l Rfd Manual
-
Upload
rommel-hidalgo-diaz -
Category
Documents
-
view
234 -
download
0
Transcript of l Rfd Manual
-
7/30/2019 l Rfd Manual
1/757
LLRRFFDD BBrriiddggeeDDeessiiggnn MMaannuuaall
-
7/30/2019 l Rfd Manual
2/757
-
7/30/2019 l Rfd Manual
3/757
ii
Mn/DOT B RIDGE OFFICE
LRFD Bridge Design Manual
Minnesota Department of Transportation3485 Hadley Avenue North Mail Stop 610
Oakdale, MN 55128-3307Phone: (651) 747-2100 Fax: (651) 747-2108
JULY 2003 OCTOBER 2003 JANUARY 2004 APRIL 2004 OCTOBER 2004DECEMBER 2004 FEBRUARY 2005 MARCH 2005 NOVEMBER 2005
-
7/30/2019 l Rfd Manual
4/757
OCTOBER 2004 LRFD BRIDGE DESIGN i
TABLE OF CONTENTS
1. INTRODUCTION..................................................................................... 1-11.1 Overview Of Manual 5-392 ...............................................................1-1
1.1.1 Chronology Of Manual 5-392 ...................................................1-11.1.2 Material Contained In Manual 5-392 .........................................1-11.1.3 Updates To Manual 5-392 .......................................................1-21.1.4 Format Of Manual References .................................................. 1-2
1.2 General Bridge Information ..............................................................1-21.2.1 Bridge Office .........................................................................1-21.2.2 Highway Systems...................................................................1-81.2.3 Bridge Numbers.....................................................................1-81.2.4 Limit States To Consider In Design ......................................... 1-101.2.5 Ductility, Redundancy, Operational Importance ........................ 1-10
1.3 Procedures................................................................................... 1-101.3.1 Checking Of Mn/DOT Prepared Bridge Plans............................. 1-101.3.2 Checking Of Consultant Prepared Bridge Plans ......................... 1-121.3.3 Schedule For Processing Construction Lettings ......................... 1-151.3.4 Bridge Project Tracking System.............................................. 1-161.3.5 Approval Process For Standards ............................................. 1-18
2. GENERAL DESIGN AND LOCATION FEATURES........................................ 2-12.1 Geometrics ....................................................................................2-1
2.1.1 Bridge Geometrics..................................................................2-12.1.2 Bridge Deck Requirements ......................................................2-22.1.3 Bridge Undercrossing Geometrics .............................................2-72.1.4 Geometric Details ................................................................ 2-152.1.5 Bridge Railings .................................................................... 2-27
2.2 Bridge Aesthetics .......................................................................... 2-272.3 Preliminary Bridge Plans ................................................................ 2-27
2.3.1 General .............................................................................. 2-272.3.2 Bridge Type Selection ........................................................... 2-37
-
7/30/2019 l Rfd Manual
5/757
OCTOBER 2004 LRFD BRIDGE DESIGN ii
2.4 Final Bridge Plans and Special Provisions.......................................... 2-422.4.1 Final Design Instructions ....................................................... 2-44
2.4.1.1 Superstructure ................................................................ 2-442.4.1.1.1 Framing Plan ..................................................... 2-442.4.1.1.2 Concrete Wearing Course .................................... 2-452.4.1.1.3 Diaphragms and Cross-frames ............................. 2-45
2.4.1.2 Pedestrian Bridges........................................................... 2-462.4.1.3 Temporary Bridges and Widenings ..................................... 2-482.4.1.4 Bridge Approaches........................................................... 2-492.4.1.5 Survey........................................................................... 2-502.4.1.6 Utilities .......................................................................... 2-502.4.1.7 Precedence of Construction Documents............................... 2-512.4.1.8 Design Calculation Requirements ....................................... 2-51
2.4.2 Final Plans .......................................................................... 2-522.4.2.1 Drafting Standards .......................................................... 2-532.4.2.2 Drafting Guidelines .......................................................... 2-532.4.2.3 General Plan and Elevation ............................................... 2-552.4.2.4 Bridge Layout and Staking Plan ......................................... 2-602.4.2.5 Standard Abbreviations .................................................... 2-632.4.2.6 Inclusion of Standard Bridge Details in Plan Sets.................. 2-632.4.2.7 Use of Bridge Standard Plans ............................................ 2-632.4.2.8 Standard Plan Notes ........................................................ 2-632.4.2.9 Quantity Notes and Pay Items ........................................... 2-64
2.4.3 Revised Sheets .................................................................... 2-652.5 Reconstruction Guidelines and Details .............................................. 2-66
2.5.1 Superstructure .................................................................... 2-662.5.1.1 Railings.......................................................................... 2-662.5.1.2 Wearing Course............................................................... 2-682.5.1.3 Expansion/Fixed Joints ..................................................... 2-68
2.5.2 Substructure ....................................................................... 2-802.5.2.1 Abutments...................................................................... 2-802.5.2.2 Piers.............................................................................. 2-80
2.5.3 Pavement ........................................................................... 2-80
-
7/30/2019 l Rfd Manual
6/757
OCTOBER 2004 LRFD BRIDGE DESIGN iii
2.6 Construction Requirements............................................................. 2-86Appendix 2-A: Bridge Type Numbers ....................................................... 2-87
Appendix 2-B: Bridge Special Provisions................................................... 2-88
Appendix 2-C: Standard Abbreviations..................................................... 2-92
Appendix 2-D: Bridge Details Part I (B-Details) ......................................... 2-94
Appendix 2-E: Bridge Details Part II ........................................................ 2-96
Appendix 2-F: Bridge Standard Plans: Culverts ......................................... 2-98
Appendix 2-G: Bridge Standard Plans: Retaining Walls ............................... 2-99
Appendix 2-H: Standard Plan Notes....................................................... 2-100
Appendix 2-I: Standard Summary Of Quantities Notes ............................. 2-109
Appendix 2-J: Bridge Pay Items ............................................................ 2-111
Appendix 2-K: Conversion From Inches To Decimals Of A Foot .................. 2-115
3. LOADS AND LOAD FACTORS .................................................................. 3-13.1 Load Factors And Combinations ........................................................3-13.2 Load Modifiers ................................................................................ 3-33.3 Permanent Loads (Dead And Earth)...................................................3-33.4 Live Loads .....................................................................................3-4
3.4.1 HL-93 Live Load, LL................................................................3-43.4.2 Multiple Presence Factor, MPF .................................................. 3-43.4.3 Dynamic Load Allowance, IM ...................................................3-43.4.4 Pedestrian Live Load, PL .........................................................3-43.4.5 Braking Force, BR ..................................................................3-53.4.6 Centrifugal Force, CE .............................................................. 3-53.4.7 Live Load Application To Buried Structures ................................3-53.4.8 Live Load Surcharge, LS..........................................................3-5
3.5 Water Loads, WA ............................................................................3-53.6 Wind Loads, WS..............................................................................3-53.7 Wind on Live Load, WL ....................................................................3-63.8 Earthquake Effects, EQ ....................................................................3-63.9 Ice Load, IC ................................................................................... 3-63.10 Earth Pressure, EV, EH, Or ES...........................................................3-63.11 Temperature, Shrinkage, Creep, Settlement, TU, SH, CR And SE ...........3-7
-
7/30/2019 l Rfd Manual
7/757
-
7/30/2019 l Rfd Manual
8/757
-
7/30/2019 l Rfd Manual
9/757
OCTOBER 2004 LRFD BRIDGE DESIGN vi
5.7.2 Prestressed I-Beam Design Example....................................... 5-715.7.3 Three-Span Haunched Post-Tensioned Concrete Slab
Design Example ................................................................. 5-101
6. STEEL STRUCTURES............................................................................... 6-16.1 Materials .......................................................................................6-16.2 General Dimensions And Details ........................................................6-36.3 General Design Philosophy ...............................................................6-7
6.3.1 Shear Connectors ..................................................................6-96.3.2 Fatigue................................................................................. 6-96.3.3 Deflections............................................................................6-96.3.4 Camber .............................................................................. 6-10
6.4 Rolled Beams ............................................................................... 6-136.5 Plate Girders ................................................................................ 6-13
6.5.1 High Performance Steel Girders.............................................. 6-146.6 Curved Girders ............................................................................. 6-146.7 Box Or Tub Girders ....................................................................... 6-156.8 Bolted Connections And Splices....................................................... 6-156.9 Two-Span Plate Girder Design Example............................................ 6-16
7. RESERVED
8. WOOD STRUCTURES.............................................................................. 8-18.1 Materials .......................................................................................8-1
8.1.1 Wood Products ......................................................................8-18.1.2 Fasteners And Hardware .........................................................8-28.1.3 Wood Preservatives ................................................................8-2
8.2 Timber Bridge Decks ....................................................................... 8-38.2.1 General ................................................................................ 8-38.2.2 Geometry .............................................................................8-58.2.3 Design/Analysis .....................................................................8-58.2.4 Detailing...............................................................................8-68.2.5 Camber/Deflections................................................................ 8-6
-
7/30/2019 l Rfd Manual
10/757
DECEMBER 2004 LRFD BRIDGE DESIGN vii
8.3 Timber Pile Caps.............................................................................8-68.3.1 Geometry .............................................................................8-78.3.2 Design/Analysis .....................................................................8-78.3.3 Detailing...............................................................................8-78.3.4 Camber/Deflections................................................................8-7
