考虑流固动力相互作用的大型渡槽地震响应研究

根据符拉索夫及豪斯纳尔理论建立考虑槽内水体与渡槽槽身流固耦合的渡槽薄壁结构空间地震响应计算模型,该模型综合考虑了渡槽横向、竖向、纵向、自由扭转变形、约束扭转变形以及槽内水体对槽身的流-固动力相互作用等。由能量变分原理推导给出了渡槽薄壁梁段单元刚度矩阵及质量矩阵,按粘滞阻尼假设建立了渡槽结构阻尼矩阵。利用该模型对南水北调中线水利工程某大型渡槽进行了多工况地震时程响应计算。计算结果说明在地震作用下,渡槽槽内水质量对渡槽的横向地震响应有较大影响,在大型渡槽抗震设计计算时应予以重视。本文模型计算简单易行,是考虑槽内水体流固耦合作用的渡槽薄壁结构实用的地震响应计算模型,计算结果可为大型渡槽的抗震设计提供参考。     

大型渡槽结构地震响应分析

大型渡槽槽身采用薄壁杆件结构,渡槽支架与槽身采用盆式橡胶支座连接,根据此结构特点,提出了大型渡槽结构地震响应分析模型.该模型综合考虑了渡槽槽身横向弯扭耦合振动、约束扭转变形、渡槽支架变形和盆式橡胶支座等对渡槽动力响应的影响.采用能量原理给出了渡槽梁段单元的刚度矩阵、质量矩阵和阻尼矩阵的表达式.具体计算了某大型渡槽的地震响应,计算结果表明本文模型计算渡槽结构的地震时程响应与大型结构分析程序SAP93计算的结果十分接近,但本文方法相当简单,计算工作量小,使用方便,是大型渡槽结构地震响应计算的实用模型.     

大型储罐自振特性分析

为了给大型储罐地震动力响应进一步分析提供数据,建立了大型储罐有限元简化模型,考虑了罐体的固液耦合作用,对储罐系统的自振特性进行了分析,结果表明,有限元结果与规范计算结果误差很小,计算结果可靠。     

槽内水流对拱式渡槽流固耦合响应的影响研究

为明确渡槽槽内水流流速和质量对拱式渡槽流固耦合响应的影响,以云南滇中引水工程中的鲁支河拱式渡槽为背景,基于ANSYS Workbench和Fluent软件,建立考虑单向流固耦合的有限元模型,分析槽内水流对渡槽的位移和应力响应.结果表明:槽内水流在1.0～2.5m/s范围内时,流速对槽身内壁和底板的流固耦合响应影响较小,...     

考虑流固耦合作用的索膜结构开洞与封闭条件下的风压风振模拟

在任意拉格朗日-欧拉(Arbitrary Lagrangian-Eulerian,简称ALE)描述下,引入Menter SST湍流模式和非线性有限元方法,建立了耦合方程迭代求解策略,进而研究考虑流固耦合作用的索膜结构风振响应.数值模拟了结构膜帽开洞和封闭等工况下的伞形索膜结构风致动力响应,揭示和总结出某些规律.     

基于不同水体模型的渡槽结构动力特性对比分析

考虑到渡槽槽体内水体的晃动对结构模态正交性的影响,采用有限元以及有限体积方法分析了两种不同高宽比的渡槽结构在附加质量模型、Housner水体模型以及势流体这三种水体模型下的流固耦合动力特性,包括自振频率和主振型。在此基础上,探讨了三种不同水体模型下渡槽结构流固耦合模态的差异,得到渡槽结构在不同水体模型下的动力特性敏感性因素,为渡槽抗震抗风设计提供参考依据。     

地震和波浪力共同作用下桥墩的动力响应研究

波浪力作用采用非线性的Morison方程,而桥墩按剪切模型进行离散,建立了桥墩在地震和波浪力共同作用下的非线性动力方程,并采用时程迭代法计算分析,发现不考虑流固耦合时桥墩的动力响应计算结果明显小于考虑流固耦合时的计算结果。因此,在地震、波浪力共同作用下,考虑流固耦合更符合实际情况。     

考虑桩-土动力相互作用的渡槽结构水平地震响应分析

以Housner流-固耦合模型和Penzien桩-土相互作用模型为基础,建立一种同时考虑流-固耦合与桩-土相互作用的渡槽结构简化计算模型,并给出其计算参数。该计算模型分为等价体系和自由场体系,并采用自由场输入。推导同时考虑弯曲变形和剪切变形时的群桩刚度矩阵,采用分别计算各子结构阻尼的方式来考虑整个结构的阻尼,并采用等效线性化原理来考虑土体的非线性。以某渡槽为例,采用该模型对其进行分析,并与刚性基础模型对比。计算结果表明,两种情况下的自振特性和水平地震响应均有较大差别,在渡槽抗震研究与设计中不能忽略桩-土相互作用。同时采用该计算模型对拟动力试验模型进行分析,并与试验结果比较,二者基本一致,说明计算模型的有效性。     

