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Seismic retrofit of buildings with backbone dampers

Shaban, Nefize
Ozdemir, Seda
Caner, Alp
Akyüz, Uğurhan
Dampers have been effectively used in new designs and seismic retrofit of old structures in many parts of the world. The common seismic retrofit practice in Turkey is almost purely based on stiffening the structure with additional shear walls or adding braces to limit the excessive seismic drifts. Such an approach usually results in expensive interior works and enlargements of foundations. The stiffening of the structure typically results in attracting more seismic force. Utilization of dampers as seismic protection devices have not been so much popular in Turkey and have been considered to be used only in some few retrofits. However, use of seismic protection devices can significantly improve the structural response and reuse of the structure after the earthquake. A new type of damper system called backbone damper has been recently developed and tested at the laboratories of METU. The results of more than 1000 tests indicated that the response of backbone damper is stable under the same conditions and more than 20% damping can be achieved at story drifts of 10-20 mm of movements. The harmonic motion test speeds reached up to 400 mm/sec in some cases and a maximum frequency of 7 Hz is achieved during some tests. It shall be noted that the backbone damper has an internal displacement amplifier that helps the system to damp even at small movements. The dampers do not get damage at the end of tests and has the ability to re-center themselves. The solid model of the damper has been prepared using the ABAQUS software. The focus of the paper will be given to application of this new damper system to improve the seismic response of the existing structures. In this scope, one typical hospital building with different selection of damper performance has been investigated in the case study. Three ground motions have been applied to the structures with and without dampers. The ground motion records are scaled to have a equivalent design response spectrum curve. The results of non-linear time history analysis performed in LARSA 4D have indicated that the seismic response of the structures can be improved significantly in terms of displacments.