This research study is aimed at assisting the Texas Department of Transportation
(TxDOT) in making a transition from the use of the AASHTO Standard Specifications
for Highway Bridges to the AASHTO LRFD Bridge Design Specifications for the design
of prestressed concrete bridges. It was identified that Type C and AASHTO Type IV are
among the most common girder types used by TxDOT for prestressed concrete bridges.
This study is specific to these two types of bridges. Guidelines are provided to tailor
TxDOT's design practices to meet the requirements of the LRFD Specifications.
Detailed design examples for an AASHTO Type IV girder using both the
AASHTO Standard Specifications and AASHTO LRFD Specifications are developed
and compared. These examples will serve as a reference for TxDOT bridge design
engineers. A parametric study for AASHTO Type IV and Type C girders is conducted
using span length, girder spacing, and strand diameter as the major parameters that are
varied. Based on the results obtained from the parametric study, two critical areas are
identified where significant changes in design results are observed when comparing
Standard and LRFD designs. The critical areas are the transverse shear requirements and
interface shear requirements, and these are further investigated.
The interface shear reinforcement requirements are observed to increase
significantly when the LRFD Specifications are used for design. New provisions for
interface shear design that have been proposed to be included in the LRFD
Specifications in 2007 were evaluated. It was observed that the proposed interface shear
provisions will significantly reduce the difference between the interface shear
reinforcement requirements for corresponding Standard and LRFD designs.The transverse shear reinforcement requirements are found to be varying
marginally in some cases and significantly in most of the cases when comparing LRFD
designs to Standard designs. The variation in the transverse shear reinforcement
requirement is attributed to differences in the shear models used in the two
specifications. The LRFD Specifications use a variable truss analogy based on the
Modified Compression Field Theory (MCFT). The Standard Specifications use a
constant 45-degree truss analogy method for its shear design provisions. The two
methodologies are compared and major differences are noted.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/4841 |
| Date | 25 April 2007 |
| Creators | Mohammed, Safiuddin Adil |
| Contributors | Hueste, Mary Beth D. |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Thesis, text |
| Format | 2805584 bytes, electronic, application/pdf, born digital |
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