叠合板中桁架钢筋对预制板受力性能的影响

采用混凝土叠合板可在保证结构受力性能的同时，有效地提高结构的装配率。受限于板的整体厚度和相关规范中对现浇层厚度的要求，预制层的厚度通常不能满足刚度需求。国内常采用在预制板中布置桁架钢筋的方法提高预制板刚度。然而目前却没有规范给出桁架钢筋预制板刚度的计算方法，此外，我国应用的桁架钢筋板厚度较薄，尺寸较小，刚度提升效果十分有限，采用桁架钢筋提升板的刚度可能并不经济。为此，通过跨中两点弯曲试验研究桁架钢筋对预制板受力性能的影响，并基于试验结果和理论分析，提出了预制板刚度计算方法。试验结果表明：桁架钢筋对预制板刚度的提升有限，60 mm厚桁架钢筋板的刚度可能无法满足施工要求；桁架钢筋对混凝土板有效受压面积的削弱将导致混凝土板受弯承载力明显降低，上弦钢筋的屈曲将导致预制板达到极限状态后承载力迅速下降。基于试验结果的参数分析显示，取消桁架钢筋，适当增加预制板厚度，不仅能有效提升预制板的刚度和承载力，还能降低楼板钢筋用量达26%左右。

Effect of truss reinforcement on mechanical properties of prefabricated slabs

Partially prefabricated concrete slabs can effectively improve the assembly rate of the structure while guaranteeing the mechanical properties. Due to the regulations of the cast-in-place layer in the relevant specifications, the precast layer is usually too thin to meet the rigidity requirements. Truss reinforcement is often used in the precast slab to improve the rigidity in China. However, there is no specification providing a calculation method for stiffness of precast slab with truss reinforcement. In addition, the truss slabs used in China have a relatively small size, which limits the effect of stiffness improvement. It may not be economical to use truss slabs. In this research, mid-span two-point bending tests were carried out to study the effect of truss reinforcement on the mechanical properties of precast slabs. Based on the experimental results and theoretical analysis, a method for calculating the stiffness of truss slab was proposed. The experimental results show that the improvement of stiffness of the precast slab by the truss reinforcement is limited, and the stiffness of the 60 mm-thick slab may not meet the construction requirements. In addition, the truss reinforcement can weaken the effective compression area of the precast slab, resulting in a decrease of the bearing capacity of the precast slab. The buckling of the top chord will cause the bearing capacity of the precast slab to decrease rapidly after reaching the limit state. The parametric analysis based on the test results shows that eliminating the truss reinforcement and appropriately increasing the thickness of the prefabricated slab can not only effectively improve the stiffness and bearing capacity of the prefabricated slab, but also reduce the amount of reinforcing steel on the floor by about 26%.