• Journal of the Korea institute for structural maintenance and inspection
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• v.22 no.6
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• pp.130-137
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• 2018

Many constitutive models for concrete have been developed to predict the nonlinear behavior of concrete members considerably. The constitutive model for reinforcing bar that include the tension stiffening effect due to the bond characteristics between steel bars and concrete is being studied but the bilinear model is generally used. It was found that the buckling of the longitudinal reinforcing bars is controlled the nonlinear behavior of hybrid precast concrete panel, which is being developed for core wall. In this study, the constitutive models that can consider the embedding and buckling effects of reinforcing bar are investigated and a new model combing these constitutive models is proposed. In order to verify the proposed model, the analysis results are compared with experimental results of the concrete wall and hybrid precast concrete panel. The analysis of embedding-effect-only modeling predicted that the deformation increases continually without the decrease in the load carrying capacity. However, the analysis results of proposed model showed good agreement with some experimental results, thus verifying the proposed computational model.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.6
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• pp.283-291
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• 2018

This study intends to develop an analytical model of unreinforced masonry(URM) walls for the nonlinear static analysis which has been generally used to evaluate the seismic performance of a building employing URM walls as seismic force-resisting members. The developed model consists of fiber elements used to capture the flexural behavior of an URM wall and a shear spring element implemented to predict its shear response. This paper first explains the configuration of the proposed model and describes how to determine the modeling parameters of fiber and shear spring elements based on the stress-strain curves obtained from existing experimental results of masonry prisms. The proposed model is then verified throughout the comparison of its nonlinear static analysis results with the experimental results of URM walls carried out by other researchers. The proposed model well captures the maximum strength, the initial stiffness, and their resulting load - displacement curves of the URM walls with reasonable resolution. Also, it is demonstrated that the analysis model is capable of predicting the failure modes of the URM walls.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.4
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• pp.120-130
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• 2019

In this study, based on the correlation between traffic volume data and vertical displacement data developed in previous research using the bridge maintenance big data of 2006, the vertical displacement estimation model using the traffic volume data of Gwangan Bridge for 10 years A comparison of the performance of the developed model with the current applicability is presented. The present applicability of the developed model is analyzed that the estimated displacement is similar to the actual displacement and that the displacement estimation performance of the model based on the structured regression analysis and the principal component analysis is not significantly different from each other. In conclusion, the vertical displacement estimation model using the traffic volume data developed by this study can be effectively used for the analysis of the behavior according to the traffic load of Gwangan Bridge.

• Structural Engineering and Mechanics
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• v.85 no.2
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• pp.179-195
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• 2023

The performance of reinforced concrete (RC) beam specimens strengthened using a newly proposed Side Near Surface Mounted (S-NSM) technology was investigated experimentally in this work. In addition, analytical and nonlinear finite element (FE) modeling was exploited to forecast the performance of RC members reinforced with S-NSM utilizing steel bars. Five (one control and four strengthened) RC beams were evaluated for flexural performance under static loading conditions employing four-point bending loads. Experimental variables comprise different S-NSM reinforcement ratios. The constitutive models were applied for simulating the non-linear material characteristics of used concrete, major, and strengthening reinforcements. The failure load and mode, yield and ultimate strengths, deflection, strain, cracking behavior as well as ductility of the beams were evaluated and discussed. To cope with the flexural behavior of the tested beams, a 3D non-linear FE model was simulated. In parametric investigations, the influence of S-NSM reinforcement, the efficacy of the S-NSM procedure, and the structural response ductility are examined. The experimental, numerical, and analytical outcomes show good agreement. The results revealed a significant increase in yield and ultimate strengths as well as improved failure modes.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.35 no.3
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• pp.191-196
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• 2022

In this study, the anisotropic mechanical property of fused deposition modeling three-dimensional (3D) printing based on lamination direction was verified by a tensile test. Moreover, the property was applied to solid isotropic materials with penalization-based topology optimization. The case of the lower control arm, one of the automotive suspension components, was considered as a benchmark problem. The optimal topological results varied depending on the external load and anisotropic property. Based on these results, two test specimens were fabricated by varying the lamination direction of 3D printing; a tensile test utilizing 3D non-contact strain gauge was also conducted. The measured strain was compared with that obtained by computer-aided engineering response analysis. Quantitatively, the measurement and analysis results are found to have good agreement. The effectiveness of topology optimization considering the lamination direction of 3D printing was confirmed by the experimental result.

