Sharif Digital Repository

Retrofitting of reinforced concrete and steel structures is a very important issue in Structural Engineering due to the reasons such as drawbacks in previous codes, revision of application of structures , destructive environmental factors and deficiencies in construction process.
Strengthening of structures with FRP composites is one of the methods that have been welcomed by researchers due to its unique properties including high tensile strength, light weight, simple application and resistance to corrosive environment. Although the main purpose of retrofitting is to increase the overall load carrying capacity of the structures, the failure mechanism of the strengthened member is also... 

Steel bracing systems can be used effectively for seismic retrofitting of existing RC buildings as well as for seismic design of new building. Steel bracing system has been used to increase the lateral load resistance of steel structures. In recent years the concept of steel bracing has also been applied to the retrofitting of reinforced concrete frames, especially to improve seismic performance of non-ductile reinforced concrete buildings. The use of steel bracing systems for seismic rehabilitation of RC frames offers some advantages such as (a) minimal added weight to the structure; (b) ease and speed of construction;(c) increased architectural flexibility; in comparison with RC shear... 

Composite Reinforced Concrete-Steel (RCS) frames which have reinforced concrete columns and steel beams attracted a lot of attention in recent years. They take advantage from the benefits of both reinforced concrete and steel frames thorough using the optimum combination of concrete and steel structural elements. In this research six structures including three 3-story, and three 6-story buildings are designed in a region with very high seismicity risk. These structures include composite RCS moment frames, special steel moment frames, and reinforced concrete special moment frames. RCS moment frames which are designed they not only have reinforced concrete columns similar to reinforced... 

The observed response of medium rise buildings during sever earthquakes worldwide has indicated that RC buildings with shear walls behave considerably better than other buildings. The conviction that shear walls are inherently brittle still prevails amongst engineers, and therefore, they usually prefer to choose moment resisting RC frames without shear walls. In this study, a number of RC frames, with and without shear walls are designed in accordance with the seismic codes, and are then subjected to an assemble of severe earthquakes. The results of timehistory nonlinear analyses of these models are then used to investigate the effect of the presence of shear walls within the framework of... 

The purpose of this research is to investigate the seismic behavior of plane moment resisting frame consisting of steel-concrete columns and steel I beams utilizing fragility curves. Due to the great influence of the column type in seismic performance of structure. To reach an optimal system, different types of steel-concrete composite columns has been used in the models and the fragility curve of each one is compared. Steel-Concrete composite columns can be divided into three types: (1) concrete filled steel tube (CFT), (2) steel reinforced concrete (SRC) and (3) new combinations of (1) and (2). Due to the abundance of the use of concrete filled steel tube (CFT) and steel reinforced... 

Shape memory alloys (SMAs) are metallic materials that have unique properties, including shape memory effects, superelastic effects, and high damping characteristics. Recovery of large deformation and capability of energy dissipation during mechanical loading-unloading cycles are special properties of superelastic effect of shape memory alloys. Due to these distinctive macroscopic behaviors, not present in most traditional materials, SMAs are the basis for innovative applications like devices for protecting buildings from structural vibrations. This paper presents a numerical investigation aimed at evaluating the improvements achievable through devices for passive seismic protection of... 

In recent years, composite systems comprised of reinforced concrete columns and steel beams, have taken consideration. This system took its own advantages both from steel and concrete systems. Joints of this system categorized into through-beam-type and through-column-type. In this research, after reviewing past studies, two kinds of the joints were modeled in ABAQUS finite element program and seismic performance of these two joints were evaluated. These two selected joints were tested by Chin-Tun Chen and Cheng-Chih Chen ( ) and also Hiroshi Kuramoto and Isao Nishiyama ( ). After verifying the finite element model with the experimental studies, a parametric study were conducted on the steel... 

The purpose of this research is evaluating of how the concrete filled composite tube column performs. Nowadays in the construction industry, a new kind of composite column called concrete filled composite tube (CFCT) columns, have become very common. Concrete and composite tubes posses’ complementary performance. Because on one hand, the composite tube makes proper confinement for concrete, on the other hand the concrete prevents internal and local buckling of the composite tube. One of the major advantages of the concrete filled composite tube columns compare to the reinforced concrete column is that there is no further need for reinforcement and molding, which results in swifter... 

Reinforced concrete (RC) column in building often needs strengthening either due to defects in the column themselves, having to support higher loads than those foreseen in the initial design of the structure or as the result of ageing or accidental damage such as earthquake force. The use of FRP wrapping, steel caging or reinforce concrete jacketing for this purpose is now a common practice in many countries throughout the world. Even though a considerable number of researches have been conducted on retrofitting methods during past years, but very limited researches have been done to compare these methods. This research has investigated the effect of jacketing from different views. The... 

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)... 

In recent years, the use of fibers has found considerable attention in concrete structures as in spillways, basins of dams, shell structure, industrial floors, and bridge pedestrians. Fibers modify the brittle nature of concrete and make the composite behave ductile under various types of loading. Fibers have numerous advantages such as higher impact resistance, less shrinkage, smaller crack width, higher durability and low expense for repair and maintenance.
Till now, no adequate data has been reported on concrete beams reinforced with high volume fiber. In this study, flexural behavior of concrete beams reinforced with high volume steel fibers is experimentally investigated. Concrete... 

