Experimental evaluation of the interaction between a masonry infill wall and the surrounding frame

This paper studies the interaction effects between a masonry infill wall and its surrounding frame. A new experimental technique is developed aiming at evaluating the loading dependent interaction effects. This includes the stage where the infill wall accumulates severe damage and cracking that are difficult to monitor with conventional devices (strain gauges and displacement transducers) or optical techniques such as digital image correlation (DIC). The experimental concept is based on detection of strains along the surrounding frame, their conversion into stress resultants, and the translation of the latter into interfacial contact tractions. It also aims at identifying the regions of contact and detachment between the frame and the infill wall and their changes during the loading path. A large-scale experimental setup that realises the concept and demonstrates its ability to provide important new information is constructed. A complementary DIC analysis that serves as reference for the above monitoring system is also conducted. This experimental setup with its complementing combination of sensing methods allows measuring the infill wall-frame interaction effects in a case of horizontal loading that simulates lateral seismic loads, as well as vertical loading that simulated a mechanism of progressive collapse triggered by failure of a supporting column. The paper presents the experimental concept and its implementation in the large-scale experimental setup and explores its capabilities. Emphasis is given to the interaction effects in the deep non-linear region where optical monitoring is adversely affected by the developing damage. The proposed experimental technique is found to be very effective and provides new information regarding the interaction of the infill wall with the surrounding frame. It is demonstrated by an experimental study simulating the loss of a frame supporting column thus enhancing the understanding of the infill wall role in the frame resistance and its contribution to avoid progressive collapse.