Prediction of Load-Displacement Curve of Flexible Pipe Carcass Under Radial Compression Based on Residual Neural Network

The carcass layer of flexible pipe comprises a large-angle spiral structure with a complex interlocked stainless steel cross-section profile, which is mainly used to resist radial load. With the complex structure of the carcass layer, an equivalent simplified model is used to study the mechanical properties of the carcass layer. However, the current equivalent carcass model only considers the elastic deformation, and this simplification leads to huge errors in the calculation results. In this study, radial compression experiments were carried out to make the carcasses to undergo plastic deformation. Subsequently, a residual neural network based on the experimental data was established to predict the load-displacement curves of carcasses with different inner diameter in plastic states under radial compression.The established neural network model’s high precision was verified by experimental data, and the influence of the number of input variables on the accuracy of the neural network was discussed. The conclusion shows that the residual neural network model established based on the experimental data of the small-diameter carcass layer can predict the load-displacement curve of the large-diameter carcass layer in the plastic stage. With the decrease of input data, the prediction accuracy of residual network model in plasticity stage will decrease.

Parameter Identification Based on Force-Displacement Curves for a Bolted Joint Finite Element Model

In order to identify the uncertain parameters of a bolted joint finite element model,a simple and applicable way of parameter identification is introduced.By utilizing numerical simulation with the Abaqus software and experimental investigation with the MTS material testing system,the tangential force-displacement curves that reflect the characteristics of the bolted joint were acquired.On the basis of this,by employing the response surface methodology（RSM）and genetic algorithms（GAs）,parameters in the FEM model were identified.The force-displacement curves by both virtual and experimental approaches are well correlated at the end.This phenomenon-based parameter identification method may help facilitate precise prediction of complex jointed connection structures.

Method for determining the position of landslide slip-surface with a typical inclinometric curves

In the actual monitoring of deep hole displacement,the identification of slip surfaces is primarily based on abrupt changes observed in the inclinometric curve.In conventional identification methods,inclinometric curves exhibiting indications of sliding can be categorized into three types:B-type,D-type,and r-type.The position of the slip surface is typically determined by identifying the depth corresponding to the point of maximum displacement mutation.However,this method is sensitive to the interval of measurement points and the observation scale of the coordinate axes and suffers from unclear sliding surfaces and uncertain values.Based on the variation characteristics of these diagonal curves,we classified the landslide into three components:the sliding body,the sliding interval,and the immobile body.Moreover,three different generalization models were established to analyze the relationships between the curve form and the slip surface location based on different physical indicators such as displacement rate,relative displacement,and acceleration.The results show that the displacement rate curves of an r-type slope exhibit a clustering feature in the sliding interval,and by solving for the depth of discrete points within the step phase,it is possible to determine the location of the slip surface.On the other hand,D-type slopes have inflection points in the relative displacement curve located at the slip surface.The acceleration curves of B-type slopes exhibit clustering characteristics during the sliding interval,while the scattered acceleration data demonstrate wandering characteristics.Consequently,the slip surface location can be revealed by solving the depth corresponding to the maximum acceleration with cubic spline interpolation.The approach proposed in this paper was applied to the monitoring data of a landslide in Yunnan Province,China.The results indicate that our approach can accurately identify the slip surface location and enable computability of its position,thereby enhancing applicability and reliability of the deep-hole displacement monitoring data.

