与构件尺寸相关的方形箍筋约束混凝土轴压强度解析模型

Axial compressive strength analytical model of square stirrups confined concrete that related to specimen size

为深入研究素混凝土及约束混凝土轴心抗压强度的尺寸效应问题,基于内部屈曲理论构建了素混凝土棱柱体轴压破坏的三维失效模型。在此基础上,利用侧向压应力能提高平面内受压简支薄板临界失稳应力的原理,诠释了箍筋约束对混凝土峰值强度的提高作用,并推导出方形箍筋约束混凝土棱柱体峰值强度的解析解,该解析解考虑了箍筋对混凝土约束不均匀的特性。之后结合试验数据,对所得解析解中的未知参数进行了数值逼近求解。最后,将模型预测值与试验值进行比较,发现解析模型能在一定程度上反映箍筋约束混凝土抗压强度随构件尺寸增大而减小的现象,但却高估了试件尺寸对峰值强度的调节能力。

In order to intensively study the size effect of axial compressive strength of plain concrete and confined concrete, in this thesis,the three dimensional failure model of axial compressive failure of plain concrete prism is established based on internal buckling theory.On this basis, the theory that lateral compressive stress can improve the critical instability stress of compressive supported plate in plane is used to explain that stirrupconfinement improves concrete ultimate strength.Also, the analytical solution of ultimatestrength of square confined concrete prism is derived,which considers the characteristic that the stirrups＇ constraint on concrete is not uniform.Afterwards,combined the test data, in this thesis,numerical approximation is used to calculate the unknown parameters of the said analytic solution.Lastly,when the predicted value is coMPared with the test data, it is found that the analytic model shows to some extent that when the size increases, the compressive strength of stirrup confined concrete decreases.However, it overestimates the adjustment ability of specimen size on peak strength.