Journal of Structural Engineering

In a coupled steel plate shear wall, the interaction between two steel plate shear wall piers enabled by the coupling beams improves the overturning capacity of the lateral force–resisting system. Furthermore, the boundary frames and coupling beams contribute significantly to the lateral strength of the system. This study presents an equation to quantify the relationship between the overstrength of the coupled steel plate shear wall and the percentage of the lateral seismic design force resisted by the web plates alone. This equation can be used in design to proportion the strength of web plates, the boundary frames, and the coupling beams. Two coupled steel plate shear wall archetype sets with different ranges of the degree of coupling (i.e., less than 0.4 and between 0.4 and 0.6) were designed considering the contribution to lateral strength from all components and their collapse performance was evaluated. Pushover and incremental dynamic analyses were conducted. The material models for the web plates, boundary frames, and coupling beams included deterioration. The analyses indicated that the complete strength of the system (i.e., the strength of the web plates, boundary frame and coupling beams) may be considered when the degree of coupling is above 0.4. When it is lower, a minimum overstrength is necessary to ensure that the seismic performance factors provide acceptable collapse performance.

Real-time hybrid simulation (RTHS) provides a cyber-physical testing method for system evaluation of global or local system evaluation of civil subjects to dynamic loading. Physical testing of experimental substructures is integrated with numerical simulation of analytical substructures, thus facilitating large-scale testing in size-limited laboratories. Current practice of RTHS often focuses on structural response evaluation under selected ground motions. This study presents an innovative application of RTHS for parameter calibration of rate-dependent devices for optimal structural response prediction. An adaptive experimental design approach is integrated with RTHS to account for realistic seismic demands on the rate-dependent device due to structural uncertainties. A kriging metamodel is utilized to surrogate the response discrepancy between RTHS and computer simulation with experimental substructure numerically modeled. Efficient global optimization (EGO) is then applied to sequentially determine new sample points for parameter calibration through laboratory testing to minimize the difference between RTHS and model-predicted results. The proposed approach is then applied for model parameter calibration of a self-centering viscous damper (SC-VD) device through RTHS. The parameters of the SC-VD device are calibrated from sequentially designed RTHS to optimize the error in maximum structural response prediction. The proposed adaptive approach is further compared with traditional experimental design methods and demonstrates better performance in maximum response prediction especially when resources are only available for a limited number of experiments.

Unreinforced masonry buildings are prone to catastrophic damage when subjected to debris-flow impact. Engineered cementitious composite (ECC) layers were utilized to strengthen unreinforced masonry walls belonging to a 1/2 scaled timber-masonry building to mitigate the risk of collapse, and rolling steel balls of various masses were used to impact the strengthened walls to investigate the effects of the ECC layer strengthening. The typical characteristics of ECC, i.e., multiple cracking and high damage tolerance, were clearly exhibited during impacting, which helped to transfer the failure mode of the masonry walls from brittle to a much more ductile one. This article introduces strain response, displacement response, acceleration response, and dynamic property of the strengthened walls under impact. The test results demonstrated that ECC layer strengthening can significantly enhance impact resistance, including stiffness, energy dissipation, etc. For simplified assessment, the residual displacement ratio is recommended as the indicator to characterize the damage level of masonry walls strengthened with the ECC layers.

The present study combines the advantages of both stainless steel and lightweight high-ductility cement composite (LHDCC) to develop a durable stainless steel–LHDCC composite for marine protective structures. Firstly, the study conducts an impact test program by the drop-hammer test machine to investigate the flexural impact performance of the composite beam. Three failure modes are captured: (1) flexural failure with bond-slip of steel–concrete interface, (2) flexural failure without bond-slip of steel–concrete interface, and (3) shear failure. The dynamic responses including the impact force, reaction force, inertia force, and displacement responses are analyzed in detail. The effects of stud spacing, concrete core thickness, stud type, and concrete layer number on the impact response and failure mode are investigated. Then, the study adopts LS-DYNA to simulate the dynamic behavior of the composite beam under different impact load scenarios. The numerical results are in good agreement with the test results. The bending moment and shear distribution of the composite beam and the influences of impact momentum and impact energy on the dynamic responses are analyzed based on the FEM results. Finally, the study proposes a trilinear load-displacement relationship considering the effects of strain rate and degree of composite action, which is incorporated into the modified single-degree-of-freedom (SDOF) model to predict the impact responses. The results show that the predictive results can well reproduce the displacement-time response and peak displacement of the composite beam.

