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Dynamic characteristics of multi-span spinning beams with elastic constraints under an axial compressive force
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作者 Xiaodong GUO Zhu SU Lifeng WANG 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2024年第2期295-310,共16页
A theoretical model for the multi-span spinning beams with elastic constraints under an axial compressive force is proposed.The displacement and bending angle functions are represented through an improved Fourier seri... A theoretical model for the multi-span spinning beams with elastic constraints under an axial compressive force is proposed.The displacement and bending angle functions are represented through an improved Fourier series,which ensures the continuity of the derivative at the boundary and enhances the convergence.The exact characteristic equations of the multi-span spinning beams with elastic constraints under an axial compressive force are derived by the Lagrange equation.The efficiency and accuracy of the present method are validated in comparison with the finite element method(FEM)and other methods.The effects of the boundary spring stiffness,the number of spans,the spinning velocity,and the axial compressive force on the dynamic characteristics of the multi-span spinning beams are studied.The results show that the present method can freely simulate any boundary constraints without modifying the solution process.The elastic range of linear springs is larger than that of torsion springs,and it is not affected by the number of spans.With an increase in the axial compressive force,the attenuation rate of the natural frequency of a spinning beam with a large number of spans becomes larger,while the attenuation rate with an elastic boundary is lower than that under a classic simply supported boundary. 展开更多
关键词 multi-span spinning beam elastic constraint improved Fourier series free vibration semi-analytical solution
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A procedure of the method of reverberation ray matrix for the buckling analysis of a thin multi-span plate 被引量:2
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作者 Zhiwei LI Guohua NIE 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI CSCD 2020年第7期1055-1068,共14页
A procedure of the method of reverberation ray matrix(MRRM)is developed to perform the buckling analysis of thin multi-span rectangular plates having internal line supports or stiffeners.A computation algorithm for th... A procedure of the method of reverberation ray matrix(MRRM)is developed to perform the buckling analysis of thin multi-span rectangular plates having internal line supports or stiffeners.A computation algorithm for the reverberation ray matrix in the MRRM is derived to determine the buckling loading.Specifically,the analytical solutions are presented for the buckling of the structure having two opposite simply-supported or clamped-supported edges with spans,while the constraint condition of two remaining edges may be in any combination of free,simply-supported,and clamped boundary conditions.Furthermore,based on the analysis of matrices relating to the unknown coefficients in the solution form for the deflection in terms of buckling modal functions,some recursive equations(REs)for the MRRM are introduced to generate a reduced reverberation ray matrix with unchanged dimension when the number of spans increases,which promotes the computation efficiency.Several numerical examples are given,and the present results are compared with the known solutions to illustrate the validity and accurateness of the MRRM for the buckling analysis. 展开更多
