Performance of an underground structure seismic mitigation system improved by frictional deformation absorbing braces

Abstract

Earthquake-induced failure of underground structures attributes to their insufficient horizontal deformation capacity, which is mainly controlled by the horizontal deformation capacity of central columns. Therefore, the developed measures to update the seismic performance of underground structures are either to enhance the deformation capacity of central columns or to decrease seismic loads transmitted to columns. This paper presented an underground structure seismic mitigation system to reduce the earthquake-induced damage of underground structures by decreasing the horizontal deformation imposed on structures. In this system, frictional deformation absorbing braces are set between underground structure and earth retaining structure. The axial deformation of the braces is capable to decrease the earthquake-induced horizontal deformation of the overall structure. Furthermore, axial force of the braces can help the earth retaining structure to resist the earthquake-induced soil pressure. The deformation behaviour of the frictional deformation absorbing brace under axial loads was experimental firstly studied. Experimental results presented that the brace had a stable deformation property and could provide expected braced force. Then seismic response of the underground structure seismic mitigation system was simulated. Numerical results presented that the seismic behaviour of underground structure was sharply improved and the structure experienced very small damage even under strong earthquakes. Finally, the stiffness and strength of braces influencing the seismic performance of underground structure were discussed detailedly. The reasonable stiffness and strength of the braces for the target structure were suggested.