埋光纤光栅传感器智能土木结构应变监测

采取与土木工程施工特点相适应的操作工艺与保护方法，将光纤Bragg光栅传感器埋入钢筋混凝土结构中，分别在实验室和实际工程施工现场对混凝土内部的应变进行了测量。实验中光纤Bragg光栅传感性能良好，能够监测混凝土内部应变状态，显示出成活率高、绝对值测量、寿命长等优势，为建立基于光纤传感器的结构健康监测系统奠定了基础。     

分布式光纤裂缝检测的有限元分析及试验

对分布式光纤裂缝检测技术中光纤-混凝土复合体的微观力学行为进行了分析. 考虑了涂覆-护套、护套-混凝土双界面的状态非线性,混凝土采用双线性各向同性强化模型以消减局部应力集中,避免护套-混凝土之间的过度穿透. 采用试验确定的接触对力学参数,用ANSYS进行了数值模拟,得到了光纤-混凝土复合体的微观应力分布及光纤的曲率分布. 定量分析了缝宽与弯曲损耗的关系,计算结果与试验结果符合较好,从理论上验证了光纤布置方式、护套厚度对传感灵敏度和动态范围的影响,为分布式光纤裂缝检测技术提供了修正的微观力学分析理论和方法.      

埋入混凝土的光纤传感器包层力学特性研究

本文用解析解探索光纤传感器埋入混凝土中其包层的特性及重要性。针对外荷载平行与光纤方向施加于混凝土构件时，其包层的材料特性和厚度变化而引起其内部应力分布特性作了一些研究。从解的分析可以看出，在埋入光纤的附近横截面应力集中很大程度上取决于包层的厚度及材料性质。对于给定的混凝土材料存在包层材料和厚度相结合的优化问题，选择某一优化目标，可能减小或消除其应力集中，而这对于光纤传感器在整个运行期间是至关重要。     

光纤光栅传感器对钢筋混凝土内部应变的测量及温度效应的研究

本文应用光纤光栅传感器实现了对钢筋混凝土试件内部应变的测量．试验不仅就应用光纤光栅进行混凝土结构内部应变测量的技术、工艺进行研究，还通过设计温度控制试验，考察了光纤光栅传感器的温度补偿问题，以及横向应变对测量结果的影响．     

光纤光栅传感器在大体积混凝土基础温度监测中的应用

光纤光栅传感器具有体积小、质量轻、灵敏度高、耐腐蚀、抗电磁干扰、传输频带较宽、易于进行分布式测量等诸多其他传感器所不具备的优点,更适用于现场的长期健康监测。大体积混凝土在施工过程中的温度问题如处理不当将会引起混凝土开裂。利用温度计、热电耦等作为传感器的传统的检测手段已经大大的制约了数据的准确性与精度。寻求一种高精度温度检测手段已经成为用于现场结构监测的前提。本文结合具体的工程实例介绍了光纤光栅传感器在基础混凝土温度监测中的应用,介绍了监测系统的组成,传感器的构造和标定,并利用实测温度预测基础混凝土底板中温度应力,及时采取措施防止混凝土的开裂。     

绞合式光纤应变传感器

研究了一种可用于工程结构状态监测的本征型强度调制光纤应变传感器,由两根以上多模光纤相互绞合形成,分析了该传感器的应变传感原理,得到其既能测量拉应变,又有测定压应变的结论,传感器对应变的响应具有良好的线性和重复性、灵敏度高、无迟滞现象,对钢筋拉应变、混凝土压就矿业的实验结果与理论分析一致,表明该传感器是适合土木工程测量、结构状态监测等方面的较为理想的光纤传感器。     

混凝土内部应变光纤测量结果及分析

本文采用迈克尔逊（Michelson)光纤白光应变测量干涉系统,利用新型光纤传感探头,对混凝土内部的一维和二维应变状态进行了测量,给出了混凝土试件单轴和两轴的力学实验结果并与Instron8505液压伺服材料实验机得到的结果进行了比较和分析。     

