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This paper aims to detect and locate damage in an innovative slab-on-girder pedestrian bridge model using the vibration characteristics determined from a combined experimental–numerical procedure. The innovative slab-girder pedestrian bridge model has a bi-layer composite deck with Glass Fiber Reinforced Polymer as the bottom layer and laminated glass as the top layer to exploit the desirable properties of these two materials. Modal data from experimental tests and numerical analyses of the bridge model under single and multiple damage cases together with the modal flexibility method are used to detect and locate damage in the bridge. Results show that the peaks of the model flexibility plots correctly locate the damage and that their values provide a good indication of damage severity, which depend on the number of damages, damaged member and location of damage. Results show that the early vibration modes of this bridge model are dominant in torsion, different to flexure dominant modes in traditional slab-girder bridges. Nevertheless, the combined experimental-numerical procedure is found to be effective for assessing both single and multiple damages in the innovative bridge model. The adopted procedure will be applicable to similar real bridge structures in future investigations and will contribute to their safety. [ABSTRACT FROM AUTHOR]

This paper proposes an innovative pedestrian arch bridge, with a new bi-layer composite deck supported by a steel frame. Bottom and top layers of the bridge deck are composed of glass fibre reinforced polymer (GFRP) plate and laminated glass plate respectively. Structural evaluation of this aesthetically pleasing and lightweight pedestrian bridges is important to avoid excessive vibration. With this in mind, free vibration tests were first carried out on the proposed composite deck and results were used to validate a three-dimensional finite element (FE) model of the composite deck developed in ABAQUS software. Static and free vibration responses of the proposed pedestrian arch bridge with steel frame and composite deck are evaluated by FE analyses. While the static performance of the bridge was found to be satisfactory, the fundamental natural frequency was found to be within human walking frequency which could cause excessive vibration. Hence, further analysis was carried out by changing the cross-sectional areas of the bridge parts to obtain the desired performance of the bridge. Results were compared with recommended values in Bridge Design Code and they ensured that the proposed pedestrian arch bridge will be a safe, aesthetically pleasing and serviceable structure for the pedestrians. [ABSTRACT FROM AUTHOR]

Damage identification for complex structures is a challenging task due to the large amount of structural elements, limited number of measured modes and uncertainties in referenced numerical models. This article presents a study on enhancing the effectiveness of modal characteristics correlation methods for damage identification of complex structures. First, a correlation method using change in the ratio of modal strain energy to eigenvalue is introduced. Damage information is determined via a forward approach by optimizing the correlation level between the patterns of the analytical and measured changes in the ratio of modal strain energy to eigenvalue. Different from traditional optimization-based forward methods that require accurate numerical models, damage sensitivity coefficients of the ratio of modal strain energy to eigenvalue are directly estimated from the experimental modal information. To enhance the damage identification capability, both the elemental modal strain energy–eigenvalue ratio and the total modal strain energy–eigenvalue ratio components are examined in the correlation function. Second, a sensitivity-weighted search space scheme incorporated with genetic algorithm is developed to overcome the ill-posed problem that causes false detection errors. Finally, the correlation method and the enhanced technique are experimentally tested on a complex truss model with nearly 100 elements. To deal with the huge number of degrees of freedom in this structure, a multi-layout roving test with the adoption of redundant channels is designed, and a three-criterion strategy is used for the selection of modes. Results demonstrate the effectiveness of the proposed damage assessment framework to locate and estimate damage in complex truss structures. [ABSTRACT FROM AUTHOR]