考虑尺寸效应影响的钢筋混凝土构件纯扭承载力计算方法

Calculation for pure torsional capacity of reinforced concrete members considering size effect

近年来,钢筋混凝土构件的抗扭设计问题受到了广泛关注,现行的设计规范是基于小尺寸试件的试验数据外推而来,并未考虑尺寸效应的影响,对大尺寸试件承载力预测值的安全度有待商榷。对比分析国内外规范中RC构件纯扭承载力计算方法公式,基于钢筋混凝土柱纯扭加载三维细观数值模拟结果,总结钢筋混凝土柱名义抗扭强度尺寸效应规律,建立可定量反映配箍率影响的名义抗扭强度尺寸效应律公式;通过引入尺寸效应系数αh建立考虑结构尺寸效应影响的钢筋混凝土构件纯扭承载力建议预测公式,并将αh分为3个区域,综合考虑结构设计的安全性和经济性,从而保证大尺寸试件承载力预测值的安全度;通过与90个试验数据的对比,证明修正公式能有效提高大尺寸试件承载力预测值的安全储备。

The torsional structure design of RC members has been widely concerned in recent years.However,the existing design codes are extrapolated based on the test data of small size specimens without considering the impact of size effect,so the safety degree of the predicted values of large size specimens remains to be further discussed.In this paper,the calculation formulas of pure torsional bearing capacity at home and abroad were compared and analyzed.Based on the results of three-dimensional mesoscopic numerical simulation of pure torsional loading of reinforced concrete columns,the size effect law of nominal torsional strength of RC columns was summarized,and the size effect law formula of nominal torsional strength which can quantitatively reflect the effect of stirrup ratio was established.Furthermore,by introducing the size effect coefficient αh,a suggestion predicted formula for the pure torsional capacity of RC members considering the influence of size effect was proposed,and αh is divided into three regions,which comprehensively considers the safety and economy of structural design,so as to ensure the safety of the predicted values of large size specimens.By comparing the existing 90 test data,it was proved that the modified formula can effectively improve the safety reserve of the predicted bearing capacity of large size specimens.