بهسازی لرزه‌ای اسکله‌های شمع و عرشه به وسیله جداگرهای لرزه‌ای

There are significant number of pile supported wharves around the world and this type of structures are commonly chosen for the construction of new waterfront port facilities. Batter piles have been used for a long time to resist large lateral loads from winds, water waves, impacts and earthquake. Their distinct advantage over vertical piles is that they transmit the applied lateral loads partly in axial compression and tension, rather than only through shear and bending. Thus, batter piles offer larger stiffness and bearing capacity compared to vertical piles with the same diameter and depth. However, batter piles have been extensively damaged at several ports worldwide during past earthquakes. This paper is focused on the application of seismic isolation devices for improving seismic performance of existing pile supported wharves with battered piles. To assess efficiency of this method, a structure with batter piles was selected to represent typical seismically vulnerable pile supported structures. The selected structure is analyzed using dynamic time history analysis taking into account the nonlinear behavior of structure components and soil–pile-structure interaction effects. 2D models of structure and soil are developed using OPENSEES platform. The soil is modeled using nonlinear elasto plastic elements and the soil pile structure interaction behavior is modeled using p-y, t-z and Q-z nonlinear spring elements. Models that include axial load effects in lead rubber bearing (LRB) isolator behavior are used. Time history analyses for 475 and 2475 years level have been carried out for existing and retrofitted structures. The structures retrofitted by seismic isolators had longer period of vibration and increased damping both of which reduced the seismic base shear, axial force of battered piles for tension and compression and also moment and shear action in deck.