地震液化灾害自适应步长计算方法及控制参数研究

饱和砂土液化是岩土地震工程和土动力学研究领域的重要课题。在动力液化数值计算中,计算精度和计算效率一直是衡量数值方法的重要指标。在水土二相耦合弹塑性计算的数值平台上开发了自适应步长方法,通过位移误差、孔压误差和混合误差的评估体系建立了时间步长自动调整的策略及相关控制参数。通过控制参数的影响性分析,确定了主要控制参数为误差允许值和孔压误差比例系数,辅助控制参数为初始时间步长、步长调整的下限和上限。对处于液化场地的地铁车站模型进行了动力自适应步长数值计算,获得了上浮位移和超孔压比的发展过程,预测出液化上浮的灾害。同时也对比了固定步长法和自适应步长法的精度和效率,发现采用自适应步长法可极大的节约计算成本并不失计算精度。     

地震作用下悬臂类结构的模态截断方法

为估计模态叠加法中模态截断对结构地震作用下位移、速度、加速度反应的影响，对比分析了累积振型参与质量误差、静荷载参与比误差、质量相关荷载作用下的位移误差、累积振型贡献系数误差、累积振型加速度贡献系数误差和单位阵误差等模态截断指标随模态数目增加的变化规律。以一个5层剪切框架、一个单向不对称的4层框架和一个框架支撑结构的地震反应为例，讨论了结构位移、速度和加速度反应的模态截断误差与模态截断指标的关系。算例分析结果表明，静荷载参与比误差高估了低阶模态的影响而使模态截断数目偏少；质量相关荷载作用下的位移误差所得模态数目不稳定，这两个指标不适合作为模态截断的依据。对于悬臂类结构，模态截断所产生的累积误差以加速度的最大，速度的次之，位移的最小；对于位移反应，首层平动位移的累积振型贡献系数误差和累积振型参与质量误差可作为位移反应模态截断的依据；高阶模态对结构加速度反应的贡献大于对位移反应的贡献，应采用累积振型加速度贡献系数误差作为加速度反应模态截断的依据。     

近断层地震地面运动的能量与位移延性需求

针对脉冲型近断层地震动考虑了位移延性和阻尼因素对结构输入能量谱的影响,指出输入能量谱是表征地震动累积破坏能力的稳定指标,分析了地震动输入能量和单自由度结构响应最大位移之间关系,提出了等效速度比的简化解析表达式．基于Park-Ang双参数损伤模型分析了损失指标和最大位移延性之间的关系,并和文献[12]建议公式进行了比较,指出对于确定的损伤指标,近场地震动相对集中的能量输入会导致更高的位移变形需求,和相对较小的累积损伤需求。因而有必要考虑增强结构瞬时耗能能力以减小其变形。     

箱型吊臂端部挠度计算方法研究

研究轮式起重机箱型伸缩式吊臂端部挠度计算的几种典型方法,包括传统的解析法如惯性矩转换法、叠加法、当量惯性矩法,在解析法基础上考虑附加弯矩的解析大位移法,以及有限元小位移法和有限元大位移法。解析法相对有限元法来说计算简便、计算速度快,但是几种解析法公式的计算误差目前没有一个详细的说明。有限元大位移法由于考虑了附加弯矩的影响,更贴近实际值,但是其建模、加载及分析过程比较复杂,所需时间比较长,并不适合所有情况下使用。本文以有限元大位移法计算结果作为标准,对解析法进行评价,分析其计算结果相对有限元大位移法的计算误差。     

关于塔机塔身垂直度误差的确定和测量

本文论述了塔身垂直度误差标准的制定根据,以及测量方法,并通过试验数据分析了塔身垂直度对塔身变形的影响。给出了考虑塔身垂直度时塔顶水平位移的计算方法。文中确定的塔身垂直度允许误差及其测量方法已列入即将颁布的国标《塔式起重机技术条件》。     

地铁基坑水平位移监测精度分析

本文利用已有的地铁基坑水平位移监测数据，结合具体的监测方法极坐标法，探讨地铁基坑水平位移监测的观测点坐标中误差和水平角测回数的选择。     

汽车最小转弯直径测量计算模型的修正分析

针对目前汽车最小转弯直径测量方法和计算模型的不足,为提高测量精度,将测量时车身侧倾引起的误差考虑在内,提出侧倾位移误差的概念并对侧倾位移误差进行推导。对计算汽车最小转弯直径的数学模型进行修正,并通过MATLAB实验仿真的方法对修正模型进行验证。结果显示,修正后的计算模型明显减小了侧倾位移误差的影响,改善了汽车最小转弯直径测量的精度。     

桥梁隔震支座静力性能试验分析

桥梁隔震支座在使用过程中可能受到各种水平静载作用.本文介绍了一个桥梁隔震支座的水平静力试验.在试验中,考虑了不同水平位移加载步长、持荷时间、不同的初始位移变化对支座动、静力性能的影响.说明桥梁隔震支座静力性能与动力性能存在不同,随着作用时间增加,存在明显的卸载现象;水平初位移的存在对支座滞回耗能曲线没有明显的影响.     

