鋁合金人行天橋設(shè)計(jì)分析要點(diǎn)

1、2012年3月第3期城市道橋與防洪0前言鋁合金材料以其較高的彈性模量和良好的防腐性能在土木行業(yè)中得到越來越廣泛的應(yīng)用。1933年,美國第一次將鋁合金應(yīng)用在橋梁中。目前在歐美等發(fā)達(dá)國家鋁合金橋梁已經(jīng)發(fā)展得比較成熟,但是國內(nèi)的鋁合金橋梁研究還處于起步階段,2006年建成的杭州市慶春路鋁合金人行天橋是目前中國第一座全鋁合金橋梁。鋁合金材料與鋼材有著較大的材料特性差異:首先是其材料的密度,鋁合金因密度小而自重小;其次是材料的彈性模量與鋼相比較小(雖然其極限強(qiáng)度和Q235相當(dāng)。因此,鋁合金橋在施工使用過程中存在諸多問題。例如,杭州市慶春路人行天橋是國內(nèi)第一座鋁合金橋梁,存在問題如下:在滿人荷載作用下?lián)隙?/p>

2、過大,自振頻率和荷載作用下的頻率相比變化較大。本文主要針對(duì)上述方面進(jìn)行研究,分析出現(xiàn)這些現(xiàn)象的本質(zhì)原因,以及提出解決問題的方案。本文依據(jù)杭州復(fù)興路人行天橋建立模型,利用ANSYS 有限元軟件輔助分析計(jì)算,以期能為將來我國設(shè)計(jì)建設(shè)更多的鋁合金橋作參考和借鑒。1橋梁概況杭州市復(fù)興路人行天橋?yàn)槿玟X合金梁,跨徑布置為26.64m+19m+15.4m ,橋梁平面布置見圖1。橋面寬度4.8m ,其中通行橋面寬4.5m (見圖2。天橋橋跨采用中承式鋁制主桁結(jié)構(gòu),橋面離主桁上弦桿1.265m 。主桁之間采用橫向桁架連接,橫向桁架上弦為橋面板的支承結(jié)構(gòu),橋面與上弦之間采用焊接互相連接。橋面為雙層鋁合金板結(jié)構(gòu),

3、在上下板之間用鋁制豎向以及斜腹板聯(lián)系。圖3為橋面板結(jié)構(gòu)圖。計(jì)算分析的范圍主要為上部結(jié)構(gòu),本次僅針對(duì)最大跨徑26.64m 簡(jiǎn)支梁進(jìn)行分析,其余同理。通過詳細(xì)的計(jì)算分析,驗(yàn)算結(jié)構(gòu)的撓度、自振頻率。(1撓度驗(yàn)算:人群荷載作用下最大撓度不大于跨度的1/400。(2振動(dòng)特性:計(jì)算結(jié)構(gòu)的自振頻率,保證橋梁在1kN/m 2活載下豎向振動(dòng)頻率大于3.0Hz 。2計(jì)算模型采用通用程序ANSYS 對(duì)結(jié)構(gòu)進(jìn)行彈塑性極限強(qiáng)度的驗(yàn)算,計(jì)算采用beam188單元模擬各上、下弦桿及豎斜腹桿,上下弦及斜豎腹桿按全截面取值,橋面采用等厚橋面板。26.64m 簡(jiǎn)支梁計(jì)算采用的有限元模型如圖4所示。根據(jù)相關(guān)資料,極限承載力分析中采

4、用了圖5所示的應(yīng)力-應(yīng)變關(guān)系。3分析計(jì)算3.1結(jié)構(gòu)自振頻率驗(yàn)算結(jié)果自振頻率按是否考慮人群荷載分兩種情況:(1恒載下的振動(dòng)頻率;(2恒載+1.0kN/m 2的人群荷載(橋面寬度按4.8m 計(jì)算。計(jì)算結(jié)果顯示,在恒載下豎向振動(dòng)自振頻率為3.91Hz ,在恒載+1.0kN/m 2的人群荷載下自振頻率為3.88Hz 。結(jié)果如表1所示,兩種情形的振型圖分別參見圖6、圖7。結(jié)果表明,兩種狀態(tài)下結(jié)構(gòu)的豎向自振頻率均超過了3.0Hz ,結(jié)構(gòu)的自振頻率能滿足規(guī)范要求。3.2結(jié)構(gòu)剛度驗(yàn)算在活載5kN/m 2作用下,跨中最大撓度為摘要:鋁合金人行天橋在全國范圍內(nèi)已建成多座,但由于鋁合金材料自身的特點(diǎn),在設(shè)計(jì)過程中應(yīng)

