Recent Research Advances of High Strength Steel Structures and Codification of Design Specification in China

Gang Shi,Fangxin Hu,Yong-Jiu Shi 한국강구조학회 2014 International Journal of Steel Structures Vol.14 No.4

High strength steel (HSS) with the nominal yield strength fy≥460 MPa has been applied in numerous modern building andbridge structures all over the world. Steel structures using high strength steel have obvious advantages in structural,architectural, economical, environment protection and energy saving aspects. After a brief introduction of early studies, recentresearch advances of high strength steel structures in Tsinghua University in China are comprehensively reviewed. Systematicinvestigations have been carried out on static- and cyclic-loading behavior of high strength steels and their welded connections,residual stress of high strength steel hot-rolled and welded sections, overall and local buckling behavior of high strength steelcolumns under axial compression, seismic behavior of high strength steel columns under combined bending and compression,bearing and slip resistance of bolted connections with high strength steel slices. The research results show that mechanicalbehavior of high strength steel structures has been improved much compared with ordinary strength steel structures, so thedesign methods in current design codes or specifications need be updated to be applicable to high strength steel structures. Therefore, as the chief-editor institute, Tsinghua University has organized 34 institutes including universities, design andresearch institutes, steel structure fabricators, and steel manufacturers, to codify a new code, i.e. Design Specification of HighStrength Steel Structures in China. Based on the above research results, new design methods and calculation formulaeapplicable to high strength steel structures are incorporated into this design specification. The outline of this specification isdiscussed in detail in this paper.

특이적 웨이트 트레이닝이 국가대표 레슬링 자유형 선수들의 근기능에 미치는 영향

노재현,송홍선 국민체육진흥공단 한국스포츠정책과학원 2019 체육과학연구 Vol.30 No.3

[Purpose] The purpose of this study was to identify the effect of a power-specific weight training program in order to improve the muscle strength of Korean national team’s freestyle wrestlers. [Methods] Participants were 13 male athletes in the national freestyle wrestling team. The period of the program was 6 weeks. Muscle strength, muscular endurance, muscle power, flexibility, agility, cardiorespiratory endurance, anaerobic power and isokinetic muscle function were measured. Data were analyzed using IBM SPSS Statistics ver. 23.0 (IBM Co., Armonk, NY, USA). Paired t-test was conducted for comparison between pre-test and post-test score. [Results] There were significant difference and tendency in the leg isokinetic power and trunk isokinetic flexion strength. However, there was no significant difference in muscle strength, muscular endurance, muscle power, flexibility, agility and cardiorespiratory endurance. [Conclusion] The 6-week program focusing on the power-specific weight training indicated a significant difference not in every variable but in isokinetic muscle power, speed power and core strength. It is suggested that the training program was applied to the athletes less continuously and not in the long term because of frequent international games abroad and the need for losing weight. Consequently, a year-long training program with personalized methods should be developed to bring about more significant outcomes. [목적] 본 연구는 국가대표 레슬링 선수들의 경기력 향상을 위해 특이적 웨이트 프로그램을 개발하고 적용하여 그 효과를 살펴보는데 있었다. [방법] 연구의 방법은 2019년 국가대표 선발전을 거쳐 선수촌에서 훈련 중인 남자 레슬링 자유형 국가대표 선수 13명을 대상으로 특이적 웨이트 프로그램을 6주간 적용하였으며, 신체 구성과 체력적 요인(근력, 근지구력, 근파워, 유연성, 민첩성, 심폐지구력, 무산소성파워, 등속성 근기능)을 프로그램 적용 전, 후로 측정하였다. 데이터는 IBM SPSS 23.0을 사용하여 변인들의 사전과 사후 값을 비교 분석한 후 전, 후 차이를 종속 t-검증(paired t-test)을 이용해 실시 및 평가하였으며 α=.05 수준에서 통계적 유의성을 검증하였다. [결과] 그 결과 무릎 등속성 각근파워 우측 신근에서 유의한 차이와 긍정적인 변화가 있었고, 허리 등속성 각근력 굴근에서 유의한 차이가 있었다.그러나 근력(악력, 배근력), 근지구력(윗몸일으키기, 반복점프), 근파워(제자리멀리뛰기), 유연성(장좌체전굴, 체후굴), 민첩성(사이드스텝, 반응시간), 심폐지구력(셔틀런)에서는 유의한 차이가 나타나지 않았다. [결론] 6주간 특이적 웨이트 프로그램을 적용한 결과 모든 항목에서 큰 차이를 보이지 않았지만, 등속성 파워근력과 스피드파워, 코어근력에서 유의한 차이를 보였다. 트레이닝 프로그램 적용 시 국가대표로서 잦은 국외 시합 일정과 그에 따른 체중감량으로 인해 지속적 및 장기간의 트레이닝이 적용되지 못한 한계점이 존재한다. 추후 연간 훈련 프로그램을 적용과 개인의 특성에 맞은 훈련프로그램 적용시킨다면 보다 유의미한 결과를 나타낼 수 있을 것으로 사료된다.

