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The need for reassessment of the fatigue life of existing structures is increasing as the world's infrastructure ages. A fatigue life reassessment typically begins with an assessment of the current condition of the structure. The condition assessment techniques range from visual inspection to X-ray inspection or detection of acoustic emissions. The fatigue reliability of the structure can be estimated from probabilistic fatigue life or fracture mechanics models. The data obtained from the condition assessment can be combined with these models to estimate the remaining service life of a structure using Bayes' theorem. Simulation techniques are often used to facilitate these calculations. If the remaining service life is inadequate, it may be desirable to repair the structure; however, repairs must be performed carefully to provide the desired benefit. On the other hand, economic factors may dictate a course of action other than repair, such as replacing the structure or changing the operation of the structure.

Many structures service in complex environments where multiple environmental factors (MEFs) coexist, and the coupling effects of MEFs often aggravate structural damage, thus increasing the risk of structural collapse and economic loss under seismic excitation. For structural damage caused by coupling effects of MEFs, previous studies have been mostly focused on one-way coupling analysis, such as the effect of structural pre-corrosion on its fatigue damage, and less attention to the interaction coupling effect of MEFs, which make it difficult to quantitatively calculate the interactive coupling damage due to the existence of MEFs. The large error of using one-way coupling damage calculation method to estimate the residual mechanical performance of the structure will reduce the reliability of seismic risk assessment of the structures suffering interaction coupling of MEFs. To solve such problem, this paper proposes a damage calculation method for structures considering the effect of interaction coupling of MEFs by establishing a multivariable interaction model, in which a coefficient β(t) is introduced to characterize the time-varying mechanisms of the interaction coupling effect of MEFs (e.g., the acceleration of structural damage with service time). Then, the solution method for β(t) is proposed by using Bayesian inference. Finally, a framework for analyzing the time-varying seismic risk of engineering structures considering the evolution of damage caused by interaction coupling of MEFs is established in which the uncertainty of environmental factors is also involved. The presented analysis framework is illustrated using a towering structure in a coastal area, and the results emphasize that the interactive coupling effect of MEFs can significantly increase the risk of structural collapse and economic loss. [ABSTRACT FROM AUTHOR]

This paper presents a unique study on the dynamic identification of the tallest glue-laminated timber frame building in the world using forced vibration tests (FVTs) and long-term ambient vibration tests (AVTs). Because the amount of sway in service under wind has become the governing design criterion for tall timber buildings, this paper aims to provide useful information and evaluate available tools and methods for modal identification in tall glulam timber frame buildings. First, combined operational modal analysis schemes based on the variational mode decomposition with the stochastic subspace identification and the random decrement technique were adopted to identify the modal properties from nonstationary ambient data. Then, unique full-scale forced vibration tests were conducted using two different methods to excite the building: measured electrodynamic shakers excitation and unmeasured rhythmic human-induced excitation. Finally, a finite-element (FE) model of the tall glulam frame building was developed and frequency response function (FRF)–based model updating was conducted showing that the FE model was able to predict the modal behavior of the test building. The results show that natural frequencies identified from output-only techniques are in good agreement with the FVT results. Damping ratios obtained from both AVTs and FVTs exhibited amplitude-dependent behavior with a larger variation observed in the FVT results due to larger range of response amplitudes. These results have significant consequences for the design of tall timber buildings under serviceability-level loading, where damping plays an important role. The resulting damping ranges presented in this paper can serve as a useful guideline for practicing engineers in developing their prediction models of tall timber buildings under serviceability-level loading. [ABSTRACT FROM AUTHOR]

Performance-based design optimization (PBDO) aims to design safe, resilient, and cost-effective structures. Methods used for PBDO have evolved by integrating numerical modeling, performance-based design principles, and optimization algorithms. The PBDO framework enables the design of structures with optimal performance and cost. This paper provides researchers with a comprehensive review of the rapidly growing field of PBDO. The evolution of PBDO methods is discussed with the goal of identifying the challenges that must be addressed in future studies. Knowledge gaps are brought to the forefront to emphasize the need for further investigation that expands on the application of PBDO in structural design. Various deterministic and probabilistic formulations for PBDO of structural systems under seismic and wind loading are reviewed. The formulations encompass one or more objective functions, including the upfront, life-cycle, and repair costs. Furthermore, the paper reviews retrofit design studies that have used PBDO methods. The high computational demand in performing PBDO is identified as the major challenge. Possible approaches to alleviate this and other challenges are discussed. [ABSTRACT FROM AUTHOR]

