Experimental Investigation on Fatigue Behavior of Steel Reinforced Concrete Composite Beam-to-Girder Joints

Le-Wei Tong,Qingjun Xian,Liying Zhou,Yiyi Chen,Yunfeng Zhang 한국강구조학회 2012 International Journal of Steel Structures Vol.12 No.4

Fatigue behavior and failure mechanism of steel reinforced concrete (SRC) beam-to-girder joints is discussed in this paper,which is intended for use in high-speed railway station structures due to their high stiffness and load capacity. Three identical SRC beam-to-girder joint specimens were designed and tested under static loading and two stages of fatigue loading. In the first stage of fatigue loading, the specimens were subjected to design fatigue load for 2 million cycles, while during the second stage, the specimens were loaded to failure under increased fatigue loading amplitude in order to know its fatigue strength and failure mechanism. The constructional details of SRC beam-to-girder joint specimen and the method of loading and testing are presented. The comparison in structural behavior of the joint is made between under static and fatigue loading. Fatigue failure characteristics of the joint are described in detail. It is found that the SRC beam-to-girder joints remained in their elastic range and the concrete surface crack did not exceed 0.1 mm when subjected to design static loading and 2 million cycles of design fatigue loading. There was no significant difference in structural behavior of each component of SRC composite beam between static and fatigue loading. Fatigue failure occurred after these joints were applied higher-level fatigue loading for another 0.70to 0.91 million cycles. Fatigue crack was initiated at the tension flange of I-shape steel of beam connected by welding to the flange of I-shape steel of girder or at the hole in tension flange of I-shape steel of beam, and then the crack propagated along flange width and web height of the I-shape steel in beam until the I-shape steel lost loading capacity due to lack of enough cross section. The fatigue behavior of constructional detail of the I-shape steel played a key role in the fatigue strength of the SRC beam-to-girder joints. Discussions on improving the fatigue strength of SRC beam-to-girder joints and future research aspects are presented finally.

Effects of Information Transmission between the London and Shanghai Non-ferrous Metal Markets

