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.

Development of load and resistance factor design format for flexible pavements

1998 ◽  
Vol 25 (5) ◽  
pp. 880-885 ◽  
Author(s):  
Hyung Bae Kim ◽  
Ronald S Harichandran ◽  
Neeraj Buch
Keyword(s):  
Flexible Pavements ◽  
The United States ◽  
Resistance Factor ◽  
Pavement Design ◽  
Fatigue Design ◽  
Reliability Methods ◽  
Partial Safety Factors ◽  
Factor Design ◽  
Load And Resistance Factor ◽  
Different Levels

The objective of pavement design, just as with the design of other structures, is to provide economical designs at specified levels of reliability. Methods that yield designs with different levels of reliability are undesirable, and over the course of time design approaches in the United States have converged toward the load and resistance factor design (LRFD) format in order to assure uniform reliability. At present the LRFD format has been implemented in concrete, steel, wood, and bridge design specifications. In this paper, reliability concepts are used to illustrate the development of an LRFD format for fatigue design of flexible pavements. It is shown that 10 candidate pavement sections designed against premature fatigue failure according to standard practice using the DNPS86 software do not have uniform reliability. It is demonstrated that uniform reliability can be achieved by using the LRFD format. The work reported is based on assumed variations of pavement layer properties and on analytical formulation; field verification was not attempted.Key words: LRFD, reliability index, fatigue, partial safety factors, flexible pavement design.

AASHTO’s Load and Resistance Factor Design Specifications for Transverse Braces: Adverse Effects on Integrity and Durability of Reinforced Concrete Deck Slabs

2000 ◽  
Vol 1740 (1) ◽  
pp. 118-125 ◽  
Author(s):  
Martin P. Burke ◽  
Joseph S. Seif
Keyword(s):  
Reinforced Concrete ◽  
Highway Bridges ◽  
Resistance Factor ◽  
Structural Systems ◽  
Steel Bridge ◽  
Design Specifications ◽  
Deck Slabs ◽  
Factor Design ◽  
Load And Resistance Factor ◽  
Concrete Deck

The transverse bracing provisions (diaphragms, cross-braces, crossframes, and so on) of the 1998 AASHTO load and resistance factor design (LRFD) bridge design specifications for the design of deck-type highway bridges are examined. This examination suggests that implementation of these provisions not only will have an adverse effect on the integrity and durability of reinforced concrete deck slabs, and consequently on life-cycle bridge costs; implementation of such provisions also has the potential to affect the desirability of steel bridge construction adversely. Instead of avoiding the use of midspan braces, as implied by LRFD provisions, it is urged that midspan braces be more generally recognized as primary elements of complex superstructure structural systems and thus be sized and spaced to function not only as transverse flange braces but also integrally with concrete deck slabs to distribute vehicular loads laterally. Such a practice not only will yield more efficient higher-quality structural systems capable of functioning effectively for 100 years or more, thus doubling their presently expected lives, but it will also help extend the service lives of the more vulnerable reinforced concrete deck slabs.

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.

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