配筋混凝土箱梁长期受力性能的比拟杆分析

为使配筋混凝土箱梁长期受力性能的分析趋于简便,将线弹性匀质箱梁短期弯曲性能分析的比拟杆法推广应用于其长期受力性能的分析。引入按龄期调整的有效弹性模量来考虑箱梁混凝土徐变的影响,基于换算截面的原理来考虑箱梁配筋的影响,建立能综合考虑箱梁受力特征和配筋影响的混凝土箱梁长期受力性能分析的比拟杆法。对一根预应力混凝土模型箱梁进行长达1001d的徐变试验,并用其结果对所提方法的适用性进行验证。结果表明:混凝土箱梁长期受力性能的比拟杆法计算结果与试验结果之间吻合较好。与试验值相比,t0～1001d时段内箱梁顶板混凝土压应变的计算值相差7%～11%、跨中截面长期挠曲变形的计算结果相差9%～17%。随着持荷时间的增长,箱梁顶板的剪力滞系数逐渐减小,持荷1001d后剪力滞系数减小了7.1%。

Bar Simulation Method for Analysis on Long-term Behavior of Reinforced Concrete Box Girder

In order to develop a simple method to determine the long-term behavior of the reinforced concrete box girder structure with the shear lag effect of box girder involved,a new bar simulation method was presented in which the Age-adjusted Effective Modulus was used to consider the effects of concrete creep and the principle of transformed section was used to consider the effects of reinforcement.The results of the method were testified by the long-term performance test of a prestressed concrete simply-supported box girder under sustained loading of 1001d.The results show as follows:The developed method can give a reasonable prediction to the creep reponse of the concrete box girder;compared with the measured values,the predicted compressive strain in the top plate and the long-term deflection at the mid-span of the tested box girder is of error range of(7~11)% and(9~17)% respectively;the shear lag coefficient of the top plate of the box girder reduces gradually in extension of the sustained loading period and till by 7.1% after 1001d.