Calibrating shaft and base resistance factors for design of drilled shaft foundations

2013 ◽  
pp. 2497-2505
Author(s):  
D Bach ◽  
M Hudson
Keyword(s):  
Drilled Shaft ◽  
Base Resistance ◽  
Resistance Factors ◽  
Drilled Shaft Foundations

scholarly journals Development of Rock Embedded Drilled Shaft Resistance Factors in Korea based on Field Tests

2019 ◽  
Vol 9 (11) ◽  
pp. 2201
Author(s):  
Seok Jung KIM ◽  
Sun Yong KWON ◽  
Jin Tae HAN ◽  
Mintaek YOO
Keyword(s):  
Design Method ◽  
Limit State ◽  
Field Tests ◽  
Load Test ◽  
Drilled Shaft ◽  
Displacement Curve ◽  
Base Resistance ◽  
Resistance Factors ◽  
Shaft Resistance ◽  
The Us

Load and resistance factor design (LRFD) is a limit state design method that has been applied worldwide. Because the data for determining LRFD factors in Korea has been insufficient, the resistance factors suggested by American Association of State Highway and Transportation Officials (AASHTO) in the US have been used for design in Korea; however, these resistance factors were defined based on the characteristics of the predominant bedrock types in the U.S. As such, it remains necessary to determine resistance factors that reflect the bedrock conditions in Korea. Accordingly, in this study, LRFD resistance factors were determined using 13 sets of drilled shaft load test data. To obtain accurate resistance factors, calibration of the elastic modulus of the drilled shaft and the equivalent load–displacement curve considering the axial load and elastic settlement was conducted. After determining accurate resistance values, a reliability analysis was performed. The resistance factors were determined to be within 0.13–0.32 of the AASHTO factors for the shaft resistance, 0.19–0.29 for the base resistance, and 0.28–0.42 for the total resistance. This is equivalent to being 30–60% of the AASHTO-recommended values for the shaft resistance and 40–60% of the AASHTO-recommended values for the base resistance. These differences in resistance factors were entirely the result of discrepancies in the conditions of the rock in the US and Korea in which the shafts were founded.

Safety Factor for Drilled Shaft Foundations Subjected to Wind-Induced Torsion

2020 ◽  
Vol 14 (1) ◽  
Author(s):  
Victor Aguilar
Keyword(s):  
Public Transportation ◽  
Probabilistic Approach ◽  
Drilled Shaft ◽  
Penetration Test ◽  
Statistical Parameters ◽  
Local Conditions ◽  
Resistance Factors ◽  
Vane Shear Test ◽  
Load And Resistance Factors ◽  
Drilled Shaft Foundations

Public transportation agencies commonly use drilled shaft foundations as support of mast arm traffic signs and signal pole structures. These structures and their foundations are subjected to wind-induced torsion. Design provisions can be found in AASHTO specifications for structural supports for highway signs, luminaires and traffic signals; nevertheless, those standards do not provide guidance to estimate the torsional resistance of drilled shaft foundations, or what an appropriate factor of safety (or resistance factor) for design could be. Although load and resistance factors format is desired because AASHTO is moving in that direction, still many Departments of Transportation design requirements are based on factors of safety. In this study, a probabilistic approach is used to recommend a rational procedure to determine factors of safety that consider the uncertainties and the consequences of failure. This procedure can be modified for load and resistance factors design calibration, as well. The skin friction approach was calibrated employing reliability analysis, available statistics, published experimental data, and simulations. However, a lack of field test data has been noticed. Factors of safety for cohesive, cohesionless, and layered soils are recommended. They are presented as a function of the target reliability index, and which in-situ test is performed to obtain the soil strength properties. Three alternatives were considered: standard penetration test, cone penetration test, and vane shear test. The procedure described can be used by practitioners to select appropriate factors of safety based on local conditions when statistical parameters from a particular site investigation are available.

Comparison of Measured and Predicted Skin Friction Values for Axially Loaded Drilled Shaft Foundations in Gravelly Soils

2005 ◽  
Author(s):  
Abdalla M. Harraz ◽  
William N. Houston ◽  
Kenneth D. Walsh ◽  
Courtland R. Perry ◽  
Sandra L. Houston
Keyword(s):  
Skin Friction ◽  
Drilled Shaft ◽  
Gravelly Soils ◽  
Axially Loaded ◽  
Drilled Shaft Foundations

Nondestructive Diagnosis of Drilled Shaft Foundations

1998 ◽  
Vol 1633 (1) ◽  
pp. 120-127 ◽  
Author(s):  
Larry D. Olson ◽  
Marwan F. Aouad ◽  
Dennis A. Sack
Keyword(s):  
Quality Assurance ◽  
The United States ◽  
Ultrasonic Waves ◽  
Drilled Shaft ◽  
Two Dimensional Image ◽  
Existing Structures ◽  
Advantages And Disadvantages ◽  
Ct Data ◽  
Drilled Shaft Foundations ◽  
Concrete Placement

Nondestructive methods based on propagation of sonic and ultrasonic waves are being used increasingly in the United States and internationally for forensic investigations of existing structures and for quality assurance of new construction. Of particular interest is the quality assurance of newly constructed drilled shaft foundations. Many state departments of transportation specify nondestructive testing of drilled shaft foundations, particularly for shafts drilled and placed under wet construction conditions. For quality assurance of drilled shaft foundations of bridges, the crosshole sonic logging (CSL) and sonic echo and impulse response (SE/IR) methods routinely are used. In the CSL method, access tubes are installed in the shaft before concrete placement. SE/IR measurements require that the top of the shaft be accessible after concrete placement. Proper test setups, specifications, and case studies are presented to illustrate the advantages and disadvantages of each of these methods. Also presented are recommendations for repair when a defect is identified in a drilled shaft foundation. The CSL method is more effective for locating defects. CSL measurements are effective for determining anomalies and defects between two access tubes. However, an accurate image of the defect cannot be determined from a CSL test alone. The crosshole tomography (CT) method uses multiple CSL logs with varying receiver locations to produce a two-dimensional image of the defect. The CT method is discussed and a dataset obtained from a drilled shaft foundation is presented. CT data collection and analysis require more time than the CSL method, and the CT method is used only for critical drilled shaft foundations.

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