*Article* **Study on Dynamic Behavior of Bridge Pier by Impact Load Test Considering Scour**

**Myungjae Lee 1 , Mintaek Yoo 1 , Hyun-Seok Jung 2 , Ki Hyun Kim <sup>1</sup> and Il-Wha Lee 2, \***


Received: 10 August 2020; Accepted: 24 September 2020; Published: 26 September 2020

**Abstract:** In this study, for the establishment of a safety evaluation method, non-destructive tests were performed by developing a full-scale model pier and simulating scour on the ground adjacent to a field pier. The surcharge load (0–250 kN) was applied to the full-scale model pier to analyze the load's effect on the stability. For analyzing the pier's behavior according to the impact direction, an impact was applied in the bridge axis direction, pier length direction, and pier's outside direction. The impact height corresponded to the top of the pier. A 1-m deep scour was simulated along one side of the ground, which was adjacent to the pier foundation. The acceleration was measured using accelerometers when an impact was applied. The natural frequency, according to the impact direction and surcharge load, was calculated using a fast Fourier transform (FFT). In addition, the first mode (vibratory), second mode (vibratory), and third modes (torsion) were analyzed according to the pier behavior using the phase difference, and the effect of the scour occurrence on the natural frequency was analyzed. The first mode was most affected by the surcharge load and scour. The stability of the pier can be determined using the second mode, and the direction of the scour can be determined using the third mode.

**Keywords:** prototype abutment; non-destructive test; surcharge load; mode number; scour
