This study was conducted to evaluate strength characteristics of various polymer concretes which were produced using materials available in Korea. Compressive strength, splitting tensile strength and flexural strength were evaluated in this study. Eight different polymer binders were used, including two types of epoxy resin, five types of unsaturated polyester resin, and a type of MMA monomer. The results of this study showed that the product made from PC-100 of SH company was the best performing concrete. However, since this result was based on strength and economics point of view, further study has to be conducted for comprehensive analysis.

There are two main methods in reinforcing cements with glass fibers : spray-suction and premixing method. But GRC have been mostly studied by spray technique. In order to develop GRC made by premixing method, in this paper, the influence of glass fiber length, volume content and curing conditions upon the compressive, direct tensile and bending strengths of composites fabricated by a premixing method, were investigated. According to the test results, although it was difficult to obtain perfectly uniform distribution of fibers in GRC Pannel, it was found that tensile strength of cements with glass fiber was improved 2~5 times and flexural strength 4 times compared to conventional cement mortar upto fiber length 35 mm, volume content 4%.

Results of an experimental study on the manufacture and the mechanical properties of carbon fiber reinforced fly ash-cement composites are presented in this paper. The carbon fiber reinforced fly ash-cement composites using silica powder and a small amount of Ethylene vinyl acetate emulsion are prepared with carbon fiber, foaming agents and curing conditions. As a result, the manufacturing process technology of carbon fiber reinforced fly ash-cement composites is developed. And the mechanical properties such as compressive, tensile and flexural strengths and drying shrinkage of lightweight carbon fiber reinforced fly ash-cement composites are improved by using a small amount of Ethylene vinyle acetate emulsion. The development and applications of precast products and the design systems of lightweight carbon fiber reinforced fly ash-cement composites are expected in the near future.

The effect of superplasticizers on the fluidity performance in fresh concrete and physical properties in hardened concrete have been analyzed and investigated under mix proportions of water cement ratio of 0.4, 0.6, crushed stone aggregates, and addition rates of superplasticizers of 0.0, 0.5, 1.0 and 1.5 in the practical range. It is the aim of this study to provide the fundamental data on the workability improvement and engineering properties of crushed stone concrete using superplasticizers comparing with conventional concrete for the practical use and research data accumulation of superplastized concrete.

In order to evaluate the difference of testing results in the standards on the compressive strength of various countries, we have compared the testing results of the compressive and flexural strength, one of the most important properties of cement, obtained on the various standards(KS, JIS, BS, ASTM) and the statistical method was used to evaluate the results.

The purpose of this study is to examine through the experimental study whether the water cooled unprocessed blast furnace slag produced in the country is useful for the fine aggregate of concrete or not. The results of this study show that the quality of the water cooled blast furnace slag is inferior to that of natural river sand and that the concrete made by substituting the water cooled blast furnace slag for fine aggregate have a tendency to decrease to some extent in strength. But if the water cooled blast furnace slag is transformed into more hardened state material, to use it as the fine aggregate of concrete will be possible.

Energy cries and availability have funded extensive research and numerous conferences. So, the idea of adding slags and pozzolans such as flyash to portland cement or portland cement concrete is widely practiced because it helps to reduce cost and conserve energy, resources and the environment. Recently, Silicafume which is the industrial by-product of electric arc furnaces is also widely studied for achieving high strength concrete. It is the aim of this study to provide the fundamental data on the workability and engineering proper of high strength concrete containing flyash and silica fume comparing with plain concrete for the practical use and research data accumulation of a new technique for achieving high strength concrete.

Depths of the vertical cracks in the concrete were determined by the time of flight of the ultrasonic waves. The ultrasonic waves are diffracted at the crack tip, and the arrival time of ultrasonic waves are dependent on the crack depth and speration distance between transmitting and receiving ultrasonic transducers. The vertical cracks with 0.2-2mm width and 10-100mm depth were examined by multi-layered ultrasonic transducers. It was found that the time of flight of ultrasonic waves were proportional to the depth of vertical cracks. The depth of vertical cracks in the range of 20-100mm depth could be determined by the transient time of the diffracted ultrasonic waves

This experimental study is performed by using artificial lightweight aggregate manufactured in laboratory, and the test results of it are compared with those using foreign materials in respect of design compressive strength, unit weight. The tests on strength characteristics such as bending, splitting tensile strength and on mechanical characteristics including σ-εcurve, elastic modulus, poisson's ratio are performed to provide the fundamental data required for the design. From this study, it is possible to obtain the high-strength concrete having compressive strength of 500 kg/㎠ and unit weight of 1.85-2.0 t/㎥. And also it is recommended that sandlightweight concrete having high specfic strength is more practical for general use.

The purpose of this study was to find, through field and questionaire survey, the problems in arrngement of reinforcing bars in wall-slab type apartment buildings. The survey was done in 88 construction sites over the country. The findings from the survey were as followed : (1) reinforcement details were unnecessarily complex in some structural members and could be simplified without sacrificing the safety of the structures; (2) It was found in many cases that drawings of reiforcement failed to show the location of the laps, bent-up positions, and the development length; and (3) it was often found that the workers did not understand the importance of tloerence limits and anchorage in the steel bar arrangement.

Investigations on the behavior of steel fiber reinforced high strength concrete beams subjected to predominant shear are accomplished to determine their diagonal shear strength including ultimate shear strength. The parameters varied were the volume fraction(Vf) of the fibers, shear span depth ratio(a/d). The test result show that diagonal shear strength and ultimate shear strength are increased siginificantly due to crack arrest mechanism. Predictive equations are suggested for evaluating the diagonal cracking strength and ultimate shear strength of the fiber reinforced high strength concrete beams.

