Given the limitations of the traditional Park-Ang dual-parameter damage model in evaluating the seismic performance of novel shear walls strengthened with high-performance fiber-reinforced concrete (HPFRC) and FRP reinforcements, low-reversed cyclic loading tests were conducted on 10 shear walls. This study reveals the underlying mechanisms governing the enhanced energy dissipation and improved ductility of shear walls strengthened with these high-performance materials. Subsequently, modified parameter calculation formulas accounting for the characteristics of the new materials were derived, establishing an improved dual-parameter damage model and corresponding performance evaluation criteria. The results indicate that the proposed parameter formulas exhibit excellent universality, proving applicable to both conventional reinforced concrete (RC) shear walls and novel composite-strengthened shear walls. The improved damage model can accurately quantify the damage evolution process of the shear walls. The calculated results are in good agreement with the experimental data, with an average error of only about 3%. Furthermore, the modified performance evaluation table accurately assesses the actual damage states of shear walls strengthened with dual materials and HPFRC. The findings of this study provide a valuable reference for the seismic design and damage assessment of highperformance shear walls.

Premature concrete spalling at the base of shear walls reinforced with carbon fiber-reinforced polymer (CFRP) grids often limits the full utilization of the high-strength properties of CFRP, compromising structural performance. To overcome this limitation, engineered cementitious composites (ECC) were introduced into the plastic hinge regions in this study, aiming to effectively leverage the mechanical advantages of CFRP grids and enhance the shear capacity and ductility of shear walls. Six shear wall specimens were designed, fabricated, and tested under cyclic loading: one conventional reinforced concrete (RC) shear wall, one CFRP grid-reinforced wall, and four shear walls reinforced with CFRP grids and incorporating ECC in the plastic hinge zones. The failure modes, hysteresis and skeleton curves, energy dissipation capacity, stiffness degradation, and reinforcement strain were investigated. Experimental results showed that ECC-enhanced specimens exhibited significantly improved ductility, crack resistance and energy dissipation compared to specimens without ECC, along with reduced crack propagation angles and reduced stiffness degradation. To accurately predict the shear behavior of these enhanced shear walls, an improved Modified Compression Field Theory (MCFT) was developed by integrating the effects of CFRP grids and the fibers in ECC. Finally, a novel algorithm based on this enhanced MCFT was formulated to calculate the shear capacity of the shear walls, with theoretical predictions closely matching the experimental results.

Brittle failures at the base of reinforced concrete shear walls under seismic loading remain a critical challenge for achieving structural resilience. Carbon Fiber Reinforced Polymer (CFRP) grids have been applied to mitigate this issue, achieving partial improvement. However, insufficient crack control at the wall base persists, restricting the full utilization of the tensile capacity of CFRP grids. This study explores a material-oriented enhancement strategy by incorporating Engineered Cementitious Composite (ECC) into the boundary elements of CFRPreinforced shear walls. The objective is to improve CFRP tensile utilization by applying ECC in boundary regions, improving material interaction and overall shear wall behavior under cyclic loading. Five shear wall specimens featuring various CFRP grid and ECC layouts were tested to evaluate their influence on crack initiation resistance, crack propagation, tensile utilization of CFRP reinforcement, and overall seismic performance. Experimental findings demonstrated that ECC-enhanced shear walls achieved markedly superior performance, with crack initiation load, ductility, peak strength, and energy dissipation increased by 115.7 %, 39.5 %, 13.5 %, and 40.5 %, respectively, relative to specimens without ECC. In addition, the refined finite element models incorporating the cyclic behavior of steel reinforcement were developed to accurately simulate damage evolution and crack propagation in shear walls. Numerical predictions agreed with experimental observations, exhibiting discrepancies of less than 15 % in strength and deformation metrics. The models accurately replicated observed crack patterns and failure mechanisms, confirming their validity and reliability. Parametric analysis was conducted to investigate the influence of ECC boundary width on synergistic mechanical performance in ECC-CFRP composites under cyclic loading.

The axial force will be altered as a result of the overturning influence exerted by both horizontal and vertical seismic events, as well as the secondary effects induced by gravitational loads. The variation of the axial force will greatly affect the seismic performance of reinforced concrete (RC) columns, thus warranting close attention. This paper proposes a hysteresis model of RC columns considering the cumulative damage effect under the action of variable axial force. First, three groups of cyclic loading tests were performed across three distinct groups. Subsequently, numerical analysis models were constructed, employing fiber-based finite element methods. Furthermore, according to the test and finite element simulation results, the existing damage value was modified to describe the degradation of the stiffness and load-bearing capacity. Next, through a regression analysis, the skeleton curve was established. Finally, the hysteresis behavior under the influence of variable axial load was ascertained. The results, when compared with the experimental data, show that the proposed hysteresis model can accurately describe the seismic performance of RC columns under the influence of variable axial force.

