Enhancing Lateral Load Performance of Traditional Timber Wall (Dhajji-Dewari) By Strengthening of Joints

Abstract

Dhajji Dewari is an open construction technique that can be easily built from local materials; timber and stone. Dhajji most commonly consists of a braced timber frame and the spaces left within the timber frame are filled with a thin wall of stones usually laid and plastered with mud mortar. Dhajji Dewari provides efficient use of material even with single layer of infill compared to modern construction techniques. The construction of houses after October, 2005 Kashmir earthquake was indecisive task. The donor agencies were not sure if the traditional structure would give better performance in case of similar magnitude Earthquake. Very limited research was available to validate the seismic performance of Dhajji Dewari construction. Later on it was experimentally proved that Dhajji construction is suitable for lateral resistance and additionally, it is suitable for remote areas, such as Kashmir where availability of skilled labor is limited due to ease of construction. This thesis presents experimental work conducted on typical Dhajji Dewari walls found in northern areas of Pakistan and Kashmir, to evaluate their in plane lateral load response by using different joint strengthening techniques. The experimental work includes an in-plane monotonic test on four reduced scale walls. Out of four Dhajji walls, one wall was used without any strengthening and considered as reference wall. The remaining walls were strengthened with three different strengthening techniques. Cross bracing was used between closely spaced vertical posts and infill ratio of stone and mud was constant and it contains 70% stone and 30% mud. Test results show that the connection functionality, controls the overall performance of the system, particularly at the joint of vertical posts and bottom plates. Strengthening of these joints not only enhances the lateral load capacity of the wall, but also significantly augments the energy dissipation capacity of the system. The performance of strengthening techniques has been experienced and based on cost benefit analysis it is concluded that wall strengthened with metal strips give the best reinforcement of Dhajji walls keeping in view the additional cost of strengthening and load deformation behavior.