钢管混凝土拱桥界面脱空光纤传感研究

基于光时域反射技术，进行了分布式传感光纤检测拱桥钢管混凝土交界面脱空的研究。通过试验确定了光纤在钢管内的布置型式和保护型式，使得光纤能在钢管内准确定位并有效保护，实际工程中存活率达到80％；构建全自动力-光耦合试验系统，进行了交界面脱空传感试验和预应变大比尺钢管混凝土界面脱空仿真试验，建立了力-光耦合本构关系，试验中脱空初始感知开度达到0．1mm，动态范围达到4．8mm，脱空定位达到0．2m。在首次布设光纤传感监测系统的拱桥工程中，检测到大面积脱空，并确定了脱空开度、位置及范围，对于提升大型桥梁工程无损检测水平具有实用意义。     

FRP混凝土结构力学性能的实验研究

本文首次引入基于马赫—曾德(Mech—Zehnder)原理的全光纤应变传感器系统到FRP混凝土结构的力学性能研究中，通过四点弯曲试验来测量试件内部的应力应变状态，并结合电测结果进行综合分析，为进一步的理论分析和计算奠定了实验基础．     

一种高精度光纤陀螺用光子晶体光纤设计

为了解决光子晶体光纤陀螺中高阶模致非互易性问题,设计了一种用于高精度光纤陀螺的单模保偏光子晶体光纤。为获得光纤结构参数最优区域,基于全矢量有限元方法开展了光子晶体光纤模场分布、双折射特性和限制损耗与三个重要结构参数(归一化频率、空气填充比、大孔直径)的依赖关系数值仿真分析。以传统熊猫型保偏光纤特性为参照,确定了光子晶体光纤结构参数最优区域。采用优化的光子晶体光纤绕制了1500 m环圈并装配于陀螺,对陀螺进行了相应测试。未采用温度补偿措施下,陀螺全温零偏稳定性优于0.008 (°)/h (100 s, 1σ),表明这种光子晶体光纤适用于高精度光纤陀螺。     

水坝瞬态热传导分析中的拟初始条件边界元法

使用一种时域边界元方法对混凝土水坝进行瞬态热传导分析。在对时间积分进行离散计算时,采用一种拟初始条件法,即在时间步迭代计算的过程中,将之前计算结果对当前时间步的影响都视作当前时间步的初始条件。在所取时间步长较小的情况下,这种处理方法容易导致数值结果不稳定,即每一步的计算误差会累计放大,最终导致计算崩溃。本文提出一种虚拟时刻方法以缓解这类数值不稳定现象,在该方法中,时间步长首先放大至合适尺度,计算某个虚拟时刻(往往在真实计算时刻之后)的温度和流量分布,再通过插值方法换算出真实时刻的温度和流量分布。在虚拟时刻点上的温度和流量计算过程中,边界已知温度或流量由真实时刻的温度或流量进行外插得到。本文简单证明了该方法在温度和流量随时间呈线性变化情况下的正确性,最后给出了两个分析实例,验证了该方法的准确性和稳定性。     

铸件凝固温度场有限元分析中界面热阻的处理

提出一种处理铸件与铸型界面热阻问题的虚拟界面单元法，并给出了有限元计算公式。由于该公式不显含单元厚度(△l)，故该单元厚度△l可取任意值。当△l取为零时，使问题处理变得极为方便。针对某一具体金属型铝合金活塞的铸造凝固过程，按考虑和不考虑铸件与铸型间热阻影响两种方法作了有限元计算，通过与实测值相比较，本文提出的算法其计算精度远高于不考虑铸件与铸型间热阻影响的计算结果。另外．该方法使有限元建模方便、通用性强。     

On the Dirichlet problem for quasi-linear elliptic equation with a small parameter

In this paper we deal with the Dirichlet problem for quasilinear elliptic equation with a small parameter at highest derivatives. In case the characteristics of the degenerated equation are curvilinear and the domain, where the problem is defined, is a bounded convex domain, we offer a method to construct the uniformly valid asymptotic solution of this problem, and prove that the solution of this problem really exists, and being uniquely determined as the small parameter is sufficiently small.     

