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    Compressive and Bond Behavior of Concrete-Filled Pultruded GFRP and PE Tubes Under Elevated Temperatures

    , Ph.D. Dissertation Sharif University of Technology Tabatabaeian Nimavard, Mojtaba (Author) ; Khaloo, Alireza (Supervisor)
    Concrete-filled GFRP and PE tubes are composite systems using the polymeric tubes as confinement for the marine structures to extend their service life. However, elevated temperatures and thermal cycles in marine environments can affect the behavior of such composite systems. In this investigation, the effect of elevated temperatures and thermal cycles on the performance of concrete-filled pultruded GFRP tubes (CFPGT) and concrete-filled polyethylene tubes (CFPT) is assessed, respectively. For this, different parameters such as concrete core strength (30 and 60 MPa), exposure temperature (25, 100, 200, 300, and 400°C), time exposure (60 and 120 min.), number of thermal cycles (50, 100, and... 

    The Performance in Temperature Increas of Bolted Slant Endplate Connection

    , M.Sc. Thesis Sharif University of Technology Zahmatkesh, Farshad (Author) ; Kazemi, Mohammad Taghi (Supervisor)
    The main goal of this research is to evaluate the vertical and slant bolted endplate connections performance in steel moment frame structures under thermal effect in elastic range for two cases. In the first case, frictionless and in the second case slips with friction are considered. By finite element analysis, the connections are simulated to study the performance and verify simplified models of vertical and slant bolted endplate connections due to increase in temperature. The results of a vertical bolted endplate connection and a slant bolted endplate connection due to increase in temperature are compared the effect of slope of end plate reduction of axial force on beam is investigated.... 

    Application of Endurance Time Method in Nonlinear Dynamic analysis of Elevated Tanks

    , M.Sc. Thesis Sharif University of Technology Rahmati, Mohammad (Author) ; Esmaeil Pourestekanchi, Homayoon (Supervisor)
    Endurance Time (ET) is a fairly comprehensive analytical method based on time history analysis applied for evaluating structural systems excited by dynamic loading of earthquake. In such evaluation assessment measure is based on endurance time of structure versus applied accelerogram function and parameters such as stiffness, lateral resistance, period of vibration and dynamic characteristics are not used directly. In this research nonlinear dynamic analysis of elevated steel tanks with laterally braced framed tower under the loading of earthquake records and ET accelerograms was studied and effectivity of ET method in analyzing such elevated tanks was verified. Due to complication of... 

    Effect of DEM Resolution on Hydraulic Modeling of Flood Inundation Area: Case Study of Gorganrood River, Northeast of Iran

    , M.Sc. Thesis Sharif University of Technology Khojeh, Shokoufeh (Author) ; Ataie Ashtiani, Behzad (Supervisor)
    Digital Elevation Models (DEM) is a crucial element of hydraulic models, including floods. Due to the lack of high-precision topographic data, including ground-based mapping hydraulic modeling is challenging. In recent years, remote sensing data, extensively used by many researchers in hydraulic modeling due to global coverage and free access. One of the most critical questions in hydraulic modeling is the efficiency of these DEMs in flood simulation. This research focused on using remote-sensing-based DEMs, such as SRTM-30m and 90m, ASTER-30m, and ALOS-12.5m DEMs, on the performance of the HEC-RAS-2D model in the Gorganrood river.The results showed that ALOS and SRTM-30m DEMs' accuracy and... 

    Behran Mehr Peyma's Activities Analysis

    , M.Sc. Thesis Sharif University of Technology Haghighi, Erfan (Author) ; Miremadi, Alireza (Supervisor)
    Behran Mehr Peyma (BMP) is an elevator equipment producer and trader in Iran which was established in 2004. At first they are producing some regular parts of elevator and then during these years they are trying to improve their work and expand their business till they have the 15% market share in elevator market in Tehran.In this thesis I am trying to use the SWOT and PETS methods to show the exact situation of BMP comparing to the whole market considering the competitors.During this reduction in the market I suggest to BMP to change some policies and use some of its strength to attract some new customers, changing their brand name and find a relation to contribute in some tenders and... 

