均匀及非均匀荷载作用下柱下梁板式筏基反力变形及破坏特征试验研究

Experiment Study on Contact Pressure Deformation and Failure Pattern of Slab and beam Foundation under Equal and Unequal Load on the Pillar

本次试验对高跨比1/6的梁、板厚跨比1/12的两组梁板式筏基模型进行加荷试验。试验表明,梁板基础呈现整体正向挠曲、内部区域反向挠曲特征。荷载通过柱传递至梁,再由梁传递到板,当柱下荷载均匀时,在地基承载力特征值内,地基反力非直线分布,梁下平均反力与柱下平均反力相差不大,约为总平均反力的1.1～1.15倍,板下平均反力小于总平均反力,板格中点处的地基反力约为总平均反力的55%,结构破坏时裂缝出现在板格上表面,裂缝贯通后呈对角线破坏形态;对于角部区域板块,角柱位置的地基反力与平均反力的比值约为1.2,其余部位地基反力均小于平均反力,区格板中心下的反力最小,约为角柱位置的地基反力的40%。结构破坏时梁中部顶面首先开裂,裂缝向下延伸至板边,由板边沿平行于梁的方向向板中心呈渐进式破坏,裂缝贯通后呈十字交叉破坏形态。

This test is a load test of two models with the beam whose ratio of thickness to span are 1 /6 and the slab whose ratio of thickness to span are 1 /12. According to this test,the beam and the slab deflects downward as a whole. The beam and the slab deflects upward locally in the inner area. The load is transmitted from column to beam,then to the slab. Within the characteristic value of subsoil bearing capacity,contact pressure under the foundation is not uniform under equal load on the column. The average contact pressure under beam and column are almost equal,around 1. 1 ～ 1. 15 times of the average contact pressure. The contact pressure under the center point of the slab is around 55% of the average contact pressure. The structure cracks first at the upper surface of the slab,extending diagonally. For the corner area of slab and beam foundation,the contact pressure under the corner column is 1. 2 times of the average contact pressure,while the other area is smaller than the average. The contact pressure under the center point is the smallest,around 40% of that of the corner column. The structure cracks first at middle of the upper surface of the beam,extending down to the edge of the slab. Gradually the crack extends to the center of the slab in parallel with the beam. At last,the crack pattern is like a cross on the upper surface.