关键词 multi-span thin rectangular plate BUCKLING method of reverberation ray matrix(MRRM) recursive equation(RE)
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Networked collaborative pseudo-dynamic testing of a multi-span bridge based on NetSLab 被引量:1
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作者 Cai Xinjiang Tian Shizhu +1 位作者 Wang Dapeng Xiao Yan 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2009年第3期387-397,共11页
Modem dynamic tests such as networked collaborative pseudo-dynamic testing (PDT) provide new tools to study the dynamic performance of large and complex structures. In this paper, several networked collaborative PDT... Modem dynamic tests such as networked collaborative pseudo-dynamic testing (PDT) provide new tools to study the dynamic performance of large and complex structures. In this paper, several networked collaborative PDT systems established in China and abroad are introduced, including a detailed description of the first networked collaborative platform that involved the construction of a standardized demonstration procedure for networked collaborative PDT. The example is a multi-span bridge with RC piers retrofitted by FRP, and a networked structural laboratory (NetSLab) platform is used to link distributed laboratories located at several universities together. Substructure technology is also used in the testing. The characteristics, resource sharing and collaborative work of NetSLab are described, and the results illustrate that use of the NetSLab is feasible for studying the dynamic performance of multi-span bridge structures. 展开更多
关键词 dynamic tests NETWORKED pseudo-dynamic testing multi-span bridges RC short piers FRP NetSLab
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Numerical Calculation of Dynamic Response for Multi-Span Non-Uniform Beam Subjected to Moving Mass with Friction 被引量:3
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作者 Junping Pu Peng Liu 《Engineering(科研)》 2010年第5期367-377,共11页
In order to simulate the coupling vibration of a vehicle or train moves on a multi-span continuous bridge with non-uniform cross sections, a moving mass model is used according to the Finite Element Method, the effect... In order to simulate the coupling vibration of a vehicle or train moves on a multi-span continuous bridge with non-uniform cross sections, a moving mass model is used according to the Finite Element Method, the effect of the inertial force, Coriolis force and centrifugal force are considered by means of the additive matrices. For a non-uniform rectangular section beam with both linear and parabolic variable heights in a plane, the stiffness and mass matrices of the beam elements are presented. For a non-uniform box girder, Romberg numerical integral scheme is adopted, each coefficient of the stiffness matrix is obtained by means of a normal numerical computation. By applying these elements to calculate the non-uniform beam, the computational accuracy and efficiency are improved. The finite element method program is worked out and an entire dynamic response process of the beam with non-uniform cross sections subjected to a moving mass is simulated numerically, the results are compared to those previously published for some simple examples. For some complex multi-span bridges subjected to some moving vehicles with changeable velocity and friction, the computational results, which can be regarded as a reference for engineering design and scientific research, are also given simultaneously. 展开更多