    The Study of the Behaviour and Performance of a New Elevated Tank

    , M.Sc. Thesis Sharif University of Technology Tajmir Riahi, Hossein (Author) ; Khansari, Vahid (Supervisor)
    Various types of tanks are used to store a variety of liquids, drinking water, chemicals, petrochemicals, and liquefied natural gas. Of these, one type is ‘elevated tank’ which is used to provide the required pressure for the water distribution systems rather than satisfying the water demand. Satisfactory performance of tanks during strong ground motions is crucial for modern facilities. Theoritical and experimental investigations of the dynamic behaviour of liquid storage tanks are conducted to seek possible improvments in the design of such tanks to resist earthquakes. The behaviour and performance of a new elevated tank was studied in this work. It was carried out through finite elements... 

    Recycled ceramic waste high strength concrete containing wollastonite particles and micro-silica: A comprehensive experimental study

    , Article Construction and Building Materials ; Volume 201 , 2019 , Pages 11-32 ; 09500618 (ISSN) Zareei, S. A ; Ameri, F ; Shoaei, P ; Bahrami, N ; Sharif University of Technology
    Elsevier Ltd  2019
    This study investigated the effects of combined utilization of wollastonite particles and recycled waste ceramic aggregate (RWCA) on high strength concrete (HSC) properties. Two groups of mixtures were manufactured: 1) concrete mixtures in which cement was partially replaced with wollastonite at values ranging from 10% to 50%, and 2) mixtures in which wollastonite was used at the aforementioned dosages and 50% of natural coarse aggregate was replaced with RWCA. In addition, 10% of cement weight micro-silica was added to all mixtures. The concrete behavior in terms of strength, durability, resistance against acidic environment, and performance under elevated temperatures ranging from 20 °C to... 

    The performance of bolted slant endplate connections subjected to temperature increase

    , Article ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, ESDA2010, 12 July 2010 through 14 July 2010l ; Volume 2 , July , 2010 , Pages 207-217 ; 9780791849163 (ISBN) Zahmatkesh, F ; Talebi, E ; Sharif University of Technology
    In this paper the main goal is to evaluate the vertical and slant bolted endplate connections performance in steel moment frame structures under thermal effect in elastic field, and by a finite element software. the connections are simulated to complete and verify simple modeling of analytical and numerical analysis of the behavior of vertical and slant bolted endplate connections due to increase in temperature. The results that are obtained from performance of a vertical bolted endplate connection and a slant bolted endplate connection due to increase in temperature will be compared  

    Dynamic ageing and the mechanical response of Al-Mg-Si alloy through equal channel angular pressing

    , Article Materials and Design ; Volume 31, Issue 9 , October , 2010 , Pages 4076-4082 ; 02641275 (ISSN) Vaseghi, M ; Karimi Taheri, A ; Ig Hong, S ; Seop Kim, H ; Sharif University of Technology
    In this paper, dynamic ageing characteristics associated with the application of equal channel angular pressing (ECAP) to Al6061 alloy at elevated temperatures was investigated. Followed by ECAP, Vickers microhardness measurement on the cross-sectional planes and microstructural observations were undertaken using transmission electron microscopy. The combination of the ECAP process with dynamic ageing at both 100°C and 150°C resulted in a significant increase in hardness. The grain size was measured as ∼160. nm after four passes. A comparison with the published data on the same alloy processed by ECAP at room temperature and statically aged, suggests several advantages in incorporating... 

    Mechanisms governing microstructural evolution during consolidation of nanoparticles

    , Article Materials and Manufacturing Processes ; Volume 30, Issue 11 , 2015 , Pages 1397-1402 ; 10426914 (ISSN) Tavakol, M ; Mahnama, M ; Naghdabadi, R ; Sharif University of Technology
    Taylor and Francis Inc  2015
    In micron-scale, powder consolidation process is driven by diffusion phenomenon, while in nano-scale the higher surface energy of particles leads to some anomalous behaviors within the process. In order to investigate the nano-sintering occurrence, an atomistic approach is employed via molecular dynamics simulations. Within this approach, the effect of particle size and temperature is examined. The study of particle structure emphasizes on a transition on the governing mechanism of process depending on the material energy levels. The results show that in a specific particle size at low temperatures, the main sintering mechanism is the plastic deformation, while at elevated temperatures it... 

