Shifferaw Taye - Academia.edu (original) (raw)
Papers by Shifferaw Taye
Zede Journal, 2005
Composite columns are in an increased usage for construction of high-rise and medium-rise buildin... more Composite columns are in an increased usage for construction of high-rise and medium-rise buildings, bridges and other structures. However, their design procedure as proposed by the relevant Ethiopian Building Code Standard, which is also a derivative of the corresponding European Standard Eurocode 4 calls for extensive numerical effort for drawing the moment -axial-force interaction charts. Furthermore, the results obtained following those procedures are based on curve-fitting techniques making use of widely sparse control points and, consequently, they produce approximate results. This paper explores the shortcomings' of the relevant local building code standard for the design process and presents improved design chart procedures for concrete-filled rectangular steel tube columns. The proposed procedure simplifies the design process and, at the same time, considerably increases the accuracy of results. A unified approach has been presented for the procedure of establishing int...
Zede Journal, 2004
Approximate structural reanalysis methods have long been pursued in quest for efficiency so as to... more Approximate structural reanalysis methods have long been pursued in quest for efficiency so as to enhance their practical' application in the assessment and verification of designs following design modifications, These have been of significant practical importance with particular emphasis on design optimization of large-scale structural systems in which thousands of design modifications need to be carried out during the search operation to identifY optimal systems, However, the consequential problems of accuracy and reliability call for the development of better-quality mathematical models that enhance computational quality while keeping the computational effort at afraction of what might be required if complete and exact analysis would be carried out. This paper presents an efficient structural reanalysis mathematical model that is based on the flexibility method and exhibits high approximation qualities in evaluating structural responses of a newly proposed design from those o...
Zede Journal, 1984
Scoria is found abundantly in Ethiopia. The use of scoria so far has been limited to highway cons... more Scoria is found abundantly in Ethiopia. The use of scoria so far has been limited to highway construction as a base course, as mortal aggregate in masnory con- 1truction and for the production of hollow concrete block1. However, 1coria, which can replace sand and cnuhed itone agsregate1, has not been u1ed in reinforced concrete comtructiom. Thi& may be attributed to lack of sufficient technical data necessary for struc· turol design. The availability of scoria in large quantitie1, where sand ii scarce and crushed stone is expemive, can have a significant reduction in cost in concrete construction. If the proper 1trengt·h parameters are identified and comtruction procedures of grain grading and concrete mixe1 are e1tabli&hed a cheap local building material could be introduced to the building industry. The purpose of thi& paper ii to present an exper· imental investigation on the strength of scoria concrete by replacing the normal siliceous sand (fine) aggregates by 1coria. The exp...
Computers & Structures, 1988
Efficient models for high quality approximations of forces in structural systems are presented. F... more Efficient models for high quality approximations of forces in structural systems are presented. Four approximate reanalysis models are developed and compared. These are First Order Approximations (FOA), Binomial Series Approximations (BSA), Improved First Order Approximations (IFOA), and Improved Binomial Series Approximations (IBSA) models. Each of these models is based on the results of a single exact analysis. Relationships among the models are derived and some of them are shown to be equivalent under certain assumptions. The improved versions are obtained by a procedure that employs scaling and norm minimization of certain matrices. This is also extended into explicit approximations in terms of a single variable introduced along a line in the design space. It is shown that poor results might be obtained by the FAO, BSA, and IFOA models. High quality approximations of forces are introduced by the IBSA model even for large and random changes in design variables. In most cases only the first two terms of the series are sufficient to obtain excellent results. Numerical examples are given to illustrate the performance of the proposed approximation models.
