边坡工程中监测数据场三维云图实时动态可视化方法

实现监测物理量空间数据场的三维实时动态可视化表达,是边坡工程安全监测三维可视化在线分析的关键。空间数据场三维可视化最直观的表达形式是三维云图,其绘制方法包括面绘制和体绘制,而体绘制方法是实现三维数据场实时动态云图绘制的首选方法。鉴于X3D灵活的场景交互和丰富的三维几何造型节点,通过生成用于监测数据场三维云图显示的几何载体TEN模型,在提取监测点坐标并形成监测数据场的基础上,应用空间插值算法得到TEN网格节点的监测物理量数值,并按照特定颜色表映射到网格节点的颜色域值,提出基于X3D技术的空间数据场三维云图体绘制方法。以某水电站坝肩边坡和某水电站谷肩堆积体为例,应用该方法实现边坡和堆积体监测数据场三维分布云图的实时动态可视化显示,直观地揭示监测对象的变形趋势和可能的变形破坏模式,为该方法在水利水电和岩土工程的边坡及地下工程安全监测领域的应用提供参考。     

受施工扰动影响土体力学参数的可视化分析方法

结合具体工程,对受施工扰动后土体力学参数分析中应用科学计算可视化分析的方法进行研究,结合体视化的算法思想,建立了受工程施工扰动土体力学参数变化的可视化分析研究方法,提出采用直接体视的算法来实现受工程施工扰动土力学参数可视化表示的解决方案。建立了用于受基坑工程施工扰动土体力学参数可视化分析的体数据V,体数据中包含了基坑外部土体的土力学参数和位移场的三维信息。按照不同的施工阶段,建立不同时间序列的系列体数据集,利用这些体数据集,可直接可视地分析施工每一工况下的坑外土体内各种土力学参数的变化和土体位移的变化。     

基于震害的钢筋混凝土框架结构倒塌机理的集成多媒体仿真研究

本文在总结历次实际地震震害特点的基础上,针对钢筋混凝土框架结构的特点,运用面向对象的建模理论建立了一套能模拟房屋倒塌过程的计算机模型,结合钢筋混凝土框架三维非线性动力有限元方法,给出了一种计算机能自动判断局部或整体可动机构的快速算法,并引入可视化技术及多媒体系统集成原理,开发了框架倒塌仿真的集成多媒体仿真系统,对钢筋混凝土框架结构房屋的倒塌机理作了研究,仿真实例表明该系统能较好地再现框架的倒塌过程。     

单层厂房排架结构地震反应分析的新方法

提出了一种新方法用来进行单层工业厂房排架结构地震反应计算 ,这种方法能够精确地计划数值化地震波作用下单层工业厂房结构的动力反应。新方法是利用分段插值多项式逼近任意动力荷载 ,当动力荷载也为分段多项式时 ,Duhamel积分是有精确解的 ,因而和传统逐步积分法相比 ,新法不但具有较高的计算精度 ,而且大大减少了计算工作量。     

Use of trigonometric interpolation for the analytical determination of the dynamic response of linear systems to arbitrary inputs

Commonly the loadings associated with the dynamic excitation of structural systems are expressed in the form of discrete time series. By the use of trigonometric interpolation these inputs may be transformed into continuous time functions. The dynamic response of a linear structural system when subjected to such inputs may be computed by modal analysis techniques. These methods require the solution of a set of uncoupled second-order linear ordinary differential equations with constant coefficients. The trigonometric interpolation function is a finite series of sine and cosine terms and hence it becomes a straightforward matter to solve the set of uncoupled differential equations for the displacements. Solutions obtained in this manner are also seen to be continuous functions expressed as finite series in sines and cosines. The associated velocities and accelerations may be easily obtained by differentiation of these expressions. The method is also free from the errors inherent in step-by-step integration methods, and the errors in the numerical determination of Duhamel integrals.The derivation of the coefficients of the time-series inputs and of the final evaluation of the dynamic response are both executed by a simple recursive algorithm which is fast and accurate.Since the only errors occur in the initial expression of the input a finite series of elementary functions—and these errors can be made very small—the method is a novel and attractive alternative to existing procedures. It is illustrated here by the computation of the dynamic response of a skeletal space frame when subjected to earthquake ground motions.     

