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Total 154 records

    Design method and feasibility study of fully actively controlled frames

    , Article Scientia Iranica ; Volume 11, Issue 1-2 , 2004 , Pages 50-59 ; 10263098 (ISSN) Joghataie, A ; Asbmarz, M. M ; Sharif University of Technology
    Sharif University of Technology  2004
    Abstract
    In this paper, results of a preliminary study on the feasibility of using an Active Tendon Control (ATC) mechanism for frame structures subject to earthquakes is presented. So far, the ATC mechanism has mainly been considered as a means for installation on structures to mitigate their response under severe loading. In this study, it is desired to evaluate the possibility of using the ATC mechanism to serve as the main means for the stability of frames against earthquakes. Hence, a methodology is presented for the integrated design of frames with ATC mechanisms, which is tested numerically. A number of five-, ten-, fifteen- and twenty-story steel frames are used for this purpose. To this end,... 

    Dynamic forces at square and inclined rail joints: Field experiments

    , Article Journal of Transportation Engineering ; Volume 142, Issue 9 , 2016 ; 0733947X (ISSN) Ataei, S ; Mohammadzadeh, S ; Miri, A ; Sharif University of Technology
    American Society of Civil Engineers (ASCE)  2016
    Abstract
    Insulated rail joints (IRJs) are widely used in signaling and broken rail identification systems. Track deterioration adjacent to IRJ is frequent due to excessive dynamic forces generated at IRJs by the repetitive passage of the ongoing traffic. Hence, they exhibit low service life and are considered high-risk elements and maintained through high standards. With a view to increase operational speed and the annual operational throughput, many improved structural designs have been proposed, of which inclined IRJs are the focus of this paper. To compare noise, vibration, and adjacent sleepers' vertical displacement of square and 30° and 45° cut joints, a series of field tests have been carried... 

    VM link element for consideration of shear-flexural interaction

    , Article 10th East Asia-Pacific Conference on Structural Engineering and Construction, EASEC 2010, Bangkok, 3 August 2006 through 5 August 2006 ; Volume 2 , 2006 , Pages 149-154 Erfani, S ; Kazemi, M. T ; Sharif University of Technology
    2006
    Abstract
    A mixed shear-flexural beam element, which is called VM link element, is introduced. Dissimilar multi-surfaces in the shear-flexural space and non zero off diagonal components in flexibility matrixes are used for more realistic modeling of inelastic shear-flexural interaction. For preventing of intersecting among the yield surfaces, a new non-associated flow rule and a new kinematic hardening rule are developed. Capability of this element is examined for shear links used in eccentrically braced frames analysis for cyclic loading. It is shown that, the proposed link element is in a good agreement with the existing test results  

    Sensitivity analysis of simple methods in determination of offshore jacket structures levels stiffness

    , Article Journal of Marine Science and Technology (Japan) ; 2021 ; 09484280 (ISSN) Tabeshpour, M. R ; Ahmadi, A ; Sharif University of Technology
    Springer Japan  2021
    Abstract
    Dynamic analyses are necessary problems in offshore jacket structures design and assessment. These analyses have various applications in recognition of dynamic behavior, fatigue analysis, damage detection, etc. Natural frequencies and mode shapes, as inherent vibrational features of a structure, are key parameters in referred analyses. These parameters are mainly affected by mass and stiffness matrices and slightly by damping. Therefore, it is more important to estimate the stiffness matrix of a structure accurately, especially in stiff structures such as offshore jacket platforms. In many cases, the stiffness of levels is required. For example, it can be useful in the construction of an... 

    Sensitivity analysis of simple methods in determination of offshore jacket structures levels stiffness

    , Article Journal of Marine Science and Technology (Japan) ; Volume 27, Issue 1 , 2022 , Pages 619-636 ; 09484280 (ISSN) Tabeshpour, M.R ; Ahmadi, A ; Sharif University of Technology
    Springer Japan  2022
    Abstract
    Dynamic analyses are necessary problems in offshore jacket structures design and assessment. These analyses have various applications in recognition of dynamic behavior, fatigue analysis, damage detection, etc. Natural frequencies and mode shapes, as inherent vibrational features of a structure, are key parameters in referred analyses. These parameters are mainly affected by mass and stiffness matrices and slightly by damping. Therefore, it is more important to estimate the stiffness matrix of a structure accurately, especially in stiff structures such as offshore jacket platforms. In many cases, the stiffness of levels is required. For example, it can be useful in the construction of an... 

