Resistance Factors at Serviceability Limit State Using the Texas Cone Penetrometer as the Predictive Model

2021 ◽  
Vol 15 (1) ◽  
Author(s):  
Rozbeh Moghaddam
Keyword(s):  
Limit State ◽  
Drilled Shafts ◽  
Load Test ◽  
Deep Foundations ◽  
Driven Piles ◽  
Resistance Factors ◽  
Serviceability Limit State ◽  
First Order Second Moment ◽  
Texas Cone Penetrometer ◽  
Load And Resistance Factor

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.

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.

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.

Resistance Factors for Single Driven Piles from Experiments

1997 ◽  
Vol 1569 (1) ◽  
pp. 47-54 ◽  
Author(s):  
Gil L. Yoon ◽  
Michael W. O’Neill
Keyword(s):  
Sampling Technique ◽  
Load Factor ◽  
Driven Piles ◽  
Resistance Factors ◽  
Present Generation ◽  
Reliability Method ◽  
First Order Second Moment ◽  
Factor Design ◽  
Load And Resistance Factor ◽  
A Site

Present-generation resistance factors for foundations in load and resistance factor design (LRFD) do not necessarily reflect directly the variance in site-specific resistance and bias in making resistance estimates. The purpose of this paper is to describe a process whereby resistance factors can be determined from experimental data at a site and to demonstrate that process for driven piles at a specific site in overconsolidated clay. Eleven pipe piles were tested to failure in compression, and 28 cone penetrometer tests (CPTs) were performed near the piles. The CPT results were characterized through both a geostatistical method and a random sampling technique to estimate resistance factors for ultimate pile resistances using three CPT methods and two α-methods. A first-order, second-moment reliability method was applied using the interpreted bias characteristics of the design methods and the dispersion characteristics of the CPT and pile tests to relate resistance factors to selected reliability indexes. The resistance factors obtained for this site by this process were 0.50 to 0.62 for the three CPT methods and 0.30 to 0.55 for the ॅ-methods for a target reliability index of 3.5, depending on the value selected for the live load factor.

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.

scholarly journals Serviceability limit state reliability-based design of augered cast-in-place piles in granular soils

2017 ◽  
Vol 54 (12) ◽  
pp. 1704-1715 ◽  
Author(s):  
Seth C. Reddy ◽  
Armin W. Stuedlein
Keyword(s):  
Lower Bound ◽  
Limit State ◽  
Companion Paper ◽  
Resistance Factor ◽  
Granular Soils ◽  
Serviceability Limit State ◽  
Reliability Based Design ◽  
Wide Range ◽  
Load Displacement ◽  
Load And Resistance Factor

This study proposes a reliability-based design procedure to evaluate the allowable load for augered cast-in-place (ACIP) piles installed in predominately granular soils based on a prescribed level of reliability at the serviceability limit state. The ultimate limit state (ULS) ACIP pile–specific design model proposed in the companion paper is incorporated into a bivariate hyperbolic load–displacement model capable of describing the variability in the load–displacement relationship for a wide range of pile displacements. Following the approach outlined in the companion paper, distributions with truncated lower-bound capacities are incorporated into the reliability analyses. A lumped load-and-resistance factor is calibrated using a suitable performance function and Monte Carlo simulations. The average and conservative 95% lower-bound prediction intervals for the calibrated load-and-resistance factor resulting from the simulations are provided. Although unaccounted for in past studies, the slenderness ratio is shown to have significant influence on foundation reliability. Because of the low uncertainty in the proposed ULS pile capacity prediction model, the use of a truncated distribution has moderate influence on foundation reliability.

scholarly journals Behaviour of Single and Group Helical Piles in Sands from Model Experiments

2019 ◽  
Vol 278 ◽  
pp. 03007
Author(s):  
Jongho Bak ◽  
Byung-hyun Choi ◽  
Junwon Lee ◽  
Jonghwan Bae ◽  
Kicheol Lee ◽  
...  
Keyword(s):  
Rotation Speed ◽  
Axial Loading ◽  
Complete Removal ◽  
Drilled Shafts ◽  
Load Test ◽  
Oil Sand ◽  
Driven Piles ◽  
Pile Installation ◽  
Helical Piles ◽  
Pile Load Tests

Mainly used foundations of oil sand plants are drilled shafts or driven piles. As environmental regulations become increasingly strict, complete removal of the foundation is becoming more important during the step of plant dismantling. However, it is difficult to remove completely drilled shafts or driven piles which are deeply installed to obtain more bearing capacity. Helical piles can be easily removed and recycled after use. This study analyses the behaviour of single and group helical piles in sands. For single helical piles, pile load tests of helical piles were conducted varying helix spacing, rotation speed and weight of axial loading during pile installation. The single pile tests determined the optimal helix spacing, rotation speed, weight of axial loading during pile installation. And then, pile load test of group helical piles was performed varying pile spacing from the centre place of upper connector based on the optimal installation conditions.

Characterization of model uncertainty in predicting axial resistance of piles driven into clay

2019 ◽  
Vol 56 (8) ◽  
pp. 1098-1118 ◽  
Author(s):  
Chong Tang ◽  
Kok-Kwang Phoon
Keyword(s):  
Model Uncertainty ◽  
Driven Piles ◽  
Resistance Factors ◽  
Reliability Based Design ◽  
Pile Diameter ◽  
Measured Resistance ◽  
Load Tests ◽  
Similar Accuracy ◽  
Load And Resistance Factor ◽  
Axial Resistance

This paper summarizes 239 static load tests to evaluate the performance of four static design methods for axial resistance of driven piles in clay. The methods are ISO 19901-4:2016, SHANSEP, ICP-05, and NGI-05. The database is categorized into four groups depending on the load type (compression or uplift) and pile tip condition (open or closed end). The model uncertainty in resistance prediction is quantified as a ratio between measured and calculated resistance, which is called a model factor. The measured resistance is interpreted as a load producing a settlement level of 10% pile diameter. Database studies show that the four methods present a similar accuracy, where the mean and coefficient of variation (COV) of the model factor are around 1 and 0.3, respectively. The COV values are smaller than those for driven piles in sand available in literature. The model statistics determined from the database are applicable to a simplified or full probabilistic form of reliability-based design (RBD) of driven piles in clay. As an illustration, the resistance factors in load and resistance factor design (LRFD, a simplified form of RBD) are calibrated by Monte Carlo simulations.

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