N. ROUMANI and M. E. PHIPPS University of Manchester Institute of Science and Technology

When a prestressed masonry diaphragm wall is laterally loaded it is subjected to the actions of bending moment, shear force and axial load. The combined effects can produce principal tensile stresses which are more critical than those created by the individual forces alone. In some cases, such as when the cross-section is an I or T shape, these stresses may lead to the development of diagonal cracking in the web which can result in a failure mechanism that is brittle in nature. This would commonly be regarded as a failure of the web in shear. Nine full sized post tensioned brickwork I section beams, 3m long, have been tested. The level of prestress and shear span to depth ratio have been examined and their effect on the shear strength with regard to serviceability and ultimate limit states is considered.