配500MPa钢筋后张有粘结预应力混凝土梁受弯试验

目的研究采用500 MPa钢筋作为纵向受拉非预应力筋的后张有粘结预应力混凝土梁的受弯性能,了解其受弯破坏形态、受弯承载力、裂缝分布及变形等情况,为工程中推广应用500 MPa钢筋提供试验依据.方法采用两点对称集中的同步分级反位加载方式,对8根试验梁进行静力加载试验.结果开裂弯矩实测值与计算值比值的均值为1.094.考虑纵向受压非预应力筋参与受弯作用时,受弯承载力实测值与计算值比值的均值为1.032.正常使用状态下短期挠度和曲率实测值与各自计算值比值的均值分别为1.055和0.988.结论试验梁达到受弯极限状态时,尽管钢绞线配筋率较高而未屈服,但500 MPa钢筋可屈服,且梁的破坏仍具有一定延性.根据平截面假定和应变协调条件计算的受弯承载力与实测值符合较好.可按现行《混凝土结构设计规范》公式计算试验梁的变形.

Flexural Test of Post-Tensioned Bonded Prestressed Concrete Beams with 500 Mpa Steel Bars

Eight post-tensioned bonded prestressed concrete beams with 500 MPa tensile non-prestressing steel bars were tested under two-point symmetrical concentrated static loading to investigate their flexural behavior. The failure mode, flexural strength, crack distribution as well as deformation of the beams were analyzed. The results show that the mean ratio of test values to calculating ones of cracking moment is 1. 094. When the compressive reinforcements are considered, the mean ratio of test values to calculating ones of flexural strength is 1. 032. The mean ratio of test values to calculating ones of short-term deflection and curvature under service loading is 1. 055 and 0. 988 respectively. When the beams reach their ultimate limit state, although the prestressing strands do not yield due to high strands ratio, the 500 MPa steel bars can yield, resulting in certain degree of ductility of the beams. The flexural strength calculated on the basis of the plane section assumption and strain compatibility condition agrees well with the test results. The flexural stiffness formula in the existing Code for Design of Concrete Structures is shown to be suitable for calculating the deformation of the beams. The test results can serve as experimental basis for the application of 500 MPa steel bars in the engineering.