Efficient solution of modal equations with arbitrary loadings

Commonly time-varying loadings such as wind, waves and earthquakes which act on engineering structures are specified in the form of discrete time-series. The dynamic response of a linear structural system when subjected to such inputs may be computed by modal analysis techniques. These methods require the solution of a set of uncoupled second-order linear ordinary differential equations with constant coefficients. Implicit to any solution used, however, is the requirement that the original loading be matched exactly or approximated closely by a continuous time-function. Frequently a piecewise linear interpolation of the discrete input data is adopted. This paper presents superior local interpolations which have been derived and optimised by considerations in the frequency domain. These local interpolations of the input are then subsequently used in conjunction with an exact solution to the modal equations. This implies that errors are due solely to the limitations of the interpolating process, a feature absent from numerical integration methods. By the use of discrete time-systems theory and the $\text{z}$ transform some simple recursive algorithms are derived for the solution of the modal equations. These algorithms, which operate linearly on the loading data, can be made very accurate, are unconditionally stable and are suitable for use with a hand calculator.The paper concludes with sections on methods of processing the discrete time-series loading data so as to increase or decrease the sample time step length. Increasing the step length can economise analysis when only low frequency components are of interest. Reducing the step length by inserting intermediate values is advantageous when high frequency components in the solution are of importance and in the direct solution of the matrix equations of motion. Simple but effective digital filters are specified for these operations, and in the case of sample rate increase (digital interpolation) the filters are much superior to linear interpolation.     

Design of reinforced concrete frames with damage control

A reinforced concrete frame design methodology to control damage indices in structural elements and keep them within tolerable limits is presented. The structural element strengths are determined to satisfy the basic design goal, which requires elastic behavior during moderate earthquakes and inelastic behavior with tolerable damage during strong earthquakes. Maximum lateral displacement and plastic dissipated energy are used as design parameters. The method uses several inelastic static analyses to optimize the strength of the structural elements in order to satisfy the adopted damage indices. The proposed method was applied to a six-floor framed structure, representative of an actual building, and the expected solution was achieved after two optimization cycles. The structure designed with the proposed method was subjected to eight earthquake acceleration records. Its response was determined from inelastic dynamic analysis. The resulting damage indices were similar to those assumed in the design, which confirm the accuracy of the proposed method.     

Efficient structural analysis of wall–frame structures

In this study, an efficient analytical model for the dynamic analysis of tall buildings with a shear wall–frame structural system has been proposed. A shear wall–frame structural system usually consists of a core wall showing flexural behavior and a frame presenting shear behavior. Therefore, the deformed shape of the shear wall–frame structural system is shown by the combination of flexural mode and shear mode. To consider this characteristic in developing an efficient analytical model, the effect of shear wall and frame on the dynamic behavior of a tall building with a dual system has been separately investigated. In order to consider the effect of the shear wall in the frame model without shear wall, a rigid body was used instead of the shear wall. Each equivalent model for the separated shear wall part and frame part has been independently developed, and two equivalent models were then combined to create an efficient analytical model for tall buildings with a shear wall–frame structural system. In order to verify the efficiency and accuracy of the proposed method, time history analyses of tall buildings with a shear wall–frame system were performed. With analytical results, it has been confirmed that the proposed method can provide accurate results with significantly reduced computational time and memory. Copyright © 2013 John Wiley & Sons, Ltd.     

Identification of Time-Variant Modal Parameters Using Time-Varying Autoregressive with Exogenous Input and Low-Order Polynomial Function

Abstract:   This work presents an approach that accurately identifies instantaneous modal parameters of a structure using time-varying autoregressive with exogenous input (TVARX) model. By developing the equivalent relations between the equation of motion of a time-varying structural system and the TVARX model, this work proves that instantaneous modal parameters of a time-varying system can be directly estimated from the TVARX model coefficients established from displacement responses. A moving least-squares technique incorporating polynomial basis functions is adopted to approximate the coefficient functions of the TVARX model. The coefficient functions of the TVARX model are represented by polynomials having time-dependent coefficients, instead of constant coefficients as in traditional basis function expansion approaches, so that only low orders of polynomial basis functions are needed. Numerical studies are carried out to investigate the effects of parameters in the proposed approach on accurately determining instantaneous modal parameters. Numerical analyses also demonstrate that the proposed approach is superior to some published techniques (i.e., recursive technique with a forgetting factor, traditional basis function expansion approach, and weighted basis function expansion approach) in accurately estimating instantaneous modal parameters of a structure. Finally, the proposed approach is applied to process measured data for a frame specimen subjected to a series of base excitations in shaking table tests. The specimen was damaged during testing. The identified instantaneous modal parameters are consistent with observed physical phenomena.     

