The Experts below are selected from a list of 115305 Experts worldwide ranked by ideXlab platform
Izuru Takewaki - One of the best experts on this subject based on the ideXlab platform.
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worst case analysis for earthquake energy input rate in sdof and mdof structures
Advances in Structural Engineering, 2006Co-Authors: Izuru TakewakiAbstract:Possible realization of earthquake ground motion and its effects on structures are very uncertain even with the accumulated knowledge. It is therefore desirable to develop a robust Structural Design Method taking into account these uncertainties. Under these circumstances worst excitation approaches have been proven to be promising. A new worst-case analysis Method is developed here in which the mean value of the earthquake energy input rate is chosen as a measure of criticality. The concepts of statistical input energy and statistical input rate are new directions. The non-stationary ground motion is described as a uniformly modulated non- stationary random process. The power and the intensity of the input ground motion are bounded and the worst excitation is found under these restrictions. The key for solving the problem is the interchange of the order of the double maximization procedures with respect to time and to the power spectral density function. It is further shown that the formulation in single-degree-of-freedom models can be extended to multi-degree- of-freedom models with proportional damping. Examples for a specific envelope function of the non-stationary ground motion are presented in single and multi-degree- of-freedom models for demonstrating the validity of the Method.
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Probabilistic Critical Excitation Method for Earthquake Energy Input Rate
Journal of Engineering Mechanics, 2006Co-Authors: Izuru TakewakiAbstract:Since earthquake ground motions and their input effects on structures are very uncertain even with the present state of knowledge, it is desirable to develop a “robust” Structural Design Method taking into account these uncertainties. Approaches based on critical excitation Methods have been proven to be promising for such robust Structural Design. A new critical excitation Method is developed here in which the mean earthquake energy input rate is chosen as a measure of criticality. The earthquake energy input rate is closely correlated with the story deformation and this supports the suitability of the energy input rate as a criticality measure in the case where the deformation is crucial in the Design. The ground motion is described as a uniformly modulated nonstationary random process. The power [area of power spectral density (PSD) function] and the intensity (magnitude of PSD function) are fixed and the critical excitation is found under these restrictions. The key for finding the new random critical...
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critical excitation for elastic plastic structures via statistical equivalent linearization
Probabilistic Engineering Mechanics, 2002Co-Authors: Izuru TakewakiAbstract:Abstract Since earthquake ground motions and their effects on Structural responses are very uncertain even with the present knowledge, it is desirable to develop a robust Structural Design Method taking into account these uncertainties. Critical excitation approaches are promising and a new random critical excitation Method for single-degree-of-freedom (SDOF) elastic–plastic structures is proposed. The power (area of power spectral density (PSD) function) and the intensity (magnitude of PSD function) are fixed and the critical excitation is found under these restrictions. In contrast to linear elastic structures, transfer functions and related simple expressions for response evaluation cannot be defined in elastic–plastic structures and difficulties arise in describing the peak responses except elastic–plastic time-history response analysis. Statistical equivalent linearization is utilized to estimate the elastic–plastic stochastic peak responses approximately. The critical excitations are obtained for two examples and compared with the corresponding recorded earthquake ground motions.
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probabilistic critical excitation for mdof elastic plastic structures on compliant ground
Earthquake Engineering & Structural Dynamics, 2001Co-Authors: Izuru TakewakiAbstract:Earthquake ground motions and their effects on Structural responses are very uncertain even with the present knowledge. It is therefore desirable to develop a robust Structural Design Method taking into account these uncertainties. Critical excitation approaches are promising and a new random critical excitation Method is proposed for MDOF elastic–plastic shear-building structures on compliant ground. The power (area of power spectral density (PSD) function) and the intensity (magnitude of PSD function) are fixed and the critical excitation is found under these restrictions. In contrast to linear elastic structures, transfer functions and simple expressions for response evaluation cannot be defined in elastic–plastic structures and difficulties arise in describing the peak responses except by laborious elastic–plastic time-history response analysis. Statistical equivalent linearization is used to estimate the elastic–plastic stochastic peak responses approximately. The critical excitation responses are obtained for several examples and compared with those of the corresponding recorded earthquake ground motion. Copyright © 2001 John Wiley & Sons, Ltd.
