Zia Razzaq - Academia.edu (original) (raw)
Papers by Zia Razzaq
Engineering with Computers, 1988
Global Journal of Research In Engineering, 2017
This paper investigates various retrofitting schemes for a prestressed concrete box beam using ca... more This paper investigates various retrofitting schemes for a prestressed concrete box beam using carbon fiber reinforced polymer (CFRP) sheets with the goal of increasing flexural strength. A simply-supported box beam is studied with a constant uniformly distributed load and three gradually increasing concentrated loads proportional to HS20 truck loading of the Association of State Highway and Transportation Officials (AASHTO). Various retrofitting schemes are considered each with single, double, and triple CFRP sheets, respectively, installed in high compression and tension regions. Cross-sectional nonlinear moment-curvature relations are developed and coupled with a finite-difference solution algorithm to predict load-deflection relations for both retrofitted and non-retrofitted box beams. The study identifies effective CFRP retrofitting schemes that result in a significant increase in the flexural strength of the prestressed concrete box beam.
... edu Peyton B. Gregory NASA Langley Research Center, Hampton, Virginia 23681, USA Abstract Pre... more ... edu Peyton B. Gregory NASA Langley Research Center, Hampton, Virginia 23681, USA Abstract Presented herein is a theoretical study on the dynamic response of geometrically imperfect columns subjected to loads consisting of a dead ... Razzaq, Z., Voland, RT, Bush, HG, and ...
Structural Stability and Dynamics, 2002
... edu Peyton B. Gregory NASA Langley Research Center, Hampton, Virginia 23681, USA Abstract Pre... more ... edu Peyton B. Gregory NASA Langley Research Center, Hampton, Virginia 23681, USA Abstract Presented herein is a theoretical study on the dynamic response of geometrically imperfect columns subjected to loads consisting of a dead ... Razzaq, Z., Voland, RT, Bush, HG, and ...
Global Journal of Research In Engineering, 2017
Presented herein is the outcome of a study of prestressed concrete inverted tee beams with carbon... more Presented herein is the outcome of a study of prestressed concrete inverted tee beams with carbon fiber reinforced polymer (CFRP) sheets for possible use in building structures. To determine an effective approach for the use of CFRP, nine different retrofitting schemes are investigated for a prestressed beam under quasi-static distributed load to increase flexural strength. The theoretical analysis is based on coupling moment-curvature relations with a central finitedifference formulation. Three different thicknesses of CFRP sheets are studied in both tension and compression and effective retrofitting schemes are identified.
27th Structures, Structural Dynamics and Materials Conference, 1986
A concurrent processing algorithm is developed for materially nonlinear stability analysis of imp... more A concurrent processing algorithm is developed for materially nonlinear stability analysis of imperfect columns with biaxial partial rotational end restraints. The algorithm for solving the governing nonlinear ordinary differential equations is implemented on a multiprocessor computer called the 'Finite Element Machine', developed at the NASA Langley Research Center. Numerical results are obtained on up to nine concurrent processors. A substantial computational gain is achieved in using the parallel processing approach.
Performance of potential passive damping concepts is investigated for a long tubular aluminum all... more Performance of potential passive damping concepts is investigated for a long tubular aluminum alloy member and a two-bar grillage structure. The members are restrained partially at the ends and are of the type being considered for possible use in the construction of future outer space stations. Four different passive damping concepts are studied under free and forced vibration and include nylon brush, wool swab, copper brush and silly-putty-inchamber dampers installed inside the hollow space of the tubular member(s). It is found that the silly-putty-inchamber and the wool swab dampers provide effective
Engineering with Computers, 1987
A concurrent processing algorithm is developed for a materially nonlinear analysis of hollow squa... more A concurrent processing algorithm is developed for a materially nonlinear analysis of hollow square and rectangular structural sections and implemented on a special purpose multiprocessor computer at NASA Langley Research Center referred to as the Finite Element Machine (FEM). The cross-sectional thrust-moment-curvature relations are generated concurrently using a tangent stiffness approach, and yield surfaces are obtained that represent the interaction between axial load and biaxial moments. For the study, a maximum speed-up factor of 7.69 is achieved on eight processors. presented. Elasto-plastic biaxial thrust-momentcurvature relations and yield surfaces are developed by employing a tangent stiffness approach by means of an iterative algorithm implemented on the FEM. Computational efficiencies of the FEM are studied by analyzing each case of the problem by using one, two, four, and eight concurrent processors.