基于IDL的地形三维可视化系统的研制

利用IDL语言强大的数据处理与图形显示功能,应用组件编程技术并结合数字摄影测量原理,对立体航空影像对进行数字影像处理,并通过内插计算快速生成数字高程模型。在此基础上运用可视化技术实现三维可视化显示及简单的可视化分析,从而完成了地形三维可视化系统的研制。     

Response Surface with random factors for seismic fragility of reinforced concrete frames

Seismic fragility curves for reinforced concrete (RC) frame structures are evaluated considering the uncertainties in both structural parameters and seismic excitation. Response Surface (RS) models with random block effects are used to solve the problem in an approximate way with good computational efficiency. The RS models are calibrated through numerical data obtained by non-linear incremental dynamic analyses performed using different sets of ground-motions, strength distributions in frame elements, and values of the random variables adopted to describe the uncertainties in the structural behaviour. The present work is mainly focused on the problem of obtaining a reasonable compromise between result soundness and computational effort. With reference to a three storey frame structure, a series of numerical tests is presented. Different simulation plans, defined following the theory of Design of Experiments (DOE), and simplified polynomial RS models are employed. The fragility curves obtained by different methods are compared, using the results from full Monte Carlo simulation as the reference solution.     

A temporal hybrid dynamic integration algorithm strategy for inelastic time history analysis of high‐rise reinforced concrete structures under strong earthquakes

A complete earthquake time history analysis (THA) requires a stable, accurate, and efficient dynamic integration algorithm. It is not rare to encounter numerical divergence when some implicit algorithms are used to deal with severe materially or geometrically nonlinearities. For explicit algorithms, computational efficiency is always a major concern. A temporal hybrid dynamic algorithm (THDA) strategy, which is specialized in the inelastic THAs of high‐rise reinforced concrete (RC) structures experiencing severe plasticity development, is developed herein. A preliminary evaluation is carried out on three low‐rise structural models, that is, two frame structures and one wall‐frame structure, for each group of collected implicit algorithms and explicit algorithms. From the evaluation, four alternatives are generated for the subsequent detailed assessment. A general framework for the THDA is proposed and implemented on a finite element analytical platform. The four alternatives are assessed based on their performance on a high‐rise frame core‐tube RC structure. The assessment indicates that the proposed THDA strategy can give rise to a more compatible dynamic integration algorithm for the complete THAs of high‐rise building structures when they are experiencing severe damage. The concerns about the computational stability, accuracy, and efficiency of the dynamic algorithms can be well balanced by the THDA.     

非饱和土地区高速铁路路基沉降预测模型

准确、合理地预测线路工后沉降是高速铁路建设的关键,现场沉降观测数据表明不同饱和度地区路基沉降曲线线型变化较大,基于饱和理论的沉降预测方法在工后沉降预测中存在不能准确描述沉降规律,且存在预测值偏小的风险。基于实测沉降规律,提出了一个适用于非饱和土地区路基的沉降预测曲线模型。分析了预测曲线模型的特点,并基于最小二乘法给出模型参数的求解方法。结合兰新铁路第二双线LXS-15标段沉降数据,提出相关系数、偏差度、稳定度为模型有效性检验指标,结合施工完成2 a的实测资料,进行了在施工完成3个月及6个月所提模型与规范要求3种预测模型的对比研究;对3条不同饱和程度高铁路基沉降预测结果表明所提出的非饱和土预测模型具有较好的精度和广泛的适用性,为非饱和土地区高速铁路建设合理判断工后沉降提供参考。     

混合多重二次插值在三维地层可视化中的应用

地质曲面插值重构是三维地质建模的一个研究热点。针对稀疏的地质钻孔数据,提出了一种基于多重二次曲面和反距离加权的组合插值方法——混合多重二次曲面插值方法(MMQS)。为了检验MMQS的精度,以peaks曲面作为先验曲面模拟起伏的地质界面、采用均方根误差(RMSE)和平均绝对百分比误差(MAPE)作为曲面拟合效果的检验标准,验证了MMQS方法比常规的多重二次曲面插值方法有较好的插值精度。MMQS算法易于编程。把MMQS方法运用到地质界面重构中,在VB.net与IDL平台上开发了三维地层可视化系统3D GeoVis。采用3D GeoVis对某工程场区进行了三维地层插值和可视化,显示了3D GeoVis的有效性和便易性。     

海量车载激光点云组织与可视化研究

车载移动测量系统是一种高精度、高速度的空间信息采集设备,由于获取的点云数据量大,海量车载激光点云的数据处理、三维建模和可视化面临挑战。考虑到车载激光点云沿采集线路逐行扫描形成的特点,提出了一种分块多层叠加型空间索引结构,对海量车载激光点云数据自动分块并建立LOD瓦片结构,实现海量车载激光点云数据的管理与动态调度。实验结果表明:该方法具有有效性和可行性。     

Vibration based stiffness reconstruction of beams and frames by observing their rotations under harmonic excitations — Numerical analysis

