Conclusions
Historic earthen structures are a significant portion of the built heritage worldwide, with similarly identified structural characteristics and performance levels. In areas with high seismic hazard and in the absence of bracing and buttressing, these structures are usually characterized by structural discontinuities, low lateral capacity, and potent fragmentations in corner junctions. Given their low mechanical properties, usual lack of maintenance and structural alterations, historic earthen structures are bound to perform inadequately in strong earthquakes, in the absence of corrective measures.
Based on recommendations from national building codes, conservation principles and local practices, traditional strengthening techniques can improve the integrity of earthen structures, increase the out-ofplane capacity and redistribute seismic loads between transversal and longitudinal walls, ensuring the so called “integral behaviour”. Commonly used, traditional strengthening techniques involve the use of buttresses, together with systems of timber strengthening elements, such as bond beams, anchors, corner keys, and tie beams.
Under the Seismic Retrofitting Project of the Getty Conservation Institute, extensive inspections, surveys, in-situ and laboratory testing, and nonlinear structural analyses of earthen historic structures assessed the current state revealing structural deficiencies. For two case studies, the Church of Kuño Tambo and Ica Cathedral, a complete design and assessment of the above-mentioned strengthening solutions have been carried out, and the project methodology and the resulting retrofitting techniques are currently being disseminated for local practitioners in Peru. The strengthening proposal was developed by a multidisciplinary team, involving national and international engineers, architects, and cultural heritage authorities. For the retrofitted structures, performance criteria and seismic local demands were met, with sufficient safety and acceptable levels of repairable damage. Furthermore, energy dissipation under lateral loading increased and a better redistribution of seismic loads between transverse and longitudinal walls was achieved.
