Limitations of Flexural Crack Width in Simply Supported One-Way Ribbed Slab

Abstract

The important consideration in design of multistory concrete buildings is reducing self-weight of the slabs. The system of one-way ribbed slab is one of the many systems chosen in order to reduce self-weight. This reduction occurs in concrete only for what causes high tensile stress in bottom fiber of concrete lead to cracking although the section is reinforced according to design specifications. Limitations of ACI 224R-01 2008 of maximum allowable crack width is 0.3 mm for members’ exposure to humidity, moist air, or soil. The experimental work in this research includes five simply supported reinforced concrete one-way ribbed slab with same dimensions and different in ratio of bottom steel reinforcement. The five specimens have reinforcement ratios of 0.0009, 0.0013, 0.0023, 0.0037, and 0.0059 respectively. The aim of this research is checking experimental crack width at design load with permissible limitations according to ACI 224R-01 2008. The experimental work and the theoretical calculations, for all the specimens, are cracked sections where the first crack appears at load less than design load. At design load the specimens with low and moderate reinforcement ratio 0.0009, 0.0013 and 0.0023 show crack width less than permissible value of 0.3 mm, while the specimens with high reinforcement ratio 0.0037 and 0.0059 show crack width more than permissible value of 0.3 mm, where the increases in width of crack causes reducing in the durability of members. At linear stage, the mid span deflection is decreasing as reinforcement ratio increase at same step of loading for all specimens. Finally, in the design of one-way ribbed slab, the emphasis is on checking the width of cracks according to codes permissible limitation and it is recommended to use low or moderate reinforcement ratio in this system of slabs.
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