PSI - Issue 64

Ge-Wei Chen et al. / Procedia Structural Integrity 64 (2024) 724–731 Ge-Wei Chen, Xinghua Chen, Piotr Omenzetter / Structural Integrity Procedia 00 (2019) 000–000

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heights between 4.27 m and 14.43 m and the maximum width and thickness of 2.85 m and 1.42 m, respectively. The ends of the bridge are supported by a pile-bent type abutment and a gravity abutment, referred to as Abutment 1 and Abutment 2, respectively. The abutments and piers are founded on piles or footing type-foundations. A pair of fixed type elastomeric bearings were installed at the top of each pier and Abutment 2 to support the superstructure, whereas at Abutment 1, sliding type bearings were used. Shear keys were also installed at the top of Piers 2–10 to provide additional resistance for the superstructure during strong seismic events. Finally, a hinge in the girder is located between Piers 4 and 5 and this is also where the depth of the box section changes gradually between 1.73 m and 1.09 m. The bridge was modelled using the ANSYS finite element package to help in experiment planning (determination of excitation frequency range and shaker locations) and for comparing the performance of the various system identification methods employed. The concrete box-girder was modelled using the 4-node 3D shell elements (SHELL 63), and a second set of 4-node shell elements were added for the asphalt pavement. Piers, steel rails and concrete water channel were modelled by 2-node 3D beam elements (BEAM188). The fixed-pot bearings were modelled by coupling the translational degrees of freedom between the piers and Abutment 2 and the respective girders but allowing unrestrained rotations. The sliding type bearings were translationally unrestrained in the direction of sliding. The hinge was modelled by a 3D pin joint COMBIN7 element with all translations fully constrained and all rotations free. The shear keys between the piers and girder were assumed to remain unengaged for the small displacements induced during the tests and so needed not be modelled. Because of the large stiffness of the foundations, the piers were modelled as fully fixed at the base, i.e., soil flexibility was ignored. In numbers, the FEM had 58,665 nodes and 66,064 elements.

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Fig. 1. Nelson St. off-ramp bridge: (a) aerial photograph; (b) structural arrangement and locations of exciters (all dimensions in m).