Powell dynamic identification of displacement parameters of indeterminate thin-walled curve box based on FCSE theory

The FCSE controlling equation of pinned thinwalled curve box was derived and the indeterminate problem of continuous thin-walled curve box with diaphragm was solved based on flexibility theory. With Bayesian statistical theory,dynamic Bayesian error function of displacement parameters of indeterminate curve box was founded. The corresponding formulas of dynamic Bayesian expectation and variance were deduced. Combined with one-dimensional Fibonacci automatic search scheme of optimal step size,the Powell optimization theory was utilized to research the stochastic identification of displacement parameters of indeterminate thin-walled curve box. Then the identification steps were presented in detail and the corresponding calculation procedure was compiled. Through some classic examples,it is obtained that stochastic performances of systematic parameters and systematic responses are simultaneously deliberated in dynamic Bayesian error function. The one-dimensional optimization problem of the optimal step size is solved by adopting Fibonacci search method. And the Powell identification of displacement parameters of indeterminate thin-walled curve box has satisfied numerical stability and convergence,which demonstrates that the presented method and the compiled procedure are correct and reliable.During parameters鈥？iterative processes,the Powell theory is irrelevant with the calculation of finite curve strip element（FCSE） partial differentiation,which proves high computation effciency of the studied method.

Dynamic Bayesian estimation of displacement parameters of continuous curve box based on Novozhilov theory

The finite strip controlling equation of pinned curve box was deduced on basis of Novozhilov theory and with flexibility method, and the problem of continuous curve box was resolved. Dynamic Bayesian error function of displacement parameters of continuous curve box was found. The corresponding formulas of dynamic Bayesian expectation and variance were derived. After the method of solving the automatic search of step length was put forward, the optimization estimation computing formulas were also obtained by adapting conjugate gradient method. Then the steps of dynamic Bayesian estimation were given in detail. Through analysis of a Classic example, the criterion of judging the precision of the known information is gained as well as some other important conclusions about dynamic Bayesian stochastic estimation of displacement parameters of continuous curve box.

ASSESSMENT OF LOCAL INFLUENCE IN A GROWTH CURVE MODEL WITH RAO'S SIMPLE COVARIANCE STRUCTURE

The present paper deals with the problem of assessing the local influence in a growth curve model with Rao's simple covariance structure. Based on the likelihood displacement,the curvature measure is employed to evaluate the effects of some minor perturbations on the statistical inference, thus leading to the large curvature direction, which is the most critical diagnostic statistic in the context of the local influence analysis. As an application, the common covariance-weighted perturbation scheme is thoroughly considered.

Classification Study on Relative Permeability Curves

The classification method of relative permeability curves is rarely reported, when relative permeability curves are applied;if the multiple relative permeability curves are normalized directly, but not classified, the calculated result maybe cause a large error. For example, the relationship curve between oil displacement efficiency and water cut, which derived from the relative permeability curve in LD oilfield is uncertain in the shape of low water cut stage. If being directly normalized, the result of the interpretation of the water flooded zone is very high. In this study, two problems were solved: 1) The mathematical equation of the relationship between oil displacement efficiency and water cut was deduced, and repaired the lost data of oil displacement efficiency and water cut curve, which solve the problem of uncertain curve shape. After analysis, the reason why the curve is not available is that relative permeability curves are not classified and optimized;2) Two kinds of classification and evaluation methods of relative permeability curve were put forward, the direct evaluation method and the analogy method;it can get the typical relative permeability curve by identifying abnormal curve.

BUCKLING OF SPATIAL CURVED RODS WITH CIRCULAR CROSS-SECTIONS

Formulae for determining Green strain of an initially curved and twisted rod with circular cross-sections are derived by using the natural (curvilinear) coordinate system. Finite element analyses are performed for the flexural buckling of initially curved and twisted thin rods under simultaneous action of axial force and torque. Numerical examples demonstrate that the given formulae are correcte. Some numerical results are compared with existing analytical solutions and data obtained by commercial FE software. The convergence of the proposed curved element is better than that of elements in the commercial FE software. It is shown that good accuracy and convergency are achieved by solving three-dimensional problems.