Past research efforts have developed several self-centering beam-to-column connections for minimizing structural damage in steel moment frames after severe earthquakes. However, less focus has been on low-damage column base connections. Severe damage at the base of columns in conventional steel structures with moment frames is likely during an intense earthquake, rendering the building nonresilient. This paper evaluates the application of a recently developed viscoplastic damper in low-damage column base connections. The proposed viscoplastic damper is a rubber-steel core damper (RSCD), which consists of a high-damping rubber layer and several ductile steel bolts. The proposed column base connections prevent damage and inelastic deformations in the steel column and its base plate by allowing a rocking mechanism at the base of the column and limiting damage to easily replaceable steel bolts in the dampers. The paper discusses the design and behavior of the column base connections equipped with RSCDs. Continuum finite element models of RSCD dampers were developed and validated using experimental results. The rocking response was validated using experimental results for rocking columns with a silt damper. A total of 21 finite element models of rocking columns with RSCD were used to numerically examine the column response to combined axial loading and cyclic lateral loading. The influence of different parameters on the cyclic response of the proposed column base connections was also evaluated. These parameters are steel bolt diameter-to-length ratio (d/h), rubber thickness, column axial compressive load, number of bolts, and steel material type. The results confirmed the effectiveness of the proposed column base connection for minimizing damage to the steel column and its base plate. An optimal d/h ratio of 0.4 was found for the design of RSCDs. In addition, analytical formulas are presented to evaluate the yield and ultimate strength of the proposed column base connection, and the comparison with FEM results indicates that the presented mechanism has sufficient accuracy. [ABSTRACT FROM AUTHOR]

Investigates the application of fatigue reliability reassessment procedures to existing world structures and its relevance to structural repair and conservation. Emphasis on structures subjected to fatigue load; Increased need for building repair; Costs in structural conservation; Basis of fatigue life calculation; Dependence of inspection schedule to fatigue reliability estimates.

This paper presents the experimental results of Grade 8.8S high-strength steel coupons tensioned to fracture at room and elevated temperatures, followed by finite element analyses for investigating the ductile fracture behavior. Smooth round bars, notched round bars, flat shear sheets, and flat grooved sheets were tested at room temperature, which covered a wide range of stress states. The relationship between the ductility of the Grade 8.8S high-strength steel and the stress state was discussed. Extra smooth and notched round bars were also redesigned and tested at elevated temperatures. The nonlinear variations of material properties, including elastic modulus, yield strength, and tensile strength, were discussed. Different modeling strategies were used for the room and elevated temperatures. At room temperature, three uncoupled ductile fracture criteria were evaluated regarding their applications in the Grade 8.8S high-strength steel. Besides, in conjunction with a modified Johnson–Cook (JC) hardening model, the JC fracture criterion was improved and characterized by an exponential temperature function, as the original linear temperature function could not accurately describe the relationship between the fracture strain and temperatures. The developed finite element models closely traced most specimens' load-displacement paths at the room and elevated temperatures. [ABSTRACT FROM AUTHOR]

Tornadoes are intense localized convective windstorms that are among the most devastating natural hazards that occur in the United States. Although the probability of any tornado striking one particular building in any given year is quite low because of its small footprint, when strong tornadoes strike densely populated areas, the results can be catastrophic; the Joplin, MO tornado of 2011 caused 161 fatalities and nearly $3 billion in damages. Such losses are projected to increase in the future as a result of urbanization and economic development. ASCE Standard 7-22 on Minimum Design Loads has, for the first time, included new reliability-based design criteria for tornado loads. The objective of this paper is to provide archival documentation of the basis for these tornado-resistant load provisions in Chapter 32 of ASCE 7-22. This paper summarizes the significant challenges that were overcome in addressing the fundamental differences between effects of tornado and nontornadic winds and the higher uncertainties associated with tornado wind pressures that must be accommodated in the risk-informed framework of ASCE 7-22. These challenges were addressed through reliability analyses that led to new tornado load criteria that provide reasonable consistency with the reliability delivered by existing criteria for nontornadic winds. [ABSTRACT FROM AUTHOR]

The paper introduces a new model of compressive membrane action (CMA) for a conical fan failure mechanism around a patch load in a reinforced concrete plate with in-plane restraint. The new model is based on a concept of 3-dimensional wedging and it is fundamentally different from conventional arching models of CMA. The new model accounts for the effects of CMA on the bending resistance at yield lines and the complementary wedging effect of compressive membrane forces at the yield lines, considering the interaction between the radial and tangential forces acting on the wedgelike segments in a restrained fan. The model was developed in the context of an investigation of the strength of fiber reinforced shotcrete (FRS) tunnel linings, but it is readily adaptable for conventional reinforced concrete plates and slabs. The paper compares the wedging model results (predicted load-deflection curves) with field test results for FRS tunnel linings. It is shown that the wedging model provides a good approximation to the available test results. [ABSTRACT FROM AUTHOR]

This paper introduces a topology optimization approach based on the virtual element method (VEM), incorporating uncertainties. The objective of this optimization process is to design an optimal material layout for problems governed by linear elasticity equations to minimize the volume while satisfying probabilistic compliance constraints. The VEM is used to solve the boundary value problem in reliability-based topology optimization (RBTO). In the comparison between the VEM and the standard finite element method (FEM), a key difference emerges in the absence of explicitly defined shape functions tied to discrete degrees of freedom in VEM. Unlike FEM, VEM directly constructs the discrete bilinear form and load linear form without the need for computing shape function derivatives within the elements. This flexibility accommodates meshes with intricate geometries and arbitrarily shaped elements. The paper discusses the computational efficiency of VEM RBTO and explores the geometric impact of tessellations on converged topologies, demonstrating reduced susceptibility to checkerboard patterns compared to conventional quadrilateral elements. Additionally, the single-loop approach is examined, showcasing comparable accuracy to the first-order/second-order reliability methods (FORM/SORM) of RBTO using VEM. Numerical results for several problems that demonstrate the feasibility of the proposed method are presented. [ABSTRACT FROM AUTHOR]