In Japanese engineering practice, pile foundations are designed to lower base shear demands below that considered in the superstructure’s design. In recent earthquakes, such buildings incurred significant pile damage even in cases where the superstructure only had minor damage. This study looks to replicate this failure mechanism via large-scale shake-table tests of a pile-supported building designed following Japanese practice, compare its performance against a fixed-base case, and identify issues with such buildings. The specimen was a 40%-scaled 3-story reinforced concrete frame building supported on weak piles buried in soil. After completing shake-table testing of the pile-supported specimen, the specimen’s foundation was fixed directly to the soil tank to mimic a fixed-base condition, and further excitations were applied. For the pile-supported case, the piles underwent drift ratio demands of up to 14% and suffered local collapse failure at 1.0–1.5 times the design shaking intensity, whereas the superstructure only had a drift ratio of 0.17% and minor damage. These observations were consistent with postearthquake damage assessments, demonstrating that the shake-table tests were able to replicate realistic failure mechanisms. For the fixed-base case, the superstructure was able to withstand demands equivalent to 1.7–2.5 times the Japanese design spectra before reaching 2.0% drift and did not exhibit any strength degradation. Based on these results, buildings with weak piles will likely suffer significant failure at smaller intensity events than that which the superstructure would have been able to withstand. Furthermore, the lack of superstructure damage for such cases may lead to significant pile failure being unidentified during postearthquake inspections, resulting in unsafe buildings being occupied.

Closed-form model expression is commonly required for parametric data assimilation (e.g., model updating, damage quantification, and so on). However, epistemic bias due to fixing the model class is a challenging issue for structural identification. Furthermore, it is sometimes hard to derive explicit expressions for structural mechanisms such as damping and nonlinear restoring forces. Although existing model class selection methods are beneficial to reduce the model uncertainty, the primary issue lies in their limitation to a small number of predefined model choices. We propose a symbolic deep learning framework that alleviates the constraint of fixed model classes and lets the data more flexibly determine the model type and discover the symbolic invariance of the structural system. A design principle for symbolic neural networks has been developed to leverage domain knowledge and translate data to flexibly symbolic equations of motion with a good predictive capacity for new data. A two-stage model selection strategy is proposed to conduct adaptive pruning on network and equation levels by balancing the model sparsity and the goodness of fit. The proposed method’s expressive strengths and weaknesses have been analyzed in several numerical case studies, including systems with nonlinear damping, restoring force, and chaotic behavior. Results from an experimental case study revealed the potential of the proposed method for flexibly interpreting hidden mechanisms for real-world applications. Finally, we discuss necessary improvements to transfer this computational method for practical applications.

Since their first use in 1989, buckling-restrained braces (BRBs) have proven to be an efficient energy dissipation device. Two reduced scale quasi-static cyclic experiments were conducted for a reinforced concrete (RC) moment frame with substandard seismic details retrofitted with a BRB to examine its performance. In the first experiment, the BRB was attached to the RC frame utilizing post-installed U steel plates designed using the uniform force method. The RC frame was tested utilizing the BRB retrofit until the BRB steel core fractured in tension, at which point the BRB was removed. A second experiment was carried out on the damaged RC frame, following removal of the BRB, with the U steel plates still attached. The two experiments showed that the RC frame retrofit using a BRB and U steel plates is an effective approach to doubling the strength, stiffness, and total hysteretic energy dissipation of the original RC frame with substandard seismic details. In addition, a method of proportioning the seismic retrofit components, including the size of the BRB and U steel plates, is developed. Nonlinear pushover and cyclic analyses were used to compare the experimental results to OpenSees numerical models.

In North American steel design specifications, a directional strength-enhancement factor is used to increase the predicted strength of fillet welds subjected to transverse loading (i.e., loading at 90° to the weld axis). Committees have expressed concerns about this factor being unsafe for single-sided fillet welds; however, due to a lack of testing, only cautionary statements have been made in most specifications to address this. An experimental program was hence developed to test 40 transversely loaded single-sided fillet welds in cruciform connections subjected to branch axial tension. The connections varied weld size, branch-plate thickness, and loading eccentricity to investigate the effects of these parameters on fillet-weld strength. Results of this program are presented herein, and a first-order reliability method (FORM) analysis was performed. It is shown that current fillet-weld design provisions meet/exceed code-specified target safety indices (i.e., $\beta =4.0$) provided that (1) the directional strength-enhancement factor is not used, and (2) stresses that result in opening of the weld root notch are avoided.

Over recent years, the application of performance-based design (PBD) has continually grown in the design of tall buildings and other structures excited by large wind loads. PBD has also become a mainstream approach to assess and reduce the risks in the rehabilitation of existing structures. The significant wind-related economic losses incurred every year around the world have prompted researchers to develop methods to reframe wind engineering to embrace the concepts of PBD. The main objective of performance-based wind engineering (PBWE) is to assess the adequacy of a structure in terms of the decision variables (DVs) set forth by the stakeholders. Each DV is defined to satisfy specific performance levels such as operational, immediate occupancy, life safety, and collapse prevention. The performance levels are defined based on acceptable levels of strength and serviceability requirements of both structural and nonstructural components. They also reflect the probable levels of damage, casualties, downtime, and costs of repair. In this paper, a 44-story steel frame building under the action of wind loads was analyzed and evaluated using PBD. To understand the structural response under long-duration wind loads, the building was subjected to randomly varying wind loads for a duration of 30 min. Different time history analyses were conducted with wind speeds varying between 45 and $80\mathrm{m}/\mathrm{s}$ (100 and 180 mph). The basic design wind speed of the building for the preliminary design based on static analysis was $58\mathrm{m}/\mathrm{s}$ (130 mph). The building responses recorded include acceleration and displacement time histories at every floor level. These responses were used to evaluate the peak and root mean squared (RMS) variations of acceleration and interstory drift along the height of the building and also to make comparisons between different wind speeds. The member forces were recorded to identify the locations of plastic hinges and also to interpret any unusual variations in the recorded accelerations and displacements in the building. The fragility and loss ratio curves are presented, showing the response parameters in comparison with the limiting threshold specified by FEMA to categorize the structural components into different damage states (DSs) and corresponding costs of repair or replacement.