关键词 Dynamic Response multi-span BEAM NON-UNIFORM SECTION FRICTION BRAKING Force
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Multi-Span and Multiple Relevant Time Series Prediction Based on Neighborhood Rough Set 被引量:1
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作者 Xiaoli Li Shuailing Zhou +1 位作者 Zixu An Zhenlong Du 《Computers, Materials & Continua》 SCIE EI 2021年第6期3765-3780,共16页
Rough set theory has been widely researched for time series prediction problems such as rainfall runoff.Accurate forecasting of rainfall runoff is a long standing but still mostly signicant problem for water resource ... Rough set theory has been widely researched for time series prediction problems such as rainfall runoff.Accurate forecasting of rainfall runoff is a long standing but still mostly signicant problem for water resource planning and management,reservoir and river regulation.Most research is focused on constructing the better model for improving prediction accuracy.In this paper,a rainfall runoff forecast model based on the variable-precision fuzzy neighborhood rough set(VPFNRS)is constructed to predict Watershed runoff value.Fuzzy neighborhood rough set dene the fuzzy decision of a sample by using the concept of fuzzy neighborhood.The fuzzy neighborhood rough set model with variable-precision can reduce the redundant attributes,and the essential equivalent data can improve the predictive capabilities of model.Meanwhile VFPFNRS can handle the numerical data,while it also deals well with the noise data.In the discussed approach,VPFNRS is used to reduce superuous attributes of the original data,the compact data are employed for predicting the rainfall runoff.The proposed method is examined utilizing data in the Luo River Basin located in Guangdong,China.The prediction accuracy is compared with that of support vector machines and long shortterm memory(LSTM).The experiments show that the method put forward achieves a higher predictive performance. 展开更多
关键词 Rainfall and runoff variable precision fuzzy neighborhood rough set LSTM multi-span
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Vortex-Induced Vibration Response Features of A Submarine Multi-Span Pipeline via Towing Tank Experimental Tests
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作者 XU Wan-hai JIA Kun +1 位作者 MA Ye-xuan SONG Zhi-you 《China Ocean Engineering》 SCIE EI CSCD 2023年第2期175-189,共15页
In offshore engineering, the phenomenon of free span often occurs, and the pipeline may have multiple free spans adjacent to each other, forming a multi-span pipeline. The interaction of different spans makes the stru... In offshore engineering, the phenomenon of free span often occurs, and the pipeline may have multiple free spans adjacent to each other, forming a multi-span pipeline. The interaction of different spans makes the structural vibration characteristics more complex, which may change the fatigue characteristics of the pipeline and affect the safety of the structure. In this paper, model tests were designed to explore the vortex-induced vibration(VIV) characteristics