Ambient vibration based evaluation of a curved post- tensioned concrete box-girder bridge

Abstract

This paper describes ambient vibration based evaluation of a curved, post- tensioned, concrete, box-girder bridge, the Newmarket Viaduct. The procedure includes ambient vibration testing, system identification, finite element modelling and finite element model updating. Since the dynamic excitations were not measured in the ambient testing, two operational modal analysis methods, namely enhanced frequency domain decomposition and stochastic subspace identification, were applied to identify the experimental dynamic modal characteristics. A three dimensional finite element model of the bridge was created to determine the dynamic characteristics analytically. Analytical and experimental dynamic modal characteristic were compared with each other and the finite element model of the bridge was updated by changing the material properties and boundary conditions to reduce the differences between the experimental and analytical results. It is demonstrated that the proposed procedure can successfully identify the most significant modes of the bridge and the in-situ material properties and boundary conditions. Finite element (FE) analysis of important engineering structures such as highway bridges is now commonly performed in the design or reassessment process. With the advances in numerical modelling, the FE models are first built in the design phase based on technical design data, as built drawings, on-site geometry surveys and professional engineering knowledge to predict structural behaviour, both static and dynamic. However, material properties, boundary conditions and section properties accepted in the analysis are subject to inherent stochastic variability, can change as a result of construction errors and will deteriorate with time due to aging and damage. Therefore, the performance and structural behaviour of bridges in service have to be determined with the help of field testing or experimental measurements. The experimental results can later be used to check the