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a new Method for non stationary random critical excitation
Earthquake Engineering & Structural Dynamics, 2001Co-Authors: Izuru TakewakiAbstract:Since earthquake ground motions are very uncertain even with the present knowledge, it is desirable to develop a robust Structural Design Method taking into account these uncertainties. Critical excitation approaches are promising and a new non-stationary random critical excitation Method is proposed. In contrast to the conventional critical excitation Methods, a stochastic response index is treated as the objective function to be maximized. The power (area of power spectral density (PSD) function) and the intensity (magnitude of PSD function) are fixed and the critical excitation is found under these restrictions. It is shown that the original idea for stationary random inputs can be utilized effectively in the procedure for finding a critical excitation for non-stationary random inputs. The key for finding the new non-stationary random critical excitation is the exchange of the order of the double maximization procedures with respect to time and to the power spectral density function. Copyright © 2001 John Wiley & Sons, Ltd.
Edwards, John Riley - One of the best experts on this subject based on the ideXlab platform.
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Quantification of prestressed concrete railway crosstie flexural response: Implications for mechanistic Design
2021Co-Authors: Edwards, John RileyAbstract:Concrete is the dominant crosstie material choice for demanding locations on heavy axle load (HAL) freight railroads with steep grades, sharp curves, and high annual gross tonnage. Concrete crossties are also used in rail transit applications where safety and reliability of infrastructure is at a premium and maintenance time is often limited. As such, development and implementation of a Structural Design Method that enables optimization of crosstie Design for varied applications and loading environments will reduce initial capital cost and recurring maintenance expense. Center flexural cracking is one of the most common factors limiting the service life of concrete crossties in North America, and rail seat cracking has been documented as a performance concern. Improving the understanding of crosstie flexure can help reduce the occurrences of cracked crossties by ensuring that Designs conform to the field conditions in which they are used. To date, few Methods have been proposed to accurately quantify the revenue service field bending moments of concrete crossties and their variability due to support conditions and other factors. This dissertation describes the development, deployment, and validation of a Method to quantify crosstie bending moments using concrete surface strain gauges. Data collected using this Method at field installations throughout the United States were used to investigate the effects of thermal gradient, axle load, axle location, support condition, and rail mode on crosstie bending moments. Results indicated that thermal gradient is significant and should be considered in crosstie flexural Design, especially at the crosstie center. Additionally, crosstie support condition is the largest source of variability in crosstie bending moments and its effect is most pronounced on HAL freight railroads. The field results indicated the need for development and application of a probabilistic Design Method for the flexural capacity of concrete crossties. I developed a Design process based on Structural reliability analysis concepts whereby target values for reliability indices (β) for new Designs are obtained and compared with existing Designs for further Design optimization. New (proposed) Designs are more economical, having a center negative moment capacity reduction of 50% for heavy rail transit. For HAL freight, a reduction in rail seat bending capacity of approximately 40% is justified, reducing the size of the rail seat cross section by approximately the same magnitude. In most cases the proposed Designs for both rail modes have fewer prestressing wires and a higher centroid of prestressing steel. In all cases the flexural capacities at the crosstie center and rail seat are better balanced from a Structural reliability standpoint. The probabilistic Method using Structural reliability analysis fundamentals that is proposed and demonstrated in this dissertation constitutes a critical step in the development of mechanistic-empirical practices for the Design of concrete crossties. Additionally, this framework for probabilistic Design provides a foundation for the future application of mechanistic-empirical Design practices to other railway track components.U of I OnlyAuthor requested U of Illinois access only (OA after 2yrs) in Vireo ETD syste
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Quantification of prestressed concrete railway crosstie flexural response: Implications for mechanistic Design
2019Co-Authors: Edwards, John RileyAbstract:Concrete is the dominant crosstie material choice for demanding locations on heavy axle load (HAL) freight railroads with steep grades, sharp curves, and high annual gross tonnage. Concrete crossties are also used in rail transit applications where safety and reliability of infrastructure is at a premium and maintenance time is often limited. As such, development and implementation of a Structural Design Method that enables optimization of crosstie Design for varied applications and loading environments will reduce initial capital cost and recurring maintenance expense. Center flexural cracking is one of the most common factors limiting the service life of concrete crossties in North America, and rail seat cracking has been documented as a performance concern. Improving the understanding of crosstie flexure can help reduce the occurrences of cracked crossties by ensuring that Designs conform to the field conditions in which they are used. To