Load on Bicycle Frame During Cycling with Different Speeds and Gestures

Experiment and dynamic simulation were combined to obtain the loads on bicycle frame. A dynamic model of body-bicycle system was built in ADAMS. Then the body gestures under different riding conditions were captured by a motion analysis system. Dynamic simulation was carried out after the data of body motions were input into the simulation system in ADAMS and a series of loads that the body applied on head tube, seat pillar and bottom bracket were obtained. The results show that the loads on frame and their distribution are apparently different under various riding conditions. Finally, finite element analysis was done in ANSYS, which showed that the stress and its distribution on frame were apparently different when the frame was loaded according to the bicycle testing standard and simulation respectively. An efficient way to obtain load on bicycle frame accurately was proposed, which is significant for the safety of cycling and will also be the basis for the bicycle design of digitalization, lightening and customization.

Theoretical research and experimental validation of quasi-static load spectra on bogie frame structures of high-speed trains

One of the major problems in structural fatigue life analysis is establishing structural load spectra under actual operating conditions.This study conducts theoretical research and experimental validation of quasi-static load spectra on bogie frame structures of high-speed trains.The quasistatic load series that corresponds to quasi-static deformation modes are identified according to the structural form and bearing conditions of high-speed train bogie frames.Moreover,a force-measuring frame is designed and manufactured based on the quasi-static load series.The load decoupling model of the quasi-static load series is then established via calibration tests.Quasi-static load–time histories,together with online tests and decoupling analysis,are obtained for the intermediate range of the Beijing—Shanghai dedicated passenger line.The damage consistency calibration of the quasi-static discrete load spectra is performed according to a damage consistency criterion and a genetic algorithm.The calibrated damage that corresponds with the quasi-static discrete load spectra satisfies the safety requirements of bogie frames.

Numerical Simulation of Dynamic Response and Collapse for Steel Frame Structures Subjected to Blast Load

The progressive collapse of steel frame structures under the blast load was investigated using LS-DYNA. The multi-material Eulerian and Lagrangian coupling algorithm was adopted. A flu-id-structure coupling finite element model was established which consists of Lagrange element for simulating steel frame structures and concrete ground, multiple ALE element for simulating air and TNT explosive material. Numerical simulations of the blast pressure wave propagation, struc-tural dynamic responses and deformation, and progressive collapse of a five-story steel frame structure in the event of an explosion near above ground were performed. The numerical analysis showed that the Lagrangian and Eulerian coupling algorithm gave good simulations of the shock wave propagation in the mediums and blast load effects on the structure. The columns subjected to blast load may collapse by shear yielding rather than by flexural deformation. The columns and joints of steel beam to column in the front steel frame structure generated enormous plastic defor-mation subjected to intensive blast waves, and columns lost carrying capacity, subsequently lead-ing to the collapse of the whole structure. The approach coupling influence between struc-tural deformation and fluid load well simulated the progressive collapse process of structures, and provided an effective tool for analyzing the collapse mechanism of the steel frame structure under blast load.

Experimental study on full scale light frame wood house under repeated lateral load

In order to obtain a deeper understanding of the behavior of the structure under high wind load,this paper conducted an experimental study on a full-scale L-shaped single story light frame wood house under the uniform lateral load simulated using a gasbag.The investigation involved the performance of light frame wood structure after it experienced the repeated cyclic lateral wind load as well as the performance of the structure under the ultimate lateral load.Then,the study verified that light frame wood structure can resist repeated cyclic wind loads without observable degradation in stiffness during the anticipated serve life,and recommended shear wall percent drift restriction for lateral wind load design of wood structure in serviceability limit states is 1/400 drift,and in ultimate limit states is 1/80 drift.The conclusions of this paper can be benefit for the engineering practice of the light frame wood structures in high wind load regions.

Theoretical Research and Experimental Validation of Elastic Dynamic Load Spectra on Bogie Frame of High-speed Train

When a train runs at high speeds, the external exciting frequencies approach the natural frequencies of bogie critical components, thereby inducing strong elastic vibrations. The present international reliability test evaluation standard and design criteria of bogie frames are all based on the quasi-static deformation hypothesis. Structural fatigue damage generated by structural elastic vibrations has not yet been included. In this paper, theoretical research and experimental validation are done on elastic dynamic load spectra on bogie frame of high-speed train. The construction of the load series that correspond to elastic dynamic deformation modes is studied. The simplified form of the load series is obtained. A theory of simplified dynamic load–time histories is then deduced. Measured data from the Beijing–Shanghai Dedicated Passenger Line are introduced to derive the simplified dynamic load–time histories. The simplified dynamic discrete load spectra of bogie frame are established. Based on the damage consistency criterion and a genetic algorithm, damage consistency calibration of the simplified dynamic load spectra is finally performed. The computed result proves that the simplified load series is reasonable. The calibrated damage that corresponds to the elastic dynamic discrete load spectra can cover the actual damage at the operating conditions. The calibrated damage satisfies the safety requirement of damage consistency criterion for bogie frame. This research is helpful for investigating the standardized load spectra of bogie frame of high-speed train.

