Abstract Aerodynamic interference effects (AIEs) between adjacent parallel decks have a pronounced influence on vortex-induced vibration (VIV). This study systematically investigates AIEs on VIV responses of a streamlined box girder parallel to twin bluff box girders. To clarify the characteristics of AIEs and evaluate the effectiveness of mitigation measures, wind tunnel tests and numerical simulations were conducted. The results show that the isolated streamlined box girder exhibits pronounced vertical VIV response at an angle of attack (AoA) of + 3 ° . When located upstream, the vibration amplitude at + 3 ° increases by about 83% compared with the isolated case, whereas it is completely suppressed when placed downstream. In the upstream condition, the strengthened dominant vortex intensifies the surface pressure fluctuations and enhances the contribution of the VIV driving region, thereby sustaining a stronger VIV response. In contrast, in the downstream condition, wake disturbance from the upstream bluff box girders suppresses the dominant vortex, disrupts the organized shedding process, and weakens the original VIV driving region, leading to the disappearance of stable VIV. Installing guide vanes provides limited mitigation of VIV, whereas optimizing the wind fairing is the most effective measure among those tested, since it suppresses the intrinsic VIV triggering flow structure of the streamlined box girder itself. These findings provide guidance for aerodynamic design and vibration control in similar parallel engineering applications.
Abstract On May 18, 2021, 76-story SEG Plaza in Shenzhen, China experienced sudden abnormal vibrations, leading to building resident evacuation and prompting considerable public concern. Given accessibility constraints and safety hazards, noncontact field measurements from SEG Plaza after the sudden vibration event were conducted using an interferometric radar system to explore the reason for the abnormal vibrations and assess its structural condition. Subsequent studies revealed that the abnormal vibrations originated from vortex-induced vibrations of the rooftop mast under specific wind conditions. Thus, the mast was removed as a mitigation measure. Its removal was followed by repeated noncontact measurements to evaluate the effectiveness of the mast removal measures. In displacement measurements of high-rise structures, weaker and higher structural vibration modes are prone to being overwhelmed by noise and dominant modes, resulting in inaccurate identification or loss of modal information. Therefore, a hybrid output-only modal identification scheme combining modal extraction, block bootstrap, and deterministic operational modal analysis techniques was adopted in this study to achieve weak modal enhancement and uncertainty quantification. Firstly, the accuracy and effectiveness of the hybrid scheme were validated by numerical simulations. The hybrid scheme then was applied to analyze the noncontact vibration measurements from SEG Plaza before and after the mast removal to identify its structural dynamic properties, explorie the cause of the abnormal vibrations, and evaluate the effectiveness of the mitigation measure. This study developed an efficient approach for noncontact vibration measurements and high-accuracy modal estimation of high-rise structures to assess the serviceability and structural safety of SEG Plaza.
Abstract Laser cladding (LC) is a 3D printing technology that has been increasingly applied to the repair and strengthening of civil engineering structures. However, research on the cyclic performance of laser-clad materials is currently limited. Therefore, 11 specimens were fabricated using LC technology, and experiments were conducted to investigate the mechanical properties and hysteretic behavior of the LC material under different cyclic loading protocols. The experimental results show that laser-clad 316L stainless steel has excellent energy dissipation capacity. LC 316L stainless steel subjected to cyclic loading demonstrates mixed hardening behavior, including isotropic hardening and kinematic hardening, along with a pronounced Bauschinger effect. The envelope curve of 316L stainless steel under cyclic loading differs from its monotonic tensile curve, with the Ramberg–Osgood model proving effective in characterizing the envelope behavior. The elastic modulus of 316L stainless steel initially decreases during the first few loading cycles before stabilizing with accumulated plastic strain. The Chaboche model was implemented to predict the stress–strain response of LC 316L stainless steel, with parameter calibration and subsequent validation confirming the predictive accuracy of the model.
Abstract Accurately capturing the mechanical behavior of externally prestressed steel–concrete composite (EPSCC) girders is challenging due to the unbonded nature of external tendons and the occurrence of slip at the steel–concrete interface. This paper presents a reliable, design-oriented method for estimating tendon stress and flexural stiffness of EPSCC girders under serviceability conditions. First, analytical expressions are derived to determine the slip-induced deflection in EPSCC girders. Subsequently, a beam–tendon deformation model is developed based on global deformation compatibility, from which an analytical model for the stress increment in external tendons is further derived. Using these foundations, an analytical procedure is developed to calculate girder deflection that accounts for the interface slip effect. Then, a segmented line is introduced to depict the distribution of slip-induced strain, which enables the derivation of a straightforward equation for the effective flexural stiffness of the EPSCC girder. Finally, practical design recommendations are proposed for calculating the deflection of continuous EPSCC girders. Comparisons with experimental results from 18 simply supported and 13 continuous EPSCC girders demonstrate that the proposed method offers greater consistency and accuracy than the design methods considered in this study.
