ITA study of non-destructive methods of inspecting and testing tunnel linings

The International Tunneling Association's Working Group on Maintenance and Repair of Underground Structures is preparing a report dealing with non-destructive methods of inspecting and testing tunnel linings. This request for information details the scope of the group's work and the types of information the group is seeking at this time.     

基于级联长周期光纤光栅的光纤布拉格光栅振动传感器的动态解调

提出一种基于级联长周期光纤光栅(CLPG)的光纤布拉格光栅(FBG)振动传感器动态解调方法。宽带光源发出的光经FBG反射后,进入到CLPG,经过CLPG调制后FBG反射光强会发生变化。通过温度测量实验对监测系统进行静态标定,再将FBG传感器粘贴于铝板表面,采用该系统监测简支铝板结构在低频和高频下的振动信号。系统采集到的动态信号时域波形及频谱与涡电流位移计的测量结果相吻合,表明该监测系统可实现2kHz以下的动态信号测量。     

非对称变形构件中无粘结预应力筋极限应力的计算

目前结构设计中使用的无粘结顶应力筋极限应力计算式均为经验公式.由于这些经验公式所依据的统计数据系来自试验条件单一的对称加荷简支构件,所以就不适用于悬臂类一梁非对称变形构件中无粘结筋极限应力的计算.本文推导出了悬臂构件中无粘结筋极限应力的计算公式,井对单跨构件中非对称变形对无粘结筋极限应力的影响从理论上进行了分析,为无粘结预应力非对称变形构件的抗弯强度设计提供了关键变量——无粘结筋极限应力的实用计算方法.     

建筑结构双线性基础隔震体系地震反应的参数研究

本文提出了基于SIMULINK和STATEFLOW的双线性隔震体系仿真分析方法,分析了双线性隔震体系反应对体系参数的敏感性,给出了双线性隔震体系反应与其基本参数的关系谱图。研究表明:屈服系数和第二隔震周期是影响双线性隔震体系反应的主因子,而第一隔震周期对体系反应的影响相对较小;隔震体系最优屈服系数与输入地震动水平相关;隔震体系反应与其基本参数的关系谱图呈现出明显的非线性特征,基本参数在较高水平存在较大的交互作用。     

Stiffness requirement of flexible skin for variable trailing-edge camber wing

The method for analyzing the deformation of flexible skin under the air loads was developed based on the panel method and finite element method.The deformation of flexible skin under air pressures and effects of the local deformation on the aerodynamic characteristics were discussed.Numerical results show that the flexible skin on the upper surface of trailing-edge will bubble under the air loads and the bubble has a powerful effect on the aerodynamic pressure near the surface of local deforma-tion.Then the...     

纤维缠绕复合材料环形容器设计优化(英文)

纤维缠绕环形容器可充分利用空间,节省结构质量和消除系统质心漂移,目前在很多工业领域中发挥着日益重要的作用。本文基于复合材料层合理论和测地线缠绕原理,提出了纤维缠绕环形压力容器的线型优化设计方法。应用微分几何,导出了圆环面上测地缠绕轨迹和纤维不架空判据。以初始缠绕角和缠绕层厚度为变量,对结构重量进行最小化设计,得到了对应于不同管径比的优化缠绕线型。对优化线型进行了计算机缠绕仿真,并给出了缠绕铺层的各向正轴应力分布。结果表明,优化设计的缠绕线型模式精确可靠,满足纤维缠绕的基本要求。纤维缠绕角度大小更趋于合理,从而能充分发挥缠绕结构的力学性能,减经系统重量,使优化得到的环形容器结构性能比传统测地线缠绕环形容器有很大提高。本文的设计计算方法可直接用于复合材料环形气瓶的初步设计。     

大跨度楼面人群荷载作用响应分析

以某大跨度钢-混凝土组合楼板模型为对象,采用ANSYS程序进行动力时程分析,研究人群荷载作用下,荷载布置方式、结构阻尼比、楼板边界条件、楼板长宽比和人群步行方式等因素对大跨度楼面结构振动响应的影响,分析大跨度楼板的人群动力响应特性。研究结果表明：不利布载形式为中间板带附近布置人群荷载;楼板长宽比越大则楼面结构响应峰值越小;连续步行荷载作用的楼板振动响应大于原地踏步荷载的响应;楼板边界约束越强振动响应越小;增大阻尼比能显著减小人致振动。     

Fluid Pump Using a Bar-shaped Piezoelectric Transducer

There are two kinds of piezoelectric pumps:check valve pumps and valve-less pumps.Whether to use a check valve or not depends upon the application occasion.To achieve large backpressure for higher flow rates,the pump with check valve is desirable.However,adding check valves implies more complex structure and higher probability of valve blocking,etc.In order to solve the problem,effective driving and transport mechanics with compact construction and reliable service are being sought.In this paper,using the second-order longitudinal vibration mode of a bar-shaped piezoelectric vibrator for driving fluid,a piezoelectric pump is successfully made.The proposed piezoelectric pump consists of coaxial cylindrical shells and a bar-shaped piezoelectric vibrator,which has a disk part and a cone part.The lead zirconium titanate ceramic rings fixed in the vibrator are polarized along the thickness direction.When the second-order longitudinal vibration of the vibrator along its axis is excited,the disk part of the vibrator changes periodically the volume of the chamber and the cone part acts as a pin valve,driving the fluid from the inlet port to the outlet port.Finite elements analysis on the proposed pump model is carried out to verify its operation principle and design by the commercial FEM software ANSYS.Components of the piezoelectric pump were manufactured,assembled,and tested for flow rate and backpressure to validate the concepts of the proposed pump and confirm the simulation results of modal and harmonic analyses.The test results show that the performance of the proposed piezoelectric pump is about 910 mL/min in flow rate with a highest pressure level of 1.5 kPa under 400 V peak-to-peak voltage and 51.7 kHz operating frequency.It is confirmed that this bar-shaped piezoelectric transducer can be effectively applied in fluid transferring mechanism of pump through this research.     

不平衡电桥的自动平衡和测量

电桥是一种结构简单的检测电路,准确度和灵敏度都较高,广泛应用于检测仪器中.本文在分析电路原理及熟悉数字电位器、A/D转换芯片的基础上设计了电桥自动平衡和自动测量电路,按照这种设计整个平衡过程不需控制电路的参与,节省了CPU的调节时间.并讨论了电路设计中的关键问题.