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This paper presents an iterative sandwich beam theory (ISBT) and a simplified version suitable for the design termed simplified sandwich beam theory (SSBT) used to predict the elastic mechanics of partially composite insulated concrete sandwich wall panels (SWPs) under flexural, axial, and thermal loads. These solution methods expand upon closed-form solutions to create a more general analysis technique. Design and analysis of SWPs are handled largely outside of codified documents and are almost exclusively designed such that they will remain within the elastic range. The presented ISBT and SSBT methods have been used in the United States precast industry since 2017 and are implemented in widely available software, LECWall, as of 2020, for predicting elastic deflections and stresses. In this paper, the ISBT and SSBT solution methods are validated with experimental data from the literature and using finite-element analysis. For the ISBT cracking moment and deflection, the measured-to-predicted ratio were 0.99 and 1.0 with coefficients of variation (COVs) of 0.10 and 0.11, respectively. For the SSBT cracking moment and deflection, the measured-to-predicted ratio was 0.99 and 0.99 with COVs of 0.21 and 0.19, respectively. For thermal loading, the ISBT and SSBT deflection m easured-to-predicted ratios were 0.95 and 0.90, respectively. The model was then used to investigate the behavior of sandwich wall panels under varying load combinations and with various section and material properties to demonstrate the robustness of the presented methods. [ABSTRACT FROM AUTHOR]

Structural assessment and seismic vulnerability of ancient masonry buildings is a difficult task even when employing advanced specialized technical skills, which requires a complex study. This paper aims to assess the structural and seismic safety of the Esfahan Shah Mosque in Iran by numerically investigating the nonlinear behavior of the mosque for different scenarios and identifying if there is a correlation between crack patterns resulting from numerical analysis, inspection, and historical evidence. First, the numerical model of the mosque is developed and updated using the experimental parameters obtained from a nondestructive test (NDT) campaign that included ambient vibration and sonic testing. Second, the finite element calibrated model is used to evaluate the structural behavior of the mosque under vertical loading, including the influence of the soil and a sensitivity analysis varying the masonry material properties. Besides, the paper discusses the structural behavior of radial stiffening walls that connect the inner and outer domes of the mosque. Finally, pushover analysis was performed to assess the seismic safety of the building and the efficiency of the structural strengthening implemented in the early 20th century. The different technical observations and analyses lead to a better understanding of the double dome and the eyvan (a rectangular space, usually vaulted, walled on three sides, with one end entirely open) as the most vulnerable parts of the structure, which validates the structural strengthening of the 1930s. Yet, improving the connection between the stiffening walls and the two domes could effectively increase the global structural performance of the building. [ABSTRACT FROM AUTHOR]

Structural health monitoring provides a measurement-informed quantitative and systematic framework to better assess the state of fatigue in aging infrastructure. In this paper, a general methodology for probabilistic modeling of fatigue damage accumulation is presented from a structural health monitoring perspective, which allows for estimating the remaining fatigue life from strain measurements. The method presented uses a damage-sensitive feature derived from the Palmgren–Miner rule—a commonly used measure in fatigue analysis and design—as a surrogate for degradation and probabilistically models the process of degradation. A Bayesian approach is employed to estimate the parameters of this degradation model, and the remaining fatigue life is predicted using Markov chain Monte Carlo (MCMC) simulations. In the simplified case of constant stress amplitude, an analytical solution for the fatigue life has been derived. Moreover, techniques are presented to account for various challenges such as the lack of structural health monitoring data (SHM) for the initial unmonitored period and the absence of the continuous monitoring program. The main contribution of the paper is to develop a probabilistic degradation modeling framework using a damage-sensitive feature derived from the Miner rule for the prediction of the remaining fatigue life of critical bridge components. A numerical case study is presented to demonstrate the proposed methodology, and the major challenges of its implementation in the field are demonstrated through illustrations. [ABSTRACT FROM AUTHOR]

This paper, which is the second of two companion papers, presents the results of a large-scale testing program on a novel bridge column design, termed polyurethane (PU)-enhanced rocking column with energy dissipation (ED) links. The experimental program included cyclic testing of large-scale (approximately 1∶2.5) cantilever bridge columns, including (1) a rocking-only precast concrete column, which served as the reference column, (2) a PU-enhanced rocking column with a solid PU segment, and (3) a PU-enhanced rocking column with an axisymmetrically bilayered segment with an exterior PU layer to withstand seismic loads, an internal reinforced concrete core to sustain long-term gravity loads, and external ED links to provide energy dissipation and flexural stiffness and strength. The specimens were subjected to displacement-controlled lateral cyclic loading of increasing amplitude (exceeding a 10% drift ratio) at several drift ratio rates (up to 1 s−1). The tested PU column with ED links was further repaired via ED link release and retightening—the yielding of the ED links was small and did not justify replacement—to demonstrate its rapid reparability characteristics. The repaired column was subsequently retested to demonstrate that the original column properties had been practically recovered. This second companion paper experimentally quantifies the performance of all designs in terms of strength, ductility capacity, self-centering and energy dissipation capabilities, posttensioning losses, and ED link fracture capacity. It also quantifies the capability of ED link release and retightening (and, by extension, ED link replacement) in eliminating residual deformations and recovering the mechanical properties of the original/undamaged system. Compared to conventional RC rocking-only columns, the proposed PU-enhanced column design with ED links demonstrated higher energy dissipation and self-centering capabilities, while release and retightening of the ED links eliminated the residual deformations and resulted in the recovery of the mechanical properties of the original/undamaged column. While ED link release and retightening (i.e., ED link reuse) is adopted in this study, because the yielding of the ED links was small, as verified herein by the practically identical response of the original and repaired column, it can be deduced that ED link replacement (i.e., use of new/pristine ED links) would also restore the original column properties and eliminate residual deformations. [ABSTRACT FROM AUTHOR]

This paper, which is the first of two companion papers, investigates the performance of a novel bridge column design, termed polyurethane (PU)-enhanced rocking column with energy dissipation (ED) links, through a large-scale testing program. The proposed column design offers explicit damage control via damage-resistant end segments made of PU, ED and flexural strength/stiffness through ED links, and self-centering through internal unbonded post-tensioning. The PU segments have high deformability, allowing large lateral column deformations with negligible damage. The ED links are in the form of buckling-restrained bars made of high-performance steel and offer hysteretic damping and flexural stiffness and strength to reduce the seismically induced displacement demands. The experimental program included cyclic testing, at various loading rates, of large-scale (approximately 1:2.5) PU-enhanced cantilever rocking columns with two designs for the PU segment: (1) solid PU segment, and (2) axisymmetrically bilayered segment with an exterior PU layer to withstand seismic loads and an internal reinforced concrete core to sustain long-term axial service loads and provide resistance against creep. The specimens are subjected to displacement-controlled lateral cyclic loading of increasing amplitude (exceeding a 10% drift ratio) at several drift ratio rates (up to 1/s). A tested column is repaired via ED link release and retightening to demonstrate their rapid reparability characteristics and are retested to demonstrate the recovery of the original column properties. While ED link release and retightening (i.e., ED link reuse) is adopted in this study, because the yielding of the ED links was small as verified in the second companion paper by the practically identical response of the original and retrofitted column, it can be deduced that ED link replacement (i.e., use of new/pristine ED links) would also restore the original column properties. A rocking-only precast concrete column is also tested under the same loading protocols to serve as reference for comparisons. This first companion paper outlines the experimental program, quantifies the observed damage of the proposed column design for a range of seismic hazard intensities and compares it with that of the rocking-only column, and validates the capability of ED link release and retightening (and, by extension, ED link replacement) as a repair method that recovers the damage resistance/avoidance properties of the original system. Compared to conventional RC rocking columns, the proposed column design demonstrated significantly higher resistance against damage in terms of concrete spalling and crushing. [ABSTRACT FROM AUTHOR]

