Sharif Digital Repository

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... 

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... 

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... 

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... 

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... 

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... 

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... 

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... 

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,... 

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... 

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... 

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... 

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... 

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...