Bayesian kriging regression for the accuracy improvement of beam modeled T-junctions of buses and coaches structures with a methodology based on FEM behavioral analysis

This paper has been developed in the framework of the alternative beam T-junction solution previously propoused by the authors (Alcalá et al., 2013), with the scope of optimizing the behavior of buses and coaches upper structures modeled with beam type elements. The alternative beam T-junction model proposed by the authors, had a total of six elastic elements at the junction level allowing to modify the localized rigidity of any modeled T-junctions, therefore improving their behavior and avoiding the well known rigidity issue these elements have. A fundamental aspect behind the use of these alternative beam models is related to the necessity of correctly estimating the rigidity values of the elastic elements for each modeled T-junction. In this context, we propose applying a surrogate model for the reference calculations which is based on statistical Bayesian kriging predictors. Statistical predictions have the added value, with respect to deterministic solutions, of providing a quantification of uncertainty. The development of the kriging predictors has required the application of a statistical methodology including computer experiment design, computation of moments of inertia, graphical and ANOVA type sensitivity analysis and Monte Carlo computation of Bayesian inference. The results of the application have been a very satisfactory trade-off between accuracy of approximation (prediction) and computational cost. The surrogate kriging models also provide an useful tool for a better understanding of the input-output relationships involved in the reference computations.     

汽车偏置前撞试验用渐变强度可变形壁障的有限元模型

建立了渐变强度可变形壁障(PDB)的有限元模型。PDB的两个铝蜂窝芯采用壳单元并用"等同化"方法使之与实际的蜂窝结构一致,铝蜂窝窝孔中的空气采用阻尼杆单元表示。对PDB偏置板和横梁的碰撞实验过程进行了仿真,结果表明测力墙受力和壁障碰撞后变形与实验结果高度吻合,验证了模型的正确性。     

薄壁高墩连续刚构桥的线性稳定分析

结合龙潭河大桥的工程实例,利用有限元程序ANSYS,分别选用梁单元和壳单元建立有限元模型,对施工和成桥阶段进行线性稳定分析。结论表明：采用梁单元模型对薄壁高墩刚构桥进行稳定分析能得到满意的效果,两种单元模型对比分析得出了一些对该桥初步设计具有参考意义的结论。     

Mining of the association rules between driver electrodermal activity and speed variation in different road intersections

It is commonly acknowledged that the human factor and the interaction between the human factor and the road environment are among the most common causes of road accidents. Physiological signals can provide a real-time assessment of the driver's state because they can be collected continuously without interfering with the driver's task performance or the drivers' perception of the road. This study presents a method for measuring and quantifying drivers' physiological responses when approaching T-junctions and roundabouts using electrodermal activity and speed variations. Speed and electrodermal activity were collected continuously during a driving study which took place on a test environment based at Cranfield University and surrounding roads. Twenty participants were involved in the study. The analysis focused on four crossing manoeuvres on two T-junctions and a roundabout. The association Rule with the Apriori algorithm was used in order to evaluate associations between the variables related to electrodermal activity, i.e. the number and amplitude of the SCR peaks (assessed by the Electrodermal Impact Index in aggregate form), and the variables related to speed, i.e. the speed variation and its sign (positive or negative), for each type of intersection. The main results of this study can be summarized as follows: 1) the rules obtained for the manoeuvres on the T-Junctions show that the T-junctions induce low variations in the electrodermal activity and are often associated with a significant speed increase (between 20% and 30%); 2) the rules obtained for the manoeuvres on the roundabout highlights that the roundabout induces high variations in the electrodermal activity and is associated with a significant speed reduction (between 20% and 40%).     

