11.60: Experimental investigation under cyclic loadings of an innovative passive mitigation device

Abstract

The present study focuses on the experimental investigation of an innovative passive mitigation steel device, mentioned as CAR1. It consists of three distinguished parts; the external cylindrical ring, the internal prismatic holder and several superimposed blades that are responsible for the transfer of forces between the aforementioned 2 parts. CAR1 is utilized for strengthening either existing or new steel and R/C structures. The behaviour of the innovative device is changing according to the developed levels of displacement. It is designed so that it can be locked at a preselected level of displacement, thus, offering an extra safety reserve against strong earthquakes. By using CAR1, the beam-column frames can be easily and safely strengthened at many predefined levels according to the desire of the designer. The mechanism of the energy absorption is developed on the superimposed blades through both yielding of steel and friction. The number and dimensions of the superimposed blades, their elastoplastic properties as well as the friction coefficient at their interface, define the equivalent nonlinear constitutive law of CAR1. A full-scale device was fabricated and experimentally investigated under cyclic loading. The experimental sequences were conducted at the premises of Laboratory for Strength of Materials and Structures of Aristotle University of Thessaloniki. The investigated variables are the geometry of the blades, the rate and number of the cycles of the loading sequence. The obtained results depicted the overall behaviour of CAR1 with respect to the absorbed seismic energy, and whether or not it will break during the cycle loading. Each experimental sequence imposed more than 50 cycles on the investigated specimen, with a different target load and rate each and every time. The results showed that CAR1 is an alternative device for mitigating the energy developed to a structure during an earthquake.