Tong Le Ga,박철호(Cheol-Ho Park) 중앙대학교 한국전자무역연구소 2022 전자무역연구 Vol.20 No.1

연구목적: 본 연구의 목적은 런던과 상하이의 비철금속시장 간 정보전이효과(information spillover effects)를 분석하는데 있다. 양 비철금속시장 간 정보전이효과를 살펴보는 것은 직접적으로 시장의 효율성 및 선도-지연관계를 밝히는 것은 물론이고, 이를 통해 금융시장의 차익거래나 포트폴리오 구성, 그리고 국내기업과 정부의 수출입 및 원자재 조달정책 등에 유용하게 활용될 수 있다. 논문구성/논리: 런던시장과 상하이시장의 선물 수익률의 안정성을 검정하기 위해 먼저 단위근 검정을 실시하고 양 시장의 수준변수들 간에 안정적인 선형결합이 존재하는지 여부를 파악하기 위해 Johansen(1991) 공적분 검정을 실시한다. 그리고 양 시장 간 비철금속 가격의 수익률 전이효과와 한 시장에서 발생한 수익률 충격 및 변동성이 다른 시장의 변동성에 미치는 영향, 그리고 수익률 충격의 비대칭적 전이효과 존재 여부를 함께 파악하기 위해 비대칭 이변량(bivariate) VAR(VECM)- BEKK-GARCH 모형을 사용한다. 공적분 관계가 나타나지 않은 경우 VAR(Vector Autoregressive) 모형을 조건부 평균방정식으로 사용하고, 공적분 관계가 나타난 경우 VECM(Vector Error Correction Model)을 사용한다. 결과: 전체 표본 기간 동안 상하이시장과 런던시장은 각 선물(특히, 알루미늄선물과 구리선물)에 대해 서로 양(+)의 수익률 전이효과를 주고받는 것으로 나타났다. 아연선물의 경우 2009-2012년 기간에서는 런던시장에서 상하이시장으로의 일방적인 양(+)의 수익률 전이효과가 존재하였으나, 2013-2016년 기간에서는 쌍방향의 수익률 전이효과가 발견되어 시간이 흐름에 따라 정보의 흐름이 활발해졌음을 알 수 있다. 또한, 각 표본기간 동안 구리선물과 아연선물에 대해 양 시장 간에는 장기균형관계가 존재하였다. 각 하위 기간에서 상하이시장의 변동성은 런던시장의 아연선물에만 영향을 미친 반면, 런던시장의 변동성은 상하이시장의 세 가지 선물 모두에 영향을 미쳤다. 독창성/가치: 비철금속 다소비 국가이자 대부분의 원재료를 수입에 의존하고 있는 우리나라의 경우, 비철금속 국제가격의 상승은 국내 물가를 상승시키고 기업의 채산성을 악화시킬 수 있다. 따라서, 비철금속 국제가격의 움직임을 이해하고 적절히 관리하는 것은 기업과 정책당국에 매우 중요한 과제임에도 불구하고, 국제 비철금속시장 간 정보의 흐름을 분석한 국내 연구는 매우 미흡한 실정이다. 이에 본 연구는 2008년 글로벌 금융위기 이후 비철금속 가격의 등락 주기가 나타났던 기간 동안 세계 최대 비철금속시장인 런던금속거래소(LME)와 비철금속의 최대 생산국이자 소비국인 중국의 상하이선물거래소(SHFE) 간 주요 비철금속 선물의 수익률 및 변동성 전이효과를 분석하고 그 시사점을 도출했다는 데 의의가 있다. Purpose: This study aims to analyze the effects of information transmission of non-ferrous metal prices between the London and Shanghai markets. Examining the information spillover effects between the two markets not only directly reveals market efficiency and lead-lag relationships, but can also be useful for arbitrage trading or portfolio composition, and the export-import and raw material procurement policies of domestic companies and the government. Composition/Logic: To test the stability of futures returns in the London and Shanghai markets, a unit root test is first performed, and Johansen’s cointegration test is performed to determine whether there is a stable linear combination between the prices of the two markets. The asymmetric bivariate VAR(VECM)-BEKK-GARCH model is used to determine the existence of the non-ferrous metals’ return and volatility transmission effects between both markets, and asymmetric transmission effects of return shock of one market on the volatility of the other market. Findings: During the full sample period, the Shanghai and London markets were found to have positive bi-directional return transmission effects for each futures contract (especially aluminum and copper futures). For zinc futures, there was a uni-directional positive return transmission effect from the London market to the Shanghai market in the 2009-2012 period, but the bi-directional effects were found in the 2013-2016 period, indicating that information flow became active over time. In each sub-period, volatility in the Shanghai market affected only zinc futures in the London market, while volatility in the London market affected all three futures in the Shanghai market. Originality/Value: In the Korea case, an increase in international non-ferrous metal prices can raise domestic prices and decrease corporate profitability. Therefore, understanding and properly managing the movement of non-ferrous metal prices is a very important task for companies and policy makers. Nevertheless, there are not many studies on the international non-ferrous metal market. This study is valuable in that it analyzed the return and volatility transmission effects of major non-ferrous futures contracts between the London and Shanghai markets after the financial crisis of 2008.

Fatigue Behavior of Welded Thin-Walled T-joints between Circular and Square Hollow Secitons

Le-Wei Tong,X.L. Zhao,F.R.Mashiri,P.Grundy,Hong-Zhi Zheng 한국강구조학회 2006 International Journal of Steel Structures Vol.6 No.3

The fatigue behaviour of thin-walled CHS-to-SHS T-joints (t < 4 m) under in-plane bending are studied in this paper. Thefailure modes observed in the fatigue tests are described. Surface crack growth was recorded at progressive stages of fatiguelife, from initiation, through-thickness life and end of test failure. The characteristics of fatigue crack initiation and propagationare described. The stress concentration factors (SCFs) along the weld toes at both the circular brace and the square chord are-dimensional joint parameters on SCFs are discussed. The resultant SCFs are compared to both the SCFs from CHS and RHSparametric formulae in IIW guidelines. Both the fatigue tests and FE analyses showed that the hot spot locations of the CHS-to-SHS T-joints were located at the weld toe of the square hollow section chord.

