• Advances in concrete construction
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• 제8권3호
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• pp.165-172
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• 2019

Progressive collapse is one of the factors which if not predicted at the time of structure plan; its occurrence will lead to catastrophic damages. Through having a glance over important structures chronicles in the world, we will notice that the reason of their collapse is a minor damage in structure caused by an accident like a terrorist attack, smashing a vehicle, fire, gas explosion, construction flaws and its expanding. Progressive collapse includes expanding rudimentary rupture from one part to another which leads to total collapse of a structure or a major part it. This study examines the progressive collapse of a 5-story concrete building with three column eliminating scenarios, including the removal of the corner, side and middle columns with the ABAQUS software. Then the beams and the bottom of the concrete slab were reinforced by (reinforcement of carbon fiber reinforced polymer) FRP and then the structure was re-analyzed. The results of the analysis show that the reinforcement of carbon fiber reinforced polymer sheets is one of the effective ways to rehabilitate and reduce the progressive collapse in concrete structures.

• Coupled systems mechanics
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• 제6권3호
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• pp.335-349
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• 2017

To cope with the demand on giant and durable buildings, reinforcement of concrete is a practical problem being extensively investigated in the civil engineering field. Among various reinforcing techniques, fiber-reinforced concrete (FRC) has been proven to be an effective approach. In practice, such fibers include steel fibers, polyvinyl alcohol (PVA) fibers, polyacrylonitrile (PAN) carbon fibers and asbestos fibers, with the length scale ranging from centimeters to micrometers. When advancing such technique down to the nanoscale, it is noticed that carbon nanotubes (CNTs) are stronger than other fibers and can provide a better reinforcement to concrete. In the last decade, CNT-reinforced concrete attracts a lot of attentions in research. Despite high cost of CNTs at present, the growing availability of carbon materials might push the usage of CNTs into practice in the near future, making the reinforcement technique of great potential. A review of existing research works may constitute a conclusive reference and facilitate further developments. In reference to the recent experimental works, this paper reports some key evaluations on CNT-reinforced cementitious materials, covering FRC mechanism, CNT dispersion, CNT-cement structures, mechanical properties and fire safety. Emphasis is placed on the interplay between CNTs and calcium silicate hydrate (C-S-H) at the nanoscale. The relationship between the CNTs-cement structures and the mechanical enhancement, especially at a high-temperature condition, is discussed based on molecular dynamics simulations. After concluding remarks, challenges to improve the CNTs reinforcement technique are proposed.

• Computers and Concrete
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• 제21권1호
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• pp.95-102
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• 2018

Reinforced concrete corbel beams (span to depth ratio of a corbel is less than one) are designed with primary reinforcement bars to account for bending moment and with the secondary reinforcement placed parallel to the primary reinforcement (shear stirrups) to resist shear force. It is interesting to note that most of the available analytical procedures employ empirical formulas for the analysis of reinforced concrete corbels. In the present work, a generalized and a simple strut and tie models were employed for the analysis of reinforced corbel beams. The models were benchmarked against experimental results available in the literature. It was shown here that increase of shear stirrups increases the load carrying capacity of reinforced concrete corbel beams. The effect of horizontal load on the load carrying capacity of the corbel beams has also been examined in the present paper. It is observed from the strut and tie models that the resistance of the corbel beam subjected to combined horizontal and vertical load did not change with increase in shear stirrups if the failure of the corbel is limited by concrete crushing. In other words, the load carrying capacity was independent of the horizontal load when failure of the beam occurred due to concrete crushing.

• Structural Engineering and Mechanics
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• 제57권5호
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• pp.937-949
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• 2016

Fiber reinforced polymer (FRP) applications in the structural engineering field include concrete-FRP composite systems, where FRP components are either attached to or embedded into concrete structures to improve their structural performance. This paper presents the results of an analytical study conducted using finite element model (FEM) to simulate the behavior of three-points load beam reinforced with GFRP and/or steel bars. To calibrate the FEM, a small-scale experimental program was carried out using six reinforced concrete beams with $200{\times}200mm$ cross section and 1000 mm length cast and tested under three point bending load. The six beams were divided into three groups, each group contained two beams. The first group was a reference beams which was cast without any reinforcement, the second group concrete beams was reinforced using GFRP, and the third group concrete beams was reinforced with steel bars. Nonlinear finite element simulations were executed using ANSYS software package. The difference between the theoretical and experimental results of beams vertical deflection and beams crack shapes were within acceptable degree of accuracy. Parametric study using the calibrated model was carried out to evaluate two parameters (1) effect of number and position of longitudinal main bars on beam behavior; (2) performance of concrete beam with composite longitudinal reinforcement steel and GFRP bars.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.1109-1114
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• 2001

