adopted and used toward a modern, lightweight, and cost-efficient engineering practice across the United States. The primary objective of this work is to numerically assess the performance of CFS-framed shear walls sheathed with oriented strand board (OSB) and subjected to seismic events. A robust three-dimensional high-fidelity shell finite element model is developed and aims to provide a benchmark modeling approach able to accurately capture strength, stiffness, and failure mechanisms in these systems. Particular attention is given to the fundamental role of the connections between the CFS members and the OSB sheathing to the overall shear wall lateral response. To understand the variability in this critical connection, a series of 30 identical connection tests are performed. The robustness of the proposed computational model is validated by nine different CFS shear wall experimental studies and by a parametric analysis. The developed model is applied to provide an accurate experimentally-derived fastener-based computational tool of CFS-framed shear walls with potential use in design code expansion.

This paper presents key findings of an experimental program performed to examine the rate-dependent behavior of weld material in transverse welded lap joints at elevated temperatures under steady-state thermal conditions. The data are intended to support the development of models of welded connections for structural-fire engineering applications. Two different loading rate scenarios (fast and slow) were incorporated in the experiments to evaluate the loading rate effect on the strength and deformation capacity of welded connection test specimens at ambient and elevated temperatures. Retention factors for the weld material under both slow and fast loading rates were computed and compared with those available in the literature. Results from this study indicate that the loading rate has a significant effect on the strength and deformation capacities of transverse welded lap joints for temperatures greater than 450°C.

Roof collapses due to ponding instability are among the most frequent structural failures. Although methods of design for other types of instability have evolved and improved with computational advances, the most commonly used method of assessing ponding instability has been updated minimally since it was developed over 50 years ago. Newer methods of design for ponding have been proposed, but they lack independent verification of their ability to assess the strength of roofs and to provide a sufficient level of reliability. An advanced analysis approach capable of capturing material and geometric nonlinearity, as well as accumulation of water caused by deflection, was developed for roofs consisting of steel beams on stiff supports. The new analysis approach generates data against which the various methods of design for ponding can be benchmarked. These comparisons showed that methods of design based on elastic analysis are capable of accurately capturing the strength of structural steel roofs subjected to ponding load if a reduction factor of 0.8 is applied to the stiffness of the structure. In addition, a reliability analysis using Monte Carlo simulation showed that the methods of design for ponding can achieve a target reliability index consistent with design for other loading conditions. The results provide new insights into the behavior of roofs subjected to ponding loads and enable the use of new design methods for ponding that are more broadly applicable, comprehensive, and consistent with current methods of strength evaluation.

To promote the development of cross-laminated timber (CLT) structures, the Japanese Government Notifications on Structural Design of CLT Buildings (GN 611) was issued in 2016. In GN 611, three types of platform-framing CLT structures were classified in the simple calculation method of Route-1. Compared with a platform-framing structure, which has been clarified in GN 611, a balloon-framing structure is superior in shortening the construction period and reducing the number of CLT panels and metal connectors. To study the seismic properties of balloon-framing CLT structures and develop new structures for a CLT building, four full-scale, 3-story CLT structures were tested under quasi-static cyclic loading: Specimen 1 was a platform-framing structure with narrow wall panels; Specimen 2 was a balloon-framing structure with continuous wall panels; Specimen 3 a was platform-framing structure with wide wall panels; and Specimen 4 was a balloon-framing structure with continuous wall panels and glulam beams. In this study, experiments were conducted, and the seismic performance of the balloon- and platform-framing CLT structures were evaluated and compared. The test results indicated that the seismic properties of Specimens 1, 2, and 3 were similar and that the design method of Specimen 1, as specified in GN 611, was applicable for Specimens 2 and 3. Specimen 4 exhibited higher lateral load resistance than the other three specimens. The performance of Specimen 4 depended on the moment-resisting performance of the glulam beam and CLT wall joint. In this case, the moment-resisting performance obtained through the experiment was significantly higher than the predicted performance.

