Mechanical Behavior of Simple masonry Buildings with low-cost Dissipators Distributed throughout the Basement

The design criteria and numerical results for a new low-cost base isolation technique for simple masonry buildings are presented. The proposed base isolator, named RCW –Reinforced Cut Wall-, is made up of a layer of weak mortar (50 mm) and an elastomer membrane sheath (4 mm) located between the foundation and the base of the bearing wall, which is reinforced by a series of vertical steel rods (8-10 or 12mm in diameter) connecting it to the foundation. A preliminary series of experimental trials have been performed on a sample set of isolators, during which specific tests have been conducted to check their mechanical properties and to define their assembly techniques. ANSYS 5.5.1. numerical simulations of the horizontal and vertical loads, consisting of non linear static incremental analysis, acting in several types of buildings (one, two or three stories high with rectangular floor plan) highlight the system’s efficient performance in terms of force-displacement law. For moderate horizontal actions, the mortar and elastomer layers of the RCW do not cause any relevant foundation-base displacement. Instead, when a prescribed limit is exceeded, the weak layers of the RCW permit large inelastic deformation due to friction behavior, while the vertical teel rods ensure an elastic restoring force that provides an elastic-plastic response of the base dissipator. Design possibilities for the RCW are illustrated, in order to optimize number and size of the steel reinforcing rods as a function of the magnitude of vertical loads and seismic actions. Moreover the RCW performs advantages in terms of feasibility and cost-effectiveness: the increase in construction costs with respect to a non-isolated building is very low, due to the same technology of simple masonry buildings, and provides further benefits in terms of isolation from ground humidity.