• Structural Engineering and Mechanics
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• v.86 no.3
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• pp.399-415
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• 2023

This paper presents the experimental and numerical evaluations on the circular SFRC columns reinforced GFRP rebars under the axial compressive loading. The test programs were designed to inquire and compare the effects of different parameters on the columns' structural behavior by performing experiments and finite element modeling. The research variables were conventional concrete (CC), fiber concrete (FC), types of longitudinal steel/GFRP rebars, and different configurations of lateral rebars. A total of 16 specimens were manufactured and categorized into four groups based on different rebar-concrete arrangements including GRCC, GRFC, SRCC, and SRFC. Adding steel fibers (SFs) into the concrete, it was essential to modify the concrete damage plastic (CDP) model for FC columns presented in the finite element method (FEM) using ABAQUS 6.14 software. Failure modes of the columns were similar and results of peak loads and corresponding deflections of compression columns showed a suitable agreement in tests and numerical analysis. The behavior of GFRP-RC and steel-RC columns was relatively linear in the pre-peak branch, up to 80-85% of their ultimate axial compressive loads. The axial compressive loads of GRCC and GRFC columns were averagely 80.5% and 83.6% of axial compressive loads of SRCC and SRFC columns. Also, DIs of GRCC and GRFC columns were 7.4% and 12.9% higher than those of SRCC and SRFC columns. Partially, using SFs compensated up to 3.1%, the reduction of the compressive strength of the GFRP-RC columns as compared with the steel-RC columns. The effective parameters on increasing the DIs of columns were higher volumetric ratios (up to 12%), using SFs into concrete (up to 6.6%), and spiral (up to 5.5%). The results depicted that GFRP-RC columns had higher DIs and lower peak loads compared with steel-RC columns.

• Journal of the Korea institute for structural maintenance and inspection
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• v.28 no.2
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• pp.77-86
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• 2024

In this study, authors attempted to determine the bond behavior characteristics to utilize Grid typed CFRP reinforcement as an alternative to steel rebar used as concrete reinforcement. Since it is difficult to understand the influence of the transverse grid length of the Grid typed CFRP reinforcement in the existing numerical analysis proposal for bond behavior, a nonlinear 3D model was created and finite element analysis was performed. To perform the analysis, the analysis was conducted by inputting a nonlinear material model and modeling the bond interface characteristics between the Grid typed CFRP reinforcement and concrete and comparing them with the actual direct pull-out test results. The bond behavior characteristics of the Grid typed CFRP reinforcement were found to be very dominated by the factors of the transverse grid, and showed a tendency to continuously increase load.

• Journal of the Earthquake Engineering Society of Korea
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• v.28 no.4
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• pp.193-203
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• 2024

Existing reinforced concrete (RC) building frames constructed before the seismic design was applied have seismically deficient structural details, and buildings with such structural details show brittle behavior that is destroyed early due to low shear performance. Various reinforcement systems, such as fiber-reinforced polymer (FRP) jacketing systems, are being studied to reinforce the seismically deficient RC frames. Due to the step-by-step modeling and interpretation process, existing seismic performance assessment and reinforcement design of buildings consume an enormous amount of workforce and time. Various machine learning (ML) models were developed using input and output datasets for seismic loads and reinforcement details built through the finite element (FE) model developed in previous studies to overcome these shortcomings. To assess the performance of the seismic performance prediction models developed in this study, the mean squared error (MSE), R-square (R²), and residual of each model were compared. Overall, the applied ML was found to rapidly and effectively predict the seismic performance of buildings according to changes in load and reinforcement details without overfitting. In addition, the best-fit model for each seismic performance class was selected by analyzing the performance by class of the ML models.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.1
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• pp.391-400
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• 2019

In the case of fire, a structure loses its original stiffness due to the temperature rise, and the load bearing capacity decreases. The loss of structural strength increases with increasing fire time of the structure. To prevent the collapse of buildings, it is very important to understand whether or not the members are damaged. On the other hand, there is insufficient data to be a guideline for diagnosing and evaluating the residual strength of the members in Korea. Therefore, this study examined the resistance performance by Finite-Element-Analysis of composite beams, which are composite structures among structural members. Composite beam modeling was carried out based on the model used in the Electrical Penetration Room (EPR) in cooperation with KEPCO. The heat transfer analysis and structural analysis of the critical phase were performed using ANSYS, a finite element analysis program. ANSYS was used to perform heat transfer analysis and structural analysis at the static analysis. To analyze the residual performance, the temperature distribution of the composite beam and the maximum displacement result of the heat-affected structure analysis were derived and the experimental data and the structural analysis result data were compared and analyzed.

• Journal of the Korea Institute of Building Construction
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• v.22 no.2
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• pp.161-169
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• 2022

The government [3] specifies steel pipe scaffolding as conventional scaffolding and is promoting the installation of system scaffolding, an integrated work platform, and avoidance of the use of steel pipe scaffolding as much as possible. However, in places where equipment cannot enter, such as power plants and plant sites, places the structure is complex, and places where scaffolding cannot be stacked on the ground, there is no choice but to install steel pipe scaffolding. When installing steel pipe scaffolding on an H-beam structure at a high place, the performance of the steel frame clamp is very important in order to form a work space which workers can work safely. In this study, the displacement magnitude and tensile load of members in each installation direction of the clamp for steel frame were verified through performance tests and structural analysis modeling. As a result, it was confirmed that the performance for each installation direction satisfies the safety certification standard tensile load of 10,000N. Although the performance value is satisfactory, deformation of the attachment pressing bolt was verified and was confirmed to have minimal deformation. Thus, to ensure the load is properly to the attachment body, the clamp for a steel frame must be installed in the direction in which the load is transmitted.