Complementing a companion paper that summarizes the building global response and physical damage of a midrise cold-formed steel (CFS) framed building during an earthquake and postearthquake fire test program, this paper focuses on understanding the seismic behavior of the shear walls utilized in the building system during this test program. In contrast to shear walls tested in an isolated configuration, the shear walls within the full-scale test building were constructed and tested under real-world kinematic constraints and dynamic loading environments. The shear walls located at various planar and vertical locations of the test building were instrumented with a dense array of analog sensors to monitor the shear wall local responses. In this study, the shear wall local responses are correlated with the global responses of the building to advance understanding regarding the behavioral characteristics of individual shear walls and in particular the interactions of the shear walls as part of the lateral-load-resisting system. Important seismic design parameters are inferred from the measured building response using a parameter optimization strategy. Their implications associated with the seismic design of CFS wall-framed structural systems are discussed in relation to code provisions and design guidelines. [ABSTRACT FROM AUTHOR]

To advance understanding of the multihazard performance of midrise cold-formed steel (CFS) construction, a unique multidisciplinary experimental program was conducted on the Large High-Performance Outdoor Shake Table (LHPOST) at the University of California, San Diego (UCSD). The centerpiece of this project involved earthquake and live fire testing of a full-scale 6-story CFS wall braced building. Initially, the building was subjected to seven earthquake tests of increasing motion intensity, sequentially targeting service, design, and maximum credible earthquake (MCE) demands. Subsequently, live fire tests were conducted on the earthquake-damaged building at two select floors. Finally, for the first time, the test building was subjected to two postfire earthquake tests, including a low-amplitude aftershock and an extreme near-fault target MCE-scaled motion. In addition, low-amplitude white noise and ambient vibration data were collected during construction and seismic testing phases to support identification of the dynamic state of the building system. This paper offers an overview of this unique multihazard test program and presents the system-level structural responses and physical damage features of the test building throughout the earthquake-fire-earthquake test phases, whereas the component-level seismic behavior of the shear walls and seismic design implications of CFS-framed building systems are discussed in a companion paper. [ABSTRACT FROM AUTHOR]

This paper focuses on the simulation of irregular stone masonry by the lattice discrete particle model (LDPM), which simulates the fracture and failure behavior of quasi-brittle heterogeneous materials by modeling the interaction among coarse material heterogeneities. LDPM is formulated at the length scale of the masonry stones whose interaction is described through constitutive equations featuring softening in tension and strain hardening in compression. The numerical results relevant to diagonal compression tests show that the intrinsic stochastic character of LDPM can quantify the variation of the mechanical properties of irregular masonry resulting from random stone size and stone-size distribution. Furthermore, the paper presents an analysis of the size effect on irregular stone masonry structures. This was obtained by simulating the shear behavior of geometrically similar samples of different sizes. The simulations demonstrate that increasing structural size leads to a significant reduction of both structural strength and structural ductility. The magnitude of the predicted size effect suggests that, contrary to typical experimental results on reduced size samples, real irregular masonry structures must be considered as perfectly brittle. [ABSTRACT FROM AUTHOR]

The number of studies on ultrahigh-performance concrete (UHPC) or ultrahigh-performance fiber-reinforced concrete (UHP-FRC) for more resilient and sustainable reinforced concrete (RC) structures has rapidly increased in recent years due to the superior mechanical and durability properties of UHPC. The application of UHPC as a replacement for conventional concrete materials in various RC elements necessitates a thorough understanding of the structural behavior of the reinforced UHPC (R/UHPC) components under various types of loadings. This paper presents a systematic review of the state-of-the-art developments in R/UHPC elements. It addresses various topics including beams, columns, beam–column joints, shear walls, bridges, structural retrofitting, and applications such as seismic and impact. Due to the ultrahigh tensile, compressive, and bond strengths, unique strain-hardening behavior, and ductility of UHPC, R/UHPC structures may exhibit substantially different behavior than conventional RC structures at both the component and system levels. This implies that particular attention must be paid when design and analysis approaches for conventional RC elements are applied to R/UHPC elements, and suggests that developing new design philosophies is warranted to take advantage of UHPC's unique mechanical properties. The present paper summarizes the developments in analysis and design approaches for R/UHPC elements under axial forces, shear forces, and bending moments, and highlights the advantages and limitations of these approaches. Important design considerations for effectively utilizing UHPC in structural elements are also suggested. In addition to normal-strength steel reinforcing bars, the potential for reinforcing UHPC with high-strength steel bars, fiber-reinforced polymer components, and structural steel shapes is discussed based on the results of pioneering studies. Finally, this paper identifies challenges and suggests future directions for research on UHPC in structural engineering. [ABSTRACT FROM AUTHOR]

Steel-concrete composite columns are strong and efficient structural members. However, their strength is not consistently recognized within design standards. In particular, current provisions regarding the strength of composite columns under combined axial compression and biaxial bending are overly simplistic and conservative. This paper presents a study of the biaxial behavior of square and rectangular, filled and encased composite columns and methods of evaluating their strength. Analyses of composite cross sections confirm the conservative nature of current design provisions and form the basis for modified strength equations that better capture the shape of the three-dimensional interaction surface. Analyses of composite columns confirm that the proposed design equations are suitable for use within the direct analysis method for evaluating members with length effects. The proposed design equations are further validated against published experimental results. This paper provides key insights on the behavior of composite columns subjected to axial compression and biaxial bending and offers an improved yet practical method of evaluating strength under these conditions that will enable more efficient designs. [ABSTRACT FROM AUTHOR]

Calls for nominations for the American Society of Civil Engineers (ASCE) and Structural Engineering Institute (SEI) awards. Aim to advance the engineering profession by emphasizing exceptionally meritious achievement; Requirements to comply in giving nominations; List of the different ASCE and SEI awards.

