| Popis: |
Seismic isolation is one of the most effective methods of reducing earthquake-induced damage to buildings. However, the associated high cost makes this technology non-applicable in residential structures in the developing world. This paper presents an experimental study of low-cost spherical isolators, aiming to be used in residential masonry buildings in low-income countries. The isolators could be placed below the masonry walls to support the gravity load of the structure, eliminating the need for a heavily-reinforced concrete slab at the isolation level. The examined system is made of mortar-filled used tennis balls rolling on concave or flat concrete surfaces. The experimental investigation comprised compressive and cyclic tests of these systems. Parameters of investigation were the geometry of the rolling surface (i.e., flat or concave) and the applied vertical load (i.e., supported weight). Initially, the compressive behavior of the isolators was investigated. Subsequently, cyclic tests were performed to characterize the lateral force-displacement response of the various configurations. The experimental results proved the efficiency of the proposed system. The high compressive strength showed that the isolators could support the gravity load of a low-rise building. The lateral cyclic loops had a bilinear form when concave plates were used. In all configurations, the rolling friction coefficient (defined as the ratio of lateral to vertical force at zero displacement) was in the range of 4.7–7.2%, hence, suitable for seismic isolation applications. Special care should be given to the casting procedure since imperfections may affect the cyclic response of the system. |