Tensegrity structures, which consist of tension cables and compression rods, are widely used in various fields. It is particularly important to find the tensegrity with definite geometric configuration for the following research and application. This paper presents a traversal topology-finding method for tensegrity structures based on dynamic programming algorithm and ground structure method. After the designer has given the cable topology, the dynamic programming is adopted to realize the traversal selection of the rod. In order to reduce the traversal space and realize the constraint of rod length type, the rod is classified according to length. Compared with existing topology-finding methods, the algorithm can not only output all feasible topologies but also incorporate structural constraints, such as rod length type and prestressed stability, into the calculation process. Four tensegrity numerical examples illustrate the feasibility and effectiveness of the topology-finding method. [ABSTRACT FROM AUTHOR]

Reports that the American Society of Civil Engineers (ASCE) and the Structural Engineering Institute (SEI) are looking for nominations for the 2006 ASCE and SEI Awards. Objective of the ASCE and SEI Honors and Awards Programs; ASCE awards based on meritorious papers; SEI awards.

The special collection on Twenty Years of Advances in Disproportionate Collapse Research and Best Practices since 9/11/2001 is available in the ASCE Library (https://ascelibrary.org/jsendh/twenty years disproportionate collapse). Kong et al. ([8]) report their experimental and numerical findings on the progressive collapse behavior of scaled six-column subframe composite floor systems subjected to the removal of a side column. Beck et al. ([2]) target optimal required ratios of column-to-beam strengths in column loss situations, considering several failure modes and providing conceptual design recommendations to mitigate disproportionate collapse of frame structures. Three papers focus on advances in analysis and design methods for disproportionate collapse ([2]; [7]; [18]) and show that their limitations no longer are a barrier to disproportionate collapse-resistant design that they once were. [Extracted from the article]

Shake-table tests of a full-scale 3-story reinforced concrete frame building were performed at the E-Defense facility (Miki City, Japan) as part of the Tokyo Metropolitan Resilience Project. Building data were collected before and after each shake-table experiment, using light detection and ranging (lidar) scanning technology. Three-dimensional point clouds were generated and processed to investigate the damage features that can be extracted, which are important for postdisaster structural assessment purposes. To this end, this paper discusses aspects pertaining to lidar data processing and registration, calculation of residual displacements and interstory drifts, and concrete cracking and spalling identification and measurement. Most notably, this paper deals with very large data sets, processed to extract structural response information at both global and local scales. Limited multiscale work has been done in the past, and the different sets of challenges that arise have typically been addressed separately. Evidently, this gap needs to be filled before lidar can be effectively used in the field for structural assessment applications. A series of examples in which lidar data are processed and analyzed to assess specific structural components is illustrated, showing that point cloud data can indeed be processed to obtain measurements of global residual drifts or of the extent of visible damage (e.g., crack width and spalling). Although preliminary in nature, the results presented in this paper indicate that collecting postdisaster data using terrestrial lidar scanners has the potential to contribute improving how buildings are assessed in the aftermath of seismic events. [ABSTRACT FROM AUTHOR]

Exactly one decade after taking the helm in 2010 and 22 years after joining the board of the I Journal of Structural Engineering i (JSE), I proudly stepped down from my position as editor in chief on September 30, 2020. One of the secrets to the eminence of JSE is that the I Journal i is seamlessly integrated with the committee structure of ASCE's Structural Engineering Institute (SEI). Professor van de Lindt: Incoming Editor in Chief It is with great pleasure that I announce that Professor John van de Lindt has been appointed by ASCE SEI as the new JSE editor in chief starting October 1, 2020 (Fig. [Extracted from the article]

In December 2021, an EF-4 tornado swept through several Midwest states in the United States, with Kentucky being the worst hit. Among the impacted towns was Mayfield, KY, where the historic buildings in downtown suffered significant damage. In response to this disaster, the authors conducted a reconnaissance mission to digitally document the affected historic structures. This involved capturing a series of three-dimensional (3D) point clouds, providing detailed spatial data about the impacted buildings. The resulting data set includes both the original raw data and processed information, now accessible via the DesignSafe open-access repository. This paper outlines the data collection process for the impacted buildings, and the steps undertaken to process it. The final product of this endeavor are the point clouds generated for the historic building typology, which included 10 historic buildings and 2 comparable religious buildings. These point clouds serve as invaluable resources for further analysis, aiding in understanding a disaster's impact, and guiding restoration endeavors. [ABSTRACT FROM AUTHOR]

