CAIT project no.: CAIT-UTC-NC-1
Fiscal Year: 2014/2015
Rutgers-CAIT Author(s): Marc Maguire, Ph.D., Victor J. Torres, M.S., Patrick Szary, Ph.D.
External Author(s): Joshua Sletton, Utah Department of Transportation
Sponsor(s): USDOT-FHWA, Utah Department of Transportation
A 48 year old prestressed double tee girder bridge located on Icy Springs road in Coalville, Utah, was tested for live load. The test measured strains, deflections and rotations. The instruments used for measuring the respective measurements were strain gages, deflectometers (“twangers”) and tiltmeters.
From the recorded measurements a finite element model (FEM) was calibrated to validate the modeling techniques based on the test data. The FEM implemented two joint link elements to connect the flanges of the FEM deck to model the transverse load distribution of the bridge deteriorated shear connectors. The abutment restraints were modeled by one joint link elements. The deck and the stems were modeled using shell element.
After validating the modeling techniques, a parametric study was developed to study the prediction of FEM girder distribution factors (GDF). The FEM GDF predictions were compared to the prediction proposed by the American Association of State Highway and Transportation Officials (AASHTO) in the provision AASHTO LRFD 2010. The parametric study considered the variable parameters of span length, slab thickness, number of double tees, angle of skew, and stem spacing.
The AASHTO specification provides an inaccurate prediction, therefore a new statistical model was proposed to better predict GDF. Furthermore, rating factors based on different girder distribution factors were studied for the Icy Springs bridge. The bridge has a passing rate for operating level.