Abstract This study investigates the seismic performance of postcast prefabricated concrete columns reinforced with ultrahigh-performance concrete (UHPC) and incorporating internal steel sections at their joints. Through low-cycle reversed loading tests conducted on two prefabricated concrete (PC) columns with UHPC-reinforced steel joints and one RC column cast-in-place, the seismic performance differences between PC and RC are compared. The study examines the influence of varying locations of prefabricated joints on hysteretic behavior, energy dissipation capacity, and deformation capability. The results indicate that the prefabricated columns reinforced with internal steel sections and UHPC connections exhibit higher load-bearing capacity and stiffness, significantly enhancing their seismic performance. Specifically, the PC-2 specimen, with its joint located at the column base, displays excellent initial ductility and energy dissipation but experiences a reduction in load-bearing capacity due to UHPC cracking at the joint in later stages. Conversely, the PC-1 specimen, featuring a joint positioned 450 mm above the bearing platform, exhibits comparable deformation and energy dissipation capabilities to the RC column due to unhindered plastic hinge formation, demonstrating superior seismic performance. The formula for calculating the flexural capacity of I-shaped steel-reinforced concrete sections, based on the internal force equilibrium condition and the lower-bound theorem of plasticity theory, yields a calculation error of less than 10%, confirming its accuracy and providing a scientific basis for relevant design optimizations.
Abstract Railway corridors are often located in coastal areas, making them vulnerable to storm-induced failures. This study develops a framework to analyze performance of coastal rail infrastructure against storm-induced surge and waves with the consideration of climate change and sea-level rise. The procedure shifts from traditional scenario-based analysis to a fully probabilistic storm hazard model by using synthetic storm data sets. This probabilistic hazard model is integrated with fragility models for key failure modes, including ballast and embankment scour for inland tracks and deck uplift for ballast-deck concrete bridges. A sequential Monte Carlo simulation is then adopted to estimate life expectancies for rail track components considering long-term effects from climate change and sea-level rise. A case study is performed for rail tracks owned by CSX Transportation and Canadian National Railway spanning from Alabama to Louisiana. The results indicate potential vulnerabilities for approximately 18% of ballast-deck bridges and 34% of inland tracks. Furthermore, the effectiveness of various mitigation strategies, such as elevation and relocation of tracks and bridges, is investigated. This study provides a quantitative framework to estimate coastal railroad vulnerabilities, prioritize mitigation solutions, and devise retrofit actions.
Abstract Cable-supported grid structures, integrating rigid and flexible components, represent a lightweight and efficient structural form. Conventional topology design methods based on single-member units often produce incomplete upper grids and lower cable-supported structures containing redundant, irregular, and discontinuous cables, which complicate practical construction. This paper proposes a multimember unit–based topology optimization model grounded in graph theory. The approach preserves grid integrity while selecting cable topologies from predefined arrangements, ensuring the engineering feasibility of the optimized designs. The model supports coupled topology optimization, allowing cables and bars to be arranged simultaneously, an approach not found in existing literature. By preprocessing member groups, the method effectively accommodates slidable nodes, a challenge that conventional approaches cannot address. Additionally, the multimember unit–based formulation improves computational efficiency over the single-member unit–based approach. The efficacy of the proposed method is demonstrated through several numerical examples and validated by finite-element analysis.