In this study, the flexural behavior and rotation capacity of welded I-beams made from $690\text{-}\mathrm{MPa}$ high-strength steel were investigated through experimental tests and numerical simulations. In the experimental program, a total of 16 beams with different width-to-thickness ratios and spans were tested to failure under three- and four-point bending. The flexural strength and rotation capacity were studied in the test. Finite-element models with initial geometric imperfections and residual stresses were established and verified by the test results. A series of parametric studies on flange and web slenderness was conducted based on the verified numerical model. Comparisons were made between test results, numerical results, and design calculations obtained from three international design standards to investigate the applicability of the current design methods to high-strength ($690\text{-}\mathrm{MPa}$) steel I-beams.

This paper investigates the elastic lateral-torsional buckling of shear deformable circular arches of monosymmetric steel I-section with in-plane elastic rotational end constraints under a central concentrated radial load. In previous studies of monosymmetric arches reported in the literature, their ends were considered to be fix-ended or pin-ended in the plane of their curvature. In practice, the ends of an arch are not always fix-ended or pin-ended. The ends of an arch may have elastic restraints provided by elastic foundations or other adjacent structural elements. In addition, Timoshenko shear deformations, which are inevitable for arches with small and moderate slenderness ratios, are not considered in previous studies of the topic. The major contributions of this article are the following: (1) accurate strains and deformed curvatures for monosymmetric arches, including shear deformations, are derived using position vector analysis; and (2) in-plane analyses, including the influences of the elastic rotational end restraints, are successfully carried out in two steps to obtain the accurate axial compressive force, bending moment, and shear force distributions for lateral-torsional buckling analysis. The theoretical solutions for the lateral-torsional buckling load are obtained by applying the principle of stationary potential energy together with a Rayleigh-Ritz formulation and validated by ANSYS version 15.0 modeling of the problem.

Ductile concrete materials with randomly oriented fibers have been studied to improve the strength, displacement capacity, and damage tolerance of reinforced concrete structural components in seismic applications. Performance-based earthquake engineering requires numerically efficient models that are capable of estimating the hysteretic behavior, including the strength, stiffness, cyclic degradation behavior, and failure criteria. This paper discusses the development of an experimental database and its use in the calibration of a phenomenological model to simulate the nonlinear behavior of reinforced ductile concrete components under cyclic loading. The modeling parameters are calibrated to predict the initial stiffness, lateral strength, deformation capacity, and cyclic and in-cycle degradation. Backbone parameters were selected using a mechanics-based approach combined with a calibration of hysteretic parameters to match an energy-based damage index. A large-scale experimental database with a variability in material properties, geometry, testing configurations, and fiber types was used for calibration purposes. A forward stepwise regression analysis was conducted to develop an empirical equation for a stiffness reduction factor and a cyclic strength degradation parameter as functions of material behavior and geometry. The modeling strategy is validated by comparing an experimental and simulated cyclic response across a range of metrics. The spring-hinge models are then applied to evaluate the collapse risk of the archetype frame structures using ductile concrete material in the potential plastic hinge region of the beams. The collapse performance is evaluated through an incremental dynamic analysis in which the results of reinforced concrete structures with and without ductile concrete material are compared in terms of the median collapse capacity, fragility curve, mean annual frequency, and sequence of hinge formation in the collapse mechanism. The outcome of this research provides much needed insight into how ductile concrete materials can influence structural system-level seismic performance.

From our investigation of the experimental seismic response of post-and-beam wooden buildings with different column joints, we developed a nonlinear three-dimensional distinct element model that is capable of time-history response analysis. This model succeeded in predicting the seismic response of the column-base, such as rocking behavior, which has been difficult. Four types of full-scale post-and-beam wooden structures with various column-base systems were tested on a shaking table with three ground-motion sequences for each type of structure, and their response and performance were investigated. By comparing the model’s predictions with the test results, we confirmed the rocking–tracking accuracy of the analysis program. The numerical model was reasonably able to keep pace with the measured experimental response in terms of load-deformation curves, following uplifts and pull-out behavior as observed at the column bottoms in the shake-table tests. The model was also able to predict maximum response acceleration and global interstory drift within 10% accuracy on average. Considering the large uncertainties associated with seismic-collapse predictions, such as complicated nonlinear behavior in frames and joints, these results encourage researchers and designers to understand how these structures respond to earthquakes and how to analyze these structures.