Landscape Function and Tourism Industry: A Case Study of Moc Chau Plateau, Vietnam

LE, Hoa Thi Thu,TONG, Binh Thanh,VU, Ngoc Thi Minh,HO, Luu Si,PHAM, Thang Viet,TRINH, Hang Thi Thu Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.12

Tourism is not only a cultural service but also a resource consuming industry. Landscape function framework is a powerful tool to show the relationship between nature and people. This study collects 50 documents around the world to analyze the relationship between the 4 functional groups of the landscape (regulatory functions, production and supply functions, resident functions, information and entertainment functions) and the tourism industry. On that basis, we created an establishment for practical contact analysis of the goods and services of the landscape for tourism development in Moc Chau plateau, Vietnam. Research results show that tourism is an economic sector that benefits from the landscape and has a clear resource orientation. Moc Chau plateau has rich tourism resources and has the conditions to develop various types of tourism, especially cultural tourism based on community and resort tourism. The two cultural functions and the providing functions are the two most important functional groups for the tourism development of Moc Chau district, bringing the two most important tourism icons for Moc Chau, a green steppe, cool milk benevolent and also a district rich in national culture. From these conclusions, the authors give recommendations and notable points about landscapes in the tourism industry, especially in places with topography like Moc Chau.

Impacts of Urban Land Cover Change on Land Surface Temperature Distribution in Ho Chi Minh City, Vietnam

Le, Thi Thu Ha,Nguyen, Van Trung,Pham, Thi Lan,Tong, Thi Huyen Ai,La, Phu Hien 한국측량학회 2021 한국측량학회지 Vol.39 No.2

Applying the Fuzzy Decision-Making Method for Program Evaluation and Management Policy of Vietnamese Higher Education

TONG, Kiet Hao,NGUYEN, Quyen Le Hoang Thuy To,NGUYEN, Tuyen Thi Mong,NGUYEN, Phong Thanh,VU, Ngoc Bich Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.9

Education policy is a dynamic process featuring social development trends. The world countries have focused their education program on empowering the learners for future life and work. This paper aims to assess the higher education curriculum based on a survey of 280 students, employers, alumni, and lecturers in both social sciences and natural sciences in Ho Chi Minh City, Vietnam. The fuzzy decision-making method, namely the Fuzzy Extent Analysis Method (F-EAM), was applied to measure the relative weight of each parameter. Seven factors under the curriculum development have been put in the ranking. Input with emphasis on foreign language was the highest priority in curriculum development, given the expected demand of the labor market. Objective and learning outcome and teaching activities ranked second and third, respectively. The traditional triangle of teaching content, methodology, and evaluation and assessment are still proven their roles, but certain modifications have been defined in the advanced curriculum. Teaching facilities had the least weight among the seven dimensions of curriculum development. The findings are helpful for education managers to efficiently allocate scarce resources to reform the curriculum to bridge the undergraduate quality gap between labor supply and demand, meeting the dynamic trends of social development.

Probabilistic real-time updating for geotechnical properties evaluation

Iok-Tong Ng,Ka-Veng Yuen,Le Dong 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.2

Estimation of geotechnical properties is an essential but challenging task since they are majorcomponents governing the safety and reliability of the entire structural system. However, due to time andbudget constraints, reliable geotechnical properties estimation using traditional site characterizationapproach is difficult. In view of this, an alternative efficient and cost effective approach to address theoverall uncertainty is necessary to facilitate an economical, safe and reliable geotechnical design. In thispaper a probabilistic approach is proposed for real-time updating by incorporating new geotechnicalinformation from the underlying project site. The updated model obtained from the proposed method isadvantageous because it incorporates information from both existing database and the site of concern. Anapplication using real data from a site in Hong Kong will be presented to demonstrate the proposed method.

