Evaluation of the fishbone model in simulating the seismic response of multistory reinforced concrete moment-resisting frames

The fishbone model is a simplified numerical model for moment-resisting frames that is capable of modelling the effects of column-beam strength and stiffness ratios. The applicability of the fishbone model in simulating the seismic responses of reinforced concrete moment-resisting frames of different sets of column-beam strength and stiffness ratios are evaluated through nonlinear static, dynamic and incremental dynamic analysis on six prototype buildings of 4-, 8-and 12-stories. The results show that the fishbone model is practically accurate enough for reinforced concrete frames, although the assumption of equal joint rotation does not hold in all cases. In addition to the ground motion characteristics and the number of stories in the structures, the accuracy of the model also varies with the column-beam stiffness and strength ratios. The model performs better for strong column-weak beam frames, in which the lateral drift patterns are better controlled by the continuous stiffness provided by the strong columns. When the inelastic deformation is large, the accuracy of the model may be subjected to large record-to-record variability. This is especially the case for frames of weak columns.

Nonlinear damage model for seismic damage assessment of reinforced concrete frame members and structures

A nonlinear damage model based on the combination of deformation and hysteretic energy and its validation with experiments are presented.Also,a combination parameter is defined to consider the mutual effect of deformation and hysteretic energy for different types of components in different loading stages.Four reinforced concrete (RC) columns are simulated and analyzed using the nonlinear damage model.The results indicate that the damage evolution evaluated by the model agrees well with the experimental phenomenon.Furthermore,the seismic damage evolution of a six-story RC frame was analyzed,revealing four typical failure modes according to the interstory drift distribution of the structure;the damage values calculated using the nonlinear damage model agree well with the four typical failure modes.

Application of time series modeling to a national reference frame realization

This paper presents an option for modern dynamic terrestrial reference system realization in Uzbekistan for user needs. An additive model is explored to predict patterns of time series and investigate means of constructing forecast time series models in the future. The main components(trend, periodical, and irregular) of the KIUB(DORIS) and KIT3, TASH, MADK, and MTAL(GNSS) international stations coordinate time series were investigated. It was shown that seasonal nonlinear trends occurred both in the height(U) component of all stations and the east(E) component of high mountainous stations such as MTAL and MADK. The seasonal periodical portion of the time series determined from the additive model has a complicated pattern for all sites and can be explained as both hydrological signals in the region and improvement of observational quality. Amplitudes of the best-fitting sinusoids in the North component ranged between 1.73 and 8.76 mm; the East component ranged between 0.82 and 11.92 mm; and the Up component ranged between 3.11 and 40.81 mm. Regression analysis of the irregular portion of the height component of the two techniques at the Kitab station using tropospheric parameters(pressure and temperature) was confirmed as only 57% of the stochastic portion of the time series.

PHYSICAL MODELLING OF ISOTHERMAL DIE FORGING PROCESS OF Ti-ALLOY STRUCTURAL AIR-FRAME PART WITH ETYPE CROSS-SECTION AND VARYING THICKNESS RIB

Isothermal flashless die forging process of Ti - alloy structural air - frame part with varying thickness rib has been modelled in this paper.The results of present study show that a upside - down trapezoid rib would be formed and buckling would occure as blank is reduced,if the thickness of billet is maller than or equal to the thickness of rib. During modelling process of structural air frame part with E type cross - section rib, the saddle or lap would be formed finally at the middle of transverse rib between ribs with increase in deformation.If metal is allowed to flow out at confluence of longitudinal and transverse rib, the lop defect would be eliminated,, but a pipe cavity is obvious on corresponding loca- tion of blank. of defect formation depends on distance of metal flow ,friction,temperature homoge- neity of the blank and complexity of the part.

Extended intrinsic mean spin tensor for turbulence modelling in non-inertial frame of reference

We investigate the role of extended intrinsic mean spin tensor introduced in this work for turbulence modelling in a non-inertial frame of reference. It is described by the Euclidean group of transformations and, in particular, its significance and importance in the approach of the algebraic Reynolds stress modelling, such as in a nonlinear K-ε model. To this end and for illustration of the effect of extended intrinsic spin tensor on turbulence modelling, we examine several recently developed nonlinear K-ε models and compare their performance in predicting the homogeneous turbulent shear flow in a rotating frame of reference with LES data. Our results and analysis indicate that, only if the deficiencies of these models and the like be well understood and properly corrected, may in the near future, more sophisticated nonlinear K-ε models be developed to better predict complex turbulent flows in a non-inertial frame of reference.

