APPLICATION OF CAPACITY DESIGN PHILOSOPHY TO GRAVITY LOAD DOMINATED DUCTILE REINFORCED CONCRETE FRAMES.

Abstract

Indiscriminate application of the capacity design philosophy can lead to unnecessary or indeed absurd conservatism in the earthquake resistant design of gravity load dominated ductile reinforced concrete frames. Low-rise framed buildings are typical examples. The origin of excessive potential strength with respect to lateral loading is discussed and proposals are made to establish an acceptable upper bound for lateral load carrying capacity in such frames. A technique is presented by which the successive formation of potential plastic hinges, involving partial beam sway mechanisms, can be conveniently assured. While retaining the requirements for energy dissipation in beams is postulated that at an acceptable high level of lateral loading the formation of story mechanisms, necessary to complete the frame sway mechanisms, should be tolerable. Examples are given to illustrate the determination of design quantities for bending moments, shear and axial forces for both, beams and columns.