8.4 Additional References ......................................................................8-78.5 Design Examples ............................................................................8-8
8.5.1 Longitudinally Laminated Timber Deck Design Example ............... 8-88.5.2 Design Example: Timber Pile Cap ........................................... 8-26
9. DECKS AND DECK SYSTEMS................................................................... 9-19.1 General .........................................................................................9-1
9.1.1 Deck Drainage.......................................................................9-29.2 Concrete Deck on Beams ................................................................. 9-2
9.2.1 Deck Design and Detailing.......................................................9-49.3 Reinforced Concrete Deck Design Example ....................................... 9-17
10. FOUNDATIONS .................................................................................... 10-110.1 Determination of Foundation Type and Capacity ................................ 10-1
10.1.1 Foundation Report................................................................ 10-110.1.2 Foundation Recommendations ............................................... 10-1
10.2 Piles............................................................................................ 10-310.3 Drilled Shafts ............................................................................... 10-510.4 Footings ...................................................................................... 10-8
10.4.1 General .............................................................................. 10-810.4.2 Footing Supported on Piling or Drilled Shafts............................ 10-910.4.3 Spread Footings................................................................. 10-10
10.5 Pile Bent Piers and Abutments ...................................................... 10-1110.6 Evaluation of Existing Pile Foundations when Exposed by Scour ......... 10-1110.7 Structure Excavation and Backfill .................................................. 10-13
-
7/30/2019 l Rfd Manual
11/757
OCTOBER 2004 LRFD BRIDGE DESIGN viii
Appendix 10-A: Sample Bridge Construction Unit Recommendations
(Future Content) .......................................................... 10-14
11. ABUTMENTS, PIERS, AND WALLS ....................................................... 11-111.1 Abutments ................................................................................... 11-1
11.1.1 Integral or Contraction Abutments.......................................... 11-311.1.2 Parapet Abutments............................................................... 11-6
11.1.2.1 Low Abutments ............................................................... 11-911.1.2.2 High Abutments .............................................................. 11-9
11.1.3 Wingwalls ......................................................................... 11-1211.1.4 Approach Panels ................................................................ 11-20
11.2 Piers ......................................................................................... 11-2111.2.1 Geometrics ....................................................................... 11-2111.2.2 Columns ........................................................................... 11-2111.2.3 Cap.................................................................................. 11-2111.2.4 Crash Walls....................................................................... 11-2211.2.5 Design and Reinforcement................................................... 11-2311.2.6 Miscellaneous .................................................................... 11-24
11.2.6.1 Pile Bent ...................................................................... 11-2511.3 Retaining Walls........................................................................... 11-25
11.3.1 Cantilever Retaining Walls ................................................... 11-2511.3.2 Counterfort Retaining Walls ................................................. 11-2511.3.3 Anchored Walls.................................................................. 11-2611.3.4 Mechanically Stabilized Earth Walls....................................... 11-2611.3.5 Prefabricated Modular Walls................................................. 11-2811.3.6 Timber Noise Walls on Retaining Walls .................................. 11-2811.3.7 Cantilevered Sheet Pile Walls ............................................... 11-2811.3.8 Design Charts of Cantilevered Sheet Pile Soil Retention
Walls for Temporary Applications.......................................... 11-29
11.4 Design Examples ........................................................................ 11-3911.4.1 High Parapet Abutment Design Example................................ 11-3911.4.2 Retaining Wall Design Example ............................................ 11-7111.4.3 Three-Column Pier Design Example ...................................... 11-93
-
7/30/2019 l Rfd Manual
12/757
OCTOBER 2004 LRFD BRIDGE DESIGN ix
12. BURIED STRUCTURES.......................................................................... 12-112.1 Geotechnical Properties ................................................................. 12-112.2 Box Culverts ................................................................................ 12-2
12.2.1 Precast ............................................................................... 12-212.2.2 Cast-In-Place ...................................................................... 12-4
12.3 Design Guidance........................................................................... 12-412.4 Arch Or 3-Sided Structure Design Data ............................................ 12-612.5 Design Criteria for Long-Span Corrugated Steel Structures ............... 12-1412.6 10' x 10' Precast Concrete Box Culvert Design Example.................... 12-18
13. RAILINGS ........................................................................................... 13-113.1 Materials ..................................................................................... 13-113.2 Design Requirements..................................................................... 13-1
13.2.1 Traffic Railing ..................................................................... 13-813.2.2 Pedestrian/Bicycle Railing...................................................... 13-913.2.3 Combination Railing ........................................................... 13-1013.2.4 Protective Screening........................................................... 13-1013.2.5 Architectural/Ornamental Railings ........................................ 13-11
13.3 Design Examples ........................................................................ 13-1213.3.1 F Rail Design Example ..................................................... 13-1213.3.2 Adhesive Anchor Design Example ......................................... 13-27
14. JOINTS AND BEARINGS ...................................................................... 14-114.1 Bridge Movements and Fixity .......................................................... 14-114.2 Expansion Joints .......................................................................... 14-2
14.2.1 Thermal Movements ............................................................. 14-214.2.2 Expansion Joint Opening ....................................................... 14-214.2.3 Expansion Joint Detailing ...................................................... 14-314.2.4 Modular Expansion Joints ...................................................... 14-3
14.3 Bearings ...................................................................................... 14-414.3.1 Loads and Movements .......................................................... 14-414.3.2 Bearing Details .................................................................... 14-414.3.3 Elastomeric Bearings ............................................................ 14-5
-
7/30/2019 l Rfd Manual
13/757
-
7/30/2019 l Rfd Manual
14/757
JULY 2003 LRFD BRIDGE DESIGN 1-1
This section contains general information about the manual along with a
general description of the Bridge Office and its procedures. It also
includes guidance on use of the ductility, redundancy, and operational
importance factors given in LRFD 1.3.3 through 1.3.5.
Mn/DOT utilizes a decimal numbering system to classify documents. The
5 before the hyphen represents a publication related to engineering
functions. The 300 series of documents is assigned to the Bridge
Office; the 90 series indicates that this is a Manual. The last digit 2
specifies that the subject matter of the document is Design.
The original bridge design manual, numbered 5-392, provided guidance
for the design of highway structures in Minnesota in accordance with
allowable stress design methods. Subsequently, it has received periodic
updates as design methods have changed. This version of the Bridge
Design Manual contains significant changes. It presents Mn/DOTs design
practices in conformance with a new design methodology, Load and
Resistance Factor Design (LRFD), and also contains fifteen
comprehensive design examples.
Use of this manual does not relieve the design engineer of responsibility
for the design of a bridge or structural component. Although Bridge
Office policy is presented here for numerous situations, content of the
manual is not intended to be exhaustive. Therefore, use of this manual
must be tempered with sound engineering judgement.
After the introductory material provided in this section, the manual
contains material arranged around the following section headings. To
simplify locating material, section numbers correspond to those used in
the LRFD specifications:
1. Introduction
2. General Design and Location Features
3. Loads and Load Factors
4. Structural Analysis and Evaluation5. Concrete Structures
6. Steel Structures
7. Reserved
8. Wood Structures
9. Decks and Deck Systems
10. Foundations
11. Abutments, Piers, and Walls
12. Buried Structures
1 .
I N T RODUCT I O N
1 . 1 O v e r v ie w o f
M a n u a l 5 - 3 9 2
1 . 1 .1 Ch r o n o l o g y
o f M a n u a l 5 - 3 9 2
1 . 1 . 2 M a t e r i a l
Co n t a i n e d i n
M a n u a l 5 - 3 9 2
-
7/30/2019 l Rfd Manual
15/757
JULY 2003 LRFD BRIDGE DESIGN 1-2
13. Railings
14. Joints and Bearings
Memos
This manual will be updated multiple times each year as procedures are
updated and new information becomes available. Current files for each
section of the manual are available on the Bridge Office Web site
[http://www.dot.state.mn.us/bridge/].
Each section of the manual contains general information at the start of
the section. Design examples (if appropriate) are located at the end of
each section. The general content is divided into subsections that are
identified with numerical section labels in the left margin. Labels for
design example subsections are identified with alphanumeric labels in the
left hand margin. The left hand margin also contains references to LRFD
Design Specification Articles, Equations, and Tables. These references
are enclosed in square brackets.
Within the body of the text, references to other sections of this manual
are directly cited (e.g. Section 10.1). References to the LRFD
Specifications within the main body of the text contain a prefix of: LRFD.
A bridge is defined under Minnesota Rule 8810.8000 as a structure
having an opening measured horizontally along the center of the roadway
of ten feet or more between undercopings of abutments, between spring
line of arches, or between extreme ends of openings for multiple boxes.
Bridge also includes multiple pipes where the clear distance between
openings is less than half of the smaller contiguous opening.
In accordance with Minnesota Statute 15.06 Subd. 6, the Commissioner
of Transportation has delegated approval authority for State Preliminary
Bridge Plans, and State, County and City Final Bridge Plans to the State
Bridge Engineer. Plans for all bridge construction or reconstructionprojects located on the Trunk Highway System, and plans on County or
City highways funded fully or in part by state funds shall be approved by
the State Bridge Engineer.