Bilateral shear strength of rectangular frame column based on simplified space truss-arch model

To investigate the bilateral shear strength of rectangular frame column subjected to oblique horizontal load, we presented a simplified space truss-arch model developed from unilateral truss-arch model. Main parameters in the new model were the cross-sectional area, transverse reinforcement raito, axial load, and material strength of the column. The reduction coefficient of concrete sterength owing to the severe cracking of column was also introduced in the model. Finally, 14 specimens under oblique horizontal load were tested to verified the feasibility and applicability of the space truss-arch model.

An Improved Functional Hierarchy Frame Model for System Maintainability

By means of analogy, this paper analyses the present functional hierarchyframe model for system maintainability, and presents an improved model. Practical applicationindicates that the improved model is visualized, more convenient and perfected over the perviousmodels.

W-F STRUCTURE: A NEW ALGORITHM ON WIRE-FRAME MODELING

This paper advances a new algorithm oriented to geometry modeling (GM) by using frame model. The elemental data structure of frame model is the vertex. This afeoithm provides a general and rapid method. By this way,we can link the vertices to construct the elemental frame and need not consider the topological relation among vertices which consist of the concrete entity. Then, we can combine the elemental frames to complete frame modeling by using aided-line method referring to concrete entity. We will discuss two keystones in the paper. Then we give a 3D geometry modeling example based on wire-frame model using the new algorithm.

Model Experiment on Integral Seismic Behavior of Reinforced Concrete Frame with Split Columns

Based on a series of previous studies, an experiment on the integral seismic behavior of a 1/3 scaled model of two-bay and three-story reinforced concrete frame with split columns at lower two stories is performed under cyclic loading. The original columns at lower two stories of the model frame are short columns and they are replaced by the split columns. The hysteresis curves between the horizontal cyclic load and the lateral displacement at the top of the model frame, indicate that under the cyclic loading, the model frame undergoes the process of cracking, yielding, and maximum loading before being destroyed at the ultimate load. They also indicate that the model frame has better ductility, and the ratio of the ultimate displacement to the yielding displacement, reaches 6.0. The yielding process of the model frame shows that for the frame with split columns, plastic hinges are generated at the ends of beams and then the columns begin yielding while the frame still possesses the bearing and deformation capacity. The design idea of directly changing the short column to long one in the reinforced concrete frame may be realized by replacing the short column with the split one.

新型分层装配式节点钢框架地震易损性分析

为提高装配式钢框架的装配效率,结合节点抗震性能要求,提出一种新型全螺栓分层装配式节点。对新型和传统两类节点进行抗震性能试验研究,并把节点参数引入整体框架模型中,采用SAP2000建立两类框架模型并进行增量动力分析。考虑基于层间位移角的单参数损伤模型和基于变形与累积耗能的双参数损伤模型,定义结构性能水准限值并划分破坏等级,对结构进行地震易损性分析。结果表明:在单、双参数损伤指标下,新型节点框架的易损性曲线都包络于传统节点钢框架的易损性曲线内,且新型节点框架的抗倒塌储备系数更大,说明采用新型节点能降低结构在各破坏状态下的失效概率,提高框架的抗倒塌能力;在LS1、LS2极限状态下结构基于单参数损伤指标的峰值加速度中位值比基于双参数损伤指标下的峰值加速度中位值小,在LS3、LS4极限状态下则相反,说明累积耗能对结构抗震性能评估影响明显,结合双参数损伤指标能更好地预测结构的损伤程度;新型节点框架在单、双参数损伤模型下的倒塌储备系数均高于传统框架,说明新型框架的抗倒塌储备能力更高,有利于结构抗震。