Implementation of existing stress–strain models for cold-formed steel requires the input of key material parameters determined from corner coupon tests on cold-formed portions. This paper proposes various approaches that can accurately describe the stress–strain responses of cold-formed steel by using corner material properties if known, or by using parent material properties and the corner geometry after cold-forming in the absence of corner material properties. First, a comprehensive database of coupon test results of cold-formed steel is assembled. A total of 483 corner coupon test results with 236 full stress–strain curves are collected from 31 sources, covering a large range of steel grades with nominal yield strength varying from 235 to 960 MPa. The applicability of existing empirical models for determination of the enhanced yield strength, ultimate strength, and ultimate strain is carefully evaluated. New predictive expressions for the required input parameters (namely, 0.01% or 0.05% proof stresses for the use of the two-stage Ramberg-Osgood model, and the strain hardening exponent for the use of one-stage material model) are subsequently derived. Prediction performances of the two-stage Ramberg-Osgood model and the one-stage material model are then evaluated against experimental stress–strain curves under different availabilities of primary material parameters. According to the proposed approaches, the minimum required input parameter to utilize these models is only the yield strength of cold-formed steel or, alternatively, the yield strength of the parent metal and corner geometry after cold-forming. The developed models are proved to be accurate in predicting the monotonic stress–strain response (up to the ultimate point) of cold-formed steel, and they are suitable for use in parametric studies and advanced modeling of cold-formed structures. [ABSTRACT FROM AUTHOR]

This paper presents a data set of a fire-induced collapse on an existing building with a truss roof. The data set contains the thermal and structural responses of the tested building, the mass loss of the fuel, the heat release rates, and the videos of the entire test. The test building and basic test scheme are introduced first. Then, the monitoring points and corresponding equipment are presented. All data obtained have been converted to a unified format and uploaded to a published data set. Detailed data formats and processing methods are introduced, and metadata are provided. To the authors' knowledge, this is the first open-access test data on fire-induced collapse of a real building, which is of great significance for further investigations on fire-induced building collapse and performance-based design for fire safety of buildings. This data set can be used to validate the existing temperature distribution models and develop deep-learning models in structural fire engineering. Moreover, the data set can validate and develop some cutting-edge theories and techniques in structural fire engineering, such as the approaches for the early-warning collapse of structures exposed to fire and the synchronous noncontact acquisition of structural deformation in fire. [ABSTRACT FROM AUTHOR]

This paper investigates the fire resistance of extended end-late beam-column middle (EEBM) joints, taking into account the gradient temperature effect under postearthquake fire (PEF). First, finite element (FE) models of the EEBM joints were established based on mechanical models under different conditions, the accuracy of the models is validated by existing experiments. Next, the gradient temperature distribution, residual deformation and stress in the EEBM connections were analyzed. Finally, 125 FE models were established to conduct parameter analysis including the column flange width-thickness ratio (α), column web height-thickness ratio (η), beam flange-to-end plate thickness ratio (γ), beam flange width-thickness ratio (δ), beam web height-thickness ratio (β) and damage variables (D˜). The generalized failure point to determine the generalized ultimate displacement and a calculation method for the flexural capacity at high temperatures are proposed against the EEBM connections. The results demonstrate that the α , η , and γ have a significant impact on the failure modes of the EEBM connections. The generalized ultimate displacement of the EEBM connections is approximately 1/40 of the beam span. The α , γ , and D˜ dramatically affect the fire resistance of the EEBM connections. The weakening of the flexural capacity due to damage is greater than that due to high temperatures. The findings can provide basic data, theoretical reference, and technical support for the design and research of EEBM connections under PEF. Practical Applications: EEBM connections are widely used in multi-story steel frame and portal frame, etc. Postearthquake fire is common, which will cause significant casualties and economic losses. On account of the residual stress and deformation caused by earthquake in EEBM connections, it is impossible to accurately evaluate the reliability and safety of EEBM connections under postearthquake fire using the failure mechanism of EEBM connections under fire. Therefore, the findings of this study can provide valuable reference for design, reinforcement and repair of EEBM connections. [ABSTRACT FROM AUTHOR]

In this paper, a novel arch structure—circular box arch with sinusoidal corrugated webs (CBASCW)—is presented. Through the methods of theoretical derivation and finite element simulation, we studied its in-plane elastic buckling and in-plane elastoplastic stability. Through theoretical derivation, a shear stiffness formula of the arch section is determined, and the elastic buckling load when the arch is in pure compression state is proposed considering the shear deformation. We also introduced a simplified model, which can simulate the deformation and internal forces conveniently. The failure mode and global elastoplastic instability mechanism are investigated under uniformly distributed full-span radial load, uniformly distributed full-span vertical load, and uniformly distributed half-span vertical load. Furthermore, by introducing a regular slenderness ratio and stability coefficient, the stability curve of the arch under the state of pure compression is plotted. Subsequently, based on the stability curve and the numerical simulation results of a simplified model, a design formula for the stability bearing capacity is proposed for situations where global elastoplastic instability occurs. [ABSTRACT FROM AUTHOR]

