基于纤维模型的钢筋混凝土柱应变率效应研究

STUDY ON THE BEHAVIOR OF REINFORCED CONCRETE COLUMNS WITH FIBER MODEL CONSIDERING STRAIN RATE EFFECT

该文基于钢筋混凝土柱构件的快速加载试验数据,分别采用CEB规范和Kulkarni和Shah建议的考虑应变率效应的混凝土动力本构关系,运用纤维模型建立了其动力纤维单元模型,并对单调快速加载下的构件的恢复力特性进行了数值模拟。与试验结果的比较表明所采用的两种动力本构模型均能够反映钢筋混凝土柱承载力随加载速率的提高而提高的特性,纤维模型提供了一种简便计算不同单调加载速率下混凝土柱的承载力的方法,验证了所建立的模型的有效性。基于此模型,对其中不同轴压比的两个试件在不同加载速率下的单调动力性能进行了数值模拟,分析加载速率对试样的动力承载力的影响。尽管两种动力本构模型在较低应变率水平下能够给出与试验结果吻合较好的结果,但随着应变率水平的提高,采用CEB规范以及Kulkarni与Shah建议的动力本构模型所得到的混凝土柱的承载力呈现一定的差异,欧洲规范CEB给出的结果要大。

In this study,dynamic tests on reincorced concrete（RC） column specimens subjected to high rate loadings are carried out.Two dynamic constitutive models of concrete proposed by CEB code and Kulkarni and Shah with the consideration of strain rate effects are adopted for the fiber model of RC columns,and a dynamic fiber model for the specimens is constructed and employed to study the dynamic performance of the RC column specimens.Simulation results by the two constitutive models show good agreements with the test results.The results also show that lateral load capacity of the RC columns increase with loading rate,and the proposed dynamic fiber element model provides a convenient way to predict the behavior of RC columns under the considered loading rates.The validated dynamic fiber element model is employed for further numerical study of the dynamic monotonic properties of two of the considered RC columns under different axial compression ratios and subjedted to different loading rates.Results show that dynamic load-carrying-capacity of the specimens increase with the increase of the loading rates.Moreover,the employed two dynamic constitutive laws give close load-carrying-capacity results under low loading rates with corresponding strain rates lower than about 10？4/s,but differences exist under relatively higher strain rates.The load-carrying-capacity by CEB code is relatively higher.