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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korea Concrete Institute
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Journal DOI :
Korea Concrete Institute
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Volume & Issues
Volume 11, Issue 6 - Dec 1999
Volume 11, Issue 5 - Oct 1999
Volume 11, Issue 4 - Aug 1999
Volume 11, Issue 3 - Jun 1999
Volume 11, Issue 2 - 00 1999
Volume 11, Issue 1 - 00 1999
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An Effects of Lateral Reinforcement of High-Strength R/C Columns Subjected to Reversed Cyclic and High-Axail Force
Journal of the Korea Concrete Institute, volume 11, issue 5, 1999, Pages 3~10
DOI : 10.22636/JKCI.19126.96.36.199
Earthquake resistant R/C frame structures are generally designed to prevent the columns from plastic hinging. R/C columns under higher axial load or strong earthquake showed a brittle behavior due to the deterioration of strength and stiffness degradation. An experimental study was conducted to examine the behavior and to find the relationship between amounts of lateral reinforcements and compressive strength of ten R/C column specimens subjected to reversed cyclic lateral load and higher axial load. Test results are follows : An increase in the amount of lateral reinforcement results in a significant improvement in both ductility and energy dissipation capacities of columns. R/C columns with sub-tie provide the improved ductility capacity than those with closely spaced lateral reinforcement only. While the load resisting capacity of the high strength R/C columns is higher than the normal strength concrete columns under both an identical ratio of lateral reinforcement, however the ductility capacity of high strength R/C columns is decreased considerably. Therefore, the amounts of lateral reinforcement must be designed carefully to secure the sufficient ductility and economic design of HSC columns under higher axial load.
Behaviors of PSC-Beam Bridges According to Continuity of Spans (1)
Journal of the Korea Concrete Institute, volume 11, issue 5, 1999, Pages 11~20
DOI : 10.22636/JKCI.19188.8.131.52
This paper deals with behaviors of PSC-Beam bridges according to continuity of spans. To analyze the long-term behavior of bridges, an analytical model which can simulate the effects of creep, the shrinkage of concrete, and the cracking of concrete slabs in the negative moment regions is introduced. To consider the different material properties across the sectional depth, the layer approach in which a section is divided into imaginary concrete and steel layers is adopted. The element stiffness matrix is constructed according to the assumed displacement field formulation, and the creep and shrinkage effects of concrete are considered in accordance with the first-order algorithm based on the expansion of the creep compliance. Correlation studies between analytical and experimental results are conducted with the objective to establish the validity of the proposed model. Besides, many uncertainties related to the continuity of spans are analyzed to minimize deck cracking at interior supports.
Behaviors of PSC-Beam Bridges According to Continuity of Spans (2)
Journal of the Korea Concrete Institute, volume 11, issue 5, 1999, Pages 21~31
DOI : 10.22636/JKCI.19184.108.40.206
The companion paper presents an analytical model to predict behaviors of PSC-Beam bridges according to continuity of spans. This paper aims at providing several examples of its application to PSC-Beam bridge. In this regard, many uncertainties affecting to the continuity of spans (such as the ultimate shrinkage strain of slab and girders, the prestressing creep of girders, and the time adopting prestressing force) are analysis in detail. Moreover, to increase the serviceability and to remove th inherent structural defects including the cracking at interior supports, a necessity for the parametric studies of PSC-Beam bridges reflecting the construction sequence is emphasized.
An Improved Finite Element Modeling Technique for Prestressed Concrete Girder Bridges
Journal of the Korea Concrete Institute, volume 11, issue 5, 1999, Pages 33~40
DOI : 10.22636/JKCI.19220.127.116.11
An improved finite element modeling technique is proposed for the assessment of load carrying capacity of partially prestressed concrete girder bridges. Based on the finite element method of analysis, shell and frame elements are used to model the slab and girders of the superstructure, respectively. In the modeling of superstructure, the emphasis is placed on the use of rigid link between the middle surface of slab an mid-plane of girder. This paper also includes the comparision of three different equations that are used in the calculation of effective moment of inertia for the partially prestressed concrete girders. Numerical analysis is performed for the unstrengthened and strengthened bridges. The obtained results are compared with those of load test for a prototype bridge. A good agreement is achieved between the numerical solutions by using the proposed method load test results.
