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    Investigation of hydroelastic effect in analysis of high-speed craft

    , Article Ships and Offshore Structures ; 2014 ; ISSN: 1754212X Zamanirad, S ; Seif, M. S ; Tabeshpur, M. R ; Yaakob, O ; Sharif University of Technology
    Abstract
    Hydroelastic effect in bottom slamming problem of high-speed craft is one of the most challenging issues in structural design. In this paper, numerical method is used to investigate the hydroelastic effect in bottom-water impact analysis of high-speed monohull craft. Slamming with two viewpoints of rigid and elastic structures (hydroelastic effect) is modelled by coupled computational fluid dynamic (CFD) and finite element method (FEM) techniques. The results showed that considering hydroelastic effect, especially in high-impact speed, reduces the structural deformations and stresses compared with quasi-statistic analysis. The effect of different parameters, such as boundary condition, plate... 

    Dynamic response of a moored semisubmersible in short-crested wave fields

    , Article Scientia Iranica ; Volume 11, Issue 4 , 2004 , Pages 351-360 ; 10263098 (ISSN) Heidari, A. H ; Borghei, S. M ; Sohrabpour, M ; Sharif University of Technology
    Sharif University of Technology  2004
    Abstract
    Wind generated sea states are more accurately modeled by short-crested wave fields. Whether or not these short-crested waves can induce larger response amplitudes in floating offshore structures is of great concern to offshore engineers. In this paper, the hydrodynamics of a moored semisubmersible in short-crested wave fields is investigated. Morison-based motion equations with nonlinear damping terms are used to analyze the dynamic behavior of the structure. A generalized three-parameter short-crested wave field is introduced as the incident wave. The effect of transverse phase lag, wave propagation angle and different ratios of in-line and transverse wave numbers are studied on the force... 

    The effect of foundation uplift on elastic response of soil-structure systems

    , Article International Journal of Civil Engineering ; Vol. 12, issue. 2 A , 2014 , p. 244-256 Jafarieh, A. H ; Ghannad, M. A ; Sharif University of Technology
    Abstract
    It is well-known that the behavior of soil-structure systems can be well described using a limited number of nondimensional parameters. This is the outcome of researches based on the premise that the foundation is bonded to the ground. Here, it is shown the concept can be extended to systems with foundation uplift. A set of non-dimensional parameters are introduced which controls the main features of uplifting systems. The effect of foundation uplift on response of soil-structure systems are investigated parametrically through time history analysis for a wide range of systems subjected to ground motions recorded on different soil types. In particular, the effects of uplift on displacement... 

    3-D Seismic Evaluation of on Grade Cylindrical Flexible Storage Tanks Considering Soil-Structure Interaction

    , M.Sc. Thesis Sharif University of Technology Andalib, Reza (Author) ; Rahimzadeh Rofooei, Fayaz (Supervisor)
    Abstract
    The circular flexible cylindrical liquid tanks usually are made of steel or aluminum and in majority of cases are built on grade due to its economic advantages. The most important part of a safe design of a storage tanks is the accurate estimation of the seismically induced lateral forces that should be transferred to its base through the tank shell and its support. Seismic behavior of liquid storage tanks is quite different from regular buildings and industrial structures due to its nonlinear behavior caused by complex distribution of hydrodynamic pressure, buckling of its walls, etc.. Moreover, the effect of rocking motion caused by the under laying soft soil, on its response parameters... 

    Seismic Behavior Evaluation of Anchored Cylindrical Fixed Roof Storage Tanks with Soil-Structure Interaction Effect

    , M.Sc. Thesis Sharif University of Technology Rasoulbeigi Fard, Mohammad Reza (Author) ; Rahimzadeh Rofouei, Fayyaz (Supervisor)
    Abstract
    The importance of the liquid storage tanks in this era is as much as their contained liquid that we use in our daily lives. Many studies have been carried out on these influential structures considering various aspects. The major damages inflicted to the liquid storage tanks in Loma Prieta, Lozan, Hokaido, Arzinkan, Northridge, Kobe, Izmit & Haiti Earthquakes, has led the researchers to perform various experimental and analytical studies on this regard in the last few decades. The most important part of a safe design of a storage tank is the accurate estimation of the seismically induced lateral forces that should be transferred to its base through the tank shell and its support. Moreover,... 

