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Total 89 records

    Environmental effects on the bond at the interface of fiber-reinforced polymer and masonry brick

    , Article Journal of Reinforced Plastics and Composites ; Volume 36, Issue 18 , 2017 , Pages 1355-1368 ; 07316844 (ISSN) Toufigh, V ; Yarigarravesh, M ; Mofid, M ; Sharif University of Technology
    Abstract
    This study examined the bond at the interface of masonry bricks and fiber-reinforced polymer when exposed to five environments. Three fabrics (aramid, carbon, and glass) and one type of epoxy resin were used. A total of 375 brick-fiber-reinforced polymer specimens were made using wet lay-up technic and exposed to chemical solutions at four pH values (2.5, 7, 10, and 12.5) and substitute seawater. The effect of dry heat on the bond at the interface was also investigated. Single-lap shear tests were then carried out on the samples after 2, 4, 6, 8, 10, and 13 weeks of exposure. The experimental results indicated that freshwater and seawater had a considerable effect on the bond strength of... 

    Rapid manufacturing

    , Article Collaborative Engineering: Theory and Practice ; 2008 , Pages 127-152 ; 9780387473192 (ISBN) Asiabanpour, B ; Mokhtar, A. R ; Houshmand, M ; Sharif University of Technology
    Springer US  2008
    Abstract
    This chapter defines rapid manufacturing (RM) as a technique for manufacturing solid objects by the sequential delivery of energy and/or material to specified points in space. Current practice is to control the manufacturing process by using a computer-generated mathematical model. This chapter compares the large speed and cost advantages of RM to alternative polymer or metal manufacturing techniques such as powder metallurgy manufacturing or die casting. Moreover, the RM as an application of solid freeform fabrication for direct manufacturing of goods is addressed. Unlike methods such as computer numerical control (CNC) milling, these techniques allow the fabricated parts to be of high... 

    Modeling of Crumb Rubber Concrete for a Structural Column by Evaluating the use of FRP

    , M.Sc. Thesis Sharif University of Technology Ghaznavi Doozandeh, Soheil (Author) ; Khaloo, Alireza (Supervisor)
    Abstract
    The research shows that the compressive strength of concrete reduced by replacing crumb rubber in concrete mix design compared to normal concrete mix design. However, there have been a couple of utilizations investigated to date for the structural utilization of these materials. Crumb rubber is usually provided from recycled rubber from automotive and truck scrap tires. During the recycling process steel and triviality are removed, leaving tire rubber with a granulose cohesiveness. The additional crumb-rubber aggregate has a significant effect on concrete mix porosity which affects both the plastic state workability and hardened state mechanical properties. This research depicts an... 

    Flexural Strengthening of Reinforced Concrete Beams by FRP Composites to Reduce Creep Deflection

    , M.Sc. Thesis Sharif University of Technology Zarringol, Mohammad Reza (Author) ; Kazemi, Mohammad Taqhi (Supervisor)
    Abstract
    The strengthening of reinforced concrete structures with externally bonded fibre reinforced polymer (FRP) laminates has shown excellent performance, so this technology is rapidly replacing externally bonded steel plates, steel or concrete jackets, and many traditional techniques available. In this study strengthening of reinforced concrete beams by GFRP to reduce creep deflection is investigated by mathematical method using available relations. Five RC beams with different dimensions, with and without strengthening with GFRP laminate, were investigated for their creep deflection. The creep coefficient of beams selected from experimental result that were mentioned in RILEM DATA BANK. In this... 

    Investigation of Progressive Collapse Resistance of RC Structures Retrofitted at Joints by FRP Sheets

    , M.Sc. Thesis Sharif University of Technology Khazaee, amin (Author) ; Kazemi, Mohammad Taghi (Supervisor)
    Abstract
    Progressive collapse in the structures can be happened as a result of many events such as terrorist attack, planes or vehicle collision to the structures and etc. Researchers’ attention to this phenomenon after occurring progressive collapse in Ronan Point building attracted and by happening terroristic attacks in Alfred P. Murrah and WTC buildings, studies in this field has developed extensively, meanwhile some of the codes, including UFC 4-023-03 or GSA, have proposed general instructions and analytical methods for increasing the strength of the structure against progressive collapse. If the structure in this analysis, does not meet the acceptance criteria of the code, the structure must... 