Low tensile strength and also low strain capacity make plain concrete a ‘brittle’ material. To overcome this shortcoming, the addition of fibre as a reinforcing material has proved to be a reasonable solution. One of the crucial factors in deciding to make this type of concrete is the cost of fibre, which varies depending on its type. In this project a special type of fibre which does not cost a lot and at the same time has a high strength has been used. To investigate the effect of the fibre on the tensile strength of concrete, splitting tensile test (Brazilian test) was adopted. Altogether, 30 standard cylindrical specimens with dimensions of 15 × 30 cm2 were made (3 of each type) which... 

Dynamic behavior of space structures are of great complexities. On the event of severe earthquake these structures exhibit high resistance and on the other hand, their high rigidity and small deformation makes it necessary to pay attention to their dynamic behavior, especially when combined with other types of structural systems. Also due to lack of sufficient codes and references, their dynamic behavior is still unknown to a great extend. Among these kinds of structures, reinforced concrete double curvature shells, and especially funicular shells, are much more important than others. In this thesis, dynamic response of these kind of structures, especially reinforced concrete domes, in... 

While there are many advantages associated with concrete, including high compressive strength, durability and so forth, on the contrary, it has several disadvantages which may make engineers somewhat reluctant to use it. These include low tensile strength, high brittleness, low resistance to impact, large dimensions of structural cross sections, etc. In recent years, there have been many attempts to surmount these disadvantages by various means such as adding pozzolans, using FRPs, fibres, etc. In this project, the effects of using a special type of high strength steel fibre is studied. In order to investigate the effect of this fibre on the compressive behavior of concrete, 30 cylindrical... 

Because of absence of adequate studies, design of deep beams with web openings has not yet been covered by most codes of practice. The most studies have been on simply supported deep beams with web openings and have been set up experimentally. There are very few tests of continuous deep beams available in the literature. So it was decided in this thesis the behaviour of concrete continuous deep beams with web openings using finite element software ANSYS to be investigated. Primary purpose of this thesis has been evaluating the use of finite element analysis method for analysis of concrete continuous deep beams with web openings. The next target of this thesis has been assessment of... 

Heavy damage developed from near field earthquake in resent years cause serious attention to this problem. Investigation shows that these records include large energy pulse, unlike far field earthquake. Overall effect of near field earthquakes ignored in the most building codes. The purpose of this investigation to find effect of near field earthquake on reinforced concrete moment frames. To achieve this goal Erduran damage index is efficient way to calculate damage. Two 4th and 8th story reinforcement concrete moment frame buildinges with moderate and high ductility designed by strength criterion. Seven pairs of near field earthquakes and seven pairs of far field earthquakes scaled and use... 

This study inspects the flexural response of RC beams at the presence of compressive GFRP bars as well as tensile bars. Total of 9 reinforced beams were investigated. Three values of tensile reinforcement percentage were considered. For each tensile reinforcement value, three types of compressive reinforcement were taken into account which are classified into zero compressive bars, less than tensile reinforcement value and similar to tensile reinforcement value. The concrete was used in this study is C45 and as a constant parameter.Specimens were tested with four-point bending method using the actuator equipped at the strong floor laboratory to attain maximum flexural strength and... 

Seismic loads are still a challenge for structures and engineers invent and provide seismic resisting systems to resist better against it. Concrete shear walls are well-known seismic resisting system that has had an acceptable performance in occurred seismic events. This system costs noticeable amount of time and material. Fiber-reinforced concretes can be useful to reduce negative effects and provides more positive effects like tensile strength, ductility, impact resisting and etc. Also changes in wall appearance such as corrugating helps to improve shear wall performance as it improves other kinds of plates and shell shaped members in structures. In this thesis, the focus is on “corrugated... 

The aim of the present study is to investigate the effects of using hybrid fibers on rheological, mechanical and durability properties of the high-strength Self-Consolidating Concrete (SCC). For this purpose, two types of fibers including hooked-end steel fibers and polypropylene fibers were used. In this study, a total of eleven mixtures were used: one as a control mix, one containing 0.5% steel fibers, four containing 0.5% hybrid fibers (steel and polypropylene), one containing 1.0% steel fibers and the four containing 1.0% hybrid fibers (steel and polypropylene). For investigating the rheological properties, slump flow, J-ring and V-funnel tests were performed. Mechanical properties were... 

This thesis presents an extension of an analytical method previously introduced for evaluation of the deformation capacity of RC columns. The method utilizes fiber elements to arrive at nonlinear moment-curvature relationship for each segment. An existing stress-strain model has been modified and used in this study. This model considers the crushing failure of confined concrete, buckling of longitudinal reinforcements in compression, and their fracture in tension. It also accounts for the spiral fracture. This method was employed to determine the force-displacement diagrams for circular RC columns dominated by flexural mode of failure, and was calibrated against a number of relevant...