Study on Development of Steel-Free Concrete Deck Slabs

(1)首先进行了无钢板的加载试验，以明确极限强度和挠度。在这些试验中，用于约束混凝土板的钢板的厚度和宽度被视为可变参数。从这些试验结果可以看出，约束比的增大对破坏模式由弯曲破坏向剪切破坏的转变有很大影响。通过对简支板和固定板在预应力和非预应力两种情况下的试验和理论研究，研究了端部支承条件和预应力对无钢板受弯性能的影响。第二组试验的结果如下：1)端部支承约束对无钢板开裂前的约束是有效的，但在开裂后是不可靠的。2)体外预应力对提高开裂荷载和极限荷载都是有效的。(3)第三系列荷载试验是对6块足尺无筋横向预应力无粘结体外筋板的冲压试验。结果表明，无粘结预应力和混凝土强度在一定程度上提高了极限冲压荷载，但对提高开裂荷载影响不大。预应力在控制裂缝发展方面是有效的，这意味着板的使用性能有了很大的提高。(4)总结了1999-2001年两年的成果，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.