of multi-span pipelines and investigate the multi-span interaction mechanism. The experimental study mainly focused on the dynamic response of double-span pipelines, and further extended to triple-span pipelines, hoping that the results can be applied to more complex environment. The effects of span-length ratio, buried depth and axial force on VIV of the pipeline were investigated and discussed. The dynamic response of the pipeline varied with the span length. There was obvious interaction between different spans of multi-span pipelines, and the pipe-sediment interaction obviously affected the vibration characteristics of pipeline. The differences of pipeline burial depth and axial force changed the structural stiffness. With the increase of buried depth, the response amplitude presented a downward trend. The spanwise evolutions were asymmetric caused by the pipe-sediment interaction and multi-span interaction. The results can help to identify multi-span pipelines in engineering, and realize the prevention and control of free spans. 展开更多
关键词 vortex-induced vibration submarine pipeline pipe-sediment interaction multi-span interaction
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Analytical investigation of bidirectional ductile diaphragms in multi-span bridges
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作者 Xiaone Wei Michel Bruneau 《Earthquake Engineering and Engineering Vibration》 SCIE EI CSCD 2018年第2期235-250,共16页
In the AASHTO Guide Specifications for Seismic Bridge Design Provisions,ductile diaphragms are identified as Permissible Earthquake-Resisting Elements(EREs),designed to help resist seismic loads applied in the trans... In the AASHTO Guide Specifications for Seismic Bridge Design Provisions,ductile diaphragms are identified as Permissible Earthquake-Resisting Elements(EREs),designed to help resist seismic loads applied in the transverse direction of bridges.When adding longitudinal ductile diaphragms,a bidirectional ductile diaphragm system is created that can address seismic excitations acting along both the bridge’s longitudinal and transverse axes.This paper investigates bidirectional ductile diaphragms with Buckling Restrained Braces(BRBs)in straight multi-span bridge with simply supported floating spans.The flexibility of the substructures in the transverse and longitudinal direction of the bridge is considered.Design procedures for the bidirectional ductile diaphragms are first proposed.An analytical model of the example bridge with bidirectional ductile diaphragms,designed based on the proposed methodology,is then built in SAP2000.Pushover and nonlinear time history analyses are performed on the bridge model,and corresponding results are presented.The effect of changing the longitudinal stiffness of the bidirectional ductile diaphragms in the end spans connecting to the abutment is also investigated,in order to better understand the impact on the bridge’s dynamic performance. 展开更多
关键词 bidirectional ductile diaphragm seismic resistance multi-span bridge with floating spans
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Research and Analysis on Cooling Capacity of Temperature Adjustment Equipments in Agricultural Multi-span Greenhouse
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作者 Dong WANG Xiaohu YANG 《Asian Agricultural Research》 2017年第11期44-47,53,共5页