This study deals with the compressive performance of cold-formed steel semi-oval hollow section (CFS-SOHS) stub columns after exposure to a standard fire. An experimental program was carried out on 17 CFS-SOHS stub columns after four different fire exposure temperatures, namely 300°C, 550°C, 750°C, and 900°C. Details of post-fire test specimens, material properties, stub column test arrangements, and results are described and discussed in this paper. A finite-element model was established and then validated by the experimental compressive performance in terms of ultimate strength, load-end shortening response, and failure mode. Parametric analyses were then performed on 160 post-fire CFS-SOHS stub column specimens to furnish more numerical data. The acquired experimental and numerical compressive strengths were compared against the design predictions by the direct strength method (DSM) initially calibrated for open sections, and the modified DSM initially proposed for CFS-SOHS without fire. A reliability analysis was performed. Comparisons show that the modified DSM offers accurate and reliable post-fire residual resistance predictions for CFS-SOHS stub columns after exposure to the standard fire. [ABSTRACT FROM AUTHOR]

The research on cold-formed steel (CFS) built-up columns, which has grown over the past decade, has been instrumental in developing new CFS built-up columns with transversely spaced chords, demonstrating better axial performance than conventional I-type built-up columns. However, previous research findings on CFS laced columns have been limited, with no data available on stub columns. This paper presents the first test program for cold-formed steel laced stub columns using plain channels. The program involved fabricating 12 specimens with a single lacing configuration, connecting lacing elements and end plates to the chords using self-drilling screws, and evaluating the impact of critical parameters on column performance under concentric axial loading. Important variables such as lacing slenderness, end plate length, and transverse chord spacing were examined, with the built-up section's aspect ratio varying from 0.75 to 1.25. The failure modes, peak strengths, and load-displacement curves of the stub column specimens were used to evaluate their performance. In addition, the study compared strength predictions from the current American Iron and Steel Institute (AISI S100-16) and Eurocode (EN1993-1-3) standards against the test strengths. Unlike slender column axial strength, these current standards predicted the axial strengths of the stub columns better, with an overprediction of less than 5%. It was verified that lacing slenderness and end plate length variation does not change the failure mode in CFS laced stub columns. Further, earlier recommendations on end plate length for CFS laced columns cannot be extended to CFS laced stub columns. [ABSTRACT FROM AUTHOR]

This paper presents a numerical parametric study to examine the structural response of drilled shaft footings (pile caps) presenting different design characteristics, which have not been studied in depth in previous experimental studies. The numerical analyses were conducted with nonlinear finite element models representing typical designs and details of actual footings. The modeling scheme was validated using experimental data from large-scale drilled shaft footings. Key parameters of the numerical study included footing geometric properties, concrete strength, and reinforcement ratios. The results of the parametric studies were examined to identify key behavioral and design aspects to be considered when using 3D strut-and-tie models for the design of drilled shaft footings. The analysis results show that influences associated with footing and column aspect ratios were essentially negligible. However, it was estimated that an increase of the angle of inclination between the compression strut and the vertical axis led to significant reductions in footing stiffness and load capacity. The effect of shaft diameter was also examined in light of lateral concrete confining effects, and it was found that larger shaft diameters provide increased footing capacities. Analyses performed to estimate the influence of concrete compressive strength showed that splitting of the strut controlled the concrete-governed failure mechanism of footings. Finally, the models developed with different amounts of reinforcement revealed that increasing bottom mat reinforcement leads to increased ultimate loads; however, the rate of strength increase decreases with increasing reinforcement ratio. Providing a minimal amount of top mat and side face reinforcement was estimated to impact the structural responses of the footings positively; however, increasing the ratios of the top mat and side face reinforcing bars beyond this minimum did not significantly impact footing strength. [ABSTRACT FROM AUTHOR]

Interest in earthquake resilience has increased in recent years, and the use of building cluster performance objectives has been shown to be an effective method for evaluating the resilience of a built environment. A building cluster is a portfolio of buildings that share the same role in a community; its performance objectives are defined by considering earthquake scenarios, hazard levels, and individual building performance. The methodology presented in this paper employs performance-based assessments to estimate the probability of achieving building cluster performance objectives immediately following a seismic event. It can be used to assess the immediate post-earthquake community resilience in five steps: (1) hazard analysis; (2) conditional assessment of individual building performance; (3) conditional assessment of building cluster performance; (4) building cluster performance assessment by aggregation; and (5) earthquake resilience assessment of building clusters considering all hazard levels of interest. The design and extreme hazard levels are formulated using ground motion records selected based on the conditional spectra considering characteristics of earthquake scenarios and spatial correlation. Three performance objectives are defined for individual buildings and building clusters: (1) functionality; (2) safe and usable during repair; and (3) collapse prevention. Two engineering demand parameters, i.e., the maximum transient and the permanent interstory drift indices, are used to estimate individual building performance. The probability of achieving building cluster performance objective is calculated using the total probability theorem. The application of the proposed methodology is demonstrated using two clusters of reinforced concrete buildings, corresponding to ASCE 7 Risk Category II and IV structures, in San Francisco, California. [ABSTRACT FROM AUTHOR]