5、注重多方面的復(fù)核。依據(jù)杭州復(fù)興路人行天橋建立模型,利用ANSYS 有限元軟件輔助,就鋁合金人行天橋的自振頻率及穩(wěn)定性進(jìn)行重點(diǎn)分析計(jì)算,以期為以后的應(yīng)用發(fā)展做出貢獻(xiàn)。關(guān)鍵詞:人行天橋;鋁合金;自振頻率;彈性模量;穩(wěn)定性中圖分類號(hào):U448.11文獻(xiàn)標(biāo)識(shí)碼:B文章編號(hào):1009-7716(201203-0067-03收稿日期:2011-11-24作者簡(jiǎn)介:程子健(1980-,男,內(nèi)蒙古人,工程師,從事路橋設(shè)計(jì)工作。程子健,杜曉燕(蘇州市慧杰工程設(shè)計(jì)有限公司,江蘇蘇州215011鋁合金人行天橋設(shè)計(jì)分析要點(diǎn)橋梁結(jié)構(gòu)67城市道橋與防洪2012年3月第3期49.50mm ,桁架下弦的撓度為46.29mm

6、,為跨度的1/434和1/470,滿足要求。活載作用下的結(jié)構(gòu)變形見圖8所示。4結(jié)論根據(jù)以上計(jì)算分析:(1鋁合金人行天橋的震動(dòng)頻率變化幅度較鋼圖1杭州復(fù)興路人行天橋橋型平面布置圖圖2主橋橫斷面圖(單位:cm 圖3橋面板結(jié)構(gòu)圖圖5鋁材的應(yīng)力應(yīng)變本構(gòu)關(guān)系圖4彈塑性極限強(qiáng)度的有限元模型表1自振頻率結(jié)果振型序恒載恒載+1.0kN/m 2頻率/Hz 振型頻率/Hz 振型1 3.86一階側(cè)彎+扭轉(zhuǎn)3.86一階側(cè)彎+扭轉(zhuǎn)2 3.91一階豎彎 3.88一階豎彎振型參照?qǐng)D圖6圖7橋梁結(jié)構(gòu)68橋梁結(jié)構(gòu)69 2012年3月第3期城市道橋與防洪圖6恒載作用下的結(jié)構(gòu)振型圖圖7恒載+1.0kN/m2活載作用下的結(jié)構(gòu)振型圖(

7、下轉(zhuǎn)第78頁城市道橋與防洪2012年3月第3期材略大,但是人行荷載作用下可滿足安全要求;(2鋁合金材料的彈性模量小,撓度大,但是在跨徑不大的情況下,由于鋁合金材料自重小,撓度反而在安全范圍內(nèi),可滿足使用要求。參考文獻(xiàn):1姚常華,楊建國,吳利權(quán).鋁合金結(jié)構(gòu)橋梁的應(yīng)用現(xiàn)狀、前景及發(fā)展建議J.鋼結(jié)構(gòu),2009(7:1-5.2陳寶春,楊亞林,孫潮.鋁橋的應(yīng)用與發(fā)展J.世界橋梁,2004(2:68-70.3徐業(yè)飛.鋁合金人行天橋結(jié)構(gòu)分析D.杭州:浙江大學(xué),2007.4張錚.鋁合金結(jié)構(gòu)壓彎構(gòu)件穩(wěn)定承載力研究D.上海:同濟(jì)大學(xué),2006.5王春生,袁卓亞,高珊,葉禮鋒.鋁合金在民用與軍用橋梁中的應(yīng)用J.世界

8、橋梁,2007(3:9-12.6陳海濱.桁式鋼管混凝土拱橋極限承載能力研究D.杭州:浙江大學(xué),2006.7靳欣華,陸逵,魯宏.上海某鋁合金人行天橋荷載試驗(yàn)分析J.城市道橋與防洪,2009(2:33-35.8竺豪立,程曉東.鋁合金人行天橋的特性及設(shè)計(jì)對(duì)策J.建筑,2007(24:44-45.9黃勇,許雷挺,李海沙.運(yùn)營中鋁合金人行天橋的監(jiān)測(cè)J.建筑施工,2010(12:1250-1252.圖826.64m 簡(jiǎn)支梁滿載作用下的結(jié)構(gòu)變形圖(單位:mm寬0.5m ,為使橫梁施工方便,索力傳遞均勻,以錨點(diǎn)為中心,每側(cè)分布0.25m 寬度。(5橋頭燈柱設(shè)計(jì)由于空間及地形限制,單獨(dú)設(shè)立基礎(chǔ)修建燈柱比較困難。

