苏通大桥——主跨1 088米的斜拉桥

介绍了苏通大桥设计和施工的工程构思,着重对群桩基础承载性能、河床冲刷防护及监测、上部结构施工抗风研究、中跨合龙方案及长悬臂结构施工控制方法等的关键技术和创新成果进行了总结和系统阐述.     

苏通大桥索塔深水群桩基础冲刷防护工程的设计与施工

从苏通大桥深水群桩基础结构方案出发,分析了冲刷及防护对大桥安全性的影响,进而从防护工程理念、结构设计与施工、防护效果监测等方面阐述了苏通大桥基础冲刷难题的解决方法.     

风力发电机塔筒晃动位移监测新方法

海上单桩基础风机塔的晃动位移是其安全监测与评估的重要参量,但是目前还没有较成熟的精确自动化监测方法.为此提出一种新的监测方法,首先基于动态高精度倾角仪测挠法得出其0～0.2 Hz范围内的准静态挠度曲线,然后利用低频振动位移传感器直接测量出其0.2 Hz～10 Hz范围内的周期性振动位移信号,最后把两种信号同步叠加成为塔...     

BP神经网络在风电塔筒裂纹AE源定位中的应用

针对常规无损检测方法难以对在役风电塔筒进行实时监测及检测效率低等问题,为实现在役风电塔筒的在线监测和塔筒裂纹源的定位。该文提出一种声发射检测技术与BP神经网络相结合的智能定位方法,研究声发射传感器分布对智能定位输出结果的影响。研究结果表明:该方法可有效解决风电塔筒裂纹声发射源的定位问题,为在役风电塔筒运行过程中的实时在线监测提供可靠依据;对于焊接结构对称且具有多条环焊缝的风电塔筒,声发射传感器的分布位置应避开塔筒构件的对称位置,以此提高智能定位输出结果的准确性,为在役风电塔筒检测时声发射传感器的合理、有效布置提供参考。     

光纤光栅传感技术在桥梁试桩中的应用

基于对光纤布拉格光栅(FBG)传感特性的理论分析,研制了可用于桥梁试桩应变监测的光纤光栅钢筋应变计,并进行了标定试验;研究了光纤光栅传感器的布设工艺,在某特大跨海大桥试桩项目中的钻孔灌注桩里成功地埋入了52支光纤光栅钢筋应变计,进行了荷载试验.研究结果表明,在桥梁试桩项目中利用光纤光栅传感技术可以方便有效地对试桩的应变进行多点实时监测,为桥梁桩基础的优化设计提供了可靠的依据.     

多波束水下地形测量系统在九江大桥抛石施工监测的应用

利用多波束水下地形测量系统,对九江大桥河床进行跟踪监测,通过分析每次监测数据,为九江大桥冲刷防护工程方案提供参考依据,及时掌握工程的动态变化,监测水下旌工质量,解决施工中的关键技术问题,指导防护工程实旅：通过防护工程的跟踪观测数据对设计和旌工方案的优化提供依据;提出相应验收标准的建议。     

基于二维波束聚焦算法的低速冲击监测研究

冲击损伤监测是结构健康监测的主要研究内容之一,为提高冲击定位的精度以及传感器的利用效率,提出了一种基于十字阵列型传感器布置方法的二维波束聚焦冲击定位算法,在高精度的前提下有效减少了传统定位方法所需布置的传感器数量。通过十字阵列型的压电传感器布置方法,可以将远场的定位精度大大提高,对于内场的盲区采用四点圆弧定位算法进行冲击定位,从而将整个大型平板结构的冲击定位精度大大提高。通过实验研究验证了该方法的有效性与实用性。     

