| Flat slabs system, a type of modern architecture structure becomes more and more popular. Without the maze of girt beams, the construction becomes convenient, and reduces the quantity of decorating work of floor. Comparing with frame structure, at the request of the same net height, the flat slabs system can obviously lower the floor height, thereby lower the overall height of the whole building. In this system, due to the more and more requirements on the function and esthetic from architecture, more and more non-rectangular irregular slabs are used. Current computational method is hard to solve the problem including the slab thickness of the flat slab floor, stress and amount of the distributed steel.Toward this problem, with finite element analysis and the direct design method (DDM) recommended by Building Code Requirements for Structural Concrete (ACI318-05), this kind of slab is calculated and then the following conclusions are made:Comparing with the maximum negative moment of normal slab's corner of slab, the abnormal flat slab's is larger than it, almost 1.5 times as large as the normal slab. Meanwhile, change of gradient is also large,that is for the normal slab the maximum moment only appears in some parts, while the maximum moment of the abnormal one's edge is just equal to its 60%~70%.For selecting the slab thickness of irregular flat slab, the length of the abnormal one and the ratio (λ) between missing area and the area of normal slab can be treated as rules. Then the primary selection coefficient of irregular bidirectional L-shaped flat square slab is summarized.The inner positive and negative moment of the irregular slab is also obviously distributed zonally. According to the result analyzed by concludes the classification of slab band for this slab is concluded which lays the root for applying direct design method to analyze this slab. |
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