大跨度門式起重機剛性支腿對結構剛度的影響分析外文文獻翻譯、中英文翻譯、外文翻譯

大跨度門式起重機剛性支腿對結構剛度的影響分析外文文獻翻譯、中英文翻譯、外文翻譯,跨度,起重機,剛性,結構,剛度,影響,分析,外文,文獻,翻譯,中英文 18大跨度門式起重機剛性支腿對結構剛度的影響分析官保華，甄圣威，曾慶敦( 華南理工大學 土木與交通學院，廣東 廣州 510640)摘要: 利用有限元軟件對某公司設計的 83 m 跨度 A5 型門式起重機的剛度進行分析，求得的主梁撓度超出通用門式起重機( GB/ T14406 93) 的規(guī)定，且結構產生較大的側向位移 通過對剛性支腿結構設計進行修改，使得主梁最大撓度下降 69. 2% ，側向位移下降 62. 6% 關鍵詞: 門式起重機; 剛性支腿; 吊車梁; 側偏中圖分類號: TU32文獻標志碼: A文章編號: 1007-7162( 2011) 04-0083-04隨著船海工業(yè)的發(fā)展，大跨度、大噸位吊車的應用越來越廣泛，以滿足造船業(yè)生產的靈活性和建造大型船只時對吊裝噸位的需求 箱型梁有剛度大和抗偏扭性能好等諸多優(yōu)點1，使之廣泛運用于大跨度吊車梁中 由于吊車梁對容許撓度有嚴格的規(guī)定2 3，超出此規(guī)定不但會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算顯得尤為必要 通過對文獻4 8的調研發(fā)現(xiàn)，對門吊鮮有關于側向剛度的研究報道，僅文獻8提及了造船門式起重機門架反變位技術，但未進行深入的理論研究 由于大跨度門吊多采用一剛一柔兩條支腿的形式，由結構力學9分析可以發(fā)現(xiàn)，這種結構在受豎向力作用后必然會發(fā)生側偏，這種側偏對結構是非常不利的，這一點將在后面的論述中詳細說明 在發(fā)現(xiàn)設計不滿足規(guī)范要求后就盲目地加大結構尺寸、提高結構剛度的做法顯然是不明智的，也是不經濟的，應首先考慮通過結構上的優(yōu)化改造來達到預期效果 本文通過對門式起重機剛性支腿的設計改造，在不增加建造成本，不改變門吊凈空的基礎上，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側偏位移較大的情況，充分說明了剛性支腿在門式起重機結構上所起的作用1 門式起重機的結構形式本文以某公司設計的 ME150 + 110 /25 83A5 型門式起重機為例，設計最大起重量 200 t，主梁跨度 83 m，高達 55 m，梁高 5 m 且由雙梁構成 根據(jù)起重機設計手冊10，當梁跨度大于 30 m 時，采用一個剛性支腿一個柔性支腿相結合的結構形式，可以減小因超靜定產生的水平支反力，故其中一側可設置為剛性支腿，與水平梁采用固定式連接; 另一側設置為柔性支腿，采用球鉸與主梁連接 剛性支腿下端寬 1. 25 m，上端寬 5 m 其結構簡圖如圖 1 所示圖 1 門式起重機原始設計示意圖由結構力學的分析易知，圖 1 所示結構在主梁受到豎向荷載后，主梁除會產生向下?lián)锨酝?，還會 產生向右的沿著梁軸向的側偏 小量的側偏是允許的，但當側偏較大時，不但會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致門 吊的整體傾覆2 有限元模型及計算結果本文對圖 1 所示龍門吊車結構使用通用有限元軟件 ANSYS，依據(jù)原設計圖紙建立整體模型 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 不考慮細部的螺栓連結和外圍輔助配套設施( 如欄桿、扶梯等) 對結構響，建立有限元模型如圖 2 所示圖 2 龍門吊車結構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通過結構力學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 = QP1max = 1. 05 1. 13 1. 4 182 =302. 32( kN) ;上小車輪壓:P2 = QP2max = 1. 05 1. 13 1. 4 175 2 =81. 4( kN) 其中，根據(jù)規(guī)范3，取動力系數(shù) = 1. 05，對于箱形結構，荷載增大系數(shù) = 1. 13，吊車豎向荷載分項系數(shù)Q = 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構自重和吊車滿載起吊的條件下，同時考慮最不利工況，計算結果如下:主梁最大撓度( 如圖 4 所示) 為 = 260. 9 mm( 1)主梁沿軸向的側偏位移( 如圖 5 所示) 為U = 492. 8 mm( 2)根據(jù)通用門式起重機( GB / T14406 93 ) 2 第 4. 2. 8 條，起重機的靜態(tài)剛性規(guī)定為: 對于 A5 型起重機，起重機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大于S /800，其中 S 為起重機主梁的跨度圖 4 主梁撓度圖圖 5 吊車側向位移圖由此可知，該吊車梁的許用垂直靜撓度為= 83 000 mm /800 = 103. 75 mm，( 3)通過如下比較: = 260. 9 mm = 103. 75 mm( 4)可見，主梁撓度已遠超過了通用門式起重機的靜態(tài)剛性規(guī)定通過對有限元計算的分析發(fā)現(xiàn)，門式吊機頂部， 即主梁發(fā)生了多達 0. 49 m 的沿梁軸向的側向位移， 為了了解這個位移帶來的危害，下面將先分析如此 大位移產生的原因3 計算結果分析前面已經介紹過，對于圖 1 所示的結構，在主梁受到豎向荷載作用時，結構必然會產生向右的側偏， 這是由它的結構形式所決定的此外，觀察圖 1 中剛性支腿，其結構形式為非對稱結構，其左側邊線為垂直地面，而右側邊線為斜直線 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 考慮剛性支腿的結構形式，這兩個力的合力并非在同一條直線上，在這兩個荷載作用下，結構會產生一個順時針的力偶，如圖 6 中順時針旋轉箭頭所示顯然，當僅有這個順時針彎矩存在時，主梁會產 生一個向右的側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)結構力學的疊加原理， 它將另外增加主梁在正常工作時的側偏和跨中撓 度 因此這個彎矩的存在對結構是不利的，以下稱其 為“不利彎矩”，故最好能消除這個彎矩對結構的不 利影響圖 6 吊車原設計受力分析簡圖在本文的實例中，由于這個不利彎矩的存在，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_ 0. 49 m，在正常使用過程中表現(xiàn)為很大幅度的晃動，起吊物將隨其晃動，因此當?shù)踯嚪畔缕鸬跷飼r難以實現(xiàn)精確定位 而造船用起重機常常需要將起吊的構件或設備精確地吊放在安裝位置，以備焊接或栓緊 因此，晃動對吊車的正常工作是十分不利的同時，此不利彎矩增加了剛性支腿與主梁連接處螺栓的應力水平，加之吊車晃動的影響，將明顯降低螺栓的疲勞壽命由于結構存在上述種種問題，因此需對結構的設計進行修改4 設計修改第 2 節(jié)通過有限元計算發(fā)現(xiàn)，某公司原設計的大型門式起重機存在跨中撓度和側偏過大的問題， 并在第 3 節(jié)中分析了其產生的機理，得出了必須修改設計的結論加大結構尺寸，提高結構剛度雖可立竿見影，但會造成資源的浪費、工期的延長，考慮到生產的商業(yè)性和結構設計中“安全可靠，經濟合理”的基本原則，這種方法在非必要的情況下不應采取，而應優(yōu)先考慮結構優(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構跨中撓度和側偏量，故只需消除不利彎矩的作用便可起到改變結構性能的作用 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?