A Seismic Assessment Procedure for Historic Structures

The majority of the world’s population live in “vernacular” buildings, often dismissed as unengineered structures, built in distinct local styles using local materials and structural techniques. The collapse of these buildings has been blamed for a large number of deaths in recent earthquakes, leading to appeals for their demolition or strengthening. However, many are of high historical and cultural significance. Furthermore, their seismic behaviour is often poorly understood, and well-intentioned interventions may adversely affect their performance unless properly verified by a robust seismic assessment. Current evaluation procedures are not appropriate for these buildings as they do not emphasise compliance with conservation principles, nor consider unique structural techniques and materials. This thesis aims to develop a novel decision-tree-based diagnostic approach for the seismic assessment of historic vernacular buildings. The diagnosis is performed in two stages; a preliminary diagnosis based on onsite observations and archival research, and a detailed, more quantitative diagnosis based on numerical analysis and experimental testing. At each stage, four parameters are assessed; the initial structural concept, the interaction between components, the quality of connections, and the quality of the structural fabric. The procedure aims to be applicable to any class of vernacular buildings with minimal modifications. The approach has been validated by application to two historic residential buildings in Peru with different structural systems. To arrive at a diagnosis, experimental tests have been performed, and detailed finite element models developed at global and local level, which are shown to adequately represent the lateral response of the system. A specific focus is made on the characterisation of quincha, a technique consisting of a timber frame infilled with a weave of canes and mud. The procedure is applicable to both building types, with only minor modifications, and has proven to be a valuable tool for identifying vulnerabilities of the building