Mn/DOT Design-Build Program Book 2 – St. Anthony Bridge Project
S.P. 2783-102
13 STRUCTURES
13.1 General
The Contractor shall conduct all Work necessary to meet the requirements of permanent and temporary Structures, including bridges, retaining walls, barriers, box culverts, circular pipes, sign structures, and lighting structures.
13.2 Administrative Requirements
13.2.1 Standards
The most current version of the following shall govern. In the event of a conflict among the standards set forth in Book 3 relating to structures, the order of precedence shall be as set forth below, unless otherwise specified:
13.2.1.1 Bridges
· Mn/DOT Special Provisions*
· Mn/DOT Technical Memoranda*
· Mn/DOT Standard Specifications for Construction*
· Mn/DOT LRFD Bridge Design Manual*
· Mn/DOT Bridge Details Manual, Parts I and II*
· Mn/DOT Bridge Construction Manual*
· AASHTO LRFD Bridge Design Specifications
· AASHTO LRFD Bridge Construction Specifications
· AASHTO Guide Design Specifications for Bridge Temporary Works
· AASHTO Construction Handbook for Bridge Temporary Works
· AASHTO/NSBA Steel Bridge Fabrication Guide Specification
· AASHTO/NSBA Guide Specification for Application of Coating Systems with Zinc-Rich Primers to Steel Bridges
· Remaining standards set forth in Book 3
*Document modified for design-build.
13.2.1.2 Retaining Walls
· Mn/DOT Special Provisions*
· Mn/DOT Technical Memoranda*
· Mn/DOT Standard Specifications for Construction*
· Mn/DOT LRFD Bridge Design Manual*
· Mn/DOT Bridge Standard Plans Manual*
· Mn/DOT Bridge Details Manual Parts I & II*
· Mn/DOT Bridge Construction Manual*
· Mn/DOT Standard Plans Manual*
· AASHTO LRFD Bridge Design Specifications
· AASHTO LRFD Bridge Construction Specifications
· AASHTO Guide Design Specifications for Bridge Temporary Works
· AASHTO Construction Handbook for Bridge Temporary Works
· FHWA Mechanically Stabilized Earth Walls and Reinforced Soil Slopes Design and Construction Guidelines
· FHWA Corrosion/Degradation of Soil Reinforcements for Mechanically Stabilized Earth Walls and Reinforced Soil Slopes
· FHWA Drilled Shafts: Construction Procedures and Design Methods
· FHWA Handbook on Design and Construction of Drilled Shafts Under Lateral Load
· FHWA Ground Anchors and Anchored Systems
· FHWA Manual for Design and Construction Monitoring of Soil Nail Walls
· AASHTO Standard Specifications for Highway Bridges
· Remaining standards set forth in Book 3
*Document modified for design-build.
13.2.1.3 Box Culverts
· Mn/DOT Special Provisions*
· Mn/DOT Technical Memoranda*
· Mn/DOT Standard Specifications for Construction*
· Mn/DOT LRFD Bridge Design Manual*
· Mn/DOT Design-Build Modifications to the Road Design Manual*
· Mn/DOT Bridge Standard Plans Manual *
· Mn/DOT Bridge Construction Manual*
· AASHTO LRFD Bridge Design Specifications
· AASHTO LRFD Bridge Construction Specifications
· Remaining standards set forth in Book 3
*Document modified for design-build.
13.2.1.4 Circular Pipes
· Mn/DOT Special Provisions*
· Mn/DOT Technical Memoranda*
· Mn/DOT Standard Specifications for Construction*
· Mn/DOT Design-Build Modifications to the Road Design Manual*
· Mn/DOT LRFD Bridge Design Manual*
· Mn/DOT Standard Plates Manual*
· AASHTO LRFD Bridge Design Specifications
· AASHTO LRFD Bridge Construction Specifications
· Remaining standards set forth in Book 3
*Document modified for design-build.
13.2.1.5 Sign Structures
· Mn/DOT Special Provisions*
· Mn/DOT Technical Memoranda*
· Mn/DOT Standard Specifications for Construction*
· Mn/DOT Design-Build Modifications to the Road Design Manual*
· Mn/DOT LRFD Bridge Design Manual*
· Mn/DOT Sign Support Standard
· Mn/DOT Standard Overhead Sign Supports, Interim Design B Details
· AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaires and Traffic Signals
· Remaining standards set forth in Book 3
*Document modified for design-build.
13.2.1.6 Lighting Structures
· Mn/DOT Special Provisions*
· Mn/DOT Technical Memoranda*
· Mn/DOT Standard Specifications for Construction*
· Mn/DOT Design-Build Modifications to the Road Design Manual*
· Mn/DOT LRFD Bridge Design Manual*
· Mn/DOT Standard Plates Manual*
· Mn/DOT Standard Plans Manual*
· AASHTO Standard Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals
· Remaining standards set forth in Book 3
*Document modified for design-build.