It is understood that the discussers focused on the finite-element modeling approach described in the paper that was used to support the development of shear strength equations for composite circular concrete-filled steel tube (CFST) members. Their claim that the shear response of CFSTs cannot be modeled using the Winfrith concrete model is based on comparing the results for these two specimens using the CDPM and Winfrith material models with test data. It can easily be shown that the plastic shear strength of a thin-walled circular hollow steel section ( HT ht ) [per Eq. (15) neglecting HT ht ] is 1.22 times its first yield shear strength ( HT ht ). [Extracted from the article]

The noncompact web-slenderness limit in current design specifications is based on an assumed value of the plate buckling coefficient for a web subjected to flexure that is between the values for fixed and simply-supported edge conditions. While the limit provided in current specifications is a good representation in many situations, there is evidence that the limit overestimates the magnitude of the restraint provided by smaller flanges. This paper shows that the ratio of the area of the compression flange to the area of the web in compression is a good indicator of the restraint provided to the bend-buckling of the web plate. The overestimation of the plate buckling coefficient can result in the classification of cross sections having relatively small flanges as noncompact web sections when their behavior is more akin to that of slender web sections. Slender web sections have a maximum possible flexural resistance, referred to as the plateau strength, less than the yield moment Myc, because of load shedding from the web. Furthermore, the St. Venant torsional stiffness contribution to the lateral torsional buckling resistance is neglected for these sections due to web distortional flexibility. This paper evaluates the appropriate noncompact web-slenderness limit via test simulation of a targeted set of short girder specimens in which the calculated resistance is governed by the plateau strength and proposes a modified equation to rectify the problem. The impact of this change on the prediction of a broad range of member limit states is illustrated via comparison to other test simulations and to experimental results. [ABSTRACT FROM AUTHOR]

The lateral torsional buckling (LTB) equations in some current standards are based on unified equations that are a fit to a large body of experimental test data. However, these curves tend to overestimate the capacities from finite-element (FE) simulations based on typical idealized end conditions, residual stresses, and geometric imperfections. Uniform moment tests conducted on various types of cross sections have led to proposed modifications of the current specification for LTB equations. This paper investigates and recommends, by means of FE test simulations, the use of the modified equations with additional improvements for moment gradient cases. The emphasis of the studies is on rolled I-section members. Specifically, the paper demonstrates an inelastic Cb effect that can be particularly significant for beams in which the maximum moment occurs within the unbraced length rather than at a braced point. A new way of applying the LTB modification factor, Cb, in the inelastic LTB region for these cases is recommended for ordinary application of current standard resistance equations. Also, it is shown that this effect can also be captured seamlessly via an explicit inelastic buckling analysis using stiffness-reduction factors (SRFs) derived from the design resistance curves. [ABSTRACT FROM AUTHOR]

The objective of this paper is to employ the results from the extensive instrumentation installed on recently tested full-scale cold-formed steel (CFS)-framed buildings to reveal a deeper understanding of the behavior of the building under seismic excitations. In particular, this paper complements a companion paper that focuses on system-level design and response. Here, utilizing strategically located string potentiometers, strain gauges, and accelerometers, the responses of the walls and diaphragms are isolated from the overall building response and studied. The interaction of shear walls along a wall line, as well as across stories is studied through measured data on strains in hold-down anchors, strains on floor-to-floor strap connecting shear-wall chord studs, and displacements across shear-wall sheathing and openings. The behavior of the floor diaphragm is studied through displacements measured perpendicular to the plane of one wall of the building and accelerometers throughout the floor of the building. The results serve to highlight the subsystem-level outcomes that accompany the complex system-level response as CFS-framed buildings undergo seismic excitations. [ABSTRACT FROM AUTHOR]

This study is concerned with the strength limit state of serial bolted connections in structural steel plates. It points out that the ultimate load capacity of a serial bolted connection failing in combined bearing and shear-out cannot be computed as the simple sum of the respective ultimate bearing and ultimate shear-out capacities, which is implicitly permitted in design specifications worldwide. Based on the laboratory test results of 10 hot-rolled steel plate specimens composed of three different grades with nominal thicknesses ranging from 5 to 8 mm, the paper first establishes the ultimate bearing coefficient of a 20-mm bolted connection in a structural steel plate to be 3.5. Coupled with the shear-out equation previously derived, a design equation where the shear-out capacity of the downstream bolt varying quadratically with the end distance is then proposed to determine the combined bearing and shear-out capacity. The proposed equation is demonstrated through verification against independent laboratory test results involving 5-mm plates of three different grades to be significantly more accurate than the simple sum. Explanation for the unexplained results obtained by another researcher using his own equation is provided in this paper. [ABSTRACT FROM AUTHOR]

This paper analyzes the wind pressures on the claddings of a 600-m-high skyscraper in Shenzhen, China, during Super Typhoon Mangkhut on September 16, 2018. A synchronous monitoring system that included 48 pressure transducers was implemented to measure the cladding pressures of the skyscraper during the typhoon event. Based on field measurements, the mean, root-mean-square fluctuating, peak (maximum and minimum) pressure coefficients are presented and discussed. Then the mean and peak pressure coefficients are used to validate the design values stipulated in the design code of China. Comparative study finds that the design values of the peak pressure coefficients on the windward and leeward faces of the skyscraper are conservative, while those on the side faces are nonconservative. As for the mean pressure coefficients, the design values are conservative for all faces. Moreover, the non-Gaussian characteristics, power spectral densities, coherences, and correlations of the measured cladding pressures are analyzed to explore the mechanisms of pressure fluctuations on the four sides of the skyscraper. This paper aims to enhance understanding of cladding pressures of high-rise buildings under extreme wind conditions and, therefore, to provide useful information for future designs of wind-resistant skyscrapers in tropical cyclone–prone regions. [ABSTRACT FROM AUTHOR]

Due to the high in-plane stiffness and strength capacity of cross-laminated timber (CLT) panels, the mechanical behavior of CLT shear walls is mainly influenced by the mechanical performances of the connections. Several calculation models have been proposed considering the mechanical anchors effectiveness only along their primary direction. However, recent studies showed a relatively high stiffness and capacity of new typologies of angle brackets when subjected to uplift vertical loads, such as for the wall-to-floor Titan V (TTV) angle bracket, developed to obtain high mechanical performances along both the vertical-tensile and horizontal-shear direction. In this paper a study on CLT shear walls anchored with TTV angle bracket is presented. The aim of the work is to investigate the effects of the coupled shear-tension behavior of the connections at the wall level and the effectiveness of TTV as an alternative to traditional mechanical anchors. The paper presents results from full-scale experimental tests and finite-element (FE) numerical analyses in SAP2000, where an innovative macroelement has been developed to model the TTV coupled shear-tension behavior. The effects of the plastic load redistributions of the TTV angle bracket on the global mechanical behavior of the CLT shear wall are discussed. [ABSTRACT FROM AUTHOR]

Light-timber frames, using plywood (PW), exhibit a pinched hysteresis response, and their energy absorption capacity is limited. The energy-dissipation capacity can be enhanced using energy-dissipation mechanisms. In this paper, two wood-friction-based connectors, with wood-plywood-wood (WPW) and wood-steel-wood (WSW), are utilized. Reverse-cyclic static load tests have shown that the WPW and WSW wall systems have nondegrading and stable hysteretic curves. In this paper, through shake-table tests, performance of WPW, WSW, PW, and WSW-PW coupled wall systems are investigated. As expected, the shake-table results indeed showed nondegrading hysteretic curve responses of WPW and WSW wall systems. Furthermore, a phenomenological model, where nonlinear behavior of the shear wall is reduced to a single spring element, is proposed for the wall systems. The nondegrading wall system (WPW, WSW) is modeled using the Bouc-Wen hysteretic model and the PW is modeled using the Pinching4 hysteretic model. Overall, there is good agreement between the test and analytical models. Results of the experimental test indeed show the utility of the new wall systems. [ABSTRACT FROM AUTHOR]

