Sensitivity analysis of geometric irregular effects on vulnerability of large-hall historic structures. (September 2020) - Boscato, G.
Highlights: Structural vulnerability triggered by the geometric irregularity of churches. Loss of box-like behaviour of church and response by macro-elements. Finite Element Analysis of church in linear and non-linear field. Structural performance analysis of the main macro-elements. Abstract: The present research aims to analyse the vulnerability triggered by the irregularity in plan and elevation of the large-hall historic structures. A meaningful case San Pietro di Coppito church in L'Aquila, seriously damaged by the 2009 earthquake, is proposed as example. The presence of annexes, of transformed volumes, of incomplete structures generate asymmetries that cause eccentricities of the masses and/or of the stiffnesses that condition the global box-like behaviour and generate the response by macro-elements. The vulnerability of irregular large-hall structures increases with the ineffective horizontal stiffening. Through the visual survey of the damage and from the experimental investigations conducted at global level through the dynamic identification it was possible to highlight the effects of this irregularity on the case study hit by the earthquake. The Finite Element model has been built based on experimental data; starting from this reference model several numerical models were built and analysed, in the linear field through the modal and spectral analysis and in the non-linear field by pushover analysis, considering the geometric regularization process related to different stiffening effects of roof. Nine numerical models have been compared considering three geometric configurations - actual, irregular without bell tower and regular - combined with three constrain conditions of roof, fixed, free and partially constrained. The behaviour of the main macro-elements, façade, walls of nave, transept, choir, apse and bell tower has been considered through the sensitivity analysis of dynamic parameters; in detail, the variation of frequency values, the participation mass and displacements of related mode shapes have been evaluated for every configuration. The non-linear static analysis has been carried out to assess the structural capacity of different numerical models.