Resistance Factors Calibrated from FHWA Drilled Shafts Static Top-Down Test Data Base

2009 ◽  
Author(s):  
Robert Liang ◽  
Jiliang Li
Keyword(s):  
Data Base ◽  
Test Data ◽  
Drilled Shafts ◽  
Top Down ◽  
Resistance Factors

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.

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.

Reliability Evaluation of AASHTO Design Equations for Drilled Shafts

1997 ◽  
Vol 1582 (1) ◽  
pp. 60-67
Author(s):  
William M. Isenhower ◽  
James H. Long
Keyword(s):  
Data Base ◽  
Reliability Evaluation ◽  
Drilled Shafts ◽  
Drilled Shaft ◽  
Factors Affecting ◽  
First Order ◽  
Axial Capacity ◽  
Moment Methods ◽  
First Order Second Moment ◽  
Load Tests

A reliability evaluation of the AASHTO design equations for drilled shafts is described. The evaluation computed the variance of a data base containing load tests to failure on 30 straight-sided drilled shafts using first-order, second-moment methods applied to the AASHTO design equations. The computed variance was compared with the measured variance of the data base. The measured variance was found to exceed the computed variance for approximately 75 percent of the load tests. This is believed to result from important factors affecting the axial capacity of the drilled shaft not being included in the AASHTO design equations. It is speculated that the missing factors are related to common variations in construction practices for drilled shafts.

Evaluation of peak side resistance for rock socketed shafts in weak sedimentary rock from an extensive database of published field load tests: a limit state approach

2019 ◽  
Vol 56 (12) ◽  
pp. 1816-1831 ◽  
Author(s):  
Pouyan Asem ◽  
Paolo Gardoni
Keyword(s):  
Test Data ◽  
Limit State ◽  
Deformation Modulus ◽  
Load Test ◽  
Resistance Factors ◽  
Strength Limit ◽  
Side Resistance ◽  
Load Tests ◽  
Load And Resistance Factor

This paper presents analyses of the measured peak side resistance of rock sockets constructed in weak claystone, shale, limestone, siltstone, and sandstone. The peak side resistance is obtained from in situ axial load tests on drilled shafts, anchors, and plugs. The parameters that affect the development of peak side resistance are determined using in situ load test data. It is found that peak side resistance increases with the unconfined compressive strength and deformation modulus of the weak rock, and decreases with the increase in length of the shear surface along the rock socket sidewalls. The increase in socket diameter also slightly decreases the peak side resistance. Additionally, it is found that the initial normal stresses do not significantly affect the measured peak side resistance in the in situ load tests. The in situ load test data are used to develop an empirical design equation for determination of the peak side resistance. The proposed model for peak side resistance and the reliability analysis are used to determine the corresponding resistance factors for use in the load and resistance factor design framework for assessment of the strength limit state.

Sign in / Sign up

Export Citation Format

Share Document