In detailed three-dimensional (3D) finite-element modeling, two-dimensional and/or 3D elements are widely used because of their high accuracy and ease of use despite the high computational cost. In contrast, simplified modeling based on fiber beam element (FBE) formulation is preferred for developing macro models to simulate structural frames due to its simplicity and computational efficiency. As for the FBE simulation of concrete-filled steel tubular (CFST) columns, its accuracy largely depends on the input steel and concrete material models, which should implicitly consider the material nonlinearity and interaction between the steel and concrete components. The authors have previously developed a FBE model for circular CFST columns, and this paper is a continuation of the previous work. In this paper, uniaxial effective stress–strain relationships are developed for the steel and concrete materials in rectangular CFST columns based on rigorous analysis of data generated from 3D finite-element modeling of stub columns. Thus, the material models have implicitly considered the effects of yielding and local buckling of the steel tube and passive confinement to the concrete. Meanwhile, the size effect is also considered in the concrete model. The accuracy of the proposed material models is verified against a database of rectangular CFST stub columns covering a wide range of material and geometric parameters. The developed material models are further used to simulate rectangular CFST slender columns and beam-columns, and a reasonably good agreement is achieved between the experimental and predicted load–deformation curves. [ABSTRACT FROM AUTHOR]

This paper investigated the potential applicability of the specification equation for the shear pull-out strength of a power-actuated fastener (PAF) connection to nail connections between steel sheets thinner than 2.9 mm. The tested G300, G450, and G550 specimens had thicknesses ranging from 0.6 to 2.4 mm, connected with 2.5- or 3.6-mm helically knurled nails. The pull-out strength is a function not only of the thickness of the member not in contact with the fastener head, but also of the other member's thickness. The member thicknesses have greater influence than the nail diameter on the pull-out strength, contrary to the design equation. Based on the test results of 93 shear nailed connections failing in pull-out, the paper proposes a design equation that is applicable to connections using helically knurled nails of steel sheets thinner than 2.9 mm. A group effect factor of 0.75 is suggested for serial nail connections based on the test results of 19 multiple nail connections. A resistance factor of 0.55 is recommended for use with the proposed equation for determining the pull-out strength of shear nailed connections in thin steel sheets. An additional finding is that the current design equation for the bearing and tilting strength of a PAF connection is applicable to connections in which the member not in contact with the fastener head is much thinner than the specification minimum of 3.2 mm, and in which the fastener diameter is smaller than the specification minimum of 3.7 mm. [ABSTRACT FROM AUTHOR]

This data paper presents the experimental investigation of unconfined cold-formed steel double-shear bolted connections where the applied load was stopped at different stages of loading (25% or 65% of the ultimate failure load under monotonic loading) followed by unloading, and finally reloading until failure. A total of 78 bolted connections of cold-formed steel subjected to loading–unloading and reloading conditions with sheet thicknesses ranging from 0.55 to 3.0 mm, bolted with 10, 12, or 16-mm bolts were investigated and compared to the identical specimens subjected to monotonic loading. The failure mode of the specimens tested under both loading conditions was bearing of the inner sheet. The test results show that ultimate capacities obtained from unloading and reloading tests were, on average, lower than those obtained from the monotonic tests. A similar trend was also observed for the displacement corresponding to the ultimate loads. However, the effects of sheet thickness and bolt diameter were found to be less critical. This study establishes a publicly available database of control cases to build the foundation for further study into similar loading regimes. This paper also alludes to several potential use cases for the available data. [ABSTRACT FROM AUTHOR]

To satisfy the easy-repair demands of precast concrete (PC) frames after an earthquake, a PC frame with replaceable artificial controllable plastic hinges (ACPHs) is proposed in this paper. ACPHs were installed at each beam end on both sides of the frame, which concentrated the structural deformation to avoid any damage of precast reinforced concrete members. In this study, to explore the seismic behavior and ACPH location factor on the seismic performance of the frame structures, cyclic loading tests were conducted on two precast concrete frames with different positionings of the ACPH and cast-in-situ frame. The test results indicate that the ACPH frame exhibited favorable seismic performance, and the bearing capacity and energy dissipation capacity can be improved by appropriately extending the distance from the ACPH to the cylinder. Based on the principle of maximizing the elastic range resistance of precast reinforced concrete beams, the formulas for calculating the optimal locations of ACPHs were established. [ABSTRACT FROM AUTHOR]

Application of fiber-reinforced polymer (FRP) composites in the strengthening of reinforced concrete (RC) structures has become an increasingly accepted engineering practice. In particular, the use of externally bonded FRP wraps as a confining material for concrete can enhance both the compressive strength and the ultimate strain of concrete, making it suitable for strengthening and/or seismic retrofit of existing RC columns. This paper focuses on a recently developed analysis-oriented iterative FRP-and-steel confinement model for concrete and proposes a new optimization procedure to obtain an analytical expression for the corresponding monotonic envelope, reduce the associated computational cost, and increase the corresponding numerical robustness. Several analytical functions were evaluated in terms of their capability to fit the iteratively-generated stress-strain monotonic envelope for confined concrete. The newly proposed analytical formulation of the confined concrete stress-strain model was compared with the original iterative formulation in terms of computational cost for two examples of nonlinear seismic response analyses for: (1) an experimentally-tested concrete-filled FRP tube bridge column of a two-column bridge pier; and (2) a five-span bridge structure with FRP-retrofitted RC piers. It is found that the use of the newly proposed optimization-based analytical monotonic envelope can reduce by more than 30% the computational time associated with the original iteration-based monotonic envelope with negligible changes in the structural response prediction at both global and local levels. [ABSTRACT FROM AUTHOR]

This paper presents an in-situ study of imaging cracks in the Berwick Bay Bridge nondestructively by the application of an inverse algorithm to ultrasonic coda wave measurements. Using only five sensors to collect coda signals, we have monitored a 100×70×33 cm3 volume of the bridge subjected to a sequence of static load tests, without prior knowledge of cracks. Whereas spatiotemporal waveform decorrelations can indicate global damage conditions, our inversion algorithm produced a three-dimensional map of change density that revealed the location and lengths of multiple 0.1-mm-scale cracks in reinforced concrete. [ABSTRACT FROM AUTHOR]

Poor earthquake response in suspended ceilings can cause wide-scale injuries and financial losses, which underscores the need to understand such systems better. This paper presents a study on a plasterboard suspended ceiling system (PSCS) installed in a 3.00-m tall steel building. The PSCS is an assembly of a plasterboard with plan dimensions of 2.69 m×2.27 m attached to a horizontal metal frame suspended from the roof. The building was subjected to Taft motion in the principal horizontal directions. The peak input accelerations ranged between 0.05g and 0.25g (0.05g and 0.70g) in the short–edge (long-edge) direction; the natural period of the PSCS increased from 0.91 to 0.99 s (0.32 to 0.99 s) during the tests. The peak plasterboard acceleration ranged between 1.1 and 2.4 times the peak roof acceleration (except during impact). Damage was observed primarily in the suspender struts near its lower end, attributable to the "rigid" connection between strut and horizontal metal frame. Response of the PSCS in the "softer" direction was greater and more sensitive to the response of the superstructure compared to the orthogonal direction. Static tests on the joint between the suspender and the roof of the building provided information for the development of the numerical model. Separate models were developed for the two principal horizontal directions due to different degradation characteristics. An ambient damping of 2% in the numerical model (experimental value was 8%) led to a much better simulation in the "softer" direction, indicating that damping during "large-amplitude motions" can be considerably less than that during "low-amplitude motions." [ABSTRACT FROM AUTHOR]

