橋式起重機(jī)主體結(jié)構(gòu)設(shè)計【10t雙梁（吊鉤）橋式起重機(jī)】
橋式起重機(jī)主體結(jié)構(gòu)設(shè)計【10t雙梁（吊鉤）橋式起重機(jī)】,10t雙梁（吊鉤）橋式起重機(jī),橋式起重機(jī)主體結(jié)構(gòu)設(shè)計【10t雙梁（吊鉤）橋式起重機(jī)】,橋式起重機(jī),主體,結(jié)構(gòu)設(shè)計,10,雙梁,吊鉤
橋式起重機(jī)主體結(jié)構(gòu)設(shè)計
摘要
起重機(jī)的用途是將物品從空間的某一個地點搬運到另一個地點。為了完成這個作業(yè)，起重機(jī)一般具有使物品沿空間的三個方向運動的機(jī)構(gòu)。橋式類型的起重機(jī)是依靠起重機(jī)運行機(jī)構(gòu)和小車運行機(jī)構(gòu)的組合運動使所搬運的物品在長方形平面內(nèi)作運動。
起重機(jī)是現(xiàn)代生產(chǎn)不可缺少的組成部分，借助起重機(jī)可以實現(xiàn)主要工藝流程和輔助作業(yè)的機(jī)械化，在流水線和自動線生產(chǎn)車間中，起重機(jī)大大提高了生產(chǎn)效率。
本文主要完成了橋式起重機(jī)主體結(jié)構(gòu)部分的設(shè)計及主梁和端梁的校核計算。采用正軌箱形梁橋架，正軌箱形梁橋架由兩根主梁和端梁構(gòu)成。主梁外側(cè)分別設(shè)有走臺，并與端梁通過連接板焊接在一起形成剛性結(jié)構(gòu)。為了運輸方便在端梁中間設(shè)有接頭，通過連接板和角鋼使用螺栓連接，這種結(jié)構(gòu)運輸方便、安裝容易。小車軌道固定于主梁的壓板上，壓板焊接在蓋板的中央。
本文正確選擇了起重機(jī)橋架鋼結(jié)構(gòu)構(gòu)造形式和構(gòu)件截面，以保證其在使用過程中的強(qiáng)度、剛度和穩(wěn)定性。設(shè)計時，同時還注意了起重機(jī)的結(jié)構(gòu)制造工藝性、省料、安裝以及維修方便等問題。
關(guān)鍵詞：橋式起重機(jī)；主體結(jié)構(gòu)；橋架
Design of main body structure of bridge-type hoist crane
Abstract
The usage of hoist crane is to transport goods from some place to another one. In order to accomplish this job, there is mechanism in the hoist crane which makes the goods move along the space in three directions. The bridge type hoist crane carries the goods to move in the rectangular plane depending upon the combination of the hoist crane movement mechanism and the car movement.
The hoist crane plays an important role in the modern age. It is possible to realize the mechanization of main technical process and assistance work with the help of the hoist crane. The hoist crane can improve the production efficiency greatly in the assembly line and production workshop.
This paper mainly completes the design of main-body structure and checking up calculation of the bridge-type hoist crane. Box-girder bridge type is adopted which is made up of two main beams and end girders. The main beams have walking platform on outside plates and welded with end girders to form rigid structure. For transportation convenience, joints are adopted in the middle of the end girders, and connected together with junction panels, angle-steels and bolts, which brings about transportation convenience and easy fixing. The car rails are fixuped on up-plates of the main beams which are welded in the middle of the up-plates.
The hoist crane bridge types and the structural cross sections are chosen correct to ensure their intensity, the rigidity and the stability in the use process. Meanwhile, the structure manufacture technology capability, materials saving, fixing and convenience of maintenance and so on are paid attention to.
