Author: Dan Ding (Engineer)
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
Probabilistic analyses were performed to study the effect of the number of measurements on the reliability of spread footings designed using load and resistance factor design (LRFD). Several alternative methods, including a new proposed method, to practically account for the uncertainty in soil design parameters were evaluated for designs using small numbers of measurements. Results show that design parameters are largely affected by the number of measurements, thus, in turn, the reliability of foundation designs highly depends on the number of measurements. Use of the penalty function and the one-sided upper confidence bound method effectively reduces the percentage of “unconservative” cases when the number of measurements is small.
Author:
Publisher: Transportation Research Board
ISBN: 0309154677
Category : Technology & Engineering
Languages : en
Pages : 149
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Book Description
This report develops and calibrates procedures and modifies the AASHTO LRFD Bridge Design Specifications, Section 10-Foundations for the Strength Limit State Design of Shallow Foundations. The material in this report will be of immediate interest to bridge engineers and geotechnical engineers involved in the design of shallow foundations.
Author: Chong Tang
Publisher: CRC Press
ISBN: 0429655959
Category : Technology & Engineering
Languages : en
Pages : 497
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Book Description
Model Uncertainties in Foundation Design is unique in the compilation of the largest and the most diverse load test databases to date, covering many foundation types (shallow foundations, spudcans, driven piles, drilled shafts, rock sockets and helical piles) and a wide range of ground conditions (soil to soft rock). All databases with names prefixed by NUS are available upon request. This book presents a comprehensive evaluation of the model factor mean (bias) and coefficient of variation (COV) for ultimate and serviceability limit state based on these databases. These statistics can be used directly for AASHTO LRFD calibration. Besides load test databases, performance databases for other geo-structures and their model factor statistics are provided. Based on this extensive literature survey, a practical three-tier scheme for classifying the model uncertainty of geo-structures according to the model factor mean and COV is proposed. This empirically grounded scheme can underpin the calibration of resistance factors as a function of the degree of understanding – a concept already adopted in the Canadian Highway Bridge Design Code and being considered for the new draft for Eurocode 7 Part 1 (EN 1997-1:202x). The helical pile research in Chapter 7 was recognised by the 2020 ASCE Norman Medal.
Author: Fred H. Kulhawy
Publisher:
ISBN: 9780784412763
Category : Engineering geology
Languages : en
Pages : 0
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Book Description
WIDTH: 405pt; BORDER-COLLAPSE: collapse border=0 cellSpacing=0 cellPadding=0 width=540> WIDTH: 405pt; mso-width-source: userset; mso-width-alt: 19748 width=540> HEIGHT: 31.5pt height=42> BORDER-BOTTOM: #f0f0f0; BORDER-LEFT: #f0f0f0; BACKGROUND-COLOR: transparent; WIDTH: 405pt; HEIGHT: 31.5pt; BORDER-TOP: #f0f0f0; BORDER-RIGHT: #f0f0f0 class=xl65 height=42 width=540>GSP 229 contains 54 papers on risk and uncertainty in foundation engineering presented in honor of Fred H. Kulhawy.
Author: Kevin C. Foye
Publisher:
ISBN: 9781622602414
Category : Transportation
Languages : en
Pages :
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Book Description
Load and Resistance Factor Design (LRFD) shows promise as a viable alternative to the present working stress design (WSD) approach to foundation design. The key improvements of LRFD over the traditional Working Stress Design (WSD) are the ability to provide a more consistent level of reliability and the possibility of accounting for load and resistance uncertainties separately. In order for foundation design to be consistent with current structural design practice, the use of the same loads, load factors and load combinations would be required. In this study, we review the load factors presented in various LRFD Codes from the US, Canada and Europe. For LRFD to gain acceptance in geotechnical engineering, a framework for the objective assessment of resistance factors is needed. Such a framework, based on reliability analysis is proposed in this study. Probability Density Functions (PDFs), representing design variable uncertainties, are required for analysis. A systematic approach to the selection of PDFs is presented. Such a procedure is a critical prerequisite to a rational probabilistic analysis in the development of LRFD methods in geotechnical engineering. Additionally, in order for LRFD to fulfill its promise for designs with more consistent reliability, the methods used to execute a design must be consistent with the methods assumed in the development of the LRFD factors. In this study, a methodology for the estimation of soil parameters for use in design equations is proposed that should allow for more statistical consistency in design inputs than is possible in traditional methods. Resistance factor values are dependent upon the values of load factors used. Thus, a method to adjust the resistance factors to account for code-specified load factors is also presented. The various considered methods obtain their input parameters from the CPT, the SPT, or laboratory testing. Designers may wish to use design methods that are not considered in this study. As such, the designer needs the capability to select resistance factors that reflect the uncertainty of the design method chosen. A methodology is proposed in this study to accomplish this task, in a way that is consistent with the framework.