This paper introduces CLEMSON, an automated machine-learning (AutoML) virtual assistant (VA) that enables engineers to carry acCeLErated, siMulation-free, tranSparent, reduced-Order, and infereNce-based fire resistance analysis with ease. This VA learns from physical observations taken from real fire tests to bypass bottlenecks and ab initio calculations associated with traditional structural fire engineering methods. CLEMSON leverages a competitive ML algorithm search to identify those most suited for a given problem and then blend them into a cohesive ensemble to realize faster and reduced-order assimilation of predictions, thereby attaining higher accuracy and reliability. In addition, this VA is designed to be transparent and hence is supplemented with explainability measures to allow users to identify key factors driving its rationale and predictions. Once fully realized, CLEMSON augments its inner workings into a graphical user interface that can be used in a coding-free manner and with enriched visualization tools to allow users to directly harness the power of ML without the need for special software. To showcase the merit of the proposed VA, CLEMSON is applied to assess classification and regression problems by means of evaluating fire resistance rating, as well as temperature rise history and deformation history of concrete-filled steel tubular (CFST) columns via five algorithms, namely: extreme gradient boosted trees, light gradient boosted trees, neural networks, random forest, and TensorFlow. Finally, this work also introduces three new and functional performance metrics that are explicitly derived for structural fire engineering applications and hence can be used to cross-check the validity of ML models.

The mechanical properties of constructional steels at different strain rates were the basis for the dynamic analysis of the progressive collapse of steel structures. The effect of strain rate on the hardening behavior and ductile fracture for the high-strength steel Q690 is investigated in this paper. Quasistatic and intermediate strain-rate experiments were performed. A smooth sheet and a V-shaped notched specimen were carefully designed to cover intermediate and high-stress triaxialities. The experimental results revealed that the effect of strain rate on the hardening behavior is sensitive to stress state. A novel dynamic isotropic hardening law was developed, taking advantage of the Cowper–Symonds and Johnson–Cook hardening models. Also, negative and positive strain-rate effects on the ductility of Q690 were observed in the smooth and notched specimens, respectively. An attempt was made to introduce a new strain-rate term into an uncoupled ductile fracture model to describe the differences of the strain-rate effects at various stress states. The new hardening law and the strain-rate-dependent ductile fracture model were validated with satisfactory accuracy.

In this paper, three one-third scale reinforced concrete (RC) beam-column-slab structure specimen tests were conducted to investigate the collapse mechanisms under a loss of the corner column, including a frame with slab (S-COR), a frame with slab and secondary beams (SS-COR), and a frame without slab (NS-COR). The slab and secondary beam’s contributions were investigated by comparing the SS-COR and NS-COR, SS-COR, and S-COR specimens. The results show that the RC slab significantly enhanced the load resistance. Only a slight increase in peak resistance capacity of the SS-COR specimen was observed, while the ductility improved obviously due to the existence of secondary beams. The failure mode of the SS-COR frame is different from that of the S-COR frame: No concrete failure line occurs on the slab bottom, and the cracks develop entirely on the slab top. Moreover, based on the test results, finite element models (FE) were updated by adapting the OpenSeespy, which shows a good fit between the test curves and simulation results. Finally, 1,000 samples considering the uncertainty parameters were generated using Monte Carlo sampling to better understand the effect of uncertainty on the structure response. Data-driven models based on machine learning were used to predict the peak resistance capacity of the RC structures with slab and secondary beams.

This paper proposes a hybrid technique to solve the inverse problem of damage localization and severity estimation in beam structures. The first phase of the method involves the use of influence lines (ILs) to extract information about the damage location. Then, a genetic algorithm (GA), representing the core of the whole procedure, uses static parameters as displacements and rotations at a few points to evaluate the bending stiffness along the structure by updating a finite-element model. The information obtained in the first phase is used in the second phase for (1) reducing the number of design variables of the GA and the consequent computational time; and (2) improving the accuracy of GA solutions because it allows a suitably trained neural network to select proper values for the coefficients of the proposed cost function in the genetic algorithm. The procedure is applied to a test problem, a simply supported, prestressed concrete railway bridge located in northern Italy. Numerical experiments are also conducted to test the procedure when the beam length and geometric properties vary.