date, few Methods have been proposed to accurately quantify the revenue service field bending moments of concrete crossties and their variability due to support conditions and other factors. This dissertation describes the development, deployment, and validation of a Method to quantify crosstie bending moments using concrete surface strain gauges. Data collected using this Method at field installations throughout the United States were used to investigate the effects of thermal gradient, axle load, axle location, support condition, and rail mode on crosstie bending moments. Results indicated that thermal gradient is significant and should be considered in crosstie flexural Design, especially at the crosstie center. Additionally, crosstie support condition is the largest source of variability in crosstie bending moments and its effect is most pronounced on HAL freight railroads. The field results indicated the need for development and application of a probabilistic Design Method for the flexural capacity of concrete crossties. I developed a Design process based on Structural reliability analysis concepts whereby target values for reliability indices (β) for new Designs are obtained and compared with existing Designs for further Design optimization. New (proposed) Designs are more economical, having a center negative moment capacity reduction of 50% for heavy rail transit. For HAL freight, a reduction in rail seat bending capacity of approximately 40% is justified, reducing the size of the rail seat cross section by approximately the same magnitude. In most cases the proposed Designs for both rail modes have fewer prestressing wires and a higher centroid of prestressing steel. In all cases the flexural capacities at the crosstie center and rail seat are better balanced from a Structural reliability standpoint. The probabilistic Method using Structural reliability analysis fundamentals that is proposed and demonstrated in this dissertation constitutes a critical step in the development of mechanistic-empirical practices for the Design of concrete crossties. Additionally, this framework for probabilistic Design provides a foundation for the future application of mechanistic-empirical Design practices to other railway track components
William F Hunt - One of the best experts on this subject based on the ideXlab platform.
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Structural hydrologic Design and maintenance of permeable interlocking concrete pavement
2010 Green Streets and Highways ConferenceAmerican Society of Civil Engineers, 2010Co-Authors: David R Smith, William F HuntAbstract:Permeable interlocking concrete pavements (PICP) combine stormwater infiltration, detention and a riding surface for vehicles into one location. These pavements rely on an open-graded crushed stone base for storage, infiltration and vehicular support. Much research has been conducted on the hydrologic and water quality aspects. State and municipal best management practices (BMP) and low impact development (LID) manuals have incorporated Design guidelines developed from university research, industry guidelines and experience by various agencies, project owners, civil engineers and contractors. This paper integrates hydrological and Structural Design for PICP for potential use in the emerging American Society of Civil Engineers (ASCE) guidelines for permeable pavement. Hydrological analysis determines if the volume of water from user-selected rainfall events can be stored and released by the pavement base. Designer-selected parameters determine how much water infiltrates the soil subgrade and/or is carried away by subdrains. Structural capacity for vehicular loads is determined using PICP industry Design charts or the American Association of State Highway and Transportation Officials (AASHTO) 1993 Structural Design Method. This paper includes Design examples using these Methodologies with an example using Design software. The paper includes input Design considerations as well as outputs for stormwater drainage and pavement Design. In addition, recent experience is summarized on surface cleaning and surface repair.
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Structural hydrologic Design and maintenance of permeable interlocking concrete pavement
Low Impact Development International Conference (LID) 2010American Society of Civil EngineersCalifornia State Water Resources Control BoardCalifornia , 2010Co-Authors: David R Smith, William F HuntAbstract:Permeable interlocking concrete pavements (PICP) combine stormwater infiltration, detention and a riding surface for vehicles into one location. These pavements rely on an open-graded crushed stone base for storage, infiltration and vehicular support. Much research has been conducted on the hydrologic and water quality aspects. State and municipal BMP (best management practices) and LID (low impact development) manuals have incorporated Design guidelines developed from university research, industry guidelines and experience by various agencies, project owners, civil engineers and contractors. This paper integrates hydrological and Structural Design for PICP for potential use in the emerging ASCE guidelines for permeable pavement. Hydrological analysis determines if the volume of water from user-selected rainfall events can be stored and released by the pavement base. Designer-selected parameters determine how much water infiltrates the soil subgrade and/or is carried away by subdrains. Structural capacity for vehicular loads is determined using PICP industry Design charts or the American Association of State Highway and Transportation Officials (AASHTO) 1993 Structural Design Method. This paper includes Design examples using these Methodologies with an example using Design software. The paper includes input Design considerations as well as outputs for stormwater drainage and pavement Design. In addition, recent experience is summarized on surface cleaning and surface repair.
