ABSTRACT
Bridge decks regularly overhang past the exterior girder to increase the overall width of the bridge and limit the number of longitudinal girders. The overhang is typically constructed with formwork and overhang brackets attached to the top flange of the exterior girder and rest against its web. This overhang setup is shown below in Figure 1, including how loads are distributed for analysis purposes. Overhang Setup with Bracket and Load Placement (<xref ref-type="bibr" rid="ref187_3">“User’s Manual. TAEG 2.1.” (2005)</xref>. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig187_1.tif"/>
The construction of the deck overhang leads to torsional moments which act on the exterior girder, a loading which is typically not considered during the design and selection of the exterior girder sections. These moments can lead to excessive rotation of the exterior girder which has the capability of causing thin bridge decks, reduced concrete cover, poor rideability, and possible girder overstress.
One method to assess the rotation of exterior girders during the construction of the deck is a program called Torsional Analysis of Exterior Girders (TAEG), developed to analyze the response of exterior steel bridge girders due to construction loading.
Previous research into the rotation of exterior girders is inconclusive. Previous works examined the effects of overhang brackets transferring construction loads into the web and top flange of the exterior girder, resulting in local instabilities in steel girder bridges and global instabilities in concrete girder bridges (Fasl 2008). Research does exist relating to the TAEG program, with previous studies finding that the program yielded results which did not compare well to field tests due to uncertainty in loading conditions and lateral support provided by falsework (Roddis, Kriesten, and Ziu, 1999).
Three bridges were analyzed in this study. All three bridges were continuous steel girder bridges. All of the bridge decks were approximately eight inches thick. One of the bridges had W30x124 girders, another had 30WF99 girders, and the final bridge had 78 inch plate girders. One of the bridges had a skew of 24 degrees, whereas the two others had negligible skew. For all bridges, spacing for permanent lateral supports was inconsistent and the number of tem-
porary lateral supports exceeded the number which could be input into the program, so an equivalent cross sectional area was used.
For each of the three bridges, multiple cases were considered for the placement of the temporary lateral supports and the results were compared to the field results. For these different cases, the arrangements and placement of the tie rods and timber blocks were varied to help account for the uncertainty within the tempo-
rary lateral supports in the field. Seven configurations for the temporary lateral supports were considered and data was recorded for each.
During the deck placement for each of these three bridges, tilt sensors were placed on the bottom flange of the exterior girder and measured the rotation experienced throughout the construction process. The rota-
tion results for each of the bracing configurations were compared to field data collected during the construc-
tion of the concrete deck to assess whether certain configurations yielded accurate results compared to the field data.