基于应变测试矿用汽车车架结构优化设计分析

矿用铰接车采用液压举升机构实现货物卸载,受力情况复杂,对车架结构影响大且要求高。针对某自卸车后车架和货箱在不同运行条件下的承载特性进行分析,获取各工况的载荷情况和边界条件;根据前述分析,建立后车架和货箱的有限元分析模型,选取多个典型工况开展分析,获取应力应变的分布情况;采用材料升级、圆角优化及焊接工艺提升等,针对应力集中和较大位置进行优化设计,降低应力值,保证安全裕度满足要求;采用直角应变测试法,针对实际自卸车车架开展应力测试,在分析的关键位置布置应变片,选取典型工况开展测试,并与仿真结果开展对比。结果可知:自卸车铰接点和液压举升缸鹅颈支撑处应力较大,并且出现了应力集中,但均在许可范围之内;采用厚度提升、直径增大及焊接工艺提升等方法,有效提升应力分布,最大值明显降低;实车测试和仿真分析,满载工况应力分布基本一致,最大值误差低于5.8%;优化后结果明显低于优化前;结果表明分析模型和优化方法的可靠性,为此类分析设计提供参考。

In-Plane Shear Performance of Wood-Framed Drywall Sheathing Wall Systems under Cyclic Racking Loading

A pilot study was conducted at Penn State University to determine whether the type of drywall joint compound would influence the shear strength of wood-frame stud walls sheathed with Gypsum Wall Board (GWB or drywall). In this study, five 2438 mm by 2438 mm specimens were tested under in-plane cyclic racking loading following the CUREE loading protocol for light-frame wall systems. Three specimens were finished using non-cement based joint compound while the other two used cement based joint compound. Based on the experimental testing of the specimens, the results show that the use of cement based joint compound on drywall joints produces higher shear capacity for the wall system as compared to similar specimens finished with conventional non-cement based joint compound. The result of the study is particularly important for high seismic regions where interior stud walls in residential construction effectively take part in seismic resistance even though wood shear walls are normally used on exterior walls.

Progressive Collapse of RC Frames Due to Heavy Impact Loads of Tsunami

Progressive collapse is a relatively rare event, as it requires both an abnormal loading to initiate the local damage and a structure that lacks adequate continuity, ductility and redundancy to resist the spread of damage. However, significant casualties can result when collapse occurs. Heavy impact loads due to tsunami against building can be one of the scenarios of progressive collapse during tsunami disaster. Since progressive collapse includes material and geometry nonlinearity during collapse propagation, in the present research capability of 2 models for the material nonlinearity in simulating actual behavior of structures during collapse is compared with recent experimental results of a Reinforced Concrete (RC) frame. The results demonstrate that a material nonlinearity model, that is based on the idealized component load-deformation behavior, is not a proper representation for the real behavior of structures during progressive collapse and is so conservative.

起波配筋混凝土框架结构的抗内爆性能数值模拟

人工塑性铰在框架结构抗震研究中已经得到广泛应用,其能够控制梁塑性铰出现的位置,避免框架结构在地震中出现梁柱节点破坏而发生连续倒塌,实现“强柱弱梁”的设计目标。一种新型起波钢筋构造的人工塑性铰为结构抗爆设计提供了新的思路。现有的结构静载试验表明,起波钢筋兼具优异的变形性能和较强的极限承载力。采用简化混合建模的方法,基于有限元分析软件ANSYS/LS-DYNA,对采用不同起波配筋方案的钢筋混凝土框架结构进行数值模拟。研究结果表明:在爆炸荷载作用下,起波配筋梁能有效地吸收冲击力,降低支座反力,推迟反力峰值出现时间,保护梁柱节点,将破坏限制在梁板构件,从而防止结构发生连续倒塌。

