Abstract ：

为实现高耐久功能可恢复结构,设计了钢-FRP复合筋(steel-FRP composite bar,SFCB)替代钢筋,塑性铰区使用高延性水泥基复合材料(engineered cementitious composites,ECC)替代混凝土的新型组合柱.在0.13轴压比下,对SFCB-ECC-混凝土组合柱进行低周往复荷载试验研究.评估了 SFCB中FRP体积分数(0％,43.6％,100％)和塑性铰区基体类型(ECC,混凝土)对组合柱抗震性能和可恢复性的影响.之后通过OpenSees进行了轴压比、SFCB配筋率和ECC强度的参数分析.结果表明:SFCB可使试件获得稳定的二次刚度,在2％位移角前,试件无需修复即可快速恢复原有功能;组合柱残余变形随SFCB中FRP体积分数增加而减少,但其初始刚度和峰值承载力也相应降低;在塑性铰区使用ECC可进一步减少残余位移,同时显著提高峰值承载力和延性;参数分析显示增大轴压比将提高SFCB-ECC-混凝土组合柱承载力,但会降低延性;随SFCB配筋率和ECC强度提高,组合柱承载力也相应增大;在实际工程中可合理设计SFCB和ECC材料特性以满足特定结构刚度、强度和可修复性的要求.

Keyword ：

OpenSees 抗震性能 桥梁工程 可恢复 组合柱 高延性水泥基复合材料 钢-FRP复合筋

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Abstract ：

本实用新型公开了一种设置通长自复位筋的既有桥墩加固结构，包括从下至上连接的承台、桥墩和盖梁，还包括连通设置在所述承台、桥墩和盖梁内的既有纵筋，所述桥墩顶部和底部的外层部分向内开设内槽，所述内槽露出所述既有纵筋，露出的所述既有纵筋外层包裹一层胶带，所述内槽位置浇筑UHPC混凝土。利用UHPC混凝土和FRP布约束桥墩，增强桥墩强度，减小桥墩损伤，从而实现震后的低损伤和快速恢复。此加固结构的桥墩基本不改变桥墩外形，而且采用价格低廉的FRP筋和FRP布，成本较低，施工方便，易于推广。

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Abstract ：

Traditional fabric-reinforced cementitious matrix (FRCM) materials are based on brittle substances, leading to large crack widths post-cracking and subsequent failure of the FRP grid. Engineered Cementitious Composites (ECC) and Ultra-High Performance Concrete (UHPC) offer alternatives to address these issues. However, the coupled influence mechanisms of FRP types and layers on the mechanical properties of FRCM, and their interaction with ECC and UHPC, are not well researched. This study investigates the tensile behavior of ECC and UHPC composites reinforced with carbon fiber (CFRP) and basalt fiber (BFRP) grids. A total of 22 sets of tests were conducted to explore the effects of FRP type, number of layers, and matrix thickness on failure mode, initial elastic modulus, strain-hardening modulus, cracking stress, peak stress, and strain. The results showed that increasing the number of grid layers from 1 to 6 enhanced tensile strength by up to 322.5 %, peaking at 5 layers before declining. Matrix thickness had a minimal impact on mechanical behavior during the elastic stage but significantly affected modulus and peak strength during the strain-hardening stage, with reductions of up to 14.57 % and 85.95 %, respectively. Additionally, the tensile properties of FRP-ECC and FRP-UHPC composites were markedly different, with the deformation capacity of FRP-ECC being 2-4 times higher than that of FRPUHPC. This was attributed to differences in the strength and elongation of the FRPs and their interaction with the reinforcing fibers. FRCM effectively combines the advantages of both materials, enhancing the mechanical properties of the composites and offering potential for cost-effective, durable structural solutions.

Keyword ：

Uniaxial tensile test Ultra-High Performance Concrete (UHPC) Engineered Cementitious Composites (ECC) Fiber-reinforced polymer (FRP) grid Mechanical properties

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Abstract ：

To investigate the strengthening effectiveness of Fabric-Reinforced Cementitious Matrix (FRCM) composites on shield tunnel segments, this study conducted four-point bending tests on FRCM composite panels. The influence of different cementitious matrices (engineered cementitious composite, ECC; ultra-high-performance concrete, UHPC) on the flexural behavior of FRCM panels was systematically analyzed. Numerical simulations were additionally conducted to analyze deformation behavior, damage progression, and stress variations in steel reinforcements within standard structural segments strengthened with FRCM composite panels. A parametric analysis was performed to assess the effects of cementitious matrix type, panel thickness, and carbon fiber-reinforced polymer (CFRP) grid layers on the reinforcement efficiency. The experimental results demonstrated that FRCM composite panels exhibit superior flexural performance. Specimens with UHPC matrices exhibited higher cracking stresses and enhanced flexural stiffness during the elastic phase, while those with ECC matrices demonstrated advantages in post-peak hardening behavior and energy dissipation capacity. Both matrix types achieved similar cracking strains and comparable ultimate flexural strengths. Numerical simulations revealed that FRCM strengthening significantly improves the ultimate flexural bearing capacity of segments while effectively controlling deformation. For UHPC-based FRCM reinforced segments, the ultimate bearing capacity increased with both UHPC thickness and CFRP layer quantity. In contrast, ECC-based FRCM reinforced segments exhibited capacity enhancement primarily correlated with CFRP layer addition, with negligible sensitivity to ECC thickness variations.

