Evaluation Of Model Uncertainties In Lrfd Calibration Process Of Drilled Shaft Axial Design
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Evaluation Of Model Uncertainties In Lrfd Calibration Process Of Drilled Shaft Axial Design
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Author : Mohammad Rakib Hasan
language : en
Publisher:
Release Date : 2019
Evaluation Of Model Uncertainties In Lrfd Calibration Process Of Drilled Shaft Axial Design written by Mohammad Rakib Hasan and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019 with Calibration categories.
The Federal Highway Administration (FHWA) released a policy in 2000 that required all new federally funded bridges to be designed using the AASHTO LRFD specifications by October 2007. The transition from ASD to LRFD posed a challenge due to the lack of area specific resistance factors. Though several studies were performed to calibrate area specific resistance factors, they did not improve from the resistance factors suggested in AASHTO 2012. The objective of this study is to analyze the uncertainties in LRFD calibration and to calibrate more accurate and improved resistance factors. A drilled shaft load test database from Mississippi and Louisiana has been selected to carry on the research. Osterberg Cell load test was a majority among the load tests in the database. Extrapolation is required in most Osterberg cell load test which may cause errors in the calibration. An analysis of the error due to the extrapolation can result in more accurate LRFD calibration of resistance factors. The analysis was performed on 8 drilled shaft cases from Louisiana and Mississippi. 4 of the 8 drilled shafts reached 5% of the shaft diameter(D) failure criterion and 4 of the drilled shafts were close to 5%D. For each of the cases,extrapolation was performed on tip and side resistance curves to get the equivalent top-down curve. Data points were removed systematically from the end of top and bottom movement curves and extrapolation was performed for each trial to get an equivalent top-down curve. Bias and error values was measured for each of the trial top down scurves for both 5% of the drilled shaft diameter(D). 80 extrapolation cases were achieved from this analysis. Finally, multiple linear regression analysis was performed on the extrapolated data set in order to reduce the effect of the extrapolation error on the resistance factor. Applying bounded bias distribution may also result in more accurate resistance factors, since the bias values have significant role in the calibration process. As the probability of failure significantly depends on the lower tail of the distribution of the resistance values and there is a physical presence of a lower limit of the resistance of a drilled shaft, introducing a lower bound to the resistance distribution will ensure more realistic calibration of the resistance factors. An analysis by simulation of load tests to failure on will also help to understand the reasons for low resistance factor values. The objective of this study is also to minimize effect of extrapolation by means of finite element modelling of the bidirectional load tests included in a database collected from Louisiana and Mississippi. The finite element modelling was performed in PLAXIS 2D until the top and the bottom movement curves reach the measured loads corresponding to the failure criteria. LRFD calibration of resistance factors was performed based on the simulated bidirectional load test database and the results were compared to the results from conventional approach.
Model Uncertainties In Foundation Design
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Author : Chong Tang
language : en
Publisher: CRC Press
Release Date : 2021-03-17
Model Uncertainties In Foundation Design written by Chong Tang and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2021-03-17 with Technology & Engineering categories.
Model Uncertainties in Foundation Design is unique in the compilation of the largest and the most diverse load test databases to date, covering many foundation types (shallow foundations, spudcans, driven piles, drilled shafts, rock sockets and helical piles) and a wide range of ground conditions (soil to soft rock). All databases with names prefixed by NUS are available upon request. This book presents a comprehensive evaluation of the model factor mean (bias) and coefficient of variation (COV) for ultimate and serviceability limit state based on these databases. These statistics can be used directly for AASHTO LRFD calibration. Besides load test databases, performance databases for other geo-structures and their model factor statistics are provided. Based on this extensive literature survey, a practical three-tier scheme for classifying the model uncertainty of geo-structures according to the model factor mean and COV is proposed. This empirically grounded scheme can underpin the calibration of resistance factors as a function of the degree of understanding – a concept already adopted in the Canadian Highway Bridge Design Code and being considered for the new draft for Eurocode 7 Part 1 (EN 1997-1:202x). The helical pile research in Chapter 7 was recognised by the 2020 ASCE Norman Medal.
Calibration Of Resistance Factors For Drilled Shafts For The New Fhwa Design Method
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Author : Murad Yusuf Abu-Farsakh
language : en
Publisher:
Release Date : 2013
Calibration Of Resistance Factors For Drilled Shafts For The New Fhwa Design Method written by Murad Yusuf Abu-Farsakh and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with Load factor design categories.
