One-way shaking table test study of resilient steel frame with seismic isolated floor system

This paper presents a novel seismic isolation floor system that aims to address the issue of incongruent deformation between the floor and the resilient steel frame structure. The proposed study introduces a design methodology for the seismic isolation floor system, along with the consideration of its impact on the resilient beam-column nodes. Subsequently, a scaled-down test model is built and constructed, consisting of three stories with a height of 1.2 m and a 2 x 2 span configuration, in accordance with the aforementioned design methodology. The experimental study involved conducting unidirectional shaking table tests on the model in both horizontal directions. The scaled-down model was subjected to seismic excitations of varying intensities, ranging from an 8-degree multiple-occurrence earthquake to a 9-degree rare-occurrence earthquake. Additionally, an extremely rare-occurrence earthquake with an acceleration of 0.75 g was also applied to the model. The test results indicate that the beam-column node exhibits a maximum opening of 4.56 mm and an angle of rotation of 3.04%. Furthermore, the seismic isolation building system demonstrates the ability to accommodate the "expansion effect" of the resilient structure, while simultaneously maintaining load carrying capacity and effectively transmitting horizontal forces. The seismic isolation floor exhibits a notable reduction of 54.8% in its maximum horizontal inertia force, hence demonstrating a favourable damping effect. Based on the observed alterations in the X-direction frequency of the structure prior to and after to the seismic event with a PGA of 0.07 g, it can be inferred that the beam-column connections inside the structure may be deemed as stiff when subjected to several earthquakes. In the PGA = 0.75 g scenario, the maximum interstory displacement angle of 1/69 is observed in the X direction of the 2nd floor. This value is in close proximity to the elastic-plastic interstory displacement angle of 1/50. However, there is no visible deformation or damage to the structure as a whole, and the strain of each member remains within the elastic range, not exceeding 1675 mu epsilon. Hence, it is widely acknowledged that the resilient steel frame, equipped with a seismic isolation floor system, exhibits robust postearthquake functional resilience in the face of unidirectional seismic activity.