大跨度門式起重機(jī)剛性支腿對結(jié)構(gòu)剛度的影響分析外文文獻(xiàn)翻譯、中英文翻譯、外文翻譯
大跨度門式起重機(jī)剛性支腿對結(jié)構(gòu)剛度的影響分析外文文獻(xiàn)翻譯、中英文翻譯、外文翻譯,跨度,起重機(jī),剛性,結(jié)構(gòu),剛度,影響,分析,外文,文獻(xiàn),翻譯,中英文
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大跨度門式起重機(jī)剛性支腿對結(jié)構(gòu)剛度的影響分析
官保華，甄圣威，曾慶敦
( 華南理工大學(xué) 土木與交通學(xué)院，廣東 廣州 510640)
摘要: 利用有限元軟件對某公司設(shè)計(jì)的 83 m 跨度 A5 型門式起重機(jī)的剛度進(jìn)行分析，求得的主梁撓度超出《通用門式起重機(jī)》( GB/ T14406 － 93) 的規(guī)定，且結(jié)構(gòu)產(chǎn)生較大的側(cè)向位移． 通過對剛性支腿結(jié)構(gòu)設(shè)計(jì)進(jìn)行修改，使得主梁最大撓度下降 69. 2% ，側(cè)向位移下降 62. 6% ．
關(guān)鍵詞: 門式起重機(jī); 剛性支腿; 吊車梁; 側(cè)偏
中圖分類號(hào): TU32 文獻(xiàn)標(biāo)志碼: A 文章編號(hào): 1007-7162( 2011) 04-0083-04
隨著船海工業(yè)的發(fā)展，大跨度、大噸位吊車的應(yīng)用越來越廣泛，以滿足造船業(yè)生產(chǎn)的靈活性和建造大型船只時(shí)對吊裝噸位的需求． 箱型梁有剛度大和抗偏扭性能好等諸多優(yōu)點(diǎn)［1］，使之廣泛運(yùn)用于大跨度吊車梁中． 由于吊車梁對容許撓度有嚴(yán)格的規(guī)定［2 － 3］，超出此規(guī)定不但會(huì)影響吊車的正常使用，且由于主梁振幅較大，將大大降低疲勞使用壽命，所以對主梁的剛度驗(yàn)算顯得尤為必要． 通過對文獻(xiàn)［4 － 8］的調(diào)研發(fā)現(xiàn)，對門吊鮮有關(guān)于側(cè)向剛度的研究報(bào)道，僅文獻(xiàn)［8］提及了造船門式起重機(jī)門架反變位技術(shù)，但未進(jìn)行深入的理論研究． 由于大跨度門吊多采用一剛一柔兩條支腿的形式，由結(jié)構(gòu)力學(xué)［9］分析可以發(fā)現(xiàn)，這種結(jié)構(gòu)在受豎向力作用后必然會(huì)發(fā)生側(cè)偏，這種側(cè)偏對結(jié)構(gòu)是非常不利的，這一點(diǎn)將在后面的論述中詳細(xì)說明． 在發(fā)現(xiàn)設(shè)計(jì)不滿足規(guī)范要求后就盲目地加大結(jié)構(gòu)尺寸、提高結(jié)構(gòu)剛度的做法顯然是不明智的，也是不經(jīng)濟(jì)的，應(yīng)首先考慮通過結(jié)構(gòu)上的優(yōu)化改造來達(dá)到預(yù)期效果． 本文通過對門式起重機(jī)剛性支腿的設(shè)計(jì)改造，在不增加建造成本，不改變門吊凈空的基礎(chǔ)上，不但使主梁的剛度滿足規(guī)范要求，而且極其明顯地改變了門式起重機(jī)側(cè)偏位移較大的情況，充分說明了剛性支腿在門式起重機(jī)結(jié)構(gòu)上所起的作用．
1 門式起重機(jī)的結(jié)構(gòu)形式
本文以某公司設(shè)計(jì)的 ME150 + 110 /25 － 83A5 型門式起重機(jī)為例，設(shè)計(jì)最大起重量 200 t，主梁跨度 83 m，高達(dá) 55 m，梁高 5 m 且由雙梁構(gòu)成． 根據(jù)《起重機(jī)設(shè)計(jì)手冊》［10］，當(dāng)梁跨度大于 30 m 時(shí)，采用一個(gè)剛性支腿一個(gè)柔性支腿相結(jié)合的結(jié)構(gòu)形式，可以減小因超靜定產(chǎn)生的水平支反力，故其中一側(cè)可設(shè)置為剛性支腿，與水平梁采用固定式連接; 另一側(cè)設(shè)置為柔性支腿，采用球鉸與主梁連接． 剛性支腿下端寬 1. 25 m，上端寬 5 m． 其結(jié)構(gòu)簡圖如圖 1 所示．
圖 1 門式起重機(jī)原始設(shè)計(jì)示意圖
由結(jié)構(gòu)力學(xué)的分析易知，圖 1 所示結(jié)構(gòu)在主梁受到豎向荷載后，主梁除會(huì)產(chǎn)生向下?lián)锨酝猓€會(huì) 產(chǎn)生向右的沿著梁軸向的側(cè)偏． 小量的側(cè)偏是允許的，但當(dāng)側(cè)偏較大時(shí)，不但會(huì)影響門吊的正常使用， 而且存在安全隱患，甚至可能由于傾斜過大導(dǎo)致門 吊的整體傾覆．
2 有限元模型及計(jì)算結(jié)果
本文對圖 1 所示龍門吊車結(jié)構(gòu)使用通用有限元軟件 ANSYS，依據(jù)原設(shè)計(jì)圖紙建立整體模型． 對組成梁與支腿的各板件選用 shell63 單元，各加勁肋和軌道則選用 beam188 單元． 不考慮細(xì)部的螺栓連結(jié)和外圍輔助配套設(shè)施( 如欄桿、扶梯等) 對結(jié)構(gòu)響，建立有限元模型如圖 2 所示
圖 2 龍門吊車結(jié)構(gòu)的有限元模型
