• Journal of the Korea Concrete Institute
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• v.19 no.2
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• pp.189-197
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• 2007

Concrete tunnel lining must be designed to having the fireproof performance because the lining are sometimes exposed to very high temperature due to traffic accident. Such fire temperature may cause explosion of concrete, or collapse of tunnel structure. The purpose of this study is to obtain the fundamental fireproof behavior of fire resistance-engineered cementitious composites(FR-ECC) under fire temperature in order to use the fire protection material in tunnel lining system. The present study conducted the experiment to simulate fire temperature by employing 2 types of FR-ECC and investigated experimentally the explosion and cracks in heated surface of these FR-ECC. Employed temperature curve were hydro carbon(HC, ECl) criterion, which are severe in various criterion of fire temperature. The numerical analysis is carried out the nonlinear transient heat flow analysis and verified against the experimental data. The complex features of behavior in fire conditions, such as thermal expansion, plasticity, cracking or crushing, and material properties changing with temperature are considered. By the use of analytical model, the concrete tunnel subjected to fire loads were analyzed and discussed. With comparison of current concrete materials and FR-ECC, the experimental and analytical results of FR-ECC shows the better fire resistance performance than the other.

• Journal of the Korea Concrete Institute
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• v.19 no.3
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• pp.283-292
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• 2007

A research projects is currently being conducted to develop a nonlinear finite element analysis methods for predicting the structural behavior of reinforced concrete frame structures, exposed to fire. As part of this, reinforced concrete frames subjected to fire loads were analyzed using the nonlinear finite-element program DIANA. Two numerical steps are incorporated in this program. The first step carries out the nonlinear transient heat flow analysis associated with fire and the second step predicts the structural behavior of reinforced concrete frames subjected to the thermal histories predicted by first step. The complex features of structural behavior in fire conditions, such as thermal expansion, plasticity, cracking or crushing, and material properties changing with temperature are considered. A concrete material model based on nonlinear fracture mechanics to take cracking into account and plasticity models for concrete in compression and reinforcement steel were used. The material and analytical models developed in this paper are verified against the experimental data on simple reinforced concrete beams. The changes in thermal parameters are discussed from the point of view of changes of structure and chemical composition due to the high temperature exposure. Although, this study considers codes standard fire for reinforced concrete frame, any other time-temperature relationship can be easily incorporated.

• Earthquakes and Structures
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• v.7 no.2
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• pp.179-199
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• 2014

The steel tube-reinforced concrete (ST-RC) composite column is a novel type of composite column, consisting of a steel tube embedded in reinforced concrete. The objective of this paper is to investigate the effect of cumulative damage on the seismic behavior of ST-RC columns through experimental testing. Six large-scale ST-RC column specimens were subjected to high axial forces and cyclic lateral loading. The specimens included two groups, where Group I had a higher amount of transverse reinforcement than Group II. The test results indicate that all specimens failed in a flexural mode, characterized by buckling and yielding of longitudinal rebars, failure of transverse rebars, compressive crushing of concrete, and steel tube buckling at the base of the columns. The number of loading cycles was found to have minimal effect on the strength capacity of the specimens. The number of loading cycles had limited effect on the deformation capacity for the Group I specimens, while an obvious effect on the deformation capacity for the Group II specimens was observed. The Group I specimen showed significantly larger deformation and energy dissipation capacities than the corresponding Group II specimen, for the case where the lateral cyclic loads were repeated ten cycles at each drift level. The ultimate displacement of the Group I specimen was 25% larger than that of the Group II counterpart, and the cumulative energy dissipated by the former was 2.8 times that of the latter. Based on the test results, recommendations are made for the amount of transverse reinforcement required in seismic design of ST-RC columns for ensuring adequate deformation capacity.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2001.05a
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• pp.119-126
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• 2001

The potential pollution problems resulting from tanker collision necessitate the requirement for an effective structural design and the development of relevant safety regulation. During a few decades, the great effort has been made by International Maritime Organization and the Administration, etc, to reduce oil spillage from collision accidents. However there is still a need for investigation in the light of structural evaluation method for the experiments and rational analysis, and design development for an operational purpose of ships. This study is aimed at investigating a complicated structural response of bow structures of oil carriers for assessing the energy dissipation and crushing mechanics of striking vessel through a methodology of the numerical analysts for the various models and its design changes. Through this study an optimal bow construction absorbing great portion of kinetic energy in the least penetration depth prior to reach to the cargo area and an effective location of collision bulkhead are investigated. In order to obtain a rational results in this study, three stages of response analysis procedures are performed as follows; 1). 16 simplified ship models are used to investigate the structural response against bow collision with variation of primary and secondary members. Mass and speed are also varied in two conditions. 2). 21 models conisted of 5 size of full scaled oil carriers are used to perform the collision simulation with the various sizes and deadweight delivered in a recent which are complied with SOLAS and MARPOL. 3). 36 models of 100k oil carrier are used to investigate the structural response and its influence to the collision bulkhead against bow collision in variation with location of collision bulkhead, primary mombers, framing system and colliding conditions, etc.

• Journal of the Korea institute for structural maintenance and inspection
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• v.14 no.1
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• pp.175-181
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• 2010

The three truss models(equilibrium truss model, Mohr compatibility truss model, and the soften truss model) based on a rotating angle is called the rotating-angle model. The three rotating-angle models have a common weakness: they are incapable of predicting the so-called "contribution of concrete". To take into account this "contribution of concrete", the modern truss model(MCFT, STM) treats a cracked reinforced concrete element as a continuous material. By combining the equilibrium, compatibility, and the softened stress-strain relationship of concrete in biaxial state, MTM is capable of producing the nonlinear analysis of reinforced concrete structures composed of membrane element. In this paper, an efficient algorithm is proposed for the solution of proposed model incorporated with failure criteria. This algorithm is used to analyze the behavior of reinforced membrane element using the results of Hsu test.