A Study on the Application in Site of the Concrete Using Fly Ash Produced in Combined Heat Power Plant
Journal of the Korea Concrete Institute, volume 11, issue 5, 1999, Pages 41~49
DOI : 10.22636/JKCI.1918.104.22.168
This study dealt with the applicability and quality control of the concrete using fly ash produced in combined heat power in a construction site. Firstly, chemical and physical characteristics of the fly ash produced in combined heat power plant re analysed. Also, after investigating the properties of flesh and hardened concrete through various experiments, the fly ash concrete was placed in depositing construction in Ulsan Petrochemical Service Co. This field application was focussed on the quality control system in the site as production, placing and curing of concrete. As the result of this study, the quantity of CaO in the fly ash is relatively high based on the chemical analysis. The fly ash concrete showed slumping maintenance and high viscosity properties in the optimal mixing conditions (W/B:44~45%, S/a:
2%, W:185kg/m). And, quality control and assurance of the fly ash concrete in actual site were verified by various testing methods.
An Experimental Studies on Properties of Antiwashout Admixtures
Journal of the Korea Concrete Institute, volume 11, issue 5, 1999, Pages 51~60
DOI : 10.22636/JKCI.1922.214.171.124
When placed under water, concrete is diluted with separating cementitious material and as a result the quality of concrete becomes poor. So as to solve the problem, underwater concrete is increasingly used for the construction and repair of the concrete structure under water. In this paper, 4 kinds of antiwashout admixtures and varying sand percentages were chosen to measure the suspended solids, pH, air contents, setting time and compressive strength of underwater concrete, and they meet "Standard for antiwashout admixture used for concrete". When sand percentage is 43%, the fluidity and filling of underwater concrete are superior to the others.he others.
Proposed Design Provisions for Bond and Development Length Considering Effects of Confinement
Journal of the Korea Concrete Institute, volume 11, issue 5, 1999, Pages 61~68
DOI : 10.22636/JKCI.19126.96.36.199
Confinement is one of the major concepts for bond of reinforcing steel to concrete. Cover distance, and lateral reinforcement are the key factors for current provisions for development and splices of reinforcement. However, the current provisions still being complicated to calculate major variables need to be developed in the process of design. In this study, an experimental work was performed to examine the behavior of bond using beam end specimens. The test results and previous available data are analyzed to isolate the effects of confinement on bond strength. From this reevaluation, new provisions for development and splice of reinforcement are proposed. The provisions also propose some limits for confinement index. The new provisions will help engineers to decide easily the simple but conservative way for manual calculations or the exact approach for computerized design.
A Study on the Spalling Properties of High-Performance Concrete with the Kinds of Aggregate and Polypropylene Fiber Contents
Journal of the Korea Concrete Institute, volume 11, issue 5, 1999, Pages 69~77
DOI : 10.22636/JKCI.19188.8.131.52
A spalling is defined as the damages of concrete exposed to high temperature during the fire by causing cracks and localized bursting of small pieces of concrete. It is reported that spalling is caused by the vapor pressure and polypropylene(PP) fiber has an important role in protecting from spalling. This paper is a study on the properties and spalling resistance of high-performance concrete with the kinds of aggregate and the contents of PP fiber. According to the experimental results, concrete contained no PP fiber take place in the form of the surface spalling and the failure of specimenns after fire test regardless of the kinds of aggregate. Concrete contained more than 0.05% of PP fiber with the aggregate of basalt does not take place the spalling, while the concrete using granite and limestone does the surface spalling. It is found that residual compressive strength after exposed at high temperature has 50~60% of its original strength. Although specimens after exposed at high temperature is cured at water for 28days, they do not recover their original strength.
Theoretical Stiffness of Cracked Reinforced Concrete Elements
Journal of the Korea Concrete Institute, volume 11, issue 5, 1999, Pages 79~88
DOI : 10.22636/JKCI.19184.108.40.206
The purpose of this paper is to develop a mathematical expression for computing crack angles based on reinforcement volumes in the longitudinal and transverse directions, member end-fixity and length-to-width aspect ratio. For this a reinforced concrete beam-column element is assumed to possess a series of potential crack planes represented by a number of differential truss elements. Depending on the boundary condition, a constant angle truss or a variable angle truss is employed to model the cracked structural concrete member. The truss models are then analyzed using the virtual work method of analysis to relate forces and deformations. Rigorous and simplified solution schemes are presented. An equation to estimate the theoretical crack angle is derived by considering the energy minimization on the virtual work done over both the shear and flexural components the energy minimization on the virtual work done over both the shear and flexural components of truss models. The crack angle in this study is defined as the steepest one among fan-shaped angles measured from the longitudinal axis of the member to the diagonal crack. The theoretical crack angle predictions are validated against experimentally observed crack angle reported by previous researchers in the literature. Good agreement between theory and experiment is obtained.