吊車的額定起重量為 200 t，小車分上下兩部，上部小車自重 40 t，下部小車自重 45 t． 主梁鋼材采用 Q345B，兩支腿鋼材均采用 Q235B．
通過結(jié)構(gòu)力學(xué)［9］中的影響線理論求得主梁撓度的最不利載荷位置如圖 3 所示． 荷載則通過計(jì)算出的輪壓以集中力的形式加到軌道位置上．
下小車輪壓:
P1 = αβγQP1max = 1. 05 × 1. 13 × 1. 4 × 182 =302. 32( kN) ;
上小車輪壓:
P2 = αβγQP2max = 1. 05 × 1. 13 × 1. 4 × 175 × 2 =81. 4( kN) ．
其中，根據(jù)規(guī)范［3］，取動(dòng)力系數(shù) α = 1. 05，對于箱形結(jié)構(gòu)，荷載增大系數(shù) β = 1. 13，吊車豎向荷載分項(xiàng)系數(shù)γQ = 1. 4． P1max 、P2max 是下、上小車的主鉤輪壓．
圖 3 主梁撓度最不利荷載布置圖
在結(jié)構(gòu)自重和吊車滿載起吊的條件下，同時(shí)考
慮最不利工況，計(jì)算結(jié)果如下:
主梁最大撓度( 如圖 4 所示) 為
δ = 260. 9 mm． ( 1)
主梁沿軸向的側(cè)偏位移( 如圖 5 所示) 為
U = 492. 8 mm． ( 2)
根據(jù)《通用門式起重機(jī)》( GB / T14406 － 93 ) ［2］ 第 4. 2. 8 條，起重機(jī)的靜態(tài)剛性規(guī)定為: 對于 A5 型起重機(jī)，起重機(jī)的額定起重量與小車自重在主梁跨中( 或撓度最大處) 引起的垂直靜撓度不應(yīng)大于
S /800，其中 S 為起重機(jī)主梁的跨度．
圖 4 主梁撓度圖
圖 5 吊車側(cè)向位移圖
由此可知，該吊車梁的許用垂直靜撓度為
［δ］= 83 000 mm /800 = 103. 75 mm， ( 3)
通過如下比較:
δ = 260. 9 mm ＞［δ］= 103. 75 mm． ( 4)
可見，主梁撓度已遠(yuǎn)超過了《通用門式起重機(jī)》的靜態(tài)剛性規(guī)定．
通過對有限元計(jì)算的分析發(fā)現(xiàn)，門式吊機(jī)頂部， 即主梁發(fā)生了多達(dá) 0. 49 m 的沿梁軸向的側(cè)向位移， 為了了解這個(gè)位移帶來的危害，下面將先分析如此 大位移產(chǎn)生的原因．
3 計(jì)算結(jié)果分析
前面已經(jīng)介紹過，對于圖 1 所示的結(jié)構(gòu)，在主梁受到豎向荷載作用時(shí)，結(jié)構(gòu)必然會(huì)產(chǎn)生向右的側(cè)偏， 這是由它的結(jié)構(gòu)形式所決定的．
此外，觀察圖 1 中剛性支腿，其結(jié)構(gòu)形式為非對稱結(jié)構(gòu)，其左側(cè)邊線為垂直地面，而右側(cè)邊線為斜直線． 剛性支腿上表面與主梁用螺栓及電焊連接，在受載后接觸面上內(nèi)力可近似看成均勻分布的面載，方向豎直向下; 下表面受到的是支座反力，由于吊車輪與軌道接觸面積較小，故可將其視為集中荷載，如圖
6 所示． 考慮剛性支腿的結(jié)構(gòu)形式，這兩個(gè)力的合力并非在同一條直線上，在這兩個(gè)荷載作用下，結(jié)構(gòu)會(huì)產(chǎn)生一個(gè)順時(shí)針的力偶，如圖 6 中順時(shí)針旋轉(zhuǎn)箭頭所示．
顯然，當(dāng)僅有這個(gè)順時(shí)針彎矩存在時(shí)，主梁會(huì)產(chǎn) 生一個(gè)向右的側(cè)向位移和向下的彎曲，分別如圖 6 中水平和豎直箭頭所示，根據(jù)結(jié)構(gòu)力學(xué)的疊加原理， 它將另外增加主梁在正常工作時(shí)的側(cè)偏和跨中撓 度． 因此這個(gè)彎矩的存在對結(jié)構(gòu)是不利的，以下稱其 為“不利彎矩”，故最好能消除這個(gè)彎矩對結(jié)構(gòu)的不 利影響．
圖 6 吊車原設(shè)計(jì)受力分析簡圖
在本文的實(shí)例中，由于這個(gè)不利彎矩的存在，一方面使得主梁跨中撓度超過規(guī)范要求; 另一方面?zhèn)绕慷噙_(dá) 0. 49 m，在正常使用過程中表現(xiàn)為很大幅度的晃動(dòng)，起吊物將隨其晃動(dòng)，因此當(dāng)?shù)踯嚪畔缕鸬跷飼r(shí)難以實(shí)現(xiàn)精確定位． 而造船用起重機(jī)常常需要將起吊的構(gòu)件或設(shè)備精確地吊放在安裝位置，以備焊接或栓緊． 因此，晃動(dòng)對吊車的正常工作是十分不利的．
同時(shí)，此不利彎矩增加了剛性支腿與主梁連接處螺栓的應(yīng)力水平，加之吊車晃動(dòng)的影響，將明顯降低螺栓的疲勞壽命．
由于結(jié)構(gòu)存在上述種種問題，因此需對結(jié)構(gòu)的設(shè)計(jì)進(jìn)行修改．
4 設(shè)計(jì)修改
第 2 節(jié)通過有限元計(jì)算發(fā)現(xiàn)，某公司原設(shè)計(jì)的大型門式起重機(jī)存在跨中撓度和側(cè)偏過大的問題， 并在第 3 節(jié)中分析了其產(chǎn)生的機(jī)理，得出了必須修改設(shè)計(jì)的結(jié)論．
加大結(jié)構(gòu)尺寸，提高結(jié)構(gòu)剛度雖可立竿見影，但會(huì)造成資源的浪費(fèi)、工期的延長，考慮到生產(chǎn)的商業(yè)性和結(jié)構(gòu)設(shè)計(jì)中“安全可靠，經(jīng)濟(jì)合理”的基本原則，這種方法在非必要的情況下不應(yīng)采取，而應(yīng)優(yōu)先考慮結(jié)構(gòu)優(yōu)化．
