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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of The Korean Society of Civil Engineers
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Korean Society of Civil Engeneers
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Volume & Issues
Volume 26, Issue 6D - Nov 2006
Volume 26, Issue 6C - Nov 2006
Volume 26, Issue 6B - Nov 2006
Volume 26, Issue 6A - Nov 2006
Volume 26, Issue 5D - Sep 2006
Volume 26, Issue 5C - Sep 2006
Volume 26, Issue 5B - Sep 2006
Volume 26, Issue 5A - Sep 2006
Volume 26, Issue 4D - Jul 2006
Volume 26, Issue 4C - Jul 2006
Volume 26, Issue 4B - Jul 2006
Volume 26, Issue 4A - Jul 2006
Volume 26, Issue 3D - May 2006
Volume 26, Issue 3C - May 2006
Volume 26, Issue 3B - May 2006
Volume 26, Issue 3A - May 2006
Volume 26, Issue 2D - Mar 2006
Volume 26, Issue 2C - Mar 2006
Volume 26, Issue 2B - Mar 2006
Volume 26, Issue 2A - Mar 2006
Volume 26, Issue 1D - Jan 2006
Volume 26, Issue 1C - Jan 2006
Volume 26, Issue 1B - Jan 2006
Volume 26, Issue 1A - Jan 2006
Selecting the target year
Confining Effect of an Internal Steel Tube in a Circular Hollow RC Column
Han, Taek Hee ; Kim, Hong Jung ; Kim, Young Jong ; Kang, Young Jong ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 565~575
When concrete is confined, its strength is enhanced by confining stress. Thus, increasing confining stress makes concrete strength higher. But a brittle failure may occur in hollow RC(Reinforced Concrete) column although its concrete is confined by transverse reinforcements. This brittle failure results from the absence of internal confinement and it decreases the strength and the ductility of a hollow RC column. To overcome this brittle failure problem, a hollow RC column which has a internal steel tube was developed. In this study, an experiment was performed to investigate the existence of to internal confinement by a settled steel tube. Thirty six specimens were tested and test results show the existence of internal confinement by the increase of concrete strength.
Nonlinear Finite Element Analysis of Reinforced Concrete Column using Timoshenko Beam Theory and Fiber Section Model
Park, Soon Eung ; Park, Moon Ho ; Kwon, Min Ho ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 577~585
In this research, nonlinear Timoshenko beam element that is able to capture nonlinear shear deformation is developed. The proposed model shows more reasonable prediction than Bernoulli beam theory in short columns or strong shear column due to the consideration of shear deformation. The cross-section is modeled as fiber approach. Since the model is based on the fiber approach for section discretization, the plastic progress of the section can be traced and the coupling effect of the axial and flexural response. The developed element is implemented into the finite element program to analysis general reinforced concrete structures. As parametric study, reinforced concrete columns are analyzed and compared with experimental results, analyzed the property of behavior for reinforced concrete columns.
Damage Analysis of Thin Steel Members with Bolt Connection Using Lamb Wave and PZT Element
Rhee, Inkyu ; Kwak, Hyo-Gyoung ; Kim, Jae Hong ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 587~596
A half portion of Korean railway bridges depends on the type of steel plate girder bridge. Since these bridges have been built in the early stage of Korean economical boom, numerous maintenance effort suffers from aging and progressive degradation issues at present. In accordance with these efforts, this paper would like to address the detailed analyses of thin steel plates with bolts in order to simulate the connection regions of steel plate girder bridge. The fundamental modal analysis, transient dynamic analysis with 3D piezoelectric element in open circuit loop and signal process with aids of TOF(time of flight) and WC(wavelet coefficient) are extensively discussed.
A Study of Static Behavior of FRP Bridge Deck Concerning Connection Condition
Yong, Hwan Sun ; Hwang, Yoon Koog ; Kyung, Kab Su ; Park, Yong Chan ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 597~604
Fiber Reinforced Polymer (FRP) is a relatively new material in the bridge construction. With high strength to weight ratios, excellent durability, and low life-cycle costs of FRP, FRP bridge decks can offer a low dead load, reduced maintenance, and long service life. Due to the lightweight of FRP, if existing concrete decks can be replaced with the FRP decks, the load carrying capacity of superstructure can be increased without strengthening of girders. In this study, we have conducted an experiment on 7 cases of connection conditions with steel girder by using bolts considering a rational and economical method of connection and compared with the results of FEM analysis. From the experimental result, if the bolts are strong enough to resist shear force between the FRP bridge deck and the steel girder, it will be structurally secure to use the zigzag method.
