Geotechnical Related Development and Implementation of Load and Resistance Factor Design (LRFD) Methods
Geotechnical Related Development and Implementation of Load and Resistance Factor Design (LRFD) Methods

Author: George G. Goble

Publisher: Transportation Research Board

Published: 1999

Total Pages: 80

ISBN-13: 9780309068543

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This synthesis report will be of interest to geotechnical, structural, and bridge engineers, especially those involved in the development and implementation of the geotechnical aspects of the AASHTO Bridge Code. The synthesis documents a review of geotechnical related LRFD specifications and their development worldwide to compare them with the current AASHTO LRFD Bridge Code. Design procedures for foundations, earth retaining structures, and culverts are summarized and compared with the methods specified by the AASHTO code. This TRB report provides information designed to assist engineers in implementing the geotechnical features of LRFD methods. Information for the synthesis was collected by surveying U.S. and Canadian transportation agencies and by conducting a literature search using domestic and international sources. Interviews were also conducted with selected international experts. The limited available experience in the United States and information from international practice are discussed to understand the problems that have arisen in order that solutions may be found. Based on the studies reported here, suggestions for improving the code are identified.

LRFD Pullout Resistance Factor Calibration for Soil Nails Incorporating Survival Analysis and PLAXIS 2D
LRFD Pullout Resistance Factor Calibration for Soil Nails Incorporating Survival Analysis and PLAXIS 2D

Author: Brett DeVries

Publisher:

Published: 2013

Total Pages:

ISBN-13:

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The use of soil nail walls (SNWs) in the United States has increased since their introduction in the mid-1970's, to where currently the analysis, design and construction are commonly performed (Lazarte, 2011). These SNW designs were mostly based on ASD methods and LRFD-based methodologies were lacking until the 1998 FHWA manual on SNW design (Byrne, Cotton, Porterfield, Wolschlag and Ueblacker, 1998), which provided uncalibrated resistance factors developed from ASD safety factors. As a result, little improvement was made toward a more efficient design, until fully calibrated LRFD pullout resistance factors were provided in the NCHRP Report 701 (Lazarte, 2011). These pullout resistance factors were calibrated with a variety of load factors commonly used for retaining structures as part of a bridge substructure. Although fully calibrated resistance factors were calculated, the predicted pullout resistance was not based a specific design procedure, but rather on multiple design procedures (Lazarte, 2011). The main objective of this study was to achieve a greater understanding of the bond strength of soil nails in North Dallas Texas. In an effort to accomplish this objective, pullout resistance factors were calibrated for cohesive soils within the project location. Pullout resistances were determined using creep test data, field observations, and methods commonly used in tension piles. This resulted in 25 cases that met failure criteria out of the 47 verification tests conduction in cohesive soil for the LBJ Express construction project. Statistical analysis was conducted to evaluate the predicted to measured pullout resistance for the failed tests, and Survival Analysis was utilized to incorporate the non-failed tests. In addition, PLAXIS 2D was used to fit a finite element model to testing results and used to predict failure in three cases. Results from analysis test results, Survival Analysis and PLAXIS 2D were combined with the 25 failed cases along with soil nail testing results found in the NCHRP Report 701. Five soil nail databases were established from these results and utilized in the remainder of the study. Then, LRFD reliability analysis using Monte Carlo simulations were performed to calibrate pullout resistance factors at a target reliability index of 2.33 and load factors of 1, 1.35, 1.5, 1.6 and 1.75. The final step involved incorporating SNAILZ to compare the required soil nail length between the existing design method and the calibrated resistance factors for a typical SNW.

Design of Highway Bridges
Design of Highway Bridges

Author: Richard M. Barker

Publisher: John Wiley & Sons

Published: 2013-02-04

Total Pages: 1194

ISBN-13: 1118330102

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Up-to-date coverage of bridge design and analysis revised to reflect the fifth edition of the AASHTO LRFD specifications Design of Highway Bridges, Third Edition offers detailed coverage of engineering basics for the design of short- and medium-span bridges. Revised to conform with the latest fifth edition of the American Association of State Highway and Transportation Officials (AASHTO) LRFD Bridge Design Specifications, it is an excellent engineering resource for both professionals and students. This updated edition has been reorganized throughout, spreading the material into twenty shorter, more focused chapters that make information even easier to find and navigate. It also features: Expanded coverage of computer modeling, calibration of service limit states, rigid method system analysis, and concrete shear Information on key bridge types, selection principles, and aesthetic issues Dozens of worked problems that allow techniques to be applied to real-world problems and design specifications A new color insert of bridge photographs, including examples of historical and aesthetic significance New coverage of the "green" aspects of recycled steel Selected references for further study From gaining a quick familiarity with the AASHTO LRFD specifications to seeking broader guidance on highway bridge design Design of Highway Bridges is the one-stop, ready reference that puts information at your fingertips, while also serving as an excellent study guide and reference for the U.S. Professional Engineering Examination.