PIECEWISE LINEAR BEHAVIOR OF RC BEAMS WITH OPENINGS

A method is presented in this paper to predict the load-deflection response of a reinforced-concrete beam containing a large opening. The load-deflection curve has been idealized by a piecewise linear relation in which each transition point represents the formation of a plastic hinge. The method of successive elastic analyses is used to trace the formation of hinges until a mechanism is formed. Deflections corresponding to each plastic hinge formation are calculated by linear superposition of deflections caused by flexural action on the entire beam to those produced by shear at the opening. The former is calculated using the conjugate segment analogy while the latter is obtained by treating the chord members as double cantilevers. A comparison of theoretical predictions with test data available on 12 simple supported, three two-span continuous, and five three-span continuous beams shows good agreement in load-deflection relations and modes of failure as well as maximum deflections at calculated service loads, redundant support reactions, and the load at collapse.