Performance Evaluation of Smart Accelerometers for Structural Health Monitoring
Yi, Jin-Hak ; O, Hye-Sun ; Yun, Chung-Bang ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 605~609
In this study, two kinds of smart accelerometers are investigated for the application of smart sensors to the structural health monitoring of infrastructures. Smart optical Fiber Bragg Grating (FBG) type and Micro-Electo-Mechanical System (MEMS) type accelerometers are selected for this study and the high sensitive ICP type accelerometer is used for the reference sensor. Small size shaking table tests were performed with 3-story shear building model using random input ground motions. The output only modal identification was carried out using stochastic subspace identification and the performances of sensors are compared in modal domain indirectly. The modal sensitivity method was applied to update the story stiffness of numerical model and the updated results were verified using the additional experiments for the same structure with additional mass.
Redundancy Evaluation of the Composite Two Steel Plate-Girder Bridges
Park, Yong-Myung ; Joe, Woom-Do-Ji ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 611~620
The composite two plate-girder bridges are generally defined as a non-redundant load path structure because the bridge can collapse if one of the two girders is seriously damaged by a fatigue crack. In this paper, a numerical study on the evaluation of the after-fracture redundancy of the composite two-girder bridges was accomplished. The evaluation has been performed on the simple and three-span continuous bridges with I-section cross beams which serve as transverse bracing, and with or without the bottom lateral bracing system. The load carrying capacities of the intact and damaged bridges with or without lateral bracing were evaluated from material and geometric nonlinear analysis, respectively and the redundancy was evaluated for each case. It was acknowledged from the analytical results that both simple and continuous intact two-girder bridges have sufficient redundancy even without lateral bracing, but it takes an important role to improve the redundancy of damaged bridges.
Grid Strut-Tie Model Approach for Structural Concrete Design
Yun, Young Mook ; Kim, Byung Hun ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 621~637
Although the approaches implementing strut-tie models are the valuable tools for designing discontinuity regions of structural concrete, the approaches of the current design codes have to be improved for the design of structural concrete subjected to complex loading and geometrical conditions because of the uncertainties in the selection of strut-tie model, in the use of an indeterminate strut-tie model, and in the effective strengths of struts and nodal zones. To improve the uncertainties, a grid struttie model approach is proposed in this study. The proposed approach, allowing to perform a consistent and effective design of structural concrete, employs an initial grid strut-tie model in which various load combinations can be considered. In addition, the approach performs an automatic selection of an optimal strut-tie model by evaluating the capacities of struts and ties using a simple optimization algorithm. The validity and effectiveness of the proposed approach is verified by conducting the analysis of the four reinforced concrete deep beams tested to failure and the design of shearwalls with two openings.
Development of Estimated Model for Axial Displacement of Hybrid FRP Rod using Strain
Kwak, Kae-Hwan ; Sung, Bai-Kyung ; Jang, Hwa-Sup ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 639~645
FRP (Fiber Reinforced Polymer) is an excellent new constructional material in resistibility to corrosion, high intensity, resistibility to fatigue, and plasticity. FBG (Fiber Bragg Grating) sensor is widely used at present as a smart sensor due to lots of advantages such as electric resistance, small-sized material, and high durability. However, with insufficiency of measuring displacement, FBG sensor is used only as a sensor measuring physical properties like strain or temperature. In this study, FRP and FBG sensors are to be hybridized, which could lead to the development of a smart FRP rod. Moreover, developing the estimated model for deflection with neural network method, with the data measured through FBG sensor, could make conquest of a disadvantage of FBG sensor - uniquely used for sensing strain. Artificial neural network is MLP (Multi-layer perceptron), trained within error rate of 0.001. Nonlinear object function and back-propagation algorithm is applied to training and this model is verified with the measured axial displacement through UTM and the estimated numerical values.
