• Computers and Concrete
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• v.27 no.1
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• pp.13-20
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• 2021

In this paper, the elevated temperature on a concrete-galvalume composite beam's flexural strength based on the numerical and experimental methods is investigated. The strategy is to perform modeling and simulation of the flexural test based on finite element method (FEM) at room temperature and validate its results to experimental data at the same temperature. When the numerical model was proven valid, the model was utilized to simulate the effect of elevated temperatures on the composite element. The study concludes that the flexural strength of the beam decreases at higher temperature. Additionally, it was shown that cracking moments is susceptible to temperature fluctuation and the failure modes are sensitive concerning the elevated temperature.

• Composites Research
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• v.29 no.2
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• pp.45-52
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• 2016

An understanding of the failure mechanisms of the adhesive layer is decisive in interpreting the performance of a particular adhesive joint because the delamination is one of the most common failure modes of the laminated composites such as the fiber metal laminates. The interface between different materials, which is the case between the metal and the composite layers in this study, can be loaded through a combination of fracture modes. All loads can be decomposed into peel stresses, perpendicular to the interface, and two in-plane shear stresses, leading to three basic fracture mode I, II and III. To determine the load causing the delamination growth, the energy release rate should be identified in corresponding criterion involving the critical energy release rate ($G_C$) of the material. The critical energy release rate based on these three modes will be $G_{IC}$, $G_{IIC}$ and $G_{IIIC}$. In this study, to evaluate the fracture behaviors in the fracture mode I and II of the adhesive layer in fiber metal laminates, the double cantilever beam and the end-notched flexure tests were performed using the reference adhesive joints. Furthermore, it is confirmed that the experimental results of the adhesive fracture toughness can be applied by the comparison with the finite element analysis using cohesive zone model.

• Journal of the Korea institute for structural maintenance and inspection
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• v.4 no.3
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• pp.197-204
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• 2000

Tensile strength (stress) of bar splice is important in the research of mechanical behavior of reinforced concrete structures-beam, column etc.- with bar splice. The purpose of this research is to evaluate the flexural behavior - deflection of beam specimens, strain of main bars - of reinforced concrete beam with Lock Joint Coupler. To make a comparative research, reinforced concrete beam specimens with normal deformed bar and lap splice are tested and analyzed. Test results, Comparing a deflection of three types flexural specimens, a flexural specimen with Lock Joint Coupler is 40% greater than the other flexural specimens. At the center of flexural specimen, the strain of main bar(D29) with lock joint coupler is 50% less, and vice versa, at the point of 14cm far from the center of flexural specimen, the strain of main bar(D29) with lock joint coupler is 9% larger than the strain of main bar(D29) which calculated using the classical flexure theory. A discords, between a deflection behavior of the flexural specimens and a strain of the main bar, are caused by the difference of strain between the lock joint coupler and main bar, near the lock joint coupler. So, additional research is need to verify as stated above discords.

• Earthquakes and Structures
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• v.17 no.4
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• pp.337-354
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• 2019

This paper presents the results of experimental and numerical studies conducted to investigate the behavior of exterior reinforced concrete beam column joints (BCJ) strengthened by using carbon fiber reinforced polymer (CFRP) sheets. Twelve reinforced concrete beam-column joints (BCJ) were tested in an experimental program by simulating the joints in seismically deficient old buildings. One group of BCJs was designed to fail in flexure at the BCJ interface, and the second group was designed to ensure joint shear failure. One specimen in each set was -retrofitted with CFRP sheet wrapped diagonally around the joint. The specimens were subjected to both monotonic and cyclic loading up to failure. 3D finite element simulation of the BCJs tested in the experimental program was carried out using the software ABAQUS, adopting the damage plasticity model (CDP) for concrete. The experimental results showed that retrofitting of the shear deficient, BCJs by CFRP sheets enhanced the strength and ductility and the failure mode changed from shear failure in the joints to the desired flexural failure in the beam segment. The FE simulation of BCJs showed a good agreement with the experimental results, which indicated that the CDP model could be used to model the problems of the monotonic and cyclic loading of beam-column reinforced concrete joints.

