• Proceedings of the Korea Concrete Institute Conference
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• 2005.11a
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• pp.591-594
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• 2005

Concrete structure that has been constructed in real field is on multi-axial stress state condition. After placing of concrete, hydration heat and shrinkage of concrete can cause various stress conditions with respect to the restraint level and condition. So, to predict the early age behavior of concrete structure, multi-axial material model is required and microplane model is acceptable. Recently, many studies have been performed on the microplane model, but the model developed up to now has been related to hardened concrete that material property is constant with concrete age. So, it is inappropriate to apply this model immediately to analyze the early age behavior of concrete. In this study, microplane model that can predict early age behavior of concrete was developed and cracking analysis using that was performed to describe cracking behavior for massive concrete sturucture.

• Journal of the Korea institute for structural maintenance and inspection
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• v.6 no.4
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• pp.129-137
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• 2002

In this study, mixed-mode fracture behavior is simulated effectively through the numerical method using the axial defomation link elements which can predict the behavior of quasi-brittle material. The behavior of quasi-brittle material is modeled numerically using the exponential tension softening constitutive equation and verified by comparing with the result of published experimental result. In order to verify the mixed-mode fracture behavior through the developed numerical method, analysis of mode I is formulated and the result is compared with those of FEM first, and then mixed-mode analysis is analyzed and compared with existing theories and experimental data. Also the characteristics of fracture behavior is examined through the analysis of crack generation with respect to various mode mixity.

• Computers and Concrete
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• v.31 no.6
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• pp.513-525
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• 2023

This research presents the experimental and theoretical evaluations on circular steel-fiber-reinforced-concrete (SFRC) columns reinforced by glass-fiber-reinforced-polymer (GFRP) rebar under the axial compressive loading. Test programs were designed to investigate and compare the effect of different parameters on the structural behavior of columns by performing tests. Theses variables included conventional concrete (CC), fiber concrete (FC), steel/GFRP longitudinal rebars, and transversal rebars configurations. A total of 16 specimens were constructed and categorized into four groups in terms of different rebar-concrete configurations, including GFRP-rebar-reinforced-CC columns (GRCC), GFRP-rebar-reinforced-FC columns (GRFC), steel-rebar-reinforced-CC columns (SRCC) and steel-rebar- reinforced-FC columns (SRFC). Experimental observations displayed that failure modes and cracking patterns of four groups of columns were similar, especially in pre-peak branches of load-deflection curves. Although the average ultimate axial load of columns with longitudinal GFRP rebars was obtained by 17.9% less than the average ultimate axial load of columns with longitudinal steel rebars, the average axial ductility index (DI) of them was gained by 10.2% higher than their counterpart columns. Adding steel fibers (SFs) into concrete led to the increases of 7.7% and 6.7% of the axial peak load and the DI of columns than their counterpart columns with CC. The volumetric ratio had greater efficiency on peak loads and DIs of columns than the type of transversal reinforcement. A simple analytical equation was proposed to predict the axial compressive capacity of columns by considering the axial involvement of longitudinal GFRP rebars, volumetric ratio, and steel spiral/hoop rebar. There was a good correlation between test results and predictions of the proposed equation.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.10a
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• pp.156-161
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• 1993

This paper is to develop steel fiber reinforced polymer-impregnated concrete(SFPIC) by impregnation polymer impregnate into hardened steel fiber reinforced concrete(SFRC). Steel fiber induces ductile behavior and polymer impregnant increase compressive strength. Steel fiber reinforced polymer-impregnated concrete specimens are prepared with fiber contents of 0.0, 1.5, 2.0, 2.5% and tested to obtain uni-axial and bi-axial compression strengths, tensile strength and flexural strength. The strength and mechanical properties of normal concrete, SFRC, SFPIC are compared.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2003.10a
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• pp.299-306
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• 2003

This paper presents the results of an experimental investigation pertaining to the creep behavior of fiber-reinforced polymeric (FRP) pultruded components subjected to sustained eccentric axial loading. Six different axial load/eccentricity combinations were investigated through the experiments. The test duration of these experiments was 2,000 hours (90 days), during which the mid-height lateral deflections of the components were recorded continually. Analytical formulations based on the Schapery's quasielastic method and a power law model were used for the prediction of the creep lateral deflection.

• Journal of the Korean Geosynthetics Society
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• v.21 no.2
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• pp.39-48
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• 2022

Unlike the horizontal strut, the corner strut causes bending behavior by the installation angle when soil pressure occurs, so there is a limit to its application as a elasto plastic method that requires only the axial stiffness of struts. Therefore, this study attempted to approach a method of modifying axial stiffness data to present an analysis method for corner struts in elasto plastic method, and linear elasticity analysis was used for this. And, through Linear elasticity analysis, axial stiffness data for corner struts installed at the actual site were calculated. The behavior of the retainingwall was confirmed by applying the calculated axial stiffness data of corner struts to elasto plastic method, and its applicability was evaluated by comparing it with the measurement results and the finite element analysis results. As a result of the study, when the axial stiffness data of the corner struts was applied using Linear elasticity analysis(Case 1, Case 3), the axial stiffness data decreased to 9% to 17% compared to the general method of applying the axial stiffness of the struts(Case 2, Case 4), and the displacement of the retainingwall increased to 25.33% to 64.42%. Comparing this result with the measurement results, when Linear elasticity analysis was used(Case 1, Case 3), the behavior of the retainingwall during the elasto plastic method was better shown.