The Bridge Office is responsible for conducting all bridge and structural
design activities and for providing direction, advice, and services for all
1 . 1 . 3 U p d a t e s t o
M a n u a l 5 - 3 9 2
1 . 2 G en e r a l B r i d g e
I n f o r m a t i on
1 . 2 . 1 B r i d g e O f f i ce
1 . 1 . 4 Fo rm a t o f
M a n u a l R e fe r e n c e s
-
7/30/2019 l Rfd Manual
16/757
JULY 2003 LRFD BRIDGE DESIGN 1-3
bridge construction and maintenance activities. The responsibilities
include:
Providing overall administrative and technical direction for the
office.
Reviewing and approving all preliminary and final bridge plans
prepared by the office and consultants.
Representing the Department in bridge design, construction and
maintenance matters with other agencies.
The office is under the direction of the State Bridge Engineer. It is
composed of sections and units as shown on the organizational chart
(Figure 1.2.1.1). Each of these subdivisions with their principal functions
is listed as follows:
A. Bridge Design Section
Responsible for the design, plans, and special provisions activities for
bridges, and miscellaneous transportation structures.
1. Design Unit
a. Designs and drafts bridge plans.
b. Reviews bridge plans prepared by consulting engineers.
c. Prepares special provisions for bridge plans.
d. Designs and drafts plans for miscellaneous highway structures.
e. Provides technical assistance, designs, and plans for special
bridge and structural problems.
2. Bridge Standards and Research Unit
a. Provides design aids and standards for the office and for
consultants, counties, and cities.
b. Coordinates the development and users of computer programs
with data processing systems.
c. Supports computer users throughout the office and manages
the local area network.
d. Provides oversight for research projects, which involve the
Office of Bridges and Structures.
3. Design/Build Unit
a. Provides oversight of design/build projects.4. LRFD Implementation
a. Maintains LRFD Bridge Design Manual.
b. Provides support to office and consulting engineers concerning
LRFD issues.
B. Bridge Planning Section
Responsible for program, cost estimates, preliminary bridge plan
activities for Trunk Highways and review of state aid bridges.
-
7/30/2019 l Rfd Manual
17/757
JULY 2003 LRFD BRIDGE DESIGN 1-4
1. Bridge Agreements and Estimates Unit
a. Selects and negotiates with consulting engineers and
administers engineering agreements for the preparation of
bridge plans.
b. Provides liaison between the office and the consulting engineer
retained to prepare bridge plans.
c. Coordinates public and private utility requirements for bridges.
d. Prepares preliminary, comparative and final cost estimates.
e. Maintains and provides current program and plan status
records.
2. Preliminary Plans
a. Conducts preliminary studies from layouts and develops
preliminary bridge plans.
b. Provides liaison with district and central office road design
through the design stage.
c. Obtains required permits from other agencies for bridges.
3. State Aid Bridge Unit
a. Reviews bridge plans and special provisions for county and
municipal state aid projects.
b. Provides technical assistance to counties and municipalities,
when requested, for nonparticipating projects.
C. Bridge Construction and Maintenance Section
Responsible for bridge construction and maintenance specifications,
and bridge construction and maintenance advisory service activities to
the office and to the job site.
1. Construction and Maintenance Unit; North, Metro and South
Regions
a. Provides construction and maintenance advisory service to
bridge construction and maintenance engineers in the field.
b. Writes bridge construction and maintenance specifications,
manuals and bulletins.
c. Writes and maintains the file of current special provisions for
bridge construction and maintenance.
d. Performs preliminary, periodic and final review of bridge
construction and maintenance projects and makesrecommendations.
e. Reviews bridge plans and special provisions prior to lettings
and makes recommendations.
f. Aids municipal and county engineers with bridge construction
and maintenance problems, upon request.
g. Provides foundation design including selection of pile type,
length, design load, and foundation preparation.
-
7/30/2019 l Rfd Manual
18/757
JULY 2003 LRFD BRIDGE DESIGN 1-5
h. Reviews bridge improvement projects and prepares
recommendations for scope of work.
2. Bridge Ratings Unit
a. Makes bridge ratings and load postings analysis for existing
bridges and maintains the records.
b. Reviews and approves special load permit requests.
3. Structural Metals Inspection Unit
a. Provides inspection services for structural metals, fabrication
and assembly to ensure conformity with plans and
specifications.
4. Fabrication Methods Unit
a. Reviews and approves structural metals shop drawings
submitted by fabricators.
b. Provides fabrication advisory service to designers, fabricators
and field construction and maintenance personnel.
c. Provides overhead sign design services to the Office of Traffic
Engineering, including the design of bridge-mounted sign
trusses.
5. Bridge Management Unit
a. Maintains inventory and inspection data for the 19,600 bridges
in Minnesota. Works with all agencies to make certain
appropriate data is collected.
b. Responsible for implementing bridge management systems to
provide information on bridges for maintenance, repair,
rehabilitation and replacement.
6. Bridge Inspection Unit
a. Provides expert assistance to the Districts in organizing and
conducting inspections of complex bridges, special features,
and fracture critical bridges.
b. Conducts quality assurance inspections of all agencies
responsible for bridge inspections in Minnesota.
c. Reviews, recommends and provides bridge inspection training
for District, county, and municipal bridge inspectors.
D. Hydraulic Engineering Section
Responsible for providing statewide hydraulic engineering servicesthat include design, construction and maintenance activities. In
addition, the section provides leadership in the development and
implementation of hydraulic automation technology, establishes policy
pertaining to hydrology and hydraulics, prepares design aids, provides
client training, participates in research projects, and represents the
department on state and national committees.
1. Bridge Design Hydraulics Unit
-
7/30/2019 l Rfd Manual
19/757
JULY 2003 LRFD BRIDGE DESIGN 1-6
a. Provides bridge and culvert waterway designs for trunk
highway, county, city and township projects.
b. Analyzes and evaluates inplace bridges for scour.
c. Provides technical assistance to counties and municipalities
upon request.
d. Provides training in hydrology and hydraulics.
2. Road Design Hydraulics Unit
a. Evaluates and codes all bridges over water for scour.
b. Provides technical assistance to Districts on all aspects of
drainage design.
c. Reviews and cost prorates storm drains on the municipal and
county state aid system.
d. Coordinates the review of new products and development of
specifications and policies pertaining to their use.
3. Hydraulics Automation Unit
a. Provides leadership and technical direction for managing the
statewide hydraulic automation effort.
b. Develops and implements the means to integrate the hydraulic
design process with the road design process.
c. Develops, implements, and supports a hydraulic information
system to facilitate the sharing of hydraulic data among all
users and stakeholders.
e. Provides statewide training and support in the implementation
and use of hydraulic automation techniques.
-
7/30/2019 l Rfd Manual
20/757
JULY 2003 LRFD BRIDGE DESIGN 1-7
-
7/30/2019 l Rfd Manual
21/757
-
7/30/2019 l Rfd Manual
22/757
JULY 2003 LRFD BRIDGE DESIGN 1-9
2. Since about 1950, a five-digit number has been assigned to each
bridge as it was constructed. The first two digits coincide with the
county number (01-87) in which the bridge is located (99 refers to
temporary bridges). The last three digits are assigned consecutively
using the following guidelines:
a. 001-499 are used for regular trunk highway bridges.
b. 500-699 are used for county bridges.
c. 700-999 are used for interstate bridges (any bridge on or
over the interstate system).
3. In 1991, additional numbers were required for bridges on the state
aid system in Hennepin County and for interstate bridges in Hennepin
County. To allocate more numbers for bridges on the local system an
alpha character is used as the third character of the bridge number.
For example, the next bridge number after Bridge No. 27699 will be
Bridge No. 27A00. Note that this happens only after 500 and 600
series have been exhausted.
To allocate more numbers on the Interstate road system, the 400
series of numbers will be used along with the 700, 800, 900's
presently used. For a bridge number XXYZZ, the following now
applies:
XX = county number (99 = Temporary Bridge)
Y = 0, 1, 2, 3, or R, T, U (for Trunk Highway Bridges)
Y = 4, 7, 8, 9, or V, or W (for Interstate Bridges)
Y = X and Y (Trunk Highway or Interstate Culverts)
Y = 5 or 6 or A through H (for non-trunk highway Bridges)
Y = J through N, and P, Q (for non-trunk highway Culverts)
ZZ = Sequence number (00 through 99)
4. In cases of twin bridges, a westbound or southbound lane bridge is
generally assigned a lower number than an eastbound or northbound
lane bridge.
All bridge numbers are assigned by the Bridge Office (phone 651-747-2122). A complete listing of all numbered bridges is available in
computer printout form entitled Minnesota Trunk Highway Bridge Log-
Statewide Listing.
-
7/30/2019 l Rfd Manual
23/757
JULY 2003 LRFD BRIDGE DESIGN 1-10
Bridge designs shall typically consider Strength, Service, Extreme Event,
and Fatigue limit states. The limit state checks will vary with the
component under consideration. Not all elements will require
consideration of all limit states. For example, the fatigue limit state need
not be considered for fully prestressed pretensioned elements.
