LRFD Design and Construction of Shallow Foundations for Highway Bridge Structures

SUMMARY

LRFD Design and Construction of

Shallow Foundations for Highway

Bridge Structures

NCHRP Project 24-31, “LRFD Design Specifications for Shallow Foundations” was initiated

with the objective to “develop recommended changes to Section 10 of the AASHTO

LRFD

Bridge Design Specifications

for the strength limit state design of shallow foundations.”

The AASHTO specifications are traditionally observed on all federally aided projects and are

generally viewed as the national code of U.S. highway practice; hence, they influence the construction

of all foundations of highway bridges throughout the United States. This report

represents

the results of the studies and analyses conducted for NCHRP Project 24-31.

The current AASHTO specifications, as well as other existing codes employing reliabilitybased

design (RBD) principles, were calibrated using a combination of reliability theory, fitting

to allowable stress design (ASD) (also called working stress design [WSD]), and engineering

judgment. The main challenges of the project were, therefore, the compilation of

large, high-quality databases of tested foundations to failure and the development of a procedural

and data management framework that would enable Load and Resistance Factor

Design

(LRFD) parameter evaluation for the strength limit state of shallow foundations. The

presented

research is the first to introduce large-scale, RBD calibration of shallow foundations

utilizing databases.


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