A detailed seismic performance assessment for super high-rise buildings is essential for decision-making on postearthquake repair, maintenance, and reoccupation. This paper proposes a probabilistic assessment framework for instrumented super high-rise buildings under bidirectional long-period ground motions in which the probabilities of key structural components experiencing different damage levels are assessed. The fragility curves of the key structural components are obtained by performing a nonlinear incremental dynamic analysis on the building model. The evolving mean values and variances of the structural responses are determined by using the Kalman smoothing algorithm based on the integrated optimal sensor placement and response reconstruction scheme. The extreme value distribution of the structural responses is obtained in terms of the Vanmarcke approximation and then incorporated with generated fragility curves to yield an estimation of the probabilistic damage states of the key structural components. The proposed framework is finally applied to a real super high-rise building, and the results manifest that the proposed framework provides a reliable way of estimating the safety and operability levels of the instrumented building after the earthquake event.

With increasing demand for midrise buildings, automated prefabrication, design for manufacturing and assembly (DfMA), and sustainability, a novel material-efficient post-tensioned (PT) composite steel-timber (CST) stiffened wall system has been developed. As opposed to cross-laminated timber (CLT), this fully prefabricated panelized composite system consists of an engineered wood panel that is integrally stiffened by timber studs and steel square hollow sections (SHS). Each SHS additionally accommodates a PT rod and panel-to-panel connections, allowing for quick onsite assembly, permanent tie-down, and self-centering inverted pendulum rocking. This study presents and evaluates the structural buckling behavior and performance of these systems under vertical axial loading in terms of failure modes, serviceability, ultimate limit states, midheight out-of-plane deflection along the width of the wall, and PT force loss. This has been achieved through an extensive experimental investigation and analysis consisting a total of 10 PT-CST stiffened walls with multiple variables including level of post-tensioning, wall height, end conditions, and the connection between the panel and SHS and the panel and stud stiffeners. Complex behavior through several modes of failure was observed with the increased application of initial PT force, which in turn reduced the ultimate capacity. Additionally, it was found that PT force reduction due to vertical axial loading even within the serviceability limit state (SLS) is significant. Thus, it is recommended that this reduced PT force be considered in design.

Long-span timber floors are susceptible to annoying floor vibrations caused by human activities, which, in many cases, govern the timber floor design. Consequently, a reliable prediction of floor vibration responses under human activities, which relies on appropriate walking load models, can be crucial in the design to keep timber floors remaining competitive in the commercial building market. Much of the current design guidance for timber floor vibrations have been established from short-span floors in a residential context, and as a result, many designers refer to established design methods formulated for use with concrete and steel-framed buildings. These guidelines predict the floor response based on a deterministic single-person walking load model that differs depending on the classification of the floor as either a high- or low-frequency floor, which are assumed as a transient or resonant floor response, respectively. Recent advances in modeling human walking have been made, including a single footfall trace load that avoids the need to classify the floor, as well as load models that incorporate a probabilistic approach. To date, an investigation on different walking load models to predict the vibration response of long-span timber floors has not been undertaken, partially due to the fact that there are limited examples in practice. This paper presents the results of a recently completed state-of-the-art research project involving full-scale testing of long-span timber floors and the development of novel numerical models to investigate the applicability of the deterministic walking load model used in current floor vibration design guides, as well as two innovative single-person walking load models for predicting the floor responses of a single long-span timber cassette floor. The numerical investigation was carried out with a finite-element model calibrated with experimentally obtained modal properties. The comparison between the predicted responses and the measured walking test results leads to the recommendation that a selection of an appropriate load model plays a crucial role in accurately and reliably predicting the floor response of a long-span timber cassette floor. Finally, the research undergirding this paper forms an essential basis for understanding the dynamic behavior of long-span timber floors for use in medium-rise timber buildings.