This research investigated the shear behavior of concrete beams reinforced with Carbon Fiber Reinforced Polymer (CFRP) bars and grids as longitudinal reinforcements and stirrups, in experiment and finite element (FE) methods. Five concrete beams were tested under a monotonical load and experienced shear failure as expected. The test variables including stirrup ratio and grid dimension were considered to investigate the interaction between grid and concrete, and the influence between the horizontal and vertical fibers of the grid. It found that reducing the grid dimension with the constant stirrup ratio could effectively improve the stress distribution of the grid and the shear capacity of the beam. The grid dimension greatly determined the shear capacity of specimens when the stirrup ratio changed in a small range. The horizontal fibers of the grid had anchoring effects on the vertical fibers and directly carried the tensile stress from concrete at the top and bottom of the beam. In FE analysis, the fiber composite layer was adopted to simulate the CFRP grid. The load-midspan deflection of specimens and strain development of the grid in the FE model showed good agreement with the tests. In parameter analysis, the grid configuration with the horizontal fiber arranged in the middle or upper part of the section was recommended.

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A series of experimental research has demonstrated superior hysteretic behavior, damage mitigation, and self-centering properties of concrete shear walls incorporating CFRP grid-steel reinforcement. Developing comprehensive theoretical and numerical models becomes crucial to assess the performance of these novel walls for structural design and application purposes. Based on the preliminary experimental investigation, a strength calculation method and numerical model for slender concrete shear walls with CFRP grid-steel reinforcement were proposed in this study. The calculation method provided a stable estimation for the loading capacity and ultimate compressive strain of edge concrete for the slender CFRP grid shear wall. The fracture strain of outermost longitudinal CFRP grid and ultimate compressive strain of edge concrete were suggested for design. The numerical model integrated hybrid reinforcements and utilized MVLEM to simulate the nonlinear hysteretic behavior of CFRP grid shear walls, effectively considering specimen failure mechanisms. The model can well capture the hysteretic behavior of the specimen, involving the peak loading, envelope curve, residual deformation, and stiffness degradation. Finally, the parametric analysis was conducted to further investigate the effects of axial compressive ratio and aspect ratio on shear walls with CFRP grid-steel reinforcement.

The metallic energy dissipation device (EDD) has been widely accepted as a useful tool for passive control of buildings against earthquakes. The distribution of metallic EDDs in a multi-story building may have significant influence on its seismic performance, which can be greatly enhanced if the distribution scheme is properly designed. This paper addresses the optimal distribution problem in the aim of achieving a desired level of performance using the minimum number of metallic EDDs. Five local search heuristic algorithms are proposed to solve the problem. Four base structures are presented as numerical examples to verify the proposed algorithms. It is indicated that the performance of different algorithms may vary when applied in different situations. Based on the results of the numerical verification, the recommended guidelines are finally proposed for choosing the appropriate algorithm in different occasions.

Carbon fiber reinforced polymer (CFRP) grid possesses not only the characteristic of FRP material, but the property of grid form with good integrity and bond behavior. It has been applied in structural reinforcement, and recently in new constructions. In this study, thirteen pieces of concrete shear walls, including two reinforced concrete (RC) specimens and eleven CFRP grid specimens with aspect ratios from 1.0 to 2.2, were tested under reversed loading. A new reinforcement configuration with CFRP grid was proposed in specimen design for partial and fully replacing steel bar. Parameters of reinforcement configuration, reinforcement ratio, and aspect ratio were considered in this investigation of cyclic behavior. The mechanical property of CFRP grid shear wall was revealed based on the evaluation of cyclic behavior. A comprehensive perspective of analysis from shear failure to flexural failure was compared and summarized. In general, the experimental results showed that specimens with CFRP grid performed higher load and displacement capacity and lower residual deformation. CFRP grid specimen showed smaller width of main cracks, surrounded by a large number of hairlike cracks, indicating a better stress distribution.

