端钩型钢纤维混凝土简支梁受弯承载力试验

Experiment on Flexural Bearing Capacity of Hooked-end Steel Fiber Reinforced Concrete Simply-supported Beam

为改善普通钢筋混凝土梁自重大、易开裂、承载力低等缺点,在混凝土中常加入钢纤维,端钩型钢纤维,作为常见的一种高性能钢纤维得到广泛关注,中外学者针对端钩型钢纤维混凝土的基本力学性能开展了较多研究,而对端钩型钢纤维混凝土受弯构件的正截面受力性能有待深入研究。为研究端钩型钢纤维混凝土简支梁受弯性能,制作4根端钩型钢纤维混凝土梁及1根普通混凝土梁,对其进行受弯性能试验,根据试验得到的破坏形态、承载力、荷载-挠度曲线、荷载-应变曲线,分析端钩型钢纤维体积掺量对试件受弯承载力及破坏形态的影响。结果表明:端钩型钢纤维混凝土简支梁与一般混凝土简支梁受弯过程类似,均经历了弹性、开裂、带裂缝工作、破坏4个阶段;端钩型钢纤维混凝土简支梁与一般混凝土简支梁受弯过程均基本符合“平截面假定”;端钩型钢纤维限制了裂缝的产生和发展,使得纤维混凝土梁变形能力增强;与一般混凝土梁相比,端钩型钢纤维混凝土梁抗裂性及极限承载力得到提高,且构件承载力与钢纤维体积掺量基本呈现正相关;基于试验数据,对现行规范中开裂弯矩及极限承载力计算公式进行优化,开裂弯矩方面考虑对截面抵抗矩塑性影响系数进行修正,极限承载力方面引入纤维混凝土正截面承载力影响系数ζ,经修正计算值可较好吻合试验值。

In order to improve the disadvantages of ordinary reinforced concrete beams,such as large deadweight,easy cracking and low bearing capacity,steel fiber is often added to concrete.As a common high-performance steel fiber,hooked-end steel fiber was widely concerned.Scholars at home and abroad carry out a lot of research on the basic mechanical properties of hooked-end steel fiber reinforced concrete,but the bending members of hooked-end steel fiber reinforced concrete needs further study.In order to study the flexural behavior of hooked-end steel fiber concrete simply-supported beam,four hooked-end steel fiber reinforced concrete beams and one reinforced concrete beam were made,and their flexural behavior tests were carried out.According to the failure form,bearing capacity,load-deflection curve and load-strain curve were obtained from the tests,the influence of the volume content of the hooked-end steel fiber on the flexural bearing capacity and failure form of the specimen was analyzed.The results show that the bending process of hooked-end steel fiber reinforced concrete simply-supported beams is similar to that of ordinary concrete beams,and they have experienced four stages:elasticity,cracking,working with cracks,and failure.The bending process of hooked-end steel fiber reinforced concrete simply-supported beams and ordinary concrete simply-supported beams basically conforms to the“plane section assumption”.Hooked-end steel fiber restricts the generation and development of cracks,and enhances the deformation ability of steel fiber reinforced concrete beams.Compared with ordinary concrete beams,the crack resistance and ultimate bearing capacity of hooked-end steel fiber reinforced concrete beams are improved,and the bearing capacity of members is basically positively correlated with the volume content of steel fiber.Based on the test data,the calculation formula of cracking moment and ultimate bearing capacity in the current code is optimized.In the aspect of cracking moment,it is considered to modify the plastic influence coefficient of section resistance moment,and in the aspect of ultimate bearing capacity,the influence coefficient of normal section bearing capacity of fiber reinforced concrete is introducedζ.The corrected calculated value can be in good agreement with the test value.