Four different composite coupling beam-to-composite plate shear wall (CPSW/CF) connection details were developed and proposed. Six large-scale specimens representing the four connections were designed, fabricated, and tested. The connections were subassemblies of coupled composite plate shear walls/concrete filled (CC-PSW/CF) subjected to cyclic lateral loading. The coupling beams were designed to be flexure-critical with clear span-to-depth (Lb/d) ratios of 3.5 or 5.1. This paper presents the experimental program, capacities, and detailed behavioral observations of all six specimens. The effects of connection type and Lb/d ratio on the ultimate strength, stiffness, ductility, and failure modes are evaluated. Major limit states and events included yielding of the steel plates comprising the coupling beam, followed by local inelastic buckling, fracture initiation in the base metal (near the weld toes), and fracture propagation through the beam flange and web plates, leading to loss of flexural strength and failure. All the connections were able to develop and transfer the flexural capacity of the composite beam section. The composite coupling beams developed flexural capacities (10%–50%) greater than those calculated using the plastic stress distribution method. The underlying reasons for this overstrength are evaluated. The AISC flexural stiffness equation for filled composite sections could reasonably estimate the stiffness of the composite coupling beam sections. A fiber-based model of the cross-section was used to calculate the section moment–curvature response of the filled composite beam sections. The calculated flexural capacities were consistent with those calculated by the plastic stress distribution method but lower than the experimentally observed values. The flexural stiffness values were slightly higher than the experimental results. For more accurate comparisons with experimental results, a numerical model is needed to estimate the cyclic lateral load-deformation response while accounting for the effects of local buckling, low cycle fatigue, and fracture. [ABSTRACT FROM AUTHOR]

A steel brace is effective to retrofit old reinforcement concrete (RC) buildings by increasing the horizontal load capacity of structures. However, concrete cracks that easily occur in the surrounding RC members under tension initiate early strength degradation, so this research aimed to develop a new self-centering brace (SCB) with the compression-only capacity such that no tension force is developed in the brace or to the adjoining RC members. Original SCBs have been developed to reduce the residual deformation of structures with a symmetrically flag-shaped hysteretic response. By altering the force transfer mechanism in the original SCB, a compression-only self-centering brace (C-SCB) can be developed under a symmetrically reversed cyclic loading, providing an alternative for the RC building retrofit. This paper first introduces the mechanics and deformation mechanism of the proposed C-SCB. A test program is then conducted on the cyclic tests of a buckling-restrained energy dissipating bar (EDB) to evaluate the energy dissipation. A 3,695-mm-long C-SCB is composed of posttensioning high-strength steel tendons, steel compression members, and buckling-restrained EDBs for the energy dissipation. The C-SCB in tests showed a good compression-only self-centering capability up to an axial displacement of 31 mm, with a maximum axial force of 1,530 kN. No damage of the steel tendons, compression members, or EDBs was found after three phase tests. Finite element analysis further validated the compression-only hysteretic response and mechanics of the C-SCB in a symmetrically reversed cyclic loading. [ABSTRACT FROM AUTHOR]

This paper aims to evaluate the seismic response of multitiered buckling-restrained braced frames (MT-BRBFs), assess the design provisions specified by the 2022 AISC Seismic Provisions for multitiered BRBFs, and propose improvements to these provisions. A set of 17 frames is first selected by varying bracing configuration, frame height, number of tiers, and tier height ratio. The frames are then designed in accordance with the 2010 and 2022 AISC Seismic Provisions. A numerical parametric study is performed under scaled ground motion accelerations. The results of the parametric study show that when the frames are designed to the 2010 provisions, the frame inelastic deformation tends to concentrate in the tier(s) undergoing tensile yielding due to their lower postyield stiffness, compared to BRBs yielding in compression, which creates unequal story shear, contributed by braces, in adjacent tiers with BRBs in tension and compression and engages column flexure to compensate for unbalanced brace story shears between tiers. Columns experience yielding and even buckling in several cases due to combined flexural and axial load demands. MT-BRBFs designed to the 2022 AISC Seismic Provisions exhibit a more uniform deformation response between tiers and relatively lower flexural demands in their columns. However, these provisions may overestimate column in-plane flexural demands (on the order of 3), resulting in potentially uneconomical design solutions. On the basis of the numerical simulations, modifications are proposed to compression BRBs' adjusted strength to better estimate column in-plane flexure and tier deformation while achieving an economical column design. The proposed improvements are validated using dynamic analyses. [ABSTRACT FROM AUTHOR]

The state of Hawaii is a series of mountainous islands with a topography that is much more complex than the simple isolated hills and escarpments included in ASCE standard ASCE/SEI 7-22 (Minimum design loads and associated criteria for buildings and other structures, ASCE 7). Hawaii state and county building codes have incorporated topographic wind speed mapping since 2007. In 2010, ASCE 7-10 recognized Hawaii as a special wind region. The design wind speed maps, Kzt maps, and site-specific directionality factors as adopted in Hawaii's state building codes constituted the "special Kzt topographic effect adjustments" of the authority having jurisdiction that were referenced in ASCE 7-10. In ASCE 7-16 and ASCE 7-22, microzoned wind speed maps for Hawaii, including the effect of topography and directionality, were incorporated for strength design return periods. This paper provides information on the development of an improved generation of higher-resolution basic design wind speed maps for the state of Hawaii, including better accuracy of topographic and directionality effects. The digital format of these wind speed maps can be readily incorporated into the ASCE 7 digital hazard tool interfaces. [ABSTRACT FROM AUTHOR]

