S.J. LAWRENCE (1), M.G. STEWART (2)
(1) Conjoint Professor, Centre for Infrastructure Performance and Reliability, School of Engineering, The University of Newcastle, Callaghan NSW 2308 Australia
(2) Professor and Director, Centre for Infrastructure Performance and Reliability, School of Engineering, The University of Newcastle, Callaghan NSW 2308 Australia
The paper develops a methodology for assessing the reliability of unreinforced masonry walls in vertical bending and for calibrating the capacity reduction factor or partial safety factor for bending. Different factors influencing the reliability of masonry in vertical bending are studied, including model error, wall height and discretisation of wall thickness. A probabilistic model for model error is derived from a statistical analysis of 118 wall test results and statistics for flexural tensile strength are obtained from a database of 7,332 individual bond strength measurements. The reliability index corresponding to the current capacity reduction factor in the Australian Masonry Structures Code AS 3700 (f = 0.6) lies approximately mid-way between the values 3.8 and 4.3. When comparing reliabilities with a target reliability index it was found that the capacity reduction factor may need to be decreased to 0.47. However, the effect of wall length and mortar type needs to be examined further to assess their effect on reliability and to consider whether an improved behaviour model could be used.