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    Obtaining optimal performance with ring stiffeners on strength for submarine pipeline

    , Article World Applied Sciences Journal ; Volume 15, Issue 11 , 2011 , Pages 1494-1502 ; 18184952 (ISSN) Riahi, F ; Shamsai, A ; Rahmani, K ; Showkati, H ; Sharif University of Technology
    Abstract
    Submarine pipelines as the principal structural components are prone to fail by circumferential buckling under the effect of hydrostatic external pressure. Basically, the buckling capacity of a thin-walled pipe is dependent on "radius to thickness" ratio. At least two modes of local and overall buckling are possible in any pipeline system, which could be developed in pipe wall. A method of strengthening of pipes is developed in this paper to stop the failure. A total of 21 stiffened models are generated and analyzed using the well-known finite element program ABAQUS. In this study, the buckling and post-buckling behaviour of stiffened pipes are investigated by carrying out linear and... 

    Structural similitude in free vibration of orthogonally stiffened cylindrical shells

    , Article Thin-Walled Structures ; Volume 47, Issue 11 , 2009 , Pages 1316-1330 ; 02638231 (ISSN) Torkamani, Sh ; Navazi, H. M ; Jafari, A. A ; Bagheri, M ; Sharif University of Technology
    2009
    Abstract
    In this paper, the necessary similarity conditions, or scaling laws, for free vibrations of orthogonally stiffened cylindrical shells are developed using the similitude theory. The Donnell-type nonlinear strain-displacement relations along with the smearing theory are used to model the structure. Then the principle of virtual work is used to analyze the free vibration of the stiffened shell. After non-dimensionalizing the derived formulations, the scaling laws are developed, using the similitude theory. Then, different examples are solved to validate the scaling laws numerically and experimentally. The obtained results show the effectiveness of the derived formulations. © 2009 Elsevier Ltd.... 

    Analysis and design recommendations for diagonally stiffened steel plate shear walls

    , Article Thin-Walled Structures ; Volume 103 , 2016 , Pages 72-80 ; 02638231 (ISSN) Akhavan Sigariyazd, M. H ; Joghataie, A ; K. A. Attari, N ; Sharif University of Technology
    Elsevier Ltd 
    Abstract
    This paper presents a comparison of analytical and experimental results of an investigation on the diagonally stiffened steel plate shear walls (SPWs). Experimental studies were carried out on three 1/3-scaled, one story single bay shear walls. The first specimen was a control specimen which was unstiffened and the other two specimens were diagonally stiffened using different stiffener configurations. Finite-element models of full SPWs are developed using finite element model. The results are compared with experimental results to investigate the influence of stiffeners on the behavior of the specimens. Good agreement between analytical and experimental models is found in point of failure... 

    Influence of crack on the steel plate shear walls strengthened by diagonal stiffeners

    , Article Structural Design of Tall and Special Buildings ; Volume 29, Issue 6 , 06 February , 2020 Khaloo, A ; Foroutani, M ; Ghamari, A ; Sharif University of Technology
    John Wiley and Sons Ltd  2020
    Abstract
    In spite of existing comprehensive studies on the behavior of steel plate shear wall (SPSW), some aspects of the SPSW have remained unknown, yet. One of the important aspects that is unknown is the crack effect on the SPSW behavior in linear and nonlinear zones. Some experimental studies have been reported that SPSWs were fractured due to crack propagation. Therefore, the crack effect on the behavior of SPSW should be accounted in considering of SPSW behavior. Although the effect of crack on the thin SPSW has been investigated to a limited extent numerically, stiffened SPSPW, especially diagonally stiffened SPSW, has not been studied. In doing so, in this paper, the effect of crack effect on... 

    On the design of stiffened steel plate shear wall with diagonal stiffeners considering the crack effect

    , Article Structures ; Volume 31 , 2021 , Pages 828-841 ; 23520124 (ISSN) Khaloo, A ; Ghamari, A ; Foroutani, M ; Sharif University of Technology
    Elsevier Ltd  2021
    Abstract
    Steel Plate Shear Walls (SPSWs) have high stiffness, strength, and considerable energy absorption capability, which have persuaded engineers to utilize the system in their practical projects. Some significant characteristic SPSWs have remained unknown despite worthwhile experimental and numerical studies. One of these unknown aspects is the effect of cracks on SPSWs behavior. Various experimental studies have reported the fracture of SPSWs during testing due to crack growth, but none of the experimental tests have studied the crack effect. In this respect, the behavior of SPSWs strengthened with diagonal stiffeners is studied in this paper. To study this, cracks located at the intersection... 