The capability of the wave method for structural health monitoring, based on fitting a layered Timoshenko beam by waveform inversion of impulse responses, to localize damage is investigated using shake table experiment data. The specimen is a full-scale slice of a seven-story reinforced concrete (RC) shear wall building, which was tested on the University of California San Diego–Network for Earthquake Engineering Simulation (UCSD-NEES) outdoor shake table under consecutive exposure to four earthquake motions with increasing intensity, which progressively damaged the structure. The damage is localized by partitioning the beam into horizontal layers, comprising a single floor in the parts with the most severe damage and a group of floors in the lightly damaged parts, and detecting changes in the wave velocities in each layer with respect to a reference state. Small amplitude, ambient vibration response data were used as input for the inversion. The paper describes a number of improvements in the methodology, which were necessary to improve the quality of the inversion, the success of the method to detect the existence and the intensity of the damage in different parts of the structure, and how it fared in comparison to other methods applied to the same test structure. Also, recommendations are proposed for future improvements of the method. [ABSTRACT FROM AUTHOR]

Rebar cages are commonly used in reinforced concrete constructions. These cages consist of longitudinal and transverse reinforcing bars usually connected by tie wires. Numerous incidents of rebar cage failure and collapse have been reported at construction sites, often leading to injuries, fatalities, construction schedule delays, and added costs. Using mechanical connectors such as U-bolts instead of tie wires can improve stability and strength of rebar cages. This paper aims to investigate the mechanical behavior of U-bolt connections through experimental tests and to explore the potential application to rebar cages through analytical models. Experiments were conducted on U-bolt connectors to determine the force-deformation response behavior in different degrees of freedom and for different rebar conditions. Then, the data obtained from a previously completed experimental study on a full-scale tie-wired rebar cage were used to develop and calibrate a nonlinear finite-element model of the test specimen. The force-deformation response of U-bolt connections was then included in the model, replacing the tie wires, to investigate the effect of mechanical connectors on the lateral stiffness and strength of the rebar cage. The results showed that application of mechanical connectors for cross-bar connections in the rebar cages can increase the lateral strength of rebar cages, rendering U-bolt connectors as a potential solution to improve stability and safety of rebar cages. [ABSTRACT FROM AUTHOR]

In determining wind loads when designing buildings—especially high-rise buildings—wind speed is a critical factor. With increased progression of city high-rise construction, accurate prediction has become ever more important. Many factors, such as local climates, roughness of surrounding conditions, and terrain, may affect wind speed. But among all factors considered, terrain has a very large influence. Difficulties in reflecting the influence of terrain on wind speed include (1) collecting topographic data information; (2) quantitatively evaluating terrain features; and (3) expressing specific area relationships with surrounding observation stations. This paper poses means to solve these limitations by (1) using satellite imagery to gather topographic information; (2) evaluating terrain quantitatively with convolutional neural network (CNN)–based encoders; and (3) employing a graph neural network (GNN) to estimate the wind speed relationship of an arbitrary place to that of observation stations. Herein, a machine learning model utilizing the aforementioned means was proposed. To support this model, an experiment was conducted using observed wind speed data in Korea. Throughout the experiment, previous studies were used to compare results with ratification of the posed model. Given the submitted findings, further research and investigation to establish correlation with other experimental case results are proposed. [ABSTRACT FROM AUTHOR]

Damage of shear connectors in steel-concrete composite (SCC) beams affects the composite action and appears as abnormalities in the shear slip between the composite components. The shear slip at the composite interface causes nonlinearity in the global composite beam response which is an issue beyond the inherent complexity of the composite system. This paper presents a novel approach for damage detection of SCCs by variational mode decomposition (VMD) of shear slip data. Numerical and experimental studies were conducted on steel-concrete composite beams to generate noise-contaminated shear slip data from undamaged and damaged states of the structure. The VMD algorithm is employed to decompose shear slip signals into intrinsic mode functions (IMFs) and then, the center frequency of each mode is captured. The higher center frequency realized in the second mode is taken as a damage sensitive feature. Because IMFs curves are extracted from the signal splines interpolated between the average of the peaks and troughs, the change of energy in the center frequencies of the undamaged and damaged states can be defined as a damage index. Welch power spectral densities of the IMFs are calculated to further investigate changes in the center frequencies of IMFs obtained using the VMD algorithm. The empirical mode decomposition (EMD) technique is also utilized to decompose shear slip signals into IMFs for comparison purposes. The results show that the EMD is not able to detect abnormalities in the shear slip signals affected by damage because of losing information through several mode decompositions and a phenomenon termed mode mixing. However, when the VMD was set to decompose the signal into two IMFs, it was found that it is more efficient in maintaining the frequency content of the shear slip signal. According to the results, the proposed method has been proved successful in detecting damage of composite beams and can be employed as a reliable and robust technique. [ABSTRACT FROM AUTHOR]

This paper presents a case study of a realistic application and evaluation of a promising structural health monitoring approach that exploits some topological features of building-like structures to develop a reduced-order, reduced-complexity, not-necessarily-linear, substructure model. The approach not only reliably detects the occurrence of anomalous features that can reflect incipient damage and deterioration but also provides the locations of the structure's regions where a single or multiple changes have been detected. The target structure used in this study is a 52-story building in Los Angeles that is instrumented with a relatively dense sensor array and is being continuously monitored through the efforts of the community seismic network (CSN). Two qualitatively different system identification approaches (global and substructuring) are applied to the large data set of ambient acceleration measurements produced by a strong wind event ("Santa Ana winds") to identify the dominant modal characteristics of the building. The results are shown to match the corresponding results from a high-resolution computational model of the building based on a widely used structural analysis software package (ETABS) developed by Computers and Structures, Inc. The main contribution of this study is to demonstrate the practical feasibility of the proposed substructuring approach with a high-order system using both wind and low-amplitude ambient vibration measurements. The approach also assesses the accuracy and reliability of the estimates of the dominant modal features of the structure to subsequently provide a probabilistic measure of confidence in the extent and location of changes if an anomaly is detected. Due to the minimal computational resources needed to implement the proposed substructuring approach, it is efficient for near-real-time applications where important structures need to be continuously monitored for sustainability as well as resiliency requirements. The method is applicable to linear, nonlinear nonhysteretic, and hysteretic systems, with no restriction on the source of the signal for identification purposes. [ABSTRACT FROM AUTHOR]

This paper presents the experimental results from nine full-scale concrete-filled double-skin tubular (CFDST) beam-columns. The test specimens exploited two fabrication strategies, featuring either hollow steel inner skins with corrugated geometry or ultrahigh-strength steel corner tubes to enhance the seismic performance of noncompact CFDST beam-columns for potential use in low-to-moderate seismicity regions. The effects of loading sequence, axial load ratio, and cross-sectional geometry were investigated. The experimental results suggested that the current AISC specification may be used to predict the axial strength of composite members with a relatively good accuracy. In the postbuckling range, conventional CFDST beam-columns and those with corrugated inner skins are prone to fracture at the corner welds of the built-up cross section. However, the latter exhibited up to two times larger drift capacities than conventional CFDST counterparts prior to losing axial load carrying capacity. Noncompact beam-columns retrofitted with ultrahigh-strength steel corner tubes exhibited a 4% lateral drift demand without experiencing more than 25% flexural strength loss. The presence of ultrahigh-strength steel increases the plastic hinge length of CFDST beam-columns by up to four times relative to CFDST beam-columns with corrugated inner skin, regardless of the employed loading history. [ABSTRACT FROM AUTHOR]

