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Monitoring, analiza numeryczna oraz ocena przyczyn uszkodzeń i koncepcja naprawy kratownicowego mostu autostradowego w USA

Podhorecki P.

Materiały Budowlane

2012

nr 7

4-10

The bridge is located on one of themost important of US interstate highways. It is steel thru-truss bridgewith two reinforced concrete slabs, two-level traffic,with lower and upper decks. The structure has 3 spans, all over the river channel and lengths around 107, 214 and 107 meters, respectively, total length of around 428 meters, with opening of around between 30 and 40 meters abovewater level. Superstructure is supported on four reinforced concrete piers on pile foundation. Central span is a suspended span (length of around 120 meters) hanged on two cantilever external spans (47 meters long on each side). The structure was built between 1968 and 1971. Ever since, during its service life was never fully retrofitted. Steel superstructure inspection in 1990 concluded that there are significant damages in both lower and upper level floorbeams (steel plate girders) connecting trusses near their fixed ends to trusses, following it inspections were more frequent, however, evaluation of technical condition and summary repairs were done after several years, between 2002 and 2006. These damages, out-of-plane and in-plane deformations and cracks, concentrated in top potions of webs and in top flanges. Repairs were made, however these works did not eliminate the reasons of damages and floorbeam failures. Finally in 2006, it was decided to perform complex damage investigation and develop retrofit design for the bridge superstructure. The study focused on development of numerical model of the bridge and finite element analysis, monitoring system was installed (including straingages, tiltmeters and thermocouples) and long-term monitoring was performed. Monitoring results were used to determine strains andmovements/deformations of steel structure due to live loads and temperature gradients and calibration of the numerical model. Based on the results of monitoring and finite element analysis, the reasons of failures were determined, retrofit design conceptwas developed and numerically verified. This paper describes monitoring and numerical analysis performed and summarizes conclusions fromstudy and retrofit design concept.