考虑扭矩影响的四边简支矩形板内力分析及配筋修正

混凝土四边简支矩形板一般是基于弹性薄板小挠度理论求出跨中弯矩布置板底钢筋,支座设置构造钢筋.该文基于弹性薄板小挠度理论,求解了板内扭矩分布.由分析可知,四边简支矩形板内具有复杂的扭矩分布,特别在角部部位其扭矩值将接近板的跨中正弯矩,由扭矩合成的主弯矩将使板角开裂.按照现行规范,仅在四边简支矩形板支座设置构造配筋是不合理的,无法满足抗扭需要,必须在角部配置受力钢筋.通过对比四边简支板与固支板沿对角线方向主弯矩的差异,指出边梁约束对板角混凝土开裂的缓解作用;该文揭示了目前混凝土简支楼板设计存在的不足,并对双向板、单向板合理设计提出了不同建议.

INTERNAL FORCE ANALYSIS AND REINFORCEMENT MODIFICATION ON THE RECTANGULAR SLABS WITH FOUR SIMPLY SUPPORTED SIDES BY CONSIDERING THE TORQUE EFFECT

The layout of steel reinforcement in the mid-span and the support of the rectangular concrete slab with four simply supported sides are usually based on the elastic thin plate theory for small deformation. This paper studies the distribution of torsion moment in the slab based on the same theory. The results show that the distribution of the torsion moment in the slab is quite complex. The magnitude of the torsion moment at the corner of the slab is close to the sagging moment in the mid-span. The combined moment consequently tears up the corner of the slab. The current design code for the simply supported rectangular slab only considers the constitutional reinforcement. Therefore, it does not satisfy the requirement for baring the torque at the corner of the plate and the reinforcement should be provided at the corner. From the comparison of the moment distribution along the diagonal line in simply supported rectangular plate and the fixed-end plate, this work demonstrates that the restraint of a curb beam for the plate can help relieve the cracking of concrete at the corner of the plate. The insufficiency of the current code in the design of simply supported floor slab is pointed out, and the corresponding recommendations in the design of one-way and two-way slabs are also proposed in this paper.