    Axiomatic Design Science: Application in reducing Design Complexities of Special Structures

    , Ph.D. Dissertation Sharif University of Technology Fazli, Noroddin (Author) ; Abedian, Ali (Supervisor) ; Malaek, Mohammad Bagher (Supervisor)
    Abstract
    This research aims to study fundamentals of design as a science for possible use in special structures. Special structures are referred to those structures that designers’ knowledge for which are insufficient. Designs of such structures are complex in the sense that we lack all necessary elements of design matrix; as well as proper steps to reach the unknowns. Introducing appropriate design strategy for such structures; we show how a design could be developed without specific needs for trial and errors. In this work, various design methodologies and especially “Axiomatic Design” have been examined. In addition, functional requirement and associated design parameters for structural design are... 

    New method in characterizing tensile softenig procedure in concrete

    , Article ISEC 2011 - 6th International Structural Engineering and Construction Conference: Modern Methods and Advances in Structural Engineering and Construction, 21 June 2011 through 26 June 2011 ; June , 2011 , Pages 1145-1150 ; 9789810879204 (ISBN) Khezrzadeh, H ; Mofid, M ; Yazdani S ; Cheung S. O ; Singh A ; Ghafoori N ; American Society of Civil Engineers (ASCE); Architectural Institute of Japan (AIJ); Chartered Institute of Building (CIOB); et al.; University of Nevada Las Vegas (UNLV), College of Engineering; Wayne State College of Engineering ; Sharif University of Technology
    Research Publishing Services  2011
    Abstract
    Several investigators worked on various aspects of tensile behavior of concrete because of its wide usage in structural design. One of the observable phenomena during tensile failure of concrete is strain softening, i.e. a negative slope in the stress-deformation diagrams. There are many kinds of experiment-based softening curves for concrete. In current research, use of newly introduced concept of fractal geometry and a failure model yields to a new softening curve for concrete. This new curve is denominated "Quasi-fractal" softening curve, which is a theorybased softening model. Comparison of Quasi-fractal softening curve with a set of proposed experimental softening curves has been... 

    An ACS algorithm for the formation of subminimal-suboptimal cycle bases

    , Article Advances and Trends in Structural Engineering, Mechanics and Computation - Proceedings of the 4th International Conference on Structural Engineering, Mechanics and Computation, SEMC 2010, 6 September 2010 through 8 September 2010 ; 2010 , Pages 437-440 ; 9780415584722 (ISBN) Kaveh, A ; Jahanshahi, M ; Zingoni A ; Sharif University of Technology
    Abstract
    Cycle bases have many applications in science and engineering. In this paper, an ant colony system algorithm is developed to generate a cycle basis that is simultaneously subminimal and suboptimal. Such a basis is called a subminimal-suboptimal cycle basis. Examples are included to illustrate the efficiency of ACS algorithm  

    Response spectrum method for extreme wave loading with higher order components of drag force

    , Article Journal of Marine Science and Application ; Volume 16, Issue 1 , 2017 , Pages 27-32 ; 16719433 (ISSN) Tabeshpour, M. R ; Dezfouli, Mani, F ; Dastan Diznab, M. A ; Mohajernasab, S ; Seif, S. M ; Sharif University of Technology
    Abstract
    Response spectra of fixed offshore structures impacted by extreme waves are investigated based on the higher order components of the nonlinear drag force. In this way, steel jacket platforms are simplified as a mass attached to a light cantilever cylinder and their corresponding deformation response spectra are estimated by utilizing a generalized single degree of freedom system. Based on the wave data recorded in the Persian Gulf region, extreme wave loading conditions corresponding to different return periods are exerted on the offshore structures. Accordingly, the effect of the higher order components of the drag force is considered and compared to the linearized state for different sea... 