由第 3 節(jié)的分析發(fā)現(xiàn)，不利彎矩的存在增加了結(jié)構(gòu)跨中撓度和側(cè)偏量，故只需消除不利彎矩的作用便可起到改變結(jié)構(gòu)性能的作用． 不利彎矩是由剛性支腿的擺放方式不合理引起的，因此改變剛性支腿的擺放方式將是行之有效的方法，不但可以消除不利彎矩的影響，甚至將其不利的影響變?yōu)橛欣?，進(jìn)一步減小主梁原本的撓度和側(cè)偏．
綜上所述，參照文獻(xiàn)［8］的思路，將翻轉(zhuǎn)剛性支 腿的擺放位置如圖 7 所示，在剛性支腿上部面力和下部集中力的合力作用下，產(chǎn)生一個(gè)逆時(shí)針的力偶， 如圖 7 中逆時(shí)針旋轉(zhuǎn)箭頭所示，與圖 6 中的力偶方向恰恰相反． 在這個(gè)力偶的單獨(dú)作用下，一方面，主梁將產(chǎn)生向上的撓曲，如圖 7 中向上的箭頭所示，可以抵消一部分正常工作時(shí)主梁的下?lián)? 另一方面，主梁會(huì)產(chǎn)生向左的沿梁軸向的側(cè)偏，如圖 7 中水平向左的箭頭所示，可以抵消部分的結(jié)構(gòu)固有側(cè)偏． 故不利彎矩在經(jīng)過改造后可以變?yōu)閷Y(jié)構(gòu)有利的彎矩．
圖 7 吊車結(jié)構(gòu)優(yōu)化受力圖
為了驗(yàn)證結(jié)構(gòu)優(yōu)化后的效果，在有限元軟件中按上述思想修改計(jì)算模型，只需按圖 7 修改剛性支腿的擺放方式，其他參數(shù)均保持不變． 經(jīng)計(jì)算得到主梁跨中撓度與側(cè)偏量如下:
主梁跨中撓度為
δ' = 80. 27 mm ＜ 103. 75 mm，
主梁跨中撓度下降了 69. 2% ，滿足《通用門式起重機(jī)》GB / T14406 － 93［2］中對主梁剛度的要求． 而且有較大的剛度富余，仍有較大可優(yōu)化的空間．
主梁的側(cè)偏位移為
U' = 184 mm，
相對于優(yōu)化前的 492. 8 mm 下降了 62. 6% ，效果十
分明顯．
根據(jù)上述的分析和計(jì)算結(jié)果告知起重機(jī)生產(chǎn)廠家，廠家同意按上述結(jié)構(gòu)優(yōu)化方案修改原 ME150 + 110 /25 － 83A5 型門式起重機(jī)的設(shè)計(jì)并按修改后的設(shè)計(jì)生產(chǎn)起重機(jī)． 廣東某船務(wù)工程有限公司購買了多臺(tái)經(jīng)結(jié)構(gòu)優(yōu)化后的此類吊車，迄今為止一直安全穩(wěn)定運(yùn)營，取得了良好的經(jīng)濟(jì)和社會(huì)效益．
5.結(jié)論
本文通過通用有限元軟件 ANSYS 對某公司設(shè)計(jì)的 ME150 + 110 /25 － 83A5 型門式起重機(jī)進(jìn)行整體分析，發(fā)現(xiàn)該設(shè)計(jì)存在如下問題:
首先，主梁跨中撓度過大，剛度不能滿足規(guī)范要求; 其次，結(jié)構(gòu)在受力時(shí)，主梁在其軸線方向上有較大的側(cè)偏，影響結(jié)構(gòu)的穩(wěn)定．
通過對吊車結(jié)構(gòu)產(chǎn)生側(cè)偏的機(jī)理分析，得出了剛性支腿不合理的擺放方式是造成結(jié)構(gòu)側(cè)偏的主要原因． 剛性支腿的合理擺放會(huì)產(chǎn)生一個(gè)有利于結(jié)構(gòu)的彎矩，不但可以減小主梁的跨中撓度，而且可以減小結(jié)構(gòu)在受載后的固有側(cè)偏位移，充分體現(xiàn)了剛性支腿在門式起重機(jī)結(jié)構(gòu)中所起的作用．
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Analysis of the Influence of Long-span Gantry Cranes' Rigid Legs on Structure Stiffness
Gan Bao-hua，Zhen Sheng-wei，Zeng Qing-dun
( School of Civil Engineering and Transportation，South China University of Technology，Guangzhou 510640，China)
Abstract: Finite software was used to research the A5 Gantry Cranes designed by a company，whose span was 83
m． The research results indicate that the deflection of girder oversteps the formulations of General purpose gantry cranes ( GB / T14406-93) ，coupled with a big lateral displacement． After a simple modification of the structure de- sign for the rigid legs，the deflection of girder and the lateral displacement have reduced by 69． 2% and 62． 6% ， respectively．
