ABSTRACT
Bridge decks often overhang past fascia girders in order to increase the width of the deck while limiting the required number of longitudinal girders. Bridge designers typically proportion overhangs so that the same sections can be used for both the interior and exterior girders. While this leads to economical designs, the construction of these overhangs results in torsional moments due to the placement of the screed rails on the overhang form; because in this configuration, the finishing machine can nearly reach the entire deck surface. These moments can cause excessive rotation (shown in Fig. 1) of the fascia girders leading to thin decks, reduced concrete cover, poor rideability, instabilities during construction, and possible girder overstress. The deck overhang is usually formed by wood sheathing supported with brackets spaced over the length of the bridge. The brackets are connected to the top of the fascia girder with steel hangers and react against the girder webs. In some cases, the construction loads have resulted in bridges that were dangerously close to failures resulting from global or local instabilities (Fasl 2008, Shokouhian et al. 2015; Gupta et al. 2006). The overhang width and bracing system can vary significantly from state to state which typically specify a maximum allowable overhang width based on factors such as the girder spacing, girder depth, and deck thickness, to name a few. The current Illinois Department of Transportation (IDOT) Bridge Design Manual does not provide specific restrictions on overhang width. In addition, many bracing systems and options are available to contractors that also vary by state. Exterior girder rotation due to unbalanced eccentric load on overhang deck. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig306_1.tif"/>
For this research, a non-skewed Illinois bridge was monitored during construction to determine the exterior girder rotations due to the unbalanced construction loads. The basic information of the bridge is shown in Table 1. Information of the bridge.
Beam Type
W30x132
Skewed?
None
No of Span
3
Span length
End spans: 13.93 m
Middle span: 16.31 m
Overhang Width
1 m
Girder Spacing
1.98 m
Deck Thickness
203.2 mm
Tie Type
Diagonal
Screed Type
Vibrating Paver
Screed Location
On overhang deck
This paper presents a detailed comparison of the exterior girder rotation between field data and finite element results for the non-skewed bridge to validate the field data. The finite element code Abaqus was used in this study and the results obtained showed good agreement with the field data.