多级耗能后张预应力筋预制节段墩的抗震性能分析

为提升节段墩的抗震性能,采用多级耗能方法实现多节段共同参与耗能.将耗能钢筋从节段墩底部向上依次穿过多个接缝,从而实现多级耗能.通过数值模拟,研究多级耗能节段墩体系的耗能能力,并针对三级耗能节段墩体系的轴压比和耗能钢筋配筋率进行参数分析.结果表明,多级耗能节段墩体系可以提高节段墩的耗能能力,而每一级别耗能体系存在耗能上限,且随多级耗能体系级别的提升而增加.在不同级别耗能体系中,耗能钢筋配筋率存在不同的临界值,一级耗能体系的耗能钢筋配筋率临界值为0.23%,二级耗能体系为1.31%.为获得较强的耗能能力,建议将耗能钢筋配筋率取值为1.31%,轴压比取值为0.1.

基于绝对位移法的曲线梁桥多维多点弹塑性随机响应分析

针对当前地震动空间效应下曲线梁桥地震反应分析多采用确定性激励输入且忽略桥梁非线性的情况,采用了多维多点非平稳随机激励对曲线连续梁桥进行弹塑性响应分析。建立非线性有限元模型并降维解耦非平稳地震动非平稳演化功率谱(energy power spectral density,EPSD)矩阵,采用绝对位移法对桥梁进行非线性时程分析。考虑不同视波速、场地条件、相干性以及平稳与非平稳地震激励,综合分析了曲线连续梁桥的随机响应及其频域特性和时域特性。结果表明,地震动空间效应和地震动的非平稳性对曲线梁桥随机响应影响很大,其中地震动空间效应对桥梁随机响应大小及其频域分布有显著影响,而非平稳性会对随机响应大小及其时变响应趋势产生重要影响。因此,在曲线连续梁桥抗震分析中需充分考虑地震动空间效应和地震动非平稳性,以避免错误估计桥梁抗震性能。提供了全面的分析结果,对加强曲线连续梁桥的抗震设计和评估,从而提高其抗震性能和可靠性具有重要意义。

面料拉伸性能与运动文胸防震功能的定量关系

为探究面料拉伸性能与运动文胸防震功能之间的定量关系,选取6种不同针织面料,先分别测量不同面料拉伸率为30%时的弹性模量来表征其拉伸性能,然后将这6种面料作为罩杯部分用料制作文胸,其它部位为同种面料。以运动假人为实验对象,在其表面选取7个位置粘贴标记点,采用三维人体动作捕捉系统,采集实验对象在模拟10 km/h跑步过程中各标记点的坐标变化,并计算出各点在局部坐标系下的相对位移。以运动过程中运动文胸对乳房竖直位移的减小作用来表征其防震功能,通过曲线拟合与模型筛选得出面料拉伸性能与文胸防震功能的定量关系。结果表明:6款罩杯面料动态最大拉伸率均值为30%,说明实验中用拉伸率为30%时的弹性模量表征面料的拉伸性能较为合理。罩杯面料弹性模量与乳房竖直位移间存在显著负相关,即面料弹性模量越大,乳房竖直位移越小,表明文胸防震功能越好;幂函数模型可作为以罩杯面料弹性模量预测75C实验对象10 km/h跑步运动时乳房竖直位移的首选模型。未来可通过测量罩杯与乳房之间的静动态压力及乳房-罩杯整体刚度探究罩杯面料拉伸性能对文胸防震功能的影响机制。

基于现行规范的型钢混凝土柱侧力-位移曲线预测方法研究

型钢混凝土(steel reinforced concrete,SRC)柱因承载力高、刚度大和耐久性能好等优点而被广泛应用于高层结构中。然而,现阶段SRC结构设计普遍基于承载力设计法,基于性能的抗震设计法在SRC结构方面的应用仍待完善。作为基于性能(位移)的抗震设计方法中最重要的一环,现阶段SRC构件的侧力-位移关系评估缺乏规范指导。基于美国现行规范ASCE/SEI 41-17中针对钢筋混凝土构件的相关规定,结合SRC构件的受力与变形特征,提出了发生弯曲破坏的SRC柱在地震作用下的侧力-位移曲线建模方法。该曲线采用约束混凝土强度计算SRC构件的峰值承载力;使用刚度折减法考虑型钢与混凝土之间的黏结滑移;基于SRC构件的变形特征考虑了纵向受力钢材端部滑移对柱顶侧移的贡献。最后,通过与28根SRC柱试验结果的比较证明了曲线的适用性。计算结果表明:所提出的曲线能合理预测发生弯曲破坏的SRC柱的开裂荷载、开裂位移、峰值荷载、峰值位移和强度退化,可为SRC结构的性能化抗震设计提供参考。

