Evaluation of Ductility of Rinforced Concrete Structures

1.基于小尺寸悬臂式试件的静力循环加载试验，建立了钢筋混凝土构件延性的计算公式。这些公式中包含的值有主配筋率、腹筋率、剪跨比、轴压应力、混凝土抗压强度、粗骨料最大尺寸、重复加载次数。在这些方程中，通过计算中性轴以下的配筋量作为主要配筋量，考虑了沿侧向布置的钢筋对延性的影响。通过延性计算值与实验值的比较，结果令人满意，计算值与实验值的平均比值为1.09，变异系数为14.5%。随着加载速率的增加，恢复力的最大值增大，但在下降支处的恢复力减小得更快。由此推测，加载速率对延性有一定的影响。然而，由于缺乏足够的数据，这种影响不能包含在上述方程中。在考虑了文献[1]结果的基础上，提出了考虑延性的恢复力模型。通过对两层刚架的反应分析与振动台试验结果的对比，证明该模型能够较好地跟踪框架的行为直至极限状态。因此，利用该模型对钢筋混凝土结构进行反应分析，可以对其延性进行评估。

1. A series of equations to evaluate the ductility of reinforced concrete members were derived based on static cyclic loading tests on small scale specimens of a cantilever type. Valuables contained in these equations are main reinforcement ratio, web reinforcement ratio, shear span ratio, axial compressive stress, compressive strength of concrete, maximum size of coarse aggregate, number of repetition of loading. In these equations, the influence of the reinforcements arranged along side faces on the ductility is taken into consideration by counting the amount arranged below the neutral axis as main reinforcement. It was proved by the comparison of calculated ductilities with the experimental ones that the derived equations give satisfactorily accurate results, the average of the ratio of calculated value to the experimental one being 1.09 and the coefficient of variation being 14.5%.2. As the loading rate is increased, the maximum value of restoring force increases, but at the same time, it decreases more rapidly on the descending branch. It is supposed from this fact that the loading rate has some influence on the ductility. However, this influence could not be contained in the equations described above because of lack of sufficient data.3. A restoring force model was proposed, taking the ductility based on the result described in 1 into account. It was proved by comparison of the response analysis on the 2 stories rigid frames with the results of shaking table tests that the model can trace the behavior of the frames upto the ultimate state satisfactorily. Therefore, it can be concluded that the evaluation of ductility of reinforced concrete structures is possible when response analysis is carried out using the proposed model.