Carbon fiber reinforced polymer (CFRP), with the properties of light weight, high strength, and linear elasticity, has been widely applied in concrete structures. CFRP grid is one of the ideal alternatives to steel reinforcement to improve structural performance by continuously providing stress under large deformation. Considering the promising application and unique deformation characteristic, a modified method based on the uniaxial shear-flexure model (USFM) was proposed to investigate the deformation performance of CFRP grid shear wall. In the modified USFM (M-USFM), the property of CFRP grid was adopted into the analytical method to reveal the interaction of CFRP grid and concrete. Experimental results of specimens with different failure modes were compared to verify the acceptability of the modified USFM, considering the parameters of aspect ratio and reinforcement ratio. The modified USFM could well predict the load-displacement response and capture the initial stiffness, strength, and peak load point. The analytical lateral load was slightly higher than the experiment due to the difference between monotonic loading and cyclic loading, with the deviation of the peak load ranging from 4.9% to 10.8%. Moreover, the deformation was divided into shear, flexural, and slip components. For flexural failure specimens, the flexural component accounted for over 65% of total deformation at failure, consistent with the experimental result. For better application, the effect of reinforcement configuration and the confinement of CFRP grid to the internal concrete were deserved further investigation.

Welded steel connections have been extensively used in practical engineering for the superiority of welding. However, many welded structures under complex disaster conditions have exhibited significant low-cycle fatigue damage, resulting in catastrophic accidents and tremendous economic losses. In this study, the low-cycle fatigue performance of steel welded connections was experimentally investigated based on full-field strain collected by a 3D-digital image correlation (DIC) system. Analysis of fatigue life, failure mode, force-displacement hysteresis curve, strain-time curve, and strain distribution of butt-welded steel connections under low-cycle fatigue loading was implemented. The failure process under low-cycle fatigue was investigated based on the strain distribution and variation of the weld zone and heat-affected zone and further explained from the point of micromechanisms. Results reveal that the strains of the weld zone were higher with the increase of loading cycles than that of other positions. Hence, the final failure of the specimens had a preference for the weld zone where the weld metal exhibited tensile and compressive plastic strain asymmetry and cyclic softening characteristics. The plastic strain accumulation of the weld zones and heat-affected zones should be the main reason for the failure of specimens under low-cycle fatigue.

Fiber Reinforced Polymer (FRP) is one of the most ideal substitutes for steel reinforcement because of its low density, high tensile strength and excellent corrosion resistance. Carbon-FRP (CFRP) grid is one type that is commonly used in engineering and has shown promising results in shear strengthening of beams. In this study, eight concrete beams, including one steel reinforced concrete (RC) beam and seven concrete beams with CFRP grids in two configurations (parallel to longitudinal axis as stirrup or perpendicular to longitudinal axis), were tested until failure. The influence of variables on shear span ratio and shear reinforcement ratio were analyzed. All the eight beams experienced shear failure as expected. As the shear span ratio increased, the shear capacity decreased while the deflection of beam increased. CFRP grids parallel to the longitudinal axis could effectively reduce the deflection and increase the cracking load of specimens. When CFRP grids were laid perpendicular to the longitudinal axis, the maximum strength of CFRP grid can reach 84% of the ultimate strength and the contribution of CFRP grid stirrups to shear capacity was higher than that of steel stirrups. Finally, experimental results of shear capacity were compared with the theoretical ones calculated by various specifications.

Hybrid configuration of steel and fiber reinforced polymer (FRP) reinforcement is an effective approach for improving the overall performances of concrete members. The use of FRP grids in new constructions is increasing owing to their superior anchorage in concrete. In this paper, two types of hybrid carbon-FRP (CFRP) grids-steel shear walls were proposed to evaluate the cyclic behavior in contrast to conventional reinforced concrete (RC) shear wall. Six large-scale shear wall specimens were fabricated and tested under reversed cyclic loading. The investigate parameters include the reinforcement configuration and the hybrid proportion of steel and CFRP grids. Experimental results showed that all shear walls reinforced with CFRP grids exhibited higher load-carrying capacity and smaller residual deformation than those of RC shear wall. The load-carrying capacity of shear wall with CFRP grids placed as exterior layers (CSC) was 7.9% higher than the wall with CFRP grids in the center (SCS). In addition, the load-carrying capacity of shear wall with CSC arrangement increased with the proportion of CFRP grids in reinforcement, while there was an optimal hybrid proportion to the energy dissipation capacity. An increase of 25.8% in load-carrying capacity was achieved compared to RC shear wall with almost the same level of energy dissipation capacity when half of steel reinforcement was replaced by CFRP grids.

