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Flexural Response Prediction of Concrete Beams Pre-Stressed with FRP Bars
, M.Sc. Thesis Sharif University of Technology ; 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...
Seismic Behavior Comparison of RC Shear Walls Strengthened Using FRP Composites, Steel Elements, and Concrete Jacket
, M.Sc. Thesis Sharif University of Technology ; Khaloo, Alireza (Supervisor)
Abstract
This paper aims at investigating the seismic behavior of strengthened reinforced concrete (RC) shear walls using a 3D finite element analysis. A series of four different configurations of carbon fiber reinforced polymer (CFRP) composites, four different schemes of steel elements and two different schemes of concrete jacket are utilized to compare the two methods of retrofitting RC shear walls with similar dimensions and reinforcement ratios. Nonlinear simulations of the RC shear walls are conducted under the action of lateral cyclic loading in ABAQUS Explicit software. In addition, the numerical modeling for RC walls strengthened by CFRP composites as well as steel elements are validated...
Dynamic Performance Enhancement of RC Slabs by Steel Fibers vs. Externally Bonded GFRP Sheets under Impact Loading
, Ph.D. Dissertation Sharif University of Technology ; Khaloo, Alireza (Supervisor)
Abstract
Recently, to improve the dynamic behavior of Reinforced Concrete (RC) slabs under impact load, the methods of externally bonding Glass Fiber Reinforced Polymer (GFRP) sheets to slab and internally reinforcing concrete by steel fibers have been proposed. Nevertheless, it is required to investigate the comparison between these two methods on response of RC slabs under impact loads. In this study, the influence of volume fraction of steel fibers, the number of GFRP sheet layers (one or two) and the arrangement of GFRP sheets (covering the whole or parts of surface), are examined. Performance of fourteen mm concrete slabs including one plain slab, one steel RC slab, three steel RC slabs...
Seismic Rehabilitation of Reinforced Concrete Columns with Fiber Reinforcement Polymers (FRP)
, M.Sc. Thesis Sharif University of Technology ; Kazemi, Mohammad Taghi (Supervisor)
Abstract
Previous researches has established that retrofitting RC (reinforced concrete) columns with FRP (fiber reinforced polymer) jackets is an effective means of providing external confinement to the column cross section. In an effort to evaluate FRP jacketing technology, this study focused on the confinement effectiveness of FRP jackets for rectangular building-type RC columns. Variables investigated include the following: the type of fibers (AFRP, CFRP), the thickness of the jacket, the shape (rectangular or circular) and aspect ratio of the cross section, and the sharpness of the corners of the rectangular cross sections. The sample structures were designed initially without lateral forces and...
Strengthening RC Arch Structures Using FRP Laminate
, M.Sc. Thesis Sharif University of Technology ; Khaloo, Alireza (Supervisor) ; Kazemi, Mohammad Taghi (Supervisor)
Abstract
Although considerable researches have been conducted on strengthening RC structures using FRP method during past years, a few researches have been reported on RC arch or curved structures strengthened by FRP. In this study, behavior of RC arches strengthened by FRP strips is investigated. The behavior of strengthened RC arches under gravitational load is analyzed using finite elements method. The arches are modeled by appropriate software in order to evaluate the behavior. The structural behavior of arches is more complicated. So, the estimation of the effect of strengthening using FRP technique on such structures is hard in comparison with traditional RC beams. In this study, the effect of...
Rehabilitation of Reinforced Concrete Coupling Beams With FRP
, M.Sc. Thesis Sharif University of Technology ; Mostofinejad, Davood (Supervisor)
Abstract
Shear walls are commonly used in tall concrete buildings to resist lateral loads. Due to the presence of regular door or window openings, a shear wall is often divided into smaller wall units coupled together by coupling beams. In any case, the earthquake resistance of a coupled shear wall structure is highly dependent on the nonlinear behaviour, especially the strength and ductility, of the coupling beams. Many existing building structures without provisions for resisting earthquake loads might no longer be considered to be up to the new standard due to increased-load specifications in the seismic code. A large number of RC coupling beams might require rehabilitation or retrofitting to...
Strengthening Reinforced Concrete Deep Beams Using FRP Systems
, M.Sc. Thesis Sharif University of Technology ; Kazemi, Mohammad Taghi (Supervisor)
Abstract
In recent years, the development of the plate bonding repair technique has been shown to be applicable to many existing strengthening problems in the building industry. This technique may be defined as one in which composite sheets or plates of relatively small thickness are bonded with an epoxy adhesive to, in most cases, a concrete structure to improve its structural behaviour and strength. The sheets or plates do not require much space and give a composite action between the adherents. The old structure and the new bonded-on material create a new structural element that has a higher strength and stiffness than original one. According to the available methods of analysis and design for...
Experimental Study of Bond in Curved FRP-Strengthed Beams
, M.Sc. Thesis Sharif University of Technology ; 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,...
Numerical Modeling of Shear Strengthening of Reinforced Concrete Deep Beams by Using FRP
, M.Sc. Thesis Sharif University of Technology ; Kazemi, Mohammad Taghi (Supervisor)
Abstract
The structural behavior of deep beams is different with usual beams as a result of the low span-to-height ratio. Shear failure load is less for deep beams. Implementation of externally bonded reinforcement such as fiber reinforced polymers (FRP) is a unique method for shear strengthening of deep beams. In this study, the effects of FRP layers on the web of the reinforced concrete deep beam have been investigated by a nonlinear finite element program. Five beams four of which were strengthened with FRP laminates were numerically modeled and the results were compared with experimental results. The effect of some governing parameters such as compressive strength of concrete, orientation of...
Compressive Behavior of Confined Concrete Column with FRP Layers
, M.Sc. Thesis Sharif University of Technology ; 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...