非圆行星齿轮马达设计与排量分析

非圆行星齿轮马达具有容积效率高、密封性良好、传递扭矩大等优势,可应用于井下机械和食品机械等领域。根据几何关系推导圆弧-圆弧型(双圆弧型)节曲线参数所需满足的弧长条件、传动条件与约束条件,建立并求解内齿圈与太阳轮节曲线非线性规划模型。在分析非圆行星齿轮马达进排液规律的基础上,确定不同太阳轮旋转角度下各容腔进排液的周期变化规律。通过面积拟合法与图解法求解马达最大与最小容腔面积,确定马达理论排量。非圆行星齿轮马达试验测试结果表明,试验法与理论计算法确定的马达实际流量随转速变化的趋势基本一致,最大误差仅为9.57%,验证了双圆弧型节曲线马达理论排量模型的正确性,可为进一步探索非圆行星齿轮马达优化设计提供参考。

材料参数对液弹阻尼器动态特性的影响

为了探究材料性能参数对液弹阻尼器动态特性的影响规律,采用电液伺服动态试验机研究了液弹阻尼器的载荷-位移曲线、弹性刚度、阻尼刚度和损耗因子随橡胶硬度和阻尼液黏度的变化。试验结果表明:液弹阻尼器91.5%以上的弹性刚度由橡胶部分提供,并且弹性刚度随橡胶硬度的增大而增大;液弹阻尼器84.8%以上的阻尼刚度由阻尼液提供,并且阻尼刚度和损耗因子随阻尼液黏度的增大而增大,随剪切振幅的增大而减小,阻尼液黏度越大阻尼刚度和损耗因子下降幅度越大;当阻尼液黏度由2000 mm^(2)/s增大到10000 mm^(2)/s时,液弹阻尼器的阻尼刚度由2420 N/mm增大到5163 N/mm;当剪切振幅由0.2 mm增大到1.5 mm时,阻尼刚度分别减小18.5%和40.1%。以上结论可为液弹阻尼器的选材提供依据。

拉压段长度变化对复合锚杆锚固性能影响研究

抗浮是深基坑施工所面临的重要工程问题之一,目前多使用抗浮锚杆平衡地下水对构筑物产生的浮力。但拉力锚杆具有局部应力集中、临界锚固深度浅等问题。因此研究设计了一种新型拉压分散型复合锚杆。通过现场试验,分析复合锚杆拉压段长度变化与锚杆锚固性能相关关系,并与拉力锚杆进行对比。结果表明:复合锚杆可以有效防止锚杆第一界面发生剪切破坏;随着承拉段与承压段长度比值降低(比值分别为5、2、1),锚杆极限承载力逐渐提高,分别为传统拉力型锚杆的1.17倍、1.22倍和1.44倍,且荷载位移曲线陡降性逐渐消失,结构延性更好;一定范围内增加承压段长度,可以更有效地调用锚固段下部土层强度,锚杆临界锚固深度下移,侧摩阻力发挥程度更高。