The long-term performance of posttensioned timber joints is closely related to the time-dependent prestressing force. Figuring out the variation of prestressing forces is vital for the long-term safety of posttensioned timber joints. In this study, posttensioned timber joints with different structural details were monitored over 750 days to investigate the prestressing force loss under varying environment. The time-dependent variations of temperature and relative humidity, moisture content, timber strain, and prestressing force were captured. The effects of key factors including prestressing ratios, timber deformation, environmental conditions, and reinforcements on the time-dependent prestressing force were carefully analyzed. Subsequently, a numerical model was established to simulate the prestressing force variation of posttensioned timber joints. Good agreements between experimental and simulated results validated the proposed numerical model. Lastly, the potential loss of prestressing force in posttensioned timber joints during a service life of 50 years was predicted by the validated numerical model. This study demonstrates that the prestressing ratios and environmental conditions have significant influence on the time-dependent prestressing force. As expected, the effect of deformation perpendicular to the grain on loss of prestressing force is much bigger than that of deformation parallel to the grain. Moreover, the steel reinforcement can effectively eliminate the loss of prestressing force.

The use of unstressed Grade 1860 MPa seven-wire steel strands as longitudinal reinforcement has the potential to reduce steel congestion in reinforced concrete members. However, no studies which use unstressed steel strands as the longitudinal reinforcement in concrete columns have been reported in the literature. Thus, in this study, five large-scale column specimens: four of which used unstressed steel strands and one which used conventional Grade 420 MPa deformed bars as longitudinal reinforcement were subjected to cyclic loading under constant axial load to investigate the effectiveness in using strands. Columns with unstressed steel strands as longitudinal reinforcement exhibited drift capacities ranging between 4.96% and 5.70%, which is well over the conventional expectation of 3.50% drift requirement for columns in special moment frames. Also, the specimens exhibited lower energy dissipation but enhanced recentering capability owing to the fact that the strands have significantly higher tensile yield capacity compared to deformed bars. A reduction in effective elastic stiffness was also observed as the postcracking stiffness of specimens with strands dropped due to the low longitudinal reinforcement ratio of 0.78% provided. The test results indicated the relative ineffectiveness of strands in compression than in tension, where the strand bulged and unwound once the surrounding confinement deteriorated. Despite this, strands did straighten up and continued to sustain tensile stresses under load reversal. Based on the experimental observations, two constitutive models, one which considers strain hardening and the other which assumes an elasto-perfectly plastic response in tension was proposed for strands. The constitutive model with strain hardening was able to produce reasonably accurate estimates of flexural strength when used in a detailed moment-curvature analysis. Both constitutive models when used in a simplified analysis, which used equivalent stress block for concrete, was able to consistently produce conservative estimates of flexural strength, which is suitable for design purpose.

The ability to conduct accurate regional seismic risk assessments is key to informing a risk-reduction policy and fostering community resilience. This paper presents a machine learning-based framework to predict a building’s postearthquake damage state using structural properties and ground motion intensity measures as model inputs. The machine learning techniques assessed, namely, logistic regression, k-nearest neighbors, decision tree, random forest, AdaBoost, and gradient boosting, are trained using a dataset of nonlinear response history analysis results from 36 detailed structural models of modern reinforced concrete shear wall buildings ranging from four to 24 stories and subjected to approximately 500 ground motion records with a range of shaking intensities. The results indicate that the gradient boosting classifier is the most efficient algorithm by achieving a prediction success (F1-score) of 87%. The proposed framework also leverages synthetic data samples to support the prediction of severe damage state instances, that is, collapse. The percentage of observed collapse cases correctly classified by the gradient boosting algorithm is increased from 76% to 93% when synthetic data are also used for training. The framework is implemented in a portfolio of reinforced concrete shear wall buildings across the Metro Seattle region to quantify earthquake-induced damage and collapse risk. The framework shows great potential for enhancing regional seismic risk assessments by leveraging datasets of detailed nonlinear response history analysis results.

The high cost of manufacturing high-performance fiber-reinforced cementitious composites (HPFRCCs) and low confidence in predicting their mechanical properties have limited their widespread use as construction materials. Also, the lack of reliable numerical stress-strain cyclic behavior models prevents the analysis and study of potential industrial applications. In this research, a new uniaxial fiber-reinforced cementitious composite constitutive model (FRCC model in OpenSees) is developed and validated for use in monotonic and cyclic analyses consisting of fiber section finite elements. The model is validated at the material and structural level through correlations of the numerical results with the limited laboratory test data available in the literature, as well as some new experimental results. The quantification of the uncertainties in structural response parameters due to model input parameter uncertainties is conducted via sensitivity analysis. The validation results make the model useful for performance-based assessment and design of civil engineering structures that use HPFRCCs.

