Experimental Testing of Tall Slender Masonry Walls with Different Rotational Base Stiffnesses

Abstract

Loadbearing, concrete masonry walls are an effective structural system to resist combined out-of-plane and gravity loads. A large portion of the market for these walls is composed of single-story warehouse and industry buildings, and public-use structures such as theaters, community centers, and school gymnasiums. In these applications, it is common to have tall walls with an effective height-to-thickness ratio greater than 30. North American masonry design standards (CSA S304-14 and TMS 402-16) have special design requirements for these types of masonry walls due to their perceived vulnerability to second-order effects. In particular, one of the CSA S304-14 requirements consists of assuming a pinned base condition to calculate design moments and deflections, which severely impacts the available strength and stiffness of tall masonry walls. The objective of this study is to assess the influence of the rotational base stiffness on the out-of-plane response of slender masonry walls subjected to cyclic loading, in terms of strength, stiffness, base damage, and failure modes. Two full-scale, partially grouted slender masonry walls were tested under combined eccentric axial load and cyclic lateral out-of-plane pressure. The tests showed increased flexural capacity and decreased deflections in the out-of-plane direction when rotational stiffness at the base is accounted for, with limited degradation at the wall base observed during cyclic loading. Results suggest that accounting for the presence of the base stiffness provides additional strength to the wall that may lead to more economical masonry wall designs while maintaining satisfactory strength and reliable structural performance.