Research Report Rose 2008/05
Analytical and experimental research were conducted to investigate the influence of clamping stresses on the shear strength of concrete slabs under uniform loads.
Analytical and experimental research were conducted to investigate the influence of clamping stresses on the shear strength of concrete slabs under uniform loads. Including clamping stresses in the Modified Compression Field Theory (MCFT) procedures was shown to considerably increase the shear prediction accuracy for members under uniformly distributed loads. In addition, contrary to current sectional methods that give accurate results only in those regions where plane sections remain plane, results suggest that the MCFT with clamping stresses can provide reasonably accurate results in any region of a slab. Shear strength predictions from the MCFT with clamping were verified against a number of experiments from the literature and specific tests designed and carried out during this work. A total of thirteen specimens were tested under uniformly distributed loads. Ten of the specimens were continuous members, while the remaining three were simple supported slabs. Experimental results showed shear capacities considerably higher than those predicted by current concrete codes. Significant improvements in the predicted shear capacities were obtained when clamping stresses were included into the Canadian code equations (which are based on the MCFT). Additional improvements in predicted shear capacities were achieved when tension stiffening was included in the calculations, an important issue for continuous members in which the shear critical region is close to the inflection point.