The Experts below are selected from a list of 303 Experts worldwide ranked by ideXlab platform

Jeffrey Scott - One of the best experts on this subject based on the ideXlab platform.

  • Operational Aspects of Quality-of-Life Assessment
    PharmacoEconomics, 1995
    Co-Authors: Pennifer Erickson, Richard C. Taeuber, Jeffrey Scott
    Abstract:

    In assessing quality of life, the most important goal is to develop a strategy that produces useable and useful inFormation for decision making. Assessment Design is complex, and whether an assessment is developed from scratch, or 1 or more portions of existing instruments are adapted, the focus must be on the quality of the theoretical and operational elements of the particular line of inquiry and its environment. The necessary and most often discussed focus on the theoretical dimensions of validity, reliability and responsiveness is not sufficient to insure that the data are of the requisite high quality. There is also a need, almost universally given little attention in the literature, to look at operational aspects, such as Design, Format, flow, appearance, and response-stimulus, of each assessment instrument. Searching for guidance in the quality-of-life (QOL) literature remains a challenge even with computers, modems, keywords, static guidebooks and bibliographic systems. The On-Line Guide to Quality-of-Life Assessments (OLGA) is presented as a personal computer-based system that is updated 3 times a year to provide QOL researchers and assessment developers with 2 databases: assessments providing full descriptions and contact inFormation; and references providing fully keyed citations to the assessment use literature. These databases are made more useful by decision-logical programs that identify relevant assessments and supporting research literature. OLGA can thus save time and other resources by helping investigators concentrate on the most relevant elements of the existing literature. This focus will assist them in avoiding the problems of ending up with the right answers to the wrong questions.

Hyung Bae Kim - One of the best experts on this subject based on the ideXlab platform.

  • Practical Probabilistic Design Format for Flexible Pavements
    Transportation Research Record, 2006
    Co-Authors: Hyung Bae Kim
    Abstract:

    Mechanistic-empirical (M-E) pavement Design procedures such as the AASHTO 2002 Design guide have been widely accepted and are being implemented by many highway agencies. However, several issues need to be resolved before this implementation is completed. One issue is that the Design procedure should provide a consistent pavement performance level considering inherent variability associated with Design input parameters. For a complete M-E pavement Design procedure, the effects of the inherent variability of input Design parameters on predicted pavement performance must be addressed and quantified. Some key principles for applying the reliability concept to M-E pavement Design are presented to account for the inherent variability of Design parameters. In particular, an appropriate reliability assessment technique and careful characterization of Design input variability were considered because of their central role in calculating the reliability of pavement performance. Finally, a practical probabilistic des...

  • Development of load and resistance factor Design Format for flexible pavements
    Canadian Journal of Civil Engineering, 1998
    Co-Authors: Hyung Bae Kim, Ronald S. Harichandran, Neeraj Buch
    Abstract:

    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 form...

Abdul-hamid Zureick - One of the best experts on this subject based on the ideXlab platform.

  • PROBABILISTIC BASED Design OF CONCENTRICALLY LOADED FIBER-REINFORCED POLYMERIC COMPRESSION MEMBERS
    Journal of Structural Engineering-asce, 2004
    Co-Authors: Maha Alqam, Richard M. Bennett, Abdul-hamid Zureick
    Abstract:

    This paper presents an analytical probabilistic based Design procedure for concentrically loaded compression members of fiber-reinforced polymeric composite materials. Resistance factors for use in a load and resistance factor Design Format are developed for flexural buckling of doubly symmetric sections, both flexural buckling and flexural-torsional buckling of equal leg angles, and material failure. The developed resistance factors are a function of the coefficient of variation of the appropriate material properties. The proposed resistance factors were determined to provide a reliability index of 3.0 for buckling limit states and a reliability index of 3.5 for the material fracture limit state. A proposed method of developing an allowable stress Design code is also given.

Masayoshi Nakashima - One of the best experts on this subject based on the ideXlab platform.