As a continuing effort to implement the Load and Resistance Factor Design (LRFD) design methodology for deep foundations in Louisiana, this report will present the reliability-based analyses for the calibration of the resistance factor for LRFD design of axially loaded drilled shafts using Brown et al. method (2010 FHWA design method). Twenty-six drilled shaft tests collected from previous research (LTRC Final Report 449) and eight new drilled shaft tests were selected for statistical reliability analysis; the predictions of total, side, and tip resistance versus settlement behavior of drilled shafts were established from soil borings using both 1999 FHWA design method (Brown et al. method) and 2010 FHWA design method (O'Neill and Reese method). The measured drilled shaft axial nominal resistance was determined from either the Osterberg cell (O-cell) test or the conventional top-down static load test. For the 30 drilled shafts that were tested using O-cells, the tip and side resistances were deduced separately from test results. Statistical analyses were performed to compare the predicted total , tip, and side drilled shaft nominal axial resistance with the corresponding measured nominal resistance.
Load And Resistance Factor Design Of Drilled Shafts Subjected To Lateral Loading At Service Limit State
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Author : Minh Dinh Uong
language : en
Publisher:
Release Date : 2018
Load And Resistance Factor Design Of Drilled Shafts Subjected To Lateral Loading At Service Limit State written by Minh Dinh Uong and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018 with categories.
Since 2007, the American Association of State Highway Administration Officials (AASHTO) has made utilization of Load and Resistance Factor Design (LRFD) mandatory on all federally-funded new bridge projects (AASHTO, 2007). However, currently, there are no guidelines implementing LRFD techniques for design of drilled shaft subjected to lateral loads using reliability-based analysis. On a national level, the AASHTO LRFD Bridge Design Specifications (AASHTO, 2012) specify that a resistance factor of 1.0 be used for design of drilled shafts subjected to lateral loading at service limit state, which means reliability-based analyses for calibration of resistance factors have not been performed. Therefore, there is a need to create a LRFD procedure for drilled shafts subjected to lateral loading at service limit state that has reliability-based calibrated resistance factors applicable for future projects. The research focuses on the reliability-based analysis of drilled shaft subjected to lateral loading, characterize lateral load transfer model of drilled shafts in shale, probabilistic calibrate resistance factor and contribute to the development of design procedure using LRFD. The objective of this work is to improve the design of drilled shaft subjected to lateral loading using LRFD at service limit state by providing a more reliable design procedure than the current AASHTO LRFD procedure for drilled shafts subjected to lateral loading at service limit state.
Calibration Of Resistance Factors Needed In The Lrfd Design Of Drilled Shafts
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Author : Alicia Rae Fortier
language : en
Publisher:
Release Date : 2016
Calibration Of Resistance Factors Needed In The Lrfd Design Of Drilled Shafts written by Alicia Rae Fortier and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016 with categories.
Development Of A Database For Drilled Shaft Foundation Testing Dshaft
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Author : Jessica A. Garder
language : en
Publisher:
Release Date : 2012
Development Of A Database For Drilled Shaft Foundation Testing Dshaft written by Jessica A. Garder and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with Bridges categories.
Drilled shafts have been used in the US for more than 100 years in bridges and buildings as a deep foundation alternative. For many of these applications, the drilled shafts were designed using the Working Stress Design (WSD) approach. Even though WSD has been used successfully in the past, a move toward Load Resistance Factor Design (LRFD) for foundation applications began when the Federal Highway Administration (FHWA) issued a policy memorandum on June 28, 2000.The policy memorandum requires all new bridges initiated after October 1, 2007, to be designed according to the LRFD approach. This ensures compatibility between the superstructure and substructure designs, and provides a means of consistently incorporating sources of uncertainty into each load and resistance component. Regionally-calibrated LRFD resistance factors are permitted by the American Association of State Highway and Transportation Officials (AASHTO) to improve the economy and competitiveness of drilled shafts. To achieve this goal, a database for Drilled SHAft Foundation Testing (DSHAFT) has been developed. DSHAFT is aimed at assimilating high quality drilled shaft test data from Iowa and the surrounding regions, and identifying the need for further tests in suitable soil profiles. This report introduces DSHAFT and demonstrates its features and capabilities, such as an easy-to-use storage and sharing tool for providing access to key information (e.g., soil classification details and cross-hole sonic logging reports). DSHAFT embodies a model for effective, regional LRFD calibration procedures consistent with PIle LOad Test (PILOT) database, which contains driven pile load tests accumulated from the state of Iowa. PILOT is now available for broader use at the project website: http://srg.cce.iastate.edu/lrfd/. DSHAFT, available in electronic form at http://srg.cce.iastate.edu/dshaft/, is currently comprised of 32 separate load tests provided by Illinois, Iowa, Minnesota, Missouri and Nebraska state departments of transportation and/or department of roads. In addition to serving as a manual for DSHAFT and providing a summary of the available data, this report provides a preliminary analysis of the load test data from Iowa, and will open up opportunities for others to share their data through this quality-assured process, thereby providing a platform to improve LRFD approach to drilled shafts, especially in the Midwest region
Calibration Of Resistance Factors Needed In The Lrfd Design Of Drilled Shafts
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Author : Murad Yusuf Abu-Farsakh
language : en
Publisher:
Release Date : 2010
Calibration Of Resistance Factors Needed In The Lrfd Design Of Drilled Shafts written by Murad Yusuf Abu-Farsakh and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with Load factor design categories.