Key word: Bridge-type hoist crane; main body structure; bridge
目 錄
第1章 緒言……………………………………………………………………………………………1
1.1 起重機(jī)的概述‥…………………………………………………………………………1
1.2 起重機(jī)發(fā)展趨勢………………………………………………………………………‥1
第2章 起重機(jī)總體方案設(shè)計……………………………………………………………………3
2.1 起重機(jī)參數(shù)確定…………………………………………………………………………3
2.2 起重機(jī)總體方案……………………………………………………………………………3
2.3 橋架主體結(jié)構(gòu)方案…………………………………………………………………………3
第3章 起重機(jī)主體結(jié)構(gòu)設(shè)計………………………………………………………………………5
3.1 起重機(jī)鋼結(jié)構(gòu)載荷情況…………………………………………………………………5
3.2 橋架金屬結(jié)構(gòu)計算…………………………………………………………………………5
3.2.1 主梁計算載荷………………………………………………………………………5
3.2.2 主梁截面尺寸的選擇………………………………………………………………7
第4章 主體結(jié)構(gòu)各承載部分的計算與校核………………………………………………9
4.1 主梁主要截面計算……………………………………………………………………9
4.2 主梁支承附近截面計算………………………………………………………………10
4.3 端梁計算…………………………………………………………………………………16
總結(jié)…………………………………………………………………………………………………………20
參考文獻(xiàn)…………………………………………………………………………………………………21
附錄A：英文原文………………………………………………………………………………………22
附錄B：英文譯文………………………………………………………………………………………25
謝辭…………………………………………………………………………………………………………28
橋式起重機(jī)主體結(jié)構(gòu)設(shè)計
1． 設(shè)計的目的及意義
起重機(jī)是在建筑工地、工廠等場所廣泛使用的一種機(jī)械裝置，它的廣泛應(yīng)用是現(xiàn)代生產(chǎn)特點的標(biāo)志，它將人們從繁重的體力勞動中解放出來，提高生產(chǎn)率。
橋式起重機(jī)是廣泛應(yīng)用于工業(yè)廠房里的一種起重運輸裝置，設(shè)計一個結(jié)構(gòu)合理、使用方便、工作可靠是橋式起重機(jī)在實際生產(chǎn)中具有積極的現(xiàn)實意義。
2． 主要設(shè)計任務(wù)、要求
完成橋式起重機(jī)主體結(jié)構(gòu)的設(shè)計；功能實現(xiàn)合理，結(jié)構(gòu)簡單實用，工作可靠；圖紙整潔、清晰、正確，符合有關(guān)設(shè)計標(biāo)準(zhǔn)；說明書要邏輯性強(qiáng)，表達(dá)清楚，字跡工整；圖紙數(shù)量、說明書排版格式及裝訂順序符合機(jī)電工程學(xué)院有關(guān)要求。鼓勵使用計算機(jī)繪圖。
序言；起重機(jī)參數(shù)確定；起重機(jī)總體方案設(shè)計；起重機(jī)主體結(jié)構(gòu)設(shè)計；起重機(jī)主體結(jié)構(gòu)各承載部分的計算與校核。
3． 主要設(shè)計參數(shù)
室內(nèi)工作
額定起重量：100KN
起升高度：8~14m
起升速度：8m/min
小車運行速度：40m/min
大車運行速度：90m/min
4． 進(jìn)度安排
第2—6周：文獻(xiàn)、資料查詢，初步確定設(shè)計方案；
第7—8周：調(diào)研并完成方案設(shè)計；
第9—12周：完成圖紙設(shè)計任務(wù)和計算任務(wù)；
第13—16周：完成畢業(yè)設(shè)計，準(zhǔn)備答辯。
5． 參考文獻(xiàn)
1）《使用起重手冊》
2）《起重機(jī)設(shè)計手冊》
3）《機(jī)械傳動設(shè)計手冊》
4）《起重運輸機(jī)械》
5）網(wǎng)絡(luò)資源
橋式起重機(jī)主體結(jié)構(gòu)設(shè)計
第1章 緒言
1.1 起重機(jī)的概述
工程起重機(jī)是各種工程建設(shè)廣泛使用的重要起重設(shè)備，它對減輕勞動強(qiáng)度，節(jié)省人力，降低建設(shè)成本，提高施工質(zhì)量，加快建設(shè)速度，實現(xiàn)工程施工機(jī)械化起著十分重要的作用。起重機(jī)作業(yè)是使物品沿空間的三個方向運動。其中作上下移動的起升機(jī)構(gòu)是不可缺少的。平面運動可以用兩種不同的運動組合來實現(xiàn)。按照這種組合方式不同，起重機(jī)可分為兩大類型：橋式起重機(jī)和回轉(zhuǎn)類型起重機(jī)。