For most structures and structural elements the load modifiers for
ductility, redundancy, and operational importance shall be 1.00.
Exceptions are noted below:
1. The ductility factor shall be 1.05 for prestressed concrete through-
girder pedestrian bridges when they are over-reinforced.
2. The importance factor shall be 1.05 for a bridge which satisfies any
one of the following three criteria: 1) it is a major river crossing, 2)
its ADT is greater than or equal to 40,000, or 3) it is a new mainline
interstate bridge.
3. The importance factor shall be 0.95 for bridges with an ADT less than
500.
This section covers the Bridge Office procedures for checking of bridge
plans, scheduling of projects, and revising or creating standards.
The general practice of most engineering offices is to require that designs
they produce be checked before they are reviewed and certified by the
Engineer in Responsible Charge. Although this practice has always
been required for structures designed for Mn/DOT, it is recognized that
the quality of the checking process often varies according to time
restraints, confidence in the designer, and the instructions given to the
checker. Therefore, in order to maintain a consistent design checking
process the following guidance is given for routine bridge designs.
For more complex or unusual designs, the checker is advised to discuss
additional requirements with the design unit leader. Also, the checking
process described is not meant to apply to the check or review functionsrequired for Mn/DOT review of consultant plans (see Section 1.3.2.) or
for construction false work reviews. (See the Bridge Construction
Manual.)
Three types of design checking will apply:
a. An independent analysis of the completed design.
b. A check of original design computations for mathematical accuracy,
application of code, and accepted engineering practice, and
1 . 2 .5 D u c t i l i t y ,
R e d u n d a n c y ,
O p e r a t i o n a l
I m p o r t a n c e
[ 1 . 3 . 3 ]
[ 1 . 3 . 4 ]
[ 1 . 3 . 5 ]
1 . 3 P r o c e d u r e s
1 . 3 .1 Ch e c k i n g o f
M n / DO T Pr e p a r e d
B r i d g e P l a n s
1 . 2 . 4 L im i t S t a t e s
t o Co n s i d e r i n
De s i g n
-
7/30/2019 l Rfd Manual
24/757
JULY 2003 LRFD BRIDGE DESIGN 1-11
c. A review of drafted details for constructibility, and accepted
engineering practice.
Generally, an independent analysis to confirm the adequacy of the
complete design is preferred. Significant differences should be discussed
and resolved before the plan is certified. The separate set of calculations
should be included with the design file as a record of the completed
design check.
When circumstances prevent a complete independent analysis, as a
minimum, an independent analysis shall be completed for the following:
a. Live and dead loads
b. Critical beam lines
c. A pier cap
d. A pier footing
e. Main reinforcement for high abutments
f. An abutment footing
However, for the elements not independently analyzed, the original
computations should be checked for mathematical accuracy of original
design computations, applications of code, and accepted engineering
practice. Checked computations should be initialed by the checker, and
the independent analysis should be included in the design file.
When doing a separate analysis, the checker may make simplifying
assumptions to streamline the checking process. However, when major
differences are found, results must be discussed and resolved with the
designer. For instance, for normal piers, piling might be analyzed for
dead and live loads only if lateral loads appear to have been reasonably
applied in the original computations or the AISC Beam Diagram and
Formula Tables may be used to approximate pier cap moment and
shear.
Whether the check is a completely independent analysis or a minimal
analysis combined with a computations check, some details, such as the
reinforcing details in a wall corner, also require review by the checker.Often referencing old bridge plans with similar details allows the checker
to compare the current design to details that have performed well in the
past.
-
7/30/2019 l Rfd Manual
25/757
JULY 2003 LRFD BRIDGE DESIGN 1-12
Consultant prepared bridge plans are created by private engineering
firms through contracts with the Department. The finished plans are
complete to the extent that they can be used for construction.
Since these plans receive final approval of the State Bridge Engineer,
there must be assurance that the plans are geometrically accurate and
buildable; structural design is adequate and design codes have been
correctly applied; proper direction is given to the construction contractor;
and all construction costs are accounted for. Plan errors may cause
costly construction delays or safety may be compromised by an
inadequate design.
To keep consultant plan reviews consistent and timely, a procedure was
developed as a guide that assigns priority to specific items in the plans.
The overall review includes a Thorough Check and Cursory Review of
various items. The distinction between Thorough Check and Cursory
Review is as follows:
Thorough Check refers to performing complete mathematical
computations in order to identify discrepancies in the plans, or
conducting careful comparisons of known data and standards of the
Project with values given in the plan.
Cursory Review refers to a comparative analysis for agreement with
standard practice and consistency with similar structures, all with
application of engineering judgment. Mathematical analysis is not
required, but may be deemed necessary to identify the extent of a
discrepancy.
The review procedure is listed on the CONSULTANT BRIDGE PLAN
REVIEW form following this section. Headings on this list are defined as
follows:
PARTIAL PLAN: In order to assure that the consultant is proceeding in
the right direction, an early submittal of the plan is required. This
submittal usually consists of the General Plan and Elevation sheetshowing the overall geometry of the structure and the proposed beam
type and spacing; the Bridge Layout Sheet; the Framing Plan sheet; and
the Bridge Survey sheets. Errors and inconsistencies found in this phase
can be corrected before the entire plan is completed. For example, a
framing plan, including the proposed beams, must be assured as
workable on the partial plan before the consultant gets deep into the
design of the remainder of the bridge.
1 . 3 . 2 Ch e c k i n g o f
C o n s u l t a n t
P r e p a r e d B r i d g e
P l a n s
-
7/30/2019 l Rfd Manual
26/757
JULY 2003 LRFD BRIDGE DESIGN 1-13
FINAL PLAN: A final plan should be complete in all areas to the extent
that it can be certified by the designer, although a certification signature
is not required for this phase.
THOROUGH CHECK: Items indicated for checking on the consultants
partial plan must be correct. Given geometry must fit the roadway
layout. Most of this information can be checked using data from the
approved preliminary plan. Approval of the partial plan will indicate that
Mn/DOT is satisfied with the geometry and proposed structure, and the
consultant may proceed with further development of the plan. For the
final plan, obvious drafting and numerical errors should be marked to
point out the errors to the consultant, however, the reviewer should not
provide corrections to errors in the consultants numerical computations.
Checking on the final plan should be thorough to eliminate possible errors
that may occur, such as the pay items in the Schedule of Quantities.
Plan notes and pay items can be difficult for a consultant to anticipate
because of frequent changes by Mn/DOT. Pay items must be correct
because these are carried throughout the entire accounting system for
the Project. Plan (P) quantities must also be correctly indicated.
CURSORY REVIEW: Normally, a cursory review would not require
numerical calculations. This type of review can be conducted by reading
and observing the contents of the plan in order to assure the
completeness of the work. The reviewer should be observant to
recognize what looks right and what doesnt look right. Obvious errors or
inconsistencies on any parts of the plan should be marked for correction.
Although structural design is usually the major focus of any plan, most
consultants are well versed in design procedures and should need only
minimal assistance from our office. A comparison of the consultants
calculations with the plan details should be performed to assure that the
plans reflect their design and that the applicable codes are followed. An
independent design by our office is time consuming and is not
recommended unless there is a reasonable doubt as to the adequacy of
the consultants design.
NO REVIEW: A thorough review of these items would be time-consuming
and may not produce corrections that are vital to construction; therefore,
it is recommended that little or no time be spent on the listed items.
Numerous errors can occur in the Bills of Reinforcement and quantity
values. However, checking this information is also time-consuming,
hence the burden of providing correct data should be placed on the
consultant.
-
7/30/2019 l Rfd Manual
27/757
JULY 2003 LRFD BRIDGE DESIGN 1-14
CONSULTANT BRIDGE PLAN REVIEW
Br. No. ________ RTE ____ DATE: PARTIAL PLAN REC'D. _____ DATE FINAL PLAN REC'D. ______
DESIGN GROUP _______________________ CONSULTANT ______________________________
No. OF SHEETS IN PLAN ______ DESCRIBE COMPLEXITY_________________________________EST. REVIEW TIME BY DESIGN GROUP ________(hrs.) ACTUAL REVIEW TIME __________(hrs)
PARTIAL PLAN FINAL PLAN
THOROUGH CHECK THOROUGH CHECK
Horizontal and vertical clearances Pay items and plan quantities
Stations and elevations on survey line Project numbers
Deck and seat elevations at working points Design data block & Rating on GP&E sheet
Deck cross-section dimensions Job number
Working line location and data Certification block
Coordinates at working points and key stations Standard plan notes
Substructure locations by station Concrete mix numbers
Framing Plan Construction joint locations
Conformance to preliminary plan Prestressed beam design if inadequate design is suspected
Design loads Bridge seat elevations at working points
Utilities on bridge
Existing major utilities near bridge
CURSORY REVIEWSteel beam splice locations and diaphragm spacing; flangeplate thickness increments (enough to save 800+ # ofsteel)Abutment and Pier design to be checked againstconsultants calculations
Conformance to foundation recommendations.Pile loads and earth pressures. Check against consultantscalculations.
