Biaxial flexure and axial load interaction in short rectangular reinforced concrete columns

Abstract

It was only recently that structural designers in New Zealand became aware of the need to consider earthquake actions generated concurrently with respect to the principal axes of multistorey buildings. It became evident that reinforced concrete columns adequately designed for separate participation in two frames, which are expected to resist seismic loads at right angles to each other, may in fact be subjected to pre-mature hinging when beams, framing into such columns from two directions, develop their full capacity. To ensure a desirable response of reinforced concrete frames to large seismic disturbances it will be necessary to check out each column of the structure against such skew effects. A recent study, in which the elasto-plastic response of a prototype structure to the concurrent North-South and East-West components of the 1940 El-Centro Earthquake was examined, showed this clearly (i). The first step in this is to assess the strength of a reinforced concrete column section, preferably with a minimum of computational effort.