Vibration testing of an in situ bridge pier to determine soil-structure interaction effects

The lateral dynamic response characteristics of a single span from the decommissioned Puhinui Stream Bridge in Manukau, New Zealand were determined through a series of forced vibration tests performed along the longitudinal axis of the bridge using an eccentric mass shaker. Following forced vibration testing, the dynamic characteristics of a three column pier group from the span were determined using snapback testing. Responses of the bridge span and pier group measured during the vibration testing were used to construct finite element models accounting for soil-structure interaction using a Winkler spring idealisation of the soil. Because of the simplified nature of the pier group, it was modelled first, and used to perform sensitivity analyses to obtain realistic bounds for soil and material properties based upon CPT data and concrete specifications. The pier group model will be extended to capture the response measured by the forced vibration testing of the bridge span but is not discussed here.