Title:

Local condition assessment and damage detection of gusset-less connections used in a vertical lift truss bridge

Detailed modeling of a complex connection is time demanding and CPU intensive while simplified modeling of connection zones can lead to an inaccurate performance prediction. Therefore, a preliminary simplified structural model can be validated through a model updating procedure, based on optimization algorithms and field-collected structural response data to update relevant structural parameters. An innovative gusset-less connection is used in the Memorial Bridge superstructure, a vertical lift bridge in Portsmouth, NH. For fabrication of the connection, the common gusset plates were eliminated, and the truss chords are joined by an integral knuckle connection. In this paper, the effects of structural damage on the dynamic properties and structural behavior of this connection are studied based on a modal parameter extraction procedure. A simplified beam model of the connection is built in SAP2000® which is accompanied by a detailed solid model developed in Abaqus®. The detailed solid model of the connection is used for simulating various types of connection damage that may not be captured by the beam model, including weld defects or fatigue cracks. The output of the solid model would represent the modal properties of the damaged connection that can be used as the input information for a condition assessment program which makes appropriate changes to the beam model based on a model updating procedure through the SAP2000® OAPI. Then, based on the updated parameters, a stiffness reduction protocol could be established for the beam model of the damage considered for the gusset-less connection.

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