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241.
This paper presents a parametric study on the stress concentration factors (SCFs) on the chord member in tubular X-connections reinforced with fiber reinforced polymer (FRP) under out-of-plane bending moment. For this aim, a FE model was generated and validated using several available experimental tests. After that, a set of 276 FE models was created to evaluate the effect of the FRP (layer number, orientation, and material) and joint geometry (γ, τ, and β) on the SCFs. In these FE models, the contact between the FRP sheets and the steel members (chord, weld, and braces) was modeled. Results indicated that the rise of the FRP laminate number causes a notable drop of the SCFs, especially in the connections with big γ. Moreover, the increment of the elastic modulus of FRP along the fibers causes a notable decrease of the SCF. Results showed that, for certain geometrical parameters set, the SCF in an X-connection retrofitted with carbon fiber reinforced polymer (CFRP) can be down to 23% of the SCF in the associated un-retrofitted connection. Despite the notable efficacy of the FRP sheets on the drop of the SCFs in the X-connections, there is not any study or equation on the X-connections with FRP. Therefore, an equation was proposed for quantifying the SCFs in the X-connections with FRP. 相似文献
242.
In this study, particulate matter was investigated as the primary pollutant in the air quality of Beijing Metro transfer stations, and passenger thermal comfort during the transfer process was evaluated by using the relative warmth index (RWI). Passenger thermal comfort level is not ideal in 87% of the measured space and is slightly hot overall, with an RWI range of 0.20–0.43. Although 20% of the measured space has lower values than ASHRAE’s cooling comfort class, the thermal comfort level of most measured space is good in winter morning rush hours, with an RWI range from −0.18 to 0.28. The particulate matter (PM) concentration is related not only to the season and spatial depth but also to the transfer design of the metro station. During the morning rush period, the concentration ranges difference of PM10 and PM2.5 in winter are 262.9 μg/m3 and 125.5 μg/m3, respectively, which are 1.43 and 1.46 times higher than those of in summer. There are significant differences in the PM concentration and RWI values between the island and lateral platforms of Beijing Metro transfer stations, and the design of the lateral platform is superior to that of the island platform. Another exploratory experiment is conducted to determine if the PM concentration has a potential effect on human metabolic rate. The data in this paper provide a valuable reference for further comfort research and environmental control in metro station, and the conclusions may guide the further underground space design of metro transfer stations. 相似文献
243.
本文提出了一种采用晶闸管元件构成的多相大功率永磁无刷直流电动机控制器的新方案.着重分析了这种新型控制器的工作原理和可靠换流过程,介绍了多单元驱动器同步控制方法,提供了基于80C196KC单片机为核心的控制单元的结构图,论文最后给出了样机的试验结果. 相似文献
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永磁电机的故障诊断和处理是提高舰船系统可靠性的关键。本文分析了永磁电机的基本数学模型,介绍了一种对永磁电机故障诊断方法,并得出了相应的结论。 相似文献
246.
季冻区道路经常发生冻胀、翻浆、开裂、不均匀沉降等一系列冻害现象,深入研究冻害因素对土体性质的影响,对季冻区工程建设及维护具有重要意义。文章以呼和浩特地区的类黏土为研究对象,通过冻胀率试验和无侧限抗压强度试验,检测土体降温速率及土体中盐浓度对冻土工程质量的影响,结果表明降温速率与盐浓度对类黏土性质的影响明显。 相似文献
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当今社会,汽车已经成为人们出行的重要交通工具,随着汽车保有量的增加汽车排气污染也变得日益严重,阴霾天、PM2.5就是最直接的影响,温室气体CO2的排放量也是一个很客观的量。因此,加强汽车排放污染的控制与治理是必须的。 相似文献
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