Condition assessment of bridges has become increasingly important.In order to accurately simulate the real bridge,finite element(FE) model updating method is often applied.This paper presents the calibration of the FE model of a reinforced concrete tied-arch bridge using Douglas-Reid method in combination with Rosenbrock optimization algorithm.Based on original drawings and topographic survey,a FE model of the investigated bridge is created.Eight global modes of vibration of the bridge are identified by ambient vibration tests and the frequency domain decomposition technique.Then,eight structural parameters are selected for FE model updating procedure through sensitivity analysis.Finally,the optimal structural parameters are identified using Rosenbrock optimization algorithm.Results show that although the identified parameters lead to a perfect agreement between approximate and measured natural frequencies,they may not be the optimal variables which minimize the differences between numerical and experimental modal data.However,a satisfied agreement between them is still presented.Hence,FE model updating based on Douglas-Reid method and Rosenbrock optimization algorithm could be used as an alternative to other complex updating procedures. Condition assessment of bridges has become increasingly important. In order to accurately simulate the real bridge, finite element (FE) model updating method is often applied. This paper presents the calibration of the FE model of a reinforced concrete tied-arch bridge using Douglas- Reid method in combination with Rosenbrock optimization algorithm. Based on original drawings and topographic survey, a FE model of the investigated bridge is created. Light global modes of vibration of the bridge are identified by ambient vibration tests and the frequency domain decomposition technique. Eight structural parameters are selected for FE model updating procedure through sensitivity analysis. Finally, the optimal structural parameters are identified using Rosenbrock optimization algorithm. Results show that although the identified parameters lead to a perfect agreement between approximate and measured natural frequencies, they may not be the optimal variables which minimize the differences between num erical and experimental modal data. Yet, a satisfied agreement between them is still presented .ence, FE model updating based on Douglas-Reid method and Rosenbrock optimization algorithm could be used as an alternative to other complex updating procedures.