N.C. SHRIVE and A. HUIZER University of Calgary

Masonry diaphragm walls of two leaves are substantially stiffer and stronger than equivalent cavity walls. Post-tensioning can increase the stiffness and strength substantially, making them attractive for high walls, or for retaining nails. However, post-tensioning of masonry walls has not been adopted in North America through some lack of knowledge on the part of designers and contractors of the techniques involved, lack of design guidance in codes of practice and concern over thermal problems which are less likely to occur in milder European climates. Initial laboratory tests on 2m high plain diaphragm walls revealed the potential robustness of this type of construction against thermal loading. Subsequently, 3 m high clay masonry diaphragm walls were subjected to temperature gradients across their widths, both unprestressed, and after the walls had been post-tensioned vertically. The thermal loading did not cause structural distress but did cause changes in the magnitude of the prestressing force.