The out-of-plane behaviour of reinforced concrete masonry walls with window openings.
Thesis DisciplineCivil Engineering
Degree GrantorUniversity of Canterbury
Degree NameMaster of Engineering
The aim of this research was to construct and test a partially grouted reinforced concrete masonry wall with window openings under out-of-plane loading and evaluate its behaviour. The behaviour of the wall was compared with the results of various theoretical models, and the accuracy of these models was evaluated relative to the experimental results. The specimen was 9.4m long with 1.8m long return walls at each end, giving it a Cshaped plan. Windows were sited to reduce the out-of-plane strength - a comer window at one end and a window that sat astride the 45° yield line near the other end. 20-series concrete blocks were used to form the wall, with D12 vertical reinforcing at 800mm centres, giving a vertical steel ratio of 0.074%, and 2 D16 bars horizontally forming a bond beam in the two upper masonry courses. The wall was partially grouted, with only cells containing reinforcement filled. The steel used was the minimum required by NZS 4229: 1999, with some minor modifications. The wall was founded on a Ribraft waffle slab flooring system. The test specimen behaved in a ductile manner, with a highly pinched hysteresis response. The ultimate strength of the wall was 5.8kPa at 2% interstorey drift, which is specified in NZS 4203: 1992 as the maximum allowable structural displacement for this type of structure. This is 40% higher than the maximum calculated ultimate limit state loading of 3.5kPa. Load carrying capacity did not decrease at very high post-elastic deflections. Because of this, it has been determined that the design of partially grouted masonry walls for out-of-plane loading is governed by deflection, not strength, requirements. Different analysis techniques were used to calculate the response of the wall prior to testing. Finite element modelling in ABAQUS provided a good match with experimental data. Yield line theory was found to give a conservative value for the ultimate load. A modification to yield line theory to model load-displacement response was proposed, with results obtained from a simple model giving reasonably accurate results at high deflections.