Reliability Evaluation of AASHTO Design Equations for Drilled Shafts

1997 ◽  
Vol 1582 (1) ◽  
pp. 60-67
Author(s):  
William M. Isenhower ◽  
James H. Long
Keyword(s):  
Data Base ◽  
Reliability Evaluation ◽  
Drilled Shafts ◽  
Drilled Shaft ◽  
Factors Affecting ◽  
First Order ◽  
Axial Capacity ◽  
Moment Methods ◽  
First Order Second Moment ◽  
Load Tests

A reliability evaluation of the AASHTO design equations for drilled shafts is described. The evaluation computed the variance of a data base containing load tests to failure on 30 straight-sided drilled shafts using first-order, second-moment methods applied to the AASHTO design equations. The computed variance was compared with the measured variance of the data base. The measured variance was found to exceed the computed variance for approximately 75 percent of the load tests. This is believed to result from important factors affecting the axial capacity of the drilled shaft not being included in the AASHTO design equations. It is speculated that the missing factors are related to common variations in construction practices for drilled shafts.

Reliability Analysis of Circular Footing by Using GP and MPMR

2021 ◽  
Vol 12 (1) ◽  
pp. 1-19
Author(s):  
Rahul Kumar ◽  
Pijush Samui ◽  
Sunita Kumari ◽  
Yildirim Hüseyin Dalkilic
Keyword(s):  
Bearing Capacity ◽  
Reliability Analysis ◽  
Unit Weight ◽  
Variable Parameters ◽  
Angle Of Internal Friction ◽  
First Order ◽  
Moment Methods ◽  
First Order Second Moment ◽  
Minimax Probability Machine Regression ◽  
Circular Footing

Circular footings are designed to bear a load of super structures. Studies have been done on the influence of soil properties on bearing capacity of shallow foundations. The use of circular foundation is practical in geotechnical engineering. During the design of circular footing, bearing capacity of soil is taken into consideration, and cohesion (c), unit weight (γ), and angle of internal friction (ϕ) are the most variable parameters. Reliability analysis is used frequently for the design of circular footing. Most of the authors have used first order second moment methods (FOSM). However, FOSM is a time-consuming method. Drawbacks of FOSM have been overcome by genetic programming (GP), minimax probability machine regression (MPMR). This article gives a distinct analysis between the developed MPMR based FOSM and GP-based FOSM.

Reliability-based design of mechanically connected built-up wood columns

1991 ◽  
Vol 18 (2) ◽  
pp. 171-181 ◽  
Author(s):  
S. K. Malhotra ◽  
A. P. Sukumar
Keyword(s):  
Data Base ◽  
Reliability Analysis ◽  
Rational Model ◽  
Limit States ◽  
Wood Structures ◽  
Factors Affecting ◽  
Analysis And Design ◽  
Additional Information ◽  
Reliability Based Design ◽  
First Order Second Moment

Built-up wood structural components and systems have been in use in the building industry for decades. Though easy to construct, they are rather complex to analyze because of numerous factors affecting their strength and behaviour. This paper explains the development of a reliability-based design formulation in limit states for built-up columns, using a rational mathematical model for the analysis and design. Also, a brief discussion is given on a set of simplified design rules for layered columns which have been incorporated into the Canadian Standards Association Standard CAN3-086.1-M89 "Code for engineering design in wood (limit states design)." The rational model as well as the simplified rules are subjected to reliability analysis.The Canadian specifications for the design of wood structures in limit states format have been available since December 1984. These specifications are essentially a soft conversion of the previous working stress design code. The 1989 edition of the code is mostly based on the principles of reliability-based design. Some portions of the code are still not fully based on reliability approach, as additional information is needed for the establishment of a reliable data base upon which the "uncertainty factors" could be redefined in a more rational and logical manner. This paper provides that type of information and the details of reliability analysis as applied to mechanically connected built-up timber columns. The reliability analyses are performed based on first-order second-moment methods, using a data base of column strengths. The data base consists of experimental as well as simulated results. Two reliability analysis programs, BUCREL (built-up column reliability analysis) and POINT (reliability analysis using design point algorithm), are developed. Design recommendations are derived in a reliability-based design format. Key words: buckling, columns, design specifications, efficiency, joints, layered columns, rational model, reliability, resistance factor, slip, spaced columns, timber, wood.

Evaluation of uplift interpretation criteria for drilled shafts in gravelly soils

2012 ◽  
Vol 49 (1) ◽  
pp. 70-77 ◽  
Author(s):  
Yit-Jin Chen ◽  
Tsu-Hung Chu
Keyword(s):  
Drilled Shafts ◽  
Load Test ◽  
Drilled Shaft ◽  
Specific Design ◽  
Interpretation Criteria ◽  
Interpretation Criterion ◽  
Gravelly Soils ◽  
Load Tests ◽  
Drilled Shaft Foundations ◽  
Shaft Failure

Representative interpretation criteria are examined in this paper to evaluate the capacity of drilled shaft foundations under axial uplift loading in gravelly soils. A large number of uplift shaft load tests for gravelly soils are used for analysis, and the interpretation criteria are applied to these load test data to establish a consistent uplift interpretation criterion. The statistical results show that the smaller the uplift displacement, the higher the coefficient of variation. In general, the displacements required to mobilize shaft failure load in gravelly soils are larger than those in non-gravelly soils. Based on these analyses, the relative merits and interrelationships of these criteria are established. Specific design recommendations for the evaluation of uplift drilled shaft capacity are given.

