双向筒芯简支预应力空心楼板静力试验

Static test of a simple support pre-stressed concrete hollow slab with two-way tube fillers

为研究筒芯内模顺筒向与剪力传递方向一致的四边简支现浇预应力混凝土双向空心楼板在竖向荷载作用下的性能,完成一块净跨为8m×8m的试验板的静力加载破坏试验。结果表明,试验板在板底中部出现弯曲裂缝,沿板的对角线方向发展并形成塑性铰线,板为弯曲破坏;实测开裂荷载大于规范计算值;加载至荷载标准值时,实测跨中最大竖向位移经考虑混凝土徐变影响后小于规范限值;加载至荷载设计值时,钢筋接近屈服;钢筋屈服时施加的荷载大于按弹性理论计算的荷载,预应力钢绞线接近条件屈服强度时施加的荷载大于按塑性理论计算的荷载;试验结束时,板中心的位移达到板跨的1/63,施加的荷载为荷载设计值的1.81倍;竖向位移、板内钢筋应变及截面抗弯刚度基本为中心对称即两个方向分别对于板的中线对称。在试验的基础上提出如下设计建议:沿剪力传递方向布置筒芯内模的四边简支双向空心楼板,内肋和组间肋可不配箍筋,可视为各向同性双向板,按弹性理论计算其受弯承载力,按塑性理论计算其极限弯矩,按双向板计算截面抗弯刚度。

To study the mechanical behavior of simply edge-supported cast-in-situ pre-stressed concrete two-way hollow slabs with tube fillers along the shear transfer directions,static test of a 8m×8m slab was performed under uniformly distributed vertical loads.The test results showed that the bending cracks appeared at the bottom of the slab,expanded along the diagonals and eventually formed plastic hinge lines,and the slab failed in bending.The measured crack load was larger than the calculation.Under the standard load,taking into account the influence of creep of concrete,the measured maximum vertical displacement was less than the code limit value.Under the design load,the reinforcement did not yield.As the pre-stressed strands approached the conditional yield strength,the applied load was larger than the load calculated from the plastic theory.In the end of the test,the maximum vertical displacement reached 1/63 of the span of the slab,the applied load was 1.81 times of the design value.The vertical displacement,the strain of reinforcement and the sectional bending stiffness were,respectively,basically centrally symmetric and symmetrical with respect to the center line of the slab in both directions.It is recommended that for simply edge-supported two-way hollow slabs with tube fillers along the shear transfer directions,stirrups are not necessary in the ribs,the slab can be considered as an isotropic two-way slab,its bending strength and ultimate strength can be calculated by using elastic theory and plastic theory,respectively,and its sectional bending stiffness can be calculated by two-way slab theory.