Bearing Capacity of Concrete Blocks

Theoretical and experimental results are presented for the bearing capacity of concrete blocks with an axially or eccentrically located cable duct and axially or eccentrically loaded by two rigid punches. The solutions have been obtained using the concept and the theory developed recently by Chen and Drucker. The problem considered here is closely related to the bearing strength of the anchorage zone of a prestressed concrete beam. More important, these solutions provide additional theoretical and experimental evidence as to the validity and limitations of the theory of perfect plasticity as applied to bearing capacity problems in concrete. In the analysis, it was found that the upper bound theorem of limit analysis may be used to predict the bearing strength of an eccentrically loaded concrete block. However, when the eccentricity ratio of the punch load is large, crack propagation does enter for such a situation. An appropriate fracture mechanics for concrete is needed. Nevertheless, the solutions obtained herein still provide a reasonable upper bound for fractured concrete. The agreement between the theory and experimental results is satisfactory. These solutions should provide a better understanding of the bearing strength of the anchorage zones of post-tensioned concrete members.