Investigation of Short Term Deflection of Reinforced Concrete Flat Slabs

Abstract

This research is dedicated to correct the short term of concrete flat slab deflection calculated based Branson equation used in both on ACI 318 code and ECB-207 code, Calculated deflection from this equation is overestimated from actual behavior, A correction factor for deflection calculated from Branson equation is the main objective for this research. After verification of ABAQUS software as FEM simulation of flat slab behavior, a parametric study is made on total of 75 square simply supported flat slab and 75 one way simply supported flat slab, those slabs are modeled using both CSI SAFE (using ACI-318 Cracking Criteria) in both tangent and incremental model. And ABAQUS (using CPDM behavior for concrete model) to present load deflection difference of each case on each model. Finally, for two-way flat slab, charts were presented for different cases of lower& top reinforcement ratios to correct the deflection calculated from CSI SAFE (Using ACI318 equation and cracking criteria), on the other hand, Correction Factor for Branson's equation Used in both on ACI 318 code and ECB-207 code is presented for one way flat slabs. 6.2 Conclusions This study presents correction for CSI SAFE short term deflection (based on Branson equation used in ACI318-14) in two way flat slabs though out correction charts for specific: 1) Loading Methodology 2) Top reinforcement ratio. 3) Lower reinforcement ratio. 4) Effect of increasing load 5) Span of Flat Slab These charts are relations between span of square simply supported slab verses normalized deflection (∆cracked/∆ABAQUS) for various λ= (Mact/Mcr) values, as the correction factor is the value of the normalized deflection extracted from those charts.