    Numerical study of solid fuel evaporation and auto-ignition in a dump combustor

    , Article Acta Astronautica ; Volume 67, Issue 7-8 , 2010 , Pages 774-783 ; 00945765 (ISSN) Tahsini, A. M ; Farshchi, M ; Sharif University of Technology
    Evaporation of polymeric solid fuels in backward facing step geometry subject to an inlet oxidizer flow at elevated temperatures is considered and convective heating of the fuel surface by the hot oxidizing inlet flow and subsequent mixing of the evaporated fuel with the oxidizer flow and its combustion is numerically studied. The objective of this work is to gain insight into the auto-ignition of the fuel and its controlling parameters in this configuration. The system of governing equations is solved with a finite volume approach using a structured grid in which the AUSM scheme is used to calculate the gas phase convective fluxes. The flowfield is turbulent and the SpalartAllmaras... 

    Casing failure in salt rock: numerical investigation of its causes

    , Article Rock Mechanics and Rock Engineering ; Volume 53, Issue 9 , 2020 , Pages 3903-3918 Taheri, S. R ; Pak, A ; Sharif University of Technology
    Springer  2020
    Numerous cases of casing failure have been reported worldwide. Depletion-induced compaction is one of the main factors that may cause casing failure. Stress perturbation in salt layers may accommodate rock flow which endangers the stability of cased wells. Besides, poor cementing jobs are recognized as one of the wellbore instability causes. These factors need to be considered to determine the mechanism behind the casing failure. In this study, the creep behavior of the caprock salt layer in the southwest Iranian oil fields is experimentally studied through a number of creep tests under conditions of elevated temperature and pressure. Then, a three-dimensional finite element analysis is... 

    The effects of elevated temperatures on the performance of concrete-filled pultruded GFRP tubular columns

    , Article Thin-Walled Structures ; Volume 169 , 2021 ; 02638231 (ISSN) Tabatabaeian, M ; Khaloo, A ; Azizmohammadi, M ; Sharif University of Technology
    Elsevier Ltd  2021
    Usage of concrete-filled pultruded glass fiber-reinforced polymer (GFRP) tubes (CFPGT) as columns can increase the service life of structures. However, marine structures such as oil platforms are always prone to fire because of the low resistance to the elevated temperatures. The purpose of this investigation is to evaluate the effects of concrete core strength (30 and 60 MPa), and exposure temperature (25, 100, 200, 300, and 400 °C) and time (60 and 120 min) on the compressive and bond behavior of CFPGTs. The properties of unexposed and exposed concrete core, pultruded GFRP hollow tubes, and CFPGTs were determined via compressive and disk-split tests. Also, the push-out test was used to... 

    Using satellite data to extract volume-area-elevation relationships for Urmia Lake, Iran

    , Article Journal of Great Lakes Research ; Volume 39, Issue 1 , March , 2013 , Pages 90-99 ; 03801330 (ISSN) Sima, S ; Tajrishy, M ; Sharif University of Technology
    Urmia Lake in the northwest of Iran is the second largest hyper-saline lake worldwide. During the past two decades, a significant water level decline has occurred in the lake. The existing estimations for the lake water balance are widely variable because the lake bathymetry is unknown. The main focus of this study is to extract the volume-area-elevation (V-A-L) characteristics of Urmia Lake utilizing remote sensing data and analytical models. V-A-L equations of the lake were determined using radar altimetry data and their concurrent satellite-derived surface data. Next, two approximate models, a power model (PM) and a truncated pyramid model (TPM), were parameterized for Urmia Lake and... 

    Comparative study on the effect of fiber type and content on the fire resistance of alkali-activated slag composites

    , Article Construction and Building Materials ; Volume 288 , 2021 ; 09500618 (ISSN) Shoaei, P ; Ghassemi, P ; Ameri, F ; Musaeei, H. R ; Chee Ban, C ; Ozbakkaloglu, T ; Sharif University of Technology
    Elsevier Ltd  2021
    Alkali-activated slag (AAS) binder has been recognized as a suitable material for construction applications owing to its low carbon footprint and good mechanical and durability performance. As a promising alternative to the conventional Portland cement binder, it is important to maximize the performance of AAS composites under normal and harsh environmental conditions such as exposure to fire. The use of fibers in a brittle matrix is a well-known approach to enhance the mechanical strength and cracking behavior under thermal loading. In this study, polypropylene fiber (PPF), glass fiber (GF), and basalt fiber (BF) are used at volume fractions of 0.5%, 1%, and 1.5% in AAS mortar mixes. First,... 