基于斜率模态的统一化损伤识别指标研究

提出了一种基于规则结构第一阶频率斜率模态的梁式结构损伤定位与程度识别方法.分析比较了第一阶位移模态及其斜率模态对于结构系统参数的敏感性.结合有限元模型,形成一系列以斜率模态为基础得到的统一化损伤识别指标(UDI),以该指标表现出的损伤状态在不同损伤工况下对于任意楼层损伤程度都具有稳定性,这样就避免了大型损伤特征矩阵的计算.使用UDI指标对一剪切型梁在单损伤与几种多损伤工况下进行了损伤识别与定位,并且分析实际结构与数值模型系统参数存在误差的情况下的识别效果.还考虑了减少测点布置后的损伤识别效果,且对识别误差的原因进行了分析.研究结果表明:基于第一频率斜率模态的UDI指标在具有近似数值模型的条件下,能够确定损伤位置并且可以较精确地估计损伤程度,而且识别速度快.     

数字化曲线的最佳拟合

本文针对数字化地图的曲线拟合精度进行了研究 ,提出了评定拟合质量的标准和计算方法。主要内容包括综合考虑拟合的模型误差和偶然误差的联合影响 ,论证了拟合方程优选的标准 ,给出了选模的实用方法 ,导出了模型误差的区间估计式以及拟合结果的不确定度公式 ,最后进行了实例验证。     

Identification and correction of water velocity measurement errors associated with ultrasonic Doppler flow monitoring

Ultrasonic Doppler flow monitoring (UDFM) is used to measure water flow in pipes and channels. However, a lack of scattering particles and signal noise can cause velocity errors, particularly for smaller discharges and surface water ('clean') flows. A postprocessing methodology is presented that identifies and corrects these errors, maximising the value of existing data. Test criteria are used to identify errors. The error correction procedure defines depth–velocity relationships from cleaned 'training data' representing the range of flow conditions (including backed up) and uses these relationships to replace erroneous velocities automatically. UDFM velocity errors have been successfully identified and corrected in example applications. Routine use allows early identification of changes in instrument or site behaviour. The methodology is practical, consistent and updateable. This is a significant advancement over previous methods for correcting velocity errors, improving the applicability of UDFM.     

Online energy-based error indicator for the assessment of numerical and experimental errors in a hybrid simulation

Hybrid simulation is an effective structural test technique combining the numerical simulation of substructures with predictable behavior, and experimental testing of complex components that are difficult to model. Consequently, hybrid simulation is prone to both numerical and experimental errors. In this paper, the dominant sources of numerical and experimental errors that can contaminate the results of a hybrid simulation are examined. It is shown that linearized analytical stability and accuracy limits for algorithms and test procedures used in a hybrid simulation may fail to adequately predict the results due to errors and nonlinearities of actual tests. An alternative approach based on monitoring the energy balance of the structural system is proposed to capture the effects of both experimental and numerical errors. This method extends an existing experimental error indicator to also account for (a) errors resulting from modification of experimental measurements by iterative corrections in numerical integrators or other signal correction procedures, and (b) numerical errors in the integration algorithm including equilibrium errors and kinematic relations between displacement, velocity and acceleration. The effectiveness of the proposed energy error indicator in predicting severity of errors is demonstrated through numerical and experimental simulations using various integration procedures.     

相对运动法与绝对位移直接求解法算法误差分析

多点激励地震响应分析过程中,相对运动法和绝对位移直接求解法分别假定阻尼与内部节点相对速度、绝对速度成比例,由于阻尼假定的不一致,计算结果可能存在误差.采用随机振动分析方法对瑞利阻尼模型下2种求解方法计算结果之间的误差进行了理论分析,得出了2种算法下结构动态响应功率谱密度误差主要受激励频率与结构基频的比值、结构阻尼比影响...     

