Cameron Baker¹, Bruce Chen² and Robert Drysdale³

1. MASc Candidate, Civil Engineering, McMaster University, 1280 Main St. W., Hamilton, ON, L8S 4L7, bakerc@mcmaster.ca
2. Former MASc Candidate, Currently Civil Engineer, Toh and Associates Ltd., Taiwan
3. Professor and Martini, Mascarin and George Chair in Masonry Design, Director of Centre for Effective Design of Structures, McMaster University, drysdale@mcmaster.ca

ABSTRACT

The capacity of unreinforced masonry (URM) walls subjected to out-of-plane bending has been investigated in many parts of the world over the past 3 decades. This research has led to incorporation of design provisions in masonry codes in Australia, Britain and Canada. Despite a large body of test data, the majority of data available is for walls without openings and the existing design provisions are only for solid walls. Frequently in design, however, URM walls feature openings of various sizes due to doors and windows. There is, consequently, a need to investigate the out-of-plane capacity of these walls to improve understanding and develop design approaches.

This paper presents information on applying the Failure Line Method (FLM) to unreinforced concrete block walls with openings that are supported on all four edges and subject to pressure normal to the wall surface. The effects of location and size of openings were analyzed using FLM and these results were compared to experimentally determined capacities. It is shown that the FLM can be a slightly conservative but easy to apply design tool to rationally take advantage of two way bending and the inherent reserve strength available after first cracking of a masonry wall.

The FLM, recently introduced into Canadian masonry design practice for walls without openings, can, in accordance with CSA S304.1-04 [1], be extended for design of walls with openings.

KEYWORDS: URM, failure line, out-of-plane bending

4c-1