基于特性的牵引车-半挂车刚柔组合车架动力学模型研究

商用车较大的车架柔性会影响到整车的操纵稳定性和乘坐舒适性,尤其是在共振时车架柔性会放大对车辆运动品质的影响。为实时模拟牵引车-半挂车的车架运动,采用基于总成特性的建模技术路线,根据运动响应频域将车架运动解耦为低频刚体运动和高频柔体运动,并将车架模型模块化划分为基于多体动力学的刚体车架模块、基于模态综合法的柔体车架模块,然后将两模块求解结果叠加形成刚柔组合车架模型。最后,将车架模型嵌入牵引车89DOF-半挂车73DOF整车模型中,针对某款商用车进行仿真,通过对比实车场地试验结果,验证了模型的有效性。

增层框架-摇摆墙体系抗震性能研究

目的基于既有建筑的结构无法满足使用需求现状,通过质量调节及变形模式控制实现结构自振周期延长与损伤可控。方法提出增层框架-摇摆墙体系,对该结构进行理论分析,研究增层对整体结构地震效应的影响机理;利用SAP2000平台建立五个有限元模型,基于规范反应谱开展参数敏感性、静力弹塑性和动力弹塑性分析;并在此基础上,提出摇摆墙简化力学模型。结果增层的质量及高度对整体结构地震作用影响显著;与原框架相比,增层后结构基本自振周期最大延长31.7%,最大弹塑性极限位移响应降低11.5%,最大位移角响应降低20.2%,结构变形不均匀性降低22.0%;与框架-摇摆墙相比,增层后摇摆墙弯矩在弹塑性极限状态下降低33.9%。结论合理设置增层框架-摇摆墙可以小幅降低结构整体地震作用,减小结构地震响应,对结构变形模式可实现有效控制;所建立的摇摆墙简化力学模型可合理反应地震作用下墙体弯矩分布,并使设计偏于安全。

A MULTIPLE STRUCTURE RECONSTRUCTION ALGORITHM BASED ON WIRE FRAME MODEL

A “LAG & RLC” visualization algorithm has been presented to display a clear three dimensional structure from stereo slice data which has the characteristics of multiple layer structure. This algorithm is based on wire frame model which can do multiple logical operations and has multiple display effects. It has wide use in biomedical science and computer graphics. The practical system is based on PC with a TVGA adapter at least 512k byte display memory and 2M byte extended memory.

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。

基于坐标时间序列的地心运动分析与预测

地心运动会影响地球参考框架原点的准确性,是地球参考框架进行非线性维持必须考虑的因素之一,因此提出对地心运动进行多尺度的建模和预测,以实现毫米级地球参考框架的建立和维持。采用网平移法计算的地心运动、全球地球物理流体中心(global geophysical fluids center,GGFC)和国际GNSS服务(international gnss service,IGS)第三次重处理(IGSR03)提供的3组地心运动数据,首先对其一致性和差异进行了分析,然后分别利用谐波模型和Diff-LSTM模型对地心运动进行了长期和短期的建模与预测,结果显示,GGFC地心运动的预测精度优于1.5 mm,而Diff-LSTM模型的地心运动预测结果在短期内优于谐波模型,当预测步长为17时,GGFC和IGSR03的地心运动预测精度均能达到甚至优于1 mm。表明地心运动的预测精度能够满足基于地球质量中心(center of mass of the total earth system,CM)的瞬时地球参考框架的建立与维持。

基于虚拟增强现实交互技术的茶疗养生文旅产业研究

以茶疗养生为主题,以虚拟增强现实交互(augmented reality,AR)技术为科技手段和技术优势,通过创新驱动发展实现茶疗养生文旅场景设计应用的新突破。在现实场景下,用户可使用具备AR功能的各种智能设备,通过识别物理空间中的标识物触发AR应用,从而实现茶疗养生信息及时推送,实现现实场景与虚拟信息之间的交互,从而达到信息补充连贯及情景增强效果,使用户构建起茶疗养生的整体观念。通过解析茶疗养生文旅产业的研发思路,丰富茶疗养生信息体系的承载维度,探索实现茶疗养生文旅产业迭代的新途径。