Computers & Structures, 1989
Engineering with Computers, 1986
Two problems of optimum topological design of gril-MLA, MLR lages are discussed: (1) the Equilibr... more Two problems of optimum topological design of gril-MLA, MLR lages are discussed: (1) the Equilibrium Linear Programming MN (ELP), where the analysis model is based only on equilibrium MQ conditions and (2) the Nonlinear Program (NLP), where the ELP formulation is extended to include compatibility conditions. The structural topology is optimized by allowing elimination of ele-MQA, MQR merits. Three different force method formulations are presented N for each of the problems.It is shown that the optimal topology for p
Structures Congress 2011, 2011
A new component-based, two-node, simplified, semi-rigid beam-to-column-connection element than ca... more A new component-based, two-node, simplified, semi-rigid beam-to-column-connection element than can easily be used in conjunction with many available structural-engineering software products is proposed for computer-oriented structural analysis. Relevant connection element properties, such as its stiffness matrices, have been established. The proposed model circumvents the iterative procedure proposed by several code standards for determining the resistance capacity and rotational stiffness of beam-to-column connections while at the same time it also alleviates the inapplicability of four-node elements that have been proposed by several researchers for use in commonly available high-end structural engineering software products. In the process of formulating the analytical model, panel shear deformation of the joint has been taken care of by allowing the joint region of the column to undergo shear deformation. Numerical experience has been gained by processing several frame structural models. Application will be demonstrated using the general purpose finite element package ANSYS by way of applying to study a typical frame. Results have also been compared with those obtained by other researchers and a high-quality correlation between and among results have been obtained. In all cases, values obtained by the proposed two-node connection model have been acceptable for design purpose.
SINET: Ethiopian Journal of Science, 2006
Computers & Structures, 1991
Abstract An approximate structural reanalysis method that is based on a binomial series expansion... more Abstract An approximate structural reanalysis method that is based on a binomial series expansion and that employs operations of matrix scaling and norm minimization is presented in this paper. It is shown that the scaling operation significantly reduces several unfavourable effects of the magnitude and nature of design changes on the prediction quality of the model. Norm minimization provides a very effective and optimal scaling factor in a simplified manner. The most significant achievement of the work is the development of an effective and efficient reanalysis model that provides near-exact response quantities even when large and strongly dispersed changes are introduced in the design. The potential capacity of the proposed method of improvement is demonstrated using numerical examples. Graphical interpretation of the concept is also provided.
Zede Journal, 2015
A numerical study has been conducted to determine the quality of blast load simulation for non-li... more A numerical study has been conducted to determine the quality of blast load simulation for non-linear dynamic response analysis of framed structures subjected to such loads at various stand-off distances with due consideration to the provisions and requirements of Unified Facility Criteria UFC 2005. Simulation has been carried out using a general-purpose, commercial software system and a special-purpose, blast-specific software product to assess and compare the quality of response prediction of such computational models. Nonlinear dynamic analysis has been performed using a three-dimensional model of a structure and its corresponding elasto-plastic analysis on its single-degree-of-freedom representation. The results obtained for different positions of explosive charges under the two analysis models have been presented. A comparative analysis of the results indicates that the quality of blast load simulation and associated structural response depend both on the analysis model of choi...
Zede Journal, 1993
An integrated analysis-synthesis software package that is based on the Fortran-90 standards is de... more An integrated analysis-synthesis software package that is based on the Fortran-90 standards is developed for the design optimization of framed structures - continuous beams, plane and space trusses and rigid frames, grids and composite truss-rigid frames. The package will enable the structural engineer to effectively and efficiently isolate designs that are better than alternative designs with minimal interaction and less computational effort. The capabilities of the package also include pure analysis and parametric studies. A numerical example will be presented to show the potential capabilities of the package.
The behavioral responses of sectorial shells as related to the number of modes and certain geomet... more The behavioral responses of sectorial shells as related to the number of modes and certain geometric properties of the shell have been studied. By varying certain dimensionless geometric properties of the shell and considering a series of undamped vibration modes, the influences of these properties on displacements, edge reactions, bending moments and other responses have been plotted and relevant conclusions reached. Two very important observations from this work are that, unlike in conventional regular building structures where the first mode is dominant in influencing various dynamic response behaviours and high-order modes affect less, the principal mode in sectorial shells fails to influence these responses while higher modes contribute progressively and significantly to those effects.
