Structural Resistance Factors for Drilled Shafts Considering Construction Flaws

Author(s):  
Michael W. O'Neill ◽  
Hazem A. Sarhan
2018 ◽  
Author(s):  
◽  
Minh Dinh Uong

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.


Author(s):  
Rozbeh Moghaddam

This study presents the development and calibration of resistance factors for the serviceability limit state (SLS) condition (φSLS) used in the load and resistance factor design (LRFD) of deep foundations. The performance function was established based on load corresponding to tolerable displacement (Qδtol) and design load (Qd). A dataset of published full-scale load tests including projects from Texas, Missouri, Arkansas, Louisiana, and New Mexico was compiled and consisted of 60 load test cases comprising 33 driven piles and 27 drilled shafts. Resistance factors for SLS conditions were calibrated for tolerable displacements using both the Monte Carlo simulation (MCS) and the First Order Second Moment (FOSM) approaches. From the calibration study, resistance factors at SLS conditions were obtained ranging from 0.33 to 0.62 using FOSM method and 0.37 to 0.67 using the MCS for driven piles. In the case of drilled shafts, SLS resistance factors ranged from 0.37 to 0.77 following the FOSM method and 0.41 to 0.86 based on MCS.


Author(s):  
Xiaoming Yang ◽  
Jie Han ◽  
Robert L. Parsons ◽  
Robert W. Henthorne

Load and resistance factor design (LRFD) has been mandatory for all FHWA-funded bridges since October 2007. The resistance factors included in the current AASHTO specifications for foundation design are not all calibrated by using field data. A calibration of resistance factors for side resistance of drilled shafts in weak rock is based on the statistical data collected from 19 O-cell tests in the midwestern United States. The field test data were used to determine the measured resistance, and the in situ rock properties and the dimensions of drilled shafts were used to calculate the predicted resistance by using the FHWA method. The Monte Carlo method was selected to perform the calibration. On the basis of the normally distributed loads and log normal distributed resistance from the test data, side resistance factors were determined at a target reliability index of 3.0. The calibrated resistance factors were compared with those in the current AASHTO LRFD Bridge Design Specifications.


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