橋式類型起重機(jī)就依靠起重機(jī)運行機(jī)構(gòu)和小車運行機(jī)構(gòu)的組合使所搬運的物品在長方形平面內(nèi)運動。驅(qū)動起重機(jī)運動的是起升機(jī)構(gòu)、運行機(jī)構(gòu)、回轉(zhuǎn)機(jī)構(gòu)和變幅機(jī)構(gòu)。為了實現(xiàn)這些運動、安放這些機(jī)構(gòu)并承受載荷，起重機(jī)必須有足夠的強(qiáng)度和剛度的金屬結(jié)構(gòu)，有驅(qū)動機(jī)構(gòu)運動并實現(xiàn)運動控制的動力控制系統(tǒng)；以及，為保證起重機(jī)安全并可靠運轉(zhuǎn)的安全和信號指示裝置。
起重機(jī)的特點是：短周期的循環(huán)作業(yè)。一個工作循環(huán)包括：取物，起升并運行靠卸貨點，下降，卸料，然后空車返回原地。一個工作循環(huán)的時間一般只要幾十秒種到幾分鐘，最長的也不會超過一、二十分鐘。這一特點對它的動力裝置的選擇及電氣設(shè)備容量的計算有較大的影響。經(jīng)常起動、制動引起傳動機(jī)構(gòu)和金屬結(jié)構(gòu)的強(qiáng)烈沖擊和振動，導(dǎo)致產(chǎn)生較大的動載荷，由于這種載荷是非常平穩(wěn)的，這使得強(qiáng)度和疲勞計算變得較為復(fù)雜。此外，對于裝卸散裝物料的起重機(jī)，生產(chǎn)效率是一個很重要的性能指標(biāo)， 它不僅取決于各機(jī)構(gòu)的運動速度，而且也依賴裝卸物料的輔助時間的大小。因此對于速度、加速度值，運動的重疊程度，取物及卸貨的自動化程度的選擇等都應(yīng)仔細(xì)考慮。
雙梁橋式起重機(jī)尤其適合室內(nèi)重物的起升和搬運，所以廣泛被工廠所采用。橋架結(jié)構(gòu)的設(shè)計好與壞對起重機(jī)的性價比（性能與價格的比）提高有很重要的意義。長期以來，機(jī)械設(shè)計工作者沿用類比的設(shè)計方法。這種設(shè)計過程可概括為“設(shè)計—分析—再設(shè)計”的過程。即首先根據(jù)設(shè)計任務(wù)及要求進(jìn)行調(diào)查研究和收集有關(guān)資料，參照相同或類似任務(wù)現(xiàn)有的、已經(jīng)完成的較為成熟的設(shè)計方案。憑借設(shè)計者的經(jīng)驗輔以必要的分析計算。確定一個合適的設(shè)計方案，并通過估算初步確定有關(guān)參數(shù)，然后對初定方案進(jìn)行必要的分析及校核計算；如果某些設(shè)計要求得不到滿足。則可進(jìn)行設(shè)計方案的修改。設(shè)計參數(shù)的調(diào)整，并再次的進(jìn)行分析計算。如此多次反復(fù)，直到獲得滿意的設(shè)計方案為止。此方法不僅需要花費較多的時間，增加設(shè)計周期，而且只限于在少數(shù)方案中進(jìn)行分析比較。
隨著電子計算機(jī)技術(shù)的發(fā)展和應(yīng)用，以線性規(guī)劃與非線性規(guī)劃為主要內(nèi)容的新的數(shù)學(xué)規(guī)劃應(yīng)用于工程設(shè)計問題。雙梁橋式起重機(jī)橋架設(shè)計應(yīng)用該優(yōu)化方法，將迅速得到一對相對很合理的截面參數(shù)。這不僅降低了設(shè)計者的工作強(qiáng)度，而且與提高了設(shè)計方案的可行性。使得起重機(jī)金屬結(jié)構(gòu)的合理設(shè)計，對減輕起重機(jī)自重，提高起重性能，節(jié)約鋼材，提高起重機(jī)的可靠性都有重要意義。
2.2 起重機(jī)發(fā)展趨勢
對工程起重機(jī)，特別是大功率的工程起重機(jī)的需要量日以增加。隨著現(xiàn)代科學(xué)技術(shù)的發(fā)展，各種新技術(shù)、新材料、新結(jié)構(gòu)、新工藝在工程起重機(jī)上得到廣泛的應(yīng)用。所有這些因素都有里地促進(jìn)了工程起重機(jī)的發(fā)展。根據(jù)國內(nèi)外現(xiàn)有工程起重機(jī)產(chǎn)品和技術(shù)資料的分析，近年來工程起重機(jī)的發(fā)展趨勢主要體現(xiàn)在以下幾個方面：
（1）廣泛采用液壓技術(shù)
液壓傳動具有體積小、重量輕、機(jī)構(gòu)緊湊、能無級調(diào)速、操縱簡便、運轉(zhuǎn)平穩(wěn)和工作安全的優(yōu)點。
（2）通用型起重機(jī)以中小型為主，專用起重機(jī)向大型大功率發(fā)展
為了提高建設(shè)工程的裝卸和安裝作業(yè)的機(jī)械化程度，工程起重機(jī)的發(fā)展，仍然是以輕便靈活的中小型起重機(jī)為主。
（3）重視“三化”，逐步過渡采用國際標(biāo)準(zhǔn)
三化是指：標(biāo)準(zhǔn)化、系列化、通用化
（4）發(fā)展一機(jī)多用產(chǎn)品
為了充分發(fā)揮工程起重機(jī)的作用，擴(kuò)大其使用范圍，有的國家在設(shè)計起重機(jī)是重視了 產(chǎn)品的多用性。
（5）采用新技術(shù)、新材料、新結(jié)構(gòu)、新工藝
為了減輕起重機(jī)的自重，提高起重機(jī)的性能，保證起重機(jī)可靠地工作，現(xiàn)在都多采用新技術(shù)、新材料、新結(jié)構(gòu)和新工藝。
第2章 起重機(jī)總體方案設(shè)計
2.1 起重機(jī)參數(shù)確定
（1）室內(nèi)工作