    Fluid-structure interaction analysis of airflow in pulmonary alveoli during normal breathing in healthy humans

    , Article Scientia Iranica ; Volume 23, Issue 4 , 2016 , Pages 1826-1836 ; 10263098 (ISSN) Monjezi, M ; Saidi, M. S ; Sharif University of Technology
    Sharif University of Technology 
    Abstract
    In this work, the human lung alveoli are idealized by a three dimensional honeycomb like geometry and a fluid-structure analysis is performed to study the normal breathing mechanics. In contrast to previous works in which the inlet flow rate is predefined, in this model, we have applied a negative pressure on the outside surface of the alveolus which causes air to flow in and out of the alveolus. The integration of the experimental curve of breathing flow rate was used to approximate the shape of the external applied pressure. Our Fluid-Structure Interaction (FSI) model has an advantage over other literature since it addresses both the fluid dynamics and solid mechanics, simultaneously. The... 

    Seismic performance of nonlinear soil-structure systems located on soft soil considering foundation uplifting and soil yielding

    , Article Structures ; Volume 28 , December , 2020 , Pages 973-982 Jafarieh, A. H ; Ghannad, M. A ; Sharif University of Technology
    Elsevier Ltd  2020
    Abstract
    In most of researches on soil-structure systems, it is assumed that the foundation is bonded to the ground where no foundation uplift is allowed. Uplifting makes changes in force–displacement behavior of the soil-structure systems, which in turn alters structural demands. In this research, a set of non-dimensional parameters is considered which controls the behavior of uplifting systems. The effects of foundation uplift on response of soil-structure system are investigated parametrically through time history analysis for a wide range of systems subjected to harmonic excitation and also ground motions recorded on soft soil with predominant period. It is seen that the response of systems with... 

    Numerical investigation of stability of deep excavations supported by soil-nailing method

    , Article Geomechanics and Geoengineering ; Volume 16, Issue 6 , 2021 , Pages 434-451 ; 17486025 (ISSN) Pak, A ; Maleki, J ; Aghakhani, N ; Yousefi, M ; Sharif University of Technology
    Taylor and Francis Ltd  2021
    Abstract
    Deep excavation in urban areas can cause instability problems due to significant settlement at the ground surface and large movements at the excavation facing walls. One of the most popular methods used to stabilise these excavations is utilising soil-nailing method. This method has also been widely used to stabilise natural slopes and earth retaining structures. Because of the complexity involved in the mechanism of this stabilising system due to interacting effects of the soil, nails, grout and shotcrete, numerical modelling with high accuracy should be used to analyse the behaviour of the soil-nailed walls. Considering all aspects of soil-structure interaction in the present research, a... 

    Unsteady supersonic aerodynamics based on BEM, including thickness effects in aeroelastic analysis

    , Article Journal of Fluids and Structures ; Volume 19, Issue 6 , 2004 , Pages 801-813 ; 08899746 (ISSN) Soltani, N ; Esfahanian, V ; Haddadpour, H ; Behbahani Nejad, M ; Sharif University of Technology
    2004
    Abstract
    A general three-dimensional aeroelastic solver is developed based on coupled finite element and boundary element methods and applied to investigate the flutter boundaries in supersonic flows. The boundary element method is applied to three-dimensional unsteady supersonic potential flow as the aerodynamic model and coupled with the finite element method for structural modelling, in order to construct the system of aeroelastic equations. The aeroelastic equations are solved for the flutter prediction using the frequency domain approach. Flutter boundaries for two types of wing planforms at supersonic speeds are determined and compared with the existing experimental results and previous... 

    Evaluation of Soil-Structure Interaction Effects in Seismic Behavior of 3D Models of Elevated Tanks, Using Absorbing Boundary Method

    , M.Sc. Thesis Sharif University of Technology Seyedpour Esmailzadeh, Saba (Author) ; Rahimzadeh Rofooei, Fayyaz (Supervisor)
    Abstract
    Elevated tanks are typically used to store water for drinking as well as fire fighting purposes. The failure of these critical structures during earthquakes can potentially lead to shortage of drinking water, difficulty in putting out fires, and substantial economical losses. Due to the fact that a large number of water tanks with insufficient seismic resistance were extremely damaged or collapsed during past earthquakes, (e.g. the elevated tank of Rasht in 1989 Gilan's earthquake), the reliability of these structures against failure under seismic loads is of critical concern. Numerous studies have analyzed and investigated the dynamic behavior of fluid storage tanks; however, most of them... 

