Eighteenth Canadian Geotechnical Colloquium: Limit States Design For Foundations. Part II. Development for the National Building Code of Canada

1996 ◽  
Vol 33 (6) ◽  
pp. 984-1007 ◽  
Author(s):  
Dennis E Becker
Keyword(s):  
Reliability Index ◽  
Resistance Factor ◽  
Design Approach ◽  
Building Code ◽  
Foundation Engineering ◽  
Limit States ◽  
Resistance Factors ◽  
Code Calibration ◽  
Factor Design ◽  
Ultimate Limit

The geotechnical engineering profession in Canada is in the process of evaluating limit states design (LSD) for its incorporation into codes of practice for foundation engineering to provide a consistent design approach between geotechnical and structural engineers. This paper describes the work carried out for the initial development of LSD for foundations in the National Building Code of Canada. A load and resistance factor design approach, based on a factored overall geotechnical resistance, is used. The resistance factors for the ultimate limit states of bearing capacity and sliding of shallow and deep foundations are derived from a direct calibration with working stress design (WSD) and from a reliability analysis. The resistance factors derived from both approaches are consistent with each other and provide a reasonably constant reliability index of about 3.0 to 3.5. A relationship is presented that relates the reliability index to a global factor of safety and resistance factor. Design examples are provided that show that the proposed LSD produces designs that are comparable with those produced by traditional WSD. The importance of serviceability limits states is discussed, and the items that require further study and research work to refine code calibration are identified. Key words: limit states design, reliability index, code calibration, resistance factors, foundations, ultimate limit states.

Load and Resistance Factor Design of Driven Piles

1996 ◽  
Vol 1546 (1) ◽  
pp. 88-93 ◽  
Author(s):  
George G. Goble
Keyword(s):  
Quality Control ◽  
Highway Bridges ◽  
The United States ◽  
Resistance Factor ◽  
Limit States ◽  
Resistance Factors ◽  
Nominal Strength ◽  
Factor Design ◽  
Load And Resistance Factor ◽  
Driven Pile

A load and resistance factor design (LRFD) bridge specification has been accepted by the AASHTO Bridge Committee. This design approach is now being implemented for highway bridges in the United States, including the design of driven pile foundations. To test the new specification's practicality and usefulness, an example problem has been solved using it. In the example, a pipe pile was designed to be driven into a granular soil to support a bridge column subjected to a factored axial compression load of 10 MN. The nominal strength selected for the pile was 1.58 MN with an estimated length of 25 m. Since the resistance factors are defined by the specified quality control procedures, the number of piles required in the foundation also depends on the quality control. In this example, the number of piles required varied from 15 to 8 with improved quality control, for a savings of almost half of the piles. This example indicated that the new AASHTO LRFD specification for driven pile design can be used effectively to produce a more rationally designed foundation. Some modifications should be made to include additional serviceability limit states, and additional research may indicate that changes should be made in some of the resistance factors.

Application of the Bayesian Updating to the Load and Resistance Factor Design (LRFD) Method

2013 ◽  
Author(s):  
Yuji Nakasone
Keyword(s):  
Reliability Index ◽  
Statistical Data ◽  
Design Method ◽  
Bayesian Updating ◽  
Fracture Probability ◽  
Resistance Factor ◽  
Factor Design ◽  
Index Value ◽  
Load And Resistance Factor ◽  
Adequate Reliability

The present study has attempted to apply the Bayesian updating to the LRFD, or Load and Resistance Factor Design method. The LRFD method takes into account the statistical distribution of the material resistance and those of the applied loads. The LRFD method can reflect the degrees of different uncertainties of the resistances of the materials and the loads. Thus, the LRFD method can attain the optimal design which can keep up an adequate reliability level of the components designed, whereas the conventional allowable stress design (ASD) method cannot. The LFRD method, however, requires vast amount of statistical data for the material resistances and the applied loadings of different kinds. The present study proposes the Bayesian updating scheme which requires only a small amount of statistical data for the material resistance and the various load item distributions to calculate the values of the partial design factors used in the LRFD method. It is revealed that the median of the updated distributions of the estimated standard deviations can give adequate reliability index values higher than the target reliability index value corresponding to a fracture probability of 0.01% even for a small number of the statistical data, say, less than 20. This paper also compares and discusses the LRFD method with the updating scheme and the conventional ASD method, showing that the updated LRFD method can maintain the reliability index value higher than the target index value whereas the ASD method cannot.

