A variable layering system for nonlinear analysis of reinforced concrete plane frames

An improved method has been developed for the computation of the section forces andstiffness in nonlinear finite element analysis of RC plane frames. The need for a new approach arisesbecause the conventional technique may have a questionable level of efficiency if a large number oflayers is specified and a questionable level of accuracy if a smaller number is used. The proposedtechnique is based on automatically dividing the section into zones of similar state of stress and tangentmodulus and then numerically integrating within each zone to evaluate the sectional stiffness parametersand forces. In the new system, the size, number and location of the layers vary with the state of thestrains in the cross section. The proposed method shows a significant improvement in time requirementand accuracy in comparison with the conventional layered approach. The computer program based on thenew technique has been used successfully to predict the experimental load-deflection response of a RCframe and good agreement with test and other numerical results have been obtained.