The main objectives of the study are: (1) identification of potential passive damping concepts fo... more The main objectives of the study are: (1) identification of potential passive damping concepts for slender tubular structural members with rotational and translational end springs under natural and forced-free vibrations; (2) evaluation of damping efficiencies of the various damping concepts; and (3) evaluation of the suitability of a theoretical finite difference analysis by comparison to the experimental results for the case of natural vibrations. Only member flexural an translation motion is considered. The natural vibration study is conducted on the seven damping concepts and for only one specific initial deflection. The most suitable of the seven dampers is further investigated under forced-free vibrations. In addition only one set of end springs is used for all of the experiments. The results show that passive damping provides a possible approach to structural vibration reduction.
Global Journal of Research In Engineering, 2017
Presented herein is the outcome of a study of prestressed concrete inverted tee beams with carbon... more Presented herein is the outcome of a study of prestressed concrete inverted tee beams with carbon fiber reinforced polymer (CFRP) sheets for possible use in building structures. To determine an effective approach for the use of CFRP, nine different retrofitting schemes are investigated for a prestressed beam under quasi-static distributed load to increase flexural strength. The theoretical analysis is based on coupling moment-curvature relations with a central finitedifference formulation. Three different thicknesses of CFRP sheets are studied in both tension and compression and effective retrofitting schemes are identified.
Engineering with Computers, 1987
A concurrent processing algorithm is developed for a materially nonlinear analysis of hollow squa... more A concurrent processing algorithm is developed for a materially nonlinear analysis of hollow square and rectangular structural sections and implemented on a special purpose multiprocessor computer at NASA Langley Research Center referred to as the Finite Element Machine (FEM). The cross-sectional thrust-moment-curvature relations are generated concurrently using a tangent stiffness approach, and yield surfaces are obtained that represent the interaction between axial load and biaxial moments. For the study, a maximum speed-up factor of 7.69 is achieved on eight processors.
Engineering with Computers, 1988
Global Journal of Research In Engineering, 2017
This paper investigates various retrofitting schemes for a prestressed concrete box beam using ca... more This paper investigates various retrofitting schemes for a prestressed concrete box beam using carbon fiber reinforced polymer (CFRP) sheets with the goal of increasing flexural strength. A simply-supported box beam is studied with a constant uniformly distributed load and three gradually increasing concentrated loads proportional to HS20 truck loading of the Association of State Highway and Transportation Officials (AASHTO). Various retrofitting schemes are considered each with single, double, and triple CFRP sheets, respectively, installed in high compression and tension regions. Cross-sectional nonlinear moment-curvature relations are developed and coupled with a finite-difference solution algorithm to predict load-deflection relations for both retrofitted and non-retrofitted box beams. The study identifies effective CFRP retrofitting schemes that result in a significant increase in the flexural strength of the prestressed concrete box beam.
... edu Peyton B. Gregory NASA Langley Research Center, Hampton, Virginia 23681, USA Abstract Pre... more ... edu Peyton B. Gregory NASA Langley Research Center, Hampton, Virginia 23681, USA Abstract Presented herein is a theoretical study on the dynamic response of geometrically imperfect columns subjected to loads consisting of a dead ... Razzaq, Z., Voland, RT, Bush, HG, and ...
Structural Stability and Dynamics, 2002
... edu Peyton B. Gregory NASA Langley Research Center, Hampton, Virginia 23681, USA Abstract Pre... more ... edu Peyton B. Gregory NASA Langley Research Center, Hampton, Virginia 23681, USA Abstract Presented herein is a theoretical study on the dynamic response of geometrically imperfect columns subjected to loads consisting of a dead ... Razzaq, Z., Voland, RT, Bush, HG, and ...