（2）額定起重量：Q = 10 噸
（3）起升高度：H = 12 米
（4）起升速度：v升= 8 米/分
（5）小車運行速度：v小= 40米/分
（6）大車運行速度：v大= 90米/分
選跨度L = 16.5米，機(jī)構(gòu)工作類別 — 中級（JC = 25%）
2.2 起重機(jī)總體方案
對于起重量為10噸的橋式起重機(jī)，可以設(shè)計成電動單梁葫蘆式，即橋式起重機(jī)采用單主梁結(jié)構(gòu)，在主梁的下端焊接有工字鋼來作為電動葫蘆的運行軌道，起吊貨物直接通過電動葫蘆完成；還可以采用雙梁小車式方案，即采用雙主梁結(jié)構(gòu)，小車運行于安裝在主梁上的軌道上，起吊貨物由小車起升機(jī)構(gòu)來完成。
對這兩種方案都是可行的，同時也是現(xiàn)在比較通用的兩個設(shè)計方案，經(jīng)過認(rèn)真比較，決定采用雙梁小車式。首先，雖然現(xiàn)在起重量為10噸的電動葫蘆已經(jīng)大量生產(chǎn)，但還沒有實行標(biāo)準(zhǔn)化和系列化，設(shè)計資料相對殘缺和稀少；而運行小車式橋式起重機(jī)設(shè)計資料相對多一點，有利于進(jìn)一步的設(shè)計和優(yōu)化。其次，這次設(shè)計的起重機(jī)選用跨度為16.5米，如果采用單梁電動葫蘆式，勢必使主梁結(jié)構(gòu)龐大，由于主梁大都采用箱形焊接結(jié)構(gòu)，尺寸增大就會增加焊接難度，且增大焊接變形。再次，采用雙梁小車式，設(shè)計制造安裝方便，設(shè)備維護(hù)和維修簡單。
雙梁橋式起重機(jī)傳動系統(tǒng)的設(shè)計，主要包括起升機(jī)構(gòu)傳動系統(tǒng)的設(shè)計、小車運行機(jī)構(gòu)設(shè)計及大車運行驅(qū)動機(jī)構(gòu)設(shè)計。主要采用電力驅(qū)動，通過聯(lián)軸器和減速器再把動力傳遞到工作機(jī)構(gòu)，對于這種傳遞系統(tǒng)，由于電動機(jī)、聯(lián)軸器及減速器均以標(biāo)準(zhǔn)化，因而可以選用標(biāo)準(zhǔn)件而簡化設(shè)計。
2.3 橋架主體結(jié)構(gòu)方案
（1）主梁采用正軌箱形結(jié)構(gòu)（如圖1 a）
a — 正軌箱形梁；b — 偏軌箱形梁；c — 半偏軌箱形梁
圖1 正軌箱形結(jié)構(gòu)圖
（2）橋架為焊接結(jié)構(gòu)（如圖2）
圖2 箱形梁焊接圖
第3章 起重機(jī)主體結(jié)構(gòu)設(shè)計
3.1 起重機(jī)鋼結(jié)構(gòu)載荷情況
作用在起重機(jī)上的外載荷有：起升載荷、自重載荷、動載荷和風(fēng)載荷等。
（1）起升載荷
起升載荷就是由起升機(jī)構(gòu)吊起的貨物和取物裝置以及其它隨同升降的裝置重量之總合。對起升高度很大的鋼絲繩起升機(jī)構(gòu)，起升載荷應(yīng)包括掛著的鋼絲繩重量。
（2）自重載荷
起重機(jī)本身重量包括機(jī)械部分、金屬結(jié)構(gòu)及電氣設(shè)備等的重量。如果起重機(jī)上裝有運輸機(jī)，則應(yīng)考慮運輸機(jī)及其上的貨物的重量。自重在設(shè)計前一般是未知的，可參考同類型參數(shù)接近的起重機(jī)的自重做初步選定。有些手冊上列有各類起重機(jī)依照起重量或載重力矩而定的自重表可供參考。自重的分配根據(jù)結(jié)構(gòu)情況而定。機(jī)械及電氣設(shè)備一般可看作是集中載荷，箱形結(jié)構(gòu)和連續(xù)運輸機(jī)上的貨物可看作是連續(xù)分布的。
（3）動載荷
動載荷是由運動速度改變而引起的質(zhì)量力，即慣性力。在啟動與制動期間，剛體做平移運動時，它的質(zhì)量產(chǎn)生加速或減速慣性力。
（4）風(fēng)載荷
由于本設(shè)計是屬于室內(nèi)工作，故不存在風(fēng)載荷。
3.2 橋架金屬結(jié)構(gòu)計算
所計算是起重機(jī)橋架由兩根用鋼板焊接是箱形主梁組成，主梁固定在裝有大車輪的端梁上。此外，裝有大車運行機(jī)構(gòu)的輔助橫梁和縱梁也固定在橋架上。橋架上設(shè)有欄桿和走臺在端梁頭部裝有緩沖器。
橋架跨度L = 16.5米
初定起重機(jī)輪距B = 4.5米
初定小車軌距K小車=2米
初定小車輪距b= 1.6米
橋架為正軌箱形焊接結(jié)構(gòu)。
橋架材料選用Q215鋼（GB700-88）
3.2.1 主梁計算載荷
假定小車車輪輪壓相等，則起重機(jī)在額定載荷下每一個車輪到軌道上的移動載荷為：
P = K + = 1.2 + = 4200公斤
式中 K動— 動力系數(shù)，考慮貨物提升或下降時的慣性力，K動= 1.1 ；1.2 ；1.3 — 相應(yīng)于輕級、中級和重級工作類型，本設(shè)計采用中級工作類型。
假定大車運行機(jī)構(gòu)的重量均勻地作用在一根梁上，則雙梁橋架半邊的重量和運行機(jī)構(gòu)自重所產(chǎn)生的均布載荷為：
q = 公斤/米
式中 — 半邊焊接箱形雙梁橋架自重（不包括端梁）， 近似為 = 5000 公斤（如圖3） ；
— 大車運行機(jī)構(gòu)重量，近似為 = 2200公斤；
— 考慮起重機(jī)運行時振動的系數(shù)；
當(dāng)v時， = 1.0；
當(dāng)1.5米/秒 v 時， = 1.1；
