【作者】 沈捷；

【导师】 黄镇；

【作者基本信息】 东南大学 ， 防灾减灾及防护工程， 2021， 硕士

【摘要】 传统钢筋混凝土剪力墙在中大震作用下会出现混凝土压碎剥落,钢筋受压屈曲,剪力墙产生较大的残余变形,导致剪力墙震后维修加固难度大、费用高。碳纤维复材网格(CFRP)具有轻质、高强、线弹性等特性,同时网格形式具备双向受力能力,整体性、锚固性好。在混凝土剪力墙结构的关键部位配置CFRP网格筋代替钢筋(或部分钢筋),可改善剪力墙的受力性能。本文通过试验研究、数值模拟及理论分析相结合的方法,对配置CFRP网格筋混凝土剪力墙的抗震性能和设计方法开展了系统研究。研究主要内容和成果如下:(1)通过对13片配置CFRP网格筋和钢筋的混凝土剪力墙试件进行低周反复加载试验,分析试件加载过程中的受力及变形特征,以钢筋混凝土剪力墙为对照,研究了剪力墙在不同剪跨比、配筋率以及配筋形式下的抗震性能,揭示了试件在不同破坏模式下的传力机制与破坏机理。分析结果表明,对于不同剪跨比的混凝土剪力墙试件,配置CFRP网格筋可有效限制裂缝宽度,使裂缝分布更加均匀密集。其中,配置水平CFRP网格筋可对混凝土产生显著约束作用,增强核心区混凝土的抗压强度和极限变形能力。因此,配置CFRP网格筋混凝土剪力墙与钢筋混凝土试件相比,拥有更高的极限承载力和更大的侧向变形能力。由于CFRP网格筋具有线弹性特征,配置CFRP网格筋剪力墙的残余变形显著低于钢筋混凝土混凝土试件,具有较好的自复位性能,且该类试件的刚度退化速率较低,对于剪跨比较大的试件体现出二次刚度。(2)当配置CFRP网格筋混凝土剪力墙试件的剪跨比小于等于1.5时,加载中剪切效应显著,选用考虑弯剪耦合的多垂直杆模型(SFI-MVLEM)可较好地反映试件受力性能,峰值荷载以及其对应的位移模拟较为准确;当配置网格筋剪力墙试件的剪跨比大于1.5时,加载中以弯曲效应为主,剪切效应不显著,选用多垂直杆模型(MVLEM)可较好地模拟试件滞回曲线、初始刚度、承载力和残余变形等特征。此外,轴压比在一定范围内增大可有效提升混凝土剪力墙的承载力,而当轴压比超出该范围后,试件承载力出现下降趋势,不利于构件受力性能的提升,且轴压比变化对剪跨比较小的试件影响较大。(3)基于桁架-拱模型建立的配置CFRP网格筋混凝土剪力墙的力学模型和抗剪承载力设计方法,具有明确的物理概念,可较为精确地计算剪力墙在考虑轴压作用下的抗剪承载力,变异系数为0.1861;基于截面分析法建立的配置CFRP网格筋混凝土剪力墙的力学模型和抗弯承载力设计方法,考虑了试件破坏时的受力特征,抗弯承载力理论值与试验结果吻合较好,变异系数为0.1082;基于单轴弯剪模型(USFM)建立的配置CFRP网格筋混凝土剪力墙的变形计算方法,考虑剪力墙在压-弯-剪复杂受力状态下的变形特征,将剪力墙的变形划分为弯曲变形、剪切变形与滑移变形。理论计算获得的骨架曲线稍大于试验结果,整体趋势与试验较为吻合,可较准确地计算剪力墙的荷载-位移曲线。更多还原

【Abstract】 Traditional reinforced concrete(RC)shear walls will be crushed and spalled under the effect of medium and large earthquakes and the reinforcement will suffer buckling under pressure,resulting in large residual deformation of the shear walls.It will make the postearthquake repair and reinforcement of shear walls difficult and costly.Carbon fiber composite(CFRP)grid has the characteristics of light weight,high strength,and linear elasticity,while the grid form has bi-directional force capacity,good integrity,and anchorage.To improve the mechanical performance of concrete shear wall,CFRP grid is applied in the key position of the wall instead of steel bars.In this paper,a systematic study on the seismic performance and design methods of configured CFRP grid reinforced concrete shear walls is carried out through a combination of experimental studies,numerical simulations,and theoretical analysis.The main contents and results are as follows:(1)13 pieces of concrete shear walls with CFRP grids and steel bars were tested until failure under cyclic loading.Through analyzing the failure characteristics of specimens,the seismic performance of concrete shear walls under different shear span ratios and reinforcement configurations is studied.The load transferring mechanism and failure mechanism of specimen under different failure modes are revealed.As for the specimens with different shear span ratios,CFRP grid can effectively limit the crack width and make the crack distribution more uniform and denser.Moreover,horizontalil laid CFRP grid can significantly confine concrete and enhance its compressive strength and ultimate deformation capacity in the core area.Therefore,compared with RC specimens,specimens with CFRP grids have higher ultimate loading capacity and greater lateral deformation.Due to the linear elasticity and lower elastic modulus of CFRP grid,the residual deformation of shear walls with CFRP grids is lower than that of RC specimens,which has better self-reset performance.Moreover,the stiffness degradation rate of such specimens is lower,and secondary stiffness is reflected for specimens with large shear spans.(2)When the shear span ratio of concrete shear wall with CFRP grids is no more than 1.5,the shear effect is significant during loading.The SFI-MVLEM model considering the flexureshear coupling can better reflect the mechanical properties of the specimen.The peak load and its corresponding displacement are more accurate.When the shear span ratio of the shear wall with CFRP grids is greater than 1.5,the flexure effect is dominant during loading,and the shear effect is not significant.The MVLEM model can be used to simulate the hysteresis curve,initial stiffness,loading capacity and residual deformation of the specimen.Moreover,when the axial compression ratio increases within a certain radius,the loading capacity of the concrete shear wall can be effectively improved.However,when the axial compression ratio exceeds the range,the loading capacity of the specimens shows a downward trend,which is not conducive to the improvement of the mechanical properties.The variation of the axial compression ratio has a greater effect on the specimens with relatively small shear spans.(3)Based on the truss-arch model,the mechanical model of concrete shear wall with CFRP grids has a clear concept,which can accurately calculate the shear loading capacity of the shear wall under the consideration of axial compression.The coefficient of variation is 0.1861.Based on the section analysis method,the mechanical model of concrete shear wall with CFRP grids is established.The mechanical characteristics of the specimens are considered.The theoretical value of flexural bearing capacity is in good agreement with the experimental results,and the coefficient of variation is 0.1536.Based on the USFM model,a method for calculating the deformation of concrete shear walls with CFRP grids is established.Considering the deformation characteristics of the shear walls under the complex axial,flexural and shear stress,the deformation of the shear walls is divided into flexural shear deformation and slip deformation.The skeleton curve obtained by theoretical calculation is slightly larger than the experimental result,and the overall trend is in good agreement with the experimental result.Thus,the load-displacement curve of shear wall can be calculated more accurately.更多还原