13.2.2 Personnel
The Contractor shall comply with the requirements stated in DBSB-2401.21 (Post Tensioning System) of the Mn/DOT Special Provisions for a post-tensioning engineer (PT Engineer) when post tensioning systems are used for structures.
The design of the bridge shall be conducted by a design engineer who has a minimum of 10 years of cumulative relevant experience in the design of the proposed structural system obtained over the past 12 years, and is a licensed Professional Engineer in the State of Minnesota now or by the time the first notice to proceed is issued.
13.3 Design Requirements
13.3.1 Bridge Load Rating
The Contractor shall load rate all vehicular bridges. The Mn/DOT Bridge Rating and Load Posting Report shall be completed and submitted to Mn/DOT before the bridge is opened to vehicular traffic.
The Contractor shall provide the load rating in VIRTIS software format, using system input. If VIRTIS is unable to rate the bridge type, then another commercially available bridge rating software Acceptable to Mn/DOT may be used.
13.3.2 Design Parameters
13.3.2.1 Loads and Forces
The Contractor shall use 1.0 for the ductility and redundancy load modifiers. The Contractor shall use 1.05 for the importance load modifier.
The Contractor shall use a vessel impact load of 1 empty free floating barge at the 2% flowline of the river (elevation 738.5’).
The Contractor shall use the following dead loads for design. For dead loads not listed, see Mn/DOT LRFD Bridge Design Manual.
· 2-inch wearing surface (DW) 25 lb/ft2
· traffic barrier (DC) use actual weight of barriers per Mn/DOT Bridge Details Manual Parts I & II
The Contractor shall use the following live loads for design. See Mn/DOT LRFD Bridge Design Manual for more information.
· The number of design lanes shall be the integer part of the ratio W/12.0 where W is the clear roadway width in feet between curbs and/or barriers.
· Multiple presence factors shall be in accordance with AASHTO LRFD Bridge Design Specifications Table 3.6.1.1.2-1 except for live load deflection .
· Vehicular live loads for design shall include: HL-93 loading (AASHTO LRFD Bridge Design Specifications Article 3.6.1.2.1), Standard C permit truck, Standard P413 permit truck, and Special permit vehicle. All loads except HL-93 shall be evaluated under strength II.
· For determination of live load distribution for span lengths outside of the limits of the AASHTO LRFD Bridge Design Specifications Article 4.6.2.2 tables, use a live load distribution factor based on the maximum span length limit given in the table.
The Contractor shall use a design wind speed of 100 mph unless the bridge or parts of the bridge is more than 30’ above low ground or water level, in which case the Contractor shall follow AASHTO LRFD Bridge Design Specifications Article 3.8.
The Contractor shall use acceleration coefficients equal to 3% for seismic loads.
The Contractor shall use the thermal load design requirements stated in Mn/DOT LRFD Bridge Design Manual 3.11.1 for non-typical bridges.
The relative humidity shall be taken as 73%.
The bridge shall be designed for the XX level of security.
13.3.2.2 Design Method
The new bridge shall have a 100 year design life.
The Contractor shall consider the following amplified double truck plus lane load case (in place of the double truck plus land load case required by AASHTO LRFD Bridge Design Specifications Article 3.6.1.3) when designing continuous structures for the strength I limit state. This load is for moment and reaction only.
· For bridges with longest span below 100 feet: 90% of the HL-93 double truck with dynamic load allowance plus lane load
· For bridges with longest span between 100 and 200 feet: (90% + (span – 100)*0.2 %) of the HL-93 double truck with dynamic load allowance plus lane load
· For bridges with longest span greater than 200 feet: 110% of the HL-93 double truck with dynamic load allowance plus lane load
The Contractor shall also analyze the bridge structure for a special permit vehicle (strength II limit state).
For steel beam design, the maximum nominal flexural resistance is limited to Fy. The moment redistribution provisions of AASHTO LRFD Bridge Design Specifications Appendix B are not allowed.
The Contractor shall use the AASHTO LRFD Bridge Design Specifications 2004 Interims method for determining losses in prestress components.
13.3.2.3 Slope Stability for New or Replacement Structures
In areas where bridge construction prohibits continued growth of natural vegetation, slope protection shall be provided.
The Contractor shall check the overall stability of earth slopes in the vicinity of all structures including bridge abutments and piers. Overall stability includes internal, external, compound, and global. The factor of safety for slope stability shall be 1.5 or greater. The steepest unreinforced slope allowed shall be 1:2 (V:H).
13.3.2.4 Signs, Lighting, Signals, and Utilities
The Contractor shall provide conduit for future under-bridge lighting.
The Contractor shall install X 1 1/2-inch diameter conduits in the bridge railings to accommodate utilities.
The Contractor shall install X 6-inch diameter conduits in the first bay of both sides of the bridge to accommodate future utilities (RTMC).