基于SolidWorks和Ansys的铁路卷状货物横向限位运输座架设计

目的针对卷状货物在铁路运输途中常发生横向窜动,造成货物损伤、危及行车安全等问题,基于当前主流运输座架和技术经验,设计一款安全可靠、适用多种车型、可叠放回送、可循环使用、适合多种规格卷状货物、带有横向限位装置的运输座架。方法根据《铁路货物装载加固规则》,制定最不利工况下的卷状货物装载加固方案;依据《钢结构设计标准》及敞车、平车的结构,确定运输座架的结构和材料;通过SolidWorks-Ansys对运输座架进行建模和有限元分析,得到卷钢座架变形及应力的变化情况。结果通过分析可知,运输座架会受到垂向力、纵向力,其最薄弱部分的应力分别为355.14、341.99 MPa,位移变形量分别为0.55、1.069 mm,符合规定;在最不利工况下,横向限位挡件的最大应力为28.89 MPa,最大变形量为0.04 mm,符合规定。结论设计的铁路横向限位运输座架安全可靠,可有效防止货物发生横向窜动;叠装回送,可实现重去重回。该设计填补了现有运输座架对卷状货物无法进行横向刚性加固的空白,对当下卷状货物运输发展具有较大的促进作用。

不同载荷工况下缩比高温超导悬浮架的振动实验研究

通过建立缩比高温超导悬浮架实物模型,针对乘客频繁上下车导致载重变化实际现象,模拟车辆空载、满载和超载的三种工况,实验研究不同工况下悬浮架固有频率的变化规律和振动响应特性。实验结果表明,高温超导悬浮架的横垂向固有频率均随载重增加而减小,但数值变化较小,可有效避免了因载重变化导致横垂向固有频率改变引发共振;相比空载,高温超导悬浮架满载时的动态性能更优,因此具有良好的空重载荷性能。

爆炸冲击波作用下板架结构响应研究综述

板架结构是飞机和水面舰艇主要的组成单元,研究其在爆炸冲击波作用下的变形和破坏对目标结构的防护设计具有重要意义。国内外学者对板架结构在冲击波载荷作用下的变形与破坏进行了大量研究,形成了诸多成果。本文中从理论分析、实验研究和数值模拟3个方面总结了爆炸冲击波载荷作用下板架结构响应领域的研究现状,并对未来研究方向提出一些建议,为相关结构的抗爆设计以及战时毁伤评估提供参考。

果园作业平台车架耐久性研究

针对农用机械作业工况复杂、受多种外力、对结构件寿命影响较大等问题,以果园作业平台车架为研究对象,编制车架加速载荷谱,分析车架耐久性。采用有限元分析方法,对车架进行力学分析并选取关键载荷测点,建立果园作业平台多体动力学模型采集相应测点载荷谱,利用伪损伤保留编辑法获取不同伪损伤保留量的加速载荷谱,从压缩时间效率、伪损伤域、功率谱密度、穿级/雨流计数和统计值参数等方面对比,分析伪损伤保留量对加速载荷谱质量的影响。通过车架耐久性仿真对比不同编辑方案对耐久性分析精度和效率的影响。对比结果表明,伪损伤保留量不低于90%才能保证加速载荷谱的质量。仿真结果表明,车架最小寿命历程大约为65000 km,根据果园作业平台使用条件和用户使用情况调查,了解果园作业平台每年大约行驶8100 km,使用年限为8年,该车架满足要求。且伪损伤保留量为95%时为最佳编制方案,加速载荷谱时间压缩量为55%,车架耐久性仿真分析误差能控制在5%内且仿真效率提高391%,本文为提高农用机械部件耐久性载荷的编辑质量提供参考。

双向加载下钢筋混凝土框架柱震损分级及损伤模型对比分析

目前已有的RC框架柱震损划分原则及对应损伤指标计算方法主要基于水平单向受力下的研究成果。相比单向受力,相同加载位移下水平双向受力RC框架柱的抗震性能明显退化,损伤加剧,因此RC框架柱的震损分级量化需考虑双向地震作用。本文基于已开展的RC柱双向滞回试验,提出了双向受力下RC柱基于骨架曲线的震损分级原则;基于8个典型双向损伤模型,对7个双向受力RC试验柱不同损伤级别对应的损伤指数进行了对比分析,推荐了适用于双向地震作用下RC柱震损分级判定的2个损伤模型以及对应的震损分级指数区间建议值,并对2个模型的特点和适用性进行了讨论。之后采用该损伤模型和震损分级评价指标对典型双向受力柱的抗震性能影响因素进行了分析。结果显示,损伤评价结果与试验结果和试验现象吻合较好,该方法可较好地适用于双向滞回加载RC柱的损伤评估。