Due to the similar design process for shear and torsion in RC members, the code limits on maximum yield strength for both shear and torsion are the same. However, the limiting values differ among different codes. For example, some codes limit the maximum yield strength of shear and torsional reinforcement to 420–800 MPa. This paper presents the experimental results of 73 RC members tested under shear and 42 members subjected to torsion, with high-strength reinforcement. The test results were carefully analyzed, along with other experiments from the literature, to investigate the behavior of RC members with high-strength steel under shear and torsion. Test results indicated that the crack width at the service load level was lower than the allowable limit of 0.41 mm even when members were reinforced with a yield strength of up to 700 MPa. The members under shear, with stirrups strength up to 600 MPa, showed shear tension failure prior to concrete web crushing. However, in the case of torsion, 18% of 153 specimens exhibited torsional compression failure when reinforcement yield strength exceeded 420 MPa. Based on these analyses of test results, a limiting value of 600 MPa for maximum yield strength of shear reinforcement is recommended in this study, whereas the current code-specified limit of 420 MPa on maximum yield strength is suggested to continue for torsional design until more supporting experimental evidence is available to increase this limit.

Exposed column base plate (ECBP) connections are commonly used in steel moment resisting frames. Current approaches for their design are well-established from a mechanistic standpoint. However, the reliability of connections designed as per these approaches is not as well understood. A detailed reliability analysis of the prevalent approach in the United States is performed in this study by using 59 design scenarios from steel moment frames subjected to combinations of dead, live, wind, and seismic loads. The analysis is conducted through Monte Carlo sampling reflecting uncertainties in the loads, material properties, component geometry, as well as demand and capacity models for the various components (e.g., base plate, footing, anchor rods) of the connection. Results indicate that the current design approach leads to unacceptable and inconsistent probabilities of failure across the various components. This is attributed to: (1) the use of a resistance factor for the footing bearing stress that artificially alters flexural demands on the base plate, and (2) the calibration of resistance factors for the plate and anchors without appropriate consideration of variability in demands. Two alternative approaches are examined as prospective refinements to the current approach. One eliminates the resistance factor for the bearing stress when used to determine flexural demands in the base plate, while the other considers overall failure of the connection rather than failure of individual components within the connection. For both approaches, new resistance factors are calibrated to provide consistent and acceptable probabilities of failure across all limit states and all types of loading. Design and cost implications of these alternative approaches are summarized.

Steel-plate composite (SC) walls consist of two steel faceplates connected with tie bars and then filled with concrete. The tie bars provide stability to the empty modules and serve as out-of-plane shear reinforcement after the concrete sets. The tie bars used in SC wall design can vary significantly, for example, round bars, rectangular bars, channel sections, or diaphragm plates. This paper presents the results of experimental and computational investigations conducted to evaluate the out-of-plane shear behavior of SC walls with four different types of tie bars or shear reinforcement. The experimental program consisted of ten full-scale out-of-plane shear tests. The parameters included were the section depth, steel faceplate thickness, shear span-to-depth ratio, longitudinal reinforcement ratio, and shear reinforcement ratio. The experimental results are presented in detail, including response plots pertaining to various displacements, rotations, and strain measurements, along with discussions of concrete cracking and shear reinforcement yielding behavior up to failure. The experimental strengths obtained from this study, combined with tests performed by researchers outside the US, indicated that the current AISC N690 code equations are appropriate for estimating the out-of-plane shear strength of SC wall designs that have different types of shear reinforcement. This paper also includes recommendations for improving and optimizing the strength calculations for special SC wall design cases that are not adequately addressed by the current code provisions. Observations from the experimental results were further supported by three-dimensional (3D) finite-element analyses conducted using benchmarked numerical models. This benchmarked numerical modeling approach is recommended for obtaining additional insight into the out-of-plane shear behavior and conducting numerical parametric studies.