    Particle filtering-based low-elevation target tracking with multipath interference over the ocean surface

    , Article IEEE Transactions on Aerospace and Electronic Systems ; Volume 56, Issue 4 , 2020 , Pages 3044-3054 Shi, X ; Taheri, A ; Cecen, T ; Celik, N ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2020
    As radar signals propagate above the ocean surface to determine the trajectory of a target, the signals that are reflected directly from the target arrive at the receiver along with indirect signals reflected from the ocean surface. These unwanted signals must be properly filtered; otherwise, their interference may mislead the signal receiver and significantly degrade the tracking performance of the radar. To this end, we propose a low-elevation target tracking mechanism considering the specular and diffuse reflection effects of multipath propagation over the ocean surface simultaneously. The proposed mechanism consists of a state-space model and a particle filtering algorithm and promises... 

    Mechanical strength of CFRP and GFRP composites filled with APP fire retardant powder exposed to elevated temperature

    , Article Fire Safety Journal ; Volume 115 , 2020 Shekarchi, M ; Majdabadi Farahani, E ; Yekrangnia, M ; Ozbakkaloglu, T ; Sharif University of Technology
    Elsevier Ltd  2020
    Ammonium polyphosphate (APP) is one of the most widely used halogen-free flame retardant, added in various resins to improve the fire properties, such as flame and smoke spread ratings and LOI, of fiber-reinforced polymer (FRP) composites. This paper experimentally investigates the effects of using APP, as a fire-retardant filler, on mechanical properties (i.e. ultimate tensile, flexural, and bond strength) of glass fiber-reinforced polymer (GFRP) and carbon fiber-reinforced polymer (CFRP) composites. Based on two fiber types (i.e. carbon and glass) and three different APP mass fractions in resin (i.e. 0, 20, and 40% of total weight of matrix), six sets of specimens were prepared for each... 

    Effect of elevated temperatures on the compressive behavior of timber filled steel and pultruded GFRP tubes

    , Article Composite Structures ; Volume 271 , 2021 ; 02638223 (ISSN) Shekarchi, M ; Yekrangnia, M ; Biniaz, A ; Raftery, G. M ; Sharif University of Technology
    Elsevier Ltd  2021
    This study examines the use of timber as a filler material for steel and pultruded GFRP tube elements and the performance of these sections is compared to solid timber columns, hollow steel and hollow pultruded GFRP tube element after exposure to elevated temperature. In total, 102 specimens were fabricated and exposure to elevated temperature ranging from 20 to 700 °C was evaluated. It was found out that filled tubes using timber could improve the compressive strength and stiffness of tubular section specimens up to 73 and 212 percent, respectively. Timber filled steel tube (TFST) and hollow steel tube specimens had a better performance at elevated temperature in comparison to other... 

    Nonlinear vibrations and chaos in floating roofs

    , Article Journal of Computational and Nonlinear Dynamics ; Volume 7, Issue 2 , January , 2012 ; 15551415 (ISSN) Shabani, R ; Tariverdilo, S ; Salarieh, H ; Sharif University of Technology
    Variational principle is used to derive the nonlinear response of the floating roof of cylindrical liquid storage tanks due to harmonic base excitations. The formulation accounts for nonlinearity due to large deflections of the floating roof. The derived nonlinear governing equation for the sloshing response of the floating roof has a cubic nonlinear stiffness term similar to the well known Duffing equation. It is shown that accounting for large deflections could substantially reduce the wave elevation for near resonance harmonic excitations. Evaluating the response of the nonlinear model for increasing amplitudes of near resonance harmonic excitations gives rise to the appearance of sub and... 

    A trace-time framework for prediction of elevation angle over land mobile LEO satellites networks

    , Article Wireless Personal Communications ; Volume 62, Issue 4 , February , 2012 , Pages 793-804 ; 09296212 (ISSN) Seyedi, Y ; Rahimi, F ; Sharif University of Technology
    Elevation angle is one of the most significant parameters of land mobile satellite channels, subject to rapid variations in the case of Low Earth Orbit (LEO) satellite systems. In this paper a novel trace-based framework is proposed and analyzed which is capable of predicting elevation angle as a function of time during satellite visibility window. Trace-time based modeling makes the framework practical for real-time evaluation of elevation angle and its alteration incurred by communication links in LEO satellite systems. The proposed method is particularly suitable for development of communication channel models and services in mobile LEO satellite networks where path variability is of...