9、因此橋頭燈柱設(shè)置在橋臺(tái)背墻上面,分列護(hù)欄外側(cè)。燈柱為鋼筋混凝土結(jié)構(gòu),柱高3.5m ,柱截面為圓形,直徑0.3m ,柱體主筋深入背墻里面,以背墻為基礎(chǔ)。背墻寬度0.4m ,燈柱側(cè)邊距背墻外緣均為5cm 。這樣做,既保證了燈柱有堅(jiān)實(shí)的基礎(chǔ),又節(jié)省了空間。(6結(jié)構(gòu)計(jì)算本次結(jié)構(gòu)計(jì)算按城市專用人行橋計(jì)算,人群荷載取4.23kN/m 2設(shè)計(jì)。計(jì)算荷載包括恒載:結(jié)構(gòu)自重、人行道鋪裝、護(hù)欄、燈飾、燈柱等;活載:溫度力、風(fēng)力、流水壓力、混凝土收縮徐變等。a.箱梁設(shè)計(jì)按A 類預(yù)應(yīng)力混凝土構(gòu)件控制;b.主塔及下部結(jié)構(gòu)按照普通鋼筋混凝土構(gòu)件控制;c.混凝土及預(yù)應(yīng)力鋼束、拉索結(jié)構(gòu)按公路鋼筋混凝土及預(yù)應(yīng)力混凝土橋涵設(shè)計(jì)規(guī)

10、范(JTGD62-2004檢算各項(xiàng)指標(biāo);d.鋼結(jié)構(gòu)部件按公路橋涵鋼結(jié)構(gòu)及木結(jié)構(gòu)設(shè)計(jì)規(guī)范(JTJ 025-86檢算各項(xiàng)指標(biāo)。4結(jié)論綜合以上過程,該項(xiàng)目具備了下面4個(gè)特征:(1統(tǒng)一和諧多樣統(tǒng)一是形式美的一種高級(jí)形態(tài),也是創(chuàng)造形式美的最高要求。從該項(xiàng)目來講,橋梁周圍環(huán)境復(fù)雜多樣,既有姿態(tài)萬千的建筑,又有形態(tài)各異的橋梁。該項(xiàng)目的加入,不僅與岸上蓮花燈柱相呼應(yīng),也增加了橋梁組成的多樣性,為周圍環(huán)境增添了新的風(fēng)景。總體來看,橋梁建筑自身及周邊環(huán)境成為有機(jī)的整體,而不是雜亂無章,支離破碎。(2均衡穩(wěn)定中國美學(xué)家朱光潛先生曾說:“美的形體無論如何復(fù)雜,大概含有一個(gè)基本原則,就是平衡和勻稱。”該項(xiàng)目對(duì)稱均衡,通

11、過它的外在形象所展示的體量就有一種均衡穩(wěn)定感。整體結(jié)構(gòu)具有穩(wěn)重、莊嚴(yán)之美,而搭配的燈飾和護(hù)欄又有靈活、翔動(dòng)的美。(3比例協(xié)調(diào)比例在建筑藝術(shù)上是非常重要的。該橋塔高、柱徑、燈飾大小經(jīng)過多次比較篩選,在眾多方案中選出合適比例的配合,再通過不同顏色之間的搭配,收到了良好的效果。(4特征鮮明該橋建筑風(fēng)格時(shí)代感強(qiáng)烈,配飾融入了民族地域風(fēng)格。橋型簡(jiǎn)潔明快、輕巧纖細(xì)、連續(xù)流暢、融入自然。參考文獻(xiàn):1范立礎(chǔ).橋梁工程(上冊(cè)M.北京:人民交通出版社,2001.2和丕壯.橋梁美學(xué)M.北京:人民交通出版社,1999.3許秀平,彭衛(wèi).橋梁建筑美學(xué)特征與結(jié)構(gòu)設(shè)計(jì)J.金華職業(yè)技術(shù)學(xué)院學(xué)報(bào),2004(3:29-32.(上接

12、第69頁!橋梁結(jié)構(gòu)78theoretical calculation mode,and the deck vibration frequency satisfies the rule of simplified calculation formula.The dynamical characteristic of this bridge is excellent.Keywords:flying-swallow concrete filled steel tube arch bridge,finite element,natural vibration characteristic,modal

13、analysisAnalysis on Unconstrained Length of Externally Prestressed Cable!Wang Shousheng(54 Abstract:The externally prestressed cable among the turning blocks(anchoring endmay produce the vibration independently from the girder.If its frequency is closing to the inherent frequency of the girder, the

