Nonlinear analysis of RC beams based on moment–curvature relation

Material nonlinear analyses of reinforced concrete (RC) beams considering the tension softening branch and bond slip have been conducted. Instead of adopting the sophisticated layer approach which has some limitations in application to large structures with many degrees of freedom, we have used the moment–curvature relationships of RC sections previously constructed through section analysis. To reduce numerical instability according to the finite element mesh size used, a relation simulating the tension softening branch has been taken into consideration. For the purpose of removing the imprecision in calculation of ultimate resisting capacity, we have included the plastic hinge length in finite element modeling. In addition, governing equations describing the bond-slip behavior in beams have been derived. Unlike the conventional bond elements using double nodes, the proposed model has used beam elements representing the structural response by two nodes at both ends, and has simplified the finite elements modeling and analytical process, besides effectively describing the bond-slip behavior. Moreover, the developed algorithm has been reflected in the moment–curvature relationship of RC section. Finally, correlation studies between analytical and experimental results have been conducted with the objective to establish the validity of the proposed algorithms.