Abutment reactions and higher modes of transverse vibration of continuous bridges

The paper discusses the problem of predicting abutment reactions of continuous bridges through a simplified method of analysis based on the response spectrum method. The feasibility of substituting the real discrete support system with a continuous (Winkler) spring system is discussed. Limitations of this approach are evaluated by comparing the approximate solution with the theoretical correct one, which is evaluated through numerical finite element model analysis. Both linear and nonlinear system response is addressed. The comparison shows that the Winkler simplification is good in case of sufficiently small intermediate support stiffness (e.g. in case of deck isolation) and/or large number of spans. However, there will always be an upper bound to the intermediate support stiffness beyond which the error linked to the Winkler model will start to increase significantly becoming unacceptably large.