洪水冲刷对重载铁路桥梁动力性能影响及加固技术

洪水冲刷可导致桥墩基础周围土体受到破坏,轻则降低基础承载能力和动力性能,重则导致桥梁垮塌事故发生,洪水冲桥墩问题直接影响铁路运营安全,冲刷是引起桥梁墩台失稳破坏的主要因素之一。以某重载铁路为工程背景,针对洪水冲刷作用下的浅埋式桩基础桥梁,开展冲刷对桥梁的动力性能影响规律和加固技术研究。结果表明:洪水冲刷引起桩基础出现不同程度外露,进而导致桥墩及主梁动力响应增大,随冲刷深度增加,桥墩墩顶横向振幅和桥跨跨中横向振幅等参数逐渐增大,而桥墩自振频率逐渐降低;桥墩振动增大直接导致主梁振动加剧,墩顶横向振幅及梁跨跨中横向振幅等多项动力性能参数与基础冲刷深度和列车速度均成正比;针对冲刷病害,提出了基于提高基础稳定性和整体加固目标的"增补桩基法+增大基础法"并完成实际工程应用,在加固前后进行动力性能试验,加固后桥墩及主梁横向振动明显降低,加固效果显著。     

风力发电机塔筒晃动位移监测新方法

海上单桩基础风机塔的晃动位移是其安全监测与评估的重要参量,但是目前还没有较成熟的精确自动化监测方法。为此提出一种新的监测方法,首先基于动态高精度倾角仪测挠法得出其0～0.2 Hz范围内的准静态挠度曲线,然后利用低频振动位移传感器直接测量出其0.2 Hz～10 Hz范围内的周期性振动位移信号,最后把两种信号同步叠加成为塔筒观测高程的晃动位移时程曲线。模型测试实验表明此方法的测量精度可达到毫米级别。基于实测数据,对2 座单桩风机塔筒在机仓对风向偏航时的晃动位移特性、台风作用下的晃动位移特性、正常工作及停机状态时晃动位移特性进行了详细的分析。分析结果表明：此方法可精确测量和分析出此类型塔筒的晃动位移频谱特性、幅值特性。     

基于Chan与Geiger混合算法的声发射源定位方法

Geiger定位算法是一种广泛应用的岩石损伤声发射源定位方法,但该算法受初始值影响较大,直接影响了算法的应用效果。文章充分挖掘Chan算法的特性,提出了一种混合Chan与Geiger算法的优化算法,利用Chan算法对损伤声源进行初始定位,再融合Geiger算法进行迭代解算。通过数值计算和断铅实验对所提出的混合算法进行理论分析和实验验证,结果表明：该混合算法简便、易行、结果可靠,能够有效提升声发射源定位算法的收敛速度和定位精度;在传感器数量较少时,该混合算法具有较强的适应性;在布设4个单维传感器的条件下,Chan与Geiger混合算法较最小二乘法与Geiger混合算法,定位结果更加精确,且迭代次数更少,能有效提高计算效率。该研究对于提高岩石、混凝土材料的损伤定位和健康监测的测算精度以及工作效率具有一定的促进意义。     

Fabrication and Characterization of Single-Layer Textile-Based Flexible Pressure Sensors for Smart Wearable Electronics Applications

Textile-based sensors have been widely studied for wearable monitoring. The sensor systems demand a large sensing area, flexibility, and scalable fabrication method. Herein, single-layer piezoresistive sensors are developed by a machine stitching technique using metallic and graphene nanoplatelets-coated conductive threads and fabrics. The pressure-sensing mechanism is based on measuring the electrical resistance due to the change in the contact area between the conductive thread and fabric as pressure on the sensor varies. The single-layer sensor design provides flexibility and overcomes the physical drift of the sensor during human activities, which enhances wearability and performance. The coated textiles are characterized by scanning electron microscopy and Fourier-transform infrared spectroscopy. Physical and electromechanical tests are performed on the sensors to evaluate their wearability and sensing performance. The sensors exhibit a wide working range of up to 100 kPa and good sensitivity with excellent durability against repeated mechanical deformations. The application potential of the sensors in real-time monitoring is demonstrated by embedding them into clothing as a wearable device. Moreover, the effectiveness of the sensors is tested for posture correction. This article suggests a novel technique to fabricate durable, flexible, and highly efficient pressure sensors for smart wearable applications.     