The high summer indoor temperature in agricultural greenhouse is not conducive to crop growth,so it is necessary to cool the greenhouse. In this study,taking the agricultural multi-span greenhouse with strong temperat... The high summer indoor temperature in agricultural greenhouse is not conducive to crop growth,so it is necessary to cool the greenhouse. In this study,taking the agricultural multi-span greenhouse with strong temperature adjustment ability for example,we make an experimental analysis on the temperature changes inside and outside the greenhouse under nine different equipment combinations( fan,skylight,sunshade,sunshade + fan,cooling pad + fan,skylight + fan,sunshade + skylight,sunshade + fan + cooling pad,sunshade + skylight + fan),respectively,and conduct the overall assessment on the measures to cool the summer agricultural greenhouse,in order to provide a reference for selecting a cost-effective cooling method for greenhouse. Tests show that the three treatment modes of fan,sunshade and sunshade + fan almost have no cooling capacity; skylight,sunshade + skylight have cooling capacity,but the effect is slow; cooling pad + fan,sunshade + skylight +fan can reduce the indoor temperature,but the effect is not very good; skylight and fan have good cooling effect; sunshade + fan + cooling pad has obvious cooling effect,which can well meet the cooling needs in the summer greenhouse. 展开更多
关键词 Agricultural production multi-span greenhouse Temperature adjustment equipment Cooling capacity Economic benefit
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Research on dynamic characteristics model test scheme for middle pylon of multi-pylon multi-span suspension bridges
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作者 Zhang Yufeng Zhang Dachang 《Engineering Sciences》 EI 2012年第3期64-71,共8页
Multi-pylon multi-span suspension bridge is a new type super flexible structure system, and the rigidity design of middle pylon is one of the main difficult technical issues. Due to the requirements of longitudinal ri... Multi-pylon multi-span suspension bridge is a new type super flexible structure system, and the rigidity design of middle pylon is one of the main difficult technical issues. Due to the requirements of longitudinal rigidity, the structural form and the corresponding foundation type of middle pylon are different from those of the ordinary steel pylon, and the complicated dynamic characteristics make the calculation quite difficult. In this article, exploration has been made in selection of similarity ratio and model materials, section simulation, restriction conditions simulation, fixing of mass blocks, fabrication scheme and testing method by taking into account different construction and working conditions such as restriction conditions and working environment of a three-pylon suspension bridge, to conduct the test experimental design of the dynamic behavior of the middle pylon, with the purpose to reveal its dynamic characteristics and make comparison and analysis with theoretical assumptions, to provide basis for anti-wind and anti-seismic design and reference for the design and research of three-pylon two-span suspension bridges in the future. 展开更多
关键词 multi-pylon multi-span suspension bridge middle pylon dynamic characteristics model test
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FE Dynamic Analysis Using Moving Support Element on Multi-Span Beams Subjected to Support Motions