Probabilistic Risk Assessment of a Cable-Stayed Bridge Based on the Prediction Method for the Combination of Failure Modes
Park, Mi-Yun ; Cho, Hyo-Nam ; Cho, Taejun ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 647~657
Probabilistic Risk Assessment considering statistically random variables is performed for the preliminary design of a Cable Stayed Bridge, which is Prestressed Concrete Bridge consisted of cable and plate girders, based on the method of Working Stress Design and Strength Design. Component reliabilities of cables and girders have been evaluated using the response surface of the design variables at the selected critical sections based on the maximum shear, positive and negative moment locations. Response Surface Method (RSM) is successfully applied for reliability analyses for this relatively small probability of failure of the complex structure, which is hard to obtain through Monte-Carlo Simulations. or through First Order Second Moment Method that can not easily calculate the derivative terms of implicit limit state functions. For the analysis of system reliability, parallel resistance system consisting of cables and plate girder is changed into series connection system and the result of system reliability of total structure is presented. As a system reliability, the upper and lower probabilities of failure for the structural system have been evaluated and compared with the suggested prediction method for the combination of failure modes. The suggested prediction method for the combination of failure modes reveals the unexpected combinations of element failures in significantly reduced time and efforts compared with the previous permutation method or system reliability analysis method, which calculates upper and lower bound failure probabilities.
Effect of Nonlinear Analysis Procedures for Seismic Responses of Reinforced Concrete Wall Structure
Song, Jong-Keol ; Jang, Dong-Hui ; Chung, Yeong-Hwa ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 659~675
Recently, significant progress has been made in performance-based engineering methods that rely mainly on nonlinear static seismic analysis procedures. The Capacity Spectrum Method (CSM) and the Displacement Coefficient Method (DCM) are the representative nonlinear static seismic analysis procedures. In order to evaluate the applicability of the procedures to the seismic evaluation and design process of new and existing structures, the accuracy of both CSM and DCM should be evaluated in advance. The accuracy of seismic responses by the nonlinear static procedures is evaluated in comparison with the shaking table test results for the structural wall specimen subjected to the far field and near field earthquakes. Also conducted are comparative studies where the shaking table test results are compared with those from nonlinear dynamic analysis procedures, i.e., Single-Degree-of-Freedom (SDOF), equivalent SDOF and Multi-Degree-of-Freedom (MDOF) systems.
Stress Recovery Technique by Ordinary Kriging Interpolation in p-Adaptive Finite Element Method
Woo, Kwang Sung ; Jo, Jun Hyung ; Lee, Dong Jin ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 677~687
Kriging interpolation is one of the generally used interpolation techniques in Geostatistics field. This technique includes the experimental and theoretical variograms and the formulation of kriging interpolation. In contrast to the conventional least square method for stress recovery, kriging interpolation is based on the weighted least square method to obtain the estimated exact solution from the stress data at the Gauss points. The weight factor is determined by variogram modeling for interpolation of stress data apart from the conventional interpolation methods that use an equal weight factor. In addition to this, the p-level is increased non-uniformly or selectively through a posteriori error estimation based on SPR (superconvergent patch recovery) technique, proposed by Zienkiewicz and Zhu, by auto mesh p-refinement. The cut-out plate problem under tension has been tested to validate this approach. It also provides validity of kriging interpolation through comparing to existing least square method.
Analysis of NEESgrid Computing and System for Korean Construction Test Equipments Infrastructure
Jeong, Tai Kyeong ; Shim, Nak Hoon ; Park, Young Suk ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 689~692
This paper presents the developments of Grid computing architecture which is use many data and resources from distributed and parallel system for construction test equipments, i.e., large scale computer networks meant to provide access to massive computational facilities for very large communities of users, drawing upon experiences of existing Grids architecture. In this paper, we present an efficient way to construct a construction test equipment infrastructure.
Damage Detection in Steel Box Girder Bridge using Static Responses
Son, Byung Jik ; Huh, Yong-Hak ; Park, Philip ; Kim, dong Jin ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 693~700
To detect and evaluate the damage present in bridge, static identification method is known to be simple and effective, compared to dynamic method. In this study, the damage detection method in steel box girder bridge using static responses including displacement, slope and curvature is examined. The static displacement is calculated using finite element analysis and the slope and curvature are determined from the displacement using central difference method. The location of damage is detected using the absolute differences of these responses in intact and damaged bridge. Steel box girder bridge with corner crack is modeled using singular element in finite element method. The results show that these responses were significantly useful in detecting and predicting the location of damage present in bridge.