This paper presents the results of a computational modeling to...
Modeling of the Behavior of Prestressed Concrete Column Confined by CFRP Composites
, M.Sc. Thesis Sharif University of Technology ; 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...
Finite Element Modeling of RC Slabs with Cut-Out and Strengthened with FRP
, M.Sc. Thesis Sharif University of Technology ; 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 Crumb Rubber Concrete for a Structural Column by Evaluating the use of FRP
, M.Sc. Thesis Sharif University of Technology ; 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...
Finite Element Modeling of Flexural Behavior of RC Beams Using FRP
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofooei, Fayyaz (Supervisor)
Abstract
The flexural behavior of reinforced concrete beams through application of FRP is studied, considering FRP-concrete bonding. Moreover, the nonlinear behavior of concrete (generation of crack and crush) is taken into consideration. Different parameters such as the number of layers of CFRP sheets, the effect of tensile reinforcing bars, the effect of using glass fibers, and modeling resin layer between the concrete and FRP are investigated. The results are compared with the existing experimental tests and those obtained from analytical method, ACI 440.2R-08 and ISIS Canada. The results show that by adding CFRP sheet to the control beam, the stiffness and flexural strength of the beam improves...
Plastic Hinge Length and Drift Capacity of FRP Reinforced Concrete Columns under Seismic Loads
, M.Sc. Thesis Sharif University of Technology ; Kazemi, Mohammad Taghi (Supervisor)
Abstract
A brief overview of the proposed research, its aims, engineering relevance and applications; as well as expected achievements compared to the present state of the art:The plastic hinge length and ultimate drift calculations of frames are required in the performance based design of reinforce concrete structure. FRP-confinement increases the column’s shear resistance and ductility. FRP-confinement prevents concrete cover from spalling and increases the inelastic deformability of concrete in the potential plastic hinge region. GU et al. 2012 [24] studied the existing experimental results of confinement effects on the plastic hinge length. Mortezaei and Ronagh, 2012 [25], studied the plastic...
Behavior of Concrete Slabs Reinforced with FRP Bars, Design and Analysis
, M.Sc. Thesis Sharif University of Technology ; Khaloo, Alireza (Supervisor)
Abstract
Despite extensive studies on the behavior of reinforced concrete slabs, especially those reinforced with steel rebars, no comprehensive studies have been conducted on the behavior of concrete slabs reinforced with FRP rebars. Therefore, there are some ambiguities regarding the tensile and compressive behavior of these rebars in the load-bearing capacity of reinforced concrete slabs (depending on their amount in the slab and their combination with steel rebars). Hence, in this study, in order to ensure the accuracy of numerical simulations, the numerical 3D simulation of a one-way concrete slab reinforced with tensile FRP rebars was performed using the finite element Abaqus software....
Experimental Investigation on the Behavior of RC Arches Strengthened by GFRP and CFRP Composites
, M.Sc. Thesis Sharif University of Technology ; Khaloo, Alireza (Supervisor)
Abstract
The rehabilitation of old structures holds a lot of importance, as many structures with a life span of over 30 years are prone to severe damage and even collapse. To overcome this problem, the use of FRP sheets to strengthen structures is suggested. RC-arches have been used in many structures such as bridges and require specific consideration in terms of strengthening. So far, the influence of the number of FRP layers and location, the height of arch and percentage of reinforcement on strengthened arch behavior have not been investigated. In this research, reinforced concrete arch members strengthened with GFRP and CFRP were investigated. A total of 28 Specimens, including four...
On the Seismic Behavior of RC Frames with Brick Infilled Walls with Opening, Retrofitted by FRP
, M.Sc. Thesis Sharif University of Technology ; Rahimzadeh Rofooei, Fayaz (Supervisor)
Abstract
Wall systems are an essential part of the buildings and their capacity should be properly considered in their design. However, the seismic behavior of building systems with in-filled walls and their interaction is a very complex issue, yet to be understood. Using the in-filled walls in the buildings without including them in the design process changes the whole behavior of the structural system as well as their failure mechanism under earthquake excitations. On the other hand, there have been extensive researches on rehabilitation of the structures with in-filled walls or designing them as the main or one of the lateral load carrying systems against seismic input. In this research, first the...
Transverse Retrofit of Infilled Frames with FRP
, M.Sc. Thesis Sharif University of Technology ; Moghaddam, Hassan (Supervisor)
Abstract
Masonry buildings are wide spread in Iran and some other countries . These buildings are highly vulnerable to seismic excitations if not constructed in accordance with engineering fundamentals . Thus it is necessary to retrofit these structures to flee from humanitarian and economical damages inflicted by earthquakes. One of the critical vulnerabilities of masonry buildings is due to transverse instability of it’s infills . Therefore to study out of plane behavior of these elements , an infilled frame is modeled and analyzed with ABAQUS , the results of which is in good congruence with the experimental one . In this model , stress distribution due to one way arching action in the confined...
Strengthening RC Slabs under Various Loads and Boundary Conditions Using FRP Composites
, M.Sc. Thesis Sharif University of Technology ; Khaloo, Ali Reza (Supervisor)
Abstract
In recent decades the use of FRP materials for strengthening structures has been developed extensively, thanks to their high strength, sufficient stiffness, high durablity, and ease of use. A great deal of research has been conducted on strengthening reinforced concrete beams and columns with FRP composites. By contrast, not many researches are performed on slabs, especially two-way slabs. In these few researches, the loading and boundary conditions are limited to simplest ones. Therefore, in this thesis, the focus of attention is on strengthening reinforced concrete slabs under various loads and boundary conditions using FRP composites.
In this thesis, first, FRP composites and their...
In this thesis, first, FRP composites and their...