Endplate moment connections with shape memory alloy (SMA) bolts provide self-centering for the seismic resilience of structures. Predicting the self-centering response of these new beam–column connections, which have not been codified yet, requires conducting experimental tests or detailed continuum finite-element simulations. Computationally efficient predictive tools are needed to facilitate the analysis, design, and assessment of self-centering connections and moment frames. In this paper, artificial neural networks (ANNs) are used to develop a MATLAB tool for predicting the moment-rotation backbone and self-centering response of extended endplate connections with SMA bolts. As the input for the neural networks, the predictive model development employs a design database of response parameters from 72 finite-element (FE) models and experimental tests of seven beam–column connection specimens. Neural networks are trained for seven response parameters, and the trained networks are used to develop a graphical user interface (GUI). The coefficient of determination for the trained ANNs is in the range of 0.92 to 0.99, indicating acceptable prediction accuracy. Furthermore, optimization studies using a multiobjective genetic algorithm are performed, seeking the minimization of material use (steel and SMA) and improved connection-response characteristics (i.e., stiffness, strength, and ductility). A phenomenological model of SMA connections is also developed in OpenSees. The use of the ANN-based predictive tool for accurate and efficient modeling of SMA-based connections and self-centering moment-resisting frames is illustrated. The computation time for predicting the moment-rotation response of a typical SMA connection is significantly reduced from seven hours in ANSYS to only three minutes in OpenSees while providing the same level of response prediction accuracy. Furthermore, the optimization results are confirmed by performing nonlinear pushover and response history analyses. [ABSTRACT FROM AUTHOR]

This paper presents experimental testing on glulam beam–column moment-resisting connections using glued-in rods (GiRod) and compares the results with model predictions. Three connection geometries and varying numbers of rods and member size were tested and compared. This experiment will be helpful in grounding research by bringing in new experimental results and proposing an innovative experimentation method. Experimental results showed the high efficiency of glued-in rod connections to transfer loads and bending moment between spruce pine glulam timber members. The observed limit states of the connections were failed steel rods in ductile tensile yielding or wood splitting around the anchorage installed perpendicularly to the grain in the column. It was found that the tested connections behaved as a semirigid moment-resisting connection and exhibited a ductile failure mode when wood splitting was avoided by design. Comparison of experimental results with model predictions showed good agreement, with a deviation under 15% for the moment capacity of the connection. [ABSTRACT FROM AUTHOR]

Peridynamics (PD) has been increasingly used to study the damage behaviors of reinforced concrete (RC) structures due to its strong capacity in analyzing discontinuous problems. In this paper, bond-based peridynamics (BPD) is enhanced for refined analysis of bond-slip behaviors between concrete and ribbed steel rebar in the pullout test. The enhancement of BPD includes the following: (1) an axial-shear interaction (ASI) model for refined simulation of bond-slip behaviors between steel ribbed rebar and concrete; (2) a nonlinear uniaxial concrete model to avoid excessive compression of concrete bonds; (3) a novel gradually weakening fictitious element (GWFE) approach to improve the stability and convergence of the Newton algorithm in solving the PD equations, e.g., in case of negative concrete stiffness; (4) a horizon updating approach for rebuilding bond interactions when large displacements occur in the bond-slip process; and (5) a parallel computing approach to improve the computational efficiency of refined analysis. The enhanced BPD method is implemented in an open-source finite-element software, OpenSees, and verified by a rebar pullout test. The type of steel rebar rib, strength of concrete, cross-area of steel, and cyclic loading condition are investigated in detail regarding their effects on the stress redistribution and mesoscale crack propagation of the RC members. The results demonstrate that the enhanced BPD modeling method presented herein is capable of fine simulation of bond-slip behaviors in the pullout test, e.g., the strength deterioration, stiffness degradation, and cyclic response. [ABSTRACT FROM AUTHOR]

This paper uses nonlinear analysis to determine the impact of corrosion-induced damage on the load-carrying capacity of prestressed concrete bridge girders. The analyses rely on two types of models, namely, beam models and nonlinear truss models. The latter are deemed necessary to obtain reliable estimates of the shear capacity, as beam models are not well-tailored for capturing shear failures. A procedure to account for the reduction in area and deformability of corroded strands, based on visually observed corrosion damage, is proposed and implemented. The models are calibrated and validated with the results of experimental tests on prestressed girders, which exhibited varying levels of corrosion-induced damage. Further analyses allow the comparison of the capacity of corrosion-damaged girders to that of their undamaged counterparts. The accuracy of a simplified procedure, using equations in the AASHTO code to determine the flexural and shear capacity of the damaged girders, is also determined. [ABSTRACT FROM AUTHOR]

This paper presents the evaluation of two methods for manually estimating the elastic lateral-torsional buckling (LTB) resistance of general doubly and singly symmetric I-section members having a linear variation in the web depth. The study focuses on unbraced lengths having idealized torsionally simply supported (fork) end conditions. The first method uses cross-sectional properties at the midspan of the unbraced segment along with a moment gradient modifier equation, written in terms of the flange stresses, to develop its strength approximation. This approach is employed in the first edition of the AISC-MBMA Design Guide 25 (DG 25). The second method is an extension of an approach that has been shown to be accurate and efficient for prismatic doubly and singly symmetric I-section members and is recommended in the second edition of DG 25. This approach uses cross-sectional properties at a critical section within the unbraced length, defined as the cross section where the ratio of the moment demand to the base LTB resistance in uniform bending is maximum, along with a moment gradient modifier equation written in terms of the above maximum ratio and the corresponding ratios at the quarter points of the unbraced length. Furthermore, Method 2 employs an additional calibration factor that accounts for an apparent destabilizing effect of the inclination of the shear center with respect to the axis of torsional restraint. The predictions from these methods are evaluated by an extensive parametric study encompassing the full design space for I-section members with linearly-varying web depth, as defined by DG 25. The second method is shown to provide improved accuracy, avoiding undesirable nonconservative errors in certain situations. The calibration factor developed as part of the second method is shown to eliminate undesirable errors in the first method as well, providing streamlined and accurate buckling estimates for linearly tapered member unbraced lengths. [ABSTRACT FROM AUTHOR]

The paper studies the flexural responses of one-way reinforced concrete structural elements subjected to cased explosive charges to explore the suitability of using high-strength materials for such scenarios. The detonation of cased explosive charges leads to the generation of fragments due to the rupturing of the casing housing the high explosive charge. Consequently, structures subjected to the detonations of cased explosive charges are acted upon by both the blast wave (due to the detonation of the high explosive charge) and the fragments. This study was motivated by the fact that although similar studies have been conducted to explore the suitability of using high-strength materials for scenarios involving bare (uncased) explosive charges, such studies are still uncommon when it comes to cased explosive charges. The methodology adopted herein consisted of developing a semianalytical approach that was validated against (1) the results of experimental static tests available in the literature, (2) the results of experimental blast trials conducted with bare (uncased) explosive charges that are available in the literature, and (3) the results of finite-element simulations, conducted by the authors due to the nonavailability of a relevant experimental data set in the public domain pertaining to cased explosive charges (to the best of the authors' knowledge). Following the validations, the adopted semianalytical approach was further used for conducting detailed parametric investigations. It was observed that compared with the lightly cased explosive charge (casing to charge mass ratio=0.5), the peak structural displacements for the heavily cased explosive charge (casing to charge mass ratio=1.5) showed an increase of 50% (for high-strength materials) to 64% (for normal-strength materials). Moreover, compared with normal-strength materials, the application of high-strength materials was also noted to reduce the peak structural displacements by 9% to 23%, which indicated the increased measure of safety provided by the high-strength materials. In addition to this, compared with normal-strength concrete, the employment of high-strength concrete grades was also effective in limiting the fragment inflicted damage by 25% to 36%. Additionally, increasing the reinforcement ratio to 0.65% from 0.16% effectively reduced the peak structural displacements by 57% to 63%. [ABSTRACT FROM AUTHOR]

