| In 2006, a consulting firm was hired to perform an in-depth interior box inspection on Delaware Department of Transportation (DelDOT) Bridge Number 1-501, also known as the Newport Viaduct. Upon inspection, 655 fatigue cracks were observed, occurring at the weld metal between the transverse cross frame connection plate and girder webs. At the cracked locations, a 2.5 in. web gap exists between the connection plate termination and the girder flanges. This is a known fatigue prone detail that has been widely documented to be susceptible to out-of-plane deformation and distortion-induced fatigue.;Although the mode of cracking is relatively familiar, there are remaining questions that should be answered to ensure the proper functioning of the structure. Specifically, is the observed fatigue cracking consistent with expected behavior? Secondly, should additional cracks be expected to initiate in locations that currently do not have observable cracks?;These questions were approached by focusing on a portion of the overall structure, Spans 9-11 in the southbound direction. Field testing was performed to capture the in-situ response of the structure to known live loads via the implementation of 23 strategically placed strain transducers. The field testing was used to calibrate and validate a finite element model. The finite element mesh was constructed using the FEMAP preprocessor and solved using ABAQUS. Sensitivity analyses were performed on the model to investigate the influence of the transverse truck position within the travel lane, the concrete deck stiffness, and the concrete parapets. The results of each analysis showed that the finite element model was insensitive to variations in transverse truck position, concrete stiffness, and the exclusion of the parapets. The finite element model was ultimately utilized to perform a fatigue evaluation.;The fatigue evaluation showed that fatigue cracking is within reason given the stress range and the number of accumulated stress cycles from lifetime truck traffic on the structure. The fatigue evaluation and anticipation of future cracking establishes the need for developing crack retrofit and mitigation strategies for the web gap details within the structure. These strategies will extend the longevity of the bridge and enable it to remain in service. |
