Investigating the behavior of reinforced concrete shear wall reinforced with FRP using the finite element method

Dissertation for Master's Degree in Civil Engineering, Structural Orientation

Abstract:

This thesis is the results of a numerical and parametric study on the effect of reinforcing reinforced concrete shear wall with FRP composite and applying the results of the finite element method. The finite element program is compared and calibrated against experimental data. Then the numerical results are introduced and used to evaluate the capacity, which is used with the help of non-linear load-displacement curves of reinforced concrete shear walls. Also, this program can be used to evaluate the entire load-displacement curve, including the elastic part, the formation of shear cracks, the occurrence of cracking, and the crushing of concrete. For the local strengthening of the shear wall, it is possible to connect metal plates or FRP composite fibers to the top or bottom of the shear wall or in different directions to increase the stiffness before cracking, the cracking load, and the ultimate bending capacity of reinforced concrete shear walls. Carbon fiber plates can be used. The carbon fiber plates that are wrapped around the plastic joint area of ??the reinforced concrete wall, in addition to providing sufficient shear strength, provide the confinement of the concrete in the plastic area, which increases the plasticity of the reinforced concrete wall.

In this thesis, a test program has been used to review retrofitting projects and plans in order to increase the shear strength and plasticity of the walls. It should be noted that an innovative experiment was used to increase the probability of controlling the ratio of cutting force to bending moment and axial load. In this study, a sample of a wall called the control wall [1], which was designed according to pre-seismic construction rules [2], was tested and the non-deformable shear failure mechanism [3] was shown. In two other retrofit projects, FRPs [4] were used in order to increase the strength and ductility of the wall. The obtained results have shown that the implemented retrofitting plans have been completely successful in preventing shear failure and increasing the strength of the wall. For investigation, nonlinear finite element analysis [5] of experimental walls using Solid65, which is an eight-node volume element, was used to model concrete. Layered volume element, Solid46, is used for FRP modeling. Solid46 is a layered model of eight-node structural volume to model the shell or layered volume. The predicted failure loads and even the shear and strain distributions are consistent with the obtained experimental results. In this research, another analytical model based on the pressure field theory [6] and another model for reinforcing reinforced concrete walls using FRPs have been presented. Analytical model has also been used for detailed analysis of the types of walls that were constructed using resistant FRP and it was found that this model was successful in predicting the displacement, ultimate load and mode or type of failure. In the end, a parametric study was carried out in order to evaluate the effect and consequences of various parameters on the effectiveness of the design and the retrofitting project.

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Chapter 1

-1-Motivation and Objective

Experiences obtained from the past have shown that reinforced concrete walls are effective and efficient against side loads. But in some cases, these walls may face serious or minor damage and danger during an event such as an earthquake, as reported by researchers such as Fintel [1] (1995), Erdrik [2] and his colleagues (2003), Satchioglou [3] and his colleagues (2001), Sezen [4] and his colleagues (2003) and Berzo [5] (2004). Figures 1-1 to 1-6 show shear faults in the last 3 earthquakes. This type of failure is common in long and medium flexural walls and they are characterized by inclined cracks[6] of 45 degrees. Long concrete walls need to be strengthened and renovated in the states of failure and breakage. Reinforcement of the wall may be in order to maintain forces. Renovation means repairing an earthquake-damaged wall to restore its original strength and resistance or stiffness. The use of FRP composites in the repair and renovation of structures is known as a new technique. This type of material is characterized by high resistance to weight ratio. The use of these types of materials, especially in the renovation and retrofitting of buildings and especially in the construction industry, play an important role.In this analytical program, the strengthening of structural walls against seismic lateral loads, using FRP composites, has been investigated. Chapter 1 includes an introduction that covers the objectives and scope of the study. Chapter 2 presents a general review of experimental research on wall improvement, an analytical review of wall modeling and structural wall design methods. Chapter 3 shows the details related to the test program, test setup and structure, design and construction of various wall specimens. Chapter 4 is the experimental program and modeling and design of samples. Chapter 5 presents the results of the experimental program and includes discussion and comparison. Chapter 6 explains the finite element model that was used to analyze the samples. Chapter 7 describes the analytical model that was used to analyze samples and some test samples [7]. Chapter 8 presents a summary of the research, the main results and points for future research. Chapter Two: General Review: 1-2 Structural Walls: In the following section, a definition of reinforced concrete structural walls, their different types, their behavior, failure modes, loads, and research. Analysis and tests carried out regarding structural walls as well as their repair and retrofitting have been presented. 1-1-2- Definitions Concrete walls are vertical diaphragms that are basically used for strengthening against lateral loads in the structure. 2-1-2 Types of structural walls Structural walls according to the aspect ratio [1] wall (ratio of height to length) are classified into two groups.

1- High walls [2]

These types of walls are characterized by a high ratio of height to length. In this type of walls, the main component of deformation is bending deformation, but it should be said that shear deformation is small compared to it. This type of walls is used in tall and medium-sized buildings. In 1999, Bachmann conducted a comprehensive research program on high structural wall systems. He performed cyclic, dynamic and quasi-dynamic tests on samples of walls (large-scale walls) and reported different modes of failure and rupture, and finally compared the results of different tests. Deformation of cutting leads to a large percentage of deformation. In this type of walls, flexural failure is unlikely. This type of walls in buildings such as schools, shopping centers, etc. are used It should be noted that reinforced concrete walls are used in these buildings in order to resist lateral loads. Such walls are also used in nuclear reactors. Doostadr in 1994 investigated the properties subject to inelastic deformation as well as the resistance or strength of the mentioned walls. He even conducted experiments on walls with aspect ratios of 0.75 and 0.1. Deformation components depend on shear and bending, which are equally included in such walls and make up almost 80% of the total deformation. Palermo's 1998 experiment on short winged walls[4] was subjected to static cyclic loading, which concluded that these walls produce hysteresis curves[5] with low energy dissipation, compared to long shear walls. The dividing line between the two types of walls is not so obvious.

3-1-2-Loads

Reinforced concrete walls are referred to three types of loads called lateral loads in the plane [6], vertical loads [7] and out-of-plane loads [8]. Strengthening these loads is the main role and issue of structural walls. Unlike gravity loads, these loads differ in terms of magnitude and direction and should be considered in analysis and design. A large part of the research related to the structural walls is devoted to the investigation of this type of loads. 2- Vertical loads Although the reinforcement of lateral loads plays the main role in the wall, but next to it are vertical gravity loads. This load affects the behavior of long structural walls and should be considered in any investigation related to the analysis and design of walls.