It is known that the performance of traditional passive tuned mass dampers (TMDs) is highly sensitive to vibration frequency. The fundamental frequency of existing tall buildings may shift to lower value due to damage or other reasons. In this regard, this paper deals with the resultant detuning problems of a traditional passive TMD for vibration control by retrofitting it with a passive adaptive negative stiffness device (NSD). The applied NSD not only provides negative stiffness for adjusting the TMD's de-tuned stiffness at its working stage, but also offers a fail-safe limiting stop for the TMD at large deformation/stroke. In this study, compared to the original TMD, a novel TMD-NSD assembly is proposed that is shown to be more effective for serviced structures. For example, the original TMD can only provide about 2.83% additional damping ratio to frequency-changed structures, while the newly proposed TMD-NSD further improves the damping ratio to 5.34%. Moreover, in the study it is found that the TMD-NSD also outperforms the TMD in resisting dynamic lateral loading such as along winds, cross winds, and earthquakes. [ABSTRACT FROM AUTHOR]

The choice of spectral targets for ground motion selection has a strong impact on structural demands resulting from nonlinear time history analysis. In particular, the conditional mean spectrum (CMS) has been recognized as an appealing alternative to the uniform hazard spectrum (UHS) as a spectral target due to the former's more realistic shape and reduced conservatism. Using a tall building case study in a high-seismicity region, this paper evaluates the building demands generated by UHS- and CMS-based selection procedures. Theoretically rigorous implementation of CMS-based selection using 17 different conditioning periods is shown to reduce maximum considered earthquake (MCE)–level demands on the case study building by 9%–35% relative to UHS-based selection. Furthermore, the simplified CMS-based procedure in the building code with apt choice of only two conditioning periods is found to satisfactorily capture the demands generated by the theoretically rigorous approach. Findings also highlight the degree of sensitivity of CMS-based results to the choice of conditioning periods and to enforcement of lower bounds on spectral targets, such as 75% of the UHS. The presented analysis procedure can be replicated in future studies for explicit evaluation of simplified CMS ground motion selection in other structural systems or analysis cases. Since its introduction to the building code, the alternative, conditional mean spectrum-based method for ground motion selection has gained traction among practitioners due to its reduced conservatism relative to traditional selection methods. To simplify the implementation of conditional mean spectra in practice, the building code alternative method requires a minimum of only two target spectra be used, so long as their envelope satisfies a lower bound within a specified period range. However, there are few quantitative studies of the impacts of these simplifications on the resulting building demands. In this study, we demonstrate how building demands vary when a tall building in a high-seismicity region is analyzed using either a traditional or a conditional mean spectrum-based selection approach. We find that using two reasonable target spectra in accordance with the alternative method produces acceptable building demands as compared to the demands obtained from performing exhaustive nonlinear analysis with a large number of target spectra. Furthermore, we illustrate how different choices of conditional mean spectrum targets maximize different types of building demands (e.g., interstory drift, base shear, floor acceleration) and how some types of demands are more sensitive to this choice than others. This work provides a procedure for evaluating conditional mean spectrum-based ground motion selection that can be replicated in the future for other buildings or structural systems. [ABSTRACT FROM AUTHOR]

From the post-war period to present day, economic development and urbanization have led to various demands for infrastructure, including bridges and viaducts. However, especially in recent years, there have been reports of sudden and unexpected collapses of bridges and viaducts, associated with large economic losses and, unfortunately, loss of human lives. The study of the causes that have led to these disasters is of strategic importance because it allows for the deepening of the specific technical knowledge. For this reason, this paper presents the study of the causes that led to the collapse of one of the spans of the "La Reale" viaduct in the Piedmont region in Italy. The main reason for the collapse was to be found in the incorrect injection of cables, which led to the absence of grout inside the sheaths for a length equal to one third of the deck. In this region, cables were subjected to a highly aggressive environment with severe corrosion. This resulted in fragile failure of the deck, with no signs that could suggest such important structural problems during normal inspection operations. The only evidence was some white efflorescence. However, in light of the knowledge prior to the present study, this evidence could not be easily connected to the type of phenomenon in progress that led to the collapse. Based on the experimental tests carried out on the collapsed portion, this study highlights new symptoms not associated with any structural pathology previously studied. The main concern relative to the structural safety assessment in cases such as the one presented in this study is related to the lack of evidence on the current state of cable degradation. Therefore, objective data for numerical evaluations is coming from bridge load tests. In this regard, the evaluation of a partial safety coefficient of variable traffic loads according to two different approaches based on bridge load tests and safety factors suggested by structural codes is presented. [ABSTRACT FROM AUTHOR]

Structural health monitoring (SHM) based on global navigation satellite systems (GNSS) is an interesting solution to provide absolute positions at different locations of a structure in a global reference frame. In particular, low-cost GNSS stations for large-scale bridge monitoring have gained increasing attention these last years because recent experiments showed the ability to achieve a subcentimeter accuracy for continuous monitoring with adequate combinations of antennas and receivers. Technical solutions now allow displacement monitoring of long bridges with a cost-effective deployment of GNSS sensing networks. In particular, the redundancy of observations within the GNSS network with various levels of correlations between the GNSS time series makes such monitoring solution a good candidate for anomaly detection based on machine learning models, using several predictive models for each sensor (based on environmental conditions, or other sensors as input data). This strategy is investigated in this paper based on GNSS time series, and an anomaly indicator is proposed to detect and locate anomalous structural behavior. The proposed concepts are applied to a cable-stayed bridge for illustration, and the comparison between multiple tools highlights recurrent neural networks (RNN) as an effective regression tool. Coupling this tool with the proposed anomaly detection strategy enables one to identify and localize both real and simulated anomalies in the considered data set. [ABSTRACT FROM AUTHOR]

Pinching characterizes the hysteretic response of several structural systems. It is associated with a reduced dissipated hysteretic energy under cyclic loading and can significantly affect seismic performance, especially under repeated earthquakes. Although several scholars proposed advanced joint arrangements with reduced pinching, ordinary timber structures present pronounced pinching effects due to the local damage to the timber joints. This paper quantifies the impact of variable pinching on the seismic performance of a timber structural archetype. The authors modeled the hysteretic response of a light-timber framed assembly using an empirical hysteresis model and assessed the sensitivity of the displacement demand of the chosen archetype to pinching, number of earthquake repetitions, and spectral acceleration. The choice of an elementary structural archetype, rather than a more complex system, allows isolating the effects of pinching, which could otherwise be disguised by other phenomena, like force redistribution between structural assemblies due to plasticization. [ABSTRACT FROM AUTHOR]

