ANALYSIS OF P-DELTA EFFECT IN COMPOSITE CONCRETE TIMBER BEAM COLUMNS

The procedure for analysing composite beam-columns of timber and concrete is developed. The influence of the interlayer slip is considered in the theoretical development. Closed form solutions for the internal axial forces and moments, which act on the timber and concrete components, and the slip forces are presented for the first-order (elementary) and the second-order (P - DELTA) cases. Approximate formulae for determining the magnification factors to be applied to the internal actions computed in the elementary case in order to account for the P-DELTA effect are recommended for simply supported members. A comparision is made between the results obtained from the application of the approximate formulae and the second-order analysis approach for the case of a practical beam-column to illustrate the applicability of the approximate formulae in design situations.