Computationally-efficient analytical procedure that provides high-quality analysis results for tw... more Computationally-efficient analytical procedure that provides high-quality analysis results for two-dimensional skeletal structure with segmented (stepped) and linearly-tapered non-prismatic flexural members has been developed based on the stiffness method of structural analysis. A computer program coded in FORTRAN 90 has been developed to facilitate the computational procedure. Concentrated and uniformly-distributed loads have been taken into consideration in the development of the computational procedure. The stiffness coefficients have been formulated employing both closed-form and numerical techniques. High quality computational procedures have been established to handle closed-form analytical solutions that have been observed to produce results that are close to theoretical values and that generally surpass those from commercially available software products. A numerical example has been presented to demonstrate the accuracy of the proposed computational procedure and related co...
SINET: Ethiopian Journal of Science, 2006
High quality moment-axial-force interaction diagrams have been developed for hexagonal and octago... more High quality moment-axial-force interaction diagrams have been developed for hexagonal and octagonal steel-concrete composite columns subjected to uniaxial bending. Comparative discussion with the procedures stipulated in relevant building code standards has been presented. A unified approach has been presented for the procedure of establishing design charts for concrete-filled steel tubes under uniaxial bending and valuable charts have been prepared for hexagonal and octagonal shape composite columns. This paper also outlines procedures that will enable preparation of similar design charts for other shapes and material types.
Structures Congress 2011, 2011
A new component-based, two-node, simplified, semi-rigid beam-to-column-connection element than ca... more A new component-based, two-node, simplified, semi-rigid beam-to-column-connection element than can easily be used in conjunction with many available structural-engineering software products is proposed for computer-oriented structural analysis. Relevant connection element properties, such as its stiffness matrices, have been established. The proposed model circumvents the iterative procedure proposed by several code standards for determining the resistance capacity and rotational stiffness of beam-to-column connections while at the same time it also alleviates the inapplicability of four-node elements that have been proposed by several researchers for use in commonly available high-end structural engineering software products. In the process of formulating the analytical model, panel shear deformation of the joint has been taken care of by allowing the joint region of the column to undergo shear deformation. Numerical experience has been gained by processing several frame structural models. Application will be demonstrated using the general purpose finite element package ANSYS by way of applying to study a typical frame. Results have also been compared with those obtained by other researchers and a high-quality correlation between and among results have been obtained. In all cases, values obtained by the proposed two-node connection model have been acceptable for design purpose.
Zede Journal, 2005
Composite columns are in an increased usage for construction of high-rise and medium-rise buildin... more Composite columns are in an increased usage for construction of high-rise and medium-rise buildings, bridges and other structures. However, their design procedure as proposed by the relevant Ethiopian Building Code Standard, which is also a derivative of the corresponding European Standard Eurocode 4 calls for extensive numerical effort for drawing the moment -axial-force interaction charts. Furthermore, the results obtained following those procedures are based on curve-fitting techniques making use of widely sparse control points and, consequently, they produce approximate results. This paper explores the shortcomings' of the relevant local building code standard for the design process and presents improved design chart procedures for concrete-filled rectangular steel tube columns. The proposed procedure simplifies the design process and, at the same time, considerably increases the accuracy of results. A unified approach has been presented for the procedure of establishing int...
Zede Journal, 2004
Approximate structural reanalysis methods have long been pursued in quest for efficiency so as to... more Approximate structural reanalysis methods have long been pursued in quest for efficiency so as to enhance their practical' application in the assessment and verification of designs following design modifications, These have been of significant practical importance with particular emphasis on design optimization of large-scale structural systems in which thousands of design modifications need to be carried out during the search operation to identifY optimal systems, However, the consequential problems of accuracy and reliability call for the development of better-quality mathematical models that enhance computational quality while keeping the computational effort at afraction of what might be required if complete and exact analysis would be carried out. This paper presents an efficient structural reanalysis mathematical model that is based on the flexibility method and exhibits high approximation qualities in evaluating structural responses of a newly proposed design from those o...