The increasing attention of governments and insurance companies toward the evaluation of tsunamis’ impacts on coastal communities led to a renewed interest in assessing the behavior of existing buildings under onshore tsunami flows. Codes and standards regulating assessment procedures for existing structures under tsunami loading are currently missing, and only a few design codes for vertical evacuation shelters can be found. Furthermore, structural analysis methods currently assume watertight buildings for the assessment of their performance under tsunami inundation. In this work, a methodology for assessing the performance of reinforced concrete (RC) buildings that considers explicitly the progressive failure of exterior breakaway infill walls hit by tsunami flows is proposed. The effects of the progressive failure of breakaway infill walls on the overall performance of RC buildings have been highlighted on case-study buildings representative of low-, mid- and high-rise buildings built before the 1980s in the Mediterranean area, characterized by masonry infill walls with low out-of-plane (OOP) capacity. In the absence of specific guidelines for assessment, load models provided by existing tsunami design codes for evacuation buildings were adopted and opportunely modified for the case of buildings with breakaway infill walls. The explicit consideration of the failure of exterior breakaway infill walls completely changed the distributions of loads inside the structure, leading to different structural capacity and damage evolution with respect to watertight buildings. The height of the building affected the global capacity but did not influence the damage evolution. The proposed methodology can represent a suitable solution for a realistic performance assessment of frame structures with breakaway claddings.

In this paper, the punching shear behavior of interior slab-rectangular column connections without shear reinforcement under static concentric loading is studied using a three-dimensional, nonlinear, finite element model (FEM) in ABAQUS version 6.12 based on the concrete damaged plasticity model. The FEM was calibrated based on seven experimental tests selected from literature. The predicted shear capacities were compared to punching and one-way shear predictions according to published standards and the critical shear crack theory (CSCT). The finite element analysis results show that the impact of column rectangularity on punching shear capacity is not only dependent on the column aspect ratio but becomes more severe as the ratio of the minimum column dimension to the effective depth of the slab increases. This behavior was found to be implicitly accounted for in some published European standards and the CSCT.

Inelastic response of reinforced concrete columns to combined axial and flexural loading is characterized by plastic deformations localized in small regions, which are idealized as plastic hinges. Under extreme events such as earthquakes, the load-carrying and deformation capacities of reinforced concrete beam/columns are highly dependent on the accuracy of this idealization for which the plastic hinge length is a key parameter. From a design perspective, a reinforced concrete column can only attain the ductility characteristics prescribed by its performance level if it is provided with sufficient confinement along the length of its plastic hinge zones. From an analysis standpoint, an efficient, nonlocalized, and objective finite-element simulation of column behavior requires accurate plastic hinge length definitions. This paper presents a novel data-driven model for predicting the plastic hinge length of reinforced concrete columns and its implementation in force-based fiber beam-column elements. The model is based on an ensemble machine learning algorithm named adaptive boosting (AdaBoost) and is trained using the results of 133 reinforced concrete column tests conducted in the period from 1984 to 2013. The performance of the model is assessed using the 10-fold cross-validation technique. It is shown that the prediction accuracy achieved using the proposed method is considerably higher than those of state-of-the-art empirical relationships and several other highly effective machine learning base models. Furthermore, numerical experiments reveal that the force-based beam-column models using plastic hinge length predictions of the developed model closely resemble the monotonic and cyclic behavior observed in laboratory experiments.

An internal steel frame–retrofitting method without diagonal braces was studied to strengthen existing reinforced-concrete (RC) moment frames with nonseismic details. For better constructability and structural capacity, a novel shear connection method was developed and verified by cyclic shear testing. To evaluate the seismic performance of retrofitted frames, three two-story moment frames with and without strengthening were tested under cyclic lateral loading. The test results showed that, despite partial composite action between RC and steel members, the proposed retrofit method significantly increased the stiffness and strength of the RC moment frame, achieving a satisfactory deformation capacity greater than 2% drift ratio. On the basis of the test results, the failure mechanism of the retrofitted frame was discussed, considering the shear connection behavior. The test strengths of the frame specimens were compared with the predictions based on a simple plastic mechanism. Further, the degree of partial composite action between the RC and steel members developed by shear connections was addressed to improve the strength predictions.

