scholarly journals Load and resistance factor design of drilled shafts at the service limit state

2013 ◽  
Author(s):  
Thanh Thuy Vu
Keyword(s):  
Limit State ◽  
Drilled Shafts ◽  
Resistance Factor ◽  
Service Limit State ◽  
Factor Design ◽  
Load And Resistance Factor

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.

Calibration concepts for load and resistance factor design (LRFD) of reinforced soil walls

2008 ◽  
Vol 45 (10) ◽  
pp. 1377-1392 ◽  
Author(s):  
Richard J. Bathurst ◽  
Tony M. Allen ◽  
Andrzej S. Nowak
Keyword(s):  
Limit State ◽  
Reinforced Soil ◽  
Resistance Factor ◽  
Resistance Factors ◽  
Soil Walls ◽  
Calibration Methods ◽  
Load And Resistance Factors ◽  
Factor Design ◽  
Load And Resistance Factor ◽  
Reinforced Soil Walls

Reliability-based design concepts and their application to load and resistance factor design (LRFD or limit states design (LSD) in Canada) are well known, and their adoption in geotechnical engineering design is now recommended for many soil–structure interaction problems. Two important challenges for acceptance of LRFD for the design of reinforced soil walls are (i) a proper understanding of the calibration methods used to arrive at load and resistance factors, and (ii) the proper interpretation of the data required to carry out this process. This paper presents LRFD calibration principles and traces the steps required to arrive at load and resistance factors using closed-form solutions for one typical limit state, namely pullout of steel reinforcement elements in the anchorage zone of a reinforced soil wall. A unique feature of this paper is that measured load and resistance values from a database of case histories are used to develop the statistical parameters in the examples. The paper also addresses issues related to the influence of outliers in the datasets and possible dependencies between variables that can have an important influence on the results of calibration.

Probabilistic analysis of drilled shaft service limit state using the "t–z" method

2006 ◽  
Vol 43 (12) ◽  
pp. 1324-1332 ◽  
Author(s):  
Anil Misra ◽  
Lance A Roberts
Keyword(s):  
Limit State ◽  
Drilled Shafts ◽  
Cumulative Distribution ◽  
Hyperbolic Model ◽  
Drilled Shaft ◽  
Large Set ◽  
Reliability Based Design ◽  
Service Limit State ◽  
Load Displacement ◽  
Load And Resistance Factor

The utility of the load and resistance factor design (LRFD) approach is being increasingly recognized for the design of drilled shafts. The current LRFD methodologies of drilled shaft design would be more efficient if reliability based design approaches were used for service limit state design. In this paper, the "t–z" methodology is utilized to develop probabilistic approaches for axial service limit state analysis of drilled shafts. Two different models of the soil–shaft interaction are implemented for load displacement calculations: (1) an ideal elastoplastic model, and (2) a hyperbolic model. For both of these soil–shaft interactions, Monte Carlo simulation is used to obtain a large set of load–displacement curves assuming lognormal distributions for the shaft–soil interface properties. The load–displacement curves are analyzed to develop two alternate methods for determining the probability of drilled shaft failure at the service limit state. As a result, cumulative distribution histograms are developed for drilled shaft load capacities at allowable head displacements. These results may be utilized to obtain resistance factors that can be applied to LRFD based service limit state design.Key words: drilled shaft, serviceability, failure probability, load displacement relation, "t–z" method.

Load and resistance factor design of shallow foundations against bearing failure

2008 ◽  
Vol 45 (11) ◽  
pp. 1556-1571 ◽  
Author(s):  
Gordon A. Fenton ◽  
D. V. Griffiths ◽  
Xianyue Zhang
Keyword(s):  
Bearing Capacity ◽  
Limit State ◽  
Resistance Factor ◽  
Shallow Foundation ◽  
Ultimate Limit State ◽  
Full Potential ◽  
Design Codes ◽  
Reliability Based Design ◽  
Factor Design ◽  
Load And Resistance Factor

Shallow foundation designs are typically governed either by settlement, a serviceability limit state, or by bearing capacity, an ultimate limit state. While geotechnical engineers have been designing against these limit states for over half a century, it is only recently that they have begun to migrate towards reliability-based designs. At the moment, reliability-based design codes are generally derived through calibration with traditional working stress designs. To take advantage of the full potential of reliability-based design the profession must go beyond calibration and take geotechnical uncertainties into account in a rational fashion. This paper proposes a load and resistance factor design (LRFD) approach for the bearing capacity design of a strip footing, using load factors as specified by structural codes. The resistance factors required to achieve an acceptable failure probability are estimated as a function of the spatial variability of the soil and by the level of “understanding” of the soil properties in the vicinity of the foundation. The analytical results, validated by simulation, are primarily intended to aid in the development of the next generation of reliability-based geotechnical design codes, but can also be used to assess the reliability of current designs.

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