考虑收缩、徐变及开裂影响的组合梁长期受力性能研究(Ⅰ)——试验及计算

Long-term behavior of composite beams with shrinkage,creep and cracking(I):experiment and calculation

通过4根钢-混凝土组合梁的长期荷载试验,研究混凝土收缩、徐变和开裂对组合梁长期受力性能的影响,并重点讨论变形随时间的变化规律。试验表明,收缩、徐变对组合梁的受力性能有显著影响:对于承受正弯矩作用的组合梁,其1年期的变形可达到初始瞬时弹性变形的2.5倍;对于承受负弯矩的组合梁,收缩及荷载作用会导致混凝土开裂并减少徐变效应的影响。通过有效模量法计算结果与实测值的对比分析,表明现行规范方法可较好计算试验梁的瞬时挠度和正弯矩作用下的长期挠度,对于承受负弯矩作用的组合梁则需要考虑混凝土开裂对其长期变形的影响。

A long-term experimental study on four composite steel and concrete beams under sustained load conditions is presented. The test program consists of two simply-supported beams under positive bending moment and two cantilever beams under negative bending moment. Deflections and strains are monitored over a period of 500 days. It is shown that the creep and shrinkage of concrete significantly affect the characteristics of the composite beams. For beams under positive bending, the mid-span deflections after one year of loading are 2.5 times of the instantaneous deflection. For beams under negative bending, the shrinkage and sustained loading causes cracking of the concrete and reduces the creep effect. A predictive model for long-term deflection based on the design code is calibrated with the tests, and design recommendations are provided.