某三塔斜拉橋動力特性分析

1、城市道橋與防洪2009年5月第5期 收稿日期:2009-02-03作者簡介:徐永勝(1974-,男,福建建甌人,工程師,從事市政橋隧設計工作。摘要:某大橋是國內首座三塔斜拉橋,結構形式復雜。該文首先建立了大橋的三維有限元動力分析的三主梁模型,采用大型有限元通用分析程序ANSYS 對該橋的動力特性進行了分析,并給出了結構的自重效應對固有動力特性的影響。結果表明,這類斜拉橋結構的自重效應對整體固有頻率影響很小。關鍵詞:三塔斜拉橋;有限元通用分析程序;動力特性;有限元模型中圖分類號:U448.27文獻標識碼:A文章編號:1009-7716(200905-0064-02某三塔斜拉橋動力特性分析徐永勝(

2、廣州市市政工程設計研究院,廣東廣州5100601概述某大橋全長6km ,為公路特大型橋梁。大橋主橋為三塔雙索面漂浮式混凝土斜拉橋,跨徑布置為130m+2×310m+130m ,主梁采用開口混凝土截面,梁寬23.4m ,梁高為2.5m ,邊塔高99.311m ,中塔高125.684m ,屬塔梁懸浮體系,索距為8m ,兩邊跨各布置17對索,中跨布置23對索。主梁形式采用開口型斷面,斷面形式見圖1。本文建立了該橋的三維有限元動力分析模型,采用大型有限元分析程序ANSYS 對該橋的動力特性進行了分析,并分析了結構自重效應對整體固有頻率的影響。2大橋有限元模型在大跨度橋梁全橋的結構分析中,一般

3、都采用平面或空間有限元桿系結構進行描述。其中,墩、塔部分簡化為若干通過其中心線的二節(jié)點梁單元,而主纜、吊桿、斜拉索簡化為二節(jié)點桿單元,在平面分析時,一般都直接將主梁處理為二維梁單元。但在空間分析時,對主梁的處理有多種方式。由于主梁為一個實體,其橫向尺寸較大,在其縱向的不同位置還有縱梁、拉索等構件連接,它的側向和扭轉方向的剛度構件的連接特性都使得僅用一個空間梁單元不能達到正確的描述。因而,必須對主梁的縱向和橫向剛度進行分解。目前,應用較多的主梁計算模型主要有三種:魚骨式、雙梁式和三梁式,如圖2。魚骨式模型適用于扭轉剛度較大的閉口箱型截面主梁,它把橋梁的剛度和質量都集中到中間節(jié)點上,節(jié)點和拉索之間

4、處理為剛臂連接或處理為主從關系。該模型的主梁的剛度和質量的模擬較準確,但橫梁的剛度和主梁的翹曲剛度反映不橋梁結構642009年5月第5期城市道橋與防洪足。雙梁式模型將主梁的剛度和質量平均分配給兩個主梁,這樣可以近似地考慮約束扭轉的貢獻,使用于開口和半閉口截面的主梁,該模型的缺點是對側向剛度和約束扭轉的剛度模擬不準確。三梁式模型由橋軸線上的中梁和位于索面處的兩個邊梁橫向共同組成,通過適當?shù)膭偠群唾|量分配來滿足等效條件。該模型力學性能好,但單元數(shù)多,計算梁大,主要用于具有開口斷面的主梁。三主梁模型截面性質和質量分析見表1。表1中有關符號定義如下(其中i =1代表中主梁,i =2代表邊主梁:A 為橋

5、截面面積,J x 為橋截面豎向慣性矩,J z 為橋截面?zhèn)认驊T性矩,J d 為橋截面自由扭轉慣性矩,J w 為橋截面約束扭轉慣性矩,M 為橋截面單位跨長重量, I m 為橋面單位跨長轉動慣量?？紤]到大橋為開口型斷面,為了正確地考慮約束扭轉剛度的貢獻,采用三梁式計算模式來模擬加勁梁。在建模時,采用三維梁單元來模擬橋面主梁和塔,采用桿單元模擬斜拉橋,壓重單元采用質量單元來模擬,這樣全橋共有1038個單元。橋面簡化后的三主梁截面特性見表2,有限元模型圖見圖3。3整體動力特性分析對上述有限元模型采用大型有限元分析通用程序ANSYS 對大橋進行了整體動力特性分析。為研究成橋內力對結構動力特性的影響,本文計

6、算了考慮成橋內力狀態(tài)和不考慮成橋內力狀態(tài)兩種情況下的振型和頻率,計算結果見表3。從表3可以看出,拉索垂度和成橋內力狀態(tài)對大橋的整體動力特性的影響很小。圖4圖6為該橋的振型圖。 4結論大橋為國內首座三塔斜拉橋,結構形式復雜。本文根據(jù)大橋的結構形式,采用三主梁模型表1三主梁模型中的主梁截面性質和質量分布等效原則公式主梁截面性質和質量分布縱向剛度等效和側向剛度等效A 1=A ,A 2=0,J z 1=J z ,J z 2=0A 1=A ,A 2=0,J z 1=J z ,J z 2=0豎向剛度等效和約束扭轉剛度等效J x 1+2J x 2=J x ,2J x 2=J J z 1=J z -J b 2