Global Journal of Research In Engineering, 2017
Presented herein is the outcome of a study of prestressed concrete inverted tee beams with carbon... more Presented herein is the outcome of a study of prestressed concrete inverted tee beams with carbon fiber reinforced polymer (CFRP) sheets for possible use in building structures. To determine an effective approach for the use of CFRP, nine different retrofitting schemes are investigated for a prestressed beam under quasi-static distributed load to increase flexural strength. The theoretical analysis is based on coupling moment-curvature relations with a central finitedifference formulation. Three different thicknesses of CFRP sheets are studied in both tension and compression and effective retrofitting schemes are identified.
27th Structures, Structural Dynamics and Materials Conference, 1986
A concurrent processing algorithm is developed for materially nonlinear stability analysis of imp... more A concurrent processing algorithm is developed for materially nonlinear stability analysis of imperfect columns with biaxial partial rotational end restraints. The algorithm for solving the governing nonlinear ordinary differential equations is implemented on a multiprocessor computer called the 'Finite Element Machine', developed at the NASA Langley Research Center. Numerical results are obtained on up to nine concurrent processors. A substantial computational gain is achieved in using the parallel processing approach.
Performance of potential passive damping concepts is investigated for a long tubular aluminum all... more Performance of potential passive damping concepts is investigated for a long tubular aluminum alloy member and a two-bar grillage structure. The members are restrained partially at the ends and are of the type being considered for possible use in the construction of future outer space stations. Four different passive damping concepts are studied under free and forced vibration and include nylon brush, wool swab, copper brush and silly-putty-inchamber dampers installed inside the hollow space of the tubular member(s). It is found that the silly-putty-inchamber and the wool swab dampers provide effective
Engineering with Computers, 1987
A concurrent processing algorithm is developed for a materially nonlinear analysis of hollow squa... more A concurrent processing algorithm is developed for a materially nonlinear analysis of hollow square and rectangular structural sections and implemented on a special purpose multiprocessor computer at NASA Langley Research Center referred to as the Finite Element Machine (FEM). The cross-sectional thrust-moment-curvature relations are generated concurrently using a tangent stiffness approach, and yield surfaces are obtained that represent the interaction between axial load and biaxial moments. For the study, a maximum speed-up factor of 7.69 is achieved on eight processors. presented. Elasto-plastic biaxial thrust-momentcurvature relations and yield surfaces are developed by employing a tangent stiffness approach by means of an iterative algorithm implemented on the FEM. Computational efficiencies of the FEM are studied by analyzing each case of the problem by using one, two, four, and eight concurrent processors.
The main objectives of the study are: (1) identification of potential passive damping concepts fo... more The main objectives of the study are: (1) identification of potential passive damping concepts for slender tubular structural members with rotational and translational end springs under natural and forced-free vibrations; (2) evaluation of damping efficiencies of the various damping concepts; and (3) evaluation of the suitability of a theoretical finite difference analysis by comparison to the experimental results for the case of natural vibrations. Only member flexural an translation motion is considered. The natural vibration study is conducted on the seven damping concepts and for only one specific initial deflection. The most suitable of the seven dampers is further investigated under forced-free vibrations. In addition only one set of end springs is used for all of the experiments. The results show that passive damping provides a possible approach to structural vibration reduction.
Global Journal of Research In Engineering, 2017
Presented herein is the outcome of a study of prestressed concrete inverted tee beams with carbon... more Presented herein is the outcome of a study of prestressed concrete inverted tee beams with carbon fiber reinforced polymer (CFRP) sheets for possible use in building structures. To determine an effective approach for the use of CFRP, nine different retrofitting schemes are investigated for a prestressed beam under quasi-static distributed load to increase flexural strength. The theoretical analysis is based on coupling moment-curvature relations with a central finitedifference formulation. Three different thicknesses of CFRP sheets are studied in both tension and compression and effective retrofitting schemes are identified.
Engineering with Computers, 1987
A concurrent processing algorithm is developed for a materially nonlinear analysis of hollow squa... more A concurrent processing algorithm is developed for a materially nonlinear analysis of hollow square and rectangular structural sections and implemented on a special purpose multiprocessor computer at NASA Langley Research Center referred to as the Finite Element Machine (FEM). The cross-sectional thrust-moment-curvature relations are generated concurrently using a tangent stiffness approach, and yield surfaces are obtained that represent the interaction between axial load and biaxial moments. For the study, a maximum speed-up factor of 7.69 is achieved on eight processors.