Full-Scale Shake Table Tests of a RC Building with Fiber-Reinforced Elastomeric Isolators: ERIES-FREISUST

The ERIES-FREISUST project investigates the effectiveness of two unbonded fiber-reinforced elastomeric isolator (FREI) systems to enhance the seismic resilience of buildings: (1) a Virgin-rubber Carbon-fiber FREI (VC-FREI), and (2) a Reclaimed-rubber Polyester-fiber FREI (RP-FREI). VC-FREI installed in recessed configuration offers better standardization in terms of axial stiffness and material properties, while RP-FREI is a eco-friendlier and more cost-effective alternative, particularly suitable for developing countries due to its use of reclaimed rubber and polyester fabric.
The project focuses on the seismic performance of both structural and non-structural components of buildings subjected to increasing levels of horizontal and vertical ground motions. The FREISUST shake table testing program aims to validate FREIs as a sustainable, low-cost base isolation solution.
Tests were conducted at the National Laboratory for Civil Engineering (LNEC), Lisbon, Portugal, ST3D shake table on a 2-story full-scale reinforced concrete infilled frame specimen. Three configurations were tested: fixed-base, RP-FREI, and VC-FREI. Instrumentation included accelerometers at beam-column joints, infill walls, and non-structural components; displacement transducers at key structural interfaces, beam/column joints and non-structural components; optical transducers for global floor displacements.
Ground motion records from the 1994 Northridge (NORTHR/CCN), 1989 Loma Prieta (LOMAP/CYC), 1995 Kobe ('KOBE/NIS) and 1997 Jiashi (NWCHINA3/J411N) earthquakes were used as seismic inputs. These records were selected combining different intensity measures and scaled according to the target displacement of the FREIs and in accordance with shake table limits, with final scale factors larger than 1.0 and up to 150% of the original record. The testing protocol involved applying the ground motions with increasing nominal intensity in X, XY, and XYZ directions, interspersed with dynamic identification tests. Additionally, a sine-sweep excitation (0.1 Hz to 10 Hz) was applied along the X-axis to identify the resonance frequencies of the RP-FREI and VC-FREI configurations.
The base-isolation systems demonstrated lateral stability and re-centering capability, as well as adequate vertical stiffness and load-bearing capacity under different earthquake excitation conditions.