基于解析法的悬索桥上部结构施工控制程序开发

介绍了基于解析法的悬索桥上部结构施工控制专用计算程序的计算原理和流程,完善了悬索桥锚跨索股分析程序MKJS;利用Fortran和Visual Basic进行混合编程,实现了SBCC3.0的开发,其功能可满足悬索桥上部结构的施工控制计算。

大跨悬索桥非线性随机静力分析

大跨度悬索桥结构具有显著的几何非线性行为,且存在材料特性、几何尺寸的随机性.先对缆索采用较小抗弯刚度参数的梁单元,对悬索桥进行确定性的几何非线性分析;然后采用响应面法进行非线性随机静力分析;最后针对1座大跨悬索桥,计算了在竖向活载作用下材料、几何尺寸的随机性对主梁跨中位移的影响.结果表明,结构随机性的影响十分明显.

大跨度悬索桥的设计参数合理性研究

大跨度悬索桥是柔性大变形结构，在科技不断发展的今天，悬索桥的建设朝着更大更新颖的形式发展，也让桥梁设计者们面临着更多的技术挑战。以坭洲水道桥的比选方案为项目背景，建立有限元模型分析了各结构参数对单跨吊悬索桥受力I性能的影响，为以后的同类型悬索桥提供合理性的参考。

管道悬索桥上部结构的施工技术研究

为解决管道悬索桥上部结构施工问题,结合某管道悬索桥工程实际情况,对其上部结构施工技术进行深入分析,提出具体的施工方法和施工中需要注意的要点,以期为相关人员提供参考。

基于磁场强度检测的悬索桥缆索锈蚀风险概率计算方法

为了分析和评定服役期内悬索桥缆索结构的锈蚀状态及屈曲破坏风险概率,开展缆索结构的加速腐蚀试验,通过拟合得到磁场总强度与腐蚀失重率的关系。在已有的抗力概率模型和荷载概率模型研究的基础上,剔除次要因素,通过极限状态方程建立缆索结构锈蚀屈曲破坏风险概率计算方法。以某大跨径悬索桥为背景,根据三轴磁场强度检测结果,判断缆索结构的锈蚀状况,通过现场检测数据建立悬索桥有限元模型,计算缆索的抗力概率模型、荷载概率模型,从而得到悬索桥在当前缆索系统锈蚀状态下的破坏率。结果表明:随着试样腐蚀率的增加,磁场总强度呈现下降趋势,且其测值越离散。锈蚀评定方法能够较好地拟合磁场总强度和腐蚀失重率的关系。基于现场锈蚀评定和有限元模拟建立的悬索桥缆索结构锈蚀风险概率计算方法切实可行。

对斜拉桥总体设计参数的讨论

主梁的中边跨径比、跨高比、跨宽比、宽高比和主塔的有效跨高比是斜拉桥的总体设计参数。本文根据已建斜拉桥资料,对其进行了统计归纳,并对总体设计参数的常用范围及对结构性能的影响作了简要说明。

Measurement of wind field characteristics at a long-span suspension bridge

In order to provide a reliable basis for wind resistant evaluation of a long-span suspension bridge, a structural health monitoring system is installed on a bridge in the East China Sea and the simultaneous wind data at the bridge deck and at the top of the bridge tower are recorded. The average wind speeds and directions, variations of wind speeds with height, turbulent characteristics, spatial correlation and characteristics of wind flow around the bridge deck are analyzed by using statistical methods and spectral analysis. It is found that the average wind speeds along the bridge girder are almost identical; however, the mean wind directions vary greatly at different locations. The dimensionless exponent decreases as the average wind speed increases. The measured turbulence intensities are greater than the recommended values, and the turbulence power spectrum can well fit the standard spectrum. However, the measured spectral values are considerably smaller in low frequency ranges. The mean wind speed of the wake flow decreases and the turbulence intensity increases significantly, and the spectral characteristics of the wake flow change obviously while the feature frequency of vortex shedding has not yet been observed.

模糊贴近度在多目标优化中的应用—从非劣解中寻求最优解

求解多目标优化问题的方法一般是先求出问题的非劣解,再从许多非劣解中选取好解。本文在已有非劣解的情况下,提出了各非劣解相对于理想解的的隶属度公式。运用模糊贴近度的概念从众多的非劣解中找出最贴近于理想解的最优解。该方法运用于悬索管桥结构参数的多目标优化设计中,得出了非常满意的设计方案。

Operational modal identification of suspension bridge based on structural health monitoring system

An output-only modal identification method by a combination use of the peak-picking method and the cross spectrum methods are presented. Meanwhile, a novel mode shape optimum method of the deck is proposed. The methods are applied to the operational modal identification system of the Runyang Suspension Bridge, which can be used to obtain the modal parameters of the bridge from out-only data sets collected by its structural health monitoring system （SHMS）. As an example, the vibration response data of the deck, cable and tower recorded during typhoon Matsa excitation are used to illustrate the program application. Some of the modal frequencies observed from deck vibration responses are also found in the vibration responses of the cable and the tower. The results show that some modal shapes of the deck are strongly coupled with the cable and the tower. By comparing the identification results from the operational modal system with those from field measurements, a good agreement between them is achieved, but some modal frequencies identified from the operational modal identification system （OMIS）, such as L1 and L2, obviously decrease compared with those from the field measurements.