    An Analitical Model for Grid Stiffened Structures of Various Patterns

    , M.Sc. Thesis Sharif University of Technology Zarei, Mohsen (Author) ; Kouchakzadeh, Mohammad Ali (Supervisor)
    Abstract
    Structural efficiency is a primary concern in today’s aerospace and aircraft industries. This brings about the need for strong and light weight structures. To increase the strength of a panel without considerable increase in its weight, we may use a lattice of stiffeners which may have shells connected to one side of the lattice or both sides of it. These structures are usually called grid stiffened structures. Aircraft fuselage and launch vehicle fuel tanks are some of the many applications of these structures in aerospace and aircraft industries. These structures include two major groups; isogrids (grid stiffened structures with equivalent isotropic properties) and orthogrids (grid... 

    Scaled down models for free vibration analysis of orthogonally stiffened cylindrical shells using similitude theory

    , Article 26th Congress of International Council of the Aeronautical Sciences 2008, ICAS 2008, Anchorage, AK, 14 September 2008 through 19 September 2008 ; Volume 2 , 2008 , Pages 3458-3469 ; 9781605607153 (ISBN) Torkamani, S ; Jafari, A. A ; Navazi, H. M ; Sharif University of Technology
    2008
    Abstract
    In this paper, the necessary similarity conditions, or scaling laws, for free vibrations of orthogonally stiffened cylindrical shells are developed using similitude theory. The Donnelltype nonlinear strain-displacement relations along with smearing theory are used to model the structure. Then the principle of virtual work is used to analyze the free vibration of the stiffened shell. After nondimensionalizing the derived formulations, the scaling laws are developed, using similitude theory. Then, different examples are solved to validate the scaling laws numerically and experimentally. The obtained results show the effectiveness of the derived formulations  

    On the Parametric Analysis of Structural Response of Base Plate Connections through FEM

    , M.Sc. Thesis Sharif University of Technology Khodaei, Sina (Author) ; Mofid, Masoud (Supervisor)
    Abstract
    Base plate is one of the important and sensitive elements of a structure which roles as a connector of force and moment in column to foundation joint and prevents from stress concentration in the joint area. As until now there has been several numerical and experimental researches conducted about base plate connections, but in practice for design, base plate is considered as a cantilever beam which undertakes compressive force and bending moment. In this method of design many important factors such as separation and deflection of base plate, interaction of base plate with bolts and foundation aren’t taken into consideration. Therefore there is an urgent need to design base plates considering... 

    Buckling and postbuckling of advanced grid stiffened truncated conical shells with laminated composite skins

    , Article Thin-Walled Structures ; Volume 149 , 2020 Bohlooly, M ; Kouchakzadeh, M. A ; Mirzavand, B ; Noghabi, M ; Sharif University of Technology
    Elsevier Ltd  2020
    Abstract
    A theoretical approach is presented to derive an explicit formula for buckling load and postbuckling path of advanced grid stiffened conical shells (stiffeners with laminated composite skins). Different types of fiber paths of grids including stringer, ring, and helical are considered. The simply supported truncated conical shell with imperfection is subjected to axial compression. Basic formulations are constructed using the classical theory of shells and von Karman type of nonlinear strain-displacement relationships. The equilibrium and compatibility equations are solved by Galerkin procedure, and an explicit relation is obtained to predict the equilibrium paths. Results for different... 