Key words: gantry crane; rigid leg; crane beam; laterodeviation
Analysis on the Influence of Rigid Legs of Long-span Gantry Crane on Structural Stiffness
Guan Baohua，Saint Vincent Yan，Chung On
( School of Civil Engineering and Communications, South China University of Technology, Guangzhou, Guangdong510640)
Summary: Using finite element software to design a company83 mSpan spanA5Stiffness analysis of type gantry crane，The deflection of the main beam obtained exceeds《General gantry crane》( G B / T 14406 － 93)Provisions，And the structure produces large lateral displacement．Modification of Rigid Leg Structure，The maximum deflection of the main beam decreases69. 2% ，Lateral displacement62. 6% ．
Key words: Gantry crane; Rigid leg; Crane beam; Side deviation
Middle Chart Classification Number:TU32 Document symbol codeA :1 Number of articles:1007-7162(2011)04-0083-04
With the development of ship-sea industry, large-span and large-tonnage cranes are more and more widely used to meet the flexibility of shipbuilding industry and the demand for hoisting tonnage when building large ships． The box girder has many advantages such as high stiffness and good deflection resistance［1］，It is widely used in large span crane beams． Because the crane beam has strict requirements for allowable deflection［2 － 3］，Exceeding this regulation will not only affect the normal use of the crane，Because of the large amplitude of the main beam, the fatigue life will be greatly reduced, so it is necessary to check the stiffness of the main beam． Adoption of the text－ It is found that the lateral stiffness of the door crane is reported,Only literature[8] has mentioned the reverse displacement technology of gantry crane in shipbuilding, but has not carried on the thorough theoretical research． Because the long span door crane is mostly in the form of one rigid and one flexible two legs, the structure mechanics［9］It can be found that this kind of structure will inevitably have side deviation after being subjected to vertical force, which is very unfavorable to the structure, which will be explained in detail in the following discussion． It is obviously unwise and uneconomical to blindly increase the size and stiffness of the structure after finding that the design does not meet the requirements of the code, so we should first consider the optimal