14、sympathetic vibration will cause.It is not the good solving method to change the section characteristic of girder or the normal using stress of external cable when the frequencies are closing.The ideal method can yet be regarded in the aspects of economy,effect and feasibility to change the restrict

15、ed length of the external cable so as to change its inherent frequency.The unconstrained length of non-lateral support for external cable should not be over long.Based on the common bridge frequency and the using condition of steel strand in China,the external cable can be controlled within12m.In th

16、is way,the natural vibration frequencies of bridge and external cable will stagger,and also avoid the sympathetic vibration.Keywords:external prestressing,sympathetic vibration,frequency,unconstrained lengthThree-dimension Finite Element Simulation Analysis on Full-pile Foundation of Bridge Based on

17、 ANSYS!Chen Hui(58 Abstract:The bridge foundation is an important composed part of bridge structural engineering.It bears the weight of the upper structure and the external force,and conveys them to the subgrade.Based on the finite element software ANSYS,the article carries out the three-dimension s

18、imulation analysis on the full-pile foundation of bridge,including the constitution design,modeling and network division of the full-pile foundation of bridge,and the stress analysis under the dead weight and vehicle live load.Keywords:bridge structure,full-pile foundation,finite element analysis,AN

19、SYSDesign Method of Long-span Continuous Steel Box Beam!Dai Shaoxiong,Xie Bin(61 Abstract:The article introduces the design and construction methods of long-span continuous steel box beam for the overpass bridge in the west longitudinal contact line of expressway,systematically describes the design

20、process,analyzes the key nodes in detail,and puts forward the feasible design method,which can be referred for the construction of the similar bridges.Keywords:long-span continuous steel box beam,steel deck slab,shear lag,pivot structureCrossbeam Design of Variable Section Pre-stressed Concrete Cont

21、inuous Box Beam Bridge Zhou Haixia(64 Abstract:The article analyzes the crossbeam constitution,calculation model and reinforcement design of variable section pre-stressed concrete continuous box beam bridge by the engineering cases.Keywords:variable section pre-stressed concrete continuous box beam,

22、crossbeam,constitution,model, reinforcementDesign and Analysis Gist of Aluminium Alloy Pedestrian Overpass!Cheng Zijian,Du Xiaoyan(67 Abstract:Many aluminium alloy pedestrian overpasses have been built in China.However,the recheck has to been focused in many aspects in the course of design because o

23、f the characteristics of aluminium alloy material.Based on the model built for Fuxing Road Pedestrian Overpass of Hangzhou,the natural vibration frequency and the stability of aluminium alloy pedestrian overpasses are focused on analysis and calculation by utilizing the ANSYS finite element software

24、 so to make the contribution for the application and development of its future.Keywords: pedestrian overpass, aluminium alloy, natural vibration frequency, elastic modulus, stability Design of 64-m Curve Steel Truss Beam ! Peng Min (70 Abstract: The article introduces the design of railway steel tru

25、ss bridge, and focuses on analysis of whether or not the deck concrete is concerned with the stress of structure system and the influence of curvature on the stress of the inner and outer lateral rods, which can be referred for the design of the same bridge. Keywords: curve steel truss beam, railway

26、 bridge, structural calculation, design Analysis on Design and Calculation of Overall Structure for Datong Beidou Bridge ! ! Chen Hefeng, Wu Yongxian, Wang Shuo (73 Abstract: The article introduces the structure design and construction schemes of Beidu Bridge, which is an important landscape bridge

27、connecting the old and new city areas in Datong City of Shanxi province. Its main bridge is a 140-m single-span through steel truss arch bridge with the design of unilateral double booms. Through the static and stability calculation analysis, and the three-dimensional analysis of partial arch foot,

28、the rationality and security of this design scheme are verified, which can be referred for the design of this kind of bridges. Keywords: steel truss arch bridge, structure design, structural calculation analysis, Datong City Design of Single-pylon Single-plane Pedestrian Landscape Cable-stayed Bridg

29、e in Baoting County of Hainan ! Liu Yaozong (76 Abstract: The article introduces the design of a single-pylon single-plane pedestrian landscape cable-stayed bridge on Baocheng East River in Baoting County of Hainan, and discusses how to deal with the harmonious unification of the structure and the l

30、andscape. Keywords: single pylon, landscape, cable-stayed bridge, design Discussion on Design of River Landscape Bridge ! Liu Xiangyang, Li Baoyuan (79 Abstract: With the advancement of the society and the enhancement of the people living level, the s river taken as an important carrier of urban landscape is more and more concerned by the people. Many cities, such as Beijing, Shanghai, Hangzhou and etc. all actively se