Static and dynamic behaviour of a hybrid PFRP-aluminium space truss girder: Experimental and numerical study

A novel hybrid pultruded fiber reinforced polymer (FRP)-aluminum space truss system was proposed, aiming to be used as pedestrian bridge or platform in marine areas. A large-scale space truss girder substructure was assembled, and the full-scale static and dynamic tests were separately conducted. The girder's static behaviour was analysed using three-point bending test, and the girder shows satisfactory bending stiffness contributed by the structural form of space truss. To reveal the girder's dynamic properties, the output-only modal identification method was used. Some unfavorable dynamic properties such as low natural frequency and the torsion mode as the first order mode shape were observed, which is mainly caused by the unique material properties and structural form. Thereafter, a strategy of adding diagonal bracing at the bottom chord plane to improve dynamic performance was proposed. To accurately predicting the static and dynamic properties, the fine line elements (FLE) model simulating all components' stiffness of the truss member were built. The simple-link-system (SLS) model was used for comparison. Based on FLE model, parametric analysis was conducted to reveal influences of key parameters. Finally, an efficient design strategy was proposed for this novel hybrid system with combined use of SLS and FLE model.