Punching resistance of RC slabs with rectangular columns

Fifteen tests on high strength concrete slabs with rectangular supports and three different load patterns are reported. The results show that current code preovisions can overestimate punching resistance in some cases. An investigation, made using the finite element method, shows the influences of the shape of a support and the pattern of loading on the distribution of shear. Factors are proposed to allow for these effects while using the control perimeter and basic shear resistance of the CEB Model Code 90, and it is demonstrated that this approach provides strength estimates better than those of MC 90, BS 8110 and ACI 318. There remains a problem of the punching capacity of slabs almost failing in flexure and this is discussed.