The prototype building consists of a three-dimensional two-story one-bay square-plan RC frame. The frame is provided with masonry infill walls and plasterboard walls along the two main directions (X and Y, respectively), and tested on two base isolation systems. The prototype was mounted on four FREIs (RP-FREIs first, then VC-FREIs) installed in unbonded configuration beneath the corner columns. The replacement of the base isolation is executed through proper uplift at the foundation level.

With regard to the bearings’ characteristics, the VC-FREI system consists of alternated layers of virgin rubber and quadriaxial carbon fabric and is characterized by higher compression modulus when compared to RP-FREI, where biaxial polyester fabric is adopted. Due to different fabric thickness the two isolators measured different heights, namely 80 mm and 95 mm for RP-FREI and VC-FREI, respectively.

Even if previous tests demonstrated that rubber-concrete friction would prevent any sliding of the isolators, a recessed configuration (e.g. two additional steel plates for each bearing installed beneath the base beam and above the table with a central hole having the bearing diameter) was adopted for VC-FREIs to comply with EN15129 fixing methods for transmission of lateral force. For ease of installation and further reduction in construction cost, no recess was provided to the RP-FREIs to assess the adequacy of a friction-only restraint for the isolators.

The RC frame was designed as a non-dissipative structure according to EN 1992-1-1 and EN 1998-1 to be more representative of existing buildings. It has plan dimensions of 4.0m x 4.0m and a story height of 2.7m. The class of concrete is of medium compressive strength (C30/37). The columns have square sections of 35cm x 35cm and are reinforced with A500 steel rebars. The beams’ cross section is 30cm x 40cm in size, whereas the slab is 12cm-thick and is reinforced with a double-layer welded wire mesh. The total weight of the 2-story infilled frame is close to 40t including the foundation beam and nonstructural components. Foundation beams at the base (with 35cm x 60cm section) provided adequate stiffness under horizontal excitation as well as vertical stiffness under lifting and handling operations. The frame had no special foundation since it rests on four FREIs transferring horizontal force by friction. In this regard, a concrete-filled plate was installed on the shaking table providing realistic friction conditions of rubber-concrete type. Two different infill systems were tested along the two horizontal directions. In one direction (X), a single-leaf, around 20-cm thick, hollow-clay brick wall was considered, which is very common in Europe also for its thermal insulation properties. Hollow clay bricks with vertical and horizontal holes were adopted for the first and the second story, respectively. In the other direction (Y), a plasterboard partition system was installed as a lower-weight and more versatile internal partition alternative. The infills have been tested both in-plane and out-of-plane due to the biaxial horizontal excitation. Nonstructural components were installed at the second story of the building, consisting in common housing and office contents, including a closet, a desk with a computer, a lamp and a suspended pipe.