• Structural Engineering and Mechanics
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• v.67 no.1
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• pp.93-104
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• 2018

The seismic behavior of reinforced concrete (RC) short columns with limited transverse reinforcement is investigated in this paper through an experimental program. The experimental program consists of four small-scale RC columns with an aspect ratio of 1.7, which are tested to the axial failure stage. The cracking patterns, hysteretic responses, strains in reinforcing bars, displacement decomposition and cumulative energy dissipation of the tested specimens are reported in detail in the paper. The effects of column axial load are investigated to determine how this variable might influence the performance of the short columns with limited transverse reinforcement. Brittle shear failure was observed in all tested specimens. Beneficial and detrimental effects on the shear strength and drift ratio at axial failure of the test specimens due to the column axial load are found in the experimental program, respectively.

• Journal of the Korea Concrete Institute
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• v.17 no.3 s.87
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• pp.435-444
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• 2005

This paper predicted the shear behavior of reinforced concrete columns using Transformation Angle Truss Model (TATM) considered the effects of bending moment and axial force. Nine columns with various shear span- to-depth ratios and axial force ratios were tested to verify the theoretical results obtained from TATM. Fine linear displacement transducers (LVDT) were attached to a side of the column near the shear critical region to measure the curvature, the longitudinal and transverse axial deformations, and the shear deformation of the column. The test was terminated when the value of the applied load dropped to about $85\%$ of the maximum-recorded load in the post-peak descending branch. All the columns were failed in shear before yielding of the flexural steel. The shear strength and the stiffness of the columns increased, as the axial force increased and the shear span-to-depth ratio decreased. Shear stress-shear strain and shear stress-strain of shear reinforcement curves obtained from TATM were agreed well with the test results in comparison to other truss models (MCFT, RA-STM, and FA-STM).

• Steel and Composite Structures
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• v.38 no.2
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• pp.223-239
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• 2021

This paper presents the analytical modeling and finite element (FE) analysis, using ABAQUS software, of the new types of steel reinforced lightweight aggregate concrete (SRLAC) columns with cross-shaped (+shaped and X-shaped) steel section, using proposed three analytical and two FE models in total. The stress-strain material models for different components in the columns, including the confined zones of the lightweight aggregate concrete (LWAC) using three and four concrete zones divisions approaches and with and without taking into account the stirrups reaction effect, are established first. The analytical models for determining the axial load-deformation behavior of the SRLAC columns are drawn based on the materials models. The analytical and FE models' results are compared with previously reported test results of the axially loaded SRLAC columns. The proposed analytical and FE models accurately predict the axial behavior and capacities of the new types of SRLAC columns with acceptable agreements for the load-displacement curves. The LWAC strength, steel section ratio, and steel section configuration affect the contact stress between the concrete and steel sections. The average ratios of the ultimate test load to the three analytical models and FEA model loads, Put /Pa1, Put /Pa2, Put /Pa3, and Put /PFE1, for the tested specimens are 0.96, 1.004, 1.016, and 1.019, respectively. Finally, the analytical parametric studies are also studied, in terms of the effects of confinement, LWAC strength, steel section ratio, and the reinforcement ratio on the axial capacity of the SRLAC column. When concrete strength, confinements, area of steel sections, or reinforcement bars ratio increased, the axial capacities increased.

• Structural Engineering and Mechanics
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• v.75 no.1
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• pp.71-86
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• 2020

This paper presents a study on the mechanical behavior of buried pipelines crossing faults using experimental and numerical methods. A self-made soil-box was used to simulate normal fault, strike-slip fault and oblique slip fault. The effects of some important parameters, including the displacement and type of fault, the buried depth and the diameter of pipe, on the deformation modes and axial strain distribution of the buried pipelines crossing faults was studied in the experiment. Furthermore, a finite element analysis (FEA) model of spring boundary was developed to investigate the performance of the buried pipelines crossing faults, and FEA results were compared with experimental results. It is found that the axial strain distribution of those buried pipelines crossing the normal fault and the oblique fault is asymmetrical along the fault plane and that of buried pipelines crossing the strike-slip fault is approximately symmetrical. Additionally, the axial peak strain appears near both sides of the fault and increases with increasing fault displacement. Moreover, the axial strain of the pipeline decreases with decreasing buried depth or increasing ratios of pipe diameter to pipe wall thickness. Compared with the normal fault and the strike-slip fault, the oblique fault is the most harmful to pipelines. Based on the accuracy of the model, the regression equations of the axial distance from the peak axial strain position of the pipeline to the fault under the effects of buried depth, pipe diameter, wall thickness and fault displacement were given.