Seismic testing of large scale structures with dissipator devices

Abstract

Seismic testing of large-size models is nowadays possible thanks to the pseudodynamic (PsD) method, which resembles a quasi-static method with the application of slowly varying forces to the test structure. Low testing velocity may change the behaviour of the materials with respect to their behaviour at real velocity due to strain rate effect (SRE). The SRE during a PsD test is not relevant for the classical construction materials. However, it can be very important for some new materials, such as rubber or silicon, mostly used in isolators or energy dissipative devices. Silicone fluid viscous dampers are an example of these dissipative devices, and they will be the subject of this paper. It is possible to extend the PsD method range of application to structures equipped with dissipative devices by introducing a correction technique (CT) developed by the European Laboratory for Structural Assessment (European Commission) in Ispra, Italy. This technique consists of an on-line linear modification of the restoring measured forces. In this paper, two new procedures of CT are proposed. The first procedure consists of a linear filter where the output is the corrected force and the inputs are the measured forces and displacements. The second procedure is based on neural networks, using the same input but adding the test velocity rate. First, the most appropriate scheme of the algorithms was selected and calibrated. This is based on experimental data obtained by dynamically testing the dissipation devices with a displacement pattern, which was specifically designed for this purpose, at different frequencies and test velocities. Then, the capability of the obtained filter/net is tested using experimental data. Additionally, the most appropriate frequency for the training tests was studied. Outcomes were successful. Both algorithms outperform the previous linear CT, the net-based one being the most accurate and versatile. It was found that the first natural frequency of the unprotected structure is an adequate reference for the training tests.