Numerical study on the reduction of the seismic vulnerability of historical industrial buildings with wide timber roofs

摘要

In the paper are presented the results of a preliminary numerical study concerning the evaluation of the effectiveness of interventions for the reduction of the seismic vulnerability of buildings with traditional multiple sloping timber roofs laid on masonry walls along the building perimeter and on columns internally. In particular, the effects of three different strengthening strategies are analyzed: the bracing of the roof diaphragm by means of wooden-based nailed panels, the addition of steel portal frames and the reinforcement of the masonry through the application of a mortar coating with composite meshes embedded. To take into account the different interventions effects, a simplified numerical procedure, based on non-linear-static analysis, is proposed and a case study is analyzed numerically to compare, in terms of resistant ground acceleration, a_(g,res), the effects of the different reinforcement techniques. Typically, the absence of the roof diaphragm determines the out-of-plane collapse of the longitudinal walls, for very low seismic actions. The roof stiffening induces a redistribution of the seismic load from the longitudinal walls to the transversal ones; however, as they are not dimensioned for horizontal loads, very modest benefits emerged in terms of a_(g,res). The addition of two steel portal frames or the reinforcement of the walls with the reinforced mortar technique permits to reach values of the resistant acceleration considerably higher than that of the unreinforced configuration (1.91 and 2.73 times higher, respectively).