Development Of A Database For Drilled Shaft Foundation Testing Dshaft
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Author : Jessica A. Garder
language : en
Publisher:
Release Date : 2012
Development Of A Database For Drilled Shaft Foundation Testing Dshaft written by Jessica A. Garder and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with Bridges categories.
Drilled shafts have been used in the US for more than 100 years in bridges and buildings as a deep foundation alternative. For many of these applications, the drilled shafts were designed using the Working Stress Design (WSD) approach. Even though WSD has been used successfully in the past, a move toward Load Resistance Factor Design (LRFD) for foundation applications began when the Federal Highway Administration (FHWA) issued a policy memorandum on June 28, 2000.The policy memorandum requires all new bridges initiated after October 1, 2007, to be designed according to the LRFD approach. This ensures compatibility between the superstructure and substructure designs, and provides a means of consistently incorporating sources of uncertainty into each load and resistance component. Regionally-calibrated LRFD resistance factors are permitted by the American Association of State Highway and Transportation Officials (AASHTO) to improve the economy and competitiveness of drilled shafts. To achieve this goal, a database for Drilled SHAft Foundation Testing (DSHAFT) has been developed. DSHAFT is aimed at assimilating high quality drilled shaft test data from Iowa and the surrounding regions, and identifying the need for further tests in suitable soil profiles. This report introduces DSHAFT and demonstrates its features and capabilities, such as an easy-to-use storage and sharing tool for providing access to key information (e.g., soil classification details and cross-hole sonic logging reports). DSHAFT embodies a model for effective, regional LRFD calibration procedures consistent with PIle LOad Test (PILOT) database, which contains driven pile load tests accumulated from the state of Iowa. PILOT is now available for broader use at the project website: http://srg.cce.iastate.edu/lrfd/. DSHAFT, available in electronic form at http://srg.cce.iastate.edu/dshaft/, is currently comprised of 32 separate load tests provided by Illinois, Iowa, Minnesota, Missouri and Nebraska state departments of transportation and/or department of roads. In addition to serving as a manual for DSHAFT and providing a summary of the available data, this report provides a preliminary analysis of the load test data from Iowa, and will open up opportunities for others to share their data through this quality-assured process, thereby providing a platform to improve LRFD approach to drilled shafts, especially in the Midwest region
Uncertainty Modeling And Decision Making In Geotechnics
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Author : Kok-Kwang Phoon
language : en
Publisher: CRC Press
Release Date : 2023-12-11
Uncertainty Modeling And Decision Making In Geotechnics written by Kok-Kwang Phoon and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023-12-11 with Technology & Engineering categories.
Uncertainty, Modeling, and Decision Making in Geotechnics shows how uncertainty quantification and numerical modeling can complement each other to enhance decision-making in geotechnical practice, filling a critical gap in guiding practitioners to address uncertainties directly. The book helps practitioners acquire a working knowledge of geotechnical risk and reliability methods and guides them to use these methods wisely in conjunction with data and numerical modeling. In particular, it provides guidance on the selection of realistic statistics and a cost-effective, accessible method to address different design objectives, and for different problem settings, and illustrates the value of this to decision-making using realistic examples. Bringing together statistical characterization, reliability analysis, reliability-based design, probabilistic inverse analysis, and physical insights drawn from case studies, this reference guide from an international team of experts offers an excellent resource for state-of-the-practice uncertainty-informed geotechnical design for specialist practitioners and the research community.
Drilled Shafts
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Author : Michael W. O'Neill
language : en
Publisher:
Release Date : 1999
Drilled Shafts written by Michael W. O'Neill and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1999 with Foundations categories.