Condition assessment of concrete piers subjected to impact load using fiber optic sensing

A novel strategy for condition assessment of concrete piers subjected to impact load is presented in this article. The method of estimating residual displacement (lateral displacement and rotation angle) of concrete piers using long-gauge fiber optic sensing is firstly established. Theoretical derivation reveals that there exists linear relationship between the residual average strain and lateral displacement or rotation angle of the concrete piers. Then, a scaled concrete pier subjected to impact load was designed to verify the condition assessment strategy. The damages of the pier gradually increase by changing the impact velocity of the moving vehicle. Experimental results show that the residual average strain can well reflect the location and severity of random crack damages of the pier under impact load. Meanwhile, residual lateral displacement and rotation angel distribution along the specimen can be identified using the residual average strain measured by long-gauge fiber optic sensors. In addition, hammer excitation was also conducted on the pier after each impact in order to obtain structural dynamic properties. The extracted natural frequencies can reflect global performance (boundary condition and global stiffness) of the pier at each damage state. Therefore, the presented strategy could be a new alternative for condition assessment of concrete piers or columns in civil engineering.