均匀流场作用下ETFE气枕的流固耦合分析（英文）

ETFE(Ethylene-Tetra-Fluoro-Ethylene)气枕由于自重轻、造型丰富等优点,广泛应用于土木工程领域的大跨空间钢结构如水立方等以及航空航天领域的空间可展结构。ETFE气枕属于风敏感结构,在风荷载作用下,易产生较大的变形和振动,进而使得周围风场发生变化,引起显著的流固耦合效应。这种耦合效应可以通过结构形状改变、附加质量、气动阻尼和气承刚度的变化来表征。目前相关研究主要对张拉膜结构在均匀流情况下的流固耦合作用进行了研究,尚未发现有关ETFE气枕等充气膜结构方面的研究报道。以方形ETFE气枕为研究对象,借助商用有限元软件ADINA,通过将CFD(Computational Fluid Dynamics)/CSD (Computational Structure Dynamics)分析结果与FSI(Fluid Structure Interaction)分析结果进行对比,探究其在均匀流场情况下的流固耦合作用的特点以及对动力响应的影响规律。数值计算中忽略能量的耗散,因此没有考虑气动阻尼的影响,通过有势流体考虑气承刚度的影响,着重研究了流固耦合作用中气枕形状改变和附加质量的影响作用。主要研究内容与结论如下:假定外部流场为均匀层流场,采用8结点层流单元进行离散; ETFE气枕外围薄膜为线弹性材料且其变形满足大转动、小应变条件,采用3D-4结点膜单元进行离散; ETFE气枕的内充气体为小扰动、无旋的理想流体,采用8结点线性势流体单元进行离散。在CFD模块,通过瞬态分析求得ETFE气枕刚性模型表面的风压分布和风荷载时程,然后将风压时程施加在CSD模块中ETFE气枕的膜面上,借助隐式时间积分进行时程分析,求得在不考虑流固耦合作用时气枕的风致响应。通过分别在CFD和CSD模块中设置流固耦合界面,并在CFD模块中引入ALE(Arbitary Lagrangian-Euler)网格离散计算域以考虑流固耦合边界的运动问题,对均匀流场中的ETFE气枕进行双向耦合分析,计算其在考虑流固耦合作用情况下的表面风压和风致响应。通过将CFD/CSD分析结果与FSI分析结果进行对比,研究流固耦合作用对ETFE气枕动力响应的影响规律。结果表明:两种情形下得到的风压分布和数值大致相同,说明在外部均匀流场情况下,气枕形状改变对流场的影响很小;而两种情形下的内压、位移、速度、加速度和应力响应时程结果差异较大,说明在外部均匀流场情况下,附加质量对ETFE气枕动力响应具有显著影响。可见,均匀流场与ETFE气枕的流固耦合作用,在不考虑气动阻尼的情况下,主要体现为附加质量的影响。     

流固耦合理论研究进展

流固耦合(Fluid-Structure Interaction,FSI)是目前很多领域研究的热点和难点之一.与国外相比,国内在该方面的研究相对滞后或片面.本文对FSI研究现状和意义、传统风工程理论和方法、流体力学基本理论、流体力学有限元、FSI理论和分析方法等内容作了介绍,探讨了耦合界面条件、边界追踪、网格更新以及大型非线性方程求解等问题,特别对强耦合和弱耦合算法作了理论上的探讨和区分.本文可为流固耦合理论数值模拟提供理论和方法的指导.     

简支梁式渡槽考虑流固耦合的横向地震三维动力响应分析

以横向地震作用下的大跨度简支梁式渡槽为对象,研究其在行波效应以及渡槽两端支撑不同高时的三维流固耦合响应。研究表明支撑不等高的渡槽,由于其两端刚度不均匀,槽身侧移受到较大影响,刚度变小则侧移变大,反之亦然。研究还表明,行波效应对渡槽的影响比较明显,激励一致情况下的槽身各截面侧移峰值要明显小于激励不一致的情况,但是槽身各截面的弯矩却恰恰相反,激励一致情况下的各截面弯矩峰值要明显大于激励不一致的情况。     

3. Risk Management of Major Aqueducts

T he paper D escribes the methodology applied to determine the security of ageing aqueducts by the application of risk analysis techniques. Targets for safety and reliability are suggested within a strategy for risk management.
A case study of a security study of a major aqueduct is briefly described.     

