Calibration Of Resistance Factors For Drilled Shafts For The New Fhwa Design Method
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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.
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.
Development Of Recommended Resistance Factors For Drilled Shafts In Weak Rocks Based On O Cell Tests
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Author : Xiaoming Yang (Writer on geotechnical engineering)
language : en
Publisher:
Release Date : 2010
Development Of Recommended Resistance Factors For Drilled Shafts In Weak Rocks Based On O Cell Tests written by Xiaoming Yang (Writer on geotechnical engineering) 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.
From October 1, 2007, the new bridges on federal-aid funded projects are mandated to be designed to meet American Association of State Highway and Transportation Officials (AASHTO) Load and Resistance Factor Design (LRFD) Bridge Design Specifications. LRFD is a simplified form of reliability-based design. By multiplying calibrated factors to load and resistance components, the designed structure will maintain a specific level of reliability (or probability of failure). By concept, the load and resistance factors should be calibrated by large number of test data; however, they are often unavailable in geotechnical engineering. Significant efforts are needed to calibrate load and resistance factors based on test data of good quality. In this study, 26 O-Cell test data were collected from Kansas, Colorado, Missouri, Ohio, and Illinois. Seven methods available in the literature were selected to estimate the load capacities of 25 out of 26 drilled shafts. The "FHWA 0.05D" method was found to yield the closest and conservative predictions of the nominal resistances to the representative values; therefore, it was adopted in this study when calibrating the resistance factors for Strength Limit State design. These test data were analyzed and used to calibrate side and base resistance factors for drilled shafts in weak rock. Resistance factors were calibrated at two different target reliability indices: 2.3 (i.e., failure probability, Pf ~ 1/100) for shafts with greater redundancy and 3.0 (Pf ~ 1/1000) for shafts with less redundancy. Side resistance factors were calibrated from two different datasets of measured resistance: total side resistance and layered unit side resistance. The resistance factors calibrated from layered unit side resistance are considered more reliable, therefore, they are recommended for design. The recommended resistance factors from this study are compared with those in AASHTO specifications. Some of those calibrated resistance factors from this study are considerably lower than those in AASHTO specifications. The main reasons for such lower resistance factors are mainly attributed to the low efficiency of the FHWA design method and the limited quality and number of O-Cell test data. These resistance factors may be improved by increasing the size and the quality of the test data in the future. At present, field load tests on drilled shafts are recommended as an alternative to using lower resistance factors, which will also accumulate more test data for future improvement.
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.
Advances In Analysis And Design Of Deep Foundations
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Author : Murad Abu-Farsakh
language : en
Publisher: Springer
Release Date : 2017-07-11
Advances In Analysis And Design Of Deep Foundations written by Murad Abu-Farsakh and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017-07-11 with Science categories.
This volume on “Advances in Analysis and Design of Deep Foundations” contains 22 technical papers which cover various aspects of analysis and design of deep foundations based on full-scale field testing, numerical modeling, and analytical solutions. The technical papers are 8-10 pages long that present the results and findings from research as well as practical-oriented studies on deep foundations that are of interest to civil/geotechnical engineering community. The topics cover a wide spectrum of applications that include evaluation of the axial and lateral capacity of piles, pile group effects, evaluation of the increase in pile capacity with time (or pile setup), influence of excavation on pile capacity, study the behavior of pile raft caisson foundations, evaluate the bearing capacity and settlement of piles from cone penetration tests, etc. This volume is part of the proceedings of the 1st GeoMEast International Congress and Exhibition on Sustainable Civil Infrastructures, Egypt 2017.
Geotechnical Engineering In The Digital And Technological Innovation Era
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Author : Alessio Ferrari
language : en
Publisher: Springer Nature
Release Date : 2023-06-16
Geotechnical Engineering In The Digital And Technological Innovation Era written by Alessio Ferrari and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023-06-16 with Science categories.
The book collects the keynote contributions and the papers presented at the “8th Italian Conference of Researchers in Geotechnical Engineering 2023, CNRIG’23”. The conference was held on July 5–7, 2023, at the University of Palermo (Italy), and it was organized under the auspices of the National Group of Geotechnical Engineering (GNIG). The event has been organized to promote interaction among geotechnical engineering and applied sciences, with special focus on technological and digital innovations. The book covers a wide range of classical and emerging topics in geotechnics, including innovation in laboratory testing and in situ monitoring, thermo-hydro-chemo-mechanical behavior of geo-materials, computational geomechanics, analyses of instability processes in seismic conditions, probabilistic approaches, resilience of critical infrastructures and advances in risk mitigation strategies, and eco-friendly solutions for soils and rocks stabilization. This book is intended for postgraduate students, researchers, and practitioners working on geotechnical engineering and related areas.
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.
Modern Geotechnical Design Codes Of Practice
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Author : Patrick Arnold
language : en
Publisher: IOS Press
Release Date : 2013
Modern Geotechnical Design Codes Of Practice written by Patrick Arnold and has been published by IOS Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2013 with Science categories.
The ground is one of the most highly variable of engineering materials. It is therefore not surprising that geotechnical designs depend on local site conditions and local engineering experience. Engineering practices, relating to investigation and design methods site understanding and to safety levels acceptable to society, will therefore vary between different regions.The challenge in geotechnical engineering is to make use of worldwide geotechnical experience, established over many years, to aid in the development and harmonization of geotechnical design codes. Given the significant uncertainties involved, empiricism and engineering
Load And Resistance Factor Design Lrfd For Deep Foundations
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Author : Samuel G. Paikowsky
language : en
Publisher: Transportation Research Board
Release Date : 2004
Load And Resistance Factor Design Lrfd For Deep Foundations written by Samuel G. Paikowsky and has been published by Transportation Research Board this book supported file pdf, txt, epub, kindle and other format this book has been release on 2004 with Bridges categories.
Introduction and research approach -- Findings -- Interpretation, appraisal, and applications -- Conclusions and suggested research -- Bibliography -- Appendixes.
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.