Plastic collapse mechanism of seismic assessment for existing RC bridges with flexible foundation and bearing pads

The deformations of reinforcement concrete bridge piers were divided into three parts, elastic deformation caused by a unit horizontal force at the top of the bridge piers, the rotation deformation and foundation translation deformation. A plastic collapse mechanism analysis mode of seismic assessment for existing reinforcement concrete bridges with flexible foundation and bearing pads was developed. Its analysis procedures and formulas with respect to the effect of elastic ground and elastic bearings were newly derived, and the practical analysis approaches of bilinear stiffness of bridge piers were given. An improved analysis method of seismic assessment for reinforcement concrete bridges was derived from equivalent elastic response acceleration at the limit state by considering the variety of the structural displacement ductility capacity caused by flexible foundation and bearing pads. An example shows that the structural displacement ductility capacity of reinforcement concrete bridges and seismic capacity are apparently reduced owing to considering flexible foundation and bearing pads.