This paper reports the shear performances of steel wedge block–crossed inclined stud–ultrahigh performance concrete (UHPC) connections for application to steel-concrete composite bridges. The study entailed 36 pushout tests based on the studs with 1.0, 1.5, and 2.0 aspect ratios, inclined 0°, 30°, 45°, and 60° from vertical. The test results show that in studs with aspect ratio less than 1.5 (ultrashort studs) and inclined at either 30° or 45°, shear strength increases 12% with initial slip increase of 47% and 110%, respectively, relative to the 0° connection. Also, the specimen comprising studs at 45° inclination showed a 1%–91% increase in secant shear stiffness at the elasto-plastic stage, implying less nonlinear sectional flexural stiffness response for such inclined connections. As the stud aspect ratio increased from 1.0 to 1.5, the shear strength increased by 13%, 25%, and 18% for studs inclined 30°, 45°, and 60°, respectively. Increased stud aspect ratio from 1.5 to 2.0 had only a minor influence on shear strength. During the test, the local embedment (UHPC over the stud head top) and UHPC slab shear failure with many subtle cracks showed pronounced ductility (continuous clear snapping sounds from steel fibers and major cracks observed approaching failure) for a stud aspect ratio less than 1.5. Furthermore, the reduced rigidity method, used in a given section under the service load, showed 10% lower deflection than 0° stud connections and a within-5% increase of the rigid connections for ultrashort studs. These results show that this type of shear connector exhibits good stiffness and strength performance, especially for ultrashort studs. In future research, low cyclic loading and high cycle fatigue tests should be performed on these connections.

Coupling beams in shear wall and frame–shear wall systems are structural fuses that undergo significant inelastic deformation and absorb earthquake input energy. However, severe damage to coupling beams can disrupt building functions and have substantial repair costs. This study proposes frictional steel truss coupling beams (FTCBs) that aim to resolve these issues. The truss configuration is advantageous because it decouples shear and bending demands and facilitates pipeline layout. Shear-critical FTCBs (SFTCBs) adopt a smaller span-to-height ratio and place friction dampers in the diagonal webs, while bending-critical FTCBs (BFTCBs) adopt a larger span-to-height ratio and place friction dampers in the bottom chords. Quasi-static tests were conducted to validate the seismic performance of the FTCBs. A traditional reinforced-concrete coupling beam (RCCB) specimen was also tested for comparison. Results showed that FTCBs can realize damage control by concentrating inelastic deformation in friction dampers while keeping the main body of the steel truss and wall piers elastic. The FTCBs exhibited full and stable hysteretic behavior and enhanced energy dissipation capacity and replicability, which is difficult to achieve in RCCBs. Therefore, the FTCBs provide resilient alternatives to coupling beams over a range of span-to-height ratios.

Accurate numerical modeling of structural components is necessary for both performance-based designs of new structures and performance assessments of existing structures. Steel special concentrically braced frames (SCBFs) represent a large portfolio of steel buildings in areas of high seismicity, especially in North America. Therefore, it is necessary to critically study the accuracy of available numerical models for SCBFs and propose improvements to them, if necessary. This requires forming a database of high-fidelity benchmark experimental results for SCBFs against which models can be compared. This paper presents multielement hybrid simulations on a steel SCBF, as a representation of systems with highly unsymmetrical hysteretic response. A representative buckling brace specimen is developed and verified through reversed-cyclic tests to physically capture the response of SCBFs in the experiments. 2-element and 4-element pseudo-dynamic hybrid simulations are carried out on the reference SCBF using the University of Toronto Ten-Element Hybrid Simulation Platform (UT10). The experimental results from the multielement tests are compared with numerical simulations in detail using the available numerical models, which are observed to predict the response well.

In this paper, the shaking table tests and finite element analyses were conducted on the traditional thermal power plant main building and the thermal power plant main building with BRBs, respectively. The differences in torsional resistance between the two structural systems were studied, and the suppression effect on the displacement field distortion of the plane consisting of crane and tracks through adding BRBs in the thermal power plant main building was discussed. The study shows that after adopting a buckling-restrained brace in a thermal power plant main building, the damage and torsional response of the structure under an earthquake can be reduced, the occurrence of inelastic torsion can be effectively blocked, and the translation-torsion coupling effect can be reduced. At the same time, it can reduce the distortion amplitude of the displacement field of the plane consisting of crane and tracks and play a key role in improving the reliability of roof truss, crane, coal bucket, and low-ductility connectors, and it also facilitates the realization of performance-based seismic design.

As inelastic design for wind is embraced by the engineering community, there is an increasing demand for computational tools that enable the investigation of the nonlinear behavior of wind-excited structures and subsequent development of performance criteria. To address this need, a probabilistic collapse assessment framework for steel structures is proposed in this paper. The framework is based on the integration of a high-fidelity fiber-based nonlinear structural modeling environment with a wind-tunnel-informed stochastic wind load model to perform nonlinear time history analysis. General uncertainty is propagated using a stratified sampling scheme enabling the efficient estimation of reliabilities associated with rare events. The adopted models for simulating high-fidelity nonlinear structural behavior were found, in general, to be adequate for capturing phenomena, including progressive yielding, buckling, and low-cycle fatigue, that are essential for wind induced collapse analysis. In particular, the adopted fatigue model was found to be capable of predicting damage and potential fiber/section fracture associated with non–fully reversing stress-strain cycles that are characteristic of wind loading. Through illustration on a 45-story archetype steel building, critical discussions on the types of observed collapse mechanisms, the difference between along-wind and across-wind nonlinear behavior, reliabilities associated with first yield, and collapse are presented. A probabilistic description of the residual and peak story drifts is also provided through development of fragility functions.