顶层抽柱钢筋混凝土框架抗震性能比较分析

由于所涉及的荷载和房屋层数最少、对原框架的影响最小,因此顶层抽柱在混凝土框架结构抽柱改造工程中较常见。针对目前多数工程技术人员关注如何使抽柱后结构承受增加的荷载,而对于抽柱后框架整体抗震性能关注和研究不多的现状,文中以某一顶层抽柱教学楼为例,采用ABAQUS有限元软件建立符合现行规范要求的单榀未抽柱的原框架模型、顶层抽柱后形成的增大原梁截面框架模型和预应力梁框架模型,对三框架模型进行模拟低周反复加载试验,得到三框架模型的滞回曲线、骨架曲线、刚度退化曲线及等效粘滞阻尼系数等抗震性能指标变化规律。对三框架模型的抗震性能进行比较分析。结果表明:与未抽柱的原框架相比,增大原梁截面框架和预应力梁框架水平承载力降低,延性也稍降低。原框架初始刚度最大,加载后期三框架刚度退化速率相近,但原框架刚度稍大。在耗能方面,预应力梁框架后期等效粘滞阻尼系数最大,表明抽柱后预应力梁框架耗能能力优越。框架顶层抽柱后结构的抗震性能总体降低,增大原梁截面框架和预应力梁框架的抗震性能表现各有优劣,但预应力梁框架整体表现相对更优。

Winkler地基上边坡锚固框架设计计算的简明有限差分法

为克服现有Winkler地基上边坡锚固框架设计计算的有限差分法需假设框架在锚杆处截断的问题,通过建立受集中荷载作用的Winkler地基梁的挠曲微分方程,提出无需做截断处理的简明有限差分法。基于提出的差分方法,改进锚杆拉力在框架纵横梁上的分配与调整方法,并采用Matlab开发功能完善的程序。结果表明:有限差分数值解具有较高的计算精度,框架外伸段直接计算结果会出现负的土抗力,致使计算结果偏于不安全,可通过调整该段边界条件的方法予以消除,使最终计算结果更加可靠。本研究开发的差分程序对锚固框架整体设计提供了一种高效的计算方法。

基于Adams/ncode整车车架疲劳寿命分析

车架作为货车的主要承载部件,承担来自货厢与货物的载荷,同时将该载荷通过悬挂系统传递到车桥和地面,不平的地面又通过轮胎和悬挂系统将载荷反馈到车架上,导致车架受力情况非常复杂,车架的破坏形式不仅有静强度破坏,还存在疲劳破坏。通过Adams建立整车动力学模型完成悬架与车架应力点的选取,建立路面工况,输出整车载荷谱。在寿命分析软件ncode中,结合有限元软件Ansys,对整车车架进行三工况下的静力分析,在ncode导入整车载荷谱的rsp格式,输出满载工况下车架疲劳寿命云图。

中原文旅城欢乐世界一期雪世界高区结构设计

中原文旅城欢乐世界一期雪世界高区结构体系采用巨型钢框架,存在结构扭转不规则、楼板缺失、大悬挑、竖向构件间断及钢桁架平台为重载大跨钢结构等不规则情况和设计难点。设计中采用基于性能的抗震设计方法,根据构件的重要程度采用不同的性能目标。4个巨型框架柱为支撑框架结构,其支撑采用屈曲约束支撑,使结构在大震作用下形成良好的屈服机制和耗能能力。对结构进行小震反应谱法弹性分析、弹性时程分析、中震弹性分析以及大震弹塑性分析。结果表明,结构整体和构件的抗震性能均能达到设计的预期目标;巨型钢框架结构体系较好地适应了本工程的实际情况,可供类似项目在选择结构体系时参考。

适用于超大采高工作面的新型复合框架式高承载中部槽研究

随着工作面采高的不断增大,液压支架与采煤机随之不断增大,在7 m及以上大采高工作面,液压支架油缸推力增大到1 600 kN以上,采煤机自重增大到1 800 kN以上,对刮板输送机中部槽的承载能力和可靠性提出了挑战,传统中部槽已难以适应,容易出现槽体及封底板变形、焊道开裂、铲板断裂失效等故障,严重影响工作效率。为此提出了一种新型复合框架式高承载中部槽,通过框架式盒状结构、鼓形销定位联接结构,有效提升中部槽的承载能力和可靠性,满足在7 m及以上大采高工作面使用需求。

装配式人字撑复合墙板异形柱框架抗震性能研究

提出一种新型装配式人字撑复合墙板异形柱框架结构。为研究其抗震性能,对一榀1/2缩尺异形柱框架结构进行低周反复荷载试验,分析其破坏形态、滞回曲线、承载力、耗能能力、位移延性、刚度退化等指标,并通过ABAQUS有限元软件模拟后将模拟结果与试验结果进行了对比分析。研究结果表明:装配式人字撑复合墙板异形柱框架结构呈现“泡沫混凝土-人字撑-叠合框架梁-组合异形框架柱”分级破坏顺序;复合墙板以剪切破坏为主;人字撑在水平往复位移荷载作用下,可与异形柱框架结构形成双重抗震体系,提高结构的抗震能力;有限元模拟结果与试验结果吻合良好,该有限元模拟方法适用于装配式人字撑复合墙板异形柱框架结构。