Membrane effect in the reinforced concrete frames—a proposal for change in the design of frames structures

This paper is concerned with the effect of membrane action or arching action on the behaviour of reinforced concrete frames. An experimental programme designed to investigate the behaviour of frames at ultimate conditions was carried out. The results indicated that failure of the frame was either by ductile failure of the beam or brittle failure of the column, depending on the degree of end restraint provided to the beams by the columns. The most significant effect of the membrane forces on the behaviour of the frame was to greatly increase the bending moment imposed on the column. Due to the development of the membrane forces, the distribution and magnitude of the moment in the column and mode of failure of the frame was very different to that predicted using normal analysis methods. Rigid–plastic analysis was used to predict conditions close to failure. This approach, together with a method for estimating the ultimate stiffness of the columns, enables the failure condition to be predicted. On the basis of a combination of experimental and theoretical models, a method for allowing for membrane effects in the design of frames is presented.