ASSESSMENT, ANALYSIS AND CONSERVATION OF TRADITIONAL AND HERITAGE BUILDINGS

Abstract

Construction practices used in Northern India depend on regional, cultural, historical, and environmental factors. Construction practice is highly influenced by locally available brick, stone, and wood materials. Traditional practices, on the other hand, result from cultural influences and the construction style of upgrading and passing knowledge from generation to generation. Although these systems have proven to be very good under seismic loading conditions, very little research has been done to identify engineering features such as load transferring mechanism, failure mechanism, load carrying capacity, ductility etc. In this research work, a reaction frame setup is proposed. The assembly is designed to facilitate a preliminary understanding of behavioural patterns of movement (also deformation, if any) in different elements of a building under applied vertical and horizontal loads. To understand the earthquake resistance properties of this traditional construction system and its behaviour, push-over in-plane wall tests were performed on a full-scale and scaled-down wall model, and the results were compared with conventional brick masonry wall specimens. The ultimate failure pattern of the traditional Kath-Kuni wall is observed due to the rotation of the perpendicular wooden beams along with infill pieces. The load-resistance capacity and ductile behavior of Kath-Kuni walls primarily depend on their wooden joints. The traditional Kath-Kuni system shows a better horizontal load-carrying capacity than conventional brick masonry, as the Vmax/P ratio is computed as 0.58-0.63 for Kath-Kuni and 0.37 for brick masonry. The failure pattern of both traditional Maanwi and Kadil connection is found brittle. The Maanwi connection exhibits initial adjustment with large rotations after failure, and the Kadil connection shows relative displacement between members after the failure. This rotational and displacement-oriented behaviour of traditional joints with the comparatively high damping nature of wood allows the Kath-Kuni construction system to undergo large deformation, ultimately allowing the whole system to be earthquake-efficient. Furthermore, to conserve this traditional knowledge system, a reinterpretation solution for masonry walls is provided. This proposed construction system addresses the problems associated with these construction systems while maintaining its structural capacity. In the proposed structural system, a combination of vertical and horizontal members with concrete blocks is used. These combinations of horizontal wooden and vertical steel members are responsible not only for the behaviour of masonry as a unit but also for its enhanced structural load-carrying capacity. In the re-interpreted solution, the usage of wood material has decreased by up to 10% of the total wall volume. Concrete of grade M25 was used in place of stones (as used in traditional structures) to address the scarcity of stones for construction. For the proposed wall model, the maximum load observed was 120 kN, which is almost 135% of the applied vertical load (88 kN), which is significantly higher than the brick masonry and Kath-Kuni. Ultimate failure mechanism was observed as toe crushing of the masonry followed by sliding of the upper half of the wall, no major damage in the wooden members and joints was found, which indicates the lower stressing on the joints upon loading in proposed system. In the present study a retrofitting scheme, inspired from traditional construction system, is proposed. Brick masonry has very high compressive strength, but when subjected to lateral forces such as earthquakes, its load-carrying capacity reduces significantly. Improving these structures' tensile and shear properties is challenging. The present research proposes a new retrofitting technique that uses wood and steel as primary materials. Wooden members are provided at different locations on masonry wall and interconnected with the help of steel angle sections. A push-over analysis of brick masonry walls (IITR_BW1) and retrofitted walls (IITR_RBW1 and IITR_RBW2) is done to understand the behaviour and capacity of the proposed retrofitting technique compared to conventional brick masonry. As the proposed system undergoes large deformations before failure, the behaviour factor R, which describes the ductility of the wall, was calculated as 4.53 for a ductility of 10.8. The wood used for retrofitting is 2% of the total wall volume, which is much less when compared to 35-50% used in traditional Kath-Kuni systems. Also, no wooden member is exposed to the external environment in the proposed system, which will ultimately control the degradation of wooden members due to external environment conditions.