• Steel and Composite Structures
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• v.20 no.3
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• pp.487-500
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• 2016

In order to investigate the flexural bearing capacity of panel zone of diaphragm-through joint between concrete filled square steel tubular column and steel beam, four specimens were tested under static tension loads to study the mechanical properties and bearing capacity of diaphragm-through joints with a failure mode of panel zone. Finite element models of these specimens were developed to simulate the test and compare the predicted failure modes, load-displacement curves and bearing capacities with the experimentally observed. It was found that the tensile load from the steel beam flange is mainly shared by the square steel tube and the diaphragm. The diaphragm plastic zone appears along the cross-section lines enclosed by the square steel tube and the influence of steel beam web on the plastic zone of the steel tube is significant and cannot be neglected. Computational models of yield lines on square steel tube and diaphragm are established based on the distribution pattern of the plastic zone, and an analytical method for the evaluation of the bearing capacity of the joint is proposed. The theoretical results and the experimental data are compared and found in good agreement.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.6
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• pp.89-96
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• 2008

The purpose of this study is to investigate the flexural strengthening effectiveness for the beams reinforced with NSM CFRP strips. To accomplish this objective, concrete T beams were made and tested. From this study, it is found that the flexural stiffness and strength of the beams reinforced with NSM strips were significantly improved compared to the beams without CFRP strip. The maximum increase of flexural strength was 247%. Failure of the beam reinforced with NSM was initiated by a part of separation of NSM strips along the longitudinal direction, and the second failure of strips was investigated. After the first rupture of the NSM strips, the load dropped suddenly and the second rupture was succeeded. This result shows that a perfect composite reaction with NSM strips and concrete is possible in the beam reinforced with NSM CFRP strips the NSM strips and Near surface mounted(NSM) is one of the most recent and promising strengthening techniques for reinforced concrete structures.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.520-523
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• 2004

The finite element method(FEM) models were developed for the reinforced concrete flexural walls and analysed under constant axial and monotonic lateral load using ABAQUS. The major objective of the present study is to determine if the ABAQUS finite element program can be used to accurately model the post-cracked mode of failure in plastic regions of walls, and, if so, to develop practical failure criteria in the plastic range of the material response. The research comprises constitutive models to represent behavior of the materials that compose a wall on the basis of experimental data, development of techniques that are appropriate for analysis of reinforced concrete structures, verification, and calibration of the global model for reinforced concrete walls of increasing complexity. Results from the analyses of these FEM models offers significant insight into the flexural behavior of benchmark data.

• 한국공간정보시스템학회:학술대회논문집
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• 2004.05a
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• pp.206-211
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• 2004

This paper deals with the flexural strengthening of reinforced concrete beams by means of thin fiber reinforced plastic(FRP) laminas. This study focuses on modeling of structural of concrete bonded FRP laminate in flexural bending members. Used computational equation is derived by relation of stress and strain. The section analysis is based on experimental observations of a linear strain distribution in the cross section until failure, and a multi-linear moment-deflection curve that is divided into four regions, each terminated by a similarly numbered point. The load-deflection relationship in each region is assumed to be linear. The present model is validated to compare wit the experiment of 4-point bending tests of R/C rectangular beams strengthened with CFRP laminates, and has well predicted the moment-displacement relationships of members.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.19 no.4 s.74
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• pp.325-335
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• 2006

In this paper, flexural test, girder-connection test and barrier-connection test for the pultruded composite bridge deck of hollow section, were carried out and its structural characteristics were evaluated. In the flexural test specimen, deflection was measured at center of the span and strains were measured at various locations to see the structural behavior up to the failure. In addition, finite element analysis was performed for the flexural test specimen and the results were compared with experiments, and load carrying capacity was evaluated. Also, field load test was conducted for the demonstration plate girder bridge and other field applications were described.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.751-756
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• 2001

