Shear behaviour of reinforced concrete pile caps under full-width loading

Abstract

There has been discrepancy in the design procedures for reinforced concrete (RC) pile caps in the UK design codes BS 8110 and BS 5400 that arose from the independent development of semi-empirical bending theory-based shear design formulae based on limited experimental data. Stimulated by the advent of the Eurocodes, a series of reduced-scale RC pile caps were tested under full-width wall loading to investigate their real shear capacity. The British Standards have been confirmed to be conservative, with the degree of conservatism found to be a function of shear enhancement factor and the width of cap over which shear enhancement is applied. The strut-and-tie model from BS 8110 gave better agreement with the experimental results, although the limit on the width of the tension tie of three pile diameters meant it became conservative at wide transverse pile spacings. A revision to the strut-and-tie model is proposed, in which longitudinal reinforcement across 90% of the cap width is considered to participate in the yielding tie.