Maximum and Residual Flexural Crack Width Estimation in Reinforced Concrete Frame Members under Seismic Excitation

Abstract

During strong seismic excitations, reinforced concrete (RC) frame members experience several cycles of nonlinear response that may result in large cracks. At the end of the excitation, the residual member crack widths are reduced compared to their maximum transient crack width. Interpretation of maximum and residual crack widths in RC frame members under cyclic stress reversal is very important for condition assessment of the damaged members after an earthquake. Similarly, accurate prediction of crack widths in RC frame members is very important for the performance assessment of buildings under postulated seismic excitations. In this paper, new expressions to estimate maximum flexural crack width and residual crack width in RC frame members under service loads, as well as cyclic load reversals, have been presented. The expressions are valid for both linear and nonlinear response ranges of the frame members. The expression for the maximum crack width accounts for alteration from flexural to shear-dominating damage modes caused by an increase in axial load. The residual crack width is found to depend on maximum crack width and maximum curvature ductility demand. It is not significantly affected by stress reversal imposed by cyclic loads. The proposed expressions are found to match well with experimental observations in the published literature.