Recent progress in data acquisition technology makes it possible to measure not only translational but also angular vibrations of beam and frame structures. This raises a question whether these new methods can effectively be applied in damage structural detection and localization. For this purpose a damage detection method aiming at reconstructing the stiffness distributions of a structure from its vibration measurements is tested when rotational degrees of freedom are added to the dynamic model of the structure. The stiffness reconstruction is formulated as a minimization problem in terms of harmonic vibrations of the structure and its finite element model. Two examples of a beam and frame structure are analyzed in detail. To better test the damage detection algorithm, measuring noise with various levels has been added to the analyzed signal. The results of the numerical analyses show that the application of genetic algorithms and a Levenberg–Marquadt local search appeared to be even more effective in damage detection when the angular amplitudes of harmonic vibrations are acquired. This creates good prospects for the future applications of angular accelerometers in structural health monitoring of civil engineering structures.     

Buckling restrained braces as structural fuses for the seismic retrofit of reinforced concrete bridge bents

A structural fuse concept is proposed in which easily replaceable ductile structural steel elements are added to an RC bridge bent to increase its strength and stiffness, and also designed to sustain the seismic demand and dissipate all the seismic energy through hysteretic behavior of the fuses, while keeping the RC bridge piers elastic. While this concept could be implemented in both new and existing bridges, the focus here is on the retrofit of non-ductile reinforced concrete bridge bents. Several types of structural fuses can be used and implemented in bridges; the focus in this paper is on using Buckling Restrained Braces (BRB) for the retrofit of RC bridge bents. The results of a parametric formulation conducted introducing key parameters for the design procedure of the fuse system, validated by nonlinear time history analyses are presented. A proposed design procedure, using BRBs as metallic structural fuses, is found to be sufficiently reliable to design structural fuse systems with satisfactory seismic performance. A graphical representation to help find admissible solutions is used, and shows that the region of admissible solution decreases when the frame strength ratio increases as a larger fuse element is required to achieve an effective structural fuse concept.     

Application of singular spectrum analysis to structural monitoring and damage diagnosis of bridges

Singular spectrum analysis (SSA) is a novel technique and has proven to be a powerful tool for time series data analysis. Through singular value decomposition of Hankel matrix data, the time series of data can be decomposed into several simple, independent and identifiable components from singular values and singular vectors. It has already been widely applied to process climatic, meteorological, geophysical and economic data. In this paper, we demonstrate that the coupling degree of the 1st and 2nd singular values in SSA contains useful indications on the feature and composition of the analysed signal. The proposed method is successfully applied to the monitoring of structure, such as damage detection of the simulated dynamic system, experimental steel frame, bridge foundation scouring and pier settlement in the laboratory and on-site bridge monitoring during typhoon strike. The proposed algorithm is simple and suitable for structural health monitoring in the field.     

基于GIS和体视化技术的工程场地地震液化势3D可视化

工程场地地震液化势三维模型的建立及可视化研究的目的是用三维图形来描述地震动作用下场地液化势的空间分布特性,以此为城市防震减灾工作提供相应的支持。采用具有概率意义的饱和砂土抗液化强度经验公式来对场地进行地震液化势概率评价;采用一种基于"块"模型的数据结构来描述场地液化势三维实体;结合Kriging插值法和体视化技术进行场地液化势的三维可视化建模。研究表明:采用"块"数据模型来分割模拟三维液化势场,利用Kriging法对工程场地地震液化势进行空间数据三维插值,有助于揭示勘探孔以外任意空间点的土层液化势信息;基于液化势概率评价结果和体视化技术,采用Kriging插值法,以不同的色标体现场地液化势的风险程度,可以直观的三维图像形式呈现场地液化势的空间分布特性和变化趋势,通过剖切自动生成指定位置的二维剖面和三维切割体,工程场地液化势的三维分布特性得到有效的表达。     

Concurrent multi-scale modelling and updating of long-span bridges using a multi-objective optimisation technique

This paper aims at developing an innovative technique of concurrent multi-objective optimisation for updating the multi-scale model of long-span bridges. A multi-scale model is established for the purpose of concurrently analysing the global response of the structure and nonlinear local damages in order to assess structural state and local damage evolution or deteriorating, respectively. A multi-objective optimisation technique is proposed in this work for concurrent multi-scale model updating, in which several key issues including the determination of the objective functions and constraint conditions, the multi-objective optimisation algorithm and how to find the optimal solution from many non-inferior solutions are studied. The proposed concurrent multi-objective optimisation technique is applied to update the initial multi-scale model of Runyang Suspension Bridge (RYSB) near Shanghai, and the updated model is validated by the data from the field tests conducted for obtaining the response in global (dynamic properties) and local levels.