基于Abaqus的预应力混凝土T梁全过程剪力滞效应

Full-range Shear Lag Effect of PC T-beam Based on Abaqus

预应力混凝土T梁桥设计中需要考虑剪力滞效应,而预应力轴压作用和材料非线性对剪力滞效应的影响目前仍有待研究,采用非线性有限元程序对预应力混凝土T梁进行全过程分析不失为一种较精确的方法。考虑混凝土和钢筋的材料非线性,采用降温法模拟预应力,利用Abaqus软件建立了不同翼缘宽度的预应力混凝土T梁有限元模型,对T梁在恒载、集中荷载和均布荷载下加载至破坏的全过程受力性能和剪力滞效应进行了分析。结果表明:T梁在集中荷载和均布荷载下均达到承载能力极限状态;在线弹性受力阶段,T梁在恒载和均布荷载下的剪力滞效应不明显,在集中荷载下T梁跨中加载点附近区域内呈正剪力滞;进入非线性受力阶段后,受沿梁长内力重分布和截面上应力重分布的影响,T梁加载全过程的剪力滞效应区别于其线弹性状态,均布荷载下,全过程剪力滞系数较线弹性值变化较小,集中荷载下,全过程剪力滞系数相对于线弹性值的最大增幅为12%~15%;集中荷载下,T梁跨中截面的最大剪力滞效应发生于其纵向普通钢筋受拉屈服对应荷载;临近破坏时,随着沿梁长不同位置的纵向钢筋相继屈服,T梁剪力滞效应呈沿梁长正、负剪力滞交替分布状态。

The shear lag effect needs to be considered in the design of PC T-beam bridges.However,the influences of prestressed axial compression and material nonlinearity on shear lag effect still needs to be studied,and using nonlinear finite element program to conduct full-range analysis on PC T-beams is a relatively precise way.Considering the material nonlinearities of concrete and reinforcement and using the cooling method to simulate prestress,a finite element model of PC T-beams with different flange widths is established by using Abaqus software,the full-range mechanical performance and shear lag effect of the T-beams from loading to failure under dead load,concentrated load and uniformly distributed load are analyzed.The result shows that(1)T-beams reach the ultimate limit state under concentrated or uniform load.(2)In the linear elastic loading stage,the shear lag effect of the T-beam under dead load or uniformly distributed load is not significant,while it exhibits positive shear lag in the area near the mid-span loading point under concentrated load.(3)In the nonlinear stress stage,the full-range shear lag effect of the Tbeams are different from the linear elastic state due to the redistribution of the internal forces along the beam length and the stress redistribution on the section.Under uniformly distributed load,the full-range shear lag coefficient changes less than the linear elastic value.Under concentrated load,the maximum increase in fullrange shear lag coefficient relative to the linear elastic value is 12%-15%.(4)Under concentrated load,the maximum shear lag effect of the mid-span section of the T-beams occurred when the longitudinal reinforcement is subjected to tensile yield corresponding to the load.(5)When the failure approaches,with the longitudinal reinforcement yielding along the beam length continuously,the positive and negative shear lags are alternately distributed along the T-beam length.