    Analysis and Modeling of Base Plates Under the Effect of Different Loads

    , M.Sc. Thesis Sharif University of Technology Abbaspour, Hamid (Author) ; Mofid, Masoud (Supervisor)
    Abstract
    In steel structured buildings the connection of columns to foundations is of practical significance. This connection customarily is performed by a base plate, which is connected to the foundation with bolts. The columns and base plates are usually prepared separately, and later are welded together by contractors. Due to the errors in the process of fabrication, these plates are proposed with larger dimensions than those suggested by the designers. However, it is believed that the utilization of stiffeners, which are welded to the columns in a perpendicular state, reduces the stress field inside the base plates significantly. Therefore, by use of stiffeners the thickness of base plates can be... 

    Investigating of the Behavior of the Column Base Plate with Eccentirisity Using FEM

    , M.Sc. Thesis Sharif University of Technology Moeini, Amin (Author) ; Vafaei, Abolhassan (Supervisor) ; Mofid, massoud (Co-Advisor)
    Abstract
    Base plate is one of the crucial elements in steel structures which transfer force from column to foundation and also prevent stress concentration in jointing area between them. For investigating the behavior of base plate under different caseloads such as axial, transverse and earthquake loads, it is necessary to consider all the involved elements including column, base plate, foundation, anchor rods and also interaction between these elements. In this study the connection between column and base plate, base plate and foundation are analyzed thoroughly. The behavior of base plate with a box type column with and without stiffener under the static loads is analyzed using finite element... 

    Free Vibration Analysis of Circumferentially Stiffened Micro-Cylinder Made of the Functionally Graded Material

    , M.Sc. Thesis Sharif University of Technology Jabbarian, Siavash (Author) ; Ahmadian, Mohammad Taghi (Supervisor) ; Firouzbakhsh, Kekhosro (Co-Advisor)
    Abstract
    Micro-Structures, especially cylindrical shells, has been widely used in different high tech industries, that this extreme usage emphasis, analyze of the vibration behavior of these structures. For gain an appropriate characteristics for a known purpose we can stiffen cylindrical shells with some rings that lids to improvement in mechanical properties of them. With advent of new materials, such as Functionally Graded Materials (FGM) and unique properties of these materials investigation of vibration behavior and characteristics of micro cylinders which has been made of FGM can be very important and essential. By using FGM materials many mechanical characteristics of these structures can be... 

    Analysis of Slabs Stiffened by Cables and Pedestals

    , M.Sc. Thesis Sharif University of Technology Mokhberi, Arsalan (Author) ; Eskandari, Morteza (Supervisor)
    Abstract
    In this study, a new concrete slab stiffened by concrete pedestals and steel cables is introduced. The slab system is studied by employing both analytical and numerical methods. The steel cables are connected to the edges of slab and the concrete pedestals mounted at the bottom face of slab act as the middle supports of cables. The tension force in the cable and its inclination results in upward forces acting at the bottom face of slab. With the aims of classical theory of thin plates and the superposition technique, the problem of a simply supported rectangular slab stiffened by cables is studied analytically. The obtained results are verified by a numerical modelling implemented in SAP2000... 

    Axisymmetric Response of a Transversely Isotropic Half-space Stiffened by a Thin Plate Considering Refined Interaction Theory

    , M.Sc. Thesis Sharif University of Technology Shanesaz Zadeh, Pouya (Author) ; Eskandari, Morteza (Supervisor)
    Abstract
    In this paper, the elastic response of a surface-stiffened transversely isotropic half-space subjected to a surface normal load is addressed. The half-space is reinforced by a Kirchhoff thin plate bonded to its surface. Two different boundary conditions are considered across the plate-half-space interface: (i) the classic approach in which the plate in-plane deformation is neglected by writing the interfacial boundary conditions across the plate mid-plane, and (ii) the refined approach that considers the in-plane deformation of plate due to bending by writing the boundary conditions across the bottom face of plate. By virtue of appropriate displacement potentials, the complete set of elastic... 

    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
    2010
    Abstract
    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... 

    Multidisciplinary optimization of a stiffened shell by genetic algorithm

    , Article Journal of Mechanical Science and Technology ; Volume 26, Issue 2 , February , 2012 , Pages 517-530 ; 1738494X (ISSN) Mehrabani, M. M ; Jafari, A. A ; Azadi, M ; Sharif University of Technology
    2012
    Abstract
    Vibration analysis of simply supported rotating cross-ply laminated stiffened cylindrical shell is performed using an energy approach which includes variational and averaging method. The stiffeners include rings and stringers. The equations are obtained by Rayleigh-Ritz method and Sander's relations. To validate the present method, the results are compared to the results available in other literatures. A good adoption is observed in different type of results including isotropic shells, rotating laminated shells, stiffened isotropic shells and stiffened laminated shells. Then, the optimization of parameters due to shell and stiffeners is conducted by genetic algorithm (GA) method under weight... 