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作者 Yong-Woo Kim Seoung Yeal Lee 《Modern Mechanical Engineering》 2015年第4期112-121,共10页
In the present study, finite element dynamic analysis or time history analysis of two-span beams subjected to asynchronous multi-support motions is carried out by using the moving support finite element. The elemental... In the present study, finite element dynamic analysis or time history analysis of two-span beams subjected to asynchronous multi-support motions is carried out by using the moving support finite element. The elemental equation of the element is based on total displacements and is derived under the concept of the quasi-static displacement decomposition. The use of moving support element shows that the element is very simple and convenient to represent continuous beam moving, deforming and vibrating simultaneously due to support motions. The comparison between the numerical results and analytical solutions indicates that the FE result agrees with the analytical solution. 展开更多
关键词 MOVING SUPPORT ELEMENT SUPPORT MOTIONS Rayleigh-Damped Bernoulli-Euler BEAM multi-span BEAM Time History Analysis Finite ELEMENT Method
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Experimental research on the microclimate in the naturally ventilated multi-span greenhouse
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作者 Zhenjun Gao Wenyang Li +1 位作者 Wei Li Xiaoming Ding 《International Journal of Agricultural and Biological Engineering》 SCIE 2024年第3期68-74,共7页
In order to further understand the changing laws of environmental factors in large multi-span greenhouses under natural ventilation conditions and the internal relations between various environmental factors,and ultim... In order to further understand the changing laws of environmental factors in large multi-span greenhouses under natural ventilation conditions and the internal relations between various environmental factors,and ultimately improve the precision of microclimate regulation of large multi-span greenhouses.Taking the multi-span greenhouse with a small spire structure in the Demonstration Base of Guangdong Agricultural Technology Extension Station as the research object,under the condition of natural ventilation with butterfly-shaped windows,the changes in temperature,humidity,wind speed and solar light intensity of different monitoring planes in the greenhouse were monitored.After analyzing the monitoring data,it was found that:1)The temperature gradient in the vertical direction in the large multi-span greenhouse is more obvious than that in the small greenhouse,and the highest average temperature difference monitored can reach 7.9℃.The velocity field in the multispan greenhouse is always maintained within the range of 0.3-0.4 m/s,and the ambient wind speed has no effect on the airflow speed in the greenhouse.The humidity and speed in the multi-span greenhouse show good uniformity.2)In a large multi-span greenhouse,the secondary radiation generated by the internal shading has less impact on the area near the ground,which can effectively reduce the ground temperature.3)Under the conditions studied in this research,the temperature and humidity in the greenhouse follow the external environment as well,showing that the greenhouse design is reasonable,and the air renewal and heat exchange inside and outside the greenhouse are good during natural ventilation. 展开更多
