Investigation of reinforced concrete frame behaviour—theory and tests

Abstract

The nonlinear behaviour of reinforced concrete frames with sidesway is governed by two efects: first the nonlinearity of materials due to cracking and the plastic behaviour of materials, and second the nonlinearity of geometry caused by the second-order deformation. These two efects may interact, and the whole phenomenon is known as the nonlinearity of geometry and materials. Reinforced concrete frames are frequently used to resist wind or earthquake forces. These forces will accentuate the complexity of the frame behaviour because of the continuous change of the shape of the bending moment diagram. The change of moment diagram will in turn afect the magnitude of the cumulative plastic rotations. A trilinear theory was devised to predict theoretically the moment-load curves of reinforced concrete frames throughout the loading history. This method utilized the trilinear moment-curvature curve for critical sections, as well as the principle of virtual work to express the compatibility condition and to find deflections. The theoretical prediction was checked by experiments with nine small-scale reinforced concrete frames. The materials for these frames were found to be acceptable, as reported in the companion Paper. The comparison indicates that both the theory and the tests are in good agreement throughout the loading history.