CURSORY REVIEW Rebar series increments (min. 3)
Proposed precast beams [per 5-393.509(2)] Interior beam seat elevations
Precast conformance to industry standards Bottom-of-footing elevations (for adequate cover)
Proposed steel beam sections Railing lengths and metal post spacing (check for fit)
Use of B-details and standard plan sheets
Conformance to aesthetic requirements
Notes General, construction, reference, etc.
Quantity items on tabulations
Precast beam design (Check against consultantscalculations)
NO CHECK OR REVIEW REQUIRED
Diagonals on Layout sheet
Figures in Bills of Reinforcement
Bar shapes and dimensions
Rebar placement dimensions
Bar marks on details against listed bars
Quantity values (including total of tabulations)
-
7/30/2019 l Rfd Manual
28/757
JULY 2003 LRFD BRIDGE DESIGN 1-15
To meet the Department s schedule requirements for construction
lettings, the following schedule for processing bridge plans, special
provisions and estimates must be followed. This schedule applies to all
projects: Federal Aid, State Funds and Maintenance. In general,
processing of bridge plans, special provisions and estimates for lettings
shall be given priority over all other work, and every effort must be made
to complete the processing in advance of the times shown, which are
deadlines.
SCHEDULE AND REMARKSDEADLINE TIME BEFORE
LETTING DATE
Federal Project State Project
Bridge plans complete to the extent thatprocessing can be completed on schedule.
14 Weeks(Friday)
12 Weeks(Friday)
Preliminary bridge pay items andquantities for estimate (to Estimating Unit
Design Services)
13 Weeks(Friday)
11 Weeks(Friday)
Bridge plan and special provisions review
Complete (by Bridge Construction Unit)13 Weeks
(Friday)11 Weeks
(Friday)
Bridge special provisions complete, otherInformation or material for inclusion in
Roadway Special Provisions complete (toSpecial Provisions & Final Processing Unit
Design Services)
12 Weeks
(Friday)10 Weeks
(Friday)
Bridge plans complete, approved and
dated (to Office Management Unit)12 Weeks
(Friday)10 Weeks
(Friday)
Final bridge pay items and quantities forestimate (to estimating Unit - Design
Services)
12 Weeks(Friday)
10 Weeks(Friday)
Final computer runs for bridge estimate during 9th week during 8th week
Office copy and final bridge plans (Bridgeplans to Special & Final Processing Unit -
Design Services for submittal to FHWA)
8 1/2 weeks
(Tuesday)7 weeks
(Friday)
Federal Project to FHWA 7 1/2 weeks(Tuesday)
7 weeks
(Friday)
Preliminary advertisement 6 1/2 weeks
(Tuesday)
6 weeks
(Friday)Final advertisement 5 1/2 weeks
(Tuesday)5 weeks(Friday)
Sale of plans and proposals 5 weeks (Friday) 5 weeks(Friday)
Last date for mailing letter addendums bySpecial Provisions & Final Processing Unit
Design Services
10 days(Wednesday)
10 days(Wednesday)
1 . 3 . 3 S ch e d u l e f o r
P r o c e s s i n g
C o n s t r u c t i o n
L e t t i n g s
-
7/30/2019 l Rfd Manual
29/757
JULY 2003 LRFD BRIDGE DESIGN 1-16
Completing a bridge design project for contract letting is a multiple step
process that involves input from a variety of work units and personnel.
To follow the process of these projects, the following major milestones
shown in Tables 1.3.4.1 and 1.3.4.2 are tracked in the Bridge Program
and Project Management System (PPMS). The project typically begins in
the Preliminary Plan Unit, continues through a Bridge Final Design Unit,
and is completed with the Engineer s Estimate. The progress and
activities completed on active bridge projects are updated monthly.
Table 1.3.4.1 PPMS Activities for Mn/DOT Prepared Bridge Plans
PPMS
ACTIVITY NO.
COMPLETED
ACTIVITY
% PROJECT
COMPLETED
0012
0020
00220023
0025
0030
0031
0035
0040
0045
0050
0076
0080
0085
0090
Program Estimate
Bridge Survey
Bridge HydraulicsBridge Grades (Packet)
Bridge Foundations
Bridge Construction Foundation Review
Bridge Aesthetics Recommendation
Bridge Preliminary Plan
District Letter & Prelim. Bridge Estimate
Bridge FHWA Approval
Final Bridge Plan
Designed:
Drawn:
Checked:
Bridge Plan Specifications
Bridge Plan Review by Bridge Construction
Bridge Plan Signed
Bridge Engineer s Estimate
0 %
5 %
6 %8 %
13 %
14 %
14 %
15 %
20 %
20 %
20 - 40 %
40 - 65 %
65 - 85 %
90 %
90 %
95 %
100 %
1 . 3 . 4 B r i d g e
P r o j e c t T r a c k i n g
S y s t em
-
7/30/2019 l Rfd Manual
30/757
JULY 2003 LRFD BRIDGE DESIGN 1-17
Table 1.3.4.2 PPMS Activities for Consultant Prepared Bridge Plans
PPMSACTIVITY NO.
COMPLETEDACTIVITY
% PROJECTCOMPLETED
0012
0019
002000220023
0025
00300031
00350040
00450060
0062
00640066
00680070
00750076
0080
00850090
Program Estimate
Bridge Consultant Pre Design Start
Bridge SurveyBridge HydraulicsBridge Grades (Packet)
Bridge Foundations
Bridge Construction Foundation ReviewBridge Aesthetics Recommendation
Preliminary PlanDistrict Letter & Bridge Prelim. Estimate
Bridge FHWA ApprovalBridge Consultant Start
Consultant Partial Plan Delivery
Mn/DOT Review Partial PlanConsultant Final Plan Delivery
Mn/DOT Review Final PlanConsultant Final Plan In
Tracing BackcheckBridge Plan Specifications
Bridge Plan Review by Bridge Construction
Bridge Plan Signed
Engineer s Estimate
0 %
3 %
5 %6 %8 %
13 %
14 %14 %
15 %20 %
20 %20 %
25 %
30 %30 - 80 %
85 %88 %
88 %90 %
90 %
100 %100 %
-
7/30/2019 l Rfd Manual
31/757
JULY 2003 LRFD BRIDGE DESIGN 1-18
1 . 3 . 5 A p p r o v a l
P r o c e s s f o r
S t a n d a r d s
NEED FOR NEW ORREVISED STANDARD
INPUT FROM S.S.R.C.INPUT FROM BRIDGEDESIGN ENGINEER
INPUT FROM
CONSULTANTS,INDUSTRY, ANDOTHER Mn/DOT
OFFICES
INPUT FROM BRIDGESTANDARDSENGINEER
INPUT FROM BRIDGEDESIGN UNITS
R. & D. COMMITTEEFOR POLICY AND APPROVAL
TO MAKE CHANGES TOSTANDARD OR DEVELOP
A NEW STANDARD
IDEA IS SCRAPPED NO
NE WSTANDARD
DEVELOPED BYSTANDARDS
UNIT, DESIGNUNIT OR
CONSULTANT
S.S.R.C., WITHSTANDARDSUNIT, MAKESCHANGES TOSTANDARD
STANDARDGOES TOR. & D.
COMMITTEE FORAPPROVAL
THE WORDM OD IFI ED A ND AREVISION DATE IS
ADDED TOSTANDARD.
STANDARD IS MADEAVAILABLE.
COMMENTS RESOLVED ANDCHANGES MADE .
STANDARD IS SENT TOSTATE BRIDGE ENGINEER
FOR APPROVAL. A COPY ISSENT TO THE STANDARDS
UNIT.
YELLOWROUTING
SHEET ISDEVELOPED BYBRIDGE
STANDARDSENGINEER
REVISED
STANDARDAFFECTS ONLYBRIDGEOFFICE
NO
YE S
MODIFY
ACCEPT
APPROVALDATE AND
SIGNATUREADDED TO
STANDARD.
TRANSMITTAL LETTERDEVELOPED BY
BRIDGE STANDARDSENGINEER AND
SIGNED BY STATEBRIDGE ENGINEER.
TRANSMITTAL LETTERAND STANDARD SENTTO PRINTER. COPIES
ENTERED INTOSTANDARDS UNIT
FILE.
ARCHIVE OLDSTANDARD
WITHBACKGROUNDOF CHANGES
MANUAL INSERTSRECEIVED BY USERS
FOR PLACEMENTINTO MANUALS.
STANDARD IS SENT OUT ONYELLOW TO OTHER OFFICES
WITHIN Mn/DOT AND TO BRIDGEOFFICE PERSONNEL. THE WORD
M OD IF IED A ND RE VI SIO N DA TEIS REMOVED BEFORE
DISTRIBUTION.
CHANGESREQUESTED BYBRIDGE OFFICE
AND OTHEROFFICES ARE
MADE .
MINOREDITORIALCHANGESMADE TO
STANDARD
NO
REVISIONDATE IS MORE
THAN ONEYEAR OLD
YE S
MODIFY
YE S
-
7/30/2019 l Rfd Manual
32/757
APRIL 2004 LRFD BRIDGE DESIGN 2-1
2 . GENERAL
DESI GN AND
LOCAT I ON
FEATURES
2 . 1 Ge om e t r i c s
2 . 1 . 1 B r i d g e
G eom e t r i c s
The design of a bridge typically takes place in two major phases of work:
preliminary design and final design. During preliminary design, the
structure type, the foundation type, the aesthetics, and the primary
geometry for the bridge are determined. During final design, specific
details for all of the elements of the bridge are developed and presented
in the plan set. These details include material descriptions, quantities,
and geometric information. Final plan sets are typically assembled in an
order that roughly follows the order of construction: from the ground up.