    Flexural Response Prediction of Concrete Beams Pre-Stressed with FRP Bars

    , M.Sc. Thesis Sharif University of Technology Momeni, Sajad (Author) ; Kazemi, Mohammad Taghi (Supervisor)
    Abstract
    Fiber Reinforced Polymer (FRP) tendons are suitable to be used in concrete beams exposed to aggressive environments. This study proceeds the design and it presents the flexural capacity (in relation to the moment-curvature) for composite sections (reinforced with steel bars and pre-stressed FRP) rectangular, T-section which has been bent and broken. The failure is in attending with strain softening, stress hardening of fiber reinforced concrete (FRC) and reinforcing with steel bars and polymer. Using the predicted moment-curvature relationship, a numerical method is used to estimate the load deflection response at sample beams under concentrated and uniform loads. A parametric study will be... 

    Enhancement of bond characteristics of ribbed-surface GFRP bars with concrete by using carbon fiber mat anchorage

    , Article Construction and Building Materials ; Volume 134 , 2017 , Pages 507-519 ; 09500618 (ISSN) Ashrafi, H ; Bazli, M ; Vatani Oskouei, A. V ; Sharif University of Technology
    Abstract
    The bond of fiber-reinforced polymer (FRP) reinforcement is expected to be more sensitive to the strength and geometry of the ribs than conventional steel reinforcement. In this study, the effect of carbon fiber mat anchorage on the pullout behavior of glass fiber-reinforced polymer (GFRP) bars embedded in normal concrete is studied. The studied parameters were the compressive strength of the concrete (16 MPa, 24 MPa, and 37 MPa), and, the length and diameter of the anchorage. In total, 15 variables were studied. Ribbed GFRP bars with 10 mm nominal diameter and 80 mm embedment length, ld, (which is 8 times the bar diameter) were considered. Based on the results for concretes with the... 

    Effect of thermal cycles on mechanical response of pultruded glass fiber reinforced polymer profiles of different geometries

    , Article Composite Structures ; Volume 223 , 2019 ; 02638223 (ISSN) Jafari, A ; Ashrafi, H ; Bazli, M ; Ozbakkaloglu, T ; Sharif University of Technology
    Elsevier Ltd  2019
    Abstract
    This study investigates the effect of Thermal cycles on the mechanical properties of GFRP pultruded profiles with different geometries. Bending specimens consisted of I-shaped and U-channel profiles that were tested in three-point bending along their both principal weak and strong axes, whereas box profiles and laminates were used in compression and tension tests, respectively. Each specimen was exposed to a range of thermal cycles, between −20 °C and 20 °C. The failure modes of the profiles were closely investigated at both major and minor scales. Results were analyzed using ANOVA to determine the influence of each factor and a model was developed to predict the strength retention of... 

    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
    Abstract
    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... 

    Experimental and probabilistic investigation on the durability of geopolymer concrete confined with fiber reinforced polymer

    , Article Construction and Building Materials ; Volume 334 , 2022 ; 09500618 (ISSN) Anvari, M ; Toufigh, V ; Sharif University of Technology
    Elsevier Ltd  2022
    Abstract
    This study investigates the durability of confined geopolymer concrete with fiber-reinforced polymer and compares the results with ordinary Portland cement concrete (OPCC). Two hundred and seventy geopolymer concrete (GPC) specimens with different mix designs (fly ash- and granulated blast furnace slag(GBFS)-based GPC) were prepared and then wrapped with two different fiber-reinforced polymers (carbon and glass FRPs). For 12,960 hrs (eighteen months), the specimens were exposed to four different pHs (2.5, 7 (water), 7.25 (saltwater), 12.5). The reliability analysis was performed after modeling the compressive strength over time. Based on the results, the ductility of all specimens decreased... 