Abstract Stainless steel built-up I-profile are frequently designed with webs significantly more slender than their flanges and greater material strength in the flanges in case of hybrid sections. Given the fundamental load case of pure compression or bending, the compressed flange can develop significant postlocal-buckling strength, approaching its fully plastic capacity, whereas the web reaches only its local buckling resistance, a long-overlooked failure mechanism not currently captured by current design approaches. The effect is particularly pronounced in stainless steel, whose nonlinear stress–strain response and pronounced strain hardening further enhance this reserve capacity. In this paper, experiments are first used to validate a finite element model of such behavior. Following validation, a parametric study is conducted to evaluate the influence of geometric and material parameters on the ultimate strengths. The study includes both homogeneous and hybrid built-up sections, where the homogeneous sections are made of four grades (EN 1.4062, EN 1.4462, EN 1.4307, and EN 1.4404), and the hybrid sections are made using four hybrid combinations covering a wide range of cross-sectional slenderness. A total of 1,325 homogeneous and 955 hybrid FE models are developed, focusing solely on strong flange behavior. The performance of the codified Effective Width Method (EWM), Direct Strength Method (DSM), and Continuous Strength Method (CSM) is evaluated against the numerical results. The comparison highlights that element interaction and local buckling strength reductions cause I-sections with slender webs and stocky flanges to exceed the codified strength predictions. A modified Direct Strength Method (mDSM) approach is then proposed. By introducing two new parameters, Ω and α , to distinguish between cross-sectional behaviors and better account for strong flange effects, we address the limitations of traditional “whole section” methods while retaining their inherent simplicity, providing greater accuracy and less scatter than any of the codified methods. A reliability assessment provides evidence that the new equation achieves the codified target for acceptable probability of failure when combined with the current resistance factor.
Abstract This paper briefly summarizes the results from experimental and numerical investigations conducted on full-scale planar concrete-filled composite plate shear walls (C-PSW/CF) with bolted splice connections. These experimental results and numerical models are used to develop and verify design methods for estimating the moment capacity ( M n ) and ultimate rotation ( θ u ) of bolted splice connections using the instantaneous center of rotation method (ICM) and a less accurate but simpler method (SM). The shear force–deformation relationship for fasteners (blind bolts and threaded rods in sleeves) and the beneficial effect of concrete are incorporated into the design methods. These shear force–deformation relationships and component-based models for fasteners (blind bolts in particular) are developed and validated using corresponding fastener test results and numerical models. The experimental and numerical results from the planar C-PSW/CF walls are used to extract and validate the fundamental moment–rotation ( M - θ ) relationships for bolted splice connections. These relationships are then used to develop and validate an empirical model for the M - θ relationship of bolted splice connections. These models utilize the moment capacity ( M n ) and ultimate rotation ( θ u ) calculated using the design methods (ICM or SM) or numerical models of the connections. The effects of connection flexibility (i.e., M - θ relationship) on the lateral stiffness of the overall C-PSW/CF wall system are evaluated, and design recommendations for limiting the reduction in lateral stiffness of the system are proposed.
Abstract Adaptive structures are able to autonomously adjust their morphology through the actuators to adapt to external conditions, offering material and energy efficiency. The multistable tensegrity structure is very suitable for adaptive structures due to its light weight and multiple stable states. However, the operational energy required during their stable state transformation (SST) remains insufficiently studied. This paper proposes an operational energy analysis method for adaptive multistable tensegrity structures with internal actuators. First, a form-finding method for tensegrity structures with internal actuators is introduced. Next, an actuation strategy consisting of linear working and recovery stages is designed, and the continuous actuation process is discretized into multiple small steps. By performing form-finding multiple times for each substep, the tracking of the multistable tensegrity structures during the actuation process is realized. The operational energy of the internal actuator is calculated per step and summed to obtain the total operational energy during actuation process. Three numerical examples validate the method and identify a minimal-energy actuation strategy, i.e., actuation threshold. Further analysis reveals the differences between internal and external actuation, as well as the influence of the prestress level on the actuation threshold and operational energy. The results provide theoretical and technical support for actuation strategy optimization and energy efficiency evaluation in adaptive multistable tensegrity structures.
Abstract Concrete-filled composite coupling beams provide an efficient alternative to RC beams for connecting shear walls, due to their enhanced structural performance and accelerated construction schedule. However, their rotation capacity is limited by strain concentration at the beam-to-wall connection and the relatively low fracture strain of conventional carbon steel. To address these issues, this study introduces an innovative composite coupling beam that incorporates rib plates at the connection and uses stainless steel tubes. Nine cyclic tests were conducted. The results showed that the use of rib plates enhanced both strength and rotation capacity by shifting the fracture location away from the connection, and the stainless steel further improved the rotation capacity by delaying the fracture initiation. Finite-element (FE) models then were developed and benchmarked to conduct additional parametric analyses. The analysis results showed that the thickness and grade of the stainless steel plate influenced both the strength and ductility, whereas the compressive strength of concrete had a minor effect. Finally, the applicability of AISC 360-22 for estimating flexural strength was evaluated and modifications are proposed.