Factors Affecting the Strength of Flexor Tendon Repair

1992 ◽  
Vol 17 (5) ◽  
pp. 550-552 ◽  
Author(s):  
D. BHATIA ◽  
K. E. TANNER ◽  
W. BONFIELD ◽  
N. D. CITRON
Keyword(s):  
Cyclic Load ◽  
Suture Material ◽  
Flexor Tendon ◽  
Tendon Repair ◽  
Flexor Tendon Repair ◽  
Factors Affecting ◽  
Full Strength ◽  
Load Tests

The effects of different thicknesses and configurations of core sutures were studied in human cadaveric flexor tendon repairs. Both straight and cyclic load tests were employed. To exploit the full strength of 4/0 suture material, the Kessler repair using four locked single knots would seem to be appropriate.

scholarly journals Comparative investigations of nonlinear and linear observers for a highly manoeuvrable target in sliding mode guidance

2017 ◽  
Vol 65 (2) ◽  
pp. 233-245
Author(s):  
Y. Wang ◽  
M. Sun ◽  
S. Du ◽  
Z. Chen
Keyword(s):  
Sliding Mode ◽  
Guidance System ◽  
Key Factors ◽  
Factors Affecting ◽  
First Order ◽  
Guidance Law ◽  
Linear Observer ◽  
Overall Performance ◽  
Twisting Algorithm ◽  
Different Levels

Abstract Target manoeuvre is one of the key factors affecting guidance accuracy. To intercept highly maneuverable targets, a second-order sliding-mode guidance law, which is based on the super-twisting algorithm, is designed without depending on any information about the target motion. In the designed guidance system, the target estimator plays an essential role. Besides the existing higher-order sliding-mode observer (HOSMO), a first-order linear observer (FOLO) is also proposed to estimate the target manoeuvre, and this is the major contribution of this paper. The closed-loop guidance system can be guaranteed to be uniformly ultimately bounded (UUB) in the presence of the FOLO. The comparative simulations are carried out to investigate the overall performance resulting from these two categories of observers. The results show that the guidance law with the proposed linear observer can achieve better comprehensive criteria for the amplitude of normalised acceleration and elevator deflection requirements. The reasons for the different levels of performance of these two observer-based methods are thoroughly investigated.

Reliability analysis of a structural element based on the Advanced First-Order-Second-Moment Method.

1985 ◽  
Vol 51 (472) ◽  
pp. 2811-2816
Author(s):  
Yoshisada MUROTSU ◽  
Masaaki YONEZAWA ◽  
Hiroo OKADA ◽  
Satoshi MATSUZAKI ◽  
Toshiki MATSUMOTO
Keyword(s):  
Reliability Analysis ◽  
Moment Method ◽  
Structural Element ◽  
Second Moment ◽  
First Order ◽  
First Order Second Moment ◽  
Second Moment Method

Expansive concrete drilled shafts

1985 ◽  
Vol 12 (2) ◽  
pp. 382-395 ◽  
Author(s):  
Shamim A. Sheikh ◽  
Michael W. O'Neill ◽  
M. A. Mehrazarin
Keyword(s):  
Load Transfer ◽  
Stress Path ◽  
Drilled Shafts ◽  
Drilled Shaft ◽  
Cement Concrete ◽  
Bored Pile ◽  
Expansive Concrete ◽  
Stiff Clay ◽  
Expansive Cement

A hypothesis is presented in this paper that states that expansive cement concrete produces a stronger bond between the concrete in a drilled shaft (bored pile) and the surrounding soil than does normal cement; this results in an increase in the frictional component of capacity and a reduction in the settlement of the shaft at working load levels.Four types of expansive cement, type "K" cement (the expansive cement available commercially) and three made from commercially available materials, were tested for their expansion characteristics; two of them were selected to be used in two instrumented drilled shafts in stiff clay. Normal (type 1) cement was used in a third shaft to serve as a reference. The three shafts were tested to failure after essentially all the expansion was deemed to have taken place in the two expansive concrete shafts. Lateral and longitudinal expansion of the shafts were monitored during the curing period. Load–settlement behaviour and load transfer between shafts and soil during the tests were studied.The test results permitted the preliminary conclusion that expansive cement concrete can increase the frictional capacity of drilled shafts in stiff clay by as much as 50% and reduce the settlement by about 50%. The results are valid for short-term behaviour of drilled shafts made of expansive cement. The long-term behaviour of such shafts remains to be studied. Key words: base bearing capacity, bored pile, cement (expansive), concrete (structural), drilled shaft, ettringite, expansion, frictional capacity, settlement, stress path.

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