This paper proposes a novel, cold-formed portal framing system that comprises tapered box members formed from two cold-formed nested channel sections. The proposed method possesses structural and nonstructural advantages, such as improved seismic performance, enhanced building hygiene through bird and dust resistance, further corrosion resistance, and aesthetic improvement, as a result of fly bracing removal. The novelty of the box member lies in the tapering ability of the section, leading to material and paint savings. To examine the failure mechanisms and structural performance of the tapered box portal frame and to investigate the adequacy of the design method, two full-scale portal frames with an 18.16-m span were built and tested to failure under two common loading scenarios. The first was lateral cyclic loading into the inelastic range in conjunction with a vertically acting permanent load. The possibility of ductile plastic hinge formation in a severe earthquake was investigated using lateral cyclic testing. The second was vertical loading to failure. A novel economic loading setup was used to apply the gravity load on the frame. For the seismic design of this section type, slenderness limits are proposed for seismic applications along with the design ductility. A rotational stiffness value for a nominally pinned portal frame column base was also suggested in this study.

This paper aims to investigate the seismic behavior of buildings equipped with self-centering birocking walls to find out the optimum location of the rocking section in the height. For this purpose, several two-dimensional nonlinear time-history analyses were carried out on different birocking structures of 4, 8, 12, 16, and 20 stories subjected to three sets of ground motions. The ground motions comprised 22 far-field (FF), 14 near-field pulse (NF-pulse), and 14 near-field nonpulse (NF-nonpulse) ground motions. The simulations have been performed utilizing the open source finite-element framework OpenSees. In this study, the first rocking section of a birocking wall was at the base and the second was considered at three different locations: one-quarter (R2-J1), half (R2-J2), and three-quarters (R2-J3) of the wall height. The seismic vulnerability of the models were statistically assessed. To determine the optimum design, a utility coefficient was defined as the average of shear and moment reduction coefficients. The results showed that R2-J2 walls are effective under FF and NF-nonpulse records, while R2-J1 walls show their best performance under NF-pulse records.

In order to reduce the use of adhesives, the development of adhesive-free engineered wood products is one of the research focuses in timber structures. This paper studies the mechanical properties of cross-laminated timber beams connected by densified wood (DW) dowels. Four-point bending tests were performed to study the influence of the arrangement and number of DW dowels on the bending strength and effective bending stiffness of the dowelled cross-laminated timber (DCLT) beams with three layers. The modified planar shear test was adopted to determine the effective shear properties of the DCLT. Cross-laminated timber (CLT) beams were also tested as references. Although the bending and shear properties of the DCLT were lower than those of the CLT, the DCLT showed a significantly larger ductility. The gamma method is promising for determining the effective bending stiffness of the DCLT using the effective shear modulus obtained from the shear test.

Mass timber panel–concrete composite (MTPCC) floors combine timber and concrete through high-performance connections to create an efficient floor system with high stiffness, high strength, and low self-weight. Previous research on MTPCC floors focused on improving the composite efficiency of floors under static loadings by testing different types of shear connectors. The dynamic performances of MTPCC floors, which can govern the floor span and thickness, have not been well investigated. In this study, vibration tests were conducted on glued-laminated timber panels and notch-connected MTPCC floors with different spans, thicknesses, and connection layouts. The dynamic properties, including natural frequencies, damping ratios, and mode shapes, were obtained for floors under different supporting conditions. Test results showed that MTPCC floors with a 6-m span had fundamental natural frequencies generally higher than 8 Hz. The addition of the concrete layer to the bare timber panels improved the floor fundamental natural frequency and damping. Deflection tests and walking tests were performed on MTPCC floors to evaluate the floor vibration serviceability performance, and it was found that the existing design criteria predicted inconsistent results. The flexural stiffness of MTPCC floors determined from vibration and deflection tests was close to full composite, while only partial composite action in the composite floors was achieved under a higher load level in destructive bending tests.

As footbridges are lightweight and slender structures, they are highly sensitive to human-induced excitation, and control measures are required to suppress undesirable structural vibrations. As wave propagation is improbable within a band gap, this study introduces a band gap in a footbridge and develops a new technique as an alternative to suppress the human-induced vibration response. Inerter-based dynamic vibration absorbers (IDVAs) are arranged periodically in the footbridge, which can convert the conventional box girder into a specially designed periodic metamaterial beam with a local resonance band gap. Following the spectral element method, the band gap structure of the metamaterial beam with IDVAs is proposed and validated by test results and numerical experiments. The band gap structure can be simultaneously tuned by the parameters of the IDVAs, including spring stiffness, inertance, and attached mass. A computer-based program was presented to determine the reasonable design parameters of IDVAs. Finally, a new vibration attenuation method for footbridges is proposed based on the theory of metamaterials and validated by numerical experiments. The results show that the proposed method exhibits good performance in vibration attenuation.

