AASHTO LOAD AND RESISTANCE FACTOR

“LRFD”BRIDGE DESIGN SPECIFICATIONS

LRFD IMPLEMENTATION BY

OHIO DEPARTMENT OF TRANSPORTATION

http://www.fhwa.dot.gov/bridge/lrfd/index.htm

1. All new bridges on which States initiate preliminary engineering after October 1, 2007, shall be designed by the LRFD Specifications.

http://www.fhwa.dot.gov/bridge/lrfd/index.htm

2. All new culverts, retaining walls, and other standard structures on which States initiate preliminary engineering after October 1, 2010, shall be designed by LRFD Specifications, with the assumption that the specifications and software for these structures are "mature" at this time.

http://www.fhwa.dot.gov/bridge/lrfd/index.htm

3. States unable to meet these dates will provide justification and a schedule for completing the transition to LRFD.

http://www.fhwa.dot.gov/bridge/lrfd/index.htm

4. For modifications to existing structures, States would have the option of using LRFD Specifications or the specifications which were used for the original design.

http://www.dot.state.oh.us/se/

1. Major Projects as defined by the PDP – Projects starting Step 6 after July 20, 2007 shall have the structures designed using the LRFD Bridge Specifications.

2. Minor Projects as defined by the PDP – Projects starting Step 3 after July 20, 2007 shall have the structures designed using the LRFD Bridge Specifications.

3. Minimal Projects as defined by the PDP – Projects starting Step 1 after July 20, 2007 shall have the structures designed using the LRFD Bridge Specifications.

Local projects using the Federal Aid and the ODOT PDP process shall have the structures designed using the LRFD Bridge Specifications after October 1, 2007 .

This commitment does not apply to the rehabilitation of existing structures. Until further notice, the design for rehabilitation of existing structures should be in accordance with the AASHTO Standard Specifications for Highway Bridges, 17th Edition, and the ODOT Bridge Design Manual.

This commitment does not apply to the rehabilitation of existing structures. Until further notice, the design for rehabilitation of existing structures should be in accordance with the AASHTO Standard Specifications for Highway Bridges, 17th Edition, and the ODOT Bridge Design Manual.

This commitment does not apply to the rehabilitation of existing structures. Until further notice, the design for rehabilitation of existing structures should be in accordance with the AASHTO Standard Specifications for Highway Bridges, 17th Edition, and the ODOT Bridge Design Manual.

The Department’s Consultants Committee has decided that completion of specific training courses will not be a prequalification requirement. However, beginning immediately all website postings for new consultant contracts that include bridge design will include a requirement to address the training and experience (in LRFD) of the proposed staff.

Additionally, firms with current contracts that will require LRFD as a result of the project development schedule will be required to demonstrate an adequate combination of training and experience in the new design methods.

ODOTLOAD AND RESISTANCE

FACTOR DESIGNTRAINING COURSES

LRFD Loads & General Overview

Steel Design

Reinforced Concrete Design

Prestressed Concrete Design

Foundation Design

ONLINE REGISTRATION

LRFD BRIDGE DESIGN SPECIFICATIONS

ANDTHE 2007 ODOT

BRIDGE DESIGN MANUAL

LISTS AND ADDRESSES THE EXCEPTIONS TAKEN BY THE OhioDOT TO THE LRFD BRIDGE DESIGN SPECIFICATIONS

BDM SECTION 1000:

LOADS, LOAD COMBINATIONS AND

LIMIT STATES

• DD - Downdrag• DC - Structural Components

and Attachments• DW - Wearing Surfaces and

Utilities

• EH - Horizontal Earth Pressure

• EL - Locked-In Force Effects Including Pretension

• ES - Earth Surcharge Load• EV - Vertical Pressure of

Earth Fill

Permanent LoadsLoad Definitions

• BR - Veh. Braking Force• CE - Veh. Centrifugal Force• CR - Creep• CT - Veh. Collision Force• CV - Vessel Collision Force• EQ - Earthquake• FR - Friction• IC - Ice Load• LL - Veh. Live Load• IM - Dynamic Load

Allowance

• LS - Live Load Surcharge• PL - Pedestrian Live Load• SE - Settlement• SH - Shrinkage• TG - Temperature Gradient• TU - Uniform Temperature• WA - Water Load• WL - Wind on Live Load• WS - Wind Load on Structure

Transient LoadsLoad Definitions

STANDARD SPECIFICATIONS LIVE LOAD MODEL

LRFD LIVE LOAD MODEL

EQ IC CT CVStrength I γp 1.75 1.00 --- --- 1.00 0.50/1.20 γtg γse --- --- --- ---

Strength II γp 1.35 1.00 --- --- 1.00 0.50/1.20 γtg γse --- --- --- ---

Strength III γp --- 1.00 1.40 --- 1.00 0.50/1.20 γtg γse --- --- --- ---

Strength IV --- 1.00 --- --- 1.00 0.50/1.20 --- --- --- --- --- ---Strength V γp 1.35 1.00 0.40 1.00 1.00 0.50/1.20 γtg γse --- --- --- ---

Ext Event I γp γeq 1.00 --- --- 1.00 --- --- --- 1.00 --- --- ---

Ext Event II γp 0.50 1.00 --- --- 1.00 --- --- --- --- 1.00 1.00 1.00

Service I 1.00 1.00 1.00 0.30 1.00 1.00 1.00/1.20 γtg γse --- --- --- ---

Service II 1.00 1.30 1.00 --- --- 1.00 1.00/1.20 --- --- --- --- --- ---Service III 1.00 0.80 1.00 --- --- 1.00 1.00/1.20 γtg γse --- --- --- ---

Service IV 1.00 --- 1.00 0.70 --- 1.00 1.00/1.20 --- 1.00 --- --- --- ---Fatigue --- 0.75 --- --- --- --- --- --- --- --- --- --- ---

LL IM CE BR PL LS

DC DD DW EH EV ES EL

Load Combination FRWLWSWA

Use One of These at a Time

SETG

TU CR SH

Load Combinations and Load Factors

γp

• Strength I: Basic load combination relating to the normal vehicular use of the bridge without wind.

• Strength II: Load combination relating to the use of the bridge by Owner-specified special design vehicles, evaluation permit vehicles, or both, without wind.

• Strength III: Load combination relating to the bridge exposed to wind in excess of 55 mph.

• Strength IV: Load combination relating to very high dead load to live load force effect ratios.

• Strength V: Load combination relating to normal vehicular use with a wind of 55 mph.

Load Combination Descriptions

• Extreme Event I: Load combination including earthquakes.

• Extreme Event II: Load combination relating to ice load, collision by vessels and vehicles, and certain hydraulic events with a reduced live load.

Load Combination Descriptions

• Service I: Load combination relating to normal operational use of the bridge with a 55 mph wind and all loads at nominal values.

• Service II: Load combination intended to control yielding of steel structures and slip of slip-critical connections due to vehicular load.

• Service III: Load combination relating only to tension in prestressed concrete superstructures with the objective of crack control.

• Service IV: Load combination relating only to tension in prestressed concrete columns with the objective of crack control.

Load Combination Descriptions

• Fatigue: Fatigue and fracture load combination relating to repetitive gravitational vehicular live load and dynamic responses under a single design truck.

Load Combination Descriptions