David R Smith - One of the best experts on this subject based on the ideXlab platform.
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Structural hydrologic Design and maintenance of permeable interlocking concrete pavement
2010 Green Streets and Highways ConferenceAmerican Society of Civil Engineers, 2010Co-Authors: David R Smith, William F HuntAbstract:Permeable interlocking concrete pavements (PICP) combine stormwater infiltration, detention and a riding surface for vehicles into one location. These pavements rely on an open-graded crushed stone base for storage, infiltration and vehicular support. Much research has been conducted on the hydrologic and water quality aspects. State and municipal best management practices (BMP) and low impact development (LID) manuals have incorporated Design guidelines developed from university research, industry guidelines and experience by various agencies, project owners, civil engineers and contractors. This paper integrates hydrological and Structural Design for PICP for potential use in the emerging American Society of Civil Engineers (ASCE) guidelines for permeable pavement. Hydrological analysis determines if the volume of water from user-selected rainfall events can be stored and released by the pavement base. Designer-selected parameters determine how much water infiltrates the soil subgrade and/or is carried away by subdrains. Structural capacity for vehicular loads is determined using PICP industry Design charts or the American Association of State Highway and Transportation Officials (AASHTO) 1993 Structural Design Method. This paper includes Design examples using these Methodologies with an example using Design software. The paper includes input Design considerations as well as outputs for stormwater drainage and pavement Design. In addition, recent experience is summarized on surface cleaning and surface repair.
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Structural hydrologic Design and maintenance of permeable interlocking concrete pavement
Low Impact Development International Conference (LID) 2010American Society of Civil EngineersCalifornia State Water Resources Control BoardCalifornia , 2010Co-Authors: David R Smith, William F HuntAbstract:Permeable interlocking concrete pavements (PICP) combine stormwater infiltration, detention and a riding surface for vehicles into one location. These pavements rely on an open-graded crushed stone base for storage, infiltration and vehicular support. Much research has been conducted on the hydrologic and water quality aspects. State and municipal BMP (best management practices) and LID (low impact development) manuals have incorporated Design guidelines developed from university research, industry guidelines and experience by various agencies, project owners, civil engineers and contractors. This paper integrates hydrological and Structural Design for PICP for potential use in the emerging ASCE guidelines for permeable pavement. Hydrological analysis determines if the volume of water from user-selected rainfall events can be stored and released by the pavement base. Designer-selected parameters determine how much water infiltrates the soil subgrade and/or is carried away by subdrains. Structural capacity for vehicular loads is determined using PICP industry Design charts or the American Association of State Highway and Transportation Officials (AASHTO) 1993 Structural Design Method. This paper includes Design examples using these Methodologies with an example using Design software. The paper includes input Design considerations as well as outputs for stormwater drainage and pavement Design. In addition, recent experience is summarized on surface cleaning and surface repair.
Yasushi Hasegawa - One of the best experts on this subject based on the ideXlab platform.
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a milp decomposition approach to large scale optimization in Structural Design of energy supply systems
Energy Conversion and Management, 2002Co-Authors: Yasushi HasegawaAbstract:Abstract An optimal Structural Design Method is proposed to determine the structures of energy supply systems in consideration of their multi-period operation. The optimization problem is formulated as a large scale mixed integer linear programming (MILP) problem with binary variables for selection and on/off status of operation of equipment and continuous variables for capacities and load allocation of equipment. The dependence of the performance characteristics of equipment on their capacities and part loads, as well as that of capital costs of equipment on their capacities, are incorporated into the optimization model. A decomposition Method of solving MILP problems with the block angular structure is applied to derive a suboptimal solution close to the optimal one in a short computation time. The meaning and validity of the decomposition Method are clarified through an analytical study on an energy supply system with a simple structure. The validity and effectiveness of the decomposition Method are also clarified in terms of solution optimality and computation time through a numerical study on another energy supply system with a complex structure.