    Evaluation of Seismic Response Parameters in On-Grade Cylindrical Steel Storage Tanks Considering Wave Propagation in Under Laying Soil

    , M.Sc. Thesis Sharif University of Technology Rezaei, Mohamad Hadi (Author) ; Rahimzadeh Rofooei, Fayaz (Supervisor)
    Abstract
    The circular flexible cylindrical liquid tanks are usually made of steel or aluminum and in majority of cases are built on grade due to its economic advantages. The most important part of a safe design of storage tanks is the accurate estimation of the seismically induced lateral forces that should be transformed to its base through the tank shell and its support . seismic behavior of the liquid storage tank is quite different from regular buildings industrial structures due to its nonlinear behavior caused by complex distribution of hydrodynamic pressure, buckling of its wall, etc.. moreover, the effect of rocking motion caused by under laying soft soil, on its response parameter could be... 

    Blind modal identification of structures from spatially sparse seismic response signals

    , Article Structural Control and Health Monitoring ; Vol. 21, issue. 5 , May , 2014 , p. 649-674 Ghahari, S. F ; Abazarsa, F ; Ghannad, M. A ; Celebi, M ; Taciroglu, E ; Sharif University of Technology
    Abstract
    Response-only identification of civil structureshas attracted much attention during recent years, as input excitations are rarely measurable for ambient vibrations. Although various techniques have been developed by which identification can be carried out using ambient responses, these techniques are generally not applicable to non-stationary excitations that structures experience during moderate-to-severe earthquakes. Recently, the authors proposed a new response-only modal identification method that is applicable to strong shaking data. This new method is highly attractive for cases in which the true input motions are unavailable. For example, when soil-structure interaction effects are... 

    Equivalent linear model for existing soil-structure systems

    , Article International Journal of Structural Stability and Dynamics ; Volume 16, Issue 2 , 2016 ; 02194554 (ISSN) Sameti, A. R ; Ghannad, M. A ; Sharif University of Technology
    World Scientific Publishing Co. Pte Ltd 
    Abstract
    The concept of equivalent linearization is extended for the soil-structure systems, in which the strength ratio (defined as the ratio of the yielding strength to the elastic strength demand) is known rather than the ductility ratio. The nonlinear soil-structure system is replaced by a linear single-degree-of-freedom (SDOF) system, which can capture the response of the actual system with sufficient accuracy. The dynamic characteristics of the equivalent linear SDOF system are determined through a statistical approach. The super-structure is modeled by an inelastic SDOF system with bilinear behavior, and the homogeneous half space beneath the structure by a discrete model, following the Cone... 

    Submicron particle deposition in pulmonary alveoli during cyclic breathing

    , Article Scientia Iranica ; Volume 24, Issue 4 , 2017 , Pages 1975-1984 ; 10263098 (ISSN) Monjezi, M ; Saidi, M. S ; Ahmadi, G ; Sharif University of Technology
    Sharif University of Technology  2017
    Abstract
    The prediction of deposition efficiency of submicron particles in the pulmonary alveoli has received special attention due to its importance for drug delivery systems and for assessing air pollutants health risks. In this work, the pulmonary alveoli of a healthy human are idealized by a three-dimensional honeycomb-like configuration and a fluid-structure interaction analysis is performed. In contrast to previous works in which the inlet flow rate is predefined, in this model, a negative pressure is imposed on the outside surface of the flalveolus which causes air to flow in and out of the alveolus. The resulting flow patterns confirmed that there was no circulation in the terminal alveolus.... 

    Soil-Structure interaction effect on fragility curve of 3D models of concrete moment-resisting buildings

    , Article Shock and Vibration ; Volume 2018 , 2018 ; 10709622 (ISSN) Anvarsamarin, A ; Rahimzadeh Rofooei, F ; Nekooei, M ; Sharif University of Technology
    Hindawi Limited  2018
    Abstract
    This paper presents the probabilistic generation of collapse fragility curves for evaluating the performance of 3D, reinforced concrete (RC) moment-resisting building models, considering soil-structure interaction (SSI) by concentration on seismic uncertainties. It considers collapse as the loss of lateral load-resisting capacity of the building structures due to severe ground shaking and consequent large interstory drifts intensified by P-Δ effects as well as the strength and stiffness deterioration of their lateral load carrying systems. The estimation of the collapse performance of structures requires the relation between the intensity measure (IM) and the probability of collapse... 