Health assessment of beams–experimental verification

A novel nondestructive structural health assessment procedure now under development at the University of Arizona and presented in a companion paper, is experimentally verified. The experimental verifications of the procedure to identify defect-free and defective fixed ended and simply supported beams are presented in this paper. In this approach, acceleration and rotational time histories are measured at pre-selected node points. They are then post-processed to remove several sources of error including noise, high frequency content, slope, and DC bias. The post-processed response information is then successively integrated to obtain the corresponding velocity and displacement time histories. Even when these sources of error were removed from the response information, the proposed method failed to identify the beams. Several factors including noise, data latency, scale factor and cross coupling error were investigated. Amplitude and phase errors in the accelerometer's measurements were found to be the root cause. Alternative approaches are proposed to mitigate them. Following the suggested procedures, defect-free and defective fixed ended and simply supported beams are correctly identified. The proposed NDE procedure is accurate and robust, and can identify defects at the local element level in the context of the finite element representation. The laboratory experiments clearly and conclusively verified the proposed algorithm, i.e. a beam can be identified without using input excitation information and using only noise-contaminated response information and established its application potential.     

大跨径外倾式拱桥钢箱拱肋拼装误差影响

分析了大跨径拱桥空间钢箱拱肋的施工特点。利用几何方法推导了空间钢箱拱肋节段拼装误差在拱肋最大悬臂端的累积规律：对首座大跨径曲线梁非对称外倾式拱桥——南宁大桥拱肋拼装进行了算例分析,分析了节段拼装线位移误差和角位移误差对最终拼装精度的不同影响,说明了拼装过程中对角位移误差进行精确控制的必要性。本文方法具有一般性,对类似工程有借鉴意义。     

隧道贯通误差及其预计方法研究

推导出了最佳贯通点和横向贯通误差的预计公式,并在此基础上给出了任意点的贯通误差预计公式及贯通误差曲线。通过贯通误差曲线,可方便、直观地得到横向贯通误差。     

The influence of calculation error of hourly marine meteorological parameter on building energy consumption calculation

The ocean is a crucial area for future economic development. The marine environment has high energy-efficient and ecological requirements for building construction. Meteorological parameters are the key basis for the analysis and design of building energy efficiency. The lack of meteorological parameters for energy efficiency, particularly hourly data, under oceanic climatic conditions is a universal problem. The appropriate calculation methods of hourly meteorological parameters under oceanic climatic conditions are explored in this study. The impact of the calculation errors of the hourly meteorological parameters on building energy consumption is also analyzed. Three key meteorological parameters are selected: temperature, humidity, and wind speed. Five hourly calculations methods, including linear interpolation, cubic spline interpolation, pieceated three-Hermite interpolation, Akima interpolation, and radial basis function interpolation, are selected to calculate the error of the difference method, with Xiamen, Haikou, and Sanya as the locations of meteorological research. Appropriate interpolation methods are selected for the three parameters, and the seasonal and regional characteristics of the errors of each parameter are compared. Different interpolation methods should be selected for different meteorological parameters in different seasons. The error data of the three parameters of different magnitudes are constructed. A quantitative relationship between the sum of squares due to error of the three meteorological parameters and the rate of change of cooling energy consumption is established. The hourly calculation errors of meteorological parameters have an important impact on the calculation of dynamic energy consumption. The energy consumption differences caused by the errors of different parameters are significant. Obvious regional and seasonal differences also exist. This research strengthens the research foundation of building energy consumption calculation under oceanic climate conditions.     

旋转补偿器在中压蒸汽管道的应用

结合某中压蒸汽供热工程,探讨了方形补偿器、球型补偿器、旋转补偿器的适用性。针对该工程具体情况,分析了旋转补偿器的布置及设计要点。     

基于状态微分控制算法的空间结构主动振动控制分析

对于主动振动控制器的设计,传统的控制算法以速度和位移作为系统的输入量,但速度和位移难以观测,给实际应用带来了较大的误差.本文在振动状态空间方程的基础上,对其进行矩阵运算,形成以加速度为系统输入的状态微分反馈控制方程.构造具有约束条件的目标函数,根据Lagrange乘子法和泛函极值运算确定了状态反馈矩阵和状态反馈估计值,从而构造了闭环的状态微分控制算法.根据此算法对一直径为1m的环形空间结构进行了振动控制仿真,利用时域内的模态参数识别方法,对控制效果进行了评价,并以三层剪切型框架结构为对象,对状态微分控制算法和传统的LQR算法进行了控制效果的对比分析.结果表明,利用状态微分控制算法在空间结构上的振动控制是可行的,且减振效果明显,同时优于传统的LQR控制算法.