7、,J x 2=J 2b 2只有扭轉剛度等效J d 1+2J d 2=J dJ d 1=J d ,J d 2=0質量系統(tǒng)等效M 1+2M 2=M ,2M 2b 2=I MM 1=M -I M b2,M 2=I M 2b2表2主梁截面幾何特性梁A J z J xJ d 中主梁15.167 5.9001220.5500.218邊主梁1.9600.03.413表3某大橋動力前15階頻率及振型特征序號不考慮自重考慮拉索垂度和成橋內力頻率振型特性(主要頻率振型特性(主要10.1374縱向漂移0.1394縱向漂移20.2354反對稱豎彎0.2335反對稱豎彎30.4373對稱豎彎0.4336對稱豎彎40.4

8、925反對稱豎彎0.4865反對稱豎彎50.5150反對稱側彎0.5150反對稱側彎60.6011對稱側彎0.6008對稱側彎70.6859對稱豎彎0.6815對稱豎彎80.8323反對稱豎彎0.8243反對稱豎彎90.8591橋面局部側彎0.8566橋面局部側彎100.8626橋面局部側彎0.8570橋面局部側彎110.8632對稱豎彎0.8606對稱豎彎120.9294對稱扭轉0.9287對稱扭轉130.9554反對稱豎彎0.9463反對稱豎彎140.9878對稱豎彎0.9792對稱豎彎150.9935反對稱扭轉0.9902反對稱扭轉橋梁結構65城市道橋與防洪2009年5月第5期 建立了某

9、大橋的有限元動力分析模型,對結構的動力特性進行了分析,結果表明:(1 斜拉索的垂度以及成橋狀態(tài)的內力狀態(tài)對該橋的整體動力特性影響很小;(2該橋的第一階振型為縱漂振型,對該大橋的抗震有利;(3橋面的扭轉頻率跟豎彎頻率比值高達4.22,說明大橋具有很好的氣動穩(wěn)定性。收稿日期:2008-12-02作者簡介:馬琳(1982-,女,吉林長春人,研究生,從事橋梁設計工作。摘要:該文通過有限元分析計算了兩種不同計算模式下的蓋梁內力。分析表明,當考慮立柱剛度影響時,蓋梁內力將進行二次分配,致使跨中正彎矩減小、支點負彎矩增大,隨著立柱與蓋梁的線剛度比的增大,此種效應越顯著。在工程實際應用中,由于工期緊張等因素,

10、當蓋梁與立柱的線剛度比大于2時,可采用簡化的雙懸臂簡支梁(連續(xù)梁圖式,但在支點及跨中截面,應適當提高。關鍵詞:蓋梁;有限元分析;線剛度比中圖分類號:U443.2文獻標識碼:A文章編號:1009-7716(200905-0066-03淺談柱式墩蓋梁的內力計算馬琳,趙興中(天津市政工程設計研究院,天津市30004570前言蓋梁作為簡支梁(板橋重要的承重構件,其承受著上部構造的恒載以及主梁傳遞給它的活載效應,并將這些荷載傳遞給橋墩。目前我國一級公路及高速公路四車道橋梁中常采用雙柱式墩臺或三柱式墩臺,隨著公路等級的提高、橋面寬度不斷加大,蓋梁的跨度也隨之增大,常規(guī)的設計計算方法已經存在一定的局限性;加

11、之在設計過程中,設計者們往往也容易忽視蓋梁構件的重要性,從而導致一些橋梁剛剛竣工便需要對蓋梁進行加固后才能投入使用,造成一定的經濟損失和不良社會反應。本文依托“塘承高速公路項目工程”對本工程項目中涉及到的部分蓋梁進行計算分析及探討,以供廣大橋梁設計人員參考。1計算方法目前對蓋梁計算圖式的選取取主要有兩種。(1雙懸臂簡支梁(連續(xù)梁計算圖式下蓋梁內力計算2雙柱式橋墩,當蓋梁剛度與柱的剛度比大于5時,為簡化計算而忽略節(jié)點不均衡彎矩的分配及傳遞,一般可按雙懸臂梁進行計算;對于多柱式的蓋梁剛可按連續(xù)梁計算,這些計算圖式可以快速解算出蓋梁控制截面內力(見圖1。(2懸臂剛構結構計算圖式下蓋梁內力計算在構造上

12、,柱的鋼筋伸入到蓋梁內,與蓋梁鋼筋綁扎在一起,因此蓋梁與柱呈剛構結構狀態(tài),本文采用“橋博V3.01有限元軟件”來進行蓋梁的內力計算(見圖2。蓋梁的線剛度為:i 1=E 1I 1/l 1(1立柱的線剛度為:i 2=E 2I 2/l 2(2蓋梁與立柱的線剛度比為:=i 1/i 2(32計算分析現(xiàn)行橋規(guī)1規(guī)定:墩臺蓋梁與柱應按剛構i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i i橋梁結構66Keywords:lighting design,lighting standard