    Push-out tests on polypropylene concrete

    , Article 11th East Asia-Pacific Conference on Structural Engineering and Construction, EASEC-11, Taipei, 19 November 2008 through 21 November 2008 ; 2008 Maleki, S ; Mahoutian, M ; Sharif University of Technology
    2008
    Abstract
    The results of several monotonioc push-out tests on polypropylene concrete with channel shear connectors are presented in this research. The results are compared with ordinary concrete specimens with the same test setup. The effect of confining reinforcement on the shear capacity and ductility of polypropylene concrete composite system is investigated  

    Factors influencing construction productivity

    , Article 10th East Asia-Pacific Conference on Structural Engineering and Construction, EASEC 2010, Bangkok, 3 August 2006 through 5 August 2006 ; Volume 5 , 2006 , Pages 269-274 ; 9748257207 (ISBN); 9789748257204 (ISBN) Khoramshahi, F ; Dehghan, R ; Mortaheb, M. M ; Sharif University of Technology
    School of Engineering and Technology  2006
    Abstract
    In today competitive world, productivity or lack of it is a major challenge facing the construction industry. The term "productivity" is defined as the amount of output per unit of input. In order to boost productivity in the construction industry, influencing factors should be recognized and improved. Researchers have identified a myriad of factors affecting construction productivity that can be broadly classified as "external" and "internal" factors. In this paper it has been tried to identify and categorize different factors influencing construction productivity. As a result the intended audience is practitioners in the construction industry and project managers who are eager to improve... 

    On the modal incremental dynamic analysis

    , Article Structural Design of Tall and Special Buildings ; Volume 14, Issue 4 , 2005 , Pages 315-329 ; 15417794 (ISSN) Mofid, M ; Zarfam, P ; Fard, B. R ; Sharif University of Technology
    2005
    Abstract
    In this article a new technique for the dynamic response of structures is investigated. This applied procedure can predict the approximate seismic performance of the structures and it is fast, inexpensive and results are reasonably acceptable. In fact, this novel method logically combines two different techniques, 'incremental dynamic analysis (IDA)' and 'modal pushover analysis (MPA)', presented by other researchers. This method will take advantage of both methodical ideas such as equivalent single degree of freedom of multi-degree structures and the implementation of different scaled level of an earthquake record to the provided equivalent SDF structure. Using this procedure, simple... 

    Design of a Barge Equipped with Turbojet for oil well Fire Extinguishing

    , M.Sc. Thesis Sharif University of Technology Heidari Aliabadi , Mojtaba (Author) ; Abbaspour Tehrani fard, Majid (Supervisor) ; Mehdigholi, Hamid (Supervisor)
    Abstract
    In this thesis, the use of jet-engine for oil well fire fighting which is a latest in kind is described and analyzed. For this purpose, more familiarization with this system and some knowledge’s such as hydrodynamics characteristic of nominated area, traditional ways of fire fighting in region, different types of jet engines available type of offshore vessels, type of flame and their characteristic are required, which after studying and analyzing above fields in details, the use of turbojet motors and barge has been chosen for the case to obtain optimum specification os this turbojet motors and required dimensions of barge Some information about oil well shuch as, fluid output, speed rate... 

    Structural Design of a Launch Vehicle with Reusable First Stage

    , M.Sc. Thesis Sharif University of Technology Hassan Jamaklu (Author) ; Haddadpour, Hassan (Supervisor)
    Abstract
    Aerodynamics loads and aeroheating during reentry, are one of the challenging issues in designing One of the main challenges in the design and application of reusable spacecrafts is the aerodynamic and thermal loads acting on their structures during reentry into the atmosphere. For this reason, all the concepts/prototypes presented in the 20th century were either not fully reusable, or were partially canceled, or did not have economic justification. In this report, the aerodynamic loads on the first stage of a launch vehicle during the launch and return phases have been investigated. Due to the fact that the main part of the first stage of the vehicle includes fuel and oxidizer tanks, the... 

    Numerical properties of second order integration algorithms for plasticity models

    , Article Research and Applications in Structural Engineering, Mechanics and Computation - Proceedings of the 5th International Conference on Structural Engineering, Mechanics and Computation, SEMC 2013 ; 2013 , Pages 443-448 ; 9781138000612 (ISBN) Jahanshahi, M ; Sharif University of Technology
    2013
    Abstract
    Investigating the behavior of materials in plastic limit is very important in different fields of engineering. Due to the simplicity of implementation and numerical stability, implicit types of algorithms are conventionally used to deal with plasticity problems. The backward Euler method as a first order accurate algorithm has proven very efficient for integrating the rate form of differential equations governing the behavior of different plasticity models. However, it is desirable to have algorithms with superior performance and quadratic rate of convergence compared with backward Euler method. Many second order integration algorithms have been proposed in the literature which are majorly... 