The purpose of this report is to study the traffic opening day of concrete pavement. For this purpose this paper studies on the propeties of various cement types which include the newly developed cement for the cement pavement regarding the resistance to the chemical attack caused by de-icing salt and the durability of the concrete pavement. Especially, traffic opening day of concrete pavement are discussed on site.

The purpose of this study was to investigate the effect of Bent-up Bars in Beam-Column Joint with High-Strength Concrete up to 800 kg/$\textrm{cm}^2$. 5 specimens were tested under reversed cyclic loadings. The primary variables were the number of the Bented Bars with Joint Core, compressive strength and loading patterrns. The results showed that bent-up bars in beam-column joint prevented crack from extending into core but the failure was concreterated at the face of beam-column joint. Thus shear stress constant value(Г) should be revised for High Strength Concrete Beam-Column Joint with Bent-up Bars.

The prediction and estimation of R/C structure behavior subjected to earthquake type loading is partly based on the experimental results of the monotonically increased cyclic loading, rather than that of the irregularly increased cyclic loading. However, actual earthquake is typical random vibration. In this respect, comparing and analysing experimental test results of R/C specimens subjected to monotonically increased cyclic loading and irregularly increased cyclic loading, this study proposes the research direction of irregularly increased cyclic loading during earthquake.

Results are presented of the cyclic loading tests of there low-rise shear wall assembligies using high strength concrete. The possibilities of achieving an acceptable level of energy dissipation in one story shear walls, mainly by flexural yielding, are examined. Mechanisms of flexural and shear resistance are reviewed with emphasis on aspects of sliding shear. Detrimental effects of sliding shear are demonstrated together with improvement achieved by use of diagonal wall reinforcements. It is postulated that with suitably arranged diagonal wall reinforcements a predominantly flexural response mode with good energy dissipation characteristics can be achieved in low-rise shear walls.

The current analytical techniques for R/C elements under severe dynamic repeated loads, like earthquake or impact, has two major problems; one is that the effects of strain rate are not considered and the other one is the current model was developed based on flexural behavior only. Thus, this study develops a computer software that can idealize the flexural and shear behavior of R/C elements using several parameters and also can consider the effects of strain rate. The analytical results using the developed analytical technique were compared with several experimental results and were generally satisfied.

The objective of this study is to optimize the section of RC box culvert and develop a CAD system for drawing. This paper consists of three parts. In the first part, the external load conditions are systematized by using the literatures and specifications. In the second one, the RC box culvert is optimized using the SUMT algorithm. Sizing variables, and steel ratio are taken as design variables, and a cost function as the objective function. The stress and side constraints are derived from the Korea Concrete Specifications for the ultimate strength design. Finally, a data base and CAD system is developed for the drawing of the optimized section of RC box culverts.

It is widely recognized that the strengths of reinforced concrete members have random characteristics due to the variability of the mechanical properties of concrete and steel, the dimensional error as well as incorrect placement of reinforcing bars. Statistical models of the variabilities of strengths of reinforced concrete members, therefore, need to be developed to evaluate the safety level implied in current practices. Based on the probabilistic models of basic factors affecting the R.C. member strengths, in this study, the probabilistic characteristics of member resistance have been studied through Monte Carlo simulation.

본 논문은 반복하중에 의한 콘크리트 부재거동에 대한 수학적인 해석방법에 관한 것으로서 철근콘크리트 부재의 Hysteretic 거동의 주요한 현상들인 강성저하, 강도저하 그리고 전단영향 등의 수치해석 Model을 소개하였다. 그리고 본 해석 Model의 정확성 및 사용성 등을 평가하기 위하여 R.C.콘크리트 부재에 대한 수치 해석 예제를 제시하였다.

The research program is directed at studying the behavior and the strength of reinforced concrete slabs subjected to certain combination of punching shear and in-plane tension. Major variables to be investigated are the shear span to depth ratio of reinforced concrete slabs and the degree of the in-plane tensile force which is acting tangent to the slabs. The experimental results are used for understanding of the degree of the interaction between the two loadings, and for developing a new practical design equation.

This paper contains experimental studies on the flexural cracking behabior of PPC one-way slabs. Three post tensioned bonded PPC slabs with the same prestressing ratio and ultimate moment strength were tested. Based upon test results, this paper also presents the crack width prediction formula PPC slab. According to the crack theory developed mainly in Europe, crack width formula is given as the product of crack spacing and mean steel strain after decompression. Aaaaverage crack spacing formula is composed of many factors mainly such as concrete cover, concrete effective area in tension, sum of reinforcing bars perimeters and mixed reinforcements. In particular, it is very important to specify the bond characteristics of mixed reinforcements, since bond characteristics of PC bars are different from those of non-tensioned deformed bars. For this reason, a reduced bond coefficients for PS bars is employed in this study.

Baxed on the results tested by various researchers, a complete stress-strain relation of plain and confined concrete is proposed. The peak strength and the corresponding strain are calculated by using the Mohr-Coulomb theory and elastic tri-axial constitutive relation. A parametric study was conducted to assess the influence of the plain concrete strength, the degree of confinement, the shape of the section, and the tie configuration for the square section. According to this model, the behavior of concrete section is predicted, and compared with experimental data and other proposed models on circular and square sections. A good agreement between theoretical and experimental results is observed.

The transfer of forces across the interface by bond between concrete and steel is of fundamental importance to many aspects of reinforced concrete behavior. Bond stress - slip relationships were studied using a symmetrical tension test specimen. This type of test is intented to simulate conditions in the tension zone of a concrete beam between primary cracks and below the neutral axis. These relationships between local bond stress and local slip are quite different at different locations along the bar. The present study allows more accurate analysis of reinforced concrete structures by employing more realistic bond stress-slip relations.