Embedded PZT Sensor for Monitoring Mechanical Impedance of Hydrating Cementitious Materials

An embedded PZT (Lead Zirconate Titanate)-based sensor is developed for real-time, continuous, in-situ monitoring of hydrating cementitious materials after casting. The development of a multi-layer protection for a PZT patch, which provides a physical barrier with the surrounding medium while ensuring the sensitivity of measurement is described. Electrical impedance measurements from the sensor embedded inside mortar mixtures of different compositions are shown to sensitively provide an indication of changes in the state and the mechanical impedance of the material during periods associated with setting and early strength gain. An analytical procedure is developed for extracting the mechanical impedance of the surrounding cementitious material from the electromechanical measurements of the embedded PZT sensor. Changes in the mechanical impedance of mortars through periods of setting and early strength gain obtained from the embedded PZT sensor are validated using pin penetration, isothermal calorimetry and vibration-based measurements. Kinetics of hydration reaction obtained from isothermal calorimetry and increase in the penetration resistance during the setting behavior in the material, are accurately reflected in the increase in the mechanical impedance of the surrounding mortar obtained from the embedded PZT sensor. The continued increase in the mechanical impedance of the mortar after setting, up to 28 days, correlates well with the increase in elastic modulus of material obtained from vibration-based measurements. The durability of the sensor protection scheme is verified by evaluating the performance of sensors recovered from inside the mortar after long-term embedment. The embedded PZT sensor offers the potential for monitoring the local property development in a cementitious material from within the bulk of the structure and for use in quality assessment.     

通过模态滤波实现阵列式传感器系统的故障诊断

基于结构振动响应特性利用改进的模态滤波方法对阵列式传感器系统进行故障诊断。在梁结构表面均匀布置一组加速度计,利用模态振型对该系统的输出信号进行重构,将重构信号与实际信号之间的曲率误差作为敏感参数,对系统中的模拟故障传感器进行检测与识别,并加以实验验证。数值计算和实验结果表明:改进的模态滤波方法不仅可以直接有效地对传感器系统进行实时故障监测,而且该方法与外界激励力位置无关,具有良好的工程应用前景。     

Highway Bridge Assessment Using an Adaptive Real-Time Wireless Sensor Network

A real-time wireless sensor network platform capable of maintaining lossless data transmission over several minutes of continuous, high-rate sampling is presented in this paper. The platform was designed specifically to provide the capability to enable expeditious system identification, as well as load rating of highway bridges without compromising the typical data acquisition parameters employed in comparable cable-based tests. Consequently, the hardware signal conditioning interface permits data collection from a variety of sensors typical to structural health monitoring, including accelerometers, strain transducers, and temperature sensors. The embedded software features a proprietary network transmission protocol capable of lossless, real-time delivery of up to 40 measurement channels at an effective sampling rate of 128 samples per second per channel. Documented in this paper is a field study on an end-of-service highway bridge in which ambient vibration monitoring was performed using 60 accelerometers interfaced with 30 wireless sensor nodes operating within one of two simultaneously operating star topology networks. In addition, an experimental load rating of the entire structure was performed through large-scale strain measurement facilitated by the same wireless sensor network platform.     

Flexible Hybrid Sensors for Health Monitoring: Materials and Mechanisms to Render Wearability

Wearable electronics have revolutionized the way physiological parameters are sensed, detected, and monitored. In recent years, advances in flexible and stretchable hybrid electronics have created emergent properties that enhance the compliance of devices to our skin. With their unobtrusive attributes, skin conformable sensors enable applications toward real-time disease diagnosis and continuous healthcare monitoring. Herein, critical perspectives of flexible hybrid electronics toward the future of digital health monitoring are provided, emphasizing its role in physiological sensing. In particular, the strategies within the sensor composition to render flexibility and stretchability while maintaining excellent sensing performance are considered. Next, novel approaches to the functionalization of the sensor for physical or biochemical stimuli are extensively covered. Subsequently, wearable sensors measuring physical parameters such as strain, pressure, temperature, as well as biological changes in metabolites and electrolytes are reported. Finally, their implications toward early disease detection and monitoring are discussed, concluding with a future perspective into the challenges and opportunities in emerging wearable sensor designs for the next few years.     