    Free vibration analysis of functionally graded cylindrical shells stiffened by uniformly and non-uniformly distributed ring stiffeners

    , Article ASME International Mechanical Engineering Congress and Exposition, Proceedings, 13 November 2009 through 19 November 2009 ; Volume 15 , 2010 , Pages 367-375 ; 9780791843888 (ISBN) Moeini, S. A ; Rahaei Fard, M ; Ahmadian, M. T ; Movahhedy, M. R ; Sharif University of Technology
    American Society of Mechanical Engineers (ASME) 
    Abstract
    Free vibration analysis of a transversely stiffened circular thin hollow cylinder made of functionally graded materials (FGMs) is analytically evaluated. Functionally graded materials are inhomogeneous composites which are usually made from a mixture of metal and ceramic. The gradient compositional variation of the constituents from one surface to the other provides an elegant solution to the problem of high transverse shear stresses induced when two dissimilar materials with large differences in material properties are bonded. In this paper, application of an FGM made of two different materials is investigated by applying Ritz method. While cylinder is assumed to be thin, strain energy... 

    Structural analysis of stiffened FGM thick walled cylinders by application of a new cylindrical super element

    , Article World Academy of Science, Engineering and Technology ; Volume 58 , 2009 , Pages 116-121 ; 2010376X (ISSN) Moeini, A ; Ahmadian, M. T ; Sharif University of Technology
    2009
    Abstract
    Structural behavior of ring stiffened thick walled cylinders made of functionally graded materials (FGMs) is investigated in this paper. Functionally graded materials are inhomogeneous composites which are usually made from a mixture of metal and ceramic. The gradient compositional variation of the constituents from one surface to the other provides an elegant solution to the problem of high transverse shear stresses that are induced when two dissimilar materials with large differences in material properties are bonded. FGM formation of the cylinder is modeled by power-law exponent and the variation of characteristics is supposed to be in radial direction. A finite element formulation is... 

    Influence of diagonal stiffeners on the response of steel plate shear walls (SPSWs) considering crack propagation

    , Article Bulletin of Earthquake Engineering ; Volume 17, Issue 9 , 2019 , Pages 5291-5312 ; 1570761X (ISSN) Khaloo, A ; Foroutani, M ; Ghamari, A ; Sharif University of Technology
    Springer Netherlands  2019
    Abstract
    Steel plate shear walls (SPSWs) have shown a desirable performance in experimental studies and past earthquakes. The advantages of the SPSW and its good performance against lateral loads persuade designers to utilize the system in their practical projects. Some important aspects of the SPSW have remained unknown in spite of valuable experimental and numerical studies. One of these unknown characteristics is the effect of cracks on the SPSW behavior. Several experimental studies have reported fracture in SPSW due to crack propagation during testing, but the experimental studies have not investigated the crack effect. Due to low thickness of steel plate and inherence of crack, the crack... 

    Dynamic instability characteristics of advanced grid stiffened conical shell with laminated composite skins

    , Article Journal of Sound and Vibration ; Volume 488 , 2020 Bohlooly, M ; Kouchakzadeh, M. A ; Mirzavand, B ; Noghabi, M ; Sharif University of Technology
    Academic Press  2020
    Abstract
    Dynamical instability characteristics of sandwich truncated conical shell are investigated. The three-layered shell is composed of advanced grid stiffened core and laminated composite skins. The core maybe made of three different fiber paths. The conical shell with simply-supported ends is subjected to two different types of time-dependent axial compressions. The equations of motion and compatibility are derived by considering Kirchhoff-Love assumptions and von Karman relations. The solution procedure is divided to two steps. First, the terms consisting of spatial derivatives are eliminated by applying a stress function and following the Galerkin method. Second, the terms with temporal...