This section of the manual contains a large amount of information useful
for the preparation and assembly of plans for a project. To facilitate the
production of plans and standardize the content of bridge plan sets,
special provisions, B-Details, standard plans, standard plan notes, and
standard pay items have been prepared by the Bridge Office. Appendices
to Section 2 identify the material available.
As the name of the section implies, content for this section is general in
nature. Guidance for the design of specific structural elements (e.g.
decks, retaining walls, etc.) is provided elsewhere in the manual.
Definitions
For discussion of bridge geometrics in this section, roadways are
classified as Mainline Highways, Ramps, Local Roads, and Local Streets.
Each of these four groups is further classified under either Urban or Rural
Design.
The following definitions apply:
Mainline Highways Roadways that carry through traffic lanes for
freeways, expressways, and primary and secondary highways.
Local Roads Rural roads off the trunk highway system.
Local Streets Urban roads off the state trunk highway system.
Ramps Segments of roadway connecting two or more legs at an
interchange.
Urban Design Roadways with curbs on the right and/or left sides.
Rural Design Roadways without curbs. Median Width The distance between the edges of opposing through
traffic lanes.
Auxiliary Lane A lane adjoining a through traffic lane for a purpose
supplementary to through traffic movement such as truck climbing,
weaving, speed change or turning.
-
7/30/2019 l Rfd Manual
33/757
-
7/30/2019 l Rfd Manual
34/757
APRIL 2004 LRFD BRIDGE DESIGN 2-3
Functions of the shoulder include:
Recovery area to regain control of a vehicle.
Emergency parking area for stalled vehicles and escape route for
stranded motorists.
Passageway for bicycles and occasional pedestrians.
Passageway for emergency vehicles.
Parking area for bridge maintenance and inspection vehicle (snooper).
Temporary traffic lane during deck repairs or overlay construction.
Area for deck drainage and snow storage.
Accommodates passing of wide oversize loads, especially farm
machinery.
On two-lane highways, the shoulders provide an escape area to avoid
a head-on collision with an oncoming passing vehicle.
The following shoulder widths for both rural and urban design apply to
trunk highway bridges. In addition, these standards apply to bridges on
local roads at a trunk highway freeway interchange. For local roads and
streets, the bridge roadway widths are given in the State Aid Manual,
Section 5-892.210 and the State Aid Operations Rules, Chapter 8820.
Exceptionally long bridges or bridges with a high cost per square foot
should be evaluated on an individual basis and modifications to these
standards are allowed based on judgment. In addition to these values,
the bridge roadway width shall meet the additional requirements for sight
distance and sharp curvature as specified in Part 3 below.
1) Rural Designa) Two-Lane Rural Design
Shoulder widths are given in the table on Figure 2.1.4.1 and are
dependent on the functional classification of the roadway and
traffic volumes.
b) Four-Lane Rural Design
i) Right Shoulder 12'-0"
ii) Left Shoulder 6'-0"
c) Six- or Eight-Lane Rural Divided Highway
i) Right Shoulder 12'-0"
ii) Left Shoulder 12'-0"The full inside shoulder allows disabled vehicles in the left lane
to stop on the inside shoulder rather than try to cross two or
three lanes of traffic to get to the outside shoulder.
d) Mainline Rural Bridge with Auxiliary Lane
i) Right Shoulder 8'-0"
e) Mainline Rural Bridge with Entrance or Exit Ramps
i) Right Shoulder 8'-0"
-
7/30/2019 l Rfd Manual
35/757
MARCH 2005 LRFD BRIDGE DESIGN 2-4
f) Rural Bridges with Turn Lanes
i) Right Turn Lane
(1)Right shoulder 6'-0"
ii) Left Turn Lanes
(1)Adjacent to a barrier railing: 4'-0" minimum shoulder, 6'-0"
desirable.
g) Rural Ramp Bridges (one 16'-0" lane, one-way)
i) Right Shoulder 6'-0"
ii) Left Shoulder 4'-0"
On ramp bridges the dimension from edge of lane to gutter is
reduced to prevent the appearance of a two-lane bridge on a
one-lane ramp. The roadway width is 26'-0", which allows
traffic to pass a stalled vehicle. With a 16'-0" lane the outside
2'-0" could, in effect, be considered as part of the shoulder for
a 12'-0" lane.
2) Urban Design (Approach Curbs)
For urban designs the bridge gutter lines shall be aligned with the
curb line on the approaching roadway with the following exceptions:
a) On four-lane divided highways where there are no median curbs,
the left shoulder shall be 6'-0".
b) On six- and eight-lane divided highways where there are no
median curbs, the left shoulder shall be 10'-0" minimum.
c) On one-lane urban ramps (16'-0" approach roadway), both right
and left shoulders shall be 4'-0" (provides a 24'-0" roadway).
d) Where an auxiliary lane, ramp, or taper extends onto a mainlinebridge, the right shoulder shall be 6'-0".
e) The minimum distance to a barrier railing is 6'-0" desired, 4'-0"
minimum.
Urban shoulder widths will vary according to functional class, traffic
volumes, scope of work, and quality of pavement surface. Typical
values are shown in the Road Design Manual, Tables 4-4.01A,
4-4.01B, and 4-4.01C. Provide a 2'-0" reaction distance to a raised
island type median or sidewalk curb where vehicle speeds are 40 mph
and under. For design speeds 45 mph and higher, provide a 4'-0"reaction distance.
3) Bus Shoulders
Where the right shoulder has been designated as a bus shoulder a
12'-0" width shall be provided across bridges. See Road Design
Manual 4-4.03 and Table 4-4.03A.
-
7/30/2019 l Rfd Manual
36/757
MARCH 2005 LRFD BRIDGE DESIGN 2-5
4) Additional Width Criteria
a) Where a ramp (loop) bridge is on a radius of 190'-0" or less, or
when the volume of trucks is 10% or greater, the effective traffic
lane is increased from 16'-0" to 18'-0" in width to accommodate
truck turning movements. Increase the width of the ramp bridge
accordingly.
b) For curved bridges longer than 100 feet, check the horizontal
stopping sight distance and increase the inside shoulder width up
to a maximum of 10'-0". See Road Design Manual, Chapter 3 for
calculation of this distance. The 2001 edition of the AASHTO
book, A Policy on Geometric Design of Highways and Streets,
changed the height of object from 6" (muffler) to 2'-0" (tail light).
Table 2.1.2.1 gives widths required for a continuously curving
bridge for various design speeds and curvature, and applies only
where the line of sight is blocked by the railing.
Table 3.1.2.1
Shoulder Width Requirements for Curved Bridges
SHOULDER WIDTH FOR DEGREE OF
CURVATURE LISTEDDESIGN
SPEED6 FT. 8 FT. 10 FT.
70 mph to 0o 45 > 0o 45 to 1o > 1o
60 mph to 1o 15 > 1o 15 to 2o > 2o
50 mph to 2o 30 > 2o 30 to 3o 15 > 3o 15
40 mph to 5o 30 > 5o 30 to 7o > 7o
c) For bridges on tapers, the taper should begin or end at a pier or
an abutment, or continue across the entire length of the bridge.
Extra width to eliminate or simplify a taper or curvature is
permissible where justified by simplified design and construction.
Cross Slopes on Bridges
1) The cross slope on bridge traffic lanes is the same as the approaching
roadway lanes, normally 0.02 ft./ft. The shoulder cross slope on the
bridge may continue at 0.02 ft./ft. or, if better drainage is desired,
may be 0.005 ft./ft. greater than the adjacent lane, with a maximum
cross slope of 0.04 ft./ft. When the bridge deck is superelevated, the
shoulders shall have the same slopes as the adjacent bridge traffic
lanes.
Keep superelevation transitions off bridges. In instances where they
are unavoidable, it is preferable for ease of deck pouring to maintain
-
7/30/2019 l Rfd Manual
37/757
MARCH 2005 LRFD BRIDGE DESIGN 2-6
a straight line across the deck at all locations (allows a straight screed
between paving rails placed at both sides of the deck.)
2) Ramp cross slopes shall be uniform between the bridge curbs with a
slope of 0.02 ft./ft. to the right unless superelevated.
Bridge Median
On divided highways with a separate bridge for each roadway, the
openings between bridges must be a minimum of 8'-0" wide if access for
bridge inspection vehicles (snoopers) is required.
Longitudinal joints along the median of bridges should be used only for
bridge roadways wider than about 100 feet or for other special cases. By
eliminating this joint on bridges with medians, simpler detailing and
simpler construction can be used.
Bridge Sidewalks and Bikeways
Bridge sidewalks of 6'-0" minimum widths are to be provided where
justified by pedestrian traffic. When bicycle traffic is expected, the width
should be 8'-0" minimum and 10'-0" desirable. Where an off road
bikeway is to be carried across a bridge, the full width of the approach
bikeway may be continued across the bridge up to a maximum width of
12'-0". Widths beyond 12'-0" are considered excessive. When the
shoulders of the bikeway cannot be carried over bridges, provide lead-in
guardrail.
