• Steel and Composite Structures
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• 제31권4호
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• pp.361-372
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• 2019

In recent years, considerable attention has been paid to the research and development of high-strength steel plates, with particular emphasis on the enhancement of the seismic resistance of buildings and bridges. Many efforts have also been undertaken to improve the properties of high-strength bolts and weld materials. However, there are still different opinions on steel joints that combine high-strength bolts and fillet welds. Therefore, it is necessary to verify the design specifications and guidelines, especially for newly developed 1,400-MPa high-strength bolts, 570-MPa steel plates, and weld materials. This paper presents the results of literature reviews and experimental investigations. Test parameters include bolt strengths, weld orientations, and their combinations. The results show that advances in steel materials have increased the plastic deformation capacities of steel welds. That allows combination joints to gain their maximum strength before the welds have fracture failures. When in combination with longitudinal welds, high-strength bolts slip, come in contact with cover plates, and develop greater bearing strength before the joints reach their maximum strength. However, in the case of combinations with transverse welds, changes in crack angles cause the welds to provide additional strength. The combination joints can therefore develop strength greater than estimated by adding the strength of bolted joints in proportion to those of welded joints. Consequently, using the slip resistance as the available strength of high-strength bolts is recommended. That ensures a margin of safety in the strength design of combination joints.

• Structural Engineering and Mechanics
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• 제41권3호
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• pp.407-420
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• 2012

This study investigated possible ways to replace conventional stirrups used on high-strength concrete members with improved reinforcing materials. Headed bar and high-strength steel were chosen to substitute for conventional stirrups, and an experimental comparison between the shear behavior of high-strength concrete large beams reinforced with conventional stirrups and the chosen stirrup substitutes was made. Test results indicated that the headed bar and the high-strength steel led to a significant reserve of shear strength and a good redistribution of shear between stirrups after shear cracking. This is due to the headed bar providing excellent end anchorage and the high-strength steel successfully resisting higher and sudden shear transmission from the concrete to the shear reinforcement. Experimental results presented in this paper were also compared with various prediction models for shear strength of concrete members.

• Steel and Composite Structures
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• 제29권4호
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• pp.509-526
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• 2018

The direct strength method adopted by the AISI Standard and AS/NZS 4600 is an advanced design method meant to substitute the effective width method for the design of cold-formed steel structural members accounting for local instability of thin plate elements. It was proven that the design strength formula for the direct strength method could predict the ultimate strength of medium strength steel welded section compressive and flexural members with local buckling reasonably. This paper focuses on the modification of the direct strength formula for the application to high strength and high performance steel welded section columns which have the nominal yield stress higher than 460 MPa and undergo local buckling, overall buckling or their interaction. The resistance of high strength steel welded H and Box section columns calculated by the proposed direct strength formulae were validated by comparison with various compression test results, FE results, and predictions by existing specifications.

• Advances in concrete construction
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• 제13권6호
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• pp.411-422
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• 2022

Aggregates mineralogical, and petrographic properties directly affect the mechanical properties of the produced high strength. This study is focused on the effects of magmatic, sedimentary, and metamorphic aggregates on the performance of high strength concrete. In this study, the effect of the mineralogical properties of aggregates on the compressive strength and modulus of elasticity of high-strength concrete was estimated by Artifical Neural Network (ANN). To estimate the compressive strength and elasticity modules, 96 test specimens were produced. After 28 days under suitable conditions, tests were carried out to determine the compressive strength and modulus of elasticity of the test specimens. This study also focused on the application of artificial neural networks (ANN) to predict the 28-day compressive strength and the modulus of elasticity of high-strength concrete. An ANN model is developed, trained, and tested by using the available test data obtained from the experimental studies. The ANN model is found to predict the modulus of elasticity, and 28 days compressive strength of high strength concrete well, within the ranges of the input parameters. These comparisons show that ANNs have a strong potential to predict the compressive strength and modulus of elasticity of high-strength concrete over the range of input parameters considered.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2007년도 추계 학술논문 발표대회
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• pp.1-4
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• 2007

Because reinforced concrete structures were being high more and more in recent year, concrete was being demanded high performance of high strength and high fluidity. But various characteristics must be confirmed besides guarantee of demand strength in ultra-high strength concrete. In ultra-high strength concrete, autogenous shrinkage and drying shrinkage grow big because of a low water cement ratio and much quantity of binder. So dangerousness of crack generation grow big in early ages. And ultra-high strength concrete is influenced by use materials more than ordinary strength concrete. In this study we were examined mix design, atuogenous shrinkage and pumpability of ultra-high strength concrete to apply on the ground.