基于多智能主体系统的车道变换模型

为更加真实地反映车道变换行为,建立具有良好性能的车道变换模型,根据抽样调查结果分析了车道变换的基本条件。引入智能主体(Agent)理论,将Agent与车道变换行为联系起来,建立了基于多智能主体系统(Multi-Agent System,MAS)的车道变换模型框架;给出了车辆MAS的结构,抽象了各Agent成员的元组构成,给出了各Agent成员的工作原理与执行流程;基于多智能系统工程方法(Multi-Agent Systems Engineering Methodology,MASEM),给出了车道变换的仿真流程并得到仿真实例。研究结果表明:在2 km长的双向4车道高速公路上,在30 s时间内,利用提出的车道变换模型仿真得到的车道变换车辆次数与实际情况相差8%;在该时段内任意瞬间,正在执行车道变换的车辆数目与实际情况相差仅1.67%。     

Dynamic analysis of a pantograph-catenary system using absolute nodal coordinates

The dynamic interaction between the catenary and the pantographs of high-speed trains is a very important factor that affects the stable electric power supply. In order to design a reliable current collection system, a multibody simulation model can provide an efficient and economical method to analyze the dynamic behavior of the catenary and pantograph. In this article, a dynamic analysis method for a pantograph-catenary system for a high-speed train is presented, employing absolute nodal coordinates and rigid body reference coordinates. The highly flexible catenary is modeled using a nonlinear continuous beam element, which is based on an absolute nodal coordinate formulation. The pantograph is modeled as a rigid multibody system. The analysis results are compared with experimental data obtained from a running high-speed train. In addition, using a derived system equation of motion, the calculation method for the dynamic stress in the catenary conductor is presented. This study may have significance in providing an example that a structural and multibody dynamics model can be unified into one numerical system.     

混凝土桥水泥铺装层温度应力研究

针对典型T梁和箱形梁桥,在简支和多跨连续边界条件、承受正温度梯度、负温度梯度、温度和汽车耦合作用下,用有限元法分析水泥铺装层的受力特征和铺装层拉应力、层内最大剪应力、等效应力和接触层间法向拉拔力、层间剪应力,以及各应力对铺装厚度的敏感性.以箱形梁桥为对象,比较分析了连续水泥铺装和划缝、带裂缝工作状态下受力以及配钢筋的影响.提出了设计、施工建议.     

某重型自卸车车架结构强度有限元分析

利用有限单元法对一款冲压铆接自卸车车架进行了仿真分析,计算得到该车架在典型极限工况下的变形和应力,结果表明该车架强度合理,满足设计要求。     

京珠高速公路温泉隧道的施工监测及位移反分析

介绍京珠高速公路温泉隧道的原位量测与监控系统,先对隧道围岩收敛、拱顶下沉及其内部位移等实测数据进行分析,并根据隧道围岩收敛情况,利用位移反分析程序BMP90,进行反分析得到等效弹性模量以及侧压力系数等地层参数,对隧道围岩的稳定性进行了评价。利用反分析得到的弹性模量等地层参数进行了二维弹性有限元分析,并与实测结果进行了简单的对比分析。分析结果表明等效弹性模量应取终测时刻反分析值或较小的反分析值比较接近实际,反分析侧压力系数通常可取全程回归分析值;利用反分析得到的地层参数对隧道开挖进行二维弹性有限元分析结果与实测值相符合。     

组合截面桥梁结构计算方法研究

组合截面桥梁结构包括分层浇注混凝土结构桥梁以及钢混凝土组合结构桥梁等。近年来这类桥梁结构的工程应用越来越多,而这类桥梁结构的分析计算是一个比较复杂的工程计算问题。本文采用刚臂节点位移协调方法,用多个梁单元来模拟组合截面,建立组合截面桥梁结构施工全过程分析方法,并给出对比分析算例。     

钢筋混凝土拱桥参数化建模及特征值屈曲分析

针对某在建的150m跨径钢筋混凝土拱桥,利用开发的基于ANSYS的拱桥参数化建模模块,分别采用梁单元和实体单元创建有限元模型。在此基础上进行拱桥的特征值屈曲分析,并对拱轴线类型、桥面结构形式以及拱脚支承形式等影响因素进行了参数分析。分析结果表明:采用梁单元与实体单元进行结构离散,对于拱桥的特征值屈曲的计算结果影响不大。     

