大跨度变厚度钢筋混凝土中空板设计

Design of long span RC variable thickness hollow slab

为使自重较重的钢筋混凝土材料能够在大跨度楼盖中得到合理应用,对变厚度中空板进行分析研究。变厚度板是指将板带的截面由矩形转变为T形,且薄板与厚板高度之比满足h′/h≥0.45,当T形板带跨中截面达到承载能力极限状态时,厚板和薄板的受压区高度相等,其纵向受拉钢筋均能达到抗拉设计强度。支座截面达到承载能力极限状态时,薄板的上下钢筋也均能达到抗拉设计强度,充分发挥了薄板中钢筋的作用。同时给出了变厚度板的强度、冲切、裂缝宽度及挠度的计算方法,并将研究成果应用于工程实践,在满足规范要求的同时,相对于梁板体系,减小了结构高度,相对于无梁楼盖体系,减少了材料用量,取得较好的经济性,可供设计大跨度楼盖时参考。

In order to make rational use of the heavy concrete material in long-span slab,this paper deals studies the variable thickness hollow slab.The variable thickness slab is the thick slab with a rectangle section changing into T form,but the thickness ratio of thin and thick slabs must maintain h′/h≥0.45.When the T form slab reaches to the limit of load carrying capacity of its middle section,the height of the thick slab in the load area is same to that of the thin slab,with all the steel tensile stress reaching the design value of yield strength.When the T form slab reaches the limit of load carrying capacity of its support section,all the steel in tension can also reach the design value of yield strength.Accordingly the action of steel in the thin slab is effectively developed.The paper also discusses a computational methods on strength,punching shear,crack width and deflection of variable thickness slab and the results can be used in practical design.The research can serve as the reference in planning of long-span slab,for reducing the height of structure,which can achieve better economical efficiency compared with the system of slab without beam.