自锚式悬索桥磁流变阻尼器减震控制研究

为了减小自锚式悬索桥的地震响应,基于桥梁结构地震动力方程及磁流变阻尼器力学模型,建立桥梁结构—磁流变阻尼器减震系统并将其程序化,对某主跨350 m的独塔自锚式悬索桥进行减震控制研究,讨论了磁流变阻尼器输入电流、数目及安装位置对减震效果的影响。研究结果表明:采用磁流变阻尼器能够有效地减小自锚式悬索桥的纵向地震响应;随安装在塔梁之间顺桥向的磁流变阻尼器输入电流的增大及数目的增加,塔顶和主梁的纵向位移逐渐减小,结构的内力响应也得到有效控制;将全部磁流变阻尼器安装在塔梁之间顺桥向时减震效果最佳。     

Investigations concerning seismic response control of self-anchored suspension bridge with MR dampers

To mitigate the seismic response of self-anchored suspension bridges, equations of motion governing the coupled system of bridge- magneto-rheological (MR) dampers subject to seismic excitation are formulated by employing the phenomenological model of MR dampers. A corresponding computer program is developed and employed for studying the seismic response control of a self-anchored suspension bridge with a main span of 350 m. The effect of variable current and number of dampers on seismic response control is investigated. The numerical results indicate the longitudinal displacement of the tower top and bridge girder decrease with the increase in input current and number of MR dampers attached longitudinally at the tower-girder connections, and the internal forces of the tower are effectively attenuated as well. It appears that small electronic current (0.5 A in this study) may sufficiently attenuate the seismic responses for practical engineering applications.     

悬索桥易损性分析与简化模型

对中国当前已建和在建的车行悬索桥进行了统计分析,总结其分类特点,得到了统计意义上桥梁主要参数间的关系,并利用线性拟合得到趋势拟合公式。选取3座典型悬索桥（双塔地锚式平行双索面桥、双塔自锚式平行双索面桥、独塔自锚式空间索面桥）建立有限元模型,对影响悬索桥振动的主要参数进行了敏感度分析;利用塔底弯矩曲率曲线确定不同等级的损伤指标,采用增量动力分析(IDA)法得到地震反应需求值,通过计算不同损伤指标的能力需求比,对悬索桥的易损性进行分析。针对震后灾害快速评估的需求,建立单塔简化模型来计算易损性曲线。结果表明:对算例桥梁而言,主塔顺桥向弯曲振动,主塔刚度对自锚式平行索面悬索桥影响大,主缆刚度对地锚式平行索面悬索桥影响大;横桥向主塔刚度对3座桥影响均较大;地锚式悬索桥比自锚式悬索桥易损,而自锚式悬索桥中双塔平行索面桥抗震性能优于独塔空间索面桥;单塔简化模型在一定程度上能够满足震害后快速评估的需求,误差基本在工程上可以接受的范围。     

Seismic response analysis of self-anchored suspension bridge with multi-tower

Seismic performance of a self-anchored suspension bridge with three-tower were investigated. A three-dimensional nonlinear finite element model of the bridge was developed using Sap2000. Nonlinear time history analysis was conducted using Fast Nonlinear Analysis Method (FNA), while beam-column effect and nonlinear behavior of bearing and damper were taken into consideration. The analyze results showed that the middle tower was more vulnerable compared with the two side towers; there existed risk of buckling of composite beam, and the most vulnerable part lied near steel-concrete composite segment. Viscous dampers were effective to reduce seismic response of towers as well as girders.

