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RISS 인기검색어
- 검색키워드
- 저자 : Xuhong Qiang (검색결과 4 건)
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Experimental and Theoretical Study on High Strength Steel Extended Endplate Connections After Fire
Xuhong Qiang,Nianduo Wu,Yongfeng Luo,Xu Jiang,Frans Bijlaard 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.2
In order to reveal more information and better understanding on the behavior and failure mechanisms of high strength steel (HSS) extended endplate connections at ambient temperature and after fi re, an experimental and theoretical study has been conducted and presented in this paper. The provisions of Eurocode 3 are verifi ed with the test results. Because strength of bolts decreases more rapidly than that of structural steels, failure modes of endplate connections may change after fi re. Hence, a series of equations are proposed to predict failure modes of endplate connections after fi re. Furthermore, FE simulations which can predicate the performance of HSS extended endplate connections with reasonable accuracy are adopted to study the behaviors of the connections after cooling down from various fi re temperatures and to validate the accuracy of the proposed equations. Moreover, a parametric study is carried out to explore an optimization design method. It is found that the current provisions of EC3 can justifi ably predict failure modes and plastic fl exural resistances of HSS extended endplate connections both at ambient temperature and cooling down from 550 °C, but it is not the case for their initial rotational stiff - ness and rotation capacity. In order to avoid brittle failure mode of endplate connections after fi re, appropriately increasing the diameter or grade of bolts in the design is suggested. What is more, the match of steel grade and thickness of column fl ange and endplate as well as beam should be considered in the optimization design of beam-column endplate connections.
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Xuhong Qiang,Nianduo Wu,Xu Jiang,Yongfeng Luo,Frans Bijlaard 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.4
Full-scale experimental study and numerical analysis on behaviors and failure mechanisms of full high strength steel extended endplate connections in fi re have been carried out and presented in this paper. The experimental behaviors of the connections were compared with the provisions of Eurocode 3. The test results show that the failure modes of the connections in fi re are bolt failure with yielding of the fl ange, as same as those at ambient temperature. The failures of the bolts in fi re are ductile while they are brittle at ambient temperature. The rotation capacity of the connections in fi re is proved suffi cient. What is more, at elevated temperature 550 °C, the plastic moment resistances of Q690 and Q960 full high strength steel endplate connections are only 40% of those at ambient temperature, while their initial rotation stiff ness are 66 and 63% respectively. But the rotation capacities of Q690 and Q960 high strength steel endplate connections are 1.38 and 1.74 times of those at ambient temperature. Moreover, it is found that the component method Eurocode 3 proposed based on connections made of mild steels can be used to calculate plastic resistances and to predict failure modes of high strength steel endplate connections in fi re, but it is not suitable to predict their stiff ness. The suggestions about rotation capacity of connections in Eurocode 3 are found too conservative for high strength steel endplate connections in fi re.
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Xu Jiang,Kai Sun,Xuhong Qiang,Dan Li,Qiwei Zhang 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.2
Orthotropic steel decks(OSD’s) are prone to fatigue cracking under cyclic loads, especially for rib-to-deck welded connection and rib-to-crossbeam welded connection. To reveal fracturing behaviors of these fatigue-prone sites, a multi-scale model of OSD’s specimen is established, including segmental shell-element part and local solid-element configuration. Based on the extended finite element method(XFEM), propagation analysis was carried out in this research. The analysis of stress intensity factor (SIF) shows that the crack at the weld root or weld toe of the rib-to-deck welded connection is a mixed-crack with modes I, II and III, where mode I plays a leading role. Besides, the maximum SIF KI of the crack at the weld toe is slightly larger than that at the weld root. For rib-to-crossbeam welded connection, the maximum SIF KI at the weld toe of the U-rib is greater than that at the weld toe of the crossbeam. The analysis of crack propagation shows that the crack growth rate at the weld toe is faster than that at the weld root with the same initial crack size and loading conditions. Similarly, for rib-to-crossbeam welded connection, the crack propagation at the weld toe of U-rib performs faster than that at the weld toe of crossbeam.
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Outd7b facilitates T cell activation and inflammatory responses by regulating Zap70 ubiquitination
( Hongbo Hu ),( Hui Wang ),( Yichuan Xiao ),( Jin Jin ),( Jae Hoon Chang ),( Qiang Zou ),( Xiaopin Xie ),( Xuhong Cheng ),( Shao Cong Sun ) 영남대학교 약품개발연구소 2016 영남대학교 약품개발연구소 연구업적집 Vol.26 No.-
Signal transduction from the T ceII receptor (TCR) is crucial for T cell-mediated immune responses and, when deregulated, also contributes to the development of autoimmunity. How TCR signaling is regulated is incompletely understood. In this study, we demonstrate a ubiquitin-dependent mechanism in which the deubiquitinase Otud7b has a crucial role in facilitatinq TCR signaling. Upon TCR ligation, Olud7b is rapidly recruited to the tyrosine kinase Zap70, a central mediator of TCR-proximal signaling. Otud7b deficiency attenuates the activation of Zap70 and its downstream pathways and impairs T cell activation and differentiation, rendering mice refractory to T cell-mediated autoimmune and inflammatory responses. Olud7b facilitated Zap70 activation by deubiquitinating Zap70, thus preventing the association of Zap70 with the negative-regulatory phosphatases SIs1 and Sts2. These findings establish Otud7b as a positive requlator of TCR-proximal signaling and T cell activation. highlighting the importance of deubiquitination in regulaling Zap70 function.
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