关键词 natural ventilation multi-span greenhouse environmental factors MICROCLIMATE
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空间网格空腹夹层板结构创新与实践最新进展 被引量:1
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作者 陈红鸟 杨瑛 +4 位作者 田鹏刚 周正荣 陈靖 魏艳辉 马克俭 《应用力学学报》 北大核心 2025年第1期1-20,共20页
为了解决大跨度空腹网架结构抗剪刚度不足的问题,贵州大学马克俭教授于20世纪90年代创新地提出了空腹夹层板结构。通过减小竖杆的高宽比,使之形成“超短柱”,即剪力键,利用剪力键连接上、下肋协同受力,从而使空腹夹层板结构具有较大的... 为了解决大跨度空腹网架结构抗剪刚度不足的问题,贵州大学马克俭教授于20世纪90年代创新地提出了空腹夹层板结构。通过减小竖杆的高宽比,使之形成“超短柱”,即剪力键,利用剪力键连接上、下肋协同受力,从而使空腹夹层板结构具有较大的剪切刚度,其整体力学特性介于密肋井字楼盖与空腹网架之间。系统回顾了空腹夹层板结构的发展历程,介绍了该结构的组成和分类,总结了该结构的几何和力学特点,归纳了现有的理论分析方法与技术规程、结构优势及工程应用案例,尤其是2010年以后的工程实践进展;最后,对空腹夹层板结构体系的应用前景进行展望。空腹夹层板结构具有大跨度灵活划分空间、节约层高、降低结构自重、节省建筑用材、空腹可穿越管线等诸多优势,在全国30个省(市、自治区)的实际工程应用面积已达300余万平方米,节约建设资金超过2亿元。空腹夹层板结构体系的理论及实践创新体现了新时代的科技自立自强,采用多高层大跨度空腹夹层板楼盖结构可节约土地资源,对促进我国生态文明建设有重要意义。 展开更多
关键词 钢筋混凝土 空腹夹层板 大跨度结构 多高层建筑 网格结构
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考虑吊杆系统性失效的多跨下承式系杆拱桥强健性设计
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作者 范冰辉 孙绮 +1 位作者 陈宝春 陈康明 《交通运输工程学报》 北大核心 2025年第2期204-217,共14页
为研究吊杆系统性失效对下承式系杆拱桥产生的动力冲击效应,首先采用3种数值计算方法(LS-DYNA重启动法、生死单元法、全动力分析法)模拟吊杆断索效应,并与吊杆破断试验的动力响应数据进行对比,以选择最优的吊杆系统性失效模拟方法;其次... 为研究吊杆系统性失效对下承式系杆拱桥产生的动力冲击效应,首先采用3种数值计算方法(LS-DYNA重启动法、生死单元法、全动力分析法)模拟吊杆断索效应,并与吊杆破断试验的动力响应数据进行对比,以选择最优的吊杆系统性失效模拟方法;其次,为加强多跨下承式系杆拱桥结构的强健性和防连续性垮塌性能,提出先简支后连续结构、刚性整体式系杆拱结构2种形式的结构体系,采用失效模拟方法分析对比了结构改造前后吊杆系统性失效下剩余结构的动力响应,并利用Simple-Johnson-Cook模型对桥梁破坏过程进行仿真,获取结构最终破坏形态;在此基础上,探讨了吊杆系统性失效下结构的连续性垮塌破坏机理。研究结果表明:LS-DYNA重启动法的模拟结果与试验数据误差较小,能够更好地模拟吊杆瞬时破坏时的工况;先简支后连续结构在吊杆系统性失效下桥道系的最终破坏损伤程度最小,传力路径更长,可以有效地延缓结构的破坏历程,减小发生连续性垮塌事故的风险,为交通疏散争取时间;而刚性整体式系杆拱结构由于初始刚度较高,易引发应力集中,导致桥道系局部过早失效。因此,先简支后连续结构可适用于新建的多跨下承式系杆拱桥的设计,或可通过在墩顶设置可更换式节点,从而将其便捷地应用于既有桥梁的强健性改造中。 展开更多
关键词 桥梁工程 多跨下承式系杆拱桥 损伤失效模型 吊杆系统性失效 强健性设计 先简支后连续结构 刚性整体式系杆拱结构
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基于跨度和多层次特征融合的实体关系联合抽取
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作者 廖涛 许锦涛 张顺香 《阜阳师范大学学报(自然科学版)》 2025年第1期15-22,54,共9页
针对目前方法大多未能充分利用跨度语义信息和局部上下文隐含信息等问题,提出基于跨度和多层次特征融合的实体关系联合抽取模型。该模型首先将文本输入到预训练语言模型(Bidirectional Encoder Representations from Transformer,BERT)... 针对目前方法大多未能充分利用跨度语义信息和局部上下文隐含信息等问题,提出基于跨度和多层次特征融合的实体关系联合抽取模型。该模型首先将文本输入到预训练语言模型(Bidirectional Encoder Representations from Transformer,BERT)转换为词向量后,将其与通过图卷积获得的句法依赖信息进行融合,形成更丰富的文本特征;然后通过多头注意力层对文本特征进行加权处理,以此抑制噪声特征的干扰,并促进特征之间的交互,随后根据跨度将文本信息分割成跨度序列进行实体识别;最后使用双向门控循环单元提取局部上下文隐含信息,将与实体类型信息融合到候选实体跨度对并使用sigmoid函数进行关系分类。实验表明,该模型在SciERC数据集和CoNLL04数据集上取得良好的提升效果。 展开更多
关键词 实体关系 联合抽取 句法依赖 跨度 多特征融合 多头注意力
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大跨度多曲面异形钢桁架整体提升与吊装相结合施工技术
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作者 梅宇 谢熠 +2 位作者 刘渝琳 邓若峯 单振东 《建筑技术》 2025年第19期2327-2330,共4页
长沙西站建设条件复杂,施工场区邻近营业线,建设期间长株潭城际铁路正常运营,与其他单位交叉施工多,施工组织难度大。屋盖下方主体结构楼板薄,大型机械吊装、行走站位难。屋盖结构为多曲异形的正交空间钢桁架结构体系,钢屋盖体量大、构... 长沙西站建设条件复杂,施工场区邻近营业线,建设期间长株潭城际铁路正常运营,与其他单位交叉施工多,施工组织难度大。屋盖下方主体结构楼板薄,大型机械吊装、行走站位难。屋盖结构为多曲异形的正交空间钢桁架结构体系,钢屋盖体量大、构件截面尺寸大,单位延米重量大,结构层较高,节点设计复杂多样,整体安装精度要求高。通过采取大跨度多曲面异形钢桁架整体提升与吊装相结合的技术,确保了施工过程安全与质量。 展开更多
关键词 大跨度 多曲面 异形钢桁架 整体提升 体量大 复杂结构体系
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多跨弹性支撑燃料棒振动特性分析方法
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作者 丁育哲 李伟 +9 位作者 任全耀 李垣明 纪谢天 田文喜 章静 巫英伟 贺亚男 王明军 苏光辉 秋穗正 《核技术》 北大核心 2025年第4期182-189,共8页
为获取压水堆中多个定位格架约束下的细长柔性燃料棒的振动行为,建立了一种能够合理表征燃料棒动力学特性的振动分析方法,将格架约束作用等效成拉压弹簧及扭转弹簧,基于欧拉梁理论建立了多跨弹性支撑燃料棒力学模型,并构建了整段梁的位... 为获取压水堆中多个定位格架约束下的细长柔性燃料棒的振动行为,建立了一种能够合理表征燃料棒动力学特性的振动分析方法,将格架约束作用等效成拉压弹簧及扭转弹簧,基于欧拉梁理论建立了多跨弹性支撑燃料棒力学模型,并构建了整段梁的位移函数并结合能量原理法获得了振动模态;通过引入辅助项改善边界不连续现象并具有较好计算精度。基于上述方法分析了定位格架约束作用对燃料棒振动特性的影响规律:格架等效后的拉压弹簧刚度是燃料棒固有频率变化的主要影响因素,而扭转弹簧的影响仅在拉压刚度较高时显著。 展开更多
