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超长结构温度预应力筋控制裂缝施工技术 被引量:1
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作者 石彦明 《山西建筑》 2011年第30期100-101,共2页
针对工程超长结构裂缝问题,采取设置后浇带方法及布设温度预应力筋技术,结合后浇带与预应力技术的优势,在后浇带封闭以前,张拉预应力筋,使得预应力效应得以充分建立;后浇带封闭以后,结构形成受力整体,从而对确保工程质量起到了重要作用。
关键词 后浇带 温度预应力 张拉
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温度对连续拱桥体外预应力张拉应力、伸长量影响分析
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作者 张骞 《甘肃科技》 2017年第10期76-78,共3页
天水市双桥大桥连续拱桥体外束张拉采用分步张拉的施工方法,张拉周期近一年,期间温度变化对体外束内应力及张拉伸长量存在较大影响。本文对体外束分阶段张拉过程中伸长量偏差进行原因分析,指出了分阶段张拉周期内温度变化是造成应力束... 天水市双桥大桥连续拱桥体外束张拉采用分步张拉的施工方法,张拉周期近一年,期间温度变化对体外束内应力及张拉伸长量存在较大影响。本文对体外束分阶段张拉过程中伸长量偏差进行原因分析,指出了分阶段张拉周期内温度变化是造成应力束伸长量较理论值出现较大偏差的主要原因,探究了阶段性预应力损失与温差、伸长量偏差之间的关系。并在该桥梁施工过程中得验证。为今后施工类似桥梁体外束张拉计算提供借鉴。 展开更多
关键词 体外预应力 体外束 预应力 温度预应力 伸长量
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美兰机场二期航站楼超长无变形缝混凝土结构裂缝控制施工技术 被引量:5
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作者 郭思壮 梁华站 +3 位作者 徐振杰 王磊 田忠贵 王凤然 《工程建设与设计》 2020年第4期199-201,共3页
美兰机场二期航站楼采用超长无变形缝混凝土结构,施工过程中通过采取多种措施减少了超长混凝土无变形缝结构因混凝土收缩产生的裂缝。论文介绍了施工过程中,对补偿收缩混凝土、纤维混凝土的配合比、强度、浇筑以及养护的要求,并对跳仓... 美兰机场二期航站楼采用超长无变形缝混凝土结构,施工过程中通过采取多种措施减少了超长混凝土无变形缝结构因混凝土收缩产生的裂缝。论文介绍了施工过程中,对补偿收缩混凝土、纤维混凝土的配合比、强度、浇筑以及养护的要求,并对跳仓法、加强后浇带以及预应力温度筋的设计以及施工要点进行总结。 展开更多
关键词 海口美兰机场二期 超长无变形缝混凝土结构 裂缝 温度预应力 跳仓法
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葫芦岛体育中心体育场超长混凝土结构施工技术
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作者 王兰群 张廷安 +2 位作者 徐云双 罗德龙 薛飞 《工程质量》 2013年第S1期317-320,共4页
葫芦岛体育场工程楼板和看台采用钢筋混凝土全现浇结构,4道伸缩缝将钢筋混凝土结构分为4块,最长的东西看台两部分达240m长,采用留置后浇带和设置无粘接预应力温度筋等办法解决超长结构因温度变化而致混凝土结构开裂的影响,保证结构的使... 葫芦岛体育场工程楼板和看台采用钢筋混凝土全现浇结构,4道伸缩缝将钢筋混凝土结构分为4块,最长的东西看台两部分达240m长,采用留置后浇带和设置无粘接预应力温度筋等办法解决超长结构因温度变化而致混凝土结构开裂的影响,保证结构的使用寿命。 展开更多
关键词 超长现浇结构 补偿收缩混凝土 预应力温度
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Temperature Stress Analysis of Prestressed Concrete Box Girder with Corrugated Steel Webs 被引量:5
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作者 单成林 刘文芳 《Transactions of Tianjin University》 EI CAS 2012年第2期97-103,共7页
To figure out the distribution of temperature gradient along the girder height of steel-concrete composite box girder, combined with the mechanical characteristics of prestressed concrete composed box girder with corr... To figure out the distribution of temperature gradient along the girder height of steel-concrete composite box girder, combined with the mechanical characteristics of prestressed concrete composed box girder with corrugated steel webs, the calculation formulas of cross-sectional temperature stress along the span in a simply-supported beam bridge with composite section were derived under the conditions of static equilibrium and deformation compatibility of the beam element. The methods of calculating the maximum temperature stress value were discussed when the connectors are assumed rigid or flexible. Theoretical and numerical results indicate that the method proposed shows better precision for the calculation of temperature self-stress in both the top and the bottom surfaces of the box girder. Moreover, the regularity of temperature stress distribution at different locations along the girder span is that the largest axial force of the top or the bottom plate of the box girder is located in the midspan and spreads decreasingly until zero at both supported ends, and that the greatest longitudinal shear density in steel-concrete interface appears at both supported ends and then reduces gradually to zero in the midspan. 展开更多
关键词 bridge engineering composite structure temperature effect corrugated steel web connector influence
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Response to temperature stress of reactive oxygen species scavenging enzymes in the cross-tolerance of barley seed germination 被引量:8
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作者 Yu-qin MEI Song-quan SONG 《Journal of Zhejiang University-Science B(Biomedicine & Biotechnology)》 SCIE CAS CSCD 2010年第12期965-972,共8页
A number of studies have shown the existence of cross-tolerance in plants, but the physiological mechanism is poorly understood. In this study, we used the germination of barley seeds as a system to investigate the cr... A number of studies have shown the existence of cross-tolerance in plants, but the physiological mechanism is poorly understood. In this study, we used the germination of barley seeds as a system to investigate the cross-tolerance of low-temperature pretreatment to high-temperature stress and the possible involvement of reactive oxygen species (ROS) scavenging enzymes in the cross-tolerance. After pretreatment at 0 ℃ for different periods of time, barley seeds were germinated at 35 ℃, and the content of malondialdehyde (MDA) and the activities of ROS scavenging enzymes were measured by a spectrophotometer analysis. The results showed that barley seed germinated very poorly at 35 ℃, and this inhibitive effect could be overcome by pretreatment at 0 ℃. The MDA content varied, depending on the temperature at which seeds germinated, while barley seeds pretreated at 0 ℃ did not change the MDA content. Compared with seeds germinated directly at 35 ℃, the seeds pretreated first at 0 ℃ and then germinated at 35 ℃ had markedly increased activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), and glutathione reductase (GR). The SOD and APX activities of seeds germinated at 35 ℃ after 0 ℃-pretreatment were even substantially higher than those at 25 ℃, and GR activity was similar to that at 25 ℃, at which the highest germination performance of barley seeds was achieved. These results indicate that low-temperature pretreatment can markedly increase the tolerance of barley seed to high temperature during germination, this being related to the increase in ROS scavenging enzyme activity. This may provide a new method for increasing seed germination under stress environments, and may be an excellent model system for the study of cross-tolerance. 展开更多
关键词 Barley seed CROSS-TOLERANCE Germination/growth Reactive oxygen species (ROS) scavenging enzyme Pretreatment at low temperature Temperature stress
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