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RISS 인기검색어
- 검색키워드
- 저자 : Yongtao Bai (검색결과 5 건)
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Yongtao Bai,Xuchuan Lin,Ben Mou 한국강구조학회 2016 International Journal of Steel Structures Vol.16 No.2
In concrete-filled steel tubular (CFST) beam-columns under cyclic loadings, local buckling of restrained steel tube, crushing and slipping of the confined concrete could have significant influences on strength and stiffness degradation. This paper presents a numerical model based on fiber element discretization for simulating the deterioration behaviour of both rectangular and circular CFST beam columns under axial load and cyclic loading. Uniaxial stress-strain relationships for steel and concrete in CFST beam columns are proposed by introducing unified parameters to control the extent of deterioration. Axial contraction caused by local buckling was accounted by defining an inelastic region that promises plasticity and strength degradation. The numerical model was validated by comparing the simulation results and the associated experimental results. The influences of diameter-to-thickness ratio, concrete and steel strength ranging from normal strength to high strength on the deterioration behavior of circular and rectangular CFST beam-columns were analyzed. Finally, through recognizing the limit state to trigger global strength degradation of a CFST frame, the developed numerical model is applicable for simulating global behavior of CFST frames under collapse-level deformations.
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Yongtao Lin,Mingyue Zhao,Lin Bai,Hailun Li,Yong Xu,Xiang Li,Juan Xie,Yiyuan Zhang,Donghui Zheng 한국공업화학회 2021 Journal of Industrial and Engineering Chemistry Vol.97 No.-
Renal ischemia-reperfusion injury (RI/R) is one of the main causes of acute renal injury and a commonclinical disease with high morbidity and mortality. It is of great significance to deliver microRNAs(miRNAs) to cells and in vivo to realize gene regulation and treatment of related diseases. In this study, wereported that the nanocomplex FMN-17 could realize both therapeutic and functional monitoringsimultaneously in vivo and in vitro. The nanocomplex comprised a cationic cell-penetrating peptidenona-arginine, a targeting ligand folic acid, a caspase-3 responsive moiety, and a Cy imaging moiety. Thenanocomplex FMN-17 has been shown to deliver miR-17-5p efficiently and selectively into HK-2 cells andtissues. Treatment of HK-2 cells with the nanocomplex significantly increased the miR-17-5p level andinhibited apoptosis, as evident by reducing the expression of active caspase-3 and reactive oxygenspecies. Uptake of FMN-17 in vivo alleviated renal tissue injury by histological assessment. In summary,we designed and synthesized a new miRNA delivery system with high transfection efficiency, goodtherapeutic effect, and near-infrared imaging in renal ischemia/reperfusion injury.
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Wang Hui,Guo Yonghua,Bai Yongtao,Zhang Bin,Sun Qing,Xue Jianyang 한국강구조학회 2017 International Journal of Steel Structures Vol.17 No.3
This paper presents experimental investigation on the local and overall buckling capacity of Q690 high-strength circular steel tubes under axial compression. Coupon tests are undertaken to obtain the Young’s modulus, Poisson’s ratio, tensile yield stress and ultimate tensile strength of Q690 steel material. Forty-two specimens under axial compression are tested to evaluate the buckling behavior and the failure mode. Test results indicate that most of the existing design standards are conservative for the design of Q690 steel tubes. The distribution model of residual stress is measured by cutting ring method. Then, a finite element model based on modified column deflection curve method (CDC) is built to assess the effects of initial imperfection and residual stress on the stability capacity of the steel tubes. Finally, design methods and recommendations are provided for estimating the stability capacity of high-strength circular steel tubes.
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Long term structural health monitoring for old deteriorated bridges: a copula-ARMA approach
Yi Zhang,Chul-Woo Kim,Lian Zhang,Yongtao Bai,Hao Yang,Xiangyang Xu,Zhenhao Zhang 국제구조공학회 2020 Smart Structures and Systems, An International Jou Vol.25 No.3
Long term structural health monitoring has gained wide attention among civil engineers in recent years due to the scale and severity of infrastructure deterioration. Establishing effective damage indicators and proposing enhanced monitoring methods are of great interests to the engineering practices. In the case of bridge health monitoring, long term structural vibration measurement has been acknowledged to be quite useful and utilized in the planning of maintenance works. Previous researches are majorly concentrated on linear time series models for the measurement, whereas nonlinear dependences among the measurement are not carefully considered. In this paper, a new bridge health monitoring method is proposed based on the use of long term vibration measurement. A combination of the fundamental ARMA model and copula theory is investigated for the first time in detecting bridge structural damages. The concept is applied to a real engineering practice in Japan. The efficiency and accuracy of the copula based damage indicator is analyzed and compared in different window sizes. The performance of the copula based indicator is discussed based on the damage detection rate between the intact structural condition and the damaged structural condition.
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A new formulation of cracking in concrete structures based on lumped damage mechanics
Daniel V.C. Teles,Rafael N. Cunha,Ricardo A. Picón,David L.N.F. Amorim,Yongtao Bai,Sergio P.B. Proença,Julio Flórez-López 국제구조공학회 2023 Structural Engineering and Mechanics, An Int'l Jou Vol.88 No.5
Lumped Damage Mechanics (LDM) is a theory proposed in the late eighties, which assumes that structural collapse may be analyzed as a two-phase phenomenon. In the first (pre-localization) stage, energy dissipation is a continuous process and it may be modelled by means of the classic versions of the theory of plasticity or Continuum Damage Mechanics (CDM). The second, post-localization, phase can be modelled assuming that energy dissipation is lumped in zones of zero volume: inelastic hinges, hinge lines or localization surfaces. This paper proposes a new LDM formulation for cracking in concrete structures in tension. It also describes its numerical implementation in conventional finite element programs. The results of three numerical simulations of experimental tests reported in the literature are presented. They correspond to plain and fiber-reinforced concrete specimens. A fourth simulation describes also the experimental results of a new test using the digital image correlation technique. These numerical simulations are also compared with the ones obtained using conventional Cohesive Fracture Mechanics (CFM). It is then shown that LDM conserves the advantages of both, CDM and CFM, while overcoming their drawbacks.
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