考虑结构空间约束的现浇楼盖梁跨中受弯性能试验

为研究结构空间约束导致现浇钢筋混凝土楼盖梁跨中受弯承载力超强的机制,以楼盖梁在结构中的空间位置和配筋率为变量,设计12根上部架立筋不伸入支座的楼盖梁试件并开展跨中受弯静力试验,并基于建立经典混凝土理论的试验方法进行了4根简支梁对比试验。对梁试件破坏形态、承载力、变形能力、轴向伸长进行研究,结果表明:楼盖梁试件承载力与按受弯构件计算承载力之比为1.57~2.77,与相应矩形简支梁试件和T形简支梁试件承载力相比均有较大提高,超强程度与配筋率成反比；与简支梁试件相比,楼盖梁试件跨中截面破坏形态未因轴压力而发生显著改变,但楼盖梁试件延性降低；楼盖梁试件轴向伸长随挠度的增大而增大。将楼盖梁视为压弯构件,提出根据楼盖梁试验峰值荷载确定相应轴力和弯矩的方法。计算结果表明,楼盖梁试件跨中截面压弯状态弯矩与受弯状态弯矩的比值为1.28~2.19。楼盖梁试件有限元数值模拟结果表明,随着楼盖梁截面包含的楼板范围增大,轴力沿梁跨分布趋于均匀。

Experimental study on mid-span flexural performance of floor beams incorporating structural spatial restraints

To investigate the mechanism of flexural overstrength of cast-in-situ reinforced concrete floor beams incorporating structural spatial restraints, this article takes the spatial position and longitudinal reinforcement ratio of the floor beams in the structure as variables, designs 12 floor beam specimens with upper erection bar not extending into the support, and conducts static tests on the mid-span flexural performance. Based on the experimental method of establishing classical concrete theory, a comparative test of 4 simply supported beams is conducted. The failure mode, bearing capacity, deformation capacity and axial elongation of beam specimens are studied in this article. The results show that the ratio of the bearing capacity of the floor beam specimen to the calculated bearing capacity based on flexural components is 1.57-2.77, which is significantly improved compared to the corresponding rectangular and T-shaped simply supported beam specimens. The degree of overstrength is inversely proportional to the longitudinal reinforcement ratio. Compared with the simply supported beam, the failure mode of the mid-span section of the floor beams do not change significantly due to the axial compression, but the ductility of the floor beam decrease. The axial elongation increases with the increase of the deflection. Regarding the floor beams as compression-flexure components, a method is proposed to determine the corresponding axial force and flexural moment according to the test peak load of the floor beam. The calculation results show that the ratio of the moment of the mid-span section of the floor beams subjected to compression and flexure to the moment subjected to flexure is 1.28 to 2.19. The finite element numerical simulation of the floor beam is carried out in this article. The results show that with the increase of the included floor range of the floor beam section, the axial force tends to be uniform along the beam span.