基于响应面法的钢管混凝土组合桁梁桥多尺度有限元模型修正

为建立适用于钢管混凝土桥梁的高效、高精度有限元分析模型,提出一种基于响应面法的全桥多尺度有限元模型修正方法。首先以一座钢管混凝土组合桁梁桥为工程背景建立包含全桥、组合桁梁桥面板以及钢管混凝土桁架杆件3个尺度的ABAQUS全桥多尺度有限元模型。在考虑钢管混凝土结构的特点和施工误差的基础上选取桥面板混凝土弹模、厚度,桁架弦杆内混凝土弹模,钢材弹模以及加载车辆荷载5个影响因素作为待修正参数;根据实桥试验条件选择中跨跨中挠度、下弦空管弦杆应力、墩顶钢管混凝土弦杆应力、墩顶受压腹杆应力以及桥面板顺桥向应力5个目标函数。其次采用中心复合设计方法生成了待修正参数的样本集,并将每组参数样本代入有限元模型进行计算。进而采用响应面法建立待修正结构参数和目标函数的2次多项式函数关系,结合参数显著性分析得到响应面方程。最后结合实桥试验结果对多尺度有限元模型3个尺度上的结构参数进行同步修正。结果表明：修正后的参数变化情况与依托工程的实际施工情况相符;采用修正后的参数建立的多尺度有限元模型计算值与实桥试验结果吻合良好;修正后的有限元模型具有较高的精度,可真实反映实际工程中桥梁结构的受力状态。该修正方法可为桥梁结构运营期间的健康监测、状态评估、损伤检测提供可靠的分析手段。     

Evaluation of the coupled dynamical response of a pantograph—catenary system: contact force and stresses

In this article, the static stresses in a catenary and its vibration modes are calculated by establishing the FEM model of the catenary with Euler-Bernoulli beam elements. The mode shapes of the catenary obtained are considered as the generalized variables which are used in the establishment of the motion equations of the catenary system. The physical model of the pantograph is simplified as a multi-body system with mass, stiffness, damping, and friction. On the basis of having derived the coupled motion equations of the pantograph-catenary system, its dynamic behavior is analyzed in detail and the contact force is calculated. Using the contact force as the external moving load of the FEM model of the catenary, the dynamic stress in the catenary is simulated. Through the detailed analysis and calculation, we not only obtain the dynamic stress response at any element of the catenary, but also its frequency responses. As the dynamic stress in the assistant wire is quite large, the influence of its structure on dynamic stress is analyzed and the way to reduce the dynamic stress is suggested. At last, the calculation method of dynamic stress is validated by a test.     

双曲拱桥有限元分析中建模方法研究

结合南京长江大桥引桥中双曲拱桥的承载能力检算,提出按刚度等效原则把拱肋与拱波简化为梁格体系的计算模型,采用空间梁单元模拟拱肋与拱波,缩减了双曲拱桥全桥建模和结果分析时的计算工作量。对此计算模型,采用ANSYS软件,选取了桥梁荷载中的几种典型工况做模拟计算,与ANSYS有限元软件建立的另一精细模型的计算结果及相同加载方式下的现场试验实测数值进行了对比,并对三组数据结果做了简要的分析。     

Combined experimental and modeling methodology for intake line evaluation in turbocharged diesel engines

This paper presents a methodology for diesel engine intake line analysis that combines specific element tests and modeling. The purpose of this methodology is to determine the impact of intake lines, or newly designed intake elements, on the volumetric efficiency of internal combustion engines while avoiding expensive on-engine tests. For this research, the intake system is divided into several elements which are individually characterized using flow and impulse test rigs. Next, individual systems are modeled using a one-dimensional code. Finally, these component models are coordinated to provide an evaluation of the volumetric efficiency. Intake lines coming from two turbocharged diesel engines are used to illustrate the method. The model is validated by comparing the model results with the actual system performance evaluated in engine test cells. Discussions of the feasibility of the technique and on the impact of element model inaccuracies on the overall system model are provided.     

