A brace-type seismic damper based on yielding the walls of hollow structural sections

This paper proposes a new brace-type seismic damper designed for earthquake protection of structures. It consists of a tube-in-tube assemblage of two commonly available hollow structural sections. The outer hollow section of the Tube-in-Tube Damper (TTD) has a series of strips created by cutting a series of slits though the wall, and it is welded to the inner hollow section in such a way that when the brace damper is subjected to forced displacements in the direction of its axis, the strips dissipate energy through flexural/shear yielding. In comparison with other existing brace-type dampers such as the popular buckling restrained brace, the TTD has the advantages of being much simpler–thus entailing a lower cost–and the yielding part of the damper can be easily inspected after an earthquake. The performance of the proposed damper was assessed experimentally by an initial series of four cyclic tests, and compared with that of conventional steel plates with slits in another series of five tests. The experimental results show that the damper possesses very stable hysteric characteristics and excellent energy dissipation capacity, both similar to the conventional steel plates with slits already in use for seismic applications. Based on the test results, a hysteric model and a procedure for predicting the ultimate energy dissipation capacity and failure of the new damper are proposed.