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Author: Awilda M. Blanco Publisher: ISBN: Category : Electronic dissertations Languages : en Pages : 161
Book Description
Approximately 40 years ago, researchers started to use probability theory to develop a more rational basis for civil engineering design. New methods like Load and Resistance Factor Design (LRFD) allowed for the use of factors to increase the load effect (load factors) and decrease the calculated resistance (resistance factors) for the structure to account for uncertainty in these parameters. The initial main approach for developing resistance factors for geotechnical design was to adjust the resistance factors to be consistent to the factors of safety used for design in the allowable stress design (ASD) methodology. The latest efforts involved the development of resistance factors based on driven pile and drilled shaft information from a national database, but further uncertainties remain due to individual site conditions, among others. Although the vertical soil variability has been modeled and included in design, the horizontal soil variability for the design of driven piles should not be determined using the same models. The main objective of this research is to characterize the soil variability in the horizontal direction at an alluvial site. The variability is included in the determination of LRFD resistance factors for the design of driven piles. Different methodologies are presented to attempt to describe the horizontal soil variability to provide guidance to designers on how to divide any site based on this variability. An example is presented on how these methodologies can be applied to design structures either within a distance where information is available or outside the distance where information is available.
Author: Awilda M. Blanco Publisher: ISBN: Category : Electronic dissertations Languages : en Pages : 161
Book Description
Approximately 40 years ago, researchers started to use probability theory to develop a more rational basis for civil engineering design. New methods like Load and Resistance Factor Design (LRFD) allowed for the use of factors to increase the load effect (load factors) and decrease the calculated resistance (resistance factors) for the structure to account for uncertainty in these parameters. The initial main approach for developing resistance factors for geotechnical design was to adjust the resistance factors to be consistent to the factors of safety used for design in the allowable stress design (ASD) methodology. The latest efforts involved the development of resistance factors based on driven pile and drilled shaft information from a national database, but further uncertainties remain due to individual site conditions, among others. Although the vertical soil variability has been modeled and included in design, the horizontal soil variability for the design of driven piles should not be determined using the same models. The main objective of this research is to characterize the soil variability in the horizontal direction at an alluvial site. The variability is included in the determination of LRFD resistance factors for the design of driven piles. Different methodologies are presented to attempt to describe the horizontal soil variability to provide guidance to designers on how to divide any site based on this variability. An example is presented on how these methodologies can be applied to design structures either within a distance where information is available or outside the distance where information is available.
Author: Samuel G. Paikowsky Publisher: Transportation Research Board ISBN: 0309087961 Category : Bridges Languages : en Pages : 87
Book Description
Introduction and research approach -- Findings -- Interpretation, appraisal, and applications -- Conclusions and suggested research -- Bibliography -- Appendixes.
Author: Haijian Fan Publisher: ISBN: Category : Civil engineering Languages : en Pages : 177
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: George G. Goble Publisher: Transportation Research Board ISBN: 9780309068543 Category : Bridges Languages : en Pages : 80
Book Description
This synthesis report will be of interest to geotechnical, structural, and bridge engineers, especially those involved in the development and implementation of the geotechnical aspects of the AASHTO Bridge Code. The synthesis documents a review of geotechnical related LRFD specifications and their development worldwide to compare them with the current AASHTO LRFD Bridge Code. Design procedures for foundations, earth retaining structures, and culverts are summarized and compared with the methods specified by the AASHTO code. This TRB report provides information designed to assist engineers in implementing the geotechnical features of LRFD methods. Information for the synthesis was collected by surveying U.S. and Canadian transportation agencies and by conducting a literature search using domestic and international sources. Interviews were also conducted with selected international experts. The limited available experience in the United States and information from international practice are discussed to understand the problems that have arisen in order that solutions may be found. Based on the studies reported here, suggestions for improving the code are identified.
Author: Lance Alan Roberts Publisher: ISBN: Category : Foundations Languages : en Pages : 414
Book Description
The analysis of deep foundations at the service limit state is important when foundation settlements are critical to the operation of a structure. The "t-z" method is a widely used soil-structure interaction model for the analysis of deep foundation settlement. In current practice, nominal values of soil-structure interface stiffness and strength parameters are used to determine the deep foundation settlement based on the "t-z" method. However, the nominal magnitude and variability of these parameters can vary from one designer or site to another, thus making the settlement results somewhat subjective. By considering reliability-based design principals, probabilistic relationships can be rationally incorporated into the settlement analysis of deep foundations, and thus, design uncertainty can be quantified. Along this approach, Load and Resistance Factor Design (LRFD) procedures may be utilized to develop resistance factors for use in design. Utilizing a "t-z" model and the Monte Carlo simulation process, various types of probabilistic solutions are developed for deep foundation axial capacity at the service limit state. To model the soil-structure interaction, ideal elasto-plastic and hyperbolic load displacement behavior of the soil-structure interface is considered for both total stress (undrained) and effective stress (drained) analyses. Consequently, resistance factors, appropriate for design in AASHTO LRFD applications, are calculated utilizing the developed probabilistic load capacity relationships for deep foundations. A parametric study is completed, in which the geometry of the deep foundation element and the soil-structure interface parameters are varied to understand their effect on the magnitude of the resistance factors. Finally, load displacement data for a series of micropile pullout tests is utilized to demonstrate and validate the developed service limit state probabilistic design approach for standard deep foundation design.
Author: Masaki Kitazume Publisher: CRC Press ISBN: 0203589637 Category : Technology & Engineering Languages : en Pages : 436
Book Description
The Deep Mixing Method (DMM), a deep in-situ soil stabilization technique using cement and/or lime as a stabilizing agent, was developed in Japan and in the Nordic countries independently in the 1970s. Numerous research efforts have been made in these areas investigating properties of treated soil, behavior of DMM improved ground under static and d
Author: Donald P. Coduto Publisher: Pearson Higher Ed ISBN: 1292052430 Category : Technology & Engineering Languages : en Pages : 889
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: Magued Iskander Publisher: ISBN: 9780784410219 Category : Electronic books Languages : en Pages : 0
Book Description
GSP 185 contains 80 papers presented at the International Foundation Congress and Equipment Expo held in Orlando, Florida, March 15-19, 2009.
Author: Awilda M. Blanco
Author: Awilda M. Blanco
Author: Samuel G. Paikowsky
Author: Haijian Fan
Author: George G. Goble
Author: Lance Alan Roberts
Author: Masaki Kitazume
Author: 
Author: Donald P. Coduto
Author: Mehrangiz Naghibi
Author: Magued Iskander