當(dāng)3米/秒 v 時， = 1.2。
圖3 雙梁橋架焊接箱形重量曲線圖
司機(jī)室和電氣設(shè)備重量產(chǎn)生的集中載荷為：
p= G= 1.12000 = 2200公斤
式中 G司— 司機(jī)室和電氣設(shè)備的重量，G司= 2000公斤
集中驅(qū)動的大車運行機(jī)構(gòu)裝在與主梁相連的懸臂橫梁上，其扭矩為：
M = e= 2200 0.75 = 1650 公斤米
式中 e— 為大車運行機(jī)構(gòu)重心至主梁截面中心的水平距離。
根據(jù)計算經(jīng)驗，當(dāng)起動和制動時起重機(jī)的加速度為0.25米/秒和0.5米/秒，而當(dāng)猛烈起動或制動時，假定加速度增加一倍，即0.5米/秒和1.0米/秒。根據(jù)車輪和軌道的粘著條件，最大加速度為：
0.98米/秒
因此，猛烈制動時= 0.98米/秒。橋架猛烈制動時在水平面內(nèi)引起的橫向均布慣性載荷為：
公斤/米
猛烈制動時，由司機(jī)室重量在水平面內(nèi)引起的橫向集中慣性載荷為：
200公斤
猛烈制動時，小車自重和吊重在水平面內(nèi)引起的橫向集中慣性載荷為：
740公斤
根據(jù)計算經(jīng)驗，起動和制動時，小車的加、減速度為0.1米/秒和0.25米/秒，當(dāng)猛烈起動和制動時，小車的加速度可為0.2米/秒和0.5米/秒。根據(jù)車輪和軌道的粘著條件加速度值可達(dá)0.98米/秒。因此，小車猛烈制動時a制max= 0.5米/秒。當(dāng)負(fù)載小車猛烈制動時，在水平面內(nèi)的縱向集中慣性載荷為：
378公斤
3.2.2 主梁截面尺寸的選擇
橋架中部箱形主梁的高度：
H =（）L =（）16500
=1030 ~ 825毫米
取H = 900 毫米
支承處的梁高為：
H=（0.6 ~ 0.7）H =（0.6 ~ 0.7） = 540 ~ 630毫米
取H = 600 毫米
變截面傾斜長度：
L=（0.1 ~ 0.2）L =（0.1 ~ 0.2） = 1650 ~ 3300毫米
取L= 2000毫米
上、下翼緣板寬度：
B =（0.5 ~ 0.33）H =（0.5 ~ 0.33） = 450 ~ 297毫米
此外，翼緣寬度應(yīng)滿足條件：
B 毫米
取B = 350毫米
初算時取腹板厚度毫米，而上、下翼緣板厚度毫米（圖4）
a — 跨中；b — 支承附近
圖4 橋架主梁橫截面
第4章 主體結(jié)構(gòu)各承載部分的計算與校核
4.1 主梁主要截面計算
上、下翼緣的截面積： F = 2厘米
腹板的截面積 F = 2厘米
截面總面積： F = F + F = 56 + 106 = 162厘米
對x — x軸的截面慣性矩：
翼緣：
I
= 111400厘米
腹板：
I= 厘米
截面總慣性矩：
I II= 111400 + 68080
= 180480厘米
對x — x軸的截面模數(shù)：
W = 厘米
對y — y軸的截面慣性矩
翼緣：
I= 厘米
腹板：
I
= 26483厘米
截面總慣性矩：
I II= 5717 + 26483
= 32200厘米
對y — y軸的截面模數(shù)：
W = 厘米
4.2 主梁支承附近截面的計算
上、下翼緣的截面積： F = 56厘米
腹板的面積 ： F = 2 厘米
截面總面積： F = F+ F = 56 + 70 = 162厘米
對x — x軸的截面慣性矩：
翼緣：
I
= 49068厘米
腹板：
I= 厘米
截面總慣性矩：
I II= 49068 + 19918
= 68986厘米
對x — x軸的截面模數(shù)：
W = 厘米
對y — y軸的截面慣性矩：
翼緣：
I= 厘米
腹板：
I
= 17496厘米
截面總慣性矩：
I II= 5717 + 17496
= 23213厘米
對y — y軸的截面模數(shù)：
W = 厘米
按額定載荷時橋架和小車同時猛烈制動的最不利載荷情況計算主梁。此外，也考慮由大車運行機(jī)構(gòu)和司機(jī)室重量對梁引起的載荷。
對主梁0 — 0軸（如圖5）的扭矩
圖5 扭矩計算圖
M
= 33490公斤厘米
當(dāng)改變力和的方向時，對主梁0 — 0軸的扭矩為：
= -490公斤厘米
取最大值（= 33490公斤厘米）作為扭矩計算值。求由固定載荷和移動載荷在垂直和水平內(nèi)產(chǎn)生的主梁最大彎矩。當(dāng)跨度中心至載荷p的距離與跨度中心至合力R的距離相等時，即主梁跨中至載荷p之間的距離為時，兩個移動載荷在左邊車輪下面的梁截面內(nèi)產(chǎn)生最大彎矩。
在垂直面內(nèi)主梁的支承反力：
由固定載荷的作用（如圖6a）
圖6 主梁計算圖
a和b — 分別為由固定載荷和移動載荷在垂直面內(nèi)的作用；
c和b — 分別為有固定載荷和移動載荷的慣性力在水平面內(nèi)的作用；
e — 由于扭矩的作用。
由活動載荷的作用（如圖6b）
= 2.25米 ， b = 1.6米
彎矩值：
= 3996 = 31369公斤米
= 5860
= 18892公斤米
由垂直載荷在截面1— 1引起的最大彎矩：
公斤米
在水平面內(nèi)主梁的支承反力 （圖6c、d）：
公斤
公斤
公斤
公斤
彎矩值：
= 352 = 2763公斤米
= 536
= 1732公斤米
河南理工大學(xué)萬方科技學(xué)院本科畢業(yè)論文
The Use and History of Crane