Deformation Demand of the Precast Concrete Frame Buildings with Ductile Connection in Moderate Seismic Regions
Journal of the Korea Concrete Institute, volume 11, issue 5, 1999, Pages 89~98
DOI : 10.22636/JKCI.19220.127.116.11
This paper evaluates nonlinear response characteristics of precast concrete frame buildings. where plastics hinging occurs in the precast connection. Designs were developed for buildings of 5, 10 and 15 stories in hight for moderate seismic risk regions of the U. S. The responses of the buildings were analyzed using DRAIN-2DX and following Nonlinear static analysis procedure of ATC 19. The main variables of the analyses were the strength and stiffness of the connection. Also, for the analysis, the bi-linear response model, developed and inserted into the DRAIN-2DX program by Shan Shi and D. Fouch, was used. With the results of analysis, the deformation demands of the connection of precast concrete frame buildings are proposed by using equal-dissipated energy capacity. It was shown that the strength of the buildings as well as their displacement capacities decreased with the decrease of either the strength or stiffness in the connections. Therefore such changes also require reductions in the response modification factors for such buildings. However, if the precast concrete frame building has plastic hinging in the connection, and has a more ductile connection than the monolithic frame building, then no reduction in R may be necessary. The deformation demand required of the connection to achieve that condition is evaluated and a simple relation is suggested in the paper.
Improvement of Properties of High Strength Concrete Using Fly Ash and Gypsum
Journal of the Korea Concrete Institute, volume 11, issue 5, 1999, Pages 99~105
DOI : 10.22636/JKCI.1918.104.22.168
In producing high strength concrete, the most practical method is to use high range water reducing admixture(HRWR). Workabili쇼 of concrete using HRWR varies rapidly with elapsed time after mixing. Effects of fly ash and gypsum on slump loss and compressive strength of concrete were examined by experiment in this study. The slump loss of high strength concrete was reduced with increase of substitution ratio of fly ash. When 2~4% gypsum of cement weight was applied, the reduction of slump loss was not prominent and strength increase appeared at all test ages.
Quasi-Static Test for Seismic Performance of Circular R.C. Bridge Piers Before and After Retrofitting
Journal of the Korea Concrete Institute, volume 11, issue 5, 1999, Pages 107~118
DOI : 10.22636/JKCI.1922.214.171.124
10 RC bridge piers have been made on a 1/3.4 scale model, and six piers of them were retrofitted with glassfiber. The have been tested in the quasi-static cyclic load so as to investigate their seismic enhancement before and after retrofitting with glassfibers. The objective of this experimental study is to investigate how to strength the ductility of reinforced concrete bridge piers which have been nonseismically designed and constructed in Korea before 1992. Important test parameters are axial load, load pattern, retrofit type. Glassfiber sheets were used for retrofitting in the plastic hinge region of concrete piers. The nonlinear behavior of bridge columns have been evaluated through their yield and ultimate strength, energy dissipation, displacement ductility and load-deflection characteristics under quasi-static cyclic loads. It can be concluded from the test that concrete piers strengthened with glassfibers have been enhanced for their ductile behavior by approximate 50%.
A Study on Shear-Fatigue Behavior of Reinforced Concrete Beams using High Strength Concrete
Journal of the Korea Concrete Institute, volume 11, issue 5, 1999, Pages 119~130
DOI : 10.22636/JKCI.19126.96.36.199
Recently, as the building structure has been larger, higher, longer and more specialized, the demand of material with high-strength concrete for building has been increasing. In this research, silica-fume was used as an admixture in order to get a high-strength concrete. From the test result, High-strength concrete with cylinder strength of 1,200kgf/
in 28-days was produced and tested. The static test was carried out to measure the ultimate load, the initial load of flexural and diagonal cracking, crack patterns and fracture modes. The load versus strain and load versus deflection relations were obtained from the static test. The relation of cycle loading to deflections on the mid-span, the crack propagation and the modes of failure according to cycle number, fatigue life and S-N curve were observed through the fatigue test. Based on the fatigue test results, high-strength reinforced concrete beams failed to 57~66 percent of the static ultimate strength. Fatigue strength about two million cycles from S-N curves was certified by 60 percent of static ultimate strength.
Analytical Modeling for Reinforced Concrete Beam Deflections Using Layered Finite Elements
Journal of the Korea Concrete Institute, volume 11, issue 5, 1999, Pages 131~137
DOI : 10.22636/JKCI.19188.8.131.52
The use of higher strength materials with the strength methed of design has resulted in more slender member and shallower sections. For this reason, it is necessary to satisfy the requirements of serviceability even though the structural safety is the most important limit state. This paper is only concerned with the control of deflections in the serviceability. In this study, an analytical model is presented to predict the deflections of reinforced concrete beams to given loading and environmental conditions. This model is based on the finite element approach in which a finite element is generally divided into a number of stiffening effect due to cracking, creep and shrinkage. Comparisons are made with available measured deflections reported by others to assess the capability of the layered beam model. The calculated values of instantaneous and long-term deflection show good agreement with experimental results in the range of tension stiffening parameter
between 2.5 and 3.0.