JULY 2016 LRFD BRIDGE DESIGN 11-1 This section contains guidance for the design and detailing of abutments, piers, retaining walls, and noise walls. Abutments and piers are used to support bridge superstructures, whereas walls primarily function as earth retaining structures. In most cases, abutments, piers, and walls are reinforced concrete elements. The preferred details for connecting the superstructure to the substructure are dependent on the geometry and type of bridge. For example, flexible substructure units supported by a single line of piles may be constructed integral with the superstructure. Conversely, stiff substructure units are detailed with expansion bearings between the superstructure and substructure to reduce the design loads in the substructure units. General Abutments function as both earth retaining structures and as vertical load carrying components. Integral and semi-integral abutments are designed to accommodate movements at the roadway end of the approach panel. Parapet abutments are detailed to accommodate movements with strip seal or modular expansion joint devices between the concrete deck and the abutment end block. Railroad bridge abutments shall be designed according to the AREMA Manual for Railway Engineering, Volume 2, for the live load specified by the railroad. Design all other abutments according to the AASHTO LRFD Bridge Design Specifications. The Duluth Mesabe & Iron Range Railway requires a special live load. The live load surcharge is found by taking the axle load and distributing it over an area equal to axle spacing multiplied by the track spacing, generally 70 square feet. Do not reduce the surcharge loading for skew. Refer to Article 2.4.1.6.2 when locating utilities near an abutment. When footings are perched on an embankment, consult with the Regional Construction Engineer regarding the use of spread footings. Abutment Type Selection Integral abutments are the preferred type of abutment when all of the following criteria are met: The bridge length and skew meet one of the following: (See Figure 11.1.1) o Bridge length ≤ 300 feet and skew ≤ 20 degrees o Bridge length ≤ 100 feet and skew ≤ 45 degrees o Bridge length is between 100 feet and 300 feet, and 11.1 Abutments 11. ABUTMENTS, PIERS, AND WALLS
ABUTMENTS, PIERS, AND WALLS
May 07, 2023
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