，進一步減小主梁原本的撓度和側偏綜上所述，參照文獻8的思路，將翻轉剛性支 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，產生一個逆時針的力偶， 如圖 7 中逆時針旋轉箭頭所示，與圖 6 中的力偶方向恰恰相反 在這個力偶的單獨作用下，一方面，主梁將產生向上的撓曲，如圖 7 中向上的箭頭所示，可以抵消一部分正常工作時主梁的下?lián)? 另一方面，主梁會產生向左的沿梁軸向的側偏，如圖 7 中水平向左的箭頭所示，可以抵消部分的結構固有側偏 故不利彎矩在經過改造后可以變?yōu)閷Y構有利的彎矩圖 7 吊車結構優(yōu)化受力圖為了驗證結構優(yōu)化后的效果，在有限元軟件中按上述思想修改計算模型，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 經計算得到主梁跨中撓度與側偏量如下:主梁跨中撓度為 = 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GB / T14406 932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)上述的分析和計算結果告知起重機生產廠家，廠家同意按上述結構優(yōu)化方案修改原 ME150 + 110 /25 83A5 型門式起重機的設計并按修改后的設計生產起重機 廣東某船務工程有限公司購買了多臺經結構優(yōu)化后的此類吊車，迄今為止一直安全穩(wěn)定運營，取得了良好的經濟和社會效益5.結論本文通過通用有限元軟件 ANSYS 對某公司設計的 ME150 + 110 /25 83A5 型門式起重機進行整體分析，發(fā)現(xiàn)該設計存在如下問題:首先，主梁跨中撓度過大，剛度不能滿足規(guī)范要求; 其次，結構在受力時，主梁在其軸線方向上有較大的側偏，影響結構的穩(wěn)定通過對吊車結構產生側偏的機理分析，得出了剛性支腿不合理的擺放方式是造成結構側偏的主要原因 剛性支腿的合理擺放會產生一個有利于結構的彎矩，不但可以減小主梁的跨中撓度，而且可以減小結構在受載后的固有側偏位移，充分體現(xiàn)了剛性支腿在門式起重機結構中所起的作用參考文獻:1 方子帆，陳永清，魏友霖，等 大跨度箱形吊車梁的強度分析及結構改進J 三峽大學學報，2007，29( 2) :141-1432 大連起重機器廠 GB/ T14406-93，通用門式起重機S北京: 中國標準出版社，19933 中華人民共和國建設部 GB50017-2003，鋼結構設計規(guī)范S 北京: 中國計劃出版社，20034 劉標，程文明，栗園園 鉸接式支腿箱梁門式起重機有限元分析J 起重運輸機械，2010( 4) : 47-495 許海翔，李鳴，李振林 基于虛擬樣機的門式起重機安全分析J 起重運輸機械，2010( 7) : 40-446 閻少泉 造船門式起重機結構型式及性能比較J 科技創(chuàng)新與生產力，2010( 12) : 94-95，997 陳進，樊艷，侯沂，等 大型雙梁桁架門式起重機鋼結構設計與研究J 中國工程機械學報，2009，7 ( 1 ) : 63-678 肖海江 造船門式起重機門架反變位技術的應用J機械工程師，2009 ( 4) : 155-1569 朱慈勉 結構力學M 北京: 高等教育出版社，200410 張質文 起重機設計手冊M 北京: 中國鐵道工業(yè)出版社，1998Analysis of the Influence of Long-span Gantry Cranes Rigid Legs on Structure StiffnessGan 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 83m 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% ， respectivelyKey words: gantry crane; rigid leg; crane beam; laterodeviationAnalysis on the Influence of Rigid Legs of Long-span Gantry Crane on Structural StiffnessGuan 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 exceedsGeneral gantry crane( G B / T 14406 93)Provisions，And the structure produces large lateral displacementModification 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 deviationMiddle Chart Classification Number:TU32Document symbol codeA :1Number of articles:1007-7162(2011)04-0083-04With 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 resistance1，It is widely used in large span crane beams Because the crane beam has strict requirements for allowable deflection2 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 literature8 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 mechanics9It 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 explained4 Structure of gantry craneThis 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 beamsBasisCrane Design Manual10，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 shownChart1 Original design of gantry craneFrom 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 crane5 Finite element model and calculation resultsIn 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 shownChart2 Finite element model of gantry crane structureThe 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 mechanics9The 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 pressureLower Car Wheel Pressure:P1 = QPmax 1= 1. 