     

Semi‐active control of seismic response of tall buildings with podium structure using ER/MR dampers

A tall building with a large podium structure under earthquake excitation may suffer from a whipping effect due to the sudden change of building lateral stiffness at the top of the podium structure. This paper thus explores the possibility of using electrorheological (ER) dampers or magnetorheological (MR) dampers to connect the podium structure to the tower structure to prevent this whipping effect and to reduce the seismic response of both structures. A set of governing equations of motion for the tower–damper–podium system is first derived, in which the stiffness of the member connecting the ER/MR damper to the structures is taken into consideration. Based on the principle of instantaneous sub‐optimal active control, a semi‐active sub‐optimal displacement control algorithm is then proposed. To demonstrate the effectiveness of semi‐active control of the system under consideration, a 20‐storey tower structure with a 5‐storey podium structure subjected to earthquake excitation is finally selected as a numerical example. The results from the numerical example imply that, as a kind of intelligent control device, ER/MR dampers can significantly mitigate the seismic whipping effect on the tower structure and reduce the seismic responses of both the tower structure and the podium structure. Copyright © 2001 John Wiley & Sons, Ltd.     

Calculation method on shape finding of self-anchored suspension bridge with spatial cables

Based on the spatial model, a reliable and accurate calculation method on the shape finding of self-anchored suspension bridge with spatial cables was studied in this paper. On the principle that the shape of the main cables between hangers is catenary, the iteration method of calculating the shapes of the spatial main cables under the load of hanger forces was deduced. The reasonable position of the saddle was determined according to the shape and the theoretical joint point of the main cables. The shapes of the main cables at completed cable stage were calculated based on the unchanging principle of the zero-stress lengths of the main cables. By using a numerical method combining with the finite element method, one self-anchored suspension bridge with spatial cables was analyzed. The zero-stress length of the main cables, the position of the saddle, and the pre-offsetting of the saddle of the self-anchored suspension bridge were given. The reasonable shapes of the main cables at bridge completion stage and completed cable stage were presented. The results show that the shape-finding calculation method is effective and reliable. __________ Translated from Journal of Hunan University (Natural Sciences), 2007, 34(12): 20–25 [译自: 湖南大学学报(自然科学版)]     

Experimental research on the multilayer compartmental particle damper and its application methods on long-period bridge structures

Particle damping technology has attracted extensive research and engineering application interest in the field of vibration control due to its prominent advantages, including wide working frequency bands, ease of installation, longer durability and insensitivity to extreme temperatures. To introduce particle damping technology to long-period structure seismic control, a novel multilayer compartmental particle damper (MCPD) was proposed, and a 1/20 scale test model of a typical long-period self-anchored suspension bridge with a single tower was designed and fabricated. The model was subjected to a series of shaking table tests with and without the MCPD. The results showed that the seismic responses of the flexible or semi-flexible bridge towers of long-period bridges influence the seismic responses of the main beam. The MCPD can be conveniently installed on the main beam and bridge tower and can effectively reduce the longitudinal peak displacement and the root mean square acceleration of the main beam and tower. In addition, no particle accumulation was observed during the tests. A well-designed MCPD can achieve significant damping for long-period structures under seismic excitations of different intensities. These results indicate that the application of MCPDs for seismic control of single-tower self-anchored suspension bridges and other long-period structures is viable.     

Limit span of self-anchored cable-stayed suspension cooperation system bridge based on strength

The limit span of self-anchored cable-stayed suspension bridge is deduced. The relations among the geometrical parameters, loads and material characteristics are also analyzed. Based on the material strength and commonly used materials, the limit spans of self-anchored cable-stayed suspension bridges with concrete girder or steel girder under vertical static load are discussed in detail. The corresponding upper limit spans and the effect of the factors on the span are given. The results indicate that increasing rise-span ratio, height-span ratio and cable-stayed segment length or reducing the second dead load could increase the cooperation system span. __________ Translated from Journal of Dalian University of Technology, 2008, 48(3): 387–391 [译自: 大连理工大学学报]     

自锚式悬索桥动力特性研究

以三汊矶自锚式悬索桥工程为例,利用通用有限元分析软件ANSYS建立大桥的动力模型,计算了前16阶频率及振型,并具体分析了恒载、加劲梁刚度、桥塔刚度等结构参数,提出了自锚式悬索桥动力特性的影响规律。     

Seismic performance of benchmark highway bridge installed with piezoelectric friction dampers