열간 압연 후 어닐링처리한 Mg 합금의 인장강도와 감쇠능과의 관계

이규현 ( Gyu Hyun Lee ),오은지 ( Eun Ji Oh ),김권후 ( Kwon Hoo Kim ),김재남 ( Jae Nam Kim ),강창룡 ( Chang Yong Kang ) 한국열처리공학회 2014 熱處理工學會誌 Vol.27 No.6

In this study, the relationship between strength and damping capacity of annealed magnesium alloysafter hot rolling was investigated. The microstructure of hot rolled magnesium consisted of dendrite structure andMg17Al12 compounds precipitated along the grain boundary. The dendrite structure was dissipated, Mg17Al12 compoundswas decomposed by annealing, and then its dissolved in α-Mg. With an increasing the annealing temperatureand time, strength was slowly decreased and damping capacity was slowly increased by the growth of grainsize and decreasing of defects induced by hot rolling. In annealing treatmented magnesium alloys after hot rolling,damping capacity was decreased rapidly with an increase of strength. There was on proportional relationshipbetween tensile strength, and damping capacity.

학교체육시설물-철봉의 강도규정 및 이의 평가방법 개발에 관한 연구

강기원 ( Ki Weon Kang ),안병화 ( Byoung Hwa Ahn ),유승원 ( Sueng Won You ),도영민 ( Young Min Do ) 한국스포츠정책과학원(구 한국스포츠개발원) 2003 체육과학연구 Vol.14 No.1

학교체육시설물의 안전성 및 효율성을 향상시키기 위해서는 이의 구체적인 요건을 정하는 표준규격의 제정이 요구된다. 이러한 표준 규격은 품질규정, 형상규정 및 강도규정 등으로 세분화될 수 있으며 이 중 표준 규격의 핵심요소인 강도규정은 학교체육시설물이 보유하여야 하는 기준강도에 대한 내용을 포함하므로 이의 적합한 설정은 매우 중요하다. 또한 이와 같이 설정된 강도규정의 타당성 및 적합성을 검증하기 위해서는 강도규정에 대한 시험방법의 선정 역시 매우 중요하다. 그러나 철봉으로 대표되는 학교체육시설물은 대부분 운동장과 같은 야외에 설치·운영되고 또한 이의 운동형태가 매우 다양하므로 기존의 시험방법으로는 이에 대한 시험평가가 매우 어려운 실정이다. 따라서 본 논문에서는 대표적인 학교체육시설물인 야외용 철봉의 강도규정 및 이의 평가를 위한 시험방법을 제정하고 이들의 적합성 및 타당성 검증에 대한 연구를 수행하였다. The present study is aiming at developing the strength specification and evaluation methodology in horizontal bars intended for permanent installation for use at elementary, middle and high schools. For these purpose, the strength specification is, firstly, established through the structural analysis considering the environmental, service and loading conditions of horizontal bars. Additionally, an evaluation methodology is developed to identify the usefulness and conformity of the strength specification. And then this study ends with the tests for prototype of horizontal bars according to the strength specification and evaluation methodology through a portable universal testing machine, which is designed to be able to adjust the loading direction and operate outdoors.

내부에 피라미드 구조를 가지는 ISB 판넬의 정적 특성 분석

안동규,이상훈,김민수,한길영,김진석,정창균,양동열 한국공작기계학회 2005 한국공작기계학회 춘계학술대회논문집 Vol.2005 No.-

The objective of this research work is to investigate into static characteristics of ISB panels with the pyramidal structure as a internally structured material. In order to investigate the behavior of material deformation and frracture characteristics, several tensile tests have been carried out for the ISB panel and skin sheet. Through the results of the experiments, the mechanical properties of ISB panel and skin sheet and fracture characteristics have been obtained. In addition, the mechaical properties of the ISB panel have been compared with that of the skin sheet by the view point of a specific modulus, a specific yield strength and a specific strength. From the results of the comparision, it has been shown that the ISB panel has an excellent static characteristics.

