Evaluation of Ductility of Rinforced Concrete Structures

1.根据悬臂式小比例试件的静力反复加载试验，推导了钢筋混凝土构件延性的计算公式。这些公式中包含的参数有主筋配筋率、腹筋配筋率、剪跨比、轴压应力、混凝土抗压强度、粗骨料最大粒径、荷载重复次数等。在这些方程中，通过将布置在中性轴下方的数量作为主钢筋来计算，考虑了沿沿着侧面布置的钢筋对延性的影响。计算结果与实验结果的比较表明，所推导的公式具有令人满意的精度，计算值与实验值之比的平均值为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，但下降分支上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。在文献[1]的基础上，考虑延性，提出了恢复力模型。对两层刚架结构的反应分析与振动台试验结果的比较表明，该模型能较好地反映结构的受力性能，直至结构的极限状态。因此，可以得出结论，钢筋混凝土结构的延性评估时，使用所提出的模型进行响应分析是可能的。

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.