Dynamic response of the benchmark highway bridge installed with semi-active piezoelectric friction dampers (PFDs) is investigated under six bidirectional earthquake ground motions. PFD utilises the response of the structure to develop control actions by adjusting frictional damping characteristics of the system. Conventional friction dampers abruptly fluctuate between stick-slip states. On the other hand, PFDs change the friction force continuously and smoothly. The study is based on the simplified lumped mass finite-element model of the 91/5 highway bridge, located in Southern California. The parameters affecting the performance of PFDs are gain factors, coefficient of friction and the preload on damper. Exhaustive studies are carried out to determine the most optimum values of these parameters. Eight dampers are installed at each deck-end and abutment junction (phase I). Additional four dampers are installed at the centre (phase II), at the junction of bent beam and piers of the bridge. In each case, the response of the bridge is compared with the corresponding uncontrolled case and that controlled by the alternate sample semi-active control strategy, using magnetorheological (MR) dampers. It is concluded that with the installation of PFDs, the seismic response of the bridge under near-fault motions can be controlled significantly. The PFDs are quite effective in reducing the peak response quantities of the bridge to a level comparable to or superior to that of the MR dampers.     

Wind-induced vibration control of Hefei TV tower with fluid viscous damper

The Hefei TV tower is taken as an analytical case to examine the control method with a fluid viscous damper under wind load fluctuation. Firstly, according to the random vibration theory, the effect of fluctuating wind on the tower can be modeled as a 19-dimensional correlated random process, and the wind-induced vibration analysis of the tower subjected to dynamic wind load was further obtained. On the basis of the others’ works, a bimodel dynamic model is proposed. Finally, a dynamic model is proposed to study the wind-induced vibration control analysis using viscous fluid dampers, and the optimal damping coefficient is obtained regarding the wind-induced response of the upper turret as optimization objectives. Analysis results show that the maximum peak response of the tower under dynamic wind load is far beyond the allowable range of the code. The wind-induced responses and the wind vibration input energy of the tower are decreased greatly by using a fluid viscous damper, and the peak acceleration responses of the upper turret is reduced by 43.4%. __________ Translated from Journal of Southeast University (Natural Science Edition), 2008, 37(6): 1018–1022 [译自: 东南大学学报(自然科学版)]     

固镇浍河二桥(徐窑渡改桥工程)悬索系统施工技术

自锚式悬索桥是以承受拉力的缆索或链索作为主要承重构件的桥梁,由悬索、索塔、锚碇、吊杆、桥面系等部分组成。本文结合固镇浍河二桥(徐窑渡改桥工程)工程实例,全面系统地介绍了单塔双跨自锚式悬索桥悬索系统的施工技术和施工工艺,为以后同类型桥梁施工提供了借鉴和经验。     

福州鼓山大桥主桥独塔自锚式悬索桥设计

对福州鼓山大桥主桥独塔自锚式悬索桥设计进行了介绍,分别阐述了主桥结构总体设计、基础结构设计、主塔结构设计、主梁结构设计、缆索系统设计,总结了鼓山大桥自锚式悬索桥的主要设计特点,对同类桥梁结构设计具有一定指导意义。     

螺洲大桥主塔施工技术

螺洲大桥三塔自锚式悬索桥主塔柱首次采用分节段现浇工艺进行施工,介绍了汽车吊结合安全爬梯形式施工主塔的成功经验。同时在施工过程采用了全过程施工控制方法,保证了主塔的线形满足设计精度要求。     

超大跨度斜拉桥的地震位移控制

对于千米级的超大跨度斜拉桥 ,一般要求塔柱在强震下基本保持弹性 ,因此往往选择隔震体系 (全飘浮或支承 )来减小地震反应。但是采用隔震体系的超大跨度斜拉桥在强震下会产生很大的梁端位移 ,必须加以控制才能保证整个结构的抗震安全性。本文从地震位移控制的机理出发 ,探讨了控制地震位移的方法、具体的装置及参数选择 ,最后介绍了超大跨度斜拉桥地震位移控制的实例。实例分析表明 ,只要合理选取参数 ,在塔、梁间设置弹性连接装置或阻尼器均能有效地控制梁端的地震位移 ,但阻尼器的效果更为理想。     

