ROLE OF HORIZONTAL TIMBER BANDS IN THE OUT-OF-PLANE BEHAVIOUR OF MASONRY STRUCTURES IN THE HIMALAYAS

Masonry structures occupy a significant share of the current building stock due to widespread material availability and cost-effectiveness. Regions with high seismicity, such as the Himalayas, have often developed a local seismic culture over the centuries. This has led to improved construction techniques providing an enhanced seismic performance, as evident from post-earthquake surveys in this area. In this framework, Bhatar is a building typology found in the greater Himalayan region, which features embedded horizontal timber bands in masonry walls, enhancing the box-behaviour and in turn avoiding their premature out-of-plane failure. This work aims to quantify the improvement of the out-of-plane performance of masonry walls because of the presence of horizontal timber bands. In order to achieve this research objective, numerical analyses were conducted in DIANA FEA finite element software starting from the few experimental results on this building typology available in the literature. These were used to calibrate the properties of masonry, which was represented as a homogeneous isotropic continuum, with nonlinearities taken into account by means of a total strain rotating crack model. Firstly, a U-shaped masonry wall having the same geometry and boundary conditions as the experimental tests was simulated using a 3D modelling approach. Non-linear static analyses were performed and very good agreement was obtained with the results from the literature. On this basis, the calibrated numerical model was then employed to conduct sensitivity analyses considering varying factors, such as masonry material properties, geometry, opening configurations, timber section sizes and properties. The outcomes of this extensive study show a considerable improvement in the out-of-plane response of the masonry walls in the presence of horizontal timber bands. Given the limited research conducted on the Bhatar building typology in the past, this work constitutes a further step towards a better understanding of the behaviour of Himalayan masonry structures under earthquakes, promoting more effective seismic risk reduction strategies. This improved understanding into timber’s role in imparting greater seismic resilience to masonry structures can inform better maintenance, conservation and preservation of heritage and historical masonry structures in the Himalayas.