transformation of the structure to achieve the desired results． In this paper, through the design and modification of the rigid leg of the gantry crane, on the basis of not increasing the construction cost and not changing the clearance of the gantry crane, the stiffness of the main beam not only meets the requirements of the code, but also obviously changes the large side displacement of the gantry crane. The function of the rigid leg in the gantry crane structure is fully explained．
4 Structure of gantry crane
This article is designed by a companyME150+110/25-83 A5Example of type gantry crane，Design Maximum Weight200 t,Main girder span83 m,Up to55 m,Beam height5 mAnd made of double beams．Basis《Crane Design Manual》［10］，When the beam span is greater than 30 mTime，Using a rigid leg combined with a flexible leg can reduce the horizontal support reaction caused by statics, so one side can be set as a rigid leg and fixed connection with the horizontal beam; The other side is provided with a flexible leg, which is connected with the main beam by ball hinge． Lower end width of rigid leg 1.25 m,Upper width m .5A schematic diagram of the structure 1as shown．
Chart1 Original design of gantry crane
From the analysis of structural mechanics，Chart1After the main beam is subjected to vertical load, the main beam will not only produce downward flexure, but also produce lateral deflection to the right along the． A small amount of side deviation is allowed, but when the side deviation is large, it will not only affect the normal use of the door crane， And there are safety risks, even because of the tilt too large to cause the overall overturning of the door crane．
5 Finite element model and calculation results
In this paper, the diagram1General finite element software for gantry crane structureAN S Y S,Build the whole model according to the original design drawing． Selection of each plate forming the beam and legshell63Units, stiffeners and tracksbeam188Unit． Bolt connections and peripheral ancillary facilities without consideration of details( such as railings, escalators, etc) The finite element model is established as shown in the diagram2 as shown
Chart2 Finite element model of gantry crane structure
The rated lifting weight of the crane is200 t,The car is divided into two parts，Weight of upper car40 t,Weight of lower car45 t.Main girder steelQ 345B,Both leg steel are usedQ 235B.