Punching shear action has been a focus for research in the field of civil engineering and using a fiber-reinforced polymer (FRP) grid is a novel configuration of the engineering materials. We present the test results of an experimental program on the punching shear performance of carbon-fiber-reinforced polymer (CFRP) grid reinforced concrete slabs. Six full-scale 1600 x 1600 x 150 mm slab specimens including one control steel reinforced concrete (RC) slab and five CFRP reinforced concrete slabs were fabricated and tested under monotonic loading till failure. The experiment aimed to investigate the effects of CFRP grids as flexural reinforcement and shear reinforcement on the punching behaviour of concrete slabs. Furthermore, three different shear reinforcement layouts were devised to verify which arrangement is better. Compared with the control RC specimen, the concrete slab with CFRP grids as flexural reinforcement reached almost the same punching strength with a lower reinforcement ratio. Moreover, adding extra shear CFRP grids was beneficial for improving the resistance of the concrete slab to punching. Among the three topological schemes of shear CFRP gird arrangements, the perpendicular layout was proven to be more effective than radial and rectangular arrangements.

Carbon fiber reinforced polymer (CFRP) is ideal for use in new construction owing to its light weight, high strength, and linear elasticity properties. CFRP grid is a common form of reinforcement that can enhance the structural integrity of components. In this study, six concrete shear walls, including one steel reinforced concrete (RC) wall and five walls reinforced with CFRP grids in two reinforcement configurations (vertically or horizontally laid), were tested until failure under cyclic loading. The comparison parameters include the aspect ratio, horizontal reinforcement ratio, and reinforcement configuration. The six specimens with aspect ratios of 1.0 and 1.4 experienced diagonal compression shear failure. The specimens with CFRP grids exhibited higher shear resistance in terms of a larger lateral drift, load capacity, strain, and less residual deformation, in particular, for walls with horizontal grids compared to conventional RC shear wall. The horizontally arranged CFRP grids significantly reduced the deformation concentration and improved the concrete confinement. Theoretical formulas based on the truss-arch model were developed to calculate the shear capacity of the concrete shear walls with CFRP grids.

Welded steel plates are widely used in several engineering applications. Usually, the material properties of the parent material are prior to the welded structure, which frequently causes the welding joint to fail due to fatigue. Predicting the fatigue life of a material is not a simple task, especially, when considering the welding joint with various constituents. In this study, a strain distribution for a steel plate weld joint was investigated using the digital image correlation technology to estimate the low cycle fatigue life. Using the reconstructed strain, a nonlinear model of strain was presented. Moreover, the rate change of strain was used as a fatigue failure criterion to predict the lifetime. The proposed model considers the strain-rules from two aspects: maximum value and change rate. With the information of the initial strain value, we can achieve the desired prediction for the fatigue life of the steel plate weld joint under the low cycle fatigue loading.

Annular reinforced concrete(RC) members are commonly used in bridge structures and offshore platforms. These RC members often fail under the combined actions of axial force, bending moment, shear force and torsion load in hazards of earthquake and wind. It is very important to study the failure mechanism of annular RC members under combined actions. This study proposes a model to analyze the ultimate strength of annular RC members under combined actions using limit failure theory. A new method is established to determine the geometric parameters of the warped failure surface, and the new calculation model for the ultimate strength is obtained using the equilibrium conditions based on the geometric parameters and the stress distribution on the failure surface. The proposed model calculations are compared with a series of experimental results of annular RC members, and they correspond well with the experimental results. The proposed model is feasible for engineering application.

混凝土板在集中荷载作用下容易发生冲切破坏,实际工程中已有板柱节点冲切破坏导致结构连续倒塌的案例.通过在混凝土板中配置碳纤维增强复材(CFRP)网格筋以提高混凝土板的抗冲切性能,开展了6个试件的抗冲切力学性能试验,得到了配置CFRP网格筋混凝土板的抗冲切承载力、CFRP网格筋应变、冲切范围内板的位移和板的破坏形态.试验结果表明,在混凝土板中配置CFRP网格筋可以提高混凝土板的抗冲切承载能力和抵抗变形能力,并且在出现冲切破坏后仍具有一定的承载能力.采用CFRP网格筋提高混凝土板抗冲切性能具有工程应用价值.

随着中国高铁建设的迅速发展,中国铁路技术水平逐渐走在世界前列.国内高铁站房多为大跨度空间结构,侧向刚度较弱.传统的抗震设计方法会导致构件截面过大,影响建筑使用功能、美观性和经济性,在高烈度地震设防区该问题尤为突出.本文以某位于高烈度地震设防区的高铁站房为工程背景,提出了屈曲约束支撑与黏滞阻尼墙联合控制的减震技术方案,对结构进行了多遇及罕遇地震作用分析与优化设计.研究结果表明,采用该联合减震方案可达到多遇地震作用下控制结构变形,罕遇地震作用下减少结构损伤的显著效果.