Wyoming Department of Transportation
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BRASS PIER(LRFD) Deck Analysis

  DECK ANALYSIS  
 

The Deck Analysis and Loading Component will apply dead and live loads to a bridge deck section (one-foot-wide transverse strip) and distribute the loads as reactions to the girders. The reactions output from the Deck Analysis and Loading Component may be used as uniform load per foot for longitudinal girder analysis. The longitudinal girder reactions at the pier are then used by the Pier Analysis and Loading Component. An understanding of how BRASS-PIER(LRFD)TM and a longitudinal girder analysis system such as BRASS-GIRDER(LRFD)TM work together to determine loads to the pier is paramount to utilizing BRASS-PIER(LRFD)TM to its fullest extent. The Deck Analysis and Loading Component can analyze bridge decks supported on two or more girders, up to a maximum of twenty. The Deck Loading Component has three purposes. The first is to assist the engineer in the analysis of the deck itself. See BRASS-GIRDER(LRFD)TM for complete information. The second is to assist in the analysis of the longitudinal girder system with the distribution of the dead load of the deck to the girders. The third is to assist in the analysis of a frame pier with the distribution of live load to the girder bearings and hence to the pier.
 


 DECK LOADING

 The dead load distribution section of the Deck Analysis and Loading Component will calculate and apply dead loads to the deck using the dimensions of the deck, curbs, etc., and any superimposed loads input.

Up to 10 uniform and 10 concentrated loads may be applied to the deck. A wearing surface may also be applied. The limits of the wearing surface will be defined by the curbs and median, or the limits of the wearing surface may be input. The Deck Loading Component will allow stage loading of the deck. This feature is used in the analysis of a longitudinal girder system where the deck slab is composite with the girders. The construction of a typical composite girder bridge involves the placement of the fluid concrete on the girders, followed by the placement of the curbs, railings, etc., on the hardened concrete slab. In the analysis of the longitudinal girder system, this results in a two stage dead loading of the structure:

  1. The load due to the weight of the fluid concrete being applied to the non-composite girder section.
  2. The load due to the weight of the curbs, railing, etc., being applied to the composite slab-girder section.

The placement of the fluid concrete on the girders is analyzed by calculating the uniform load on the girders due to the weight of the slab and applying this uniform load to the girder in a structural analysis program, such as BRASS-GIRDER(LRFD)TM. BRASS-PIER (LRFD)TM treats the deck as a continuous one foot wide beam over the girders. The reactions due to this one foot wide beam are calculated. The reactions at the girders for the one foot strip of deck then become the uniform loads (in kips per foot) to be applied to the individual non-composite girders in the structural analysis. The placement of the curbs, railing, etc., on the slab is analyzed by BRASS-PIER(LRFD)TM in the same method mentioned above to determine the uniform loads to apply to the individual composite girders in the structural analysis.

The input command set for the dead load distribution run may be saved, and with minor modifications, used for the live load distribution for frame pier analysis. The live load distribution section of the Deck Loading Component will position a specified live load (truck and lane) transversely on roadway at one foot intervals and calculate the live load reaction to each girder for each position. The resulting live load reactions are stored internally for use by the frame section of the Pier Analysis and Loading Component. The live load distribution section must be executed immediately prior to, and in the same run as, the frame section of the Pier Analysis and Loading Component so that the live load reactions will be available for use in applying the live load to the pier.

 

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