In general, load control method is used in finite element method for nonlinear structural analysis. Using this method, however, we can not realize the behavior of the structure, that is, reinforced concrete structure which has softening part after maximum load. A computer program was developed in this paper for displacement control method in which one displacement of the structure is increased and applied loads and another displacements are obtained.
From the stress-strain curves of steel and concrete, the moment-curvature relationship of the section in the beam element was derived, and using this relationship of moment-curvature, reinforced concrete beams were analyzed by displacement control method until the failure of the structure. To simplify the nonlinear structural analysis, the relationships of moment-curvature were linearised as elasto-softening model for overreinforced beam and as elasto-plastic-softening model for underreinforced beam.
Since the results of the analysis of reinforced concrete beams depended on the element size beyond elastic zone, relationship of moment-curvature was modified for each element by using the concept of fracture energy. Comparisons between theoretical and empirical results are given for load-displacement in reinforced concrete beam. Overall, analytical program accurately predicted the load-displacement behavior of reinforced concrete beams.