Optical Intensity-Based Measurement of Multipoint Hetero-Core Fiber Sensors by the Method of Time-Differentiation in Optical Loss

In this paper, we propose the multipoint optical intensity-based measurement of tandem connected intrinsic fiber-optic sensors by means of monitoring time-differentiation in optical loss. The use of hetero-core sensors can make it possible that a simple optical intensity-based measurement combined with a time-differentiation method could be facilitated for the multipoint measurement because the hetero-core technique has a low insertion loss and a sizable loss change in the tandem usage. Addressing multi-sensors has been successfully demonstrated including one displacement sensor and two contact sensors, which are located along a single transmission line in real-time basis. The gait system is also efficiently improved to monitor the knee flexure and the sole contact sensors located in a single transmission line with a mirror at the terminal end of fiber in order to simplify the measurement system for unconstrained monitoring.     

Nondestructive Evaluation on Strain Sensing Capability of Piezoelectric Sensors for Structural Health Monitoring

A kind of strain-sensing-based piezoelectric sensor was fabricated, and the mixture of cement powder and epoxy resin was used as the packaging layer. A nondestructive strain sensitivity testing method based on strain-sensing capability of piezoelectric sensor is presented. The theoretical foundation indicates that output voltage of piezoelectric sensor and strain of structure keep linear relationship when corresponding parameters are ascertained. Quasi-static responses and low-frequency (0–40 Hz) dynamic responses of piezoelectric sensors and strain gauges are analyzed. The results show that the piezoelectric sensors are sensitive and can accurately reflect the strain variation of structures. The quantification of output voltage and strain is investigated, and quasi-static and dynamic sensitivities were acquired (159.52–515.48 mV/με). With increasing of vibration frequency, the area of hysteresis loop decreases, and the strain sensitivity of sensor increases. Combining sensitivities with output voltages of sensors, the strain variation of structures could be obtained, which exhibit great application potentials of piezoelectric sensors for structural strain monitoring in low-frequency vibrations in civil engineering.     

旋涡进动流量计传感器的安装对测量的影响

 用自行设计的流量计实验台，对50 mm El径旋涡进动流量计上不同的压电式压力传感器安装方式进行了试验．结果表明，传感器安装对测量结果有显著影响．并给出了较佳的传感器安装方式和传感器的设计准则．     

自供能柔性氧化石墨烯湿度传感器的喷墨印刷制备及性能研究

呼吸频率及呼吸模式检测可用于医疗诊断以及人体健康评估。传统的医学检测器件体积大、能耗高、使用不便捷。针对高性能、低成本、便携式电子产品的迫切需求, 本工作利用氧化石墨烯材料自发极化后对湿度敏感的特性, 通过喷墨印刷方法制备了一种可以实现自供能的平面型湿度传感器。所制备的传感器对湿度响应呈现为线性关系, 并且具有优异的灵敏度、快速响应和恢复特性、多次循环稳定性和长期老化稳定性等特性。基于该传感器可以实现对于人体呼吸频率和呼吸模式等的检测。制备的湿度传感器具有制作简单、成本低、不易受人体行动及外界环境干扰等优点, 适用于实时监测呼吸频率和呼吸模式。     

Piezoelectric Glass-Fiber-Reinforced Polymer Sensor for Structural Health Monitoring and Stiffness Sensing

Strengthening and repairing infrastructure with fiber-reinforced polymers while achieving low-cost, real-time monitoring of cracks in engineering structures is highly challenging. Herein, a piezoelectric glass-fiber-reinforced polymer (piezo-GFRP) sensor is used to monitor the mechanical behavior of cement beams with cracks under cyclic bending. The output voltage and frequency of the sensor are shown to be effective feedback signals for determining the mechanical behavior. The thin piezo-GFRP sensor shows sufficient piezoelectric sensitivity to monitor the slight variations in the mechanical behavior of the cement beams during the early stages of cracking. It is indicated in this result that such sensors have the potential for the multifunctional structural health monitoring of engineering structures.