Dynamic behavior of masonry structures under pyroclastic flows

抄録

Pyroclastic flow is a dangerous hazard for people and houses so buildings have to provide a measure of protection to the occupants. In order to improve the structural strength of buildings, we need to know the structural behavior against the lateral pressure of the flow. In this study, dynamic behavior of unreinforced masonry structures affected by pyroclastic flows was analyzed using 2-dimensional (2D) Distinct Element Methods (DEM). DEM is a numerical analysis technique, in which the positions of elements are calculated by systematically solving equations. The structure is modeled as an assembly of distinct elements connected by virtual springs and dashpots where elements come into contact. Masonry structures with simple structural elements; walls, floors, a roof, and furniture were modeled. The strength of mortar was varied to check the effect of pyroclastic flow on the structural behavior under different conditions. Pressure acting on a wall due to pyroclastic flow was modeled as a simple time function of which the peak value was varied from 0.1 MPa to 10 MPa. A pressure model of which intensity changes with height was also treated. Tilting, lateral movement, collapse and swept away within several seconds are the typical collapse process of a weak masonry structure even when the lateral pressure is 1 KPa. The collapse of the masonry structure is controlled by the relation between the overturning moment due to the lateral pressure and the resistant moments due to gravity and mortar joint strength.