Tension Stiffening in Reinforced Concrete Slabs

A nonlinear finite element model is used to predict the short-term behavior of reinforced concrete slabs under transverse service loads. The model is based on small deflection plate bending theory and uses a layered 16-degree-of-freedom rectangular plate bending element. The sources of material nonlinearity in reinforced concrete slabs are examined and accounted for in an incremental nonlinear solution procedure. Various methods are considered for treating the tension stiffening effect that occurs between the cracks in the tensile concrete in regions close to the reinforcement. Numerical calculations are used to assess the relative merits of these methods and to test the validity of the model. A simple treatment of the tension stiffening effect is proposed in which a modification is made to the tensile stress-strain diagram for the reinforcing steel. This produces accurate results with relatively economic use of computer time.