Bridge elements shall be designed by the Contractor to accommodate the forces and moments resulting from loads (dead, wind, ice, etc) applied to the signs, lighting, signals, and utilities.
The Contractor shall not mount major sign supports (such as cantilevered signs or sign bridges) on or behind MSE retaining walls.
For overhead lighting to be placed on bridges, the Contractor shall locate the overhead lighting at bridge supports.
13.3.2.5 Visual Quality
Aesthetic treatments for all bridges shall be in accordance with this Section and Section 15 of Book 2.
13.3.3 Additional Design Requirements
13.3.3.1 Bridges
13.3.3.1.1 Geometrics
The areas where substructures shall not be placed are shown in Exhibit A, which will be released soon.
The navigation channel of the Mississippi River shall be defined as a minimum vertical clearance of 30 feet above normal pool elevation (724.64’, 1929 datum), and a minimum channel width of XXXX feet.
The minimum vertical clearance over 2nd Street shall be XXX feet.
The minimum vertical clearance over the Minnesota Commercial Railroad shall be XXX feet.
The minimum vertical clearance for trails and bikeways under a bridge or through a tunnel shall be 10 feet, 0 inches.
The minimum lateral clearance for trails and bikeways under a bridge or through a tunnel shall be 2 feet, 0 inches each side. The maximum total lateral allowance (width of trail plus lateral clearance) for trails and bikeways under a bridge or through a tunnel shall be 14 feet, 0 inches.
13.3.3.1.2 Type
Bridge types allowed are as follows:
· Prestressed concrete I-beams
· Spliced post-tensioned concrete girders
· Steel beams
- Welded beams (including steel box girders)
- Rolled beams
· Cast-in-place concrete slab spans
· Post-tensioned concrete slab spans
· Reinforced concrete box girders
· Post-tensioned concrete box girders
If the Contractor chooses a steel box girder design, a minimum of 3 boxes in each direction of traffic is required. The webs of the steel box shall be a constant 1:X slope.
The Contractor shall not use masonry, timber, and aluminum as materials for permanent bridge superstructures or substructures.
The Contractor shall not design bridges with intermediate hinges.
The Contractor shall not design bridges with floor beam systems.
13.3.3.1.3 Inspection Access
All bridge superstructures, joints, and bearings shall be made accessible by the Contractor for long-term inspection and maintenance. These elements shall be designed and detailed by the Contractor to allow for replacement of joints and bearings. All elements of the superstructure shall be accessible by ladder, a “Snooper” (under-bridge inspection) truck with a 75’ arm, or an under bridge access and inspection system. Box girders with an inside depth of 4 feet or more shall be made accessible for interior inspection during and after construction. Access doors shall swing into the box girders and shall be placed at locations do not impact traffic under bridges. Access doors shall be accessible and lockable at both ends of the bridge. Power and lighting shall be required inside box girders for inspection purposes. The inside of steel box girders shall be primed with the intermediate coat being the color white. Box girders shall prevent access of vermin. Steel box girders which aren’t accessible for interior inspection will not be allowed.
13.3.3.1.4 Components
1. Foundations
The Contractor shall not use timber piles as foundations for permanent structures.
The Contractor shall not use spread footings in waterways unless the footings are keyed into rock.
Scour conditions shall be considered in the design of the bridge.
The Contractor shall design the bridge substructures and foundations to allow a maximum of 1 inch total settlement for tall abutments (h>12 feet) and retaining walls. Total maximum settlement for other piers and abutments shall be limited to 0.1% of adjacent span length. The Contractor shall design the bridge substructures and foundations for a differential settlement of 1/2 inch within a pier or abutment.
2. Abutments
The Contractor shall provide a type of abutment that meets the requirements of the bridge system and the visual quality guidelines developed for the Project. The minimum thickness of abutment parapets and wingwalls shall be 18 inches. For bridges with curved steel girders and for straight bridges with substructures under expansion joints skewed more than 30 degrees, shear lugs shall be used at each abutment to limit transverse movement of the bearings. With the exception of properly designed cast-in-place concrete cantilever or counterfort/buttress wall types, retaining walls shall not serve as abutments for free-standing bridges. Properly designed cast-in-place concrete cantilever or counterfort/buttress retaining walls may be used in lieu of wingwalls at abutments. For all other conditions, MSE walls shall not be constructed in front of bridge abutments.
3. Piers and Pier Caps
The Contractor shall provide a type of pier that meets the requirements of the bridge system and the visual quality guidelines developed for the Project. Drop caps or non-redundant, fracture critical pier caps will not be allowed.
4. Slope Protection
The Contractor shall provide slope protection for all slopes under bridges in accordance with the visual quality guidelines developed for the Project. Concrete slope paving shall be provided for bridges over highways or Railroads. Riprap shall be provided under the bridge over waterways and at any river piers.