基于有限元方法的复合钢混凝土桥梁热点应力分析研究

通过建立复合钢混凝土疲劳危险部位焊接构件的三维有限元模型,围绕桥梁交通荷载作用下局部热点应力和疲劳损伤累积进行分析,获得合适的在役钢-混凝土桥梁关键焊接构件的疲劳损伤评价方法。研究结果表明:采用大桥有限元模型进行动力特性分析,模型计算固有频率和实测值最大误差在10%以内,计算的动力特性和设计测试阶段特性相符;钢混凝土桥梁纵向加劲桁架细节热点应力区域出现在上下弦杆与对角撑、盖板连接处,与焊缝构件最大疲劳损伤位置一致,主梁框架热应力出现在靠近公路外侧梁腹板连接处;通过线性米勒准则获得的疲劳损伤累积呈线性变化,在高周疲劳损伤初期损伤率增长较慢,后期较快,适用于在役结构疲劳寿命评价。     

无限长板带对位荷载下的有效分布宽度计算和应力分析方法

无限长板带对位荷载下的应力分布的研究有助于进一步理解和解决长条形板式结构（如带外伸横梁的桥梁结构等）的横向计算简化问题。其等效加载模式（平面应力问题）也对应于条形基础下的下卧刚性层的软土地基受力问题（平面应变问题）。通过理论分析采用复变函数法得到无限长板带对位荷载下的应力计算公式，然后导出该理论解的有效宽度简化计算方法，与理论解的误差控制在5%以内，为进一步工程应用做理论准备。     

Methodology for bus structure torsion stiffness and natural vibration frequency prediction based on a dimensional analysis approach

Engineering bus design requires testing of bus structures prototypes in order to guarantee a certain level of strength and an appropriate static and dynamic behavior of the bus superstructure when exposed to road loads. However, experimental testing of real bus structures is very expensive as it requires expensive resources and space. If testing is done on a scale bus model the previous required expenses are considerably reduced. Therefore, a novel methodology based on dimensional analysis applied to bus structure prediction to evaluate the bus structure static and dynamic performance is proposed. The static performance is evaluated attending to torsion stiffness and the dynamic in terms of the natural vibration frequencies and rollover threshold. A scale bus has been manufactured and dimensionless parameters have been defined in order to project the results obtained in the scale bus model to a larger model. Validation of the proposed methodology has been carried out under experimental and finite element analysis.     

概念设计阶段的车身结构分析

在某款轿车的概念设计阶段,建立了概念车身结构的几何模型,采集了若干典型的车身梁截面.根据接头的力学特性,利用弹簧单元和刚性梁单元对接头进行了模拟,计算了车身5种典型接头的刚度.求取了概念模型的弯曲刚度、扭转刚度和模态,并与详细设计结果进行对比.结果表明,概念设计计算结果与详细设计的结果基本相近,说明采用所提出的概念设计方法,能够比较准确地预测车身结构的性能.     

钢-轻骨料混凝土简支组合梁承载及变形能力研究

为了确定轻骨料混凝土组合梁的性能,以对称集中荷载为加载方式,同时考虑栓钉间距、钢梁尺寸等影响组合梁承载及变形能力的因素,研究了钢-轻骨料混凝土组合梁结构的承载及变形能力。根据剪切滑移的挠曲线方程,提出组合梁在集中荷载作用下跨中挠度的简化计算公式,并选用ANSYS软件进行了有限元对比模拟分析,计算结果吻合良好。算例表明,轻骨料混凝土组合梁相比于相同尺寸的普通混凝土组合梁,应力值偏小5%左右,跨中挠度偏大10%左右,钢-轻骨料混凝土组合梁承载力及变形能力可满足实际应用,同时验证了计算公式应用的可行性。