A hemoglobin-based oxygen-carrying biomimetic nanosystem for enhanced chemo-phototherapy and hypoxia alleviation of hepatocellular carcinoma

Jing-Qing Le,Fang Yang,Xun-Huan Song,Ke-Ke Feng,Ling-Wu Tong,Meng-Die Yin,Wen-Zhong Zhang,Ying-Qi Lin,Hui Wu,Jing-Wei Shao 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.123 No.-

Tumor microenvironment is characterized by low pH, high reactive oxygen species and hypoxia, whichprovides a suitable environment for cancer growth. The hypoxia not only elevates tumor angiogenesisand metastasis, but also is responsible for the development of treatment resistance, which graduallybecomes a significant impediment for cancer therapy. Therefore, we developed a biomimetic nanosystemcontaining hemoglobin extracted from red blood cells, chemotherapy drug sorafenib, sensitizer ursolicacid and photosensitizer indocyanine green for enhanced chemo-photo combination therapy of hepatocellularcarcinoma, which could not only enhance the chemotherapy effect of sorafenib bowing to thesensitizing effect of ursolic acid, but also achieved synergetic phototherapy in virtue of indocyaninegreen. Besides, the nanoparticles could effectively delivery exogenous oxygen to tumor site and amelioratethe tumor hypoxic environment with the assistance of hemoglobin. The dual-sensitization drugdelivery system was expected to effectively reduce the resistance of traditional treatment methodsagainst tumor hypoxia, providing a novel prospect for the synergistic hepatocellular carcinomatreatment.

Experimental Investigation on Fatigue Strength of Joints between SRC Beams and Concrete-Filled RHS Columns

Qingjun Xian,Le-Wei Tong,Liying Zhou,Yiyi Chen 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.5

Fatigue behavior, failure mechanism and fatigue strength of joints between steel reinforced concrete (SRC) beams and Concrete Filled Rectangular Hollow Section (CFRHS) columns is discussed in this paper. Three identical beam-to-column joint specimens were designed and tested under static loading and two stages of fatigue loading. In the first stage of fatigue loading, the specimens were subjected to design fatigue load for 2 million cycles, while during the second stage, they were loaded to failure under increased fatigue load in order to know failure mechanism and fatigue strength. It is found that the joints satisfied design requirements when subjected to static loading and design fatigue loading. Fatigue failure occurred after these joints were applied higher-level fatigue loading. The crack initiated at the weld toe of stud or stirrup hole in the upper flange of I-shaped steel in certain SRC beam, and then it propagated along flange width in winding trajectory until fatigue fracture occurred. Stress amplitude of tension flange in SRC beam can be regarded as the parameter representing fatigue strength of the joints. S-N curves in related codes are selected to evaluate fatigue strength of the joints. The design method is suggested to consider fatigue design of the joints.

AIR CURTAIN CHARACTERISTICS INVESTIGATION OF THE HIGH TEMPERATURE VEHICLE PAINTING DRYING WORKSHOP

Chen Yue,Le Tong,Murong Ge,Furui Wang,Weifeng He,Pengju Gao,Youde Peng 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.2

Installing the air curtain for painting drying workshop is an effective method for continuous vehicle in and out. A top injection air curtain is designed for the high temperature vehicle painting drying workshop in this research. Based on the numerical simulation method, the effect of key operating parameters and working state of the air curtain on the stability and thermal dissipation performance of air curtain have been investigated. The results showed that increasing both the air curtain injection velocity and injection angle improved the stability of the top injection air curtain. Both the optimized air curtain injection velocity and the air curtain injection angle are obtained to achieve the lowest thermal dissipation effect at the fixed workshop height. The stability of the air curtain declines sharply and the thermal energy dissipation of the workshop increased obviously at high workshop height. With the vehicle skeleton passes through the air curtain, the stable gas barrier is destroyed, and the thermal dissipation is increased compared without vehicle passing. The low air curtain jet velocity is recommended with vehicle through the air curtain. Moreover, the small distance between the car bottom to the ground, and the quickly vehicles passing air curtain are suggested in actual operation.