Study on Development of Steel-Free Concrete Deck Slabs

(1)对无钢板进行了首次加载试验，以明确其极限强度和挠度。在这些试验中，用于约束混凝土板的钢板厚度和宽度被视为可变参数。从试验结果来看，约束比的增大对试件破坏模式由弯曲破坏向剪切破坏的转变有较大影响。然而，当约束比大于2%时，强度并没有显著提高。(2)通过对简支和固定板在预应力和无预应力两种情况下的试验和理论研究，探讨了端支状态和预应力对无钢板抗弯性能的影响。第二组试验的结果可总结如下：1)端支约束对无钢板开裂前的抑制有效，但开裂后的抑制不可靠。2)外部预应力对增加开裂和极限荷载均有效。(3)第三系列荷载试验是在6块无粘结外筋横向预应力的全尺寸无钢板上进行冲孔试验。结果表明：无粘结预应力和混凝土强度对极限冲孔荷载有一定的提高作用，但对开裂荷载的提高作用不大；预应力对控制裂缝的发展具有有效的作用，这意味着在很大程度上提高了楼板的使用性能。(4)总结了1999年至2001年两年的所有结果，并完成了报告。

(1)First series of loading tests for steel-free slabs were carried out to clarify ultimate strength and deflection. In these tests, the thickness and width of steel plate used to confine the concrete slabs were considered as variable parameter. From these tests results, the increase of confinement ratio has drastically influenced the change of failure mode from bending to shear failure. However higher confinement ratios than 2% have not increased the strength significantly.(2)Effect of the end supports condition and prestressing on the flexural behavior of steel-free slab by undergoing an experimental and theoretical study on a simple supported and fixed slabs in both prestressed and non-prestressed cases were investigated. The results obtained from the second series of tests can be summarized as follows ; 1)End support confinement is efficient in restraining the steel-free slabs before cracking, but it is not reliable after cracking. 2)External prestressing is effective in increasing both cracking and ultimate loads.(3)Third series of load tests are punching tests on six full scale steel-free slabs transversely prestressed with unbonded external bars. The obtained results showed that unbonded prestressing and concrete strength increased the ultimate punching load to some extent but no considerable effect on increasing the cracking load was obtained. Prestressing proved efficiency in controlling cracks development, which means a great improvement on the serviceability of the slab.(4)All results of two years from 1999 to 2001 were summarized and the report was completed.