Real-time hybrid simulation (RTHS) provides an efficient and effective experimental technique for rate-dependent energy-dissipation devices in seismic hazard mitigation. The structure under investigation is generally divided into analytical and physical substructures to enable large-scale experiments for system behavior. Accurate modeling of analytical substructures is critical for truthful structural response replication through RTHS. This presents challenges to laboratory practice of RHTS such as capability of specialized finite-element software to replicate complex nonlinear behavior, and the equipment capacity to accommodate large-scale finite-element modeling to be executed in a real-time manner. This study explores the use of a polynomial chaos nonlinear autoregressive with exogenous input (PC-NARX) model to conduct RTHS in laboratories using existing equipment and general-purpose finite-element analysis (FEA) software readily available in earthquake engineering research. The NARX model can be trained using any existing FEA software for a good representation of structural dynamics. Polynomial chaos expansion (PCE) is then introduced to surrogate NARX model coefficients to account for ground motion uncertainties. Laboratory tests of a self-centering viscous damper were conducted as proof of concept to experimentally demonstrate the effectiveness of RTHS with PC-NARX metamodeling approach. The results were further compared with the kriging surrogate technique for NARX model coefficients to explore a better technique to account for uncertainties in RTHS.

Wire arc additive manufacturing (WAAM) is a metal three-dimensional (3D) printing method that enables large-scale structural elements with complex geometry to be built in a relatively efficient and cost-effective manner, offering revolutionary potential to the construction industry. However, fundamental experimental data on the structural performance of WAAM elements, especially at the member level, are lacking. Hence, an experimental study into the flexural buckling response of WAAM tubular columns has been conducted and is presented in this paper. A total of 18 stainless steel square and circular hollow section (SHS and CHS) columns were tested under axial compression with pin-ended boundary conditions. Regular SHS and CHS profiles were chosen to enable direct comparisons against equivalent, conventionally manufactured sections and, hence, to isolate the influence of the additive manufacturing process, whereas the cross-section sizes and column lengths were varied to achieve a broad spectrum of member slendernesses. Given the geometric undulations inherent to the WAAM process, 3D laser scanning was used to determine the as-built geometry and global geometric imperfections of the specimens; digital image correlation (DIC) was employed to monitor the surface deformations of the specimens during testing. Full details of the column testing program, together with a detailed discussion of the experimental results, are presented. The applicability of the current column design provisions in EN 1993-1-4 and AISC 370 to WAAM stainless steel members was assessed by comparing the test results with the codified strength predictions. The comparisons emphasized the need to allow for the weakening effect of the inherent geometric variability of WAAM elements to achieve safe-sided strength predictions.

To increase the energy dissipation capacity and deformation capacity of the beam-column connections, and save space for realizing more architectural functions in the frame structure, a new type of metallic damper is developed that is installed inside the connection area and is convenient to assemble and disassemble. The components and construction procedure of the damper are explained, and according to the analysis on the force transfer mechanism of the beam-column connections equipped with this damper, their deformation capacity and energy dissipation can be greatly improved. To verify the cyclic behavior of the new rotational metallic damper, an experimental study is conducted and the failure process and hysteretic behavior of the test specimens with different damping materials are reported. The load-deformation behavior, bending moment capacity, overstrength, and energy dissipation capacity are analyzed, and it is found that the specimens made of low-yield-point steel BLY160 and high-strength steel Q345GJ have both demonstrated a ductile failure pattern and stable and energy-dissipative hysteretic behavior. The rotational capacity of the damper can be as large as 0.08, and the specimen composed of BLY160 presents a significant strain-hardening phenomenon as its overstrength factor has exceeded 2.0. Both specimens have excellent energy dissipation capacity under large deformations, but the specimen made of BLY160 is more energy-dissipative under small deformations as its yielding strength is much low than Q345GJ. Meanwhile, formulas to calculate the bending moment capacity of the damper are deduced. Subsequently, a numerical investigation is carried out to establish an accurate finite-element model for simulating the cyclic behavior of the damper. Based on the proposed numerical model, the influence of shear or axial forces induced by the connection on the damper is evaluated, and an optimization procedure is conducted to further increase the seismic performance of the rotational damper. In the end, the typical frame substructures with a traditional beam-column connection, with typical metallic dampers, and with the proposed rotational damper are analyzed, and the results show that the rotational damper could more effectively improve the deformation capacity and energy dissipation efficiency of the substructure compared with other dampers. Then, nonlinear time-history analysis is performed on a case-studied structure with and without the rotational damper, and the results prove that the new rotational metallic damper can significantly improve the seismic performance of the structure.

This paper presents the results of a finite-element (FE) study on posttensioned (PT) rocking steel bridge piers, each composed of a circular tubular column, welded end plates, PT strands, and axially yielding steel energy dissipators (EDs), and corresponding chairs. The pier is configured so that it rocks at its base. Previously conducted experiments on five scaled rocking steel columns are summarized. Three-dimensional (3D) continuum FE models of the tested specimens are generated with the objective of verifying the capability of the modeling approach in the simulation of the local and global responses. Strain-controlled cyclic coupon tests were performed to quantify the kinematic and isotropic hardening material parameters. A simplified method is proposed to model the cyclic loss of prestressing because of wedge seating in a typical industry monostrand anchorage system. The FE procedure is then calibrated against the experimental data at the material, component, and global pier levels. A parametric study is conducted to examine the effects of key factors such as material model, P-Delta, base plate dimensions, column diameter-to-thickness and initial axial force ratios, ED chairs, and ED location on the lateral cyclic response. It is demonstrated that, for a given target drift, local buckling and the resulting residual lateral deformations of a rocking steel pier are a function of the diameter-to-thickness and initial axial force ratios of the column and the ED chairs. By the proper selection of these variables, a stable and robust self-centering response can be obtained with minimal damage to the bridge pier.

