Tableros de puentes

DESIGN AND CONSTRUCTION OF A FULL-WIDTH, FULLDEPTH PRECAST CONCRETE DECK SLAB ON STEEL GIRDER BRIDGE
N. David LeBlanc, M.Eng, P.Eng. Totten Sims Hubicki Associates, Canada

Abstract
The West Sandusky Street over I-75 bridge replacement project consists of a single 170’ span hybrid steel plate girder bridge with concrete deck. To minimize closure times full-width, full-depth precast concretedeck panels are used for the construction of the bridge deck. The precast deck panels are post-tensioned both longitudinally and transversely to minimize cracking and improve durability. The deck panels are constructed with shear stud pockets to allow for the installation of shear studs after erection and post-tensioning. During detail design, a finite element analysis of the bridge deck wascarried out to determine the required level of prestress in the deck. A time dependent analysis was subsequently carried out to determine the long term creep effects and post-tensioning losses, including the effects of restraint from the steel girders. A sensitivity analysis was carried out to determine the optimum curing time required prior to stressing the longitudinal post-tensioning tendons andgrouting the shear pockets. The steel plate girders were designed for the long term creep effects due to the post-tensioning of the deck, which imposed additional axial loads and moments on the steel girders. Bridge construction was completed in the Fall of 2004.

1. Introduction
The West Sandusky Bridge replacement project, located in Findlay, Ohio, was scheduled for replacement in 2004. In orderto minimize bridge closure times, this bridge was selected as a pilot project by the Ohio Department of Transportation for the construction of a full-width, full-depth precast concrete deck panel alternative, to determine the time savings associated with this type of construction, and to monitor the performance of the transverse joints.

LEBLANC, “Full-Width Precast Deck Panel”, 1/10

2.Structural configuration
The West Sandusky Street Bridge over I-75, located in Findlay, Ohio, was a 3 span steel rolled girder bridge with concrete riding deck, scheduled for replacement in 2004. The replacement structure consisted of a single span steel plate girder bridge with a fulldepth precast concrete deck riding surface. The span of the replacement bridge was 170’. Elevation of the new bridgeis shown in Figure 1. and a cross-section is shown in Figure 2.

Figure 1

Figure 2

2.1 Deck panel details
A variety of deck panel configurations were evaluated at the preliminary design stage, including a traditional cast-in-place concrete deck, precast concrete deck form panels with a reinforced cast-in-place concrete deck, full-width precast deck panels with concrete topping, andfull-width, full-depth precast concrete deck panels. The results of the evaluation indicated that up to five weeks of time savings could be achieved through the use of full-width, full-depth precast concrete deck panels, at an additional cost of approximately $200,000.

LEBLANC, “Full-Width Precast Deck Panel”, 2/10

The deck panel segments were 10’ 3” wide, 10 ¾” thick, with shear keyways providedbetween the panels which are grouted after erection. The deck panels were milled ½” after installation to provide a nominal 10 ¼” deck thickness. Smaller sized units would have increased the number of joints in the deck, and increased the time required for lifting operations during erection, prolonging the construction schedule. Larger panel sizes would have resulted in handling andtransportation difficulties due to the additional weight of the panels. The gap between the top flange of the girder and the deck underside was grouted after post-tensioning. The deck end blocks at the abutments were cast after post-tensioning. Pockets were blocked out of the deck panels to allow shear studs to be installed on the top flange of the girders, which were grouted after post-tensioning. The deck...