Every time we see a crane in action we remains without words, these machines are sometimes really huge, taking up tons of material hundreds of meters in height. We watch with amazement and a bit of terror, thinking about what would happen if the load comes off or if the movement of the crane was wrong. It is a really fascinating system, surprising both adults and children. These are especially tower cranes, but in reality there are plenty of types and they are in use for centuries. The cranes are formed by one or more machines used to create a mechanical advantage and thus move large loads. Cranes are equipped with a winder, a wire rope or chain and sheaves that can be used both to lift and lower materials and to move them horizontally. It uses one or more simple machines to create mechanical advantage and thus move loads beyond the normal capability of a human. Cranes are commonly employed in the transport industry for the loading and unloading of freight, in the construction industry for the movement of materials and in the manufacturing industry for the assembling of heavy equipment.
1. Overview
The first construction cranes were invented by the Ancient Greeks and were powered by men or beasts of burden, such as donkeys. These cranes were used for the construction of tall buildings. Larger cranes were later developed, employing the use of human treadwheels, permitting the lifting of heavier weights. In the High Middle Ages, harbor cranes were introduced to load and unload ships and assist with their construction – some were built into stone towers for extra strength and stability. The earliest cranes were constructed from wood, but cast iron and steel took over with the coming of the Industrial Revolution.
For many centuries, power was supplied by the physical exertion of men or animals, although hoists in watermills and windmills could be driven by the harnessed natural power. The first 'mechanical' power was provided by steam engines, the earliest steam crane being introduced in the 18th or 19th century, with many remaining in use well into the late 20th century. Modern cranes usually use internal combustion engines or electric motors and hydraulic systems to provide a much greater lifting capability than was previously possible, although manual cranes are still utilized where the provision of power would be uneconomic.