Assessing the Target Reliability Index for Nuclear Piping

2016 ◽  
Author(s):  
Kleio Avrithi
Keyword(s):  
Reliability Index ◽  
Historical Data ◽  
Allowable Stress ◽  
Safety Factors ◽  
Code Calibration ◽  
Target Reliability Index ◽  
Consistent Manner ◽  
Factor Design ◽  
Load And Resistance Factor ◽  
Allowable Stress Design

Previous research developed Load and Resistance Factor Design (LRFD) equations for Class 2 and 3 nuclear piping for different reliability levels and load combinations. The LRFD equations consider separate safety factors for each load and for the strength of steel in opposition to the Allowable Stress Design (ASD) equations used in the ASME Boiler and Pressure Vessel (B&PV) Code, Section III, Div. 1, where only one safety factor is considered. In order to use the developed LRFD equations for the design of nuclear piping, specific reliability levels or else acceptable probabilities of failure need to be assigned to each Code equation. The paper discusses the available methods for evaluating the target reliability index, such as historical data of piping failures, expert-opinion elicitation, and Code calibration. Code calibration is the method of determining the existing level of reliability in the Code equations and assigning the same reliability to the developed LRFD equations in a consistent manner. Code Calibration is explained to be the more appropriate method of assigning reliability levels to the LRFD equations. The other methods can supplement the analysis results.

Behaviour and ultimate tensile strength of partial joint penetration groove welds

1989 ◽  
Vol 16 (3) ◽  
pp. 384-399 ◽  
Author(s):  
Darrel P. Gagnon ◽  
D. J. Laurie Kennedy
Keyword(s):  
Experimental Data ◽  
Tensile Strength ◽  
Ultimate Tensile Strength ◽  
Key Words ◽  
Cross Section ◽  
Resistance Factor ◽  
Steel Plates ◽  
Limit States ◽  
Resistance Factors ◽  
Lateral Deflections

Partial joint penetration groove welds may be used in columns, for example, when it is not necessary to develop the full tensile capacity of the cross section. Also, where it is not feasible to make a full joint penetration groove weld because welding can be done from one side only, the strength of a partial joint penetration groove weld may be adequate. Limited experimental data have shown that the strength of partial penetration welds are proportional to their areas.A series of 75 tests on 25 mm thick, grade 300W and grade 350A steel plates, with welds made with matching electrodes and with 20–100% penetration, were conducted. The overall behaviour, the effects of percent penetration, plate strength, and the eccentricity of the load were investigated. The inherent ductility of the welds allows lateral deflections and straining to take place so that eccentrically loaded welds are as strong as concentrically loaded welds. The strength of welds is greater than the strength of the plate multiplied by the percent penetration and increases with the increasing lateral restraint that occurs with decreasing penetration. Design equations and resistance factors, based on weld strengths at least equal to the percent penetration multiplied by the ultimate tensile resistance of the plate, are proposed. Recommendations for fabrication are presented. Key words: behaviour, groove weld, limit states, partial joint penetration, strength, resistance factor, tension, ultimate.

scholarly journals Load and resistance factor design approach for seismic buckling of fast reactor vessels

2017 ◽  
Vol 4 (3) ◽  
pp. 16-00558-16-00558
Author(s):  
Shigeru TAKAYA ◽  
Naoto SASAKI ◽  
Tai ASAYAMA ◽  
Yoshio KAMISHIMA
Keyword(s):  
Fast Reactor ◽  
Resistance Factor ◽  
Design Approach ◽  
Factor Design ◽  
Load And Resistance Factor
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