    Application of endurance time method in nonlinear seismic analysis of steel frames

    , Article Procedia Engineering ; Volume 14 , 2011 , Pages 3237-3244 ; 18777058 (ISSN) Riahi, H. T ; Estekanchi, H. E ; Seyedain Boroujeni, S ; Sharif University of Technology
    2011
    Abstract
    In Endurance Time (ET) method gradually intensifying acceleration functions are created in a manner that the linear and nonlinear response spectra of them, while being proportional to average of real earthquakes spectra, intensifies in a uniform manner with time. These functions are used as input functions for nonlinear time history analysis of structures and performance of structures is assessed based on the maximum time duration that they can meet the specified performance objectives. In this paper, application of the ET method in nonlinear seismic analysis of structures has been investigated. Numerical procedures and optimization techniques that are used for the production of acceleration... 

    Seismic performance evaluation and design of steel structures equipped with dual-pipe dampers

    , Article Journal of Constructional Steel Research ; Volume 122 , 2016 , Pages 25-39 ; 0143974X (ISSN) Mahjoubi, S ; Maleki, S ; Sharif University of Technology
    Elsevier Ltd 
    Abstract
    Dual-pipe damper (DPD) is a metallic yielding device for passive control of structures, introduced recently by the authors. The objective of the current study is to provide guidelines for implementing DPDs in actual steel buildings, evaluate and compare their performance against other metallic dampers. In this study, a representative load-displacement model for DPDs is proposed for the first time, and assessed based on previous experimental cyclic tests. Guidelines for the design of DPD devices are also presented. Three steel moment resisting frames of 5, 10 and 20 stories are designed and then equipped with DPDs of various properties. The responses of the frames to seven earthquake... 

    Optimal design of multiphase composites under elastodynamic loading

    , Article Computer Methods in Applied Mechanics and Engineering ; Volume 300 , 2016 , Pages 265-293 ; 00457825 (ISSN) Tavakoli, R ; Sharif University of Technology
    Elsevier  2016
    Abstract
    An algorithm is proposed to optimize the performance of multiphase structures (composites) under elastodynamic loading conditions. The goal is to determine the distribution of material in the structure such that the time-averaged total stored energy of structure is minimized. A penalization strategy is suggested to avoid the checkerboard instability, simultaneously to generate near 0-1 topologies. As a result of this strategy, the solutions of presented algorithm are sufficiently smooth and possess the regularity of H1 function space. A simple method for the continuum adjoint sensitivity analysis of the corresponding PDE-constrained optimization problem is presented. It is general and can be... 

    Dynamic-based pushover analysis for one-way plan-asymmetric buildings

    , Article Engineering Structures ; Volume 163 , 2018 , Pages 332-346 ; 01410296 (ISSN) Rahimzadeh Rofooei, F ; Mirjalili, M. R ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    A simple Dynamic-based Pushover analysis for Plan Asymmetric buildings (DPPA) is proposed with the aim of properly considering the effects of torsional behavior as well as the higher modes in the applied lateral load pattern. According to the proposed method, the peak story drifts obtained from the response spectrum analysis (RSA) can be resolved into their translational and rotational components, and the related equivalent static lateral forces and torsional moments can be calculated. Consequently, for accurate estimation of the maximum drift demands of plan-asymmetric buildings, it is proposed that the drift responses obtained from the RSA for the stiff and flexible edges of the building... 

    Buckling and frequency responses of a graphene nanoplatelet reinforced composite microdisk

    , Article International Journal of Applied Mechanics ; Volume 11, Issue 10 , 2019 ; 17588251 (ISSN) Moayedi, H ; Habibi, M ; Safarpour, H ; Safarpour, M ; Foong, L. K ; Sharif University of Technology
    World Scientific Publishing Co. Pte Ltd  2019
    Abstract
    This is the first research on the vibration and buckling analysis of a graphene nanoplatelet composite (GPLRC) microdisk in the framework of a numerical based generalized differential quadrature method (GDQM). The stresses and strains are obtained using the higher-order shear deformable theory (HOSDT). Rule of the mixture is employed to obtain varying mass density, thermal expansion, and Poisson's ratio, while the module of elasticity is computed by modified Halpin-Tsai model. Governing equations and boundary conditions of the GPLRC microdisk are obtained by implementing Extended Hamilton's principle. The results show that outer to inner ratios of the radius (Ro/Ri), ratios of length scale...