预应力混凝土桥梁收缩与徐变变形试验研究

EXPERIMENTAL RESEARCH ON THE DEFORMATIONS FOR SHRINKAGE AND CREEP OF BEAMS IN PRESTRESSED CONCRTE BRIDGES

由本试验配制成的低徐变普通高强混凝土(HSC,C50)和低徐变高性能混凝土(HPC,C50)及其制作成的8根计算长度为6m的预应力T形梁的收缩、徐变试验为基础,研究HSC梁与HPC梁的收缩、徐变和上拱随时间的变化,并研究梁体上下缘应力水平差、钢筋(预应力和非预应力)配筋率及环境对收缩、徐变及上拱变化的影响规律。500多天试验观测表明,在梁体上下缘应力水平相差较小时,目前规范中计算预应力混凝土桥梁徐变上拱的方法可能产生较大误差,本文提出的计算公式理论值与试验结果吻合得较好。文中建立了考虑配筋率影响的梁体混凝土徐变、收缩的计算式,提出了钢筋对徐变影响系数的计算方法。本文亦为有关工程设计及理论分析提供可靠的试验依据。

Based upon the test results of shrinkage and creep of eight prestressed concrete, with 6 meters long each, T-beams, which were constructed by specific compounded low creep common high strength concrete (HSC50) and low creep high performance concrete (HPC50) respectively for this experiment, then, the study of the time dependent shrinkage, creep and camber of HSC and HPC beams are presented, meanwhile, the research on the level differences between top and bottom fibers stresses of beams, the steel (prestressed and non-prestressed) reinforcemet ratios as well as the effective regularity of enviro-mental variations on shrinkage, creep and camber are carried out. Taking the experimental observations over 500 days, there are indications that if the differences between top and bottom fibers stresses are relatively on the small side, using the method specified in present code to compute the creep, camber of beams for prestressed concrete bridges, hence, a comparative large error may be produced possibly, nevertheless, the theorectical values of computing formulae in the paper are fitting well with experimental data. The computing formulae of shrinkage, creep of concrete beams in prestressed concrete bridges considering the effects of steel reinforcement ratios have been established in the paper and the computing methods for the effective coefficients of steels on creep are presented. In addition, the reliable experimental data which are useful to engineering design and theoretical analysis have been provided too.