Experimental Assessment of Three Simple Techniques for the Seismic Retrofitting of Heritage Earthen Structures

An experimental program was conducted to evaluate simple retrofitting techniques that could preserve historical buildings in Colombia. This paper presents experimental results from 28 full-scale adobe and RE walls subjected to in-plane and out-of-plane lateral cyclic loading, overturning, and shake table excitations. Geometries included solid walls, wall piers, flanged/corner walls, and walls with openings. Specimen dimensions were 0.4m or 0.6 thick, 1.25 to 7.0m long, and 1.8 to 3.45m tall. It was found that retrofitting with steel meshes can enhance the lateral load capacity of earthen walls by as much as 190% and drift capacity by as much as 170% depending on the level axial load. Flanged/corner RE walls that failed under the design-level earthquake were able to sustain much larger levels of excitation when retrofitted with steel meshes although exhibiting excessive residual drifts. Retrofitting with steel plates increased the in-plane shear strength of adobe wall piers by 30% and enabled attaining drift ratios of up to 5% under out-of-plane cyclic loading. Steel plates also allowed corner RE walls to sustain base excitation well-above the design earthquake while maintaining residual drifts at tolerable levels. Using timber straps and vertical posttensioning was the most effective seismic retrofitting alternative evaluated in this research because the in-plane lateral resistance of earthen walls with openings increased by almost 80%, while the drift capacity increased by a factor of five, and the energy dissipation capacity increased by nearly an order of magnitude. Flanged RE walls retrofitted with timber sustained very large levels of base excitation with minimal permanent drifts .