Investigation of Deflection and Cracks in Reinforced Concrete Solid Slabs as a Function of Thickness Using Staad Pro and Tekla Tedds

Abstract

In this study, the effect of variation of thickness of slab on the deflection and crack width of solid slabs were analysed. The thickness of the slab were varied by 150 mm, 175 mm and 200 mm. The design conditions also varied were concrete grade, spacing of reinforcement and size of reinforcement. A two-way slab of size 6 m by 5 m was loaded with varying dead loads and constant live loads and analysed in StaadPro to obtain the internal stresses. Thereafter, the results of the internal stresses were applied in Tekla Tedds software while varying the design conditions to examine the effect on deflection and crack widths. The results obtained showed that as the thickness of the slab increases, the allowable span/effective depth ratio (l/d) increases which implies that the slab is less likely to fail deflection check at higher thickness. For cracking, as the concrete thickness increases, the crack width becomes smaller. Average increase in allowable l/d for different slabs was 13% while an average of 41% change in the values was observed for the crack width as the thickness of the slab was varied. Increase in concrete grade was observed to cause an average of 17% increase in the allowable l/d values. However, in the evaluation of the crack width, the maximum change brought upon by change in the grade of concrete was just 0.8%. Increasing bar size and reducing bar spacing also helped to reduce slab susceptibility to deflection and cracks.