The curb height for sidewalks adjacent to the roadway is 8". When the
design speed on the street is over 40 mph, a concrete barrier is required
between the roadway and the sidewalk (or bikeway). In addition, a
pedestrian (or bikeway) railing is required on the outside.
When a barrier is provided between the traffic lanes and the sidewalk,
use the bridge slab for the walkway (i.e., do not require an additional
pour for sidewalk). Advise the road plans designer to provide for any
necessary sidewalk ramping off the bridge.
Sidewalks and bikeways shall have a minimum cross slope of 0.01 ft./ft.
Protective Rails at Bridge Approaches
The ends of bridge railings must be protected from being impacted
(except on low speed roads such as city streets). For design speeds over
40 mph, a crash tested guardrail transition (normally plate beam
guardrail) is required.
-
7/30/2019 l Rfd Manual
38/757
MARCH 2005 LRFD BRIDGE DESIGN 2-7
2 . 1 . 3 B r i d g e
U n d e r c r o s s i n g
G eom e t r i c s
Refer to State-Aid Operation Rules, Chapter 8820 for guardrail
requirements on local bridges.
General Criteria for Lateral Clearance
Bridge undercrossing geometrics must rationalize safety requirements
with costs and physical controls such as span length and permissible
depth of structure. The following guidelines apply in establishing these
geometrics:
1) Safety
Piers, abutments, side slopes and back slopes steeper than 1:3, and
guardrails can all be hazards to an out of control vehicle. It is
desirable at all bridge undercrossings to provide a clear zone recovery
area beside the roadway that is free from these hazards. This clear
zone is given in the Road Design Manual, Section 4-6.0 and is a
function of the roadway curvature, design speed, ADT, and ground
slope. For the area under bridges a practical maximum clear zone of
30 feet may be used as permitted in the 2002 AASHTO Roadside
Design Guide, Table 3.1 based on consistent use and satisfactory
performance. Eliminate side piers from the roadside area wherever
possible. The desirable bridge undercrossing will satisfy the above
safety criteria.
For those locations where it is totally impractical to provide a full clear
zone recovery area at an undercrossing (as at some railroadunderpasses and in certain urban situations), lesser side clearances
are permitted. Where the full recovery areas must be infringed upon,
the greatest side clearances that circumstances will permit shall be
used. A side clearance of 20 feet is not as desirable as 30 feet but is
still better than the absolute minimum clearance. Minimum lateral
clearances are specified under the section for Lateral Clearance for
Mainline Highways.
Where drainage must be carried along the roadway passing under a
bridge, either a culvert must be provided at the approach fill or theditch section must be carried through at the toe of the bridge
approach fill. The use of a culvert will often permit more desirable
bridge geometrics, but the culvert openings can also introduce a
roadside hazard. A determination regarding drainage (need for
culverts, size of a culvert, and assessment of possible hazard) will be
a controlling factor in deciding geometrics of the bridge for the site.
-
7/30/2019 l Rfd Manual
39/757
MARCH 2005 LRFD BRIDGE DESIGN 2-8
2) Economics
Prestressed concrete beam spans (in length up to about 145 feet) are
normally the most economical type of construction for grade
separations. In addition, there will usually be greater economy in
constructing grade separations using two long spans rather than
constructing four shorter spans, provided that a concrete
superstructure can be used.
3) Aesthetics
The use of longer spans will necessitate a deeper superstructure and
higher approach fills. Consideration must be given to the effect of the
depth of structure on the overall appearance and design of the
undercrossing.
For rough calculations during preliminary planning, the depth of
highway bridge superstructures can be assumed to be about 1/20 of
the length of the longest span. (Depth of superstructure refers to the
dimension from top of slab to bottom of beam.) Contact the
Preliminary Bridge Plans Engineer for the exact dimensions to be used
in final planning. Contact the Preliminary Bridge Plans Engineer for
depth of structure on railroad bridges.
Lateral Clearance for Mainline Highways
1) The desirable lateral clearance right and left from the edge of through
traffic lanes to any hazard (as described above) is the full clear zone.
30'-0" may be used as a practical maximum. Side piers shall beeliminated entirely wherever feasible.
2) The details for rural design provide for selection of geometrics that
carry the ditch section through the bridge (Alternate B), and also
geometrics that have a filled ditch (Alternate A). (See Figures 2.1.4.1
and 2.1.4.3.) Alternate A permits a shorter bridge superstructure and
thereby improves the economics and the chance of eliminating side
piers and is used almost exclusively. However, Alternate A can only
be used where ditch culverts will be deleted or used without
introducing a significant safety hazard.
3) Where the roadway ditch section (rural design) is modified at the
bridge (Alternate A), a longitudinal transition from the ditch section to
the 0.04 ft./ft. side slope under the bridge must be provided. Use a
maximum longitudinal slope of 1:20.
4) For an auxiliary lane, the clear zone must be maintained from both
the through traffic lane and the auxiliary lane.
-
7/30/2019 l Rfd Manual
40/757
MARCH 2005 LRFD BRIDGE DESIGN 2-9
5) For ramps and tapers adjacent to the mainline highway, the clear
zone must be maintained from both the through lane and the taper.
A reduced design speed, usually 50 mph, is assumed for the taper.
6) Minimum Lateral Clearances
The following paragraphs list those instances where less than
desirable geometrics can be considered and describes the minimum
values that will apply. Where geometrics less than desirable are to be
used, approval of the State Bridge Engineer and State Design
Engineer must be obtained. For plate beam guardrail with standard
6'-3" post spacing, a minimum of 3'-0" is required between the face
of the guardrail and the face of the pier or abutment to allow room for
the guardrail to deflect. (See Road Design Manual10-7.02.01.)
a) Through Traffic Lanes Right Side
For urban design, the lateral clearance on the right measured
from the edge of the through lane shall be not less than 10'-0"
width for an approaching shoulder plus the minimum width of
approaching berm. This will result in minimum dimension of
16'-0" from the edge of a lane to face of substructure unit.
For auxiliary lanes, tapers, and ramps along urban mainline
highways, the minimum lateral clearance from the edge of a lane
to face of pier or abutment on the right is 10'-0". This provides
room to construct the standard 6'-0" ramp shoulder plus providing
an additional 4'-0" of space for guardrail. However, in no eventshall the distance from the edge of a through lane to the face of a
pier be less than 16'-0".
For rural design, the lateral clearance on the right may be reduced
from the full clear zone distance at railroad overpasses. At these
locations the minimum clearance on the right shall be as described
above for urban designs.
b) Through Traffic Lanes Left Side of Divided Highways
i) Urban Highways with Continuous Median BarriersThe minimum clearances at continuous median barriers are
based on the use of a concrete barrier between the roadways.
(See Std. Plate 8322.)
For urban design, four-lane divided roadways, the minimum
clearance on the left will be based on providing an 8'-0" wide
shoulder from the edge of a through lane to median gutter line
away from the bridge. The 8'-0" wide shoulder may be
-
7/30/2019 l Rfd Manual
41/757
MARCH 2005 LRFD BRIDGE DESIGN 2-10
infringed upon as necessary to carry the median barrier
around a bridge pier. At normal grade separations, using 3'-0"
thick piers, the 8'-0" shoulder may be reduced to 6'-2" at the
pier. (See Figure 2.1.4.11.)
For urban design, six- and eight-lane divided roadways, the
minimum clearance on the left is based on providing a
10'-0" minimum wide shoulder from the edge of a through
lane to median gutter line outside of the bridge. As described
above for four-lane divided roadways, this dimension may be
infringed upon as necessary to carry the median barrier
around a bridge pier. This may result in reducing the shoulder
width from 10'-0" to 8'-2" at normal grade separations
(assuming 3'-0" thick pier). (See Figure 2.1.4.11.)
ii) Urban Highways without Continuous Median Barriers
The warrant requiring a median barrier is based on the median
width and the ADT. (See Road Design Manual.) At those
locations where the clear distance to a center pier is less than
the clear zone distance from the edge of a lane, but where a
continuous barrier will not be provided, a plate beam barrier
will normally be required at the pier.
The pier with plate beam guardrail protection can be used only
in medians that are 18'-6" or wider for four-lane divided
highways, and 22'-6" or wider for six- and eight-lane dividedhighways. (Dimensions are from the edge of lane to edge of
lane.) Piers on high speed roadways should not be placed in
medians narrower than 18'-6" (four- lane) or 22'-6" (six- or
eight-lane).
The face of the plate beam will be located 2'-0" from the face
of the pier. At normal grade separations (with 3'-0" pier
thickness) this will result in a dimension of 5'-6" from the edge
of lane to face of the guardrail on four-lane divided roads, and
a dimension of 7'-6" from the edge of lane to face of theguardrail on six- and eight-lane divided roads.
iii) Rail Overpasses Using Rural Design
For rural design, the median width (edge of lane to edge of
lane) for roadways passing under railroads may be considered
for a reduction. Where a reduced width is used, the distance
from the edge of lane to face of pier should be not less than
20'-0".