Abstract In reinforced concrete walls with low aspect ratios and construction joints, shear-sliding is a critical failure mode under earthquake loading. In this study, a backbone curve model was developed to capture the nonlinear response of walls with shear-sliding failure mode. The shear-sliding strength was defined as the sum of shear-friction strength in the compression zone and dowel action strength in the tension zone, considering the effect of flexural moment. Deformation capacity was defined as the sum of flexural, shear, and shear-sliding components, with shear-sliding displacement limited by reinforcement fracture due to catenary action in the tension zone. The proposed model was validated using existing test results from 43 wall specimens with construction joints. The model predicted both the shear-sliding strength and deformation capacity of the walls with reasonable accuracy.
Abstract Embedded crush of timber surrounding shear connectors and high accuracy of bolt installation are two critical issues for steel-cross laminated timber (CLT) composite (SCLTC) beams with bolted connections. This study proposes novel grouted shear stud (GSS) connectors to overcome the abovementioned drawbacks. The shear performance of the GSS connectors was evaluated via push-out tests first and then four-point bending tests were performed to assess the flexural behavior of the SCLTC beams with GSS connectors. The test results indicate the GSS connectors mainly failed by shear yielding of studs and slight block rotation. The load-slip curves of the connectors were typically characterized by an initially linear-elastic response followed by a nonlinear ascending branch and a post-peak descending branch. The SCLTC beams mainly failed by local crush of CLT in compression and yielding of steel beam, indicating a pseudo-ductile failure mode. The load-midspan deflection curves of the beams were generally characterized by a bilinear response with an obvious yielding plateau. The initial composite action coefficient ranging from 83.5% to 95.9% indicates relatively rigid shear connectors were developed. The transversal strain of CLT slab was distributed in the shape of a saddle with edge strain higher than middle strain and termed negative shear lag effect. The finite element (FE) model validated by experimental results was employed for parametric analysis. Finally, a calculation model considering interfacial slip effects was developed to predict the full-range nonlinear behavior of the SCLTC beams. Good agreement was observed between the calculated results and the experimental data.
Abstract To address the structural complexity and construction difficulties associated with conventional cellular steel–concrete joints (SCJs), this study proposes an innovative noncellular steel–ultrahigh-performance concrete (UHPC) joint (SUJ) for hybrid continuous girder bridges, in which headed studs are solely used to connect the steel box girder with monolithic UHPC grout. The proposed SUJ has been successfully implemented in the Yuanshui Bridge of the Yiyang–Changde Expressway ( G 55 17 ) in China, demonstrating its practical feasibility. Based on this joint configuration, push-out tests were conducted to investigate the shear behavior of long stud groups ( D 22 × 180 mm at 200-mm spacing), and the effects of stud diameter, aspect ratio, spacing, and configuration were systematically evaluated. Test results showed that all specimens failed by stud shank failure, and the grouped-stud arrangement resulted in an average 6.8% reduction in shear capacity per stud compared with single studs; meanwhile, increasing the aspect ratio from 3.6 to 8.2 led to a 6.6% decrease in shear capacity. Although denser arrangements using smaller diameter studs achieved comparable total shear resistance at similar shear areas, the elastic shear stiffness per stud of grouped studs was significantly reduced, and the interfacial slip between steel beams and UHPC blocks failed to satisfy the ductility requirement of current standards. Parametric analysis further confirmed that stud diameter plays a dominant role in shear capacity, whereas reduced stud spacing and increased stud row number adversely affect both shear capacity and ductility. Accordingly, an empirical formula incorporating a reduction factor related to stud row number is proposed to predict the ultimate shear resistance of grouped long studs, showing good agreement with experimental results.
Abstract With growing demand on low-carbon and fire-safe building solutions, timber–concrete composite (TCC) floors have emerged as a sustainable and efficient alternative. This paper provides a critical review of the fire performance of slab-type TCC floors, with an emphasis on studies reported in the past five years, including 25 full-scale furnace tests. Results show that cross laminated timber (CLT) concrete floors are prone to char fall-off, leading to sharp inner temperature rises and highly variable fire resistance (30–214 min), mainly influenced by load ratio, lamella thickness, and connection type. The fire resistance of slabs generally exceeded 90 min under service loads, and higher load ratios caused earlier failure. By contrast, nail-laminated timber– and laminated veneer lumber–concrete systems exhibited stable charring and consistently higher resistance ( > 190 min ). Emerging simulation approaches that model char fall-off and temperature-dependent connector degradation show improved agreement during extended fires, though broader validation is still needed. Simplified analytical methods, such as the γ -method, provide useful estimates but require calibration across load levels. Future research should refine delamination modeling, incorporate temperature-dependent connector behavior, and recalibrate analytical methods using full-scale data to ensure reliable fire design of TCC floors.