Keyword ：

numerical simulation flexural performance tunnel reinforcement FRP grid UHPC ECC

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Abstract ：

Increasingly heavy urban traffic exacerbates vehicle impacts on reinforced concrete (RC) bridge columns, possibly leading to shear failure and structural collapse. To enhance the dynamic shear resistance of these columns, fiber reinforced polymers (FRPs) made from recycled polyethylene terephthalate (PET) plastic bottles were used for external strengthening. PET FRPs offer an eco-friendly alternative by repurposing plastic waste, reducing pollution, and promoting circular economy. This study focused on the dynamic shear responses of RC columns strengthened with PET FRPs. The influences of FRP types and number of FRP layers were experimentally revealed in terms of the failure modes, impact force, reaction force, shear force and impact force-displacement relationship. It was found that significant shear damage occurred in RC columns under horizontal impact loads, with carbon FRPs (CFRPs) strengthening unable to alter the failure mode. Nevertheless, the use of PET FRPs transformed the failure mode to a flexural-shear mode, significantly reducing the impact duration, maximum and residual displacements, and energy dissipation. Moreover, a finite element model was validated to describe the impact resistance of PET FRP-strengthened RC columns, as supported by experimental data. A parametric study further investigated the effects of impact velocity, impact mass, number of FRP layers, and reinforcement ratios on the dynamic shear responses. Based on the truss-arch model, a dynamic shear strength model was proposed and can well predict the dynamic shear capacity of FRP-strengthened RC circular columns. © 2025

Keyword ：

Carbon fiber reinforced plastics Fiber reinforced concrete Shear strain Insertion losses Recycling Fracture mechanics Cracks

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Abstract ：

To address the complexity and inefficiency of the current experimental and numerical simulation methods, a simplified analysis and prediction method for the dynamic response of fiber-reinforced polymer (FRP)/steel hybrid-reinforced concrete beams under impact loads was investigated. Firstly, a dynamic bending-shear resistance model of hybrid-reinforced concrete beams was established. Subsequently, based on this model and considering the stress wave propagation effect, an improved two degree of freedom simplified analytical model was proposed to predict the impact response of hybrid-reinforced concrete simply supported beams, and the accuracy of the model was verified. Finally, based on the dimensional analysis, an empirical prediction model of the peak displacement and impact force time history curves of the hybrid-reinforced beams was established by regression analysis of the results of 120 sets of impact conditions calculated with the two degree of freedom model. The results show that the prediction error of the model was basically within 20%, which provides an effective and simplified calculation method for the engineering practice of the hybrid-reinforced concrete simply supported beams under impact loads. © 2025 Chinese Vibration Engineering Society. All rights reserved.

Keyword ：

Carbon fiber reinforced plastics Fiber reinforced concrete

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Abstract ：

To solve the corrosion problems of steel bars in reinforced concrete (RC) structures and brittle damage in pure fiber-reinforced polymer (FRP) reinforced concrete structures, hybrid-reinforced concrete (hybrid-RC) structures combining FRP and steel bars have been proposed. The studies on hybrid-RC structures have focused on static loading conditions, while the structures may also be subjected to impact loading, leading to significant damage. Due to the difference in the properties of FRP and steel bars, FRP bars are always equivalent to steel bars based on different principles in calculation and design, e.g., equal-area, equal-strength, and equal-stiffness. In this work, to investigate the impact behavior of hybrid-RC beams and the influence of design principles, 17 specimens were designed and modeled using Basalt FRP (BFRP) bars replacing steel bars. The results show that the equalstrength-reinforced beams have the smallest damage extent, and the largest impact and reaction forces. While the equal-stiffness-reinforced beams have the greatest damage extent, the beams exhibited a better deformation and deformation recovery capacity. The impact resistance of equal-area-reinforced beams is between the remaining two. Besides, to fully utilize the material performance, for structures with high deformation and damage control requirements, it is recommended to use equal-strength-reinforced beams; for structures that need to reduce residual deflections, impact forces and reaction forces, equal-stiffness-reinforced beams are suggested; and if the economy of the materials is considered, equal-area-reinforced beams may be the preferred choice. The current study could be a reference for impact-resistant design for hybrid-RC structures.