In this paper, an innovative hamburger-shaped eddy current damper (HSECD) is presented to mitigate the responses of civil structures subjected to wind excitations. The damper's capacity to dissipate energy is significantly enhanced through a two-phase configuration of permanent magnets (PMs) and two transmission devices: a ball-screw assembly and a bevel gear group. The improved eddy current damper (ECD) solves the problem that the low damping density of traditional ECDs hinders their application to the field of vibration control for civil structures. First, the construction details of this novel HSECD are elaborated, and its principle is discussed through theoretical analysis and numerical simulation. Subsequently, a prototype of the HSECD was fabricated, and cyclic tensile–compressive tests were conducted to investigate its mechanical performance. Furthermore, the temperature effect on the damper's maximum output force was analyzed, and more than 10% performance degradation was detected in tests with a continuous loading of 1,250 s, while the damper performance quickly reached a steady state after a certain decline. A theoretical model of the HSECD was then established to simulate its hysteretic characteristics, and the accuracy was verified by comparing it with the test data, where their energy error was only 1.9%. Finally, the application of the HSECD to both a single-degree-of-freedom (SDOF) simplified system and a jacking engineering system demonstrates its excellent control performance because the reduction ratios of their peak displacement were as high as 31.1% and 40.9%, respectively. These results highlight the significant practical value of the HSECD in mitigating the wind-induced vibrations for engineering structures. [ABSTRACT FROM AUTHOR]

Angle profiles belong to the most common steel profiles used in several types of civil engineering structures, such as in lattice towers. Although, in such towers, they are usually considered as axially loaded (truss) members, an additional bending moment develops due to the eccentricity between the point of load application and the gravity center of the profile. Therefore, this paper focuses on the buckling resistance of single-angle members subjected to combined compression and bending. The investigations have been performed through numerical parametrical studies and have been compared to different normative documents where interaction equations are provided. [ABSTRACT FROM AUTHOR]

While numerous experimental tests have been conducted on single-story cross-laminated timber (CLT) shear walls, research addressing the drift performance of multistory CLT structures remains limited. This paper presents an experimental parameter study of the lateral performance of two-story platform-type CLT shear wall structures utilizing self-tapping screw connections. The test program consisted of six reversed cyclic tests investigating the impact of: (1) additional floor mass; (2) different angle bracket connections between floors; (3) different tension strap connections between floors; and (4) acoustic insulation layers on both sides of the first-level floor. The results showed that additional dead load increased the lateral resistance and that designing angle brackets to remain elastic limited the sliding contribution to total lateral deformations to less than 10%. The results also showed that the acoustic layer had minimal effect on the performance of the shear walls under the tested conditions. The tension straps significantly influenced the rocking performance, underscoring their importance to achieve similar story drifts in multistory CLT shear wall structures. Finally, while preceding single-story shear wall tests allowed designing the structures, hold-down uplifts on single-story tests were shown not to be representative for tension strap uplifts in multistory tests. [ABSTRACT FROM AUTHOR]

Self-centering braces are an attractive new type of brace able to reduce structural residual deformations after earthquakes, with no requirement of major modifications to structural joints. One primary challenge in widespread implementations of self-centering braces is their high demands of prestressing forces, in order to counteract the anti-recentering resistance induced by their energy-dissipation system. This paper introduces a novel self-centering (SC) brace, denoted as a viscoelastic low-prestressing self-centering (VE-LPSC) brace, that needs only a low level of prestressing force to achieve self-centering. The proposed brace incorporates a novel frequency-independent viscoelastic damper (VED) as its energy-dissipation system. The new VED behaves similarly to displacement-based dampers that provide stable stiffness and damping across various frequencies. Meanwhile, as loading ends, the VED does not generate residual anti-recentering forces, unlike conventional velocity-based dampers. Performance tests on the VEDs were first conducted using three specimens to examine the material's deformation capacity, frequency-independent characteristic, fatigue-resistance capacity, and recovery capacity. Then, six full-scale brace prototype specimens were manufactured and tested, considering three levels of prestressing forces (15, 50, and 100 kN). Test results revealed that the brace achieved complete self-centering and consistent stiffness and strength under various frequencies, even with a prestressing force of 15 kN. With conventional steel strand and Belleville springs as its prestressed elements, the new brace was able to elongate 2.27% (corresponding to a story drift of 4.54%) while maintaining its recentering capacity. The VE-LPSC brace may experience some strength degradation after loading lower to 90%, but its capacity can recover to 98% of the original strength after 2 weeks. [ABSTRACT FROM AUTHOR]