An Experimental Method for the Evaluation of Dead Load Stress in Existing Concrete Bridges
Park, Dae Sung ; Kim, Woo ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 701~706
This paper describes an attempt to develop a practical method for the measurement of dead load stress in existing concrete bridges. In most cases, the dead load stress was determined by various theoretical calculations. However, the theoretical calculation cannot always provide a sufficient information on the current stress state due to lots of uncertainty. The key idea incorporated with this paper is the partial sectioning method which is able to estimate current stress state in concrete bridges subjected to dead load. The proposed method is applied to the safety assessment of actual concrete bridges and the applicability of this system is investigated.
Dynamic Performance Estimation of the Incrementally PSC Girder Railway Bridge by Modal Tests and Moving Load Analysis
Kim, Sung Il ; Kim, Nam Sik ; Lee, Hee Up ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 707~717
As an alternative to conventional prestressed concrete (PSC) girders, various types of PSC girders are either under development or have already been applied in bridge structures. Incrementally prestressed concrete girder is one of these newly developed girders. According to the design concept, these new types of PSC girders have the advantages of requiring less self-weight while having the capability of longer spans. However, the dynamic interaction between bridge superstructures and passing trains is one of the critical issues concerning these railway bridges designed with more flexibility. Therefore, it is very important to evaluate modal parameters of newly designed bridges before doing dynamic analyses. In the present paper, a 25 meters long full scale PSC girder was fabricated as a test specimen and modal testing was carried out to evaluate modal parameters including natural frequencies and modal damping ratios at every prestressing stage. During the modal testing, a digitally controlled vibration exciter as well as an impact hammer is applied, in order to obtain precise frequency response functions and the modal parameters are evaluated varying with construction stages. Prestressed force effects on changes of modal parameters are analyzed at every incremental prestressing stage. With the application of reliable properties from modal experiments, estimation of dynamic performances of PSC girder railway bridges can be obtained from various parametric studies on dynamic behavior under the passage of moving train. Dynamic displacements, impact factor, acceleration of the slab, end rotation of the girder, and other important dynamic performance parameters are checked with various speeds of the train.
Sensitivity of the Continuous Welded Rail and the Fastener on the Track Stability
Han, Sang Yun ; Park, Nam Hoi ; Lim, Nam Hyoung ; Kang, Young Jong ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 719~726
The use of CWR track not only reduces the track maintenance cost, but increase the life cycle of track components. Therefore, the use of the CWR track has increased consistently in the worldwide. As the use of CWR increases in track structures, derailing disasters associating with track buckling also increase in great numbers due to high compressive thermal stress in the summer. Among many CWR parameters, the influence of the sectional properties of the rail was investigated on the stability of CWR track in this study. Also, the sensitivity of the broken fastener and the stiffness of the fastener system such as the translational and rotational stiffness was investigated.
Experimental Study on Ultimate Shear Strength of Horizontally Curved Plate Girder Web Panels
Lee, Doo Sung ; Park, Chan Sik ; Lee, Sung Chul ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 727~734
Although a limited number of experimental investigations and finite element analyses revealed that a curved web panel in practical design has a considerable reserve strength after the elastic buckling as a straight girder web panel, the current Guide Specifications for Horizontally Curved Steel Girder Highway Bridges (AASHTO, 2003) do not consider the postbuckling strength in the ultimate shear strength due to lack of a comprehensive study. In this study, the ultimate shear strength behavior of horizontally curved steel web panels was investigated through nonlinear finite element analysis and experimental test. It was found that curved web panels used in practical designs are able to develop the postbuckling strength that is equivalent to that of straight girder web panels having the same dimensional and material properties.
The Rigidity of Transverse Intermediate Stiffener of Horizontally Curved Plate Girder Web Panels
Lee, Doo Sung ; Park, Chan Sik ; Lee, Sung Chul ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 735~742
In this study, the ultimate shear strength behavior of transversely stiffened curved web panels was investigated through nonlinear finite element analysis. It was found that if the transverse stiffener has a sufficient rigidity, then curved web panels used in practical designs are able to develop the postbuckling strength that is equivalent to that of straight girder web panels having the same dimensional and material properties. The nonlinear analysis results indicate that in order for curved web panels to develop the potential postbuckling strength. The rigidity of the transverse stiffener needs to be increased several times the value obtained from the Guide Specifications (AASHTO, 2003). However, in the case of thick web panels where the shear design is governed by shear yielding, the stiffener rigidity does not have to be increased. From the analysis results, a simple design formula is suggested for the rigidity of transverse stiffener under strength limit state.