This paper describes an attempt to develop a new truss model for reinforced concrete beams failing in shear based on a rational behavioral model. The key idea incorporated with truss model is the internal force state factor which is able to express global state of internal force flow in cracked reinforced concrete beams subjected to shear and bending. A new truss model using internal force state factor may provide a comprehensive result of shear strength in reinforced concrete beams without web reinforcement.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.279-282
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• 2005

Experimental study is performed to investigate the variation of shear strength of reinforced concrete beams according to design parameters. The major parameters are loading condition, shear span-to-depth ratio, ratio of tensile longitudinal reinforcement, prestress and boundary rigidity.14 reinforced concrete beams without web reinforcement are tested under monotonic downward loading. The shear strength of the tested specimens were compared with the prediction by design code and Choi's method.

• Corrosion Science and Technology
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• 제4권5호
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• pp.171-177
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• 2005

A comprehensive framework for numerical simulation of time-dependent performance change of reinforced concrete (RC) structures subjected to chloride attack is presented in this paper. The system is composed of simplified computational models for transport of moisture and chloride ions in concrete pore structure and crack, corrosion of reinforcement in concrete and mechanical behavior of RC member with reinforcement corrosion. Service-life of RC structures under various conditions is calculated.

• KCI Concrete Journal
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• 제11권3호
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• pp.5-17
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• 1999

In recent years. the concept of the modified compression field theory (MCFT) was develped and applied to the analysis of reinforced concrete beams subjected to shear, moment, and axial load. Although too complex for regular use in the shear design or beams. the procedure has value in its ability to provide a rational method of anlysis and design for reinforced concrete members. The objective of this paper is to review the MCFT and apply it for the prediction of the response and shear strength of reinforced concrete beams A Parametric analysis was Performed on a reinforced T-section concrete beam to evaluate and compare the effects of concrete strength. longitudinal reinforcement ratio shear reinforcement ratio, and shear span to depth ratio in two different approaches the MCFT and the ACI code. The analytical study showed that the concrete contribution to shear strength by the MCFT was higher than the one by the ACI code in beams without stirrups, while it was lower with stirrups. On the other hand. shear reinforcement contribution predicted by the MCFT was much higher than the one by the ACI code. This is because the inclination angle of shear crack is much smaller than 45$^{\circ}$assumed in the ACI code.

• Structural Engineering and Mechanics
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• 제91권4호
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• pp.335-347
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• 2024

This paper presents the behavior of geopolymer concrete beams reinforced with glass fiber reinforced polymer (GFRP) bars. In the study, ordinary Portland cement concrete and geopolymer concrete beams having GFRP bars were prepared and tested under four-point loading. The load-deflection diagrams and load capacities of the tested beams were obtained. It was observed that the tested beams exhibited good ductility and significant deflection capacity. The results showed that increasing the tension GFRP reinforcement ratio caused enhancement in the strength capacity of geopolymer concrete beams. In addition, the tested beams were analyzed to obtain the load capacity and the load-deflection responses. The theoretical load-deflection curves and load bearing capacities have been predicted well with the test results. Parametric study has been performed to determine the influences of concrete strength, shear span to depth ratio (a/d) and reinforcement ratio on the behavior of geopolymer concrete beams longitudinally reinforced with GFRP bars. It was concluded that increasing concrete strength led to an increase in load capacity. Besides, the ultimate load increased as the reinforcement ratio increased. On the other hand, increasing a/d ratio reduced the ultimate load value of GFRP reinforced geopolymer concrete beams.

• Corrosion Science and Technology
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• 제6권6호
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• pp.297-303
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• 2007

This paper discusses the chloride-induced corrosion of reinforcement in marine concrete structures focusing on the variability in the progress of deterioration. Through tests and analyses of reinforced concrete slabs taken out from existing open-pile structures that have been in service for 30 to 40 years, the following topics were particularly discussed: variation in chloride ion profiles of concrete, variation in corrosion properties of reinforcement embedded in concrete, and influence of the reinforcement corrosion on the load-carrying capacity of the concrete slabs. As a result, their variability was found to be very large even in one reinforced concrete slab with almost the same conditions. It was also discussed how to determine the calculation parameters for prediction of decreasing in load-carrying capacity of concrete members with chloride-induced corrosion of reinforcement.