含聚合物防水膜的隧道衬砌界面剪切-滑移力学特性试验研究

为研究隧道衬砌结构中密贴型防水层界面的力学特性,根据隧道喷膜防水衬砌结构的特点,采用粘结强度试验和压剪试验探讨聚合物防水膜复合试件的界面剪切-滑移力学行为和特性。通过粘结强度试验绘制3种类型防水膜的拉伸应力-位移曲线,通过压剪试验绘制界面剪切应力-位移曲线,基于试验结果曲线计算得到防水层的界面参数,包括剪切强度、残余剪切强度、剪切模量、剪切滑移能量和剪切失效位移,并讨论防水材料性能和法向压应力对这些参数的影响。结果表明,防水层界面的剪切-滑移特性主要受防水材料特性和法向压应力的影响,防水材料特性对界面剪切强度和剪切模量的影响较大,而残余剪切强度、剪切滑移能量和剪切失效位移则受到法向压应力的影响更多。

工业灰渣-棉秆纤维灌孔砌块砌体的抗剪性能研究

为研究工业灰渣-棉秆纤维灌孔砌块砌体的抗剪性能,对48个工业灰渣-棉秆纤维灌孔砌块砌体和6个未灌孔工业灰渣-棉秆纤维空心砌体进行了抗剪试验,探究了砌筑砂浆抗压强度、芯柱抗压强度和预压力对灌孔砌块砌体破坏特征、峰值位移和抗剪强度的影响,分析了灌孔砌块砌体的剪切变形性能。结果表明:提高砂浆抗压强度、芯柱抗压强度和预压力均能不同程度地提升灌孔砌块砌体的抗剪强度和峰值位移,其中芯柱抗压强度和预压力对砌体抗剪强度和峰值位移影响较大;与砂浆部分相比,随着芯柱抗压强度的提升,芯柱部分对砌体抗剪强度的贡献越来越大。基于梁式抗剪模型,提出了适用于无预压状态下工业灰渣-棉秆纤维灌孔砌块砌体的抗剪强度计算公式;根据试验结果拟合了预压状态下砌体的抗剪强度计算公式。

基于深度学习的复合材料开孔板拉伸失效行为预测

为研究复合材料开孔板在拉伸载荷下的失效行为,基于开孔板的拉伸试验建立了高精度的有限元仿真模型,并批量生成了拉伸载荷-位移曲线的数据集。提出了一种双长短时记忆(Long short-term memory,LSTM)神经网络模型用于预测载荷-位移曲线,其中第1个LSTM模型进行输入特征的提取,第2个LSTM模型直接给出载荷-位移曲线的预测。结果表明:这一模型能够高效、准确地预测开孔板的拉伸载荷-位移曲线,在测试集上的决定系数R2可以达到0.9755,关键特征如初始刚度E0的预测误差仅为1.85%,极限载荷Fmax的预测误差仅为2.16%。

高速铁路大跨度钢桁架桥接触网腕臂安装技术研究

高速铁路大跨度钢桁架桥纵向伸缩量大且变位复杂,是影响接触网腕臂偏移等系统能否正常、安全运行的重要因素,如何解决接触网腕臂安装、偏移调整与钢梁伸缩之间的协同配合,目前国内在此方面鲜有研究。通过阐述受导线伸缩影响的腕臂偏移机理和大跨度钢桁架桥梁体纵向伸缩机理,分析在不同接触网锚段布置方式下大跨度钢桁架桥梁体伸缩对腕臂偏移的影响,并采用逐工点分析法总结不同工况下钢梁伸缩与导线伸缩对腕臂偏移影响的相互关系,揭示了接触网腕臂安装曲线在导线伸缩及钢梁伸缩共同作用下的计算方法。结合典型案例计算分析,建议采用不同钢梁跨度下的推荐锚段布置方式能有效降低腕臂偏移量,并提出应重点关注伸缩缝两侧锚段腕臂偏移问题、腕臂偏移为叠加关系时缩小半锚长度、钢梁跨度大于720 m时应重点计算伸缩缝两侧双腕臂间距等优化事项。研究内容及计算公式可为系统性解决高速铁路大跨度钢桁架桥接触网腕臂偏移设计、施工及运营维护等技术难题提供理论支持。