듀플렉스계 스테인리스강 2행 2열 볼트접합부의 구조거동에 관한 실험적 연구

강현식,김태수 한국강구조학회 2019 韓國鋼構造學會 論文集 Vol.31 No.1

Recently, duplex stainless steel with higher strength, greater corrosion resistance (particularly, stress corrosion cracking) and lower cost compared with austenitic stainless steel has been developed. However, stainless steels are not included in the structural materials of Korean Building Code(KBC) and corresponding design specifications are not regulated. In this paper, experimental studies have been performed to investigate the structural behaviors of duplex stainless steel (STS329FLD) four-bolted connections for providing the basic data of domestic design specification. Main variables are shear connection type (single shear and double shear) and end distance parallel to the direction of applied force. Fracture modes were classified into typical block shear fracture, tensile fracture and curling. Curling occurrence in single shear connection led to ultimate strength drop by up to 17%. Test strengths were compared with those by current design specifications and proposed equations by previous researches. For specimens with no curling, AISC/AISI/KBC, EC3 and Clement & Teh’s equations underestimated the strength. AIJ and Teh & Deierlein overestimated the strength of bolted connection. For specimens with curling, Kim & Lim’s equation was also overly unconservative to predict the ultimate strength of curled connections. 최근에 오스테나이트계 스테인리스강에 비해 높은 재료강도, 우수한 내식성(특히, 내응력부식균열)과 가격경쟁력을 지닌듀플렉스계 스테인리스강이 개발되었다. 그러나, 스테인리스강은 한국건축구조기준에 구조용 재료로 지정되어 있지 않아서 이에 대한 구조설계기준도 마련되어 있지 않은 실정이다. 이 연구에서는 국내 구조설계기준 작성에 필요한 기초자료를 제공하고자 듀플렉스계 스테인리스강 2행 2열 볼트접합부의 구조거동을 조사하기 위해 실험연구를 수행하였다. 주요변수는 전단접합 방법(일면전단과 이면전단)과 하중방향 연단거리로 한다. 실험종료시점에서 파단형태는 블록전단파단, 순단면파단과 면외변형으로 분류되었다. 일면전단 볼트접합부에서 면외변형 발생으로 최대 17%까지 내력저하가 발생되었다. 실험내력과 현행설계기준과 기존연구자에 의해 제안된 내력식에 의한 예측내력과 비교되었다. 면외변형의 영향이 없는 접합부에 대해서 AISC/AISI/KBC, EC3와 Clement & Teh 내력식은 접합부의 내력을 과소평가했지만 AIJ와 Teh & Deierlein 내력식은 과대평가했다. 면외변형에 의해 내력저하를 갖는 접합부에 대해서 Kim & Lim 내력식은 또한 과도하게 과대평가하는 경향을 보였다.

A duplex β″-Al₂O₃ solid electrolyte consisting of a thin dense layer and a porous substrate

Kim, Jin Y.,Canfield, Nathan L.,Bonnett, Jeff F.,Sprenkle, Vincent L.,Jung, Keeyoung,Hong, Inchul Elsevier 2015 Solid state ionics Vol.278 No.-