  • Variation of Ductility Capacity of Steel Beam‐Columns
    Journal of Structural Engineering-asce, 1994
    Co-Authors: Masayoshi Nakashima
    Abstract:

    This paper presents an investigation on the variation of ductility capacity of steel beam-columns. First, experimental data obtained from previous tests are surveyed, and their ductility ratios are examined. It is found that experimental ductility ratios scatter over a wide range with their coefficients of variation ranging from 0.4 to 0.9. Next, nonlinear numerical analysis is carried out with slenderness, axial force, strain hardening, residual stresses, and initial out-of-straightness as variables. The analysis reveals that neither residual stresses nor initial out-of-straightness is a major factor affecting the ductility ratio, but strain hardening is very influential on the ductility ratio, suggesting that strain hardening is one of the major sources for the large variation in the experimental ductility ratio. A guideline is also presented for estimating ductilty ratios of steel beam-columns. Finally, problems associated with large variation in the ductilty capacity of steel beam-columns are discussed with reference to the reliability Design Format.

Sven Thelandersson - One of the best experts on this subject based on the ideXlab platform.

  • experimental investigation on the effect of detail Design on wood moisture content in outdoor above ground applications
    Building and Environment, 2013
    Co-Authors: Tord Isaksson, Sven Thelandersson
    Abstract:

    An essential part of a performance-based service life Design Format for wood exposed in outdoor applications is the effect of proper detailing in terms of avoiding moisture traps. Models for predicting degradation and non-performance caused by decay are functions of arbitrary climate history of combined moisture content and temperature. Therefore it is crucial to be able to predict the behaviour of different detailing in terms of moisture content exposed to outdoor climate. An experimental study was made with continuous moisture content measurements of different details. The different detail set-ups are selected to represent a wide range of sawn timber dimension details of non-treated Norway spruce. Hourly moisture content values are recorded by a wireless monitoring system and the climate is monitored using a weather station. A simple horizontal board with no detailing is chosen as reference detail. This is, apart from a vertical board and sheltered details, what can be expected to be a good detail in terms of not trapping water. The remaining details show higher moisture content levels. It was found that the ratio between moisture content in a detail and in the reference detail showed a reasonably constant value over time. Consequently the behaviour of an arbitrary detail can be estimated by scaling the behaviour of the reference detail up or down using a constant value. Depending on the Design the constant will be higher for more water trapping details and vice versa. This is important inFormation and input for evaluating and developing details with acceptable performance. (C) 2012 Elsevier Ltd. All rights reserved. (Less)

  • Critical conditions for onset of mould growth under varying climate conditions
    Building and Environment, 2010
    Co-Authors: Tord Isaksson, Sven Thelandersson, Annika Ekstrand-tobin, Pernilla Johansson
    Abstract:

    A performance-based service life Design Format based on climatic exposure on one hand and "resistance" of materials against mould growth on the other hand, is presented in this paper. A limit state for onset of mould growth is defined as the occurrence of traces of mould observed by microscopy. A dose-response model is proposed by which onset of mould growth can be predicted for an arbitrary climate history of combined relative humidity phi and temperature T. The model is calibrated and verified against a comprehensive set of experimental data published by Viitanen et al. [Viitanen H, Ritschkoff A-C. Mould growth in pine and spruce sapwood in relation to air humidity and temperature. Uppsala: Swedish University of Agricultural Sciences, Department of Forest Products; 1991. Report No. 221, 49 p.: Viitanen H. Modelling the time factor in the development of mould fungi - effect of critical humidity and temperature conditions in pine and spruce sapwood. Holzforschung 1997;51(1):6-14; Viitanen H. Modelling the time factor in the development of brown rot decay in pine and spruce sapwood - the effect of critical humidity and temperature conditions. Holzforschung 1997:51(2):99-106; Viitanen H. Bjurman J. Mould growth on wood under fluctuating humidity conditions. Material und Organismen 1995;29(1):27-46] describing mould development on spruce and pine sapwood as a function of climatic exposure. The model is applied to predict time to onset of mould growth under natural outdoor climate (under shelter) as well as mould development in building attics and in crawl space foundations. The predicted response shows reasonable agreement with experimental observations and proven experience, although biological processes of this type display great variability. The results show that a generally applicable, quantitative model can be used as a powerful tool for moisture safe Design in practice. The model is Designed to facilitate continuous improvement of prediction capability by further laboratory testing of various materials under specified climate conditions. In combination with currently available building physics software the model is suitable for moisture safe Design of wood-based components in the building envelope. (C) 2010 Elsevier Ltd. All rights reserved. (Less)