13、,energy saving,earthing typeBRIDGES&STRUCTURESeExample of Comprehensive Anchorage Waterproof Treatment Engineering of Suspension Bridg!Ying Ganzhou(50 Abstract:The anchorage structure is the key to guarantee the integral structural safety of suspension bridge.The anchorage waterproofing is the i

14、mportant factor to guarantee the long-term safe use of the structure.The anchorage of the main bridge for Changjiang River No.2Bridge in Wanzhou is the compound anchorage structure.The most of anchorage chamber and the anchor block of this bridge are all placed below the normal water storage level o

15、f Three Gorges.The anchorage opening is limited from the waterside.The engineering geological condition is relatively worse.The waterproofing treatment is greatly difficult.Therefore,the comprehensive waterproofing treatment measure is taken.Keywords:suspension bridge,anchorage proofing,technical st

16、andard,integral scheme,engineering measureeCalculation Analysis and Design Discussion of25-m Continuous Plate Bridg!Li Chunxiao,Yang Junyi,Lin Tianqing,Li M inghong(54 Abstract:Taking the design of2-span3-span25-m post-tensioning continuous plate bridge as an example,the article analyzes the stress

17、characteristics of negative moment area at the top of continuous pier under the condition of a few piers,and contrasts and calculates this characteristic in detail.The relative contents can be referred for the design of the same bridges.Keywords:continuous plate bridge,analysis,designr Wang Hui(58 A

18、nalysis on M echanics Characteristic of Corrugated Steel Web PC Composite Box Girde!Abstract:Combined with the structural property of corrugated steel web composite box girder,the article systematically analyzes the axial deformation characteristic of corrugated steel web,the shear stress distribute

19、d characteristic of box girder and the torsion characteristic of the box girder.The result shows that the prestressed concrete box girder of corrugated steel web has the good stress feature and will be widely used in bridge engineering.Keywords:bridge engineering,PC composite box girder,corrugated s

20、teel web,mechanics characteristics Dai Pan,Hu Dalin(61 Analysis on Ultimate Bearing Capacity of Long Span Stone Arch Bridge!Abstract:Taking Danhe Bridge as an example,this paper determines the ultimate bearing capacity of masonry arch bridge by calculating ultimate bending moment of hinge point,and

21、considers the loading state of arch bridge and material characteristics comprehensively.It offers the new direction for researching the ultimate bearing capacity of masonry arch bridge,and the reference able for determining the ultimate bearing capacity of reinforced concrete arch bridge.Keywords:ar

22、ch bridge,ultimate bearing capacity,ultimate bending moment,limit eccentricitye Xu Yongsheng(64 Analysis of Dynamic Characteristic of a Three-pylon Cable-stayed Bridg!Abstract:A bridge is the first three-pylon cable-stayed bridge in China.Its structure is complicated.The article firstly sets up thre

23、e-main-beam model for the three-dimension finite element dynamic analysis,uses the large finite element general program ANSYS to analyze the dynamic characteristic of the bridge,and gives the influence of the deadweight effect of structure on the inherent dynamic characteristic.The result makes clea

24、r that the deadweight effect of this structure of cable-stayedbridge influences a little the integral inherent frequency.Keywords:three-pylon cable-stayed bridge,finite element general analysis program,dynamic charac-teristic,finite element modelmElementary Discussion on Internal Force Calculation o

25、f Column Pier Cover Bea!Ma Lin,Zhao Xingzhong(66 Abstract:The article calculates the internal forces of cover beams under two different calculation modes by the analysis of finite elements.The analysis makes clear that when considering the rigidity influence of upright column,the internal force of c

26、over beam will be secondarily distributed so as to make the positive moment in the span decrease and the negative moment support increase,and this kind of effect is more obvious with the increment of linear stiffness ratio of the upright column and cover beam.In the engineering practice and as the f

27、actors of the constructing period limit,it can be to use the simplified double-cantilever simple-support beam(continuous beampattern when the lin-ear stiffness ratio of the upright column and cover beam is larger than2,but it should be properly enhanced on the support and the section in the span.Key

28、words:cover beam,analysis of finite element,linear stiffness ratiotDesign of Bridge Structure of Kunming City Northeast Ring2Rebuilding Extension Projec!Liu Fang(69 Abstract:The article introduces the express system of Kunming M ain City Area Northeast Ring2 Rebuilding Extension Project including th

29、e structure type,anti-earthquake design,existing bridge re-building,durability design and engineering landscape design,which can be referred for the structural design of city elevated bridge projects.Keywords:bridge structure,rebuilding of existing bridges,anti-earthquake design,engineering land-sca

30、petDesign of Pile Foundation Underpinning Work of Expressway Elevated Bridge of Guangzhou Airpor!Liu Liying,Wei Lixin,Liu Fang(75 Abstract:Taking the foundation underpinning of an existing bridge pier in the expressway of Guangzhou Airport as an example,the article explains the key techniques in the design scheme,con-struction process and design construction of the pile foundation underpinning of the elevated bridge.The article combines