Numerical and Experimental Efficiency Assessment of Energy Dissipators for the Seismic Protection of Buildings

The present study is intended to assess the efficacy of energy dissipators in the seismic protection of buildings. It has been divided in two parts: 1) a numerical analysis and 2) an experimental study. The numerical analysis is a 2-D study on the nonlinear seismic response of buildings equipped with two types of energy dissipators: Constant Friction Slip Braces (CFSB) and Adding Damping and Stiffness (ADAS). Three types of reinforced concrete buildings with 3, 7 and 15 stories are considered. Dissipators are placed in steel diagonal braces in all the floors. Two different criteria for selecting the sliding threshold (or yielding) forces for each mechanism are considered. The input consists of ten recorded earthquakes corresponding to medium and stiff local soil conditions. Average values on the ten registers are given for the maximum horizontal displacement, base shear, energy dissipated and interstory drift. Analyses of the structures directly built on a common ground have also been performed. The ground is composed of seven different layers with different thickness. In this case the response has been calculated only for CFSB and ADAS with a sliding threshold (or yielding) forces selected as the maximum ones obtained from UBC-91 code (F-y = 100%). The buildings have been subjected to two earthquake registers; the inputs have been filtered by the ground. In the experimental study a series of shaking-table tests have been performed on a steel model passively protected with simple friction dissipators. Based on these numerical analyses and dynamic tests it appears that energy dissipators provide an effective and reliable method for seismic resistant design. The conclusions are expected to provide simple design guidelines.