Previous studies have demonstrated that elevated temperatures exert a significant influence on the structural performance of reinforced concrete (RC) members. However, the residual shear performance of the RC beam under the combined effects of stirrup corrosion and fire has not been thoroughly explored. Therefore, this paper aims to investigate this aspect by prefabricating eight RC beams and employing experimental, numerical, and theoretical methods. The influence of varying stirrup corrosion degrees and fire exposure time on the residual shear capacity of these beams was examined. It was observed that corrosion-induced cracks had an impact on the distribution of the temperature field within the RC beams. Furthermore, the exposure to the corrosion–fire combination significantly affected the shear capacity of the RC beams. Notably, stirrup corrosion may lead to a more brittle failure after a fire. To assess the impact of corrosion degree and fire exposure time on the temperature field and residual shear properties of RC beams, a simplified finite element (FE) model considering the effect of concrete spalling was developed. The accuracy of this model was validated through a comparison with experimental results. Finally, three theoretical methods for predicting the residual shear capacity of postfire RC beams with corroded stirrups were proposed, based on Chinese, American, and European codes. A comparison between the calculated and test results revealed a good agreement. These methods can provide conservative predictions for practical engineering applications. [ABSTRACT FROM AUTHOR]

Currently, the investigation on the collapse performances of steel frames with various structural scales has not formed a system resultant force, which leads to the current "overall qualitative and local quantitative" modes of structural system anticollapse resistance design. This paper numerically and analytically investigated the load-bearing capacities of the frame assemblies with various structural scales extracted from an overall steel frame structure subjected to the removal of an internal column. First, the accuracy of the numerical simulation methods was verified by comparing with the experimental results of the representative experimental collapse tests with various structural scales. Afterwards, numerical simulation analysis was conducted to investigate the variations in load-resisting capacities, axial forces generated in beams, and bending moments at beam ends in frame assemblies with different structural scales. The finding revealed that the boundary constraint is the one of the most critical parameters influencing the development of various load-bearing mechanisms, which is critical to identifying the internal links among the load-resisting capacities of assemblies with varying different scales. Finally, theoretical analysis methods for achieving the correlation transformation of the collapse capacities of steel frames with different structural scales were proposed, using member resistance based on the evolution laws of internal force among each story beam. The load-displacement curves generated by the display expression and its corresponding numerical models demonstrate a high level of accuracy, which demonstrates that the analytical methods can be employed for structural resistance evaluation before the anticollapse design. [ABSTRACT FROM AUTHOR]

The accurate representation of real floor behavior is crucial for assessing human-induced vibration serviceability. Many researchers focus on developing computational models and field testing to reflect actual serviceability conditions. Although traditional boundary conditions are commonly used, limited attention has been given to optimizing these conditions. To begin with, this paper introduced semirigid boundary conditions into a finite-element model of the floor and optimized physical parameters and boundary constraint stiffness using the simulated annealing-particle swarm optimization (SA-PSO) method, resulting in a more realistic computational model. Subsequently, a random crowd load model was established by combining the social force model (SFM) and the pedestrian load model, and a random crowd-floor mutual coupling calculation model was established based on the improved pedestrian biomechanical model. In addition, the mode shape functions of the floor with semirigid boundary conditions were obtained by extracting the optimized mode shape vector of the floor and using cubic spline interpolation. The dynamic response of the floor was computed using the modal analysis method, and the accuracy of the suggested method and model was verified by experiment. Furthermore, the effect on the vibration serviceability of the floor was analyzed under crowd walks randomly on the floor with different boundary conditions both before and after optimization. This study revealed: (1) achieving a computational model consistent with real floors requires optimization of relevant parameters and boundary conditions, reducing the error in floor frequency from 39.48% to 5.44% compared to measured results. (2) The human-induced vibration serviceability for existing floors may be misjudged by using traditional boundary conditions. The mean value of peak acceleration of floor with semirigid boundary conditions increased by 35.92%, with a 42% increase in the probability of serviceability problems compared to the SSCC boundary. (3) High-frequency floors also experience human-induced vibration serviceability issues. For a floor with a fundamental frequency of 10.3540 Hz, simulation and experimental results during five-person random walks indicate that peak acceleration at the middle position of the floor exceeds serviceability limits. [ABSTRACT FROM AUTHOR]

Cross-laminated timber (CLT) buildings are constructed by connecting CLT panels with dowel-type fasteners and mechanical anchors, which govern the lateral behavior of these structures. Although these connections are mostly distributed along the perimeter of the CLT panels, creating highly redundant structures, previous research on the lateral behavior of CLT structures has mainly focused on the behavior of the connections placed at the base of the CLT shear walls, such as hold downs and angle brackets, while limited attention has been paid to the connections between perpendicular walls and their effect on the lateral response of CLT shear walls. This paper presents a comprehensive experimental study aimed at investigating the effects of the interaction between perpendicular walls on the lateral response of CLT shear walls. CLT shear walls with three different aspect ratios were analyzed by means of monotonic and cyclic tests, both in single wall configuration and connected to perpendicular walls. The experimental findings demonstrate that the structural interaction due to the perpendicular walls significantly affects the lateral response of a CLT shear wall, resulting in increased lateral stiffness, lateral capacity, and deformation capacity. In addition, the study presents two analytical models for the prediction of the lateral stiffness and the lateral capacity of CLT shear walls connected to perpendicular walls. The analytical models were validated based on the experimental results, showing reasonable agreement. [ABSTRACT FROM AUTHOR]