Side Resistance Factor for Serviceability-Based Design of Drilled Shafts in Weak Rock Calibrated Using O-Cell Test Data

2009 ◽  
Author(s):  
Jie Han ◽  
Xiao-Ming Yang ◽  
Robert L. Parsons ◽  
Robert W. Henthorne
Keyword(s):  
Test Data ◽  
Drilled Shafts ◽  
Resistance Factor ◽  
Weak Rock ◽  
Side Resistance ◽  
Cell Test

Resistance Factors for Drilled Shafts in Weak Rock Based on O-Cell Test Data

2008 ◽  
Vol 2045 (1) ◽  
pp. 62-67 ◽  
Author(s):  
Xiaoming Yang ◽  
Jie Han ◽  
Robert L. Parsons ◽  
Robert W. Henthorne
Keyword(s):  
Test Data ◽  
Drilled Shafts ◽  
Rock Properties ◽  
Weak Rock ◽  
Foundation Design ◽  
Resistance Factors ◽  
Side Resistance ◽  
Measured Resistance ◽  
Log Normal ◽  
Load And Resistance Factor

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.

Statistical Analysis of O-Cell Test Data for Nominal Load Capacities of Drilled Shafts

2008 ◽  
Author(s):  
Xiaoming Yang ◽  
Jie Han ◽  
Robert Henthorne ◽  
Robert L. Parsons
Keyword(s):  
Statistical Analysis ◽  
Test Data ◽  
Drilled Shafts ◽  
Cell Test ◽  
Nominal Load

Field P–y curves in weathered rock

2007 ◽  
Vol 44 (7) ◽  
pp. 753-764 ◽  
Author(s):  
Kook Hwan Cho ◽  
Mohammed A Gabr ◽  
Shane Clark ◽  
Roy H Borden
Keyword(s):  
Field Tests ◽  
Drilled Shafts ◽  
Drilled Shaft ◽  
Weak Rock ◽  
Strain Gages ◽  
Weathered Rock ◽  
Clay Model ◽  
Rock Model ◽  
Stiff Clay ◽  
Subgrade Modulus

In weathered and decomposed rock profiles, the lack of an acceptable analysis procedure for estimating lateral load–displacement response of drilled shafts is compounded by the unavailability of weathered material properties, including the material's lateral subgrade reaction modulus. Such deficiency often leads to the overdesign of the drilled shaft foundation. Six field tests were conducted on drilled shafts to investigate the shape and magnitude of P–y curves in weathered rock material at three locations in North Carolina. The tested shafts were instrumented using dial gages, strain gages, and continuous vertical inclinometers. The measured load versus deflection data are used to study the stiffness response of weathered rock. Measured lateral responses are compared with the results estimated based on a "weak rock" model and a stiff clay model. The comparison shows that Reese's weak rock model overestimated the resistances of the tested shafts while the stiff clay model consistently underestimated the measured shaft resistances. The measured and computed results are analyzed and discussed.Key words: drilled shaft, weathered rock P–y curve, subgrade modulus, ultimate resistances in weathered rock, verification tests.

scholarly journals Load and resistance factor design of drilled shafts subjected to lateral loading at service limit state

2018 ◽  
Author(s):  
◽  
Minh Dinh Uong
Keyword(s):  
Limit State ◽  
Design Procedure ◽  
Drilled Shafts ◽  
Resistance Factor ◽  
Lateral Loading ◽  
Drilled Shaft ◽  
Resistance Factors ◽  
Service Limit State ◽  
Load And Resistance Factor ◽  
Aashto Lrfd

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.

scholarly journals Evaluation of Unit Side Resistance of Drilled Shafts by Revised SPT N Value

2013 ◽  
Vol 29 (12) ◽  
pp. 5-10
Author(s):  
Min-Seung Yoon ◽  
Chea-Keon Lee ◽  
Myung-Hak Kim
Keyword(s):  
Drilled Shafts ◽  
N Value ◽  
Side Resistance ◽  
Spt N Value
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