• 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.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.04a
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• pp.393-398
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• 1999

The main objective of this project is to define the ultimate bond performance of domestic prestressing strands in the precast prestensioned concrete beams. Eight specimens from four different companies were fabricated and tested in this study. Four-point loading tests were performed on the beams of domestic strands with an arbitrary anchorage length. The research has shown, that all seven specimens except one failed in bond are capable of developing their full flexural capacity and the strands within them are fully anchored even with the sudden transfer of frame cutting. Following results are summarized from the tests conducted. 1) All of the specimens are tested at an embedment lengths much shorter than those required by the ACI code, failed in flexure except one failed in bond. 2) It seems that the beam depth can not be an effective variable to estimate the bond length within these sections and length of specimens on this tests. 3) The development length with the stirrup space which are considered for correction factors in the equations of Russel and Paulsgrove, is fully accurate to determine the required length for the beam tested in this research.

• Computers and Concrete
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• v.13 no.2
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• pp.235-253
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• 2014

The theoretical basis and the main results of a design procedure, which attempts to provide the optimal layout of ordinary reinforcement in prestressed concrete beams, subjected to bending moment and shear force are presented. The difficulties encountered in simulating the actual behaviour of prestressed concrete beam in presence of coupled forces bending moment - shear force are discussed; particular emphasis is put on plastic models and stress fields approaches. A unified model for reinforced and prestressed concrete beams under axial force - bending moment - shear force interaction is provided. This analytical model is validated against both experimental results collected in literature and nonlinear numerical analyses. Finally, for illustrating the applicability of the proposed procedure, an example of design for a full-scale prestressed concrete beam is shown.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.2
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• pp.269-276
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• 2017

In order to study ultimate flexure behavior of FRP-concrete composite structures which can replace reinforced concrete structures, ABAQUS, a general purpose analysis program, was utilized for numerical nonlinear analysis of structural performance and behavior characteristics of FRP-concrete composite beams. Explicit nonlinear finite element analysis was conducted and the numerical results were compared with previous experiments. Concrete damaged plasticity model was adopted as material properties of concrete and Euro code was used as compressive stress state. Nonlinear analysis was performed for four different types of FRP-concrete composite beams, and ultimate load and cracking pattern was compared and analyzed. The model suggested in this research was able to simulate ultimate load and cracking pattern properly, it is expected to be utilized in study of precise structural and behavioral characteristics of various FRP-concrete composite structures.

• Composites Research
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• v.29 no.5
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• pp.249-255
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• 2016

The fiber metal laminates have been widely used at aerospace industry due to outstanding fatigue characteristic, corrosion resistance and impact resistance and so forth. The objective of this research is to establish the proper manufacturing variables for enhancing the interfacial energy release rate of fiber metal laminates using Taguchi method. The major variables of the manufacturing process are surface treatment, pre-specified temperature holding time and additional pressure. In order to determine the interfacial adhesive strength, the double cantilever beam and end-notched flexure tests were conducted. Afterward, Mode I and II energy release rates at various conditions were introduced signal-to-noise ratio with respect to each condition. Finally, the most efficient manufacturing variables are recognized using larger-the-better characteristic.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.22 no.6
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• pp.519-525
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• 2009

In this study a cohesive zone model was used to simulate the delamination phenomena which occurs by a successive crack initiation and propagation in composite laminates. The cohesive zone model was incorporated to the classical finite element method via cohesive element formulation and then implemented into the user-subroutine UEL of a commercial finite element program Abaqus. To validate the formulation and implementation of the cohesive element the finite element results were compared with the experimental data of double cantilever beam and end notched flexure tests. The numerical results well agree with the experimental load-displacement curves. Also the effect of the elastic stiffness and the size of the cohesive element on the global load-displacement curves were studied numerically. To minimize the mesh-dependency of the crack propagation path and eliminate the zig-zag patterns in the load-displacement curve, cohesive elements should be refined at the crack-tip.

• Journal of Wind Energy
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• v.14 no.3
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• pp.83-90
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• 2023

The purpose of this study is to evaluate the inter-laminar fracture toughness characteristics of CFRP pultrusion spar cap materials reinforced with non-woven glass fabric. Test specimens were fabricated by the infusion technique. A non-woven glass fabric and artificial defects were embedded on the middle surface between two pultruded CFRP panels. Double cantilever beam (DCB) and End Notched Flexure (ENF) tests were performed according to ASTM standards. Fracture toughness and crack propagation characteristics were evaluated with load-displacement curves and delamination resistance curves (R-Curve). The fracture toughness results were calculated by compliance calibration (CC) method. The initiation and propagation values of Mode-I critical strain energy release rate value G_Ic were 1.357 kJ/m2 and 1.397 kJ/m2, respectively, and Mode-II critical strain energy release rate values G_IIc were 4.053 kJ/m2 for non-precracked test and 4.547 kJ/m2 for precracked test. It was found that the fracture toughness properties of the CFRP pultrusion spar-cap are influenced by the interface between the layers of CFRP and glass fiber non-woven.

• Journal of the Korean Society of Industry Convergence
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• v.12 no.2
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• pp.107-112
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• 2009

The effective reinforcement methods of structure is required to improve the durability of existing structures. Recently, the continuous fiber sheets to the concrete structures are widely used in the earthquake-proof reinforcement method. This study examines suitability and effect to concrete structure of fiber by FEM analysis. The result of analysis is as follows; All specimens occurred bending tensile failure at the middle span. Ultimate strength of specimen in the RC and reinforced RC specimen were 53.9 kN, 56.3 kN respectively and it was some low by degree 0.89, 0.82 to compare with calculated result. The deflection of specimen at the middle span occurred in approximately 0.2 mm, and did linear behavior in load 20 kN by seat reinforcement. Stiffness did not decrease by occurrence in the finer crack and reinforcement beam's flexure stiffness was increased until reach in failure. To compare calculated value and analysis value, it almost equal behavior in the elastic reign and can confirm effectiveness of analysis. Crack was distributed uniformly by reinforcement of fiber seat at failure and it do not occurred stiffness decreases.

• Steel and Composite Structures
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• v.19 no.3
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• pp.615-633
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• 2015

Composite steel-concrete beams are used frequently in situations where axial forces are introduced. Some examples include the use in cable-stayed bridges or inclined members in stadia and bridge approach spans. In these situations, the beam may be subjected to any combination of flexure and axial load. However, modern steel and composite construction codes currently do not address the effects of these combined actions. This study presents an analysis of composite beams subjected to combined loadings. An analytical model is developed based on a cross-sectional analysis method using a strategy of successive iterations. Results derived from the model show an excellent agreement with existing experimental results. A parametric study is conducted to investigate the effect of axial load on the flexural strength of composite beams. The parametric study is then extended to a number of section sizes and employs various degrees of shear connection. Design models are proposed for estimating the flexural strength of an axially loaded member with full and partial shear connection.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.126-129
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• 2010

MEMS(micro electro-mechanical systems) inertial switch which is applicable to the ignition Safe-Arm- Unit of propulsion system is devised. The MEMS inertial switch is designed according to the general design procedure for conventional mechanical elements. Unlikely conventional MEMS accelerometer, threshold inertial switching mechanism is adopted which makes a MEMS element an abrupt switching in a certain acceleration level. By comparing the design data and test results of the specimen a small discrepancy in switching acceleration level is found which is presumably due to the nonlinear characteristics of the beam spring and the flexure hinge which are the main parts of the MEMS inertial switch.