Investigating nonlinear analysis and numerical modeling of reinforced concrete deep beam with opening reinforced with FRP by finite element software

Master's Thesis in Civil Engineering, Structural Orientation

Abstract

In this study, the evaluation and comparison of nonlinear and numerical analysis of deep reinforced concrete beams with openings without reinforcement with deep concrete beams with openings reinforced with FRP sheets and deep reinforced concrete beams without openings by Abaqus finite element software has been done. Using the nonlinear finite element method, 9 samples of deep beams with simple supports under concentrated load have been modeled and the effectiveness of FRP sheets on the ultimate strength of reinforced concrete deep beams with openings has been studied. For this purpose, a sample of deep reinforced concrete beam without opening was used as a reference beam and 4 deep reinforced concrete beams with openings (circular and square) without reinforcement and 4 samples of deep reinforced concrete beams with openings (circular and square) reinforced with FRP sheets were used. 

Strengthening by FRP sheets, around the openings, has been very effective in increasing the capacity of deep reinforced concrete beams. The finite element modeling of the samples has been done using the Abaqus finite element software. Keywords: deep beam, reinforced concrete, opening, finite elements, FRP, nonlinear analysis. Chapter 1 Introduction Iran is located in the seismically active region of the world, and according to scientific documentary information and recent observations, it is considered one of the most dangerous regions in the world. In this regard, one of the plans of the government and people to reduce the vulnerability of the country against earthquakes is the study and implementation of retrofitting of important government buildings, infrastructure facilities and vital arteries of the country. Success in seismic retrofitting as a part of seismic retrofitting depends on the use of modern retrofitting techniques and skills. Among these innovations, polymer-reinforced fibers [1] have a special place. Meanwhile, deep reinforced concrete beams have been widely used in high-rise buildings, tanks, rectangular silos, floor diaphragms, shear walls, transfer slabs and beams in marine structures and foundations, walls of underground shelters and hempenin in load-bearing walls of buildings, etc. The existence of many openings in such beams is required to create access such as doors and windows or to pass the main facilities such as ventilation pipes, water, electricity, sewage, cooler, etc.

On the other hand, the behavior of reinforced concrete structural members during loading is very important to improve the safety and efficiency of the structure. Various methods have been used to obtain the response of structural members. Laboratory studies have been widely used as a method to analyze structural elements. Although this method gives results that are more realistic, it is very time-consuming and expensive. Using finite element analysis method to study structural members is another method that is used today. In the past, preliminary studies in this field were time-consuming due to poor hardware and software facilities. However, in recent years, the use of finite element analysis [2] has increased due to the advancement of knowledge and increased hardware and software capacity. Using computer software to model these elements is much more cost-effective and faster.

The data obtained from a finite element analysis will not be useful unless steps are taken to understand what is going on inside the model created by the software. Also, the necessary controls must be performed at key points to ensure the output of the software. Some reinforced concrete beams are taller than usual in relation to their opening. In these beams, external forces and support reactions are located in the plane of the member, and a state of plane stress is created in the concrete, such beams are called deep beams.

The design of these beams is not sufficiently covered by national regulations; For example, the current British code B 8110 explicitly states that "specialist publications should be consulted for the design of deep beams." Important codes that have discussed deep beams to some extent include the ACI Code and CIRIA Guide 2, although CIRIA Guide No. 2 provides more comprehensive information and similarly the draft Eurocod EC/2 states "this code does not apply to deep beams".. The important design codes are: ACI code (USA), CAN-A23.3-M84 code (Canada) and CIRIA GUIDE 2 code. Of these, only CIRIA GUIDE 2 has relatively comprehensive recommendations. and computer, mechanical installations or even commuting from one room to another, open openings in deep reinforced concrete beams.

Factors affecting the behavior of deep reinforced concrete beams with openings [4]

Span to depth ratio

beam cross-section (rectangular, T-shaped, etc.)

Amount and location of longitudinal reinforcement

Amount and type of life reinforcement

Properties of concrete and steel

Ratio of net shear opening to beam depth

Type of load and its location

Size, shape, opening location, etc.

(Images are available in the main file)

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Deep reinforced concrete beams are usually used in high-rise buildings, marine structures. and coastal, transmission beams, some walls and pillars are used. Existence of openings in the beam in some deep beams due to access such as doors and windows, or due to architectural and installation requirements, or due to changes in the use of the building is inevitable, which reduces the capacity of the member, so some safe solutions should be provided for the risk of such weakness. To date, limited studies on the behavior and strength of deep reinforced concrete beams with openings have been reported in the literature. The result obtained from these studies is that the existence of the opening significantly reduces the strength of the reinforced concrete deep beam. In cases where the presence of such openings is unavoidable, suitable solutions should be provided to strengthen the beam and compensate for the decrease in strength. There are various methods for repairing and strengthening deep beams, the use of composite polymer fibers known as FRP in strengthening ordinary reinforced concrete beams has been widely investigated by researchers, and the results of this research have shown the significant effect of using FRP sheets in increasing the strength of reinforced concrete beams. Despite extensive research in the field of reinforced concrete shallow beams, few research activities have been done on the strengthening of deep reinforced concrete beams. In this regard, various theories of researchers have been expressed regarding the effect or lack of effect of FRP sheets in increasing the ultimate strength of deep beams.

1-4-

The purpose of this study is to investigate the nonlinear and numerical analysis of reinforced concrete deep beams with opening reinforced by CFRP. In this study, the one-point bending test has been modeled and studied, and the powerful Abaqus finite element software has been used for accurate numerical modeling and study.

In this research, after examining the types of linear and nonlinear analysis and determining the strengths and weaknesses of each of the analysis methods, advanced methods of nonlinear static analysis are examined.

In this research, using the nonlinear finite element method, 9 samples of deep beams with support Simple beams under concentrated load, modeling and effectiveness of CFRP on ultimate strength of deep reinforced concrete beams with opening have been studied. For this purpose, one sample of reinforced concrete deep beam without opening was used as a reference beam, 4 deep reinforced concrete beams with circular and square openings without reinforcement and 4 samples of reinforced concrete deep beams with circular and square openings reinforced with CFRP sheets in the form of a U-turn were used. In this study, samples with openings are loaded to the point of failure and the effect of increasing strength in deep beams with openings that are reinforced by CFRP is investigated.

In these samples, a steel plate with dimensions of 10x50x150 mm is used at the top of the sample and two steel plates with dimensions of 10x50x150 are used at the two lower ends of the sample.

The next objective in chapter 2 It is mentioned that the behavior of these samples is investigated. In chapter 3, first, the control beam corresponding to the tested beam of Mohammad Panahi et al. [4] is made in the relevant software package, and the results are analyzed and compared with the test; To determine how well the software's prediction of the behavior of this beam matches the result of the laboratory sample