Cranes exist in an enormous variety of forms – each tailored to a specific use. Sizes range from the smallest jib cranes, used inside workshops, to the tallest tower cranes, used for constructing high buildings. For a while, mini - cranes are also used for constructing high buildings, in order to facilitate constructions by reaching tight spaces. Finally, we can find larger floating cranes, generally used to build oil rigs and salvage sunken ships. This article also covers lifting machines that do not strictly fit the above definition of a crane, but are generally known as cranes, such as stacker cranes and loader cranes.
2. History
Ancient Greece
The crane for lifting heavy loads was invented by the Ancient Greeks in the late 6th century BC. The archaeological record shows that no later than c.515 BC distinctive cuttings for both lifting tongs and lewis irons begin to appear on stone blocks of Greek temples. Since these holes point at the use of a lifting device, and since they are to be found either above the center of gravity of the block, or in pairs equidistant from a point over the center of gravity, they are regarded by archaeologists as the positive evidence required for the existence of the crane.
The introduction of the winch and pulley hoist soon lead to a widespread replacement of ramps as the main means of vertical motion. For the next two hundred years, Greek building sites witnessed a sharp drop in the weights handled, as the new lifting technique made the use of several smaller stones more practical than of fewer larger ones. In contrast to the archaic period with its tendency to ever-increasing block sizes, Greek temples of the classical age like the Parthenon invariably featured stone blocks weighing less than 15-20 tons. Also, the practice of erecting large monolithic columns was practically abandoned in favor of using several column drums.
Although the exact circumstances of the shift from the ramp to the crane technology remain unclear, it has been argued that the volatile social and political conditions of Greece were more suitable to the employment of small, professional construction teams than of large bodies of unskilled labor, making the crane more preferable to the Greek polis than the more labor-intensive ramp which had been the norm in the autocratic societies of Egypt or Assyria.
The first unequivocal literary evidence for the existence of the compound pulley system appears in the Mechanical Problems (Mech. 18, 853a32-853b13) attributed to Aristotle (384-322 BC), but perhaps composed at a slightly later date. Around the same time, block sizes at Greek temples began to match their archaic predecessors again, indicating that the more sophisticated compound pulley must have found its way to Greek construction sites by then.
Ancient Rome
The heyday of the crane in ancient times came during the Roman Empire, when construction activity soared and buildings reached enormous dimensions. The Romans adopted the Greek crane and developed it further. We are relatively well informed about their lifting techniques, thanks to rather lengthy accounts by the engineers Vitruvius (De Architectura 10.2, 1-10) and Heron of Alexandria (Mechanica 3.2-5). There are also two surviving reliefs of Roman treadwheel cranes, with the Haterii tombstone from the late first century AD being particularly detailed.
The simplest Roman crane, the Trispastos, consisted of a single-beam jib, a winch, a rope, and a block containing three pulleys. Having thus a mechanical advantage of 3:1, it has been calculated that a single man working the winch could raise 150 kg (3 pulleys x 50 kg = 150), assuming that 50 kg represent the maximum effort a man can exert over a longer time period. Heavier crane types featured five pulleys (Pentaspastos) or, in case of the largest one, a set of three by five pulleys (Polyspastos) and came with two, three or four masts, depending on the maximum load. The Polyspastos, when worked by four men at both sides of the winch, could already lift 3000 kg (3 ropes x 5 pulleys x 4 men x 50 kg = 3000 kg). In case the winch was replaced by a treadwheel, the maximum load even doubled to 6000 kg at only half the crew, since the treadwheel possesses a much bigger mechanical advantage due to its larger diameter. This meant that, in comparison to the construction of the Egyptian Pyramids, where about 50 men were needed to move a 2.5 ton stone block up the ramp (50 kg per person), the lifting capability of the Roman Polyspastos proved to be 60 times higher (3000 kg per person).
However, numerous extant Roman buildings which feature much heavier stone blocks than those handled by the Polyspastos indicate that the overall lifting capability of the Romans went far beyond that of any single crane. At the temple of Jupiter at Baalbek, for instance, the architrave blocks weigh up to 60 tons each, and one corner cornice block even over 100 tons, all of them raised to a height of about 19 m. In Rome, the capital block of Trajan's Column weighs 53.3 tons, which had to be lifted to a height of about 34 m (see construction of Trajan's Column).
It is assumed that Roman engineers lifted these extraordinary weights by two measures (see picture below for comparable Renaissance technique): First, as suggested by Heron, a lifting tower was set up, whose four masts were arranged in the shape of a quadrangle with parallel sides, not unlike a siege tower, but with the column in the middle of the structure (Mechanica 3.5). Second, a multitude of capstans were placed on the ground around the tower, for, although having a lower leverage ratio than treadwheels, capstans could be set up in higher numbers and run by more men (and, moreover, by draught animals). This use of multiple capstans is also described by Ammianus Marcellinus (17.4.15) in connection with the lifting of the Lateranense obelisk in the Circus Maximus (ca. 357 AD). The maximum lifting capability of a single capstan can be established by the number of lewis iron holes bored into the monolith. In case of the Baalbek architrave blocks, which weigh between 55 and 60 tons, eight extant holes suggest an allowance of 7.5 ton per lewis iron, that is per capstan. Lifting such heavy weights in a concerted action required a great amount of coordination between the work groups applying the force to the capstans.
