Numerical approaches for cross-laminated timber roof structure optimization in seismic retrofitting of a historical masonry church

In recent earthquakes, historical masonry churches have demonstrated to be vulnerable structures. Strengthening interventions based on the introduction of a roof diaphragm can be considered a valid solution in order to obtain a box-behaviour of this kind of structures. Among the possible different roof-diaphragm solutions, the wooden based ones represent an effective alternative, satisfying the conservation requirements in terms of material compatibility and reversibility, together with a significant improvement of the structural behaviour. After a short literature review of all the wooden based strengthening interventions, the possibility to consider cross-laminated timber (CLT) as a roof-diaphragm strengthening for existing churches is discussed in this paper. The effectiveness of this retrofitting solution is inquired numerically by means of different kind of linear and nonlinear analysis, focusing on the role played by the steel connections among the different CLT panels. The Basilica of Collemaggio has been chosen as case study to test the possibility to apply CLT roof diaphragm on an existing masonry church, adopting different modelling approaches. A short discussion on the optimisation of the steel connection layout is also presented.