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    Smeared rotating crack model for reinforced concrete membrane elements

    , Article ACI Structural Journal ; Volume 107, Issue 4 , 2010 , Pages 411-418 ; 08893241 (ISSN) Broujerdian, V ; Kazemi, M. T ; Sharif University of Technology
    A set of stress-strain relations for normal-strength concrete and mild steel bars embedded in concrete is presented in this paper. The salient features of the proposed constitutive laws are: 1) considering the effect of reinforcement ratio on average stressstrain relationships of cracked concrete; and 2) considering the gradual reduction of average stiffness of steel bars embedded in concrete. Equilibrium, compatibility, and constitutive relationships were incorporated into an algorithm to obtain a procedure for analyzing reinforced concrete membrane elements. Corroboration with data from panel test specimens shows that the presented model provides good predictions for the entire... 

    Axial effects investigation in fixed-end circular bars under torsion with a finite deformation model based on logarithmic strain

    , Article International Journal of Mechanical Sciences ; Volume 48, Issue 1 , 2006 , Pages 75-84 ; 00207403 (ISSN) Yeganeh, M ; Naghdabadi, R ; Sharif University of Technology
    In this paper the torsion problem of a circular bar with fixed ends is solved using a finite deformation constitutive model based on the corotational rates of the logarithmic strain. The logarithmic, Green-Naghdi and Eulerian corotational rates of the logarithmic strain are used in the model. The solution is based on a von Mises type yield function that incorporates isotropic and kinematic hardenings. For the kinematic hardening, a modified Armstrong-Fredrick hardening model with the corotational rate of the logarithmic strain is used. Assuming incompressible behavior, the fixed-end torsion problem is simplified to the simple shear problem. Solving the problem, the stress components are... 

    Mechanical behaviour of A-III steel rebars under monotonic loadings at seismic strain rates

    , Article Magazine of Concrete Research ; Volume 70, Issue 1 , 2018 , Pages 42-54 ; 00249831 (ISSN) Khonsari, S. V ; Shabani, A ; England, G. L ; Shahsavar Gargari, M ; Sharif University of Technology
    ICE Publishing  2018
    As the reinforcing bars used in concrete structures located in earthquake-prone areas experience strain rates higher than normal quasi-static ones, it is necessary to have a comprehensive understanding of the behaviour of such materials under these rates of loading. In this work, in order to study the behaviour of grade A-III reinforcing-bar steel (based on the GOST standard, a set of technical standards maintained by the Euro-Asian Council for Standardization, Metrology and Certification), a number of monotonic tests on its tensile and compressive strength on (short and long) specimens at various strain rates, 0·002, 0·01, 0·02 and 0·04 s-1, experienced during earthquakes, were carried out.... 

    Seismic behavior of concrete moment frame reinforced with GFRP bars

    , Article Composites Part B: Engineering ; Volume 163 , 2019 , Pages 324-338 ; 13598368 (ISSN) Aliasghar Mamaghani, M ; Khaloo, A ; Sharif University of Technology
    Elsevier Ltd  2019
    In this research, four types of concrete moment frame were designed with glass fiber reinforced polymer (GFRP) bars according to ACI 440.1R-15 and the seismic behavior was assessed using pushover analysis. The frames were three and five stories with two and three bays. A computer code was developed to calculate the amount of fiber reinforced polymer bars in beams of the frames. In order to evaluate nonlinear behavior in plastic hinge regions, sections of beams and columns were analyzed on the basis of moment-curvature diagram and also P-M interaction curve for columns. Performance levels of frames were determined considering ATC-40 criteria. Behavior of concrete moment frames reinforced with... 

    Rigid-bar loading on pregnant uterus and development of pregnant abdominal response corridor based on finite element biomechanical model

    , Article International Journal for Numerical Methods in Biomedical Engineering ; Volume 36, Issue 1 , January , 2020 Irannejad Parizi, M ; Ahmadian, M. T ; Mohammadi, H ; Sharif University of Technology
    Wiley-Blackwell  2020
    During pregnancy, traumas can threaten maternal and fetal health. Various trauma effects on a pregnant uterus are little investigated. In the present study, a finite element model of a uterus along with a fetus, placenta, amniotic fluid, and two most effective ligament sets is developed. This model allows numerical evaluation of various loading on a pregnant uterus. The model geometry is developed based on CT-scan data and validated using anthropometric data. Applying Ogden hyper-elastic theory, material properties of uterine wall and placenta are developed. After simulating the “rigid-bar” abdominal loading, the impact force and abdominal penetration are investigated. Findings are compared... 

    Microstructural study of a High Bainite Dual Phase (HBDP) steel austempered at different temperatures

    , Article Defect and Diffusion Forum ; Volume 297-301 , 2010 , Pages 62-67 ; 10120386 (ISSN); 3908451809 (ISBN); 9783908451808 (ISBN) Bakhtiari, R ; Ekrami, A ; Sharif University of Technology
    Trans Tech Publications Ltd  2010
    4340 steel bars were austenitized at 850°C for 1 hour followed by heating at 700°C (ferrite and austenite region) for 90 min and quenching into a salt bath with different temperatures of 300, 350, 400 and 450°C. The steel bars were held for 1 hour at these temperatures before air cooling to room temperature. Various ferrite-bainite microstructures with 34% volume fraction of ferrite and different bainite morphologies were obtained. The results of SEM studies showed that by increasing the austempering temperature, the morphology of bainite varies from lower to upper bainite. According to the T-T-T diagram of the studied steel, the bainite transformation will not complete for the holding time...