混凝土T梁桥拓宽的长期效应分析

Long-term effect analysis of widening for concrete T-girder bridge

为了分析拓宽后桥梁的时间效应,研究了每一时段内由混凝土收缩引起的应力的连续变化和混凝土的弹性模量变化,根据能量原理推导了混凝土收缩徐变的位移法基本方程,按增量法分析了徐变应变的变化,编制了相应的计算程序。为验证理论计算的正确性,与小试件的试验结果作了比较。在拼接缝处的受拉区,应变计算值与实测值的相对误差为10%,计算精度比代数法高。在新梁混凝土的收缩应力和新梁自重应力的徐变作用下,3 a后新梁翼板的拉应力为2.67 MPa,可能会引起混凝土开裂。为减少收缩徐变对新旧梁受力的影响,建议新梁脱模后至少放置6个月后再进行拼接处理。

In order to analyze the long-term effect of widening for concrete T-girder bridge, the continuous change of stress resulted from the shrinkage and elastic modulus change of concrete in each period of time were studied, the basic formulas of shrinkage and creep were derived by using displacement method based on energy principle, the strain change of creep was analyzed by using incremental method, and corresponding calculation program was compiled. For testing the program, the calculation result of test pieces was compared with their measure result. Their relative error is 10% at the joint of new and old concretes, so the computation precision of the program is higher compared with algebraic method. The tensile stress at flange plate of new girder is 2.67 MPa under creep effect aroused by shrinkage stress and self-weight stress of new girder in 3 a, which may lead to concrete crack. For reducing the effect of shrinkage and creep, it is suggested that bridge should be widened after new girder is placed at least 6 months. 6 figs, 11 refs.