近海大气环境下RC框架结构时变地震易损性分析

由于近海大气环境中存在的氯离子会侵蚀RC框架结构,造成材料性能不断劣化,最终降低了RC框架结构的抗震性能。为研究近海大气环境下RC框架结构地震损伤风险变化规律,基于钢筋均匀锈蚀模型及混凝土开裂前后钢筋锈蚀速率的变化规律,提出了一种改进的钢筋锈蚀率概率模型,并构建材料性能劣化模型。在此基础上,根据解析易损性分析理论,建立考虑氯离子侵蚀的近海大气环境RC框架结构时变易损性分析方法,并构建典型结构,分析不同损伤状态下的时变易损性曲线,评估其时变易损性与损伤状态。研究结果表明:当地震动强度指标取值相同时,各损伤状态结构在服役龄期内的地震易损性呈现出非线性增大趋势,抗震性能不断退化;以易损性指数作为结构损伤指标时,按照我国规范设计的RC框架结构,在30 a服役龄期内能够满足我国三性能抗震设防水准。

木构架古建筑基本周期的分析方法

针对现行规范近似公式存在的不足,结合单层、两层砖围护墙木构架古建筑的构造特征,构建了设有集中质量和连续分布质量的悬臂杆分析模型,以考虑屋顶、楼盖的质量和位置,以及围护墙、木构架的质量和刚度分布规律。依据结构动力学原理,采用等效质量法将分析模型等效为单质点悬臂杆模型,推导了中部集中质量和连续分布质量的等效公式,以及基本自振周期的计算公式。所研制的分析模型较好地反映了古建筑的大屋顶、楼盖及围护墙对结构自振周期的影响,相应的计算公式可以得出结构的横向和纵向基本周期。结合3座典型古建筑的动力特性试验研究,介绍了计算公式的运用方法,并将基本周期的计算值与实测值进行了对比,表明提供的分析方法适用于围护墙在横向、纵向不同布置的木构架古建筑的基本周期分析。

既有框架结构的新型等效简化动力模型构建方法

为了实现对长期服役后的结构在地震、风等动荷载作用下安全性和舒适性的评估,利用监/检测数据建立一个能准确反映实际建筑在地震、风等动荷载作用下动力响应的结构动力学模型至关重要。本文针对非常普遍的框架建筑结构,提出了一种基于少量移动传感器的框架结构等效简化动力学模型构建方法。首先,提出建筑结构等效简化模型构建的层间剪力等效原理,证明了以该原理构建的简化模型具备准确模拟实际建筑结构动力响应的能力。其次,推导了框架结构简化模型形式,并研究了简化模型参数特点。然后,提出了一种框架结构简化模型参数的迭代识别方法,实现了仅使用少量无线移动传感器的简化模型参数识别。最后,通过一个12层3跨钢框架结构数值模拟算例,研究了在不预知结构刚度退化的具体形式和仅使用少量移动加速度传感器的条件下,由本文所提方法构建的等效简化模型对实际框架结构在不同水平动荷载作用下结构动力响应的预测能力。数值试验结果表明,等效简化模型能准确模拟不同荷载工况下框架结构加速度和位移响应。因此,本文提出的框架结构等效简化模型构建方法将在评估既有框架结构在风、地震等动荷载作用下的结构安全性和舒适性方面具有重要的应用前景。

CFRP及EWSS复合加固震损双层高架桥框架式桥墩恢复力模型研究

为研究碳纤维布(Carbon Fiber Reinforced Polymer,CFRP)及外包型钢(Externally Wrapped Steel Section,EWSS)复合加固震损双层高架桥框架式桥墩的恢复力模型,对1榀原型对比试件、1榀无预损加固试件和2榀遭受不同地震损伤加固试件进行了低周往复加载破坏试验,获取了滞回曲线并提取骨架曲线,分析其滞回特性,提出一种弹性段和强化段为双折线、下降段为指数函数且考虑初始损伤的骨架曲线模型;采用试验数据回归拟合方法,定量描述了试件滞回曲线卸载刚度的退化规律,考虑了同级加载承载力退化和定点指向特征,建立了恢复力模型。研究结果表明:复合加固试件滞回曲线捏缩现象明显,呈倒S型,各滞回环分别相交于骨架曲线上正向、负向荷载为屈服荷载0.25倍的点,峰值荷载后EWSS产生包辛格效应;所提出的骨架曲线模型对中度震损和重度震损加固试件下降段指数函数的参数k建议取值分别为3.6和3.4;所建立的骨架曲线模型和恢复力模型计算结果与试验实测结果吻合较好,可为该类结构弹塑性地震反应分析提供依据。