• Journal of the Earthquake Engineering Society of Korea
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• v.23 no.5
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• pp.239-248
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• 2019

In this study, the out-of-plane seismic resistance of lightly-reinforced existing walls strengthened with thick RC jacket was investigated. The thick RC jacket with a thickness of 500 mm was placed at one side of the thin existing wall with a thickness of 150 mm. At the interface between the wall and RC jacket, a tee-shaped steel section with a number of anchor bolts and dowel bars was used as the shear connector. To investigate the connection performance and strengthening effects, the cyclic loading tests of four jacketed wall specimens were performed. The tests showed that the flexural strength of the jacketed walls under out-of-plane loading was significantly increased. During the initial behavior, the tee shear connector transferred forces successfully at the interface without slip. However, as the cracking, spalling, and crushing of the concrete increased in the exiting walls, the connection performance at the interface was significantly degraded and, consequently, the strength of the jacketed walls was significantly decreased. The flexural strength of the jacketed walls with tee shear connector was estimated considering the full and partial composite actions of the tee shear connector.

• Structural Engineering and Mechanics
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• v.77 no.2
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• pp.179-196
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• 2021

Experimental investigations on the seismic behaviors of the PVC-FRP Confined Reinforced Concrete (PFCRC) columns under low cyclic loading are carried out and two variable parameters including CFRP strips spacing and axial compression ratio are considered. The PFCRC column finally fails by bending and is characterized by the crushing of concrete and yielding of the longitudinal reinforcement, and the column with a high axial compression ratio is also accompanied by the cracking of the PVC tube and the fracture of CFRP strips. The hysteretic curves and skeleton curves of the columns are obtained from the experimental data. With the increase of axial compression ratio, the stiffness degradation rate accelerates and the ductility decreases. With the decrease of CFRP strips spacing, the unloading sections of the skeleton curves become steep and the ductility reduces significantly. On the basis of fiber model method, a numerical analysis approach for predicting the skeleton curves of the PFCRC columns is developed. Additionally, a simplified skeleton curve including the elastic stage, strengthening stage and unloading stage is suggested depending on the geometric drawing method. Moreover, the loading and unloading rules of the PFCRC columns are revealed by analyzing the features of the skeleton curves. The quantitative expressions that are used to predict the unloading stiffness of the specimens in each stage are proposed. Eventually, an analytical model for the PFCRC columns under low cyclic loading is established and it agrees well with test data.

• Journal of the Korean Geosynthetics Society
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• v.21 no.3
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• pp.71-78
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• 2022

In this study, the applicability of underground displacement sensors was considered through rock blasting tests to develop a relatively inexpensive and efficient slope failure prediction system that can quickly detect the risk of slope failure in advance and issue predictions and warnings with accurate judgment. In the blasting experiment, the sensor located close to the blasting source showed a large displacement due to crushing inside the rock and the sensor located away from the blasting source showed a relatively small strain. This study confirmed that the wired and wireless type underground displacement sensor system can be applied to measure the behavior of the rock slope, and it can be used as a basic data for establishing an early warning system to predict slope failure.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.2
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• pp.138-145
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• 2017

The purpose of this study is to establish a reasonable analytical method for the estimation of overall behavior characteristic from cracking to yielding of rebar and crushing of concrete and seismic performance of reinforced concrete shear wall with high-strength reinforcing bar. A total of 8 specimens of reinforced concrete walls which have constant aspect ratio and a variety of variables such as reinforcement ratio, reinforcement yielding strength, reinforcement details, concrete design strength, section shape and whether lateral restraint hoop were selected and the analysis was performed by using a non-linear finite element analysis program (RCAHEST) applying the proposed constitutive equation by the authors. The mean and coefficient of variation for maximum load from the experiment and analysis results was predicted 1.04 and 8%. The mean and coefficient of variation for displacement corresponding maximum load from the experiment and analysis results was predicted 1.17 and 19% respectively. The analytical results were predicted relatively well the fracture mode and the overall behavior until fracture for all specimens. These results are expected to be used as basic data for application of high-strength reinforcing bar to design codes in the future.

• Journal of the Korea Concrete Institute
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• v.23 no.2
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• pp.169-176
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• 2011

In this study, the flexural test for reinforced high performance fiber reinforced cementitious composites (R/HPFRCC) members has been conducted in order to investigate the flexural behavior including the effect of an ordinary tensile reinforcing bar. Through the test, it was observed that the flexural strength increased due to the stable tensile stress transfer of HPFRCC, even up to the ultimate state. In addition, no localized crack appeared until the yielding of the reinforcement. From the layered section analysis of the tested members, it was found that the analysis with the tensile model obtained from the tension stiffening test showed better agreement with the flexural test results, whereas the analysis with direct tension test results overestimated the flexural capacity. Through the experimental and analytical studies, two flexural failure modes have been defined in this paper; concrete crushing at the top compression layer or tensile failure at the bottom tensile layer of the beam section. Based on these two flexural failure modes, a simple formula that estimates the ultimate flexural strength of the member has been proposed in this paper. The proposed equations can be useful in a design and an analysis of R/HPFRCC members.