Spatial structural analysis of main saddle for single tower spatial cable self-anchored suspension bridge

Based on the engineering background of the Jiangxinzhou Bridge in Nanjing, issues related to the spatial main saddle of the self-anchored suspension bridge are studied. The refinement finite element model is established by the secondary development technology based on the platform of the general finite element program, and a reasonable load pattern is used in its spatial structural analysis, by which its path of force transference and stress distribution are obtained. Matched with the spatial main cable, the tangency point correction method is also discussed. The results show that the lateral wall stress of the saddle groove is higher than the stress within the wall due to the role of lateral forces in the finished bridge state; the horizontal volume force of the main cable can generate a gradient distributed vertical extrusion pressure on the saddle clamping device and the main saddle body; the geometric nonlinear effect of the self- anchored suspension bridge cable system in the construction process is significant, which can be reflected in the spatial tangent point position of the main cable with the main saddle changes a lot from free cable to finished cable.

Finite element analysis of dynamic stability of skeletal structures under periodic loading

This paper addresses the dynamic stability problem of columns and frames subjected to axially applied periodic loads. Such a structure can become unstable under certain combinations of amplitudes and frequencies of the imposed load acting on its columns/beams. These are usually shown in the form of plots which describe regions of instability. The finite element method (FEM) is used in this work to analyse dynamic stability problems of columns. Two-noded beam elements are used for this purpose. The periodic loading is decomposed into various harmonics using Fourier series expansion. Computer codes in C++ using object oriented concepts are developed to determine the stability regions of columns subjected to periodic loading. A number of nu-merical examples are presented to illustrate the working of the program. The direct integration of the equations of motions of the discretised system is carried out using Newmark’s method to verify the results.

Software development of modeling assistant for continuous suspension bridges with multi-pylon

Building a reasonable and accurate finite element model is the first and critical step for structural analysis of complicated bridge. In this article, modeling assistant for continuous suspension with multi-pylon is developed based on .Net platform, with VB.Net, C# language and OpenGL graphic technique. With parameterized modeling method, finite element model of this kind of bridge can be built quickly and accurately, and multi-type element modeling with uniform parameters is realized. With advanced graphic technique, three-dimensional model graph can be real-timely previewed for intuitive data check. With an example of practice project, the accuracy and feasibility of this modeling method and practicality of this software are verified.

Advanced aerostatic analysis of long-span suspension bridges

As the span length of suspension bridges increases, the diameter of cables and thus the wind load acting on them, the nonlinear wind-structure interaction and the wind speed spatial non-uniformity all increase consequently, which may have unnegligible influence on the aerostatic behavior of long-span suspension bridges. In this work, a method of advanced aerostatic analysis is presented firstly by considering the geometric nonlinearity, the nonlinear wind-structures and wind speed spatial non-uniformity. By taking the Runyang Bridge over the Yangtze River as example, effects of the nonlinear wind-structttre interaction, wind speed spatial non-uniformity, and the cable＇s wind load on the aerostatic behavior of the bridge are investigated analytically. The results showed that these factors all have important influence on the aerostatic behavior, and should be considered in the aerostatic analysis of long and particularly super long-span suspension bridges.

The mechanical response of multi-tower continuous-span suspension bridge deck pavement based on whole bridge analysis

The effect of multiple span suspension structure on the mechanical response of bridge deck pavement was studied, and finite element analysis (FEM) of stress and strain of pavement according to the bridge floor system features of super-long and high flexibility was made. Meanwhile, the FEM results were compared with those of the single span suspension structure. Three-stage analytic hierarchy process (AHP) is developed to analyze the mechanical response including whole bridge analysis, partial beams section analysis and orthotropic plate analysis. The most unfavorable load position was determined by the numerical solutions acquired from each stage to study the main mechanical index of multiple span suspension structure. The FEM results showed that the mechanical response numerical solutions by using the three-stage AHP are greater than those by simplified boundary condition, and the force condition of multiple span suspension structure is worse than that of the single span suspension structure.

Multi-type sensor placement and response reconstruction for structural health monitoring of long-span suspension bridges

This study is devoted to the experimental validation of the multi-type sensor placement and response reconstruction method for structural health monitoring of long-span suspension bridges. The method for multi-type sensor placement and response reconstruction is briefly described. A test bed, comprising of a physical model and an updated finite element （P-E） model of a long-span suspension bridge is also concisely introduced. The proposed method is then applied to the test bed; the equation of motion of the test bed subject to ground motion, the objective function for sensor location optimization, the principles for mode selection and multi-type response reconstruction are established. A numerical study using the updated FE model is performed to select the sensor types, numbers, and locations. Subsequently, with the identified sensor locations and some practical considerations, fiber Bragg grating （FBG） sensors, laser displacement transducers, and accelerometers are installed on the physical bridge model. Finally, experimental investigations are conducted to validate the proposed method. The experimental results show that the reconstructed responses using the measured responses from the limited number of multitype sensors agree well with the actual bridge responses. The proposed method is validated to be feasible and effective for the monitoring of structural behavior of longspan suspension bridges.

Optimal sensor placement in health monitoring of suspension bridge

Structural health monitoring(SHM) provides an effective approach to ensure the safety of structures.However,with the restriction of the cost of sensor system and data processing,only a small number of sensors could be available in the health monitoring system(HMS).In order to obtain the best identification of structural characteristics,optimal sensor placement(OSP) becomes an inevitable task in the design of HMS.This paper introduces the process for determining the OSP in HMS of a suspension bridge,in which four different OSP methods have been investigated,including the effective independence(EI) method,the effective independence driving-point residue(EFI-DPR) method,the minimized modal assurance criterion(minMAC) method and the principal subset selection-based extended EI(PSS-EI) method.Then,three criteria,which are modal assurance matrix(MAC),condition number(CN) of mode shape matrix and determinant of Fisher information matrix(FIM),were employed to evaluate the effect of the OSP methods respectively.The result showed that the PSS-EI method developed has the ability to guarantee the highest determinant of FIM,a relatively small off-diagonal term of MAC and agreeable CN,as well as the deployment of sensors in a uniform and symmetric fashion for the studied bridge.Finally,the scheme obtained by PSS-EI was adopted in the HMS.