The concrete deck depth cannot be less than 7.0 inches, excluding any provision for grinding, grooving, and sacrificial surface. STable 3.5.1-1 Design Step 2.2 - Determine Minimum Slab Thickness "AE" concrete has a compressive strength of 4.0 KSI.įuture wearing surface density - The future wearing surface density is 0.140 KCF. Also, type "AE" concrete should be specified when the deck will be exposed to deicing salts or the freeze-thaw cycle. This includes the 1/2 inch integral wearing surface that is required.ĭeck bottom cover - The concrete bottom cover is set at 1.0 inch since the bridge deck will use reinforcement that is smaller than a #11 bar.Ĭoncrete 28-day compressive strength - The compressive strength for decks shall not be less than 4.0 KSI. See Publication Number FHWA HI-95-017, Load and Resistance Factor Design for Highway Bridges, Participant Notebook, Volume II (Version 3.01), for the method used to compute the parapet properties.ĭeck top cover - The concrete top cover is set at 2.5 inches since the bridge deck may be exposed to deicing salts and/or tire stud or chain wear. * Based on parapet properties not included in this design example. Total transverse resistance of the parapet*: The following units are defined for use in this design example:Ĭritical length of yield line failure pattern*: A common rule of thumb is to make the overhang approximately 0.35 to 0.5 times the girder spacing. In addition, the overhang is set such that the positive and negative moments in the deck slab are balanced. The overhang width is generally determined such that the moments and shears in the exterior girder are similar to those in the interior girder. However, the empirical method could not be used to design the overhang as stated in S9.7.2.2. The empirical method could be used for the positive and negative moment interior regions since the cross section meets all the requirements given in S9.7.2.4. For the equivalent strip method analysis, the girders act as supports, and the deck acts as a simple or continuous beam spanning from support to support. In this example, the equivalent strip method will be used. The next step is to decide which deck design method will be used. Additional information is presented about the design assumptions, methodology, and criteria for the entire bridge, including the concrete deck. Refer to Design Step 1 for introductory information about this design example. The following concrete deck design criteria are obtained from the typical superstructure cross section shown in Figure 2-1 and from the referenced articles and tables in the AASHTO LRFD Bridge Design Specifications (through 2002 interims). The first design step for a concrete bridge deck is to choose the correct design criteria. Table of Contents Design Step 2.1 - Obtain Design Criteriaĭesign Step 2.2 - Determine Minimum Slab Thicknessĭesign Step 2.3 - Determine Minimum Overhang Thicknessĭesign Step 2.4 - Select Slab and Overhang Thicknessĭesign Step 2.5 - Compute Dead Load Effectsĭesign Step 2.6 - Compute Live Load Effectsĭesign Step 2.7 - Compute Factored Positive and Negative Design Momentsĭesign Step 2.8 - Design for Positive Flexure in Deckĭesign Step 2.9 - Check for Positive Flexure Cracking under Service Limit Stateĭesign Step 2.10 - Design for Negative Flexure in Deckĭesign Step 2.11 - Check for Negative Flexure Cracking under Service Limit Stateĭesign Step 2.12 - Design for Flexure in Deck Overhangĭesign Step 2.13 - Check for Cracking in Overhang under Service Limit Stateĭesign Step 2.14 - Compute Overhang Cut-off Length Requirementĭesign Step 2.15 - Compute Overhang Development Lengthĭesign Step 2.16 - Design Bottom Longitudinal Distribution Reinforcementĭesign Step 2.17 - Design Top Longitudinal Distribution Reinforcementĭesign Step 2.18 - Design Longitudinal Reinforcement over Piersĭesign Step 2.19 - Draw Schematic of Final Concrete Deck Design LRFD Steel Girder SuperStructure Design Example Concrete Deck Design Example Design Step 2
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