Sharif Digital Repository

According to key importance of bridges in transportation system vital routes, a need to study and survey of bridges against destructive factors exist. Among these, bridges with concrete deck are widely used. One of the most important factors in destruction of these bridges is steel reinforcements corrosion and destruction of bridge deck. So in order to reduce the aggregation of reinforcements in critical sections and performance improvement of deck beams, a reinforcing substance which is not only resistant against corrosion but benefits from high resistance and stiffness is implemented.In this research the case studied bridge is simulated by finite elements software in two cases; reinforced... 

Performance of reinforced concrete frames is highly dependent on detailing of the joint connections between its members, such as beams and columns. To have a good structural behavior, joints must show ductile behavior and designed based on the philosophy of strong column-weak beam. In the case of sever lacking ductility, strength or even rigidity of the connections, or having a weak column-strong beam, in the existing structures, there is a need for seismic upgrading of the connection. There are several ways for seismic upgrading of this type of connections.In the last decade Fiber Reinforced Polymer (FRP) widely has been used to strengthening the reinforced concrete (RC) members. Most of... 

Performance based design was first introduced in order to evaluate seismic vulnerability of structures in retrofitting topic and was rapidly implemented in new design codes. The main cause conducting widely developing of performance based design methods, has been accurate estimation of seismic demand parameters. Since seismic structural members displacement during earthquake has a direct effect on the amount of sustained damages, displacement index has always been a key concept in performance based design. The main goal followed by this research is comparing the results obtained from the standard pushover method (with two theorems of distributed plasticity and plastic hinges) and the... 

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... 

This study deals with the monotonic behavior of reinforced concrete membranes. In the first step, small reinforced concrete membrane panels were studied. Examining the available test results on reinforced concrete panels, a new set of stress-strain relations for normal strength concrete and mild steel bars embedded in concrete. The salient features of the proposed constitutive laws are: 1) considering the effect of reinforcement ratio on average stress-strain relationships of cracked concrete; and 2) considering the gradual reduction of average stiffness of steel bars embedded in concrete. Equilibrium, compatibility, and constitutive relationships were incorporated into an algorithm to... 

The continual deterioration and insufficient strength of reinforced concrete (RC) structures has been a vital problem in the field of civil engineering such an extent that traditional methods of strengthening found to be inconvenient. Nowadays by increasing demands for retrofitting of structures, it necessitates the application of efficient, inexpensive and unobtrusive methods of strengthening. Common way on retrofitting was to use of steel plates externally bonded to RC members. Although this technique has proven to be reasonably effective, it has several distinct disadvantages such as susceptibility of the steel plates to corrode and the excessive weight of steel plates when used in... 

The modeling of mechanical behavior of Reinforced concrete Structures has been an important issue in civil engineering. In this thesis, an approach to the numerical modeling of different parts of these structures such as concrete and steel bars was presented. The model is based on damage and plasticity in porous materials. The behavior of steel materials was modeled through Von-Misses plasticity model while the coupling of the Gurson plasticity and a rate dependent damage model based on elastic strains were used for modeling the behavior of concrete materials. The effect of interaction between concrete and steel bar in RC members was considered through an experimental relation in which the... 

This study is devoted to the analysis and design of a recently proposed steel-FRP deck system. A methodology is being proposed to analysis the elastic behavior of the proposed deck. In this method the deck is modeled as an equivalent orthotropic plate which is constrained by rotational springs along its edges. An analytical model of the proposed deck is derived by using Rayleigh-Ritz method where the primary Rayleigh-Ritz shape functions are generated from orthonormal polynomials by using Gram-Schmidt procedure. The results of the proposed methodology show good agreement with finite element analysis results. In order to test the applicability of the proposed deck as buildings flooring... 

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)... 

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... 

In the last decade Fiber Reinforced Polymer (FRP) widely has been used to strengthening the reinforced concrete (RC) members. Most of the research works have been concentrated on the design of shear members with FRP layers. Based on the reported results, increasing the shear reinforcement more than a certain amount, the shear capacity and ultimate strength of reinforced concrete deep beam does not increased, On the other hand, The presence of web openings in such beams is frequently required to provide accessibility such as doors and windows or to accommodate essential services such as ventilating and air conditioning ducts, So the external strengthening of the reinforced concrete deep beams... 

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... 

Many of the major structure over coastal waters in the Kish Island due to the aggressive condition are showing signs of reinforcement corrosion. Recent advances in the development of anodes make it practical to use zinc galvanic cathodic protection to protect this structure in this area. Five anode systems were tested on several samples as, (1) zinc metal spray applied by arc-spraying on the concrete, (2) a zinc foil with conductive adhesive backing, (3) a system of zinc mesh and grout jacket, (4) a system of zinc mesh and compression panels, and (5) a bulk zinc. These anodes are set up to comparison the effects of potential and current over the zinc galvanic cathodic protection during 4... 

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... 

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... 

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... 

Global collapse in earthquake engineering refers to the inability of a structural system to sustain gravity loads when subjected to seismic excitation. Dynamic instability phenomena in exist buildings have a key position and for this reason strict criteria in structural seismic assessing codes presented for avoiding this phenomena. At this study, dynamic instability of five designed concrete buildings with moment frame system, mixed up 3, 6, 9, 12 and 15 story building, are investigated. P-delta effects, deterioration in strength and stiffness and cyclic deterioration in structural components considered in this investigation. For modeling nonlinear behavior of elements, experimental results... 

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... 

The purpose of this paper is to estimate the stiffness and strength of damaged rectangular reinforced concrete shear walls after an earthquake using surface crack patterns. Assessing the damage severity of buildings after an earthquake is an important part of the emergency inspection operation of buildings. Expert inspectors tag buildings into two categories of safe or unsafe that are usually affected by subjective decisions, which may result in catastrophic events reported in previous earthquakes. In this research, an extensive database on the images of damaged rectangular reinforced concrete shear walls (RCSWs) is collected and used to develop predictive equations for updated stiffness and...