• Earthquakes and Structures
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• 제9권6호
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• pp.1233-1250
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• 2015

The behavior of reinforced concrete (RC) columns made from high strength materials was investigated experimentally. Six high-strength concrete specimen columns (1:4 scale), which included three with high-strength transverse reinforcing bars and three with normal-strength transverse reinforcement, were tested under double curvature bending load. The effects of yielding strength and ratio of transverse reinforcement on the cracking patterns, hysteretic response, shear strength, ductility, strength reduction, energy dissipation and strain of reinforcement were studied. The test results indicated that all specimens failed in splitting failure, and specimens with high-strength transverse reinforcement exhibited better seismic performance than those with normal-strength transverse reinforcement. It also demonstrated that the strength of high-strength lateral reinforcing bars was fully utilized at the ultimate displacements. Shear strength formula of short concrete columns, which experienced a splitting failure, was proposed based on the Chinese concrete code. To enhance the applicability of the model, it was corroborated with 47 short concrete columns selected from the literature available. The results indicated that, the proposed method can give better predictions of shear strength for short columns that experienced a splitting failure than other shear strength models of ACI 318 and Chinese concrete codes.

• Journal of Welding and Joining
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• 제22권4호
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• pp.50-58
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• 2004

In this study, high temperature tensile properties of high strength steels(POSTEN60, POSTEN80) were investigated. The three-dimensional thermal elastic-plastic analyses were conducted to investigate the characteristics of welding residual stresses in welds of high strength steels on the basis of thermal and mechanical properites at high temperature obtained from the experiment. According to the results, high temperature tensile strength of POSTEN60 steel deteriorated slowly to 10$0^{\circ}C$. As the temperature went up, the tensile strength became better because of blue shortness, and it deteriorated radically after reaching to the maximum value around 30$0^{\circ}C$. For the POSTEN80 steel, high temperature tensile strength deteriorated slowly to 20$0^{\circ}C$. As the temperature went up the tensile strength became better and it deteriorated slowly to $600^{\circ}C$ after reached to the maximum value around 30$0^{\circ}C$. Strain of high strength steels at the elevated temperature increased radically after the mercury rose to $600^{\circ}C$. The strain hardening ratio of POSTEN60 steel was larger then that of POSTEN80 steel at the elevated temperature as in the case at the room temperature and it became smaller radically after the mercury rose to 40$0^{\circ}C$. And, in the welding of high strength steels, increasing tensile strength of the steel (POSTEN60

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1992년도 가을 학술발표회 논문집
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• pp.100-105
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• 1992

While there are many researches in high-strength concrete recently, average strength required is the level of 400kg/$\textrm{cm}^2$ 28days compressive strength yet. For the effective using of high strength concrete, high strength concrete of 600 to 800kg/$\textrm{cm}^2$ 28days compressive strength must be accepted, But in this high strength concrete, due to much cement content, there are the problems of high hydration heat, high viscosity and economical efficiency. To solve these problems, it is suggested the method that replacement some of cement content as flyash up-to-dately. Therefore, the aim of this study is to develop high strength concrete of 800kg/$\textrm{cm}^2$ 28days compressive strength containing fly ash. This paper is the part I that analyze the testing results of fresh concrete in various aspects.

• Journal of Welding and Joining
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• 제12권3호
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• pp.56-62
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• 1994

The spot weldability of high strength steel sheet and two stories galvannealed high strength steel sheet has been studied. 1) Tensile shear strength decreased inversely as welding current increased over 12KA in the case of two stories galvannealed high strength steel sheet. 2) When heat flux input over 12KA, hardening region become narrow in case of two stories galvannealed high strength steel sheet. 3) The size of hardening region affect the strength of nuggets.

• Architectural research
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• 제15권1호
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• pp.53-58
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• 2013

High strength concrete is being used increasingly in mass structure projects. The purpose of this study is to investigate the influence of temperature during mixing, placing and curing on the strength development, hydration products and pore structures of high strength concrete in mass structures. The experiments were conducted with two different model walls, viz.: 1.5 m and 0.3 m under typical summer and winter weather conditions. The final part of this study deal with the clarification of the relationship between the long-term strength loss and the microstructure of the high strength concrete at high temperatures. Test results indicated that high elevated temperatures in mass concrete structures significantly accelerate the strength development of concrete at the early ages, while the long-term strength development is decreased. The long-term strength loss is caused by the decomposition of ettringite and increased the total porosity and amount of small pores.