Keyword ：

Concrete beam Hybrid reinforcement Basalt fiber-reinforced polymer (BFRP) bars Impact response Equivalence design principle

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Abstract ：

The plastic hinge region of bridge columns dissipates seismic energy under earthquakes, effectively constraining the extent of structural damage through localized plastic deformation. To enhance the seismic resilience of this critical region, this study proposes replacing the conventional concrete in the plastic hinge zone with engineered cementitious composite (ECC) and externally wrapping it with fiber-reinforced polymer (FRP). This approach is expected to significantly enhance structural damage tolerance, mitigate longitudinal bar buckling and steel reinforcement corrosion. The seismic performance of this new type of bridge column was investigated via quasi-static tests. The parameters were FRP type (large rupture strain FRP and traditional glass FRP) and the number of FRP layers (1, 2, and 3 layers). The combination of ECC and FRP exhibited outstanding seismic performance in terms of ductility, energy dissipation capacity, and damage control capacity. The existing equivalent plastic hinge length expressions of FRP-confined reinforced concrete (RC) members were evaluated and the proposed formula considering the confinement stiffness for FRP-confined ECC bridge columns delivered more accurate predictions. Nonlinear finite element analysis was performed and was shown to reproduce the hysteretic curves of the column models with acceptable accuracy. A parametric study was conducted to further analyze the effects of the wrapping height of FRP, axial compression ratio, and longitudinal reinforcement ratio on the peak lateral force and ductility of FRP-reinforced ECC bridge columns. Finally, design recommendations were provided for the engineering design of FRP-reinforced ECC structures. © 2025 Elsevier Ltd

Keyword ：

Engineered cementitious composite Glass fiber reinforced plastics Seismic design Concrete products Model structures Structural health monitoring Seismic response Structural dynamics Fiber reinforced concrete Earthquake effects Carbon fiber reinforced plastics

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Abstract ：

The steel-FRP composite bar (SFCB) is an ideal reinforcement choice for structures aimed at enhancing durability and resilience. However, research on the seismic applications of SFCBs has primarily focused on flexure-dominated concrete columns, with limited experimental investigation into columns subjected to axial-shear-flexure interaction. To address this gap, quasi-static tests were conducted on six short concrete columns to evaluate their seismic performance. The study examined the effects of key variables, including longitudinal reinforcement type, the spacing of GFRP stirrups, and shear span-to-depth ratios. The results show that all specimens exhibited a shear-flexure failure mode. Compared to the steel-reinforced short column, SFCBreinforced short columns with an equal stiffness design method demonstrate better seismic performance, including reduced shear-flexure damage, similar initial stiffness, higher load-bearing capacity, and increased resilience. Reducing the GFRP stirrup spacing enhances the shear capacity of SFCB-reinforced columns, thereby reducing shear deformation and improving ductility. A decrease in the shear span-to-depth ratio significantly increases the stiffness and overall loaddisplacement curves of SFCB-reinforced columns, with a slight improvement in resilience. An analytical model incorporating axial-shear-flexure interaction was developed using the uniaxialshear-flexure model (USFM) approach and validated by comparing the predicted envelope curves with the experimental results.

Keyword ：

Uniaxial-shear-flexure model (USFM) SFCB Short column Seismic performance

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Abstract ：

Novel engineered cementitious composite (ECC) columns reinforced with hybrid reinforcement (longitudinal steel-FRP composite bars (SFCBs) and GFRP stirrups) exhibit superior load capacity, ductility, and corrosion resistance. However, the lack of research on their axial compression behavior and the key parameters seriously limits their safe application. To address this research gap, experimental investigations of 22 column specimens were conducted to evaluate their axial compression behavior. The effects of matrix type, ECC strength, hybrid reinforcement, longitudinal reinforcement type, longitudinal reinforcement ratio, and volumetric stirrup ratio were discussed. The test results show that, compared to concrete columns, unreinforced and reinforced ECC columns have 12.5 % and 10.7 % higher load capacity, respectively, with enhanced ductility characteristics. The use of ECC effectively reduces specimen damage. Longitudinal SFCBs can work synergistically with ECC, efficiently maintaining their integrity before ECC crushing. Notably, replacing longitudinal steel bars with equalstiffness SFCBs leads to similar compression behavior of columns, including axial load capacity and ductility. The excellent tensile properties and fiber bridging effect of ECC slow the development of stirrup strain and prevent premature slip of GFRP stirrups. Furthermore, a modified prediction model of axial load capacity was proposed, which has excellent accuracy for this novel type of column.

Keyword ：

Engineered cementitious composite (ECC) Steel-FRP composite bar (SFCB) GFRP stirrup Prediction model Axial compression behavior

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