Zede Journal, 1984
Scoria is found abundantly in Ethiopia. The use of scoria so far has been limited to highway cons... more Scoria is found abundantly in Ethiopia. The use of scoria so far has been limited to highway construction as a base course, as mortal aggregate in masnory con- 1truction and for the production of hollow concrete block1. However, 1coria, which can replace sand and cnuhed itone agsregate1, has not been u1ed in reinforced concrete comtructiom. Thi& may be attributed to lack of sufficient technical data necessary for struc· turol design. The availability of scoria in large quantitie1, where sand ii scarce and crushed stone is expemive, can have a significant reduction in cost in concrete construction. If the proper 1trengt·h parameters are identified and comtruction procedures of grain grading and concrete mixe1 are e1tabli&hed a cheap local building material could be introduced to the building industry. The purpose of thi& paper ii to present an exper· imental investigation on the strength of scoria concrete by replacing the normal siliceous sand (fine) aggregates by 1coria. The exp...
Computers & Structures, 1988
Efficient models for high quality approximations of forces in structural systems are presented. F... more Efficient models for high quality approximations of forces in structural systems are presented. Four approximate reanalysis models are developed and compared. These are First Order Approximations (FOA), Binomial Series Approximations (BSA), Improved First Order Approximations (IFOA), and Improved Binomial Series Approximations (IBSA) models. Each of these models is based on the results of a single exact analysis. Relationships among the models are derived and some of them are shown to be equivalent under certain assumptions. The improved versions are obtained by a procedure that employs scaling and norm minimization of certain matrices. This is also extended into explicit approximations in terms of a single variable introduced along a line in the design space. It is shown that poor results might be obtained by the FAO, BSA, and IFOA models. High quality approximations of forces are introduced by the IBSA model even for large and random changes in design variables. In most cases only the first two terms of the series are sufficient to obtain excellent results. Numerical examples are given to illustrate the performance of the proposed approximation models.
Computers & Structures, 1989
Engineering with Computers, 1986
Two problems of optimum topological design of gril-MLA, MLR lages are discussed: (1) the Equilibr... more Two problems of optimum topological design of gril-MLA, MLR lages are discussed: (1) the Equilibrium Linear Programming MN (ELP), where the analysis model is based only on equilibrium MQ conditions and (2) the Nonlinear Program (NLP), where the ELP formulation is extended to include compatibility conditions. The structural topology is optimized by allowing elimination of ele-MQA, MQR merits. Three different force method formulations are presented N for each of the problems.It is shown that the optimal topology for p
Structures Congress 2011, 2011
A new component-based, two-node, simplified, semi-rigid beam-to-column-connection element than ca... more A new component-based, two-node, simplified, semi-rigid beam-to-column-connection element than can easily be used in conjunction with many available structural-engineering software products is proposed for computer-oriented structural analysis. Relevant connection element properties, such as its stiffness matrices, have been established. The proposed model circumvents the iterative procedure proposed by several code standards for determining the resistance capacity and rotational stiffness of beam-to-column connections while at the same time it also alleviates the inapplicability of four-node elements that have been proposed by several researchers for use in commonly available high-end structural engineering software products. In the process of formulating the analytical model, panel shear deformation of the joint has been taken care of by allowing the joint region of the column to undergo shear deformation. Numerical experience has been gained by processing several frame structural models. Application will be demonstrated using the general purpose finite element package ANSYS by way of applying to study a typical frame. Results have also been compared with those obtained by other researchers and a high-quality correlation between and among results have been obtained. In all cases, values obtained by the proposed two-node connection model have been acceptable for design purpose.
SINET: Ethiopian Journal of Science, 2006
Computers & Structures, 1991
Abstract An approximate structural reanalysis method that is based on a binomial series expansion... more Abstract An approximate structural reanalysis method that is based on a binomial series expansion and that employs operations of matrix scaling and norm minimization is presented in this paper. It is shown that the scaling operation significantly reduces several unfavourable effects of the magnitude and nature of design changes on the prediction quality of the model. Norm minimization provides a very effective and optimal scaling factor in a simplified manner. The most significant achievement of the work is the development of an effective and efficient reanalysis model that provides near-exact response quantities even when large and strongly dispersed changes are introduced in the design. The potential capacity of the proposed method of improvement is demonstrated using numerical examples. Graphical interpretation of the concept is also provided.
