| Abstract: | A structure moving under the influence of an earthquake is normally required to absorb its own energy of motion. However, in many cases it is possible to attach to the structure energy absorbing devices which absorb most of its energy of motion. One such device is an energy absorber which works by extruding lead back and forth through an orifice. On being extruded the deformed lead recrystallizes immediately, thereby recovering its original mechanical properties before the next extrusion or stroke. Accordingly, the amount of energy absorbed is not limited by work hardening or fatigue of the lead, but rather by the heat capacity of the device, the melting point of lead being the upper limit to the operating temperature. Furthermore, the device is able to absorb energy during a large number of earthquakes. A number of 20 kN × 2 cm stroke to 200 kN × 26 cm stroke extrusion energy absorbers have been tested at rates of 10?6 to 3.6 × 10?6 cm/min. They behaved as ‘plastic solids’ or ‘coulomb dampers’ with nearly rectangular hysteresis loops and little rate dependence. |
