(1) Research Scholar, Department of Civil Engineering, IIT Madras, Chennai, India, 600036

(2) Professor, Department of Civil Engineering, IIT Madras, Chennai, India, 600036



Unreinforced masonry buildings with relatively flexible diaphragms are considered to be composed of a primary system consisting of the vertical lateral load resisting elements, and a secondary system consisting of the diaphragm and the supporting out-of-plane walls. Often structural assessment of the secondary system is carried out without explicitly accounting for the integral response between the diaphragm and out-of-plane walls. This is particularly relevant when integral action is ensured between relatively flexible/semi-rigid diaphragms and out-of-plane walls with moderate-high axial loads, through strong walldiaphragm connections employed as part of strengthening measures adopted. In addition, this also affects the out-ofplane assessment of walls with the displacement demands acting on the wall altered due to the degree of connectivity with the diaphragm. The current work focuses on the possible implications of considering an integral diaphragm-out-ofplane wall response in the seismic assessment of masonry buildings by adopting the case of the Madras Terrace floor, a commonly observed diaphragm typology in southern India. Results indicate that the role of out-of-plane walls in the integral diaphragm-wall response cannot be neglected, particularly for the ground level walls, in terms of strength capacity, stiffness and energy dissipation. Also, the stability of out-of-plane walls cannot be defined solely based on slenderness ratios, but the effects of diaphragm stiffness also need to be accounted for.


KEYWORDS – Unreinforced masonry, Diaphragm wall characterization, Out-of-plane assessment