Flexural behavior of rammed earth components reinforced with steel plates based on experimental, numerical, and analytical modeling

During past earthquakes, earthen buildings have collapsed causing significant human, economic and heritage losses. In recent years, the authors proposed a seismic rehabilitation technique used to enhance out-of-plane strength and ductility of earthen buildings. This retrofitting solution consists on adding A36 structural steel plates (6.35-mm-thickness and 101.6-mm-width) on both faces of the earthen walls. This proposal enhances seismic performance of earthen structures while protecting occupant lives and reducing expected damages. In this paper, a comprehensive experimental, analytical and numerical study is conducted to evaluate the influence exerted by the amount of steel plates on the out-of-plane strength in reinforced earthen walls. The experimental program includes tests for rammed earth specimens reinforced with different sizes of steel plates. Experimental results are complemented with finite element simulations and analytical formulations based on partially composite beams with interlayer slip. Despite the high variability involved in the mechanical properties of earthen materials and uncertainty in the interaction between the steel plates and the rammed earth, models used in this study predict out-of-plane strength of reinforced earthen specimens within 15% error. In addition, based on experimental evidence, the authors proposed an empirical design equation to calculate the moment or flexural capacity that could be included in retrofitting provisions.