Laser scan-based structural assessment of wrought iron bridges: Guinness Bridge, Ireland

Abstract

This paper introduces a workflow to create the geometric documents for conducting the finite-element-based structural assessment of wrought iron bridges using laser scanning data as the input dataset. First, a methodology for identifying actual cross-sections of the bridge components based on a point cloud obtained from a terrestrial laser scanner (TLS) is presented. Next, a non-parametric regression kernel density estimation is employed to determine overall bridge dimensions to populate a computational model by projecting the position of the web and/or flange surface of the cross-section (appearing as local maximum peaks of a probability density shape). The process is demonstrated with respect to the previously undocumented Guinness Bridge in Dublin, Ireland, to determine the bridge's behaviour. The successful generation of this model proves that TLS can surpass other common techniques (e.g. unmanned aerial vehicle-based images) for acquiring the bridge geometry necessary for reconstructing accurate member cross-sections and overall bridge dimensions, regarding the quantity and quality of the data points, and timing. The finite-element analysis showed that the bridge currently satisfies both strength and serviceability requirements under self-weight but would be unlikely to support a new slab and a modern pedestrian load level as per current code requirements for reopening the bridge.