带预应力约束拉杆R-CFT短柱轴压性能试验研究

为了解约束拉杆预拉力对矩形钢管混凝土短柱受力性能的影响,进行了3个带预应力约束拉杆短柱轴压试验和另外2个对比试验,对比试验试件中1个不带约束拉杆,1个带普通约束拉杆。预应力约束拉杆和普通约束拉杆均由M20高强度螺栓组成,作为普通约束拉杆的高强度螺栓,在构件受轴向压力前与钢管壁焊接成一体;作为预应力约束拉杆的高强度螺栓,在构件受轴向压力前通过扭紧螺帽产生预拉力,然后与钢管壁焊接成一体,由拉杆预拉力对钢管壁和核心混凝土进行预压。试验结果表明,设置约束拉杆后,构件的承载力提高,轴向变形能力增强;与普通约束拉杆相比,预应力约束拉杆能减小构件最大荷载时的变形,但对构件承载能力和后期变形能力影响不大;减小预应力约束拉杆的横向间距,可有效减小构件最大荷载时的轴向变形,提高构件前期刚度,但对构件承载力影响不明显;在截面宽度和拉杆数量不变的情况下,随着截面长宽比的增加,构件后期变形能力减小。     

光纤光栅传感技术在火灾报警系统中的应用

作者通过对光纤光栅火灾报警器原理的介绍,详述了这一新技术在工程应用中的优点,并通过实例分析阐述了该报警器在建筑设计中的应用。     

压应力对配筋煤矸石多孔砖墙片抗震性能的影响

通过对水平配筋煤矸石多孔砖墙片在不同压应力作用下的拟静力试验,研究了煤矸石多孔砖这种新型墙体材料在低周反复荷载作用下的力学性能,压应力对水平配筋墙片的影响,在不同压应力作用下水平钢筋强度发挥效能。     

FRP筋长期耐腐性能的研究与发展

FRP筋除具有抗拉强度高、疲劳性能好、松弛率小等优良力学性能外,特殊环境下的耐腐蚀性能也明显优于钢筋,成为解决钢筋锈蚀问题的最佳选择。本文在系统地查阅国内外代表性研究文献的基础上,对FRP筋的耐酸碱盐、潮湿、紫外线和耐温耐火性能进行了研究和总结,并对今后拟开展的研究工作提出了建议。     

Fast Fourier and discrete wavelet transforms applied to sensorless vector control induction motor for rotor bar faults diagnosis

This paper presents new techniques to evaluate faults in case of broken rotor bars of induction motors. Procedures are applied with closed-loop control. Electrical and mechanical variables are treated using fast Fourier transform (FFT), and discrete wavelet transform (DWT) at start-up and steady state. The wavelet transform has proven to be an excellent mathematical tool for the detection of the faults particularly broken rotor bars type. As a performance, DWT can provide a local representation of the non-stationary current signals for the healthy machine and with fault. For sensorless control, a Luenberger observer is applied; the estimation rotor speed is analyzed; the effect of the faults in the speed pulsation is compensated; a quadratic current appears and used for fault detection.     

Induction Motors Broken Rotor Bars Diagnosis Through the Discrete Wavelet Transform of the Instantaneous Reactive Power Signal under Time-varying Load Conditions

Abstract—In this article, a method based on the application of the discrete wavelet transform to the instantaneous reactive power signal, for diagnosing the occurrence of broken rotor bars in induction motors operating under time-varying load conditions, is presented. This method is based on the decomposition of the instantaneous reactive power signal, from which wavelet approximation and detail coefficients are extracted. The energy evaluation of known bandwidths permits to de?ne a fault severity factor. This method has been tested through the simulation of an induction motor using a mathematical model based on the winding-function approach. These simulation results are complemented by experimental tests conducted on an induction motor with several faulty rotors that can be interchanged and both simulation and experimental results have shown the effectiveness of the proposed method for broken rotor bars diagnosis in induction motors even under time-varying load conditions.     

应对国家钢筋产品升级换代的对策研究

本文着重介绍国家淘汰强度335 MPa级钢筋前,现有钢筋生产工艺和成本分析,提出400 MPa/500 MPa钢筋生产工艺改进方案。     

连杆机构可视化设计和模拟研究

介绍连杆机构构件的建模方法和用ＡｃｔｉｖｅＸ技术实现连杆机构可视化设计和模拟的原理和过程。     

混凝土水平折梁的连续配筋构造

混凝土水平折梁当弯折不大时采用连续配筋，经济合理。在折角处按照假定的传力模型计算所需的附加横向钢筋，并合理配置。     

用超声波波速评估大电机主绝缘的剩余运行年数

为了有效评估大电机主绝缘的剩余寿命，对大量已运行16、18和23年的300MW发电机定子线棒进行统计最小波速Vmin和统计平均波速Vav的超声波波速测量试验，以及介质损耗角增量△tanδ、电容变化率△C／C0、最大放电量qmax、平均放电量qmean等电气测量试验，用线性回归分析对比研究了超声参数和电气参数与运行年数多的相关性。结果表明，Vmin和Vav与^↑y密切相关，△tanδ、qmax和qmean与^↑y相关性较弱，△C／C0与^↑y没有相关性，超声参数比电气参数能更准确评估绝缘状态；分别建立了Vmin和Vav与^↑y的二阶和三阶线性函数数学模型，提出了最可靠运行年数和置信度为95％的可靠运行年数的预测方法。