    Experimental Investigation on Debonding between FRP sheets and Structures

    , M.Sc. Thesis Sharif University of Technology Haghighi, Sina (Author) ; Toufigh, Vahab (Supervisor)
    Abstract
    This study has investigated the effects of different environmental conditions on the bond at the interface between two fiber reinforced polymer (FRP) layers. A total of 945 single lap splice coupons with three bond length were made using wet lay-up technic. There were used three unidirectional fabrics and one type of epoxy resin. A Uniaxial tensile test was performed on samples after 2, 4, 12, 20, 28, 36 and 48 weeks of exposure. Also series of test were conducted in order to determine the minimum lap splice length of single splice FRP samples. The experimental results indicated reduction of bond strength in glass specimens that was 17 % after 48 weeks of exposure while for same amount of... 

    Refinement of Buckling-restraint Braces Behavior Using Fiber Reinforced Polymer (FRP) Strips

    , M.Sc. Thesis Sharif University of Technology Bashiri, Mehdi (Author) ; Toufigh, Vahab (Supervisor)
    Abstract
    In order to enhance the behavior of structures during an earthquake, various system have been proposed and used in recent years. The main purpose of these systems is to provide enough deuctility to dissipate the input energy of the earthquake. Buckling restrained braces are used extensively in seismic-restraint structures due to their sutiable cyclic behavior. They consist of a core energy dissipation and external restraining component. The purpose of this study is to improve the behavior of BRBs using FRP strips as a restraining component. In this study ABAQUS is used to model analyze the structure. Concrete Damage Plasticity (CPD) is used to model concrete, Hashin model used for FRP strips... 

    Finite Element Modeling of RC Slabs with Cut-Out and Strengthened with FRP

    , M.Sc. Thesis Sharif University of Technology Mazrouei, Majid (Author) ; Kazemi, Mohammad Taghi (Supervisor)
    Abstract
    In some cases, because of the need for installations, creating cutouts in the existing RC slabs will be necessary whereas these cutouts can cause weakness in the strength and stiffness of the slabs. Nowadays, expanding the use of FRP materials can provide the possibility of easier strengthening of such slabs. There are various methods for strengthening with FRP including Externally Bonded FRP sheets, Near Surface Mounted FRP rebars, and Mechanically Fastened FRP sheets. To select the most appropriate techniques for strengthening RC slabs with cutouts, it is essential to know different structural performance of these strengthened slabs. This research tends to model one and two-way spanning RC... 

    Modeling of the Behavior of Prestressed Concrete Column Confined by CFRP Composites

    , M.Sc. Thesis Sharif University of Technology Yazdani, Mohammad (Author) ; Kazemi, Mohammad Taghi (Supervisor)
    Abstract
    Because of mistakes in the design and calculation, incoherence between construction and design, structural changes, changes in loads and also damages caused by the passage of the time, concrete structures need to be improved and strengthened. Polymeric sheets reinforced by fibers (FRP), according to their appropriate characteristic, are more efficient for strengthening concrete structures. Most studies on confined columns refers to confined RC columns with FRP and less mentioned about prestressed columns. In this study, the behavior of prestressed columns is analyzed by modeling a case of prestressed column in a nonlinear analysis software. Samples of confined concrete columns with CFRP and... 

    Experimental Study of Bond in Curved FRP-Strengthed Beams

    , M.Sc. Thesis Sharif University of Technology Afshari, Majid (Author) ; Vafai, Abolhassan (Supervisor)
    Abstract
    Through the recent years application of FRP material in structural engineering has been developed significantly. According to possible changes of a building function during its lifetime or alteration of the building codes, building structures usually need to be strengthened. Referring to merits of FRP material, its application seems to be a convenient idea toward the cited requirement. Curved beam and slab are known as highly used elements in building structures. Bridges composed of horizontal or vertical arches could be noted as common examples which need to be reinforced by FRP. However curved concrete surfaces, reinforced by FRP plates, seem to be studied than it is really required; For,... 

