Sharif Digital Repository

Most of the investigations during the two past decades focused on the effect of moisture and temperature on the bond at the interface of carbon or glass-fabrics and concrete, masonry or timber. Few investigations have studied the effect of chemical solutions, dry heat exposure and ultravilolent (UV) radiation on the bond at the interface of other types of fiber reinforced-polymers (FRPs) and masonry, timber and concrete in the short and long terms. Therefore, this research aims to investigate the effect of five chemical solutions with pH of 2.5±0.1, 7±0.1, 7.25±0.1, 10±0.1 and 12.5±0.1 on the interfacial bond strength between seven types of FRPs (unidirectional, bidirectional and hybrids)... 

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... 

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... 

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... 

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... 

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 of multi-story frames widely has been studied in recently. So that such studies can lead the earthquakes-resistance system to better performance. The dramatic growth of computer processing power make it possible that nonlinear dynamic analysis of structures with great precision could be done. One of the advantages of nonlinear analysis is achieve behavioral performance of structures during an earthquake. Knowledge of the performance, enables us to identify structural weaknesses result in devising to improve these. The aim of this study is to evaluate the seismic performance of reinforced concrete frames have been improved, using different techniques. The frames are designed... 

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... 

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... 

Retrofitting and strengthening existing structures is one of the most important concepts of structural and earthquake engineering. Strengthening of structures could be due to changes in application and applied load, errors in calculation, mistakes in construction, weakness of old codes, structural height increases and changes in environmental conditions. Different methods for increasing the flexural strength and ductility of reinforced concrete beams, as one of the major structural components, have been presented. This research presents an experimental study on the strengthening of reinforced concrete beams by reinforced concrete jackets (classical method) and Fiber Reinforced Polymer (FRP)... 

Recent investigations on construction engineering have determined that repairing of Reinforced Concrete (RC) by means of fiber reinforced polymer (FRP) composites is an effective method of retrofitting existing columns. The main research in this thesis focuses on the repair of concrete specimens which are damaged and their initial strength has been reduced. To achieve this purpose, through experimental procedures, the effect of confining damaged concrete cylinders by FRP, has been investigated. The experimental program included three parameters: type of fibers (glass or carbon), type of confining (full or partial), and the number of layers. First concrete cylinders were made and loaded to... 

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... 

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... 

The purpose of this study is to determine the effects of some strengthening methods such as steel jacketing, concrete jacketing and FRP wraps in the overall behavior of structures and introducing the most appropriate method. For this purpose a 14 story building with intentionally weak designed shear walls was considered, subsequently each of the strengthening methods were followed for the shear walls and relative structural outcomes like total stiffness and lateral movements were calculated, studied and compared and finally a guideline for choosing the most appropriate strengthening method for concrete shear walls is resulted. It is established that for the system with steel jacketing... 

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... 

Today, many evidences, including the distribution of galactic velocities, gravitational lensing observations, and the cosmic microwave background, show that there exist dark matter (non-baryon matter) in large-scale cosmological structures that are stable, free of charge and without color, which has gravitational interaction like normal matter. The hypothesis that weakly interacting massive particles (WIMPs) as a dark matter candidate with mass range of several tens of GeV to several teV and with the typical couplings of Electroweak order of magnitude, is an attractive and desirable model, Which naturally explains the density of cosmic dark matter in agreement with observations. Alongside... 

This study has been carried out for investigating the need for an appropriate and fast seismic analysis method to be applied in performance based design (PBD), and show the application of Endurance Time (ET) method and its advantages in PBD. The major goal of this project is analysis and study of behavior of concrete frames with retrofitted shear walls with FRP by ET method with acceleration functions which are compatible with actual earthquake and comparation with time history analysis, forand comparation of whole results with shear wall frames that are not retrofitted. Performance criteria of FEMA code were used fore comparation of two frame categories (retrofitted and not retrofitted).... 

The repair of pipes that deteriorate over time or due to various factors is a critical issue in engineering. Consequently, effective and novel repair methods, especially using FRP (Fiber-Reinforced Polymer) composites, have gained significant importance. In this research, the repair and connection of pipes using FRP are examined. In the pipe repair section, through hydrostatic testing, various factors such as the damaged area, the number of sharp corner points, the width of the sheets, the number of layers, and the pre- stress condition of the FRP are studied for their impact on the pipe's ultimate pressure tolerance. Also, in the pipe connection section, with hydrostatic tests, the ultimate... 

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... 

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...