Presenation-ASSHTO LRFD

7/27/2019 Presenation-ASSHTO LRFD

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AASHTOLOAD AND RESISTANCE FACTOR

“LRFD”BRIDGE DESIGN

SPECIFICATIONS



LRFD IMPLEMENTATION

BYOHIO 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.




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 thespecifications and software

for these structures are

"mature" at this time.




3. States unable to meet these

dates will provide

justification and a schedulefor completing the

transition to LRFD.




4. For modifications to

existing structures, States

would have the option of using LRFD Specifications

or the specifications which

were used for the originaldesign.



1. Major Projects as defined by the

PDP – Projects starting Step 6after July 20, 2007 shall have

the structures designed using the

LRFD Bridge Specifications.

2. Minor Projects as defined by thePDP – Projects starting Step 3

after July 20, 2007 shall have

the structures designed using theLRFD 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 andthe 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 rehabilitationof existing structures should be in

accordance with the AASHTO Standard

Specifications for Highway Bridges, 17thEdition, and the ODOT Bridge Design

Manual.



This commitment does not apply to the

rehabilitation of existing structures. Until

further notice, the design for rehabilitationof existing structures should be in

accordance with the AASHTO Standard

Specifications for Highway Bridges, 17thEdition, 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.



ODOT

LOAD AND RESISTANCE

FACTOR DESIGN

TRAINING COURSES



LRFD Loads & General Overview



Steel Design

Reinforced Concrete Design

Prestressed Concrete Design



Foundation Design



ONLINE REGISTRATION



LRFD BRIDGE DESIGNSPECIFICATIONS

ANDTHE 2007 ODOT

BRIDGE DESIGN MANUAL



LISTS AND ADDRESSES

THE EXCEPTIONS TAKENBY THE OhioDOT TO THE

LRFD BRIDGE DESIGN

SPECIFICATIONS

BDM SECTION 1000:



LOADS, LOAD COMBINATIONS

ANDLIMIT 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 Loads

Load 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 Loads

Load Definitions



STANDARD SPECIFICATIONS LIVE LOAD MODEL



LRFD LIVE LOAD MODEL



EQ IC CT CV

Strength I γ p 1.75 1.00 --- --- 1.00 0.50/1.20 γ tg γ se --- --- --- ---

Strength II γ p 1.35 1.00 --- --- 1.00 0.50/1.20 γ tg γ se --- --- --- ---

Strength III γ p --- 1.00 1.40 --- 1.00 0.50/1.20 γ tg γ se --- --- --- ---

Strength IV --- 1.00 --- --- 1.00 0.50/1.20 --- --- --- --- --- ---

Strength V γ p 1.35 1.00 0.40 1.00 1.00 0.50/1.20 γ tg γ se --- --- --- ---

Ext Event I γ p γ eq 1.00 --- --- 1.00 --- --- --- 1.00 --- --- ---

Ext Event II γ p 0.50 1.00 --- --- 1.00 --- --- --- --- 1.00 1.00 1.00Service I 1.00 1.00 1.00 0.30 1.00 1.00 1.00/1.20 γ tg γ se --- --- --- ---

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 γ tg γ se --- --- --- ---

Service IV 1.00 --- 1.00 0.70 --- 1.00 1.00/1.20 --- 1.00 --- --- --- ---

Fatigue --- 0.75 --- --- --- --- --- --- --- --- --- --- ---

LL

IM

CEBR

PL

LS

DC

DD

DW

EHEV

ES

EL

Load

Combination FRWLWSWA

Use One of These at a Time

SETG

TU

CR

SH

Load Combinations and Load Factors

γ p



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

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

• Strength III: Load combination relating to the bridge exposed towind 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 usewith 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 certainhydraulic events with a reduced live load.




• Service I: Load combination relating to normal operationaluse of the bridge with a 55 mph wind and allloads at nominal values.

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

• Service III: Load combination relating only to tension inprestressed concrete superstructures with theobjective of crack control.

• Service IV: Load combination relating only to tension inprestressed concrete columns with theobjective of crack control.




• Fatigue: Fatigue and fracture load combination relating to

repetitive gravitational vehicular live load and

dynamic responses under a single design truck.


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