Through structural mechanics［9］The most unfavorable load position of the main beam deflection is obtained by the influence line theory as shown in the diagram3 as shown． The load is added to the track position in the form of concentrated force by calculating the wheel pressure．
Lower Car Wheel Pressure:
P1 = αβγQPmax 1= 1. 05 × 1. 13 × 1. 4 × 182 =302.32(k N);
Car wheel pressure:
P2 =αβγQPmax 2 = 1. 05 × 1. 13 × 1. 4 × 175 × 2 =81.4(k N)...
Of which，According to specifications［3］，Dynamic coefficient α= 1. 05，F(xiàn)or box structure，Load increase coefficient β= 1. 13，γ of sub-coefficient of vertical load of craneQ = 1. 4． Pm a x 1 P; andm a x 2Next、Main wheel pressure on the trolley．
Chart3 Main girder deflection worst load layout
Under the condition of structure weight and crane full load lifting，At the same time
Considering the most unfavorable working conditions, the calculation results are as follows:
Maximum deflection of main girder( Figure 14 as shown) For
δ= 260. 9 m m. ( 1)
Lateral deflection of main girder along axial direction( Figure 15 as shown) For
m m. U =492.8 ( 2)
According to General Gantry Crane(GB /T14406) Annex － 93 ) ［2］ Section 1428. . The static rigidity of the crane is specified as: For exampleA5Crane, rated lifting weight and car weight in the main girder span( Or maximum deflection) The resulting vertical static deflection should not be greater than
S /800，Of whichSSpan for crane girder．
Chart4 deflection of main girder
Chart5 Lateral Displacement Map of Crane
From this we can see，The allowable vertical static deflection of the crane beam is
[δ]=83 000 mm /800 = 103. 75 mm, ( 3)
Through the following comparison:
δ= 260. 9 m m ＞［δ］= 103. 75 m m. ( 4)
It can be seen that the deflection of the main girder has far exceeded the general gantry crane》Static Rigid Provisions．
Based on the finite element analysis, it is found that the top of the gantry crane， That's when the main beam. m 049lateral displacement along the beam axis， In order to understand the harm caused by this displacement, we will first analyze the causes of such a large displacement．
6 Analysis of results
I've already introduced，F(xiàn)or the diagram1Structure shown，When the main beam is subjected to vertical load, the structure will inevitably produce a lateral deviation to the right， This is determined by its structural form．
In addition，Observation map1Medium Rigid Leg，Its structure form is asymmetric structure, its left side line is vertical ground, and the right side line is oblique straight line． The upper surface of the rigid leg is connected with the main beam by bolt and electric welding. The internal force on the contact surface after loading can be regarded as a uniformly distributed surface load, and the direction is vertical and downward; The lower surface is subjected to support reaction, which can be regarded as concentrated load because of the small contact area between the lifting wheel and the track, as shown in the figure
6 as shown． Considering the structural form of the rigid leg, the resultant force of the two forces is not in the same straight line, and under these two loads, the structure will produce a clockwise couple，F(xiàn)igure 16Central clockwise rotation arrow．
Obviously, when only this clockwise moment exists, the main beam will produce a lateral displacement to the right and a downward bending，F(xiàn)igure 16 Medium horizontal and vertical arrows, according to the superposition principle of structural mechanics， It will also increase the lateral deflection and midspan deflection of the main girder during normal operation． Therefore, the existence of this moment is unfavorable to the structure, hereinafter referred to as "unfavorable moment ", so it is best to eliminate the adverse effects of this moment on the structure．
Chart6 Analysis of Force in the Original Design of Crane
In the example of this paper, due to the existence of this unfavorable bending moment, on the one hand, the mid-span deflection of the main beam exceeds the specification requirement; On the other hand, as much as0. 49 m,In the normal use of the performance of a very large amount of sloshing, lifting objects will shake with it, so when the crane put down the lifting object is difficult to achieve accurate positioning． Ship-building cranes often require lifting components or equipment precisely in the mounting position for welding or fastening． Therefore, sloshing is very unfavorable to the normal operation of the crane．
At the same time, this unfavorable moment increases the stress level of the bolt at the connection between the rigid leg and the main beam, and the influence of the crane sloshing will obviously reduce the fatigue life of the bolt．