<P><B>Abstract</B></P> <P>To improve the performance of Na-beta batteries at intermediate temperatures (≤200°C) where much improved cyclability and reduced degradation can be achieved, there is a need to lower the resistance/polarization originated from β″-Al<SUB>2</SUB>O<SUB>3</SUB> solid electrolyte (BASE) while maintaining its good strength. In this paper, the concept of a duplex BASE consisting of a thin dense electrolyte and a porous support was proposed as a solution to achieve low area-specific resistance (ASR) with good mechanical strength supported by the porous substrate. The effects of various factors including porosity, composition, and homogeneity of ingredients on the flexural strength of duplex BASEs were examined. In summary, lower porosity, higher YSZ content in the structure, and attrition milling of raw powders resulted in improved strength. The ASR measurement exhibited that the resistance of duplex BASEs was mainly originated from a dense layer. Overall, the maximum strength of 260MPa and the ASR value of 0.31Ωcm<SUP>2</SUP> (at 350°C) was achieved from a duplex BASE consisting of a 50μm thick dense layer (Al<SUB>2</SUB>O<SUB>3</SUB>:YSZ=7:3 in volume) and a 500μm thick porous support (Al<SUB>2</SUB>O<SUB>3</SUB>:YSZ=4:6 in volume with 19% open porosity). The effects of various factors on the properties of duplex BASEs will be discussed in detail.</P> <P><B>Highlights</B></P> <P> <UL> <LI> As a method to lower the ASR, the concept of duplex BASEs is presented. </LI> <LI> A duplex BASEs consists of a thin dense β″-alumina layer and a mechanically strong porous support. </LI> <LI> Processing factors including conversion, porosity, composition, and homogeneity influence the strength of a duplex BASE. </LI> <LI> The minimum ASR value of 0.31Ωcm<SUP>2</SUP> was achieved at 350°C with decent strength of 260MPa. </LI> </UL> </P>

플라이애시를 혼입한 기포콘크리트의 압축강도 특성에 관한 실험적 연구

오세출(Oh Se-Chul),서치호(Seo Chee-Ho),지석원(Ji Suk-Won) 대한건축학회 2003 大韓建築學會論文集 : 構造系 Vol.19 No.4

This study aims at the production of foamed concrete mixed with fly-ash, examInIng the variation of the mechanical properties of foamed concrete, and issuing the data to site engineers for quality control. The experiment began by mixing the fly-ash by a maximum of 60% in stages and the mixing was mainly based on practical mixture. The following results were obtained from the experiment. In the instance of replacing cement with fly-ash. the outlook specific gravity and the water absorption ratio appeared not to be affected, while the compressive strength tended to decrease inversely proportional to the increasing fly-ash as compared to foamed concrete mixed with only cement. However, under long cure periods, an improvement in compressive strength was observed strength. As earlier stated, the pozzolanic reaction of the fly-ash contributed to the increased strength and also assisted in recovering the narrow range of the strength increased ratio obtained at early cure periods.

반응표면분석을 이용한 플라이애시 혼입 기포콘크리트의 비강도 특성에 관한 연구

이상안(Lee Sang-An),김화중(Kim Wha-Jung),김재경(Kim Jae-Kyung) 대한건축학회 2010 大韓建築學會論文集 : 構造系 Vol.26 No.7

There have been several investigations in the past on the influence of mixture composition on the properties of aerated concrete. This paper discusses the relation of empirical models for compressive strength-apparent density and flexural strength-apparent density of aerated concrete through statistically designed experiments. The response surface plots helps in visually analysing the influence of factors on the responses. The relative influence of fly ash replacement, water-binder ratio and hydrogen peroxide-binder ratio on strength and density of aerated concrete is studied by comparing it with main effect plot. The mutual influence of fly ash replacement, water-binder ratio and hydrogen peroxide-binder ratio on strength and density of aerated concrete is studied by comparing it with interaction plot. Specific strength of aerated concrete is higher in 0% and 35% of fly ash replacement.

고강도 오스테나이트계 스테인리스강(STS201) 일면전단 볼트접합부의 최대내력평가

강현식(Kang, Hyun-Sik),김태수(Kim, Tae-Soo) 대한건축학회 2017 大韓建築學會論文集 : 構造系 Vol.33 No.4

Recently, the usage of stainless steel in buildings and infra-structures has been gradually increased with the global need for sustainability thanks to its excellent durability. In the previous studies of bolted connections with 304 type and 430 type stainless steels, curling (out-of-plane deformation) in the direction of plate thickness (in the perpendicular direction of loading) was observed and resulted in strength reduction of single shear bolted connections. On the basis of previous findings, the purpose of this paper is to investigate ultimate strength, fracture mode and curling effect of single-shear bolted connection of cold-formed austenitic stainless steel (STS201) with high strength. Bolt arrangement and end distance parallel to the loading direction are considered as main variables. All specimens failed by net-tensile fracture at test end and curling was also observed in some specimens with long end distances. Test strengths were compared with design predictions by current specifications (AISC, KBC, AISI, AIJ and ASCE) and modified strength equation was suggested considering strength drop by curling and actual ultimate state.