    Compressive Behavior of Confined Concrete Column with FRP Layers

    , M.Sc. Thesis Sharif University of Technology Mohammadian, Armita (Author) ; Khaloo, Alireza (Supervisor)
    Abstract
    In recent years, the use of fiber reinforced polymer (FRP) jackets, as an external lateral confinement has found considerable attention in retrofitting and strengthening existing reinforced concrete (RC) columns in earthquake prone areas. The FRP composites have numerous advantages such as ease in application, high strength and stiffness-weight ratio, no corrosion and negligible changes in the member dimension. Most of previous studies have concentrated on evaluation of the effect of confinement with spiral bars or FRP composites, separately. However, in practice both types of confinements exist in strengthening RC columns.
    This paper presents the results of a computational modeling to... 

    Numerical Analyses for Flexural Behavior of Bridge Deck Strengthened with Frp Sheets Using Partially Bonding System

    , M.Sc. Thesis Sharif University of Technology Kangani, Ashkan (Author) ; Vafai, Abolhassan (Supervisor)
    Abstract
    During times, reinforced concrete sturctures might need to be strengthened due to environmental factors, material properties, design errors or changes indesign guidelines.Fibre-reinforced-polymer (FRP)composites are prominentmaterialsfor this purpose. Externally full bonding systemhas been widely used for flexural strengthening of reinforced concrete sturctures with FRP. However, the drawback of using this strengthening system is the high reduction of structure's deformability.In this research, partially bonding system used in finite element modeling of a bridge’s deck to increase deformability compared to full bonding system. Results showed that not only deformability but also load... 

    Numerical Analysis of FRP Strengthened Beam with Lingitudinal Grooves

    , M.Sc. Thesis Sharif University of Technology Samea, Parham (Author) ; Mostofinejad, Davood (Supervisor)
    Abstract
    Strengthening and rehabilitation of concrete structures significantly became a dynamic construction field of activity through the years. Strengthening concrete structures by means of fiber reinforced polymers (FRP) plates or sheets over the tensile face of flexural members is stated to be an effective rehabilitation technique. Numerous studies have been carried out over the years, taking into account the FRP strengthening methods. In this regards, premature failures induced as a result of composite plate de-bonding is of great importance in such members.
    In a reinforced concrete beam de-bonding may be induced by a major flexural crack in the mid-span.
    Loading of a FRP strengthened... 

    Effect of Corner Radius on Axially-Loaded Square RC Columns Confined with FRP Laminates

    , M.Sc. Thesis Sharif University of Technology Mohammadi Samani, Ali (Author) ; Mostofinejad, Davoud (Supervisor)
    Abstract
    FRP confinement studies on concrete square columns and its effect on design and retrofitting has been the topic of numerous studies in recent years and due to wide spread usage of FRP in structural retrofitting, these studies are still carried out by researchers. One of the most common and accurate methods for predicting the behavior of structures is modeling by Finite Elements Method (FEM). This study aims to assess the effects of corner radius on axially loaded reinforced FRP-confined concrete columns and their behavior for different corner radiuses using FEM software. Using the capability of FEM in ABAQUS software (V 6.8-1), the behavior of square reinforced concrete (RC) columns... 

    Numerical Study on Behavior of RC Shear Wall Retrofitted with FRP Sheets

    , M.Sc. Thesis Sharif University of Technology Shadan, Fariba (Author) ; Khalu, Alireza (Supervisor)
    Abstract
    Shear wall has been widely used in RC structures due to high initial stiffness and lateral load capacity. Hence, the behavior and effectiveness of retrofitting technique on shear wall are needed to be investigated widely. Among several available techniques for retrofitting RC structures, fiber reinforced polymer (FRP) is quite effective because of its high strength-weight ratio, high resistance to corrosion and easy handling and installation. Several researchers have investigated on the behavior of retrofitted RC members with FRP jackets like columns. However, application of FRP laminates on RC walls has attracted less attention by researchers. In this study a numerical investigation on...