A comparative study on nonlinear damping behaviors of precast and cast-in-situ recycled aggregate concrete frames

It has been well accepted that applying recycled aggregate concrete (RAC) into structural engineering is a sustainable method to solve the problem of construction and building waste (CDW) accumulation meanwhile to save natural resources exploitation. Precast RAC members in factories is beneficial to improve their qualities and will extend the RAC application. This study presents nonlinear damping behaviors of precast and cast-in-situ RAC frames after simulated earthquakes, as a reference of quality control of precast RAC members, and of damage detection under ambient vibration. The nonlinear damping of precast RAC slabs with different damage degrees was studied to validate the feasibility of applying the quadratic damping coefficient as a sensitive damage factor without any requirement of undamaged baseline. Meanwhile a comparative study on nonlinear damping behaviors of a precast and a cast-in-situ RAC frames was conducted. Results highlight a change of nonlinear damping mechanism for both precast and cast-in-situ RAC frames from a viscous damping into a nonlinear damping. The precast RAC frame had a comparatively larger quadratic damping coefficient before and after earthquake hitting, indicating it had more severe initial damage and damage developed more significantly compared with the cast-in-situ frame. A unified damage classification was proposed for both precast and cast-in-situ RAC frames based on quadratic damping coefficient and observation.