桃花峪黄河大桥主桥工程上部结构施工关键技术

悬索桥因其跨越能力强,应用广泛。但与地锚式悬索桥相比,自锚式悬索桥加劲梁受力更复杂。因为通常要按"先梁后缆"顺序施工,故周期长,技术难度更大。桃花峪黄河大桥主桥为(160+406+160)m3跨自锚式悬索桥,为目前国内最长的自锚式悬索桥。结合武(陟)西(峡)高速公路桃花峪黄河特大桥主桥工程实例,简要介绍了在特殊结构与复杂环境条件下该桥上部结构施工关键技术,包括主塔、钢箱梁、主缆和吊杆安装与体系转换等。     

城市隔震高架桥梁地震反应的半主动控制

研究应用磁流变(MR)阻尼器对隔震连续梁桥邻联相对位移的半主动控制,并采用离线优化与在线自调整相结合进行模糊控制(FLC)。以邻联最大相对位移最小化为目标函数,对基本模糊控制器的隶属函数、量化因子、比例因子进行离线遗传优化;对优化后的模糊控制器的量化因子和比例因子进行在线自调整;数值仿真分析一多跨隔震连续梁桥的简化四自由度体系的半主动控制,比较不同控制方案的控制效果。结果表明,将MR阻尼器安装在上部结构与桥墩之间对桥梁邻联相对位移的控制效果优于将其安装在邻联之间;半主动控制能同时有效控制邻联最大相对位移与支座变形;与普通模糊控制以及仅采用遗传优化的模糊控制相比,具有在线自调整功能的模糊控制具有更好的控制效果和鲁棒性。     

螺洲大桥大型鞍座底板一次性预埋施工技术

螺洲大桥主桥为自锚式三塔悬索桥,主塔塔顶面积小,钢筋、预埋件密集,特别是高控制精度要求的鞍座底板预埋,给塔顶混凝土施工带来相当大的困难。文章从塔顶结构、鞍座底板形式出发,经过分析、研究和现场试验,总结出大型预埋件灌浆技术,为类似工程提供施工依据。     

大跨度双塔悬索桥在地震动行波激励下的响应规律研究

本文以一座主跨850m的大跨双塔悬索桥为工程背景,采用时程分析法研究了行波效应大跨双塔悬索桥地震响应的影响。通过建立三维有限元分析模型,在分析了大跨度双塔地锚式悬索桥动力特性及一致激励下地震响应规律的基础上,进一步探讨了行波效应对大跨双塔地锚式悬索桥地震响应的影响规律。分析结果表明:地震波纵向行波作用下,主塔的地震响应随着视波速的减小而先减小后增大;主梁的竖向振动则较一致激励下显著增大;主缆及吊索轴力则受地震动行波效应的影响不大。     

高烈度区斜拉桥横向约束方案优化分析

为了确定强震作用下斜拉桥合理的横向抗震约束体系,以可克达拉大桥为工程背景,采用非线性时程分析法,分析了4种横向约束体系即横向滑动体系、全限位体系、位移相关型减震体系和速度相关型减震体系对强震区大跨度桥梁地震响应的影响,重点对钢阻尼器的屈服荷载和黏滞阻尼器的位置及相关参数进行优化分析,并与其他体系的地震响应进行了对比。结果表明：在强震作用下,对于大跨度桥梁横向滑动体系和全限位体系均不是理想的抗震体系;而在墩梁、塔梁之间设置减隔震装置可以有效减少横桥向的墩梁、塔梁的相对位移及地震剪力和弯矩;然而,从桥梁正常使用的角度来看,塔梁之间布设横向钢阻尼器装置优于黏滞阻尼器装置。