Author:
Publisher:
ISBN:
Category : Highway research
Languages : en
Pages : 508
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Book Description
Author: Haijian Fan
Publisher:
ISBN:
Category : Civil engineering
Languages : en
Pages : 177
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Book Description
With the implementation of load and resistance factor design (LRFD) by the U.S. Federal Highway Administration, the design of deep foundations is migrating from Level I (e.g., allowable stress design) codes to Level II codes (e.g., LRFD). Nevertheless, there are still unsolved issues regarding the implementation of load and resistance factor design. For example, there is no generally accepted guidance on the statistical characterization of soil properties. Moreover, the serviceability limit check in LRFD is still deterministic. No uncertainties arising in soil properties, loads and design criteria are taken into account in the implementation of LRFD. In current practice, the load factors and resistances are taken as unity, and deterministic models are applied to evaluate the displacements of geotechnical structures. In order to address the aforementioned issues of LRFD, there is a need for a computational method for conducting reliability analysis and computational tools for statistically characterizing the variability of soil properties. The objectives of this research are: 1) to develop a mathematically sound computational tool for conducting reliability analysis for deep foundations; and 2) to develop the associated computational method that can be used to determine the variability model of a soil property. To achieve consistency between the strength limit check and the serviceability limit check of the LRFD framework, performance-based design methodology is developed for deep foundation design. In the proposed methodology, the design criteria are defined in terms of the displacements of the structure that are induced by external loads. If the displacements are within the specified design criteria, the design is considered satisfactory. Otherwise, failure is said to occur. In order to calculate the probability of failure, Monte Carlo simulation is employed. In Monte Carlo simulation, the variability of the random variables that are involved in the reliability analysis is captured by simulating a large number of samples according to their respective probability distributions. Next, the simulations of the random variables are used as the input to the commonly used p-y method and load transfer method to evaluate the load-displacement behavior. Once the displacements are calculated, it can be determined whether or not failure will occur. Accordingly, the failure probability is calculated as the number of failure events to the total number of simulations. A series of computer programs have been developed and validated based on the proposed performance-based design methodology. These computer programs can be used to conduct reliability analysis for designing a drilled shaft. To determine the variability model of soil properties that will be used as input to the computer programs, a computational method has been developed in which the blow counts in a standard penetration test are required as inputs. It is found that the consideration of the dependence structure of soil properties is important for reliability analysis.
Author: Tharwat M. Baban
Publisher: John Wiley & Sons
ISBN: 1119056136
Category : Technology & Engineering
Languages : en
Pages : 752
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Book Description
Shallow Foundations: Discussions and Problem Solving is written for civil engineers and all civil engineering students taking courses in soil mechanics and geotechnical engineering. It covers the analysis, design and application of shallow foundations, with a primary focus on the interface between the structural elements and underlying soil. Topics such as site investigation, foundation contact pressure and settlement, vertical stresses in soils due to foundation loads, settlements, and bearing capacity are all fully covered, and a chapter is devoted to the structural design of different types of shallow foundations. It provides essential data for the design of shallow foundations under normal circumstances, considering both the American (ACI) and the European (EN) Standard Building Code Requirements, with each chapter being a concise discussion of critical and practical aspects. Applications are highlighted through solving a relatively large number of realistic problems. A total of 180 problems, all with full solutions, consolidate understanding of the fundamental principles and illustrate the design and application of shallow foundations.
Author: Donald P. Coduto
Publisher: Pearson Higher Ed
ISBN: 1292052430
Category : Technology & Engineering
Languages : en
Pages : 889
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Book Description
For undergraduate/graduate-level foundation engineering courses. Covers the subject matter thoroughly and systematically, while being easy to read. Emphasizes a thorough understanding of concepts and terms before proceeding with analysis and design, and carefully integrates the principles of foundation engineering with their application to practical design problems.
Author: Lymon C. Reese
Publisher: John Wiley & Sons
ISBN: 0471431591
Category : Technology & Engineering
Languages : en
Pages : 608
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Book Description
One-of-a-kind coverage on the fundamentals of foundation analysis and design Analysis and Design of Shallow and Deep Foundations is a significant new resource to the engineering principles used in the analysis and design of both shallow and deep, load-bearing foundations for a variety of building and structural types. Its unique presentation focuses on new developments in computer-aided analysis and soil-structure interaction, including foundations as deformable bodies. Written by the world's leading foundation engineers, Analysis and Design of Shallow and Deep Foundations covers everything from soil investigations and loading analysis to major types of foundations and construction methods. It also features: * Coverage on computer-assisted analytical methods, balanced with standard methods such as site visits and the role of engineering geology * Methods for computing the capacity and settlement of both shallow and deep foundations * Field-testing methods and sample case studies, including projects where foundations have failed, supported with analyses of the failure * CD-ROM containing demonstration versions of analytical geotechnical software from Ensoft, Inc. tailored for use by students in the classroom
