Structural Stability Evaluation of Natural Fiber Retrofitted Low-Cost Rammed Earthen Houses Under Seismic Loading

Abstract

Earthen houses constructed using the rammed technique have long served for housing across the globe. However, despite their environmental benefits, these houses may pose unacceptable earthquake risks for the communities. To address this, the current study focuses on investigating the seismic response of unreinforced and retrofitted rammed earth model houses using unidirectional shaking table experiments. Retrofitting is performed using two different approaches. The first method is the traditional way using cement, lime and natural fibers like straw and jute mixed with soil. The second method is a new and innovative approach that uses bitumen-treated natural fibers such as jute and bamboo strips as external encasing reinforcement along with special L-shaped corner reinforcement using jute and bamboo sheets. The study shows that rammed earth houses retrofitted using the proposed novel and low-cost methods with jute/bamboo fibers demonstrate promising results in terms of structural strength and ductility compared to the stabilized counterpart. The fundamental period of the retrofitted and unreinforced houses is found in the order of 0.08 and 0.12 indicating an enhancement in lateral stiffness depending on various level retrofitting methods. The study provides valuable insights and points toward potential changes in the seismic design guidelines for low-cost rammed earthen houses.