Zede Journal, 2015
A numerical study has been conducted to determine the quality of blast load simulation for non-li... more A numerical study has been conducted to determine the quality of blast load simulation for non-linear dynamic response analysis of framed structures subjected to such loads at various stand-off distances with due consideration to the provisions and requirements of Unified Facility Criteria UFC 2005. Simulation has been carried out using a general-purpose, commercial software system and a special-purpose, blast-specific software product to assess and compare the quality of response prediction of such computational models. Nonlinear dynamic analysis has been performed using a three-dimensional model of a structure and its corresponding elasto-plastic analysis on its single-degree-of-freedom representation. The results obtained for different positions of explosive charges under the two analysis models have been presented. A comparative analysis of the results indicates that the quality of blast load simulation and associated structural response depend both on the analysis model of choi...
Zede Journal, 1993
An integrated analysis-synthesis software package that is based on the Fortran-90 standards is de... more An integrated analysis-synthesis software package that is based on the Fortran-90 standards is developed for the design optimization of framed structures - continuous beams, plane and space trusses and rigid frames, grids and composite truss-rigid frames. The package will enable the structural engineer to effectively and efficiently isolate designs that are better than alternative designs with minimal interaction and less computational effort. The capabilities of the package also include pure analysis and parametric studies. A numerical example will be presented to show the potential capabilities of the package.
The behavioral responses of sectorial shells as related to the number of modes and certain geomet... more The behavioral responses of sectorial shells as related to the number of modes and certain geometric properties of the shell have been studied. By varying certain dimensionless geometric properties of the shell and considering a series of undamped vibration modes, the influences of these properties on displacements, edge reactions, bending moments and other responses have been plotted and relevant conclusions reached. Two very important observations from this work are that, unlike in conventional regular building structures where the first mode is dominant in influencing various dynamic response behaviours and high-order modes affect less, the principal mode in sectorial shells fails to influence these responses while higher modes contribute progressively and significantly to those effects.
Computationally-efficient analytical procedure that provides high-quality analysis results for tw... more Computationally-efficient analytical procedure that provides high-quality analysis results for two-dimensional skeletal structure with segmented (stepped) and linearly-tapered non-prismatic flexural members has been developed based on the stiffness method of structural analysis. A computer program coded in FORTRAN 90 has been developed to facilitate the computational procedure. Concentrated and uniformly-distributed loads have been taken into consideration in the development of the computational procedure. The stiffness coefficients have been formulated employing both closed-form and numerical techniques. High quality computational procedures have been established to handle closed-form analytical solutions that have been observed to produce results that are close to theoretical values and that generally surpass those from commercially available software products. A numerical example has been presented to demonstrate the accuracy of the proposed computational procedure and related co...
SINET: Ethiopian Journal of Science, 2006
High quality moment-axial-force interaction diagrams have been developed for hexagonal and octago... more High quality moment-axial-force interaction diagrams have been developed for hexagonal and octagonal steel-concrete composite columns subjected to uniaxial bending. Comparative discussion with the procedures stipulated in relevant building code standards has been presented. A unified approach has been presented for the procedure of establishing design charts for concrete-filled steel tubes under uniaxial bending and valuable charts have been prepared for hexagonal and octagonal shape composite columns. This paper also outlines procedures that will enable preparation of similar design charts for other shapes and material types.
Structures Congress 2011, 2011
A new component-based, two-node, simplified, semi-rigid beam-to-column-connection element than ca... more A new component-based, two-node, simplified, semi-rigid beam-to-column-connection element than can easily be used in conjunction with many available structural-engineering software products is proposed for computer-oriented structural analysis. Relevant connection element properties, such as its stiffness matrices, have been established. The proposed model circumvents the iterative procedure proposed by several code standards for determining the resistance capacity and rotational stiffness of beam-to-column connections while at the same time it also alleviates the inapplicability of four-node elements that have been proposed by several researchers for use in commonly available high-end structural engineering software products. In the process of formulating the analytical model, panel shear deformation of the joint has been taken care of by allowing the joint region of the column to undergo shear deformation. Numerical experience has been gained by processing several frame structural models. Application will be demonstrated using the general purpose finite element package ANSYS by way of applying to study a typical frame. Results have also been compared with those obtained by other researchers and a high-quality correlation between and among results have been obtained. In all cases, values obtained by the proposed two-node connection model have been acceptable for design purpose.