Strength capacity of a No-Tension portal arch-frame under combined seismic and ash loads

In some previous papers the seismic response of a simple structural system has been studied, namely a masonry arch portal [Baratta et al. (1996) Seismic Risk of Historic Centres], modelled by the classical rules of mono-dimensional structures, and complex structural systems made of combinations of several elementary arch portals. In this paper, the seismic response of a simple masonry arch portal under the combined action of horizontal seismic forces and vertical overload due to volcanic ash fall subsequent to an eruption is discussed. Decay of the collapse coefficient of the horizontal load is evaluated for ash fall load increasing.