Bi-axial shaking table tests to evaluate the seismic performance of two-story rammed-earth walls retrofitted with steel plates

Abstract

Worldwide, unreinforced earthen buildings have shown poor performance during earthquakes, causing deaths and loss of property. The Spaniards that conquest the Americas built with earthen materials for about four centuries and therefore, there are a large number of historic buildings in the northern Andean zone of South America. This territory is geographically located in intermediate and high seismic hazard zones. Over the last few years, the authors proposed a seismic reinforcement system for historic earthen buildings based on A36 steel plates (100 mm x 6.35 mm) installed on both sides of the walls. However, to date, the studies had been focused on tests of one-story buildings subjected to in-plane pseudo-static loads or uniaxial dynamic loads. For this reason, this research assesses the seismic performance of two-story rammed-earth (RE) walls subjected to ground motions using a bidirectional shaking table. Two 1:2 scale RE walls (one retrofitted with steel plates and another unreinforced) were tested. The specimens were two-story walls with a "C" shape, similar to that found in heritage buildings of the Historic Center of Bogota (HCB). Based on the experimental tests, the unretrofitted wall presented irreparable damage at acceleration levels higher than 0.34g. In contrast, the retrofitted wall had excellent performance with lower damage levels and residual drifts; this specimen was highly resilient, withstanding earthquakes with peak ground acceleration (PGA) greater than 0.76g.