MACRO-ELEMENTS IDENTIFICATION ON HISTORIC CHAPELS: THE CASE OF ST. VENERIO CHAPEL IN REGGIOLO – EMILIA ROMAGNA

Masonry churches are effectively studied by means of kinematic analyses on macro-elements. This paper presents a procedure to recognize and evaluate the contribution to the dynamic response of such macro-elements by means of nonlinear transient analyses. In particular, it consists in evaluating damages occurred by applying accelerograms of the Emilia Romagna earthquake (Italy, 2012) to a small church characterized by a complex damage pattern. First, a modal analysis furnished qualitative information about vulnerable macro-elements of the chapel, stressing the high vulnerability of the central vault, actually collapsed, and that of the façade, subjected by an incipient overturning and in plane mechanism. Afterwards, a more sophisticated approach was performed, considering the nonlinear behavior of masonry, capable to evaluate the damage evolution or the degradation of elastic stiffness. The density of energy dissipated by damages for each macro-element was computed for three sets of natural accelerograms, applied in transient analysis. The rates of dissipated energy densi-ties with respect to the total dissipated energy helped to identify the macro-elements subjected to more severe damages. Such structural elements were demonstrated to be effectively the most damaged under the considered main shock. A similar procedure can be applied in a preventive perspective to judge the critical parts of a church or a historic building, upon a correct evaluation of the post-elastic behavior of masonry and a proper choice of acceleration time-histories