关键词 改进傅里叶级数法 多跨连续梁 振动特性 模态分析
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适用连栋智能温室大果型番茄品种长季节栽培适应性评价
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作者 邢慧颖 张馨苹 +7 位作者 李新旭 李树山 李常保 刘彤 陈怀勐 王绍辉 孙路路 杨瑞 《中国蔬菜》 北大核心 2025年第6期136-145,共10页
为了与进口大果型番茄品种Yarimaru比较,以国内3个番茄品种(502、H2106、H2103)为研究对象,通过对温室内环境因子的监测,分析了不同番茄品种在连栋温室长季节栽培下各时期的农艺性状、产量及果实品质的动态变化和环境因子之间的关系。... 为了与进口大果型番茄品种Yarimaru比较,以国内3个番茄品种(502、H2106、H2103)为研究对象,通过对温室内环境因子的监测,分析了不同番茄品种在连栋温室长季节栽培下各时期的农艺性状、产量及果实品质的动态变化和环境因子之间的关系。结果表明:进口番茄品种Yarimaru的株高在栽培期内高达8.23 m,单果质量115~288 g,果实硬度2.10~5.20 kg·cm^(-2),可溶性固形物含量为4.03%~5.43%,产量较其他3个品种高,为53.44 kg·m^(-2)。国产品种H2103单果质量为101~274 g,可溶性固形物含量较高,为3.46%~5.30%,产量为48.50 kg·m^(-2)。国产番茄品种502与H2106可溶性固形物含量分别为3.51%~5.13%、3.05%~4.60%,产量分别为45.26 kg·m^(-2)和44.26 kg·m^(-2)。Yarimaru的VC和番茄红素平均含量也高于其他3个品种。结合植株生长量和环境因子数据分析,Yarimaru每增长1片叶片需要有效积温较国产品种低,为19.62℃·d,需要累计光合有效辐射857.82μmol·m^(-2)·s^(-1)。这表明其在产量相对较高的情况下,每增长1片叶、每增长1穗果所需积温和光合有效辐射较低,减少能源的消耗,同时,国内品种H2103存在着一定的高产潜力。研究结果为连栋智能温室番茄种植品种选择、高效育种和长季节栽培资源利用提供了科学依据。 展开更多
关键词 连栋智能温室 大果型番茄 长季节栽培 环境因子 生物学性状 品质 产量
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多跨倾斜PC连续梁桥预拱度设置方法 被引量:1
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作者 廖宗熙 李元松 +1 位作者 叶绍其 郑和智 《城市道桥与防洪》 2025年第1期69-74,共6页
预拱度的设置关系到车辆高速运行的舒适性和安全性。为解决大跨径桥梁悬臂施工过程中桥梁预拱度线形不达标的问题,适应桥梁实际工程特点,提出一种考虑结构自重、预应力、收缩徐变效应、汽车荷载和温度效应等多种影响因素的预拱度设置和... 预拱度的设置关系到车辆高速运行的舒适性和安全性。为解决大跨径桥梁悬臂施工过程中桥梁预拱度线形不达标的问题,适应桥梁实际工程特点,提出一种考虑结构自重、预应力、收缩徐变效应、汽车荷载和温度效应等多种影响因素的预拱度设置和调整方法。以南昌某多跨倾斜PC连续梁桥为背景,基于设计文件和MIDASCivil程序,建立空间杆系结构纵向计算模型,对该桥的施工过程进行了模拟计算,得到了各节梁段的预拱度并用于指导施工。监控结果表明:大桥成桥线形高程与监控成桥高程误差符合规范要求,二者高差绝对值不超过20mm,所提方法理论清晰、简便可行。 展开更多
关键词 多跨PC连续梁桥 悬臂施工 数值模拟 预拱度设置方法 影响因子
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吊装重物脱钩后承重索的跳跃振动分析
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作者 许斌林 郭范波 +1 位作者 何根 田仲初 《振动与冲击》 北大核心 2025年第16期79-89,共11页
缆吊系统在吊装过程中由于吊钩突然跳舌或断裂会导致重物脱钩坠落,从而会使承重索产生跳跃振动,针对这类多跨连续悬索结构的跳跃振动问题,仍有待探究。为此,首先,基于单跨索随时间变化的振动规律与多跨连续索相同的原则,将承重索在支承... 缆吊系统在吊装过程中由于吊钩突然跳舌或断裂会导致重物脱钩坠落,从而会使承重索产生跳跃振动,针对这类多跨连续悬索结构的跳跃振动问题,仍有待探究。为此,首先,基于单跨索随时间变化的振动规律与多跨连续索相同的原则,将承重索在支承处进行切分,使其成为多个单跨索结构,从而建立各单索结构的振动微分方程;其次,根据各单跨索结构的动态平衡和变形协调原则,推导了承重索含固有频率的特征方程和振型函数;然后,以脱钩前的位置为初速条件,构建了重物突然脱钩后的滑动-跳跃模型,建立了承重索的主振动式和自由振动式;最后,结合梅溪河特大桥施工用的缆吊系统进行分析。结果表明:重物脱钩后,前3个周期内承重索频率和幅值随时间增加逐渐减少,从而产生了跳跃式振动,后面承重索频率开始趋于稳定,且1阶振动波形起主导作用,各点均是以相同的姿态进行简谐振动;吊重质量的变化不会改变承重索的非线性运动形式,但是会明显影响非线性振动频率和幅值;通过对主振动特征变化规律进行分析,发现缆吊系统的最不利脱钩位置位于十分点、二分点和四分点处。 展开更多
关键词 缆索吊装系统 脱钩 多跨连续索 主振动 跳跃振动
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薄膜连栋温室巡检植保无人机系统
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作者 亓颖颖 杨兴杰 +1 位作者 吕壹凡 岑峰 《农业工程学报》 北大核心 2025年第19期98-107,共10页
农用无人机已广泛应用于户外开放场景的农业生产,但在温室内的应用尚处于起步探索阶段。该研究提出一套在薄膜连栋温室内以自主飞行方式进行巡检和植保的四旋翼无人机系统。该系统采用RTK-GNSS(real-time kinematicglobal navigation sa... 农用无人机已广泛应用于户外开放场景的农业生产,但在温室内的应用尚处于起步探索阶段。该研究提出一套在薄膜连栋温室内以自主飞行方式进行巡检和植保的四旋翼无人机系统。该系统采用RTK-GNSS(real-time kinematicglobal navigation satellite system)结合双扩展卡尔曼滤波切换进行棚内环境下的精准定位;通过融合前向视觉和多向超声波,并对障碍物施加静态安全距离,实现近距离避障;通过采用高压扇形喷嘴和速度自适应变量喷洒控制系统,进行棚内植保喷洒。试验结果表明,无人机实现了薄膜连栋温室内自主飞行并可以近距离安全避障,避障过程中无人机与障碍物的最小距离上界值为(44±5.5)cm,作物巡检回传图像的水平位置误差小于±7 cm,对青菜黄条跳甲防治效果优于相同条件下的人工施药。采用该系统研制的四旋翼无人机在薄膜连栋温室内完成了以自主飞行方式进行巡检和植保的示范性应用,验证了薄膜连栋温室内采用自主飞行无人机进行作物巡检和植保的可行性及有效性。 展开更多
关键词 农业机械 薄膜连栋温室 无人机 巡检植保
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