空间框架建筑结构静力分析的超级元法解

本文发展一种建筑结构简化计算的新方法，这种方法的整体结构分析按其连续化分单元（超级元）进行，但单个构件又按常规有限元计算，故应用于复杂的空间框架结构提供了一种自由度及工作量极少又适用性强的高效实用分析方法，可望在微机上实现。     

The solution of large deflection problem of thin circular plate by the method of composite expansion

In this paper, the method of composite expansion in perturbation theory is used for the solution of large deflection problem of thin circular plate. In this method. the outer field solution and the inner boundary layer solution are combined together to satisfy all the boundary conditions. In this paper, Hencky’s membrane solution is used for the first approximation in outer field solution, and then the second approximate solution is obtained. The inner boundary layer solution is found on the bases of boundary layer coondinate. In this paper, the reciprocal ratio of maximum deflection and thickness of the plate is used as the small parameter. The results of this paper improves quite a bit in comparison with the results obtained in 1948 by Chien Wei-zang.     

两类网格结构模型的预处理方法

针对参考节点分别为q=3和q=4的网格结构模型,设计了两种预处理方法:以块对角逆为预条件子的共轭梯度法(BPCG)及以块下三角逆为预条件子的PGMRES法。数值结果表明,BPCG法对q=3具有很好的求解效率和鲁棒性,但对q=4的情形,特别是当α很小时,其求解效率将变得很差。当α很小时,以块下三角逆为预条件子的PGMRES法对求解q=4的蜂窝状结构在计算CPU和算法稳定性等方面均全面占优。在这两种预处理方法中,利用了基于标量椭圆问题的GAMG法求各个子块矩阵的逆,以提高内迭代运算效率。近似连续方程的建立为内迭代方法的合理性提供了有效的理论支撑。     

On the optimal shape of compressed rotating rod with shear and extensibility

In this paper, the optimal shape of a compressed rotating rod which maintains stability against buckling is presented. In the rod modeling, extensibility along the rod axis and shear stress is taken into account. Using Pontryagin's maximum principle, the optimization problem is formulated with a fourth order boundary value problem. The optimally shaped compressed rotating (fixed-free) rod has a finite cross-sectional area on the free end. This shape is qualitatively different from that suggested by the Bernoulli-Euler theory with zero cross-sectional area on the free end. In addition, the Bernoulli-Euler theory overestimates the buckling load, and this effect is more significant in the optimally shaped rod than for the corresponding constant cross-sectional rod consisting of the same material volume and length. In order to show this effect, it is necessary to use a generalized constitutive model which takes real material properties, such as axial extensibility and shear stress into account. Particularly, the solution of this generalized problem, obtained for thin rods, approaches the classical solution predicted by the Bernoulli-Euler theory.     

Simulation and hybrid fuzzy-PID control for positioning of a hydraulic system

Accuracy and precision of position control of hydraulic systems are key parameters for engineering applications in order to set more economical and quality systems. In this context, this paper presents modeling and position control of a hydraulic actuation system consisting of an asymmetric hydraulic cylinder driven by a four way, three position proportional valve. In this system model, the bulk modulus is considered as a variable. In addition, the Hybrid Fuzzy-PID Controller with Coupled Rules (HFPIDCR) is proposed for position control of the hydraulic system and its performance is tested by simulation studies. The novel aspect of this controller is to combine fuzzy logic and PID controllers in terms of a switching condition. Simulation results of the HFPIDCR based controller are compared with the results of classical PID, Fuzzy Logic Controller (FLC), and Hybrid Fuzzy-PID controller (HFPID). As a result, it is demonstrated that Hybrid Fuzzy PID Controller with Coupled Rules is more effective than other controllers.     

Evolution of fabric tensors in damage mechanics of solids with micro-cracks: Part I – Theory and fundamental concepts

The evolution of fabric tensors based on micro-crack distributions is formulated based on sound thermodynamic principles. In Part I of this work, the exact definition of fabric tensors based on micro-crack distributions is presented. This definition is seen to incorporate both the orientation and length of a micro-crack. In this regard, the micro-crack distribution is assumed to be radially symmetric, i.e. symmetric about a line through the origin.The equations of thermodynamics are employed in order to derive the exact evolution equations of the fabric tensors defined in the first part. In this regard, a thermodynamic force that is associated with the fabric tensor is defined and utilized in the derivation of the evolution equations. The application of the theory to the case of uniaxial tension is derived in Part II (companion paper) of this work.