【作者】 王德斌；

【导师】 李宏男；

【作者基本信息】 大连理工大学 ， 结构工程， 2013， 博士

【摘要】 钢筋混凝土结构在地震作用下的动力响应通常会受到荷载速率的影响,而钢筋混凝土柱作为主要的承重构件,其在不同加载速率下的抗震性能研究尚且较少,同时,目前的结构抗震设计规范并未涉及由荷载速率引起的钢筋混凝土构件力学性能和变形性能变化方面的条款。本文基于试验研究和数值计算相结合的方法,分析了地震荷载速率作用下钢筋混凝土柱的率敏感性对其力学特性的影响,主要内容归结如下：(1)试验研究了加载速率对钢筋混凝土柱力学性能和变形性能的影响。主要考虑的因素有：剪跨比、轴压比、混凝土强度、纵筋强度等级、纵向配筋率、体积配箍率、加载模式(单向加载、双向加载和变轴力加载)和加载速率。试验结果表明,随着加载速率的提高,构件的屈服承载力和极限承载力均有所增加,且屈服承载力增加的程度更为显著；加载速率的提高导致构件的强度退化、刚度退化和损伤加剧,延性略有降低,耗能则有所增加；轴力变化加剧了构件的率敏感性,使构件在加载后期提前失稳；双向加载过程中存在的耦联作用则进一步加剧了柱强度退化和刚度退化的进程。另外,基于理论分析发现,在快速加载条件下柱的截面受压区高度略有减小,加载速率导致柱的抗弯承载力的增长水平远高于抗剪承载力,同时,加载速率的提高致使构件的破坏机理也发生明显改变。(2)试验研究了钢筋混凝土柱在不同加载路径下的动力特性,主要考虑的加载路径有：单向循环加载、十字形加载、菱形加载和圆形加载路径。试验结果表明,加载路径和加载速率的综合作用使柱的强度退化、刚度退化、延性降低程度均明显提高；通过双向加载条件下的等效阻尼比计算结果,可以看到,圆形加载路径下柱的耗能能力最强;加载速率使柱的荷载-位移骨架曲线在加载后期斜率下降更为迅速,这种现象在菱形加载路径下表现更为显著；经过回归分析给出了不同加载路径下静力和动力加载的等效阻尼比计算的经验公式。(3)基于OpenSees中的分布塑性铰模型,数值计算给出了不同材料应变率下柱单调加载条件下的荷载-位移关系曲线和地震作用下柱的动力响应,并通过回归分析给出了不同材料应变率下柱极限承载力的动力增长因子经验公式。另外,基于OpenSees中的BeamwithHingesElement单元,引入钢筋和混凝土材料的应变率效应,考虑了构件的双向弯曲、轴力的耦联作用及剪切、粘结滑移效应,编制了钢筋混凝土柱的Tcl程序,对不同加载路径下的钢筋混凝土柱进行了数值模拟,并与试验结果进行了对比。更多还原

【Abstract】 As the main bearing component of RC structure, the seismic behavior of reinforced concrete column will be influenced by loading rate. However, there are very few studies on the dynamic properties of the RC members subjected to earthquake loading, and the current seismic design code for buildings hasn’t considered the effect of loading rate on the RC members. In this paper, the effects of loading rate on the RC columns are investigated by using the methods of experimental research and numerical calculation. The main sections of the research work are listed as follows:(1) The effects of loading rate on the dynamic properties of RC columns are experimentally studied with different parameters, including shear span ratio, axial compression ratio, concrete strength, steel strength, longitudinal steel ratio, volume-stirrup ratio, loading mode (uniaxial loading, biaxial loading and variable axial force) and loading rate. The test results show that as the loading rate increases, the yield load and ultimate load increase, and the growth of yield load is higher; the strength degradation, stiffness degradation and damage are faster; the ductility of RC columns decreases; the energy absorption increases slightly. The variable axial force enhances the sensitivity of loading rate of RC columns, and leads to buckling in advance, At the same time, the coupling behavior of the biaxial loading worsens both stiffness and strength degradation. In addition, based on theoretical analysis, as the loading increases, the relative depth of compression zone of RC columns decreases; the growth on the flexural bearing capacity of RC column is far higher than that of the shear bearing capacity; and the failure mechanism has also changed.(2) The effects of loading pattern (uniaxial cyclic loading, cross loading path, rhombus loading path and circular loading path) on the dynamic properties of RC columns are studied experimentally. The test results show that the combination of loading path and loading rate leads to enhancement of strength degradation, stiffness strength and the decrease level of ductility. Based on the calculation of equivalent damping, it is observed that the strongest energy dissipation occurs in the circular loading path. As the loading rate increases, the slope of skeleton curve decreases more quickly in the later stage of loading, especially in the rhombus loading path. Moreover, the empirical formulas of equivalent damping under static and dynamic loading are proposed by regression analysis of test results. (3) Based on the force-based beam-column element with distributed plasticity in OpenSees, the loading processes under monotonic and earthquake loading are simulated with different strain rate of materials, and the empirical formulas of ultimate bearing capacity are proposed according to the simulation results. Furthermore, in order to simulate the dynamic properties of RC column subjected to earthquake loading, based on the Beam with Hinges Element in OpenSees, considering the influence of different factors (strain rate effects of materials, the interaction between biaxial bending and axial force, the shear effect, the bond-slip effect), a Tcl program is compiled, and the dynamic behavior of RC columns under different loading paths are simulated. The results show that the Tcl program can simulate the hysteretic behavior of RC columns well.更多还原