An innovative distributed base-isolation system for masonry buildings: the reinforced cut-wall

The article reports the results of experimental tests conducted on an innovative masonry-building seismic isolator, named "reinforced cut-wall". The system is simple to construct and inexpensive to implement, yet delivers high static performance. It is made up of a layer of low load-bearing capacity mortar and an underlying sheet of elastomer waterproofing interposed between the base of the walls and the foundation head and reinforced by a series of vertical steel rods anchored to both the wall and foundation by concrete castings. The experimental trials were conducted on pairs of cellular blocks, 20x20x50 cm, separated by a 5 cm-thick layer of mortar and 3mm elastomer sheathing; the rods used ranged from 8 to 12 mm in diameter. Such specimens were subjected to a constant vertical force, simulating the actions of permanent in-service loads, and a cyclic history of horizontal forces (max. 0.4 times the vertical load), representing an earthquake. Test results, expressed as a series of hysteresis diagrams, reveal a high degree of energy dissipation, attributable to the malt-elastomer joint, and efficient elastic recovery due to the reinforcing bars which also furnish suitable vertical load-bearing capacity. Numerical analyses, conducted by means of a rheological model calibrated with the help of the test results and applied to the case of a simple masonry building, have confirmed the high-level performance of the proposed seismic isolating system.