Seismic retrofitting of existing earthen structures using steel plates

•A novel retrofitting is proposed to enhance the seismic performance of earthen walls.•Connections between steel plates and earthen walls were tested.•Five full-scale pier walls were experimentally characterized.•Three full-scale corner walls were subjected to shaking-table tests.•The solution substantially increases stiffness, strength, ductility, and stability. During past earthquakes, existing earthen buildings have suffered severe damage or total collapse leading to fatalities and major economic and cultural losses. Poor mechanical properties, out-of-plane instability, lack of seismic diaphragms, and low strength of the connections between structural elements are the most common problems with these types of vernacular constructions. In this research, a novel retrofitting solution, based on steel plates, is proposed to enhance the seismic performance of earthen structures while protecting the life of the occupants and reducing the expected damages. A comprehensive experimental program is conducted to evaluate the seismic behaviour of earthen structural components under both unretrofitted and retrofitted conditions. The experimental program includes four cyclic tests of the proposed connections between steel plates and walls, five cyclic tests of earthen piers, and three full scale shaking table tests of 3.50 m high × 0.60 m thick walls. Observed damage states were related to measured drifts (for cyclic tests) and peak ground accelerations (for dynamic tests). Tests results show that the proposed retrofitting technique substantially increases the stiffness, strength, ductility, and stability of the specimens, which reduces damages and permanent displacements. Retrofitted specimen supported accelerations larger than 1.64g at the roof height without collapse; residual drifts for these demands did not exceed 1.1%.