Rock-concert events in stadiums have raised complaints among dwellers of neighborhood buildings about annoying vibrations in Buenos Aires, Argentina, Wellington, New Zealand, Medellín, Colombia, and other cities around the world. Controversy about the causes and effects of vibrations has produced demands, alarms among inhabitants, and cancellations of spectacles with large economic consequences. Although the analysis and effects of vibrations on the stadium grandstands are well known, no comprehensive published paper could be found that addressed the effects of vibrations on neighborhood buildings when thousands of spectators jump on a stadium field. This paper covers this gap in civil engineering knowledge, introducing a systematic study (analytical and experimental) to explain the causes, predict building responses, and determine the size of the expected human, structural, and cosmetic effects on neighborhood buildings. First, the equations for modeling are presented: (1) the coordinated jump of the public on the field and the load generated, (2) the acceleration-wave propagation over the surface of an elastic solid, and (3) the responses of buildings at different distances from the stadium. The resulting equations are used to estimate the accelerations at building tops at distances within a radius of 3 km of the stadium. Second, the measurements planned and obtained during concerts are shown and evaluated. The results indicate that for buildings in resonance with the spectators' jumps (natural frequency of 2.1 Hz for 10- to 12-story buildings in Buenos Aires), the acceleration level in the upper stories is severe to people at distances of more than 3 km from the stadium, but it is not high enough to cause structural or nonstructural damage. [ABSTRACT FROM AUTHOR]

The article discusses a study which described a nonlinear finite-element model (FEM) that was used to simulate the steel-to-concrete bond mechanism in reinforced concrete (RC) tie members. It is suggested that the authors of the study have used two different sources to estimate material properties. It is also noted that the bond stress to concrete tensile strength ratio does not add information when the peak bond shear stress expected.

This paper presents the details of a numerical study aimed at investigating the fire performance of carbon-fiber-reinforced polymer (CFRP)-strengthened short square hollow section (SHS) steel columns with and without an insulation system. Steady- and transient-state finite-element (FE) models were developed to simulate the behavior of CFRP-strengthened columns exposed to uniform elevated temperatures and CFRP-strengthened and insulated columns exposed to standard fire conditions, respectively. They were validated using the results of the authors' experimental study. A detailed parametric study was then conducted using the validated steady-state FE model to determine the influence of SHS steel grade and dimensions and CFRP strengthening configuration on the axial compression capacity deterioration at elevated temperatures, based on which suitable design equations were proposed to predict the elevated-temperature axial compression capacity of CFRP-strengthened columns. Fire resistance ratings (FRRs) of CFRP-strengthened and insulated SHS columns were determined based on the time-temperature profiles from heat-transfer analyses and the load ratio versus critical temperature profiles developed from steady-state FE analyses. In this study, two types of insulation materials (spray-applied CAFCO 300 and intumescent paint) were investigated, and both were found to provide satisfactory FRRs, where more than 60- and 120-min FRRs were achieved for most columns with CAFCO 300 and intumescent paint, respectively. The modeling and design methods presented in this paper can be used to conduct fire safety designs of CFRP-strengthened and insulated steel columns. [ABSTRACT FROM AUTHOR]

This data paper reviews the experimental research on fully restrained beam-to-column connections for steel moment-resisting frames (MRFs) over the last 50 years worldwide and presents an experimental database consisting of 100 tests with an emphasis on those exhibiting inelastic panel zone behavior. The collected data, which is organized in a consistent format, includes full digitized histories of the local panel zone shear force–shear distortion as well as the global force–displacement hysteretic diagrams of each experiment. In most cases the original data was only available in paper format. The gathered dataset suggests that the existing panel zone models that are currently used for the seismic design of steel MRFs deviate, in some cases considerably, from the measured response quantities of an actual panel zone. These involve the panel zone stiffness and shear resistance at selected inelastic shear distortions of interest to the engineering profession. The assembled inelastic panel zone database provides ranges in which post-Northridge beam-to-column connections, which exhibit considerable inelastic deformations within the panel zone web, may achieve lateral drift demands larger than 4% without experiencing premature fracture. The assembled dataset constitutes an important source for validation of continuum finite-element models that could aid the simulation-based engineering design of steel MRF beam-to-column connections designed with a balanced design approach. The database is made available to the engineering and research communities through a publicly available data repository. [ABSTRACT FROM AUTHOR]

This paper attempts to formulate an expression for the estimation of equivalent viscous damping (EVD) for cross-laminated timber (CLT) structural archetypes as a function of ductility. The paper aims at contributing toward the direct displacement-based design procedure (DDBD) of CLT structures, which makes use of equivalent viscous damping and secant stiffness estimations as proxies for the estimation of the nonlinear behavior of structures. The available hysteretic models of CLT structures are very elaborate, and the inelastic time-domain simulations using hysteretic models are not easily manageable. Hence, the adoption of equivalent viscous damping is a crucial feature of any DDBD method. In this paper, the authors estimate the EVD of a set of 16 typologies of CLT buildings with an increasing slenderness ratio. The minimum of the squared error between the maximum drift of the elastic time-history and the hysteretic response gives the EVD. The extended energy-dependent generalized Bouc Wen (EEGBW) model, calibrated on experimental data, is used to predict the inelastic seismic response of the single CLT shear wall. The correlation between EVD and ductility is compared to existing EVD formulations referring to concrete and steel structures. [ABSTRACT FROM AUTHOR]

Temporary shoring structures are used in the construction of reinforced concrete buildings to transmit the loads of newly poured slabs onto the lower floors. The main problems involved in the use of shores/props are: (1) the possibility of having higher loads than those initially foreseen, and (2) the structural efficiency and cost of the system, which is normally oversized due to being designed to bear the maximum load of the most demanding building operation. This paper describes a test carried out on a full-scale one-story building to analyze the behavior of load limiters (LLs) installed on shores under actual construction loading conditions. The theoretical approach and development of this new LL concept were described in previous papers. Because these LLs still had not been tested in actual buildings, this paper covers the existing need for a test in the form of a "proof of concept." It also includes computer simulations and recommendations for the use of LLs. [ABSTRACT FROM AUTHOR]

This paper investigates the impact of Super Typhoon Mangkhut on Hong Kong, especially the wind effects on high-rise buildings, based on 24-h-long field measurement records collected from the two tallest skyscrapers (484 and 420 m in height) in the metropolis and six meteorological stations on different types of terrain on September 16, 2018. Mangkhut corresponded to a 50-year return period and was the most violent typhoon since wind records in Hong Kong began in 1946. In this large-scale monitoring study, the wind characteristics of Mangkhut over different terrains are investigated using the climate records by anemometers and a weather surveillance radar, the wind-excited structural responses of the monitored skyscrapers are analyzed according to measurements by accelerometers and a global navigation satellite system, the structural dynamic properties are estimated by the random decrement technique and the Bayesian spectral density approach, and both rigid and aeroelastic modeling techniques for wind tunnel testing are validated by in-situ measurements during the typhoon. This study aims to enhance the understanding of strong typhoon-generated wind characteristics over different terrains and provide comprehensive information for the wind-resistant design of high-rise buildings in tropical cyclone-prone regions. [ABSTRACT FROM AUTHOR]