Deck Overhang Brackets

Deck overhang brackets, such as those shown in Figure 7, are typically required to construct the cantilever portion of the deck slab that extends beyond the exterior girders. The deck overhang brackets always support the overhang formwork and wet concrete, and will typically support a construction walkway and the concrete paving machine when the rails are installed above the bracket. The deck overhang brackets are typically selected from manufacturer catalogues and prefabricated components. The contractor is responsible for selecting the proper deck overhang bracket and spacing, as well as the design of any addition formwork. In some states, the contractor is required to submit computations sealed by a Professional Engineer, verifying the selection and spacing of the deck overhang brackets to be used to construct the concrete deck slab.

The bridge designer should consider the loads imparted on the exterior girders as part of the girder constructibility checks, as the eccentricity of the deck weight and other loads acting on the overhang brackets creates applied torsional moments on the exterior girder. The overhang bracket also imparts a lateral load on the girder top flange and bottom flange or web, depending on the bearing location of the bottom portion of the bracket. In most cases, deck overhang brackets are typically spaced at 3.0 or 4.0 feet along the exterior girders. Article C6.10.3.4 provides equations that can be used, in lieu of a refined analysis, to estimate the maximum flange lateral bending moments due to the eccentric loading caused by the deck overhang brackets.

Also where practical, the deck overhang brackets should be carried to the intersection of the bottom flange and web. The brackets may bear on the girder webs if temporary bracing is provided to ensure that the web is not damaged and that the associated deformations permit proper placement of the concrete deck slab. Alternatively, the out-of-plane bending of the web could be checked using refined analysis techniques in order to ensure that the lateral load imparted by the deck overhang bracket does not cause damage to the web or interfere with construction of the concrete deck slab. When required, notes should be included in the contract plans or specifications stating the need for a contractor to submit computations, sealed by a Professional Engineer, that verify the deck overhang bracket does not cause damage to the web.