05 1. 13 1. 4 182 =302.32(k N);Car wheel pressure:P2 =QPmax 2 = 1. 05 1. 13 1. 4 175 2 =81.4(k N).Of which，According to specifications3，Dynamic coefficient = 1. 05，F(xiàn)or box structure，Load increase coefficient = 1. 13， of sub-coefficient of vertical load of craneQ = 1. 4 Pm a x 1 P; andm a x 2Next、Main wheel pressure on the trolleyChart3 Main girder deflection worst load layoutUnder the condition of structure weight and crane full load lifting，At the same timeConsidering the most unfavorable working conditions, the calculation results are as follows:Maximum deflection of main girder( Figure 14 as shown) For= 260. 9 m m.( 1)Lateral deflection of main girder along axial direction( Figure 15 as shown) Form 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 thanS /800，Of whichSSpan for crane girderChart4 deflection of main girderChart5 Lateral Displacement Map of CraneFrom this we can see，The allowable vertical static deflection of the crane beam is=83 000 mm /800 = 103. 75 mm,( 3)Through the following comparison:= 260. 9 m m = 103. 75 m m.( 4)It can be seen that the deflection of the main girder has far exceeded the general gantry craneStatic Rigid ProvisionsBased on the finite element analysis, it is found that the top of the gantry crane， Thats 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 displacement6 Analysis of resultsIve 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 formIn 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 figure6 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 arrowObviously, 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 structureChart6 Analysis of Force in the Original Design of CraneIn 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 craneAt 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 boltBecause of the above problems, the design of the structure needs to be modified5 Design changesSection 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 modifiedIncreasing 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 structureby3Section 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 beamAs 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 structures intrinsic lateral bias Therefore, the unfavorable bending moment can be changed into favorable bending moment after modificationChart7 Optimization of Crane StructureIn 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 = 80. 27 mm 103.9 75 mm,The midspan deflection of the main girder decreases692%. to meet the General Gantry CraneGB /T14406-932Requirements for stiffness of main girder And has the bigger rigidity surplus, still has the bigger may optimize the spaceThe lateral displacement of the main beam ism m, U=184Relative to pre-optimization4928 mm. Down626%. The effect is tenObviouslyAccording 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 achieved5.ConclusionIn 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 stabilityBased 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 structureReferences:1 Fang Zifan, Chen Yongqing, Wei Youlin, et al Strength Analysis and Structural Improvement of Long-span Box Crane BeamJ.Journal of the Three Gorges University，