Chapter 1: About this Manual

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Section 1: Introduction

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Implementation

Load and Resistance Factor Design (LRFD) is a design methodology that makes use of load and resistance factors based on the known variability of applied loads and material properties. In 1994, the American Association of State Highway and Transportation Officials (AASHTO) published the first AASHTO Load and Resistance Factor Bridge Design Specifications. The Federal Highway Administration (FHWA) mandated the use of LRFD for all bridges for which the Texas Department of Transportation (TxDOT) initiated preliminary engineering after October 2007.

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Purpose

This manual documents policy on bridge design in Texas. It assists Texas bridge designers in applying provisions documented in the AASHTO LRFD Bridge Design Specifications, 2014, 7th Edition with Interims, which designers should adhere to unless directed otherwise by this document. Recommendations and examples are available on the TxDOT website.

All Articles, Equations, and Tables referenced in this manual are from the current AASHTO LRFD Bridge Design Specifications, unless noted otherwise.

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Updates

Updates to this manual are summarized in the following table.

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Version

Publication Date

Summary of Changes

2005-1

July 2005

New manual

2005-2

September 2005

Revision adding information on deck slabs on slab beams, double-tee beams, and box beams. Also added information on prestressed slab beams, prestressed concrete double-tee beams, prestressed concrete box beams, and cast-in-place concrete slab and girder spans (pan forms).

2006-1

June 2006

Revision adding information on cast-in-place concrete spans, straight plate girders, and curved plate girders.

2006-2

July 2006

Revision adding information in Chapter 3 on prestressed concrete U beams (types U40 and U54) and on concrete deck slabs on U beams (types U40 and U54), and making minor adjustments to references in the Chapter 3 section on geometric constraints for steel-reinforced elastomeric bearings and to the Chapter 4 sections on design criteria for abutments and design criteria for inverted tee reinforced concrete bent caps.

2007-1

April 2007

Revisions to the design criteria for concrete deck slabs on stringers, cast-in-place concrete slab spans, rectangular reinforced concrete bent caps and inverted tee reinforced concrete bent caps. Revisions to the structural analysis of prestressed concrete I beams, U beams, slab beams and box beams (Types B20, B28, B34 and B40). Revisions to the geometric constraints for abutment and rectangular reinforced concrete bent caps. Revisions to the design recommendations for widenings.

2008-1

April 2008

Revisions to manual to conform with the 4th Edition of the AASHTO LRFD Bridge Design Specifications. Adds information in Chapter 5 for strut-and-tie design method. Revision to requirements for foundation load calculations. Revision to interface shear transfer requirements for prestressed beams. Clarifies policy on live load distribution factors for beam design. Revision to policy on debonding design. Corrects inverted tee design formulas.

2009-1

May 2009

Revisions to the manual to revise policy on foundation load calculations; revises policy on live load deflection check; revises policy on use of empirical design method for slab design; updates prestressed concrete design criteria; revises debonding limits for prestressed concrete design; adds requirements for considering corrosion protection measures; clarifies policy on bearing pad design; revises policy on calculating live load distribution factors for double-tee beams; and corrects minor editorial errors.

2010-1

September 2010

Revisions to the manual to revise policy on concrete deck slabs on stringers, minimum shear reinforcing for inverted tee bent caps and steel-reinforced elastomeric bearings.

2011-1

December 2011

Revisions to manual to update information in Chapter 2 regarding earthquake effects; add information in Chapter 3 regarding Concrete Deck Slabs on Spread Box Beams (X-Beams) and Prestressed Concrete Spread Box Beams (X-Beams); minor revisions in various chapters to reference current editions of publications.

2013-1

March 2013

Revisions to manual to conform to the 6th Edition of the AASHTO LRFD Bridge Design Specifications. Generally, revisions to manual to update information in Chapter 2 regarding vehicular collision force; add information in Chapter 3 regarding Segmental Spans; add upper limits on pretensioned girder concrete strength; add minimum number of beams in a roadway width; add overlay information for Decked Slab Beams; revise material grades and flange width for plate girders; add information in Chapter 4 regarding Post-tensioned Concrete Bent Caps; add minimum drilled shaft sizes; minor revisions in various chapters to reference current editions of publications; minor editorial revisions.

2015-1

October 2015

Revisions to manual to conform to the 7th Edition of the AASHTO LRFD Bridge Design Specifications with Interims. Generally, revisions to manual to update information in Chapter 2 regarding vehicular collision force; add information in Chapter 3 regarding Spliced Precast Girders; add information for Spread Slab Beams; revised deck design and detailing; revised minimum number of I-girders per span; added straight strand with debonding designs for pretensioned I-girders; revised prestress losses; added information in Chapter 4 regarding Columns for Single Column Bents or Piers; added grades higher than grade 60 reinforcement; added limits for service load cracking in straddle bent caps; removed 22 ksi limit for dead load stress; minor revisions in various chapters to reference current editions of publications; minor editorial revisions.



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Organization

The information in this manual is organized as follows:

  • Chapter 1, About this Manual. Introductory information on the purpose and organization of the manual.
  • Chapter 2, Limit States and Loads. General information on limit states and on load factors.
  • Chapter 3, Superstructure Design. Policy on LRFD design of specific bridge superstructure components.
  • Chapter 4, Substructure Design. Policy on LRFD design of specific bridge substructure components.
  • Chapter 5, Other Designs. Design guidelines for bridge widenings, steel-reinforced elastomeric bearings for pretensioned concrete beams, and strut-and-tie method. This chapter also addresses corrosion protection measures.
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Feedback

Direct any questions or comments on the content of the manual to the Director of the Bridge Division, Texas Department of Transportation.


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