Design of tie-columns in confined masonry structures for lateral loads

Confined masonry (CM) buildings are generally designed with an expectation that masonry walls withstand all possible loads imparted on the buildings. The reinforced concrete (RC) confining members, also known as tie-members, have the sole purpose of constraining the masonry and avoiding its outward spread during lateral earthquake loading. Reliable design rules for tie-columns are scarce in design codes of CM structures, often resulting in the nominal design of tie-elements without considering the influence of all the important parameters related to the material and geometric properties of CM wall. This often results in the construction of weaker tie-members, especially the tie-columns, that can lead to their direct failure and the failure of the entire wall during earthquakes. To address this issue, a methodology was developed for assessing the design shear forces for the tie-columns as well as masonry subjected to lateral loading by utilizing the past observations from systematic experimental and numerical studies. The efficacy of this methodology was evaluated in the present experimental study conducted on CM walls with varying aspect ratios. The test results demonstrated that the proposed methodology can result in a significant improvement in the lateral load behavior of CM walls, by delaying the shear failure of tie-columns without jeopardizing other functional requirements.