• Steel and Composite Structures
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• v.45 no.2
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• pp.193-204
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• 2022

The need for establishing the contribution of pultruded FRP encasements and additional FRP wraps around these encasements to the shear strength and load-deflection behavior of reinforced concrete beams is the main motivation of the present study. This paper primarily focuses on the effect of additional wrapping around the composite beam on the flexural and shear behavior of the pultruded GFRP (Glass Fiber Reinforced Polymer) beams infilled with reinforced concrete, taking into account different types of failure according to av/H ratio (arch action, shear-tension, shear-compression and pure bending). For this purpose, nine hybrid beams with variable shear span-to-depth ratio (av/H) were tested. Hybrid beams with 500 mm, 1000 mm, and 1500 mm lengths and cross-sections of 150x100 mm and 100x100 mm were tested under three-point and four-point loading. Based on the testing load-displacement relationship, ductility ratio, energy dissipation capacity of the beams were evaluated with comprehensive macro damage analysis on pultruded GFRP profile and GFRP wrapping. The GFRP wraps were established to have a major contribution to the composite beam ductility (90-125%) and strength (40-75%) in all ranges of beam behavior (shear-dominated or dominated by the coupling of shear and flexure). The composite beams with wraps were showns to reach ductilities and strength values of their counterparts with much greater beam depth.

• The Korean Journal of Ceramics
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• v.4 no.4
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• pp.311-322
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• 1998

American Society for Testing and Materials (ASTM) standard test method PS 070-97 has been created for measuring fracture toughness of advanced ceramics. PS 070-97 includes three test methods which use beams in bending: chevron notch (CNB), single-edged precracked beam (SEPB), and surface crack in flexure (SCF). Supporting data has been collected through several Versailles Advanced Materials and Standards round robins. This paper discusses the evolution of the standard including the rationale for the choice of the three methods and the specifications in the standard. Progress on Standard Reference material 2100 which will have certified values of fracture toughness is presented.

• Structural Engineering and Mechanics
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• v.62 no.6
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• pp.759-769
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• 2017

The effect of central axial load on natural frequencies of various thin-walled beams, are investigated by some researchers using different methods such as finite element, transfer matrix and dynamic stiffness matrix methods. However, there are situations that the load will be off centre. This type of loading is called eccentric load. The effect of the eccentricity of axial load on the natural frequencies of asymmetric thin-walled beams is a subject that has not been investigated so far. In this paper, the mentioned effect is studied using exact dynamic stiffness matrix method. Flexure and torsion of the aforesaid thin-walled beam is based on the Bernoulli-Euler and Vlasov theories, respectively. Therefore, the intended thin-walled beam has flexural rigidity, saint-venant torsional rigidity and warping rigidity. In this paper, the Hamilton‟s principle is used for deriving governing partial differential equations of motion and force boundary conditions. Throughout the process, the uniform distribution of mass in the member is accounted for exactly and thus necessitates the solution of a transcendental eigenvalue problem. This is accomplished using the Wittrick-Williams algorithm. Finally, in order to verify the accuracy of the presented theory, the numerical solutions are given and compared with the results that are available in the literature and finite element solutions using ABAQUS software.

• Structural Engineering and Mechanics
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• v.20 no.6
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• pp.695-712
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• 2005

Hybrid coupled shear walls in tall buildings are known as efficient structural systems to provide lateral resistance to wind and seismic loads. Multiple hybrid coupled shear walls throughout a tall building should be joined to provide additional coupling action to resist overturning moments caused by the lateral loading. This can be done using a coupling beam which connects two shear walls. In this study, experimental studies on the hybrid coupled shear wall were carried out. The main test variables were the ratios of coupling beam strength to connection strength. Finally, this paper provides background for rational design guidelines that include a design model to behave efficiently hybrid coupled shear walls.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.733-738
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• 2001

Although there are strong needs for evaluating statistical characteristics of strengthened reinforced concrete beams under flexure, many researches have been performed mostly on the mechanical properties and failure mechanisms. Different material properties and resulting reinforcing effect could alter the probabilistic values of the strengthened beams. Existing equations suggested for predicting flexural strengthened reinforced concrete beam with CFRP and steel plate are selected and best-fitting one is used in evaluating probability of failure based on Monte-Carlo method. Influential factors are statistically examined and approximate strength reduction factors are suggested. It was found that the factor is more sensitively influenced by predictive equations as well as characteristics and amounts of strengthening materials.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.259-264
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• 2002

This paper describes an attempt to develop a unified design approach for reinforced concrete short beam failing in shear based on a Arch Factor. Designing for short beam in shear is not as straightforward as designing for flexure due to the complicated interdependency of the variables involved and to the nonexistence of a rational theory tn current design code. Shear failure of reinforced concrete beams with stirrups is influenced greatly because of the actual geometrical shape(a/d) of the concrete and flexural reinforcement steel ratio, stirrup reinforcement ratio and concrete compression strength, size effect etc. The objective of this paper is to present a pilot study to develop a simplified physical model for estimating shear behavior of reinforced concrete short beams. The Key idea incorporated with this model is the Arch factor, introduced by Kim and White.