Structural insulated panels (SIPs) are thermally efficient, prefabricated structural elements that expedite on-site construction with a minimal number of skilled workers. This research aimed to model the time-independent mechanical response of transversely loaded SIPs with plywood skins and a closed-cell rigid polyurethane foam core. The foam core was characterized in both shear and compression through experimental testing, and a trilinear strain-based constitutive model was found suitable for the shear, while a linear response was adequate for compression. Two models, one analytical the other numerical, were produced using the component behavior and validated by comparison to the results of full-scale SIPs experimentally tested in quarter-point bending at two spans, 2.40 and 3.65 m. The analytical model is based on thin-faced, antiplane-core sandwich beam theory, while the numerical model is a two-dimensional plane-strain finite-element model (FEM). Good agreement was found between the analytical model and full-scale bending tests. However, it was found that the experimentally observed polyurethane shear moduli had to be reduced to 77% of their original values to provide good agreement of the FEM with the full-scale bending tests. While both models accurately predicted the bending deflection of the panels, neither was able to satisfactorily predict ultimate strength.

In this paper, an innovative low-yield-point corrugated steel plate damper (LCSPD) was proposed, which consisted of two corrugated webs as the shear component and two outer corrugated plates as the bending component. Four LCSPDs were studied by varying the corrugation directions and arrangement forms. The lateral strength, energy dissipation, ductility, hysteretic behavior, and equivalent viscous damping coefficient of the LCSPDs were estimated by quasi-static tests. A finite element analysis was carried out based on the variables of web thickness and aspect ratio, and the validity of the finite element analysis was confirmed by comparing the results of the model with the experimental results. Comparing the horizontal low-yield-point corrugated steel plate dampers (LCSPD_H) with the vertical low-yield-point corrugated steel plate dampers (LCSPD_V), Damper specimen LCSPD_H exhibited better energy dissipation and ductility. Finally, a simplified formula was proposed to estimate the shear-carrying capacity of the LCSPDs, and the calculated results agreed well with the experimental results.

For performance-based design of reinforced concrete moment frames, the inelastic load-displacement relationship including strength degradation of beam-column joints should be accurately defined. In this study, a simplified design equation for joint shear strength was developed, addressing the effects of the target story drift ratio, beam rebar detail, joint configuration ratio, and joint hoops. Using the proposed method, a plastic hinge element was developed for nonlinear numerical analysis of beam-column connections. The proposed model was applied to existing interior and exterior beam-column joint specimens with or without joint hoops. The predicted lateral load-drift ratio relationships were compared with the test results and current design models. An existing cyclic behavior model was also implemented in the proposed plastic hinge model for time history analysis.

Construction of unreinforced masonry (URM) buildings has been a common practice in many countries. Strengthening of such buildings located in seismically active regions has become extremely important. Although numerous strengthening techniques have been suggested in the literature, most of these methods are either qualitative in nature or too expensive. In this study, effectiveness of a simple strengthening scheme for URM buildings using surface-mounted steel bands is evaluated by carrying out experimental, numerical, and analytical studies. Three full-scale single-room specimens, unstrengthened as well as strengthened using two configurations of the strengthening scheme, are first tested under quasi-static cyclic loading. The strengthening is found to significantly improve the lateral-load behavior of the URM building. The experimental response data are then used to develop finite-element models for carrying out a parametric numerical study. It is observed that even small cross-sectional area of steel bands are sufficient to improve the lateral-load behavior of URM buildings. There is no appreciable advantage of using higher cross-sectional area of the steel bands. Finally, regression analysis is carried out using the numerical data, and an empirical model is developed for estimation of the lateral strength of the strengthened building.

