预应力混凝土钢桁架叠合板受弯性能试验与理论研究

通过在预应力混凝土平板上增设钢桁架方式，提出一种预应力混凝土钢桁架叠合板，解决了现阶段其他类型叠合板用预制底板存在开裂荷载较低、临时支撑密集等问题。为研究不同桁架类型对预制底板及叠合板受弯性能的影响，对6块预制底板试件和4块叠合板试件开展了静力加载试验，得到其破坏特征、开裂荷载、挠度曲线及应变分布等。试验结果表明：钢桁架能够显著提高底板的开裂荷载，其中钢管桁架底板试件的开裂荷载最高，达到平板试件的194%以上，适用跨度最大达到9m；不同桁架类型底板试件的破坏模式存在一定差异，钢板桁架、钢管桁架和钢筋桁架预制底板的破坏特征分别为钢板屈曲、焊缝断裂及钢筋弯曲；钢桁架能显著增强底板及叠合层混凝土的整体受力及协同工作性能；桁架类型对叠合板的受弯性能影响较小，不同桁架类型叠合板的开裂荷载均相同，开裂挠度差异在10%以内。基于试验结果，建立了底板上弦失稳弯矩计算公式，并提出预制底板失效弯矩应取开裂弯矩与上弦失稳弯矩的较小值，计算值与试验值吻合较好。

Experimental and theoretical study on bending behavior of prestressed concrete composite slabs with steel trusses

A composite slab was developed which added steel trusses above the prestressed concrete panels to slove the problems of the current precast panels with low cracking loads and serried supports. Ten specimens, including six precast panels and four composite slabs, were tested to investigate the influence of the type of trusses on the bending behavior of the slabs. The failure modes, cracking loads, load-deflection curves and strain distributions were obtained. The test results show that the cracking loads of precast panels are significantly improved due to the presence of the steel trusses. The crack resistance of the precast panels with steel tube trusses are the highest, which is about 194% of the panel specimens, and the maximum span reaches 9 m. In addition, different failure modes are observed when the various types of steel trusses are used. The failure modes of the plate truss, pipe truss and bar truss are buckling, weld fracture and bar bending, respectively. The collaborative mechanical behavior of the bottom panels and the concrete in composite layers are enhanced by the steel trusses. The bending behavior of the composite slabs is less sensitive to the type of trusses. The cracking loads are the same for the specimens with the different steel trusses, and the difference of the cracking deflection is less than 10%. Based on the testing results, the design formulas for buckling of the trusses were developed. It is recommended that the ultimate load should be the smaller value of that calculated from the cracking moment and the buckling moment. The calculated results are in good agreement with the test results.