    The effect of soil-structure interaction on damage index of buildings

    , Article Engineering Structures ; Volume 30, Issue 6 , 2008 , Pages 1491-1499 ; 01410296 (ISSN) Nakhaei, M ; Ali Ghannad, M ; Sharif University of Technology
    2008
    Abstract
    The effect of Soil-Structure Interaction (SSI) on Park and Ang Damage Index in a Bilinear-SDOF model is investigated under seismic loading. This is done through an extensive parametric study. Two non-dimensional parameters are used as the key parameters which control the severity of SSI: (1) a non-dimensional frequency as the structure-to-soil stiffness ratio index and (2) the aspect ratio of the structure. The soil beneath the structure is considered as a homogeneous elastic half space and is modeled using the concept of Cone Models. The system is then subjected to three different earthquake ground motions as the representative motions recorded on different soil conditions. The analysis is... 

    Site-dependent strength reduction factors for soil-structure systems

    , Article Soil Dynamics and Earthquake Engineering ; Volume 27, Issue 2 , 2007 , Pages 99-110 ; 02677261 (ISSN) Ghannad, M. A ; Jahankhah, H ; Sharif University of Technology
    2007
    Abstract
    The effect of soil conditions on strength reduction factors (SRFs) is investigated. Both site effect and soil-structure interaction (SSI) effect are considered in the study with special emphasis on the latter effect. The structure is modeled as an elasto-plastic single degree of freedom (SDOF) system, whereas the underlying soil is considered as a homogeneous half-space. The half-space is also replaced by a simplified 3DOF system, based on the concept of Cone Models. The whole 4DOF model is then analyzed under a total of 54 strong motions recorded on different soil types. A parametric study is done for a wide range of non-dimensional parameters, which completely define the problem. It is... 

    Effects of Mechanical Loading Environment on Aneurysm

    , M.Sc. Thesis Sharif University of Technology Abdollahi, Rahim (Author) ; Abedian, Ali (Supervisor)
    Abstract
    Human body is subjected to body accelerations or vibrations in several circumstances. During gravitational changes, the hydrostatic pressure gradient along the body axis changes, and then body fluids are redistributed. Prolonged exposure to high level external acceleration may lead to serious or even fatal situations on account of disturbances in blood flow. Due to physiological importance of body acceleration many theoretical investigations have been carried out for the flow of blood under the influence of body acceleration. In this study, the mechanical loads that pilots experience during flight are considered. The aim of the present study is to investigate the effects of mechanical... 

    Probabilistic Estimation of Maximum Inelastic Displacement Demands for Performance-Based Design Considering Soil-Structure Interaction

    , M.Sc. Thesis Sharif University of Technology Aboutorabian, Elham (Author) ; Rahimzadeh Rofooei, Fayaz (Supervisor)
    Abstract
    In the current design Codes, the estimation of maximum inelastic Single Degree Of Freedom (SDOF) displacements is done through simplified procedures by either applying modification factors on maximum SDOF elastic displacement demands or by considering equivalent SDOF systems with elongated fundamental period and increased damping ratio. Thus, the inherent uncertainty caused by approximating maximum inelastic displacements with maximum elastic displacements is neglected. On the other hand, in time history dynamic analysis of structures, the free field recorded ground motions are applied to the base of structures. Obviously, this procedure would be correct when the structure is built on firm... 

    A plasticity-based constitutive model for the behavior of soil-structure interfaces under cyclic loading

    , Article Transportation Geotechnics ; Volume 14 , 2018 , Pages 41-51 ; 22143912 (ISSN) Hosseinali, M ; Toufigh, V ; Sharif University of Technology
    Elsevier Ltd  2018
    Abstract
    In this study, a new plasticity-based constitutive model is proposed for the behavior of soil-structure interfaces under monotonic and cyclic loadings. The features of the interface including the strain-softening behavior, phase transformation, steady-state, and dilatancy behavior were described by the proposed model with satisfactory accuracy. The proposed model does not require additional concepts such as damage or disturbance, and the model parameters can be obtained easily using straight-forward analyses of the results obtained from constant normal stress tests. Moreover, the results of the proposed model showed its capability in predicting the experimental results obtained from various...