Lack of design standards and guidelines is the most important barrier limiting widespread use of mass timber panel–concrete (MTPC) composite floor systems, a preferred choice by designers in modern multistory mass timber construction. The commonly used Gamma method of designing timber–concrete composite floors has some limitations and cannot predict the load-carrying capacity and failure modes of composite floor systems. Therefore, an analytical model was developed considering the interlayer connector behavior under the elastic-plastic range along with an acoustic layer between timber and concrete, to accurately predict the capacity and failure modes of MTPC composite floor system. One-way acting composite floor panels were tested under four-point bending with different configurations to investigate the influence of different parameters and to validate the developed capacity prediction model. It was found that the model can predict the capacity of the MTPC composite system within 17% of the experimental value and the associated failure mode. This developed capacity prediction model for MTPC composite floors will facilitate the use of these system in mass timber construction.

Fixed offshore platforms in the Gulf of Mexico (GoM) are traditionally designed following the working stress design (WSD) format, that is, the factor of safety approach. In 1993, the first reliability-based design standard for offshore platforms using the Load and Resistance Factor Design (LRFD) format was published by the American Petroleum Institute (API) called Recommended Practice for Planning, Designing, and Constructing Fixed Offshore Platforms—Load and Resistance Factor Design, which is commonly abbreviated as API RP 2A-LRFD 1st edition. API RP 2A-LRFD 1st edition has had a significant influence in developing the LRFD format of the ISO for fixed offshore structures (i.e., ISO 19902), but it was not commonly used in the United States, and it was withdrawn in 2012 due to a lack of maintenance. The API RP 2A-LRFD format was reintroduced in 2014 as a draft 2nd edition. This study was carried out in the context of the plan to prepare the API RP 2A-LRFD 2nd edition under the effort to align and merge the API and ISO standards as a single global standard. The objectives of this study are to assess the fixed offshore platform component reliability with the accumulated experience in the last several decades, and to evaluate the suitability of the load and resistance factors in API RP 2A-LRFD 1st edition for the 2nd edition of API LRFD given the updated metocean characteristics after Hurricane Katrina in the GoM. The key findings of this study are that the LRFD format with the load and resistance factors from API RP2A-LRFD 1st edition gives slightly higher reliability levels for component checks than the WSD format, but lower reliability level with the updated new metocean criteria comparing to the criteria in the 1980s. A list of recommendations on the load and resistance factors was provided to facilitate the preparation for the API RP2A-LRFD 2nd edition.

Timber-concrete composite (TCC) floors are becoming more commonly used in mass timber construction due to their increased stiffness and strength relative to nonconcrete composite timber floors. Current building codes do not recognize the contribution of the composite action of TCC floors to their combined strength and fire performance. Extensive structural testing is required for structural engineers to design fire protection in timber buildings that use TCC floors using either alternate means and methods or structural fire engineering. This paper presents two experimental studies conducted to examine (1) properties of shear connection systems used in TCC floors through ambient temperature direct shear tests, and (2) the behavior of TCC floors through large-scale fire tests performed at the National Research Council (NRC) in Canada. The main objective of this research is to collect data on the fundamental behavior of TCC floors in a fire. The results indicate that TCC floors have improved fire performance when compared with mass timber floors. In addition, the research quantifies the force-slip behavior of the shear connectors used and benchmarks the flexural behavior of TCC floors at ambient and elevated temperatures to existing analytical models.

This technical note presents findings from a study investigating the correlation between the number of test data available and the choice of the uncertainty factors (called beta) used in the FEMA P695 methodology to quantify the quality of test data and modeling. On the basis of reviewing data from the existing literature on past FEMA P695 studies, an attempt was made to assess if there exists a trend in the choice of beta factors for new structural systems. This study can help in better estimating the test data (${\beta }_{TD}$) and modeling (${\beta }_{MDL}$) uncertainty factors for a new structural system with the available test data.