This paper presents the derivation and validation of a mechanics-based finite element for the analysis of shear-critical slender reinforced concrete beams and columns. The element can capture the load-deformation behavior associated with axial loads, bending moments, and shear in uncracked or cracked reinforced concrete using only a small number of degrees of freedom and easily measurable input parameters: the gross cross-section dimensions and steel and concrete material stress/strain curves. The element is specifically derived to represent the full reinforced concrete cross section (i.e., one element is required over the depth of a member) and consists of four nodes, with two translational degrees of freedom (DOFs) per node. This formulation facilitates modeling the interface regions between walls or joint regions, beams, or columns and lowers the numerical complexity and number of decisions that the user must make. The element shows improvements to results from design codes when validated against experimental results for 782 beams without shear reinforcement and 167 beams with shear reinforcement taken from the literature. By reducing the number of degrees of freedom, the element will allow relatively rapid two-dimensional (2D) nonlinear analyses of full reinforced concrete buildings.

Carpentry joints are the traditional connecting media for timber elements. Among those, step joints are particularly important at structural size, because they are the most frequent solution to connect rafters and tie beams in roof timber trusses. The forthcoming version of Eurocode 5 will include, for the first time, provisions on its design. This paper describes the experimental investigation carried out to assess the safety and accuracy of the design formulae proposed in the literature and in some national standards on timber structures design. Although the behavior of double step joints is particularly aimed, given the scarce experimental information available on this configuration, single step joints were also investigated, intended to serve as a reference basis for the double-step case. It is also of interest to investigate how the load is shared between the two notches in the double-step geometries. To this end, an analytic procedure is proposed, based on the strains measured in the notches’ regions during the tests. Various test specimen groups were defined, whose dimensions favored one particular failure mode. The test setup was designed in order to simulate a rafter-to-tie beam connection in a timber truss. Besides the main strength tests of the step joints, side bending tests to EN 408 were also carried out in order to a better mechanical characterization of the used solid timber. Regarding the capacities, the results are in good agreement with the values provided by the formulae, and always on the safe side. The prevailing failure mode was as expected in most configurations, indicating the adequacy of the proposed design expressions. A procedure was proposed to determine the load share between the two notches in double step joints, but some setup detail changes are recommendable in order to improve its stability and reliability.

To overcome the shortcomings of traditional shear walls, structure systems have been proposed and investigated. One such structure system is a steel-reinforced concrete shear wall, which has certain desirable properties such as good load-bearing capacity, stiffness, and seismic performance. This paper proposes an M-section cold-formed thin-walled steel reinforced concrete (MCTSR) shear wall, which uses M-section cold-formed thin-walled steel to function as reinforcements. Six specimens with different permanent formwork types, axial compression ratios, reinforcement diameters, and other parameters were tested under cyclic loading to investigate seismic performance. The results demonstrate that various types of permanent formwork, including cement fibrolite plate, metal lathing, and polystyrene board can meet the requirement of related seismic design codes, construction demand, and assembly requirements, and have no obvious impact on the ultimate load-bearing capacity, lateral stiffness, and stiffness degradation rate. However, it changes the energy dissipation capacity and ductility, which are two important indexes to evaluate seismic performance in engineering practice. The failure mechanism and the influence of axial compression ratio, reinforcement diameter, and space between reinforcements are discussed. The shear-strength equations proposed by various countries’ or regions’ codes were analyzed, which can be used as a reference for related engineers and designers. Finite-element models for MCTSR shear walls were established for further investigation.

This paper investigates the influence of rebars’ corrosion monitoring systems on the vulnerability assessment and life-cycle cost analysis (LCCA) of reinforced concrete (RC) bridge piers subjected to repeated earthquake loading. A methodology is proposed to investigate the life-cycle economic savings gained with the use of a structural health monitoring (SHM) system made of corrosion sensors, exploiting the construction of damage-dependent fragility curves and using the pacific earthquake engineering research (PEER) equation to calculate the seismic probability of failure. The availability of corrosion sensors’ data is accounted for in the degradation model for assessing the probability of failure by assuming that the recorded corrosion parameters are deterministic variables during the monitored period. Monitoring data are simulated by choosing values from the literature for the parameters representing the corrosion conditions. Seismic damage accumulation is considered through Monte Carlo (MC) simulations of long-term seismic scenarios considering the mean annual rate of earthquake occurrence obtained by the seismic hazard curves. The results of the methodology application to a case study highlight the importance of incorporating corrosion effects for the correct estimation of seismic life-cycle vulnerability. They are also used to discuss the advantage in terms of the safety and economy of including corrosion sensors for optimizing maintenance activities as opposed to purely inspection-based evaluations.