钢筋混凝土柱纯扭破坏尺寸效应数值分析

在地震作用下，钢筋混凝土柱时常会受到扭矩的作用，而扭矩的存在会改变钢筋混凝土柱的破坏模式。为探究钢筋混凝土柱纯扭破坏的尺寸效应行为，采用三维细观数值模拟方法，考虑了混凝土细观组分的非均质性及钢筋与混凝土间的粘结滑移作用，建立了钢筋混凝土柱的纯扭作用数值模型。模拟分析了结构尺寸、纵筋率、配箍率和截面形状对钢筋混凝土柱抗扭破坏的影响。结果表明:钢筋混凝土柱扭转破坏表现为脆性特征，名义抗扭强度表现出明显的尺寸效应；纵向配筋对扭转强度尺寸效应影响不大；方形截面柱比圆形截面柱具有更强的尺寸效应；箍筋可以提高扭转强度，且可以削弱名义抗扭强度的尺寸效应。最后，修正了Ba?ant尺寸效应律，建立了全结构尺寸范围内的名义抗扭强度预测公式。

SIZE EFFECT NUMERICAL ANALYSIS ON PURE TORSIONAL FAILURE OF RC COLUMNS

Under the action of earthquake, the reinforced concrete (RC) columns may subject to torsional moment, and the existence of torsion will change the failure mode of RC columns. In order to study the size effect of RC columns on pure torsional failure, a numerical model of RC columns on pure torsional failure was established by using the three-dimensional meso-scale numerical simulation method, considering the meso-heterogeneity of concrete and the bond-slip action between reinforcements and concrete. The influence of structural size, longitudinal reinforcement ratio, stirrup ratio and cross-sectional shape on torsional failure of RC columns was investigated. The results show that: the tested RC columns show brittle failure patterns, the nominal torsional strength presents obvious size effect; the longitudinal reinforcement presents little influence on the size effect; columns with square cross-section present stronger size effect than the ones with circular shape; stirrups can improve the torsional strength, while they would weaken the size effect on torsional strength. Finally, a prediction formula for nominal torsional strength in the full-size range was established by modifying Ba?ant’s size effect law.