Stress-Strain Relations of Concrete According to the Confining Conditions
Im, Seok Been ; Han, Taek Hee ; Han, Sang Yun ; Kang, Young Jong ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 743~752
Confined concrete has enhanced strength and ductility compared with unconfined strength. Cause of these merits of confined concrete, many researches have been performed for confining effects of concrete and been studied in many fields. Although many researches about concrete confined by FRP sheets have been studied recently, it is difficult to apply concrete confined by FRP in real structures because FRP is a brittle material. In this study, the enhanced strength and ductility of concrete which is confined by steel tubes or steel plates were investigated. Fifty one specimens were tested and each specimen has different confining condition. Test results showed enhanced ductility and strength of confined concrete and concrete models were suggested under various confining conditions by regression of experimental data.
Influence of Water-Cement Ratios and Curing Conditions on the Diffusion Characteristics of Chloride Ion in Concrete
Bae, Su-Ho ; Lee, Kwang-Myong ; Kim, Jee-Sang ; Jung, Sang-Hwa ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 753~759
To predict service life of concrete structures exposed to chloride attack, surface chloride concentration, diffusion coefficient of chloride ion, and chloride corrosion threshold value in concrete, are used as important factors. Of these, as the diffusion coefficient of chloride ion for concrete is strongly influenced by concrete quality and environmental conditions of structures and may significantly change the service life of structures, it is considered as the most important factor for service life prediction. The qualitative factors affecting the penetration and diffusion of chloride ion into concrete are water-cement (W/C) ratio, age, curing conditions, chloride ion concentration of given environment, wet and dry conditions, etc. In this paper the influence of W/C ratio and curing conditions on the diffusion characteristics of chloride ion in concrete was investigated through the chloride ion diffusion test. In the test, the voltages passing through the diffusion cell were measured by accelerated test method using potential difference, and then with the consideration of IR drop ratio the diffusion coefficient of chloride ion for concrete with different W/C ratios were estimated by Andrade's model. Furthermore, under different curing conditions formulas for the estimation of the diffusion coefficient of chloride ion have been proposed by the regression analysis considering the effect of W/C ratio and age.
Properties on the Strength of Polymer Concrete Using Nano MMT-UP Composite
Jo, Byung-Wan ; Moon, Rin-Gon ; Park, Seung-Kook ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 761~766
Polymer composite are increasingly considered as structural components for use in civil engineering, on account of their enhanced strength-to-weight ratios. Unsaturated polyester (UP) resin have been widely used for the matrix of composites such as FRP and polymer composite, due to its excellent adhesive. Polymer nanocomposites are new class of composites derived from the nano scale inorganic particles with dimensions typically in the range of 1 to 1000 nm that are dispersed in the polymer matrix homogeneously. Owing to the high aspect ratio of the fillers, mechanical, thermal, flame, retardant and barrier properties are enhanced without significant loss of clarity, toughness or impact strength. To prepare the MMT (Montmorillonite)-UP exfoliated nanocomposites, UP was mixed with MMT at
for 3 hours by using pan mixer. XRD (X-ray diffraction) pattern of the composites and TEM (Transmission Electron Micrographs) showed that the interlayer spacing of the modified MMT were exfoliated in polymer matrix. The mechanical properties also supported these findings, since in general, tensile strength, modulus with modified MMT were higher than those of the composites with unmodified MMT. The thermal stability of MMT-UP nanocomposite is better than that of pure UP, and its glass transition temperature is higher than that of pure UP. The polymer concrete made with MMT-UP nanocomposite has better mechanical properties than of pure UP. Therefore, it is suggested that strength and elastic modulus of polymer concrete was found to be positively tensile strength and tensile modulus of the MMT-UP nanocomposites.
Flowability and Strength of Self-compacting Concrete Mixed with Tailings from the Sangdong Tungsten Mine
Choi, Yun Wang ; Kim, Yong Jic ; Jung, Moon Young ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 767~774
This study has focused on the possibility for recycling of tailings from the sangdong tungsten mine as powder (TA) of self-compacting concrete (SCC). The experimental tests for entrapped water ratio were carried out in accordance with the specified method by Okamura. The rheological measurements of cement paste were conducted by using a commercially digital Brookfield viscometer (Model LVDV-II+) equipped with cylindrical spindles, also tests for slump-flow, time required to reach 500 mm of slump flow (sec), time required to flow through V-funnel (sec) and filling height of U-box test (mm) were carried out in accordance with the specified by the Japanese Society of Civil Engineering (JSCE). The results of this study, entrapped water ratio was decreased with increasing replacement of TA. Thickness of pseudo water film was increased, and mean plastic viscosity was decreased with increasing replacement of TA. And slump-flow of SCC was decreased with increasing replacement of TA. But time required to reach 500 mm of slump flow (sec), time required to flow through V-funnel (sec) and filling height of U-box test (mm) were satisfied a prescribed range. The mechanical properties including compressive strength, splitting tensile strength and elastic modulus were checked with the requirements specified by Korean Industrial Standard (KS). The compressive strength of SCC was decreased with increasing replacement of TA, splitting tensile strength and elastic modulus were similar to those of normal concrete.
