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) has mandated the use of LRFD for all bridges for which the Texas Department of Transportation (TxDOT) initiates 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, 4th edition, which designers should adhere to unless directed otherwise by this document. Recommendations and examples are available on the TxDOT web site at: http://www.dot.state.tx.us/services/bridge/default.htm.

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.

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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 and steel-reinforced elastomeric bearings for prestressed concrete beams and strut-and-tie method.

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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.