-
7/30/2019 l Rfd Manual
42/757
MARCH 2005 LRFD BRIDGE DESIGN 2-11
Lateral Clearances for Ramps
When rural or urban ramps pass under a bridge independently, piers
should be eliminated and the approaching typical section should be
carried through the bridge. On extremely skewed bridges where piers
are necessary, place the face of pier 2'-0" further from roadway than toe
of back slope. (See Figure 2.1.4.8.)
Lateral Clearances for Local Roads
Lateral clearances for local roads are dependent on ADT. The applicable
values are shown on Figure 2.1.4.9.
Lateral Clearance for Local Streets
Locate the face of piers or abutments on or beyond the property line.
This will provide for the ultimate development of the section by local
authorities. A minimum distance of 6'-0" from the face of a curb to the
face of pier or abutment must be provided.
Lateral Clearance for Railroads
Lateral clearances at railroads are to be determined as follows:
1) The statutory clearances diagram shown on Figure 2.1.4.10
represents the absolute minimums that must be adhered to. For
design, a minimum horizontal clearance of 9'-0" to a pier or abutment
is to be used (8'-6" legal).
2) Side piers are placed 4'-0" in from the back slope control point (18'-0"
clear to the centerline of track for a cut section without amaintenance road). This puts the face of pier 2'-0" outside the
bottom of a 3'-0" deep ditch with a 1:2 slope and allows the railroad
to periodically clean the ditch with track-mounted equipment.
3) Mn/DOT and FHWA have agreed to the horizontal clearances shown in
Figure 2.1.4.10 (25'-0" minimum clearance to pier, 30'-6" to back
slope control point) for mainline BNRR tracks at sites meeting the
following conditions:
a) When the standard will not increase the cost of the structure by
more than $50,000.b) When sufficient vertical clearance exists between the tracks and
inplace or proposed roadway profile to accommodate the structure
depth necessary for the longer spans typically required by the
standard.
If these conditions cannot be met, submit a letter to the Railroad
Administration Section along with the signed Preliminary Bridge Plan
-
7/30/2019 l Rfd Manual
43/757
MARCH 2005 LRFD BRIDGE DESIGN 2-12
stating the reasons the standard cannot be met including an estimate
of the increased cost if applicable.
4) Back slopes shall be 1:2 and pass through the back slope control
point shown on Figure 2.1.4.10 for the applicable case. The
dimension to the back slope control point indicates the maximum
extent of federal participation in the construction and must not be
exceeded.
5) The Preliminary Bridge Plans Engineer will contact the Railroad
Administration Section of the Office of Railroads and Waterways to
determine the need for provisions for a maintenance road for track
maintenance equipment. If the Railroad Administration Section
determines that the need is justified, the dimension to the back slope
control point can be increased up to 8'-0".
Waterway Sections Under Bridge Crossing Streams
The Waterway Analysis (hydraulics report) gives information on the
required stream cross section under the bridge including waterway area
and low member elevation. Potential flood damage, both upstream and
downstream, and permitting agencies requirements must be considered.
Vertical Clearance for Underpasses
Table 2.1.3.1 lists the minimum vertical clearance requirements for trunk
highway underpasses.
Table 2.1.3.1
Vertical Clearance for Underpasses
TYPE OF STRUCTUREDESIGN VERTICAL
CLEARANCES
Trunk Highway Under Roadway Bridge 16'-4"
Trunk Highway Under Railroad Bridge 16'-4"
Railroad Under Trunk Highway Bridge 23'-0" *
Trunk Highway Under Pedestrian Bridge 17'-4"
Trunk Highway Under Sign Bridge 17'-4"
Portal Clearances on Truss or Arch 20'-0"
* Critical vertical clearance point offset 8'-6" from centerline of track, statutoryminimum vertical clearance is 22'-0".
For trunk highway bridges over local streets and roads, the minimum
vertical clearance is 16'-4" for rural-suburban designs and 14'-6" for
-
7/30/2019 l Rfd Manual
44/757
-
7/30/2019 l Rfd Manual
45/757
MARCH 2005 LRFD BRIDGE DESIGN 2-14
Vertical Clearance over Waterways
1) Non-Navigable Waterways
A 3'-0" minimum clearance between the 50-year flood stage and low
point on the bridge superstructure is recommended. This amount of
clearance is desired to provide for larger floods and also for the
passage of ice and/or debris. If this amount of clearance is not
attainable due to constraints relating to structure depth, roadway
grades or other factors, reduced clearance may be allowed. The
Preliminary Bridge Plans Engineer, after consultation with the
Hydraulics Section and the Mn/DOT District Office, will determine the
required clearance.
2) Navigable Waterways
a) Waterways that require a construction permit from Coast Guard
(generally considered to be waterways for commercial shipping):
The Mississippi River downstream from I-694 in Fridley
The Minnesota River downstream from Chaska
The St. Croix River downstream from Taylors Falls
The St. Louis River downstream from Oliver, Wisconsin.
Guide vertical clearances published by the Coast Guard are:
Mississippi River:
52'-0" above 2% flowline or 60'-0" above normal pool,
whichever is greater, for the portion downstream of the
Burlington Northern Railroad Bridge near the University of
Minnesota (mile point 853.0). 4'-0" above river stage of 40,000 c.f.s. for the river portion
upstream (mile point 853.0 to 857.6).
Minnesota River:
55'-0" above normal pool from mouth to I-35W bridge
(mile point 10.8).
30.8 feet above 1881 high water from I-35W bridge to
Chaska.
St. Croix River:
52'-0" above 2% flowline or 60'-0" above normal pool from
mouth to Stillwater. St. Louis River:
The Bong Bridge over the St. Louis River Bay in Duluth has
a vertical clearance of 120'-0".
The Preliminary Bridge Plans Engineer shall be consulted when
establishing navigation clearances.
-
7/30/2019 l Rfd Manual
46/757
-
7/30/2019 l Rfd Manual
47/757
APRIL 2004 LRFD BRIDGE DESIGN 2-16
F ig u r e 2 . 1 . 4 .1
G eom e t r i c s
2 - L a n e H ig h w a y ( R u r a l )
-
7/30/2019 l Rfd Manual
48/757
-
7/30/2019 l Rfd Manual
49/757
-
7/30/2019 l Rfd Manual
50/757
-
7/30/2019 l Rfd Manual
51/757
APRIL 2004 LRFD BRIDGE DESIGN 2-20
F ig u r e 2 . 1 . 4 .5
D e s ir a b l e G eom e t r i c s
6 - L a n e D iv i d e d H i g h w a y ( R u r a l)
-
7/30/2019 l Rfd Manual
52/757
MARCH 2005 LRFD BRIDGE DESIGN 2-21
F ig u r e 2 . 1 . 4 .6
D e s ir a b l e G eom e t r i c s
6 - L a n e D iv i d e d H ig h w a y ( U r b a n )
(Details for 8-Lane Divided Highway Are Similar)
-
7/30/2019 l Rfd Manual
53/757
MARCH 2005 LRFD BRIDGE DESIGN 2-22
F ig u r e 2 . 1 . 4 .7
D e s ir a b l e G eom e t r i c s
6 " R a is e d I s l a n d , Tu r n L a n e s , a n d S id e w a l k s ( U r b a n )
-
7/30/2019 l Rfd Manual
54/757
APRIL 2004 LRFD BRIDGE DESIGN 2-23
F ig u r e 2 . 1 . 4 .8
D e s ir a b l e G eom e t r i c s
R am p s ( R u r a l a n d U r b a n )
-
7/30/2019 l Rfd Manual
55/757
APRIL 2004 LRFD BRIDGE DESIGN 2-24
F ig u r e 2 . 1 . 4 .9
L o c a l R o a d s
( R u r a l )
-
7/30/2019 l Rfd Manual
56/757
APRIL 2004 LRFD BRIDGE DESIGN 2-25
F ig u r e 2 . 1 . 4 . 1 0
Ra i lr o a d Cl e a r a n c e s
-
7/30/2019 l Rfd Manual
57/757
-
7/30/2019 l Rfd Manual
58/757
APRIL 2004 LRFD BRIDGE DESIGN 2-27
2 . 1 . 5 B r i d g e
Ra i l i n g s
2 . 2 B r i d g e
A e s t h e t i c s
2 . 3 P r e l i m i n a r y
B r i d g e P l a n s
2 . 3 . 1 Ge n e r a l
See Section 13 of this manual for the policy on design of bridge railings
for Mn/DOT projects.
The aesthetic design process is initiated early in a bridge projects life.
The Preliminary Bridge Plans Engineer will determine which of three
levels of aesthetic attention is appropriate for the bridge.
Level A is intended for bridges with major cultural or aesthetic
significance.
Level B is used for mid-level structures, including highway corridors.
Level C is used for routine bridges.
Maximum levels of Mn/DOT participation in aesthetic costs are given in
the Mn/DOT Policy Manual, Chapter 6, 6-41. For Level A the maximum is
15% but not to exceed $3 million per bridge; for Level B the maximum is
7% but not to exceed $300,000 per bridge; for Level C the maximum is
5% but not to exceed $200,000 per bridge.
The Preliminary Bridge Plans Engineer along with the District Project
Manager coordinates the implementation of the aesthetic design process
as it relates to bridges. Other people, offices