A Study on Methodology for Improvement of Bond of FRP reinforcement to Concrete
Moon, Do-Young ; Sim, Jongsung ; Oh, Hongseob ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 775~785
This study focused on the development of surface deformations of GFRP rebars with a better bond characteristic for reinforcing concrete, and simultaneously, of GFRP rebars with more simple and economic production process. This research paper describes a development and bond performance of GFRP rebar with molded deformations, which is composed of polymer resin and milled glass fiber. To determine proper mix ration of milled fibers, material test of hardened epoxy and pullout tests of GFRP rebar with various mix ratio were conducted. The test results indicate that the new strategy of using a mixture of epoxy resin and milled fiber could be successfully applied to a surface structure of GFRP rebar to enhance bond with concrete. The bearing resistance of the ribs was further enhanced by the milled fibers at mechanical and environmental loading state.
Shrinkage Properties of High Performance Concrete Used Expansive Additive and Shrinkage Reducing Agent
Koh, Kyung Taek ; Park, Jung Jun ; Ryu, Gum Sung ; Kang, Su Tae ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 787~794
Generally, high performance concrete has characteristics such as low water-cementitious material ratio, lots of unit binder powder, thus the heat of hydration, autogenous shrinkage are tend to be increased. This study is to investigated the effect of the expansive additive and shrinkage reducing agent on the shrinkage properties of high performance concrete as a study to develop the reduction technology of the concrete shrinkage. Test results showed that the expansive additive and shrinkage reducing agent were effective the reduction of shrinkage of high performance concrete. Especially, the using method in combination with expansive additive and shrinkage reducing agent was more effective than the separately using method of that. Also, it analyzed that the combination of expansive additive of 5% and shrinkage reducing agent of 1% was the most suitable mixture, considering to the fluidity, strength and shrinkage properties.
A Numerical Study on the Characteristics of Plastic Shrinkage Cracking on Concrete Slab with Sequential Placement
Kwak, Hyo-Gyoung ; Ha, Soo-Jun ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 795~808
In this paper, an analytical method which can predict the occurrence of plastic shrinkage cracking on concrete slabs with sequential placement is proposed on the basis of the numerical model introduced in the previous study. The influence of many design variables on plastic shrinkage cracking such as the number of layers and the time interval between layers is quantitatively analyzed through parametric studies using the analytical method. In advance, two equations are introduced to take into account the effect of sequential placement on the plastic shrinkage cracking of concrete slab; The first one is to calculate the time at which the surface of concrete slab begins to dry, and the second one is to determine the critical time interval to prevent the surface drying of previously placed concrete layers. The timing of curing and the sequence of concrete placement, which are important for the prevention of plastic shrinkage cracking, can be effectively planned using the introduced both equations without any rigorous analysis.
Detecting Reinforcing Bars under Multi Boundary Layers and Void Shapes in Concrete Using Simulation Analysis Model of Electromagnetic Wave Radar
Park, Seok Kyun ;
Journal of The Korean Society of Civil Engineers, volume 26, issue 4A, 2006, Pages 809~816
More than effectively judging the existence of reinforcing bars under multi boundary layers and void shapes in concrete, this study aims to develop the analysis algorithm of radar response on multi boundary layers in reinforced concrete and radar capable of estimation of the shape of specific voids in plain concrete. To detect or estimate reinforcing bars and void shapes in these conditions, the simulation analysis model of transmission and reflection wave of electromagnetic radar is used. This radar simulation model is carried out with reinforced or non reinforced concrete of various boundary conditions and void shapes. And, the output signals (images) of radar simulation results are calculated and represented by convolution method. As the results, it is clarified that this simulation analysis technique can be used to analyze radar response on multi boundary layers in reinforced concrete and void shapes in concrete.