大型U形渡槽动力性能分析

以东深供水改造工程中樟洋渡槽和某小型渡槽为研究对象 ,对比分析大型预应力U形渡槽结构动力特性 ,研究渡槽结构在Mexico强震激励下的振动反应 ,以获得渡槽中动水压力资料。研究表明常规的抗震设计方法可以满足小型渡槽结构的抗震设计要求 ,而大型渡槽中水体的大幅晃动作用较大程度地改变了水压力、槽体应力的分布和数值 ,对渡槽中预应力钢筋不利 ,在渡槽的抗震设计中 ,动水压力应该作为一项主要的外荷载予以考虑。     

Characterization of building stones from the ancient Tyana aqueducts,Central Anatolia,Turkey: implications on the factors of deterioration processes

Many archaeological and historical monuments constructed by different civilizations over the last 5500 years can be observed in the Ni?de region located in central Anatolia. The Tyana aqueduct as a continuation of the Roman Pool is one such important historical monument. The aqueducts that carried the water of the Roman Pool to the ancient city of Tyana were constructed during the time of the Roman emperors Trajan, Hadrian and Marcus Aurelius Antoninus. Half of the total length of the aqueducts (3 km) is on the surface and the rest is buried. The engineering properties of the rocks used in such archaeological and historical buildings are very important in terms of conserving these structures for future generations. In this study, the geomechanical and geotechnical features of the Tyana aqueducts were investigated to understand the rock types, deterioration in the stones over time and problems originating from these features. Also, for restoration purposes, the ancient stone quarry areas for the aqueducts were identified, and the chemical, petrographical and geomechanical properties of fresh travertine blocks from these quarries were determined. The main rock type used as building stones in the aqueducts is Mio-Pliocene travertine. Laboratory studies were performed to determine the mineralogical, petrographic and petrophysical properties of the building stone samples. Fresh and used travertine samples were composed exclusively of calcite crystal. The results of chemical analyses were similar for fresh and used travertine samples. To determine the geomechanical properties of the travertines, dry unit weight, water absorption, effective porosity, P-wave velocity, Böhme abrasion test, capillary water absorption and uniaxial compressive strength experiments were conducted. In addition, Schmidt hammer hardness measurements were performed on site for the different levels and different textural characteristics of the belts on the travertines. According to the experimental data obtained, higher strength was displayed by samples with fine grains, massive texture and low porosity. The deterioration effects in most of the travertines used in the original structure are very low. In addition to human effects, the use of small stone dimensions (especially the stones used in belts as keystones) and the use of stone from the same quarry but with features that differ or are inferior are thought to be factors in the destruction of the Tyana aqueducts.     

Asset Appraisal of Trunk Mains

Over the past decade, much attention has been paid to the assessment of water distribution networks. Attention now is turning towards the larger diameter trunk mains. The increased scale and cost of investigative work means that a change of approach is needed and, in some cases, new investigative techniques.
This paper discusses the general approach to the appraisal of trunk mains (and aqueducts) and, based on practical experience, considers solutions to a number of problems associated with inspection work.
A case study is presented, based upon a preliminary appraisal of the Vyrnwy Aqueduct, which was carried out in 1988–89. The aqueduct was first commissioned in 1891, and now contains some 325 km of large diameter pipes, in both cast iron and steel.     

考虑流体结构耦合作用的单柱三面广告牌结构的风致动力响应

流体-结构耦合作用的力学问题是当前计算风工程领域的研究重点,针对当前广告牌结构风灾破坏的普遍性,采用ADINA有限元软件对单柱三面广告牌结构进行了流体-结构耦合风致动力响应数值模拟计算,得出了该类结构的风振系数和体型系数,可供工程参考使用。     

膜结构风致动力响应数值模拟

许多工程领域中都存在流体-结构耦合作用现象,膜结构作为一种风敏感型结构,此现象在其风致动力响应方面表现更为明显。针对膜结构本身的特点,给出了流体-结构耦合作用下流体的基本控制方程的ALE(Arbitrary Lagrangian-Eulerian)描述、结构的基本控制方程和求解耦合方程的直接求解算法。采用Adina软件实现了简单张拉膜结构的流体-结构耦合作用风致动力响应数值模拟,并与已有风洞试验结果进行了比较。对比结果表明,给出的方法可以准确地计算出柔性结构考虑流体-结构耦合作用的风致动力响应,可为相关的科学研究和工程设计提供理论依据。     

Aqueduct Management Planning: Thirlmere, Haweswater and Vyrnwy Aqueducts

Between 1988 and 1992, an asset study of North West Water Limited's three largest aqueducts was carried out to assess their condition and rehabilitation needs. About 360 km of the aqueduct system, including approximately 1700 structures, 160 km of tunnel and conduit, 700 km of pipeline and 4000 valves, were covered by the study. A wide range of survey techniques was used, some being specially developed as part of the study, and a unified system of condition assessment and prioritization of rehabilitation needs was devised.
The paper (a) describes the overall approach and survey techniques, (b) discusses the methods of assessment used, (c) summarizes the conditions of the assets whose ages vary from 20–100 years, and (d) reviews some of the rehabilitation works proposed and executed.