This paper deals with the experimental evaluation of the performance of R.C beams strengthened with aramid, glass and carbon fiber sheets. To evaluate the effects of FRPs on the flexural strengthening of the beams, strengthening ratio is adopted as a main variable. Seven beams were fabricated and strengthened under same tensile strength based on ultimate strength of FRPs and strengthening length. Deflection, flexural stiffness, strain of FRP, ultimate load and failure load are compared to evaluate the effects of FRPs on structural behavior of retrofitted beams. The results shows that little effects of FRPs on behavior of strengthened beams can be estimated and the fail modes are more influenced on structural behavior than that.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.2
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• pp.227-234
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• 2010

To investigate the flexural behavior of RC beams strengthened with carbon fiber sheets, 1 control beam and 8 strengthened beams(4 NU-beams without U-shaped band and 4 U-beams with U-shaped band) are tested. The variables of experiment are composed of the number of carbon fiber sheets and the existence of U-shaped band, etc. The experimental results showed that the strengthening system with U-shaped band controls the premature debonding and provides a more ductile failure mode than the strengthening system without U-shaped band. It can be found from the load-deflection curves that as the number of fiber sheets is increased, the maximum strength and the flexural rigidity is increased. The experimental results are compared with the analytical results of nonlinear flexural behaviors for strengthened RC beam. The proposed analytical method for strengthened beams is proved to be accurate by an experimental investigation of load-deflection curve, yield load, maximum load, and flexural rigidities in the pre- and post-yielding stages.

• Structural Engineering and Mechanics
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• v.81 no.5
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• pp.539-550
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• 2022

A detailed experimental program was conducted to investigate the flexural behavior of ultra high performance concrete (UHPC) beams reinforced with high strength steel (HSS) rebars with a specified yield strength of 600 MPa via direct tensile test and monotonic four-point bending test. First, two sets of direct tensile test specimens, with the same reinforcement ratio but different yield strength of reinforcement, were fabricated and tested. Subsequently, six simply supported beams, including two plain UHPC beams and four reinforced UHPC beams, were prepared and tested under four-point bending load. The results showed that the balanced-reinforced UHPC beams reinforced with HSS rebars could improve the ultimate load-bearing capacity, deformation capacity, ductility properties, etc. more effectively owing to interaction between high strength of HSS rebar and strain-hardening characteristic of UHPC. In addition, the UHPC with steel rebars kept strain compatibility prior to the yielding of the steel rebar, further satisfied the plane-section assumption. Most importantly, the crack pattern of the UHPC beam reinforced with HSS rebars was prone to transform from single main crack failure corresponding to the normal-strength steel, to multiple main cracks failure under the condition of balanced-reinforced failure, which validated by the conclusion of direct tensile tests cooperated with acoustic emission (AE) source locating technique as well.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.331-336
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• 1994

This paper presents comprehensive test data on the effect of Epoxy-Bonded Steel Plates on the ultimate strengths, ductilities, failure modes and structural deformations of flexural members strengthened with steel plates on the tension face. To achieve the purpose, six specimens with and without Epoxy-Bonded steel Plates were tested. The results show that Epoxy-Bonded Steel Plate is very effective for strengthening the damaged structure, That is, plated members have enhanced ultimate strength at all load levels until failure. However, the failure mode of plated members is brittle as soon as steel plate separates from concrete face.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.543-548
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• 2003

In this study, a numerical model is developed using axial deformation link elements that can effectively predict the failure behavior of RC type structures. Using this mod 1, numerical analysis was performed to investigate the strengthening effect and failure behavior of structures repaired with a new material. High-Performance Cementitious Composites, which is characterized by its ductility with 5% strain-capacity is used as a repair material. To investigate the validity of developed numerical model, simulations of direct tension specimen and flexural specimen are performed and the results are compared with published ones. The similar analysis is performed for RC beam. Through this study, it is seen that predicted response has a good agreement with the experimental results. Using this verified numerical model, the strengthening effect of repaired with HPCC structure is analyzed through load-displacement curve and failure modes. Also, the same numerical analysis is performed in RC beam repaired with HPCC. The effect of HPCC ductility is estimated for the overall behavior of structures. Based on the results, the fundamental data are suggested for repaired structures with HPCC.