Punching shear in pad foundations on rock

Abstract

With the increasing popularity of multi-storey buildings, foundation engineering is becoming a more important issue in the construction industry. In Malta, sound rock can normally be found at shallow depths. However, the design codes in use locally suggest a generic design process for foundations which does not take into account the type of substrate. The focus is on critical failure modes affecting reinforced concrete pad foundations on soils. The controlling parameter in the design of these foundations is found to be punching shear. The physical properties of sound rock under load suggest that a pad foundation on rock will exhibit a different behaviour than that predicted by codes. This dissertation is meant to encourage and lead the way to further research in this field of study. A review of the recommendations given by BS 8110: Part 1 (1985), Eurocode 2 prEN 1992-1-1 and ACI 318-02 on pad foundations, with particular emphasis on pu.nching shear was first carried out. It was found that, only Eurocode 2 prEN 1992-1-1 outlines briefly the issue of pad foundations on rock. An experimental research was also carried out with the aim of finding the actual concrete punching shear resistance of footings on rock. Results were compared to theoretical predictions drawn up following recommendations given by each of codes considered. Experimental results demonstrate that pad foundations on rock have a significantly higher resistance to punching shear failure than predicted by the codes.