Abstract
This paper summarizes test results of six heavily reinforced concrete masonry shear walls. The test programme was designed to investigate the necessity for the low ultimate shear stress specified by Masonry codes. Care was taken to accurately model good, but realistic design practice in detailing, and variables investigated in the series included steel percentage, influence of vertical load and confinement of potential crushing areas by mortar bed confining plates.
 Results are presented which clearly indicate that the maximum current code allowance for ultimate shear stress is unreasonably low. No wall suffered diagonal shear failure despite maximum shear stresses exceeding four times the maximum code level. All walls displayed stable hysteresis loops at a displacement ductility factor of 2, and the less heavily reinforced walls (designed to approximately twice code levels) were satisfactory at DF = 4. Degradation was never catastrophic and occurred due to slip of the entire wall along the foundation beam. Methods for reducing the degradation are discussed. Confining plates did not significantly reduce the degradation of the hysteresis loops, but substantially reduced damage to the walls at high ductility factors.
 Values of required ductility for walls designed to the Loadings Code are investigated, and on the basis of these and the experimental results, recommendations are made for relaxation to the ultimate shear provisions of the masonry code.
Highlights
The research described in this report was carried out for one main purpose: to establish that the maximum shear stresses allowed for masonry structures by existing(1) and proposed draft(2) N
The main purpose of these tests was to demonstrate that the limits imposed on maximum shear stress by the Masonry code are unrealistically low
No wall showed any signs of distress as a result of high diagonal shear stresses
Summary
The research described in this report was carried out for one main purpose: to establish that the maximum shear stresses allowed for masonry structures by existing(1) and proposed draft(2) N. This is of considerable importance, as recent changes in design philosophy which have been incorporated in the recently adopted Loadings code (NZS 4203) (3), together with the concepts of capacity design have resulted in the situation where many structures of four or more storeys cannot be designed in reinforced masonry because of the shear limitations. Consider the situation of a building designed for Zone Ausing external masonry shear wall elements. Assume the aspect ratio (height/width) of the walls is less than 2.0
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