Static and dynamic performance of a steel-concrete composite bridge

Continuous advances in bridge engineering often result in design of elegant, long-span and lightweight structural forms that fully exploit complementary mechanical properties of steel and concrete materials. These composite steel-concrete structures often possess large span-to-depth ratio that might lead to increased sensitivity to dynamic actions, such as wind and human-induced excitation. To ensure satisfactory performance of these structures against dynamic loading, reliable modes are required. In addition, due to creep and shrinkage of concrete, a reliable evaluation of time-dependent deformation development under long-term static loading is required. This paper describes an analysis of static and dynamic performance of a slender steel-concrete composite bridge situated in the Structures Laboratory at the University of Warwick. The 19.9m long bridge has a high slenderness ratio of 45, and a fundamental vibration mode having natural frequency of 2.5Hz. The static and dynamic behaviour of the bridge has been monitored for a year. Key experimental data are presented in this paper. A number of finite element models are developed in Abaqus software and evaluated against the test data. It was found that detailed modelling of the boundary conditions is crucial for successful prediction of the dynamic properties. Creep and shrinkage effects caused large deformation which could not be captured by the model developed. Therefore, a more sophisticated modelling approach and further studies are necessary to improve modelling of long-term static effects. Subjective vibration assessment concluded that the bridge is serviceable for short vibration exposure, while long exposure in walking posture resulted in increased vibration levels and probability of complaints.