SEISMIC DESIGN OF MASONRY BUILDINGS:CURRENT PROCEDURES AND NEW PERSPECTIVES

摘要

The application of parametric linear and nonlinear analyses on regular structural configurations of masonry buildings has showed how the procedures of seismic safety checks based on linear analyses can lead to inconsistent results if the q-factor values recommended in some seismic codes (i.e. EC8) are used. The need for the consideration of an appropriate overstrength ratio (OSR) is demonstrated for masonry buildings. However,the choice of a single conservative value of OSR for a given building typology does not completely overcome the intrinsic limitations of a linear analysis, given the high variability of OSR from structure to structure. On the basis of comparison between the force distribution in linear and nonlinear analysis two simplified design linear procedures are proposed, solving the high variability of OSR. The first method is based on a traditional linear elastic analysis followed by a suitable redistribution of the internal forces (shear and bending moments). The second method is characterized by a preliminary estimation of the distribution of the internal forces based on the strength of the masonry piers. This estimation is evaluated trough the results of an elastic analysis. The safety checks are then carried out comparing the total base shear of the structure with the base shear strength. Both methods have shown to give good results in comparison with full nonlinear static procedures, when applied to regular building configurations. The second method can be very useful also as a simplified method to check the results of the nonlinear static analyses in terms of base shear-top displacement capacity curve.