Because of the above problems, the design of the structure needs to be modified．
5 Design changes
Section 12The section is found by finite element calculation，A large gantry crane originally designed by a company has problems of midspan deflection and excessive side deflection， and in3The mechanism of its production is analyzed in the section，It is concluded that the design must be modified．
Increasing the size of the structure and increasing the stiffness of the structure can be an immediate result, but it will lead to the waste of resources and the extension of the construction period. Considering the commercial production and the basic principles of "safety, reliability and reasonable economy" in the structural design, this method should not be adopted if it is not necessary, but should give priority to the optimization of the structure．
by3Section analysis findings，The existence of unfavorable bending moment increases the deflection and lateral deflection of the structure, so it can change the structure performance only by eliminating the unfavorable bending moment． The unfavorable moment is caused by the unreasonable arrangement of the rigid leg, so it will be an effective method to change the arrangement of the rigid leg, which can not only eliminate the influence of the unfavorable moment, but also turn the adverse effect into advantage. Further reduce
the original deflection and side deflection of the main beam．
As a result, referring to the ideas [8] in the literature, the position of the inverted rigid leg is shown in the figure7as shown，A counterclockwise couple is produced under the combined force of the upper surface force and the lower concentrated force of the rigid leg， Figure 17Rotate the arrow counterclockwise，F(xiàn)igure II6In the opposite direction． On the one hand, under the sole action of this couple, the main beam will produce upward flexure，F(xiàn)igure 17The arrow up in the middle，Can offset part of the normal operation of the main beam deflection; On the other hand，The main beam will produce a lateral deviation to the left along the axial direction of the beam，F(xiàn)igure 17An arrow pointing horizontally to the left can offset part of the structure's intrinsic lateral bias． Therefore, the unfavorable bending moment can be changed into favorable bending moment after modification．
Chart7 Optimization of Crane Structure
In order to verify the effect of structural optimization, the calculation model is modified according to the above idea in finite element software，Just click7Modify the placement of rigid legs, other parameters remain unchanged． The mid-span deflection and side deflection of the main beam are calculated as follows:
Medium deflection of main girder
δ' = 80. 27 mm <103.9 75 mm,
The midspan deflection of the main girder decreases692%. to meet the General Gantry CraneGB /T14406-93［2］Requirements for stiffness of main girder． And has the bigger rigidity surplus, still has the bigger may optimize the space．
The lateral displacement of the main beam is
m m, U'=184
Relative to pre-optimization4928 mm. Down626%. The effect is ten
Obviously．
According to the above analysis and calculation results to inform the crane manufacturer，The manufacturer agrees to modify the above structure optimization planME150+110/25-83 A5Type gantry crane design and production of crane according to modified design． Guangdong Shipping Engineering Co., Ltd. has purchased a number of structural optimization of such cranes, so far has been safe and stable operation，Good economic and social benefits have been achieved．
5.Conclusion
In this paper, general finite element softwareANSYSDesigned for a companyME150+110/25-83 A5Holistic analysis of type gantry crane，It is found that the design has the following problems:
First of all, the midspan deflection of the main beam is too large and the stiffness can not meet the requirements of the code; Secondly, when the structure is subjected to force, the main beam has a large side deviation in the direction of its axis，Impact on structural
stability．
Based on the analysis of the mechanism of side deviation of crane structure, it is concluded that the unreasonable placement of rigid leg is the main cause of side deviation． The reasonable placement of the rigid leg will produce a favorable bending moment, which can not only reduce the mid-span deflection of the main beam, but also reduce the inherent lateral deflection of the structure after loading. It fully reflects the role of the rigid leg in the gantry crane structure．
References:
[1] Fang Zifan, Chen Yongqing, Wei Youlin, et al． Strength Analysis and Structural Improvement of Long-span Box Crane Beam[J].Journal of the Three Gorges University，
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