Middle Ages
During the High Middle Ages, the treadwheel crane was reintroduced on a large scale after the technology had fallen into disuse in western Europe with the demise of the Western Roman Empire. The earliest reference to a treadwheel (magna rota) reappears in archival literature in France about 1225, followed by an illuminated depiction in a manuscript of probably also French origin dating to 1240. In navigation, the earliest uses of harbor cranes are documented for Utrecht in 1244, Antwerp in 1263, Brugge in 1288 and Hamburg in 1291, while in England the treadwheel is not recorded before 1331.
Generally, vertical transport could be done more safely and inexpensively by cranes than by customary methods. Typical areas of application were harbors, mines, and, in particular, building sites where the treadwheel crane played a pivotal role in the construction of the lofty Gothic cathedrals. Nevertheless, both archival and pictorial sources of the time suggest that newly introduced machines like treadwheels or wheelbarrows did not completely replace more labor-intensive methods like ladders, hods and handbarrows. Rather, old and new machinery continued to coexist on medieval construction sites and harbors.
Apart from treadwheels, medieval depictions also show cranes to be powered manually by windlasses with radiating spokes, cranks and by the 15th century also by windlasses shaped like a ship's wheel. To smooth out irregularities of impulse and get over 'dead-spots' in the lifting process flywheels are known to be in use as early as 1123.
The exact process by which the treadwheel crane was reintroduced is not recorded, although its return to construction sites has undoubtedly to be viewed in close connection with the simultaneous rise of Gothic architecture. The reappearance of the treadwheel crane may have resulted from a technological development of the windlass from which the treadwheel structurally and mechanically evolved. Alternatively, the medieval treadwheel may represent a deliberate reinvention of its Roman counterpart drawn from Vitruvius' De architectura which was available in many monastic libraries. Its reintroduction may have been inspired, as well, by the observation of the labor-saving qualities of the waterwheel with which early treadwheels shared many structural similarities.
Structure and placement
The medieval treadwheel was a large wooden wheel turning around a central shaft with a treadway wide enough for two workers walking side by side. While the earlier 'compass-arm' wheel had spokes directly driven into the central shaft, the more advanced 'clasp-arm' type featured arms arranged as chords to the wheel rim, giving the possibility of using a thinner shaft and providing thus a greater mechanical advantage.
Contrary to a popularly held belief, cranes on medieval building sites were neither placed on the extremely lightweight scaffolding used at the time nor on the thin walls of the Gothic churches which were incapable of supporting the weight of both hoisting machine and load. Rather, cranes were placed in the initial stages of construction on the ground, often within the building. When a new floor was completed, and massive tie beams of the roof connected the walls, the crane was dismantled and reassembled on the roof beams from where it was moved from bay to bay during construction of the vaults. Thus, the crane ‘grew’ and ‘wandered’ with the building with the result that today all extant construction cranes in England are found in church towers above the vaulting and below the roof, where they remained after building construction for bringing material for repairs aloft.
Less frequently, medieval illuminations also show cranes mounted on the outside of walls with the stand of the machine secured to putlogs.
Mechanics and operation
In contrast to modern cranes, medieval cranes and hoists - much like their counterparts in Greece and Rome - were primarily capable of a vertical lift, and not used to move loads for a considerable distance horizontally as well. Accordingly, lifting work was organized at the workplace in a different way than today. In building construction, for example, it is assumed that the crane lifted the stone blocks either from the bottom directly into place, or from a place opposite the centre of the wall from where it could deliver the blocks for two teams working at each end of the wall. Additionally, the crane master who usually gave orders at the treadwheel workers from outside the crane was able to manipulate the movement laterally by a small rope attached to the load. Slewing cranes which allowed a rotation of the load and were thus particularly suited for dockside work appeared as early as 1340. While ashlar blocks were directly lifted by sling, lewis or devil's clamp (German Teufelskralle), other objects were placed before in containers like pallets, baskets, wooden boxes or barrels.
It is noteworthy that medieval cranes rarely featured ratchets or brakes to forestall the load from running backward. This curious absence is explained by the high friction force exercised by medieval treadwheels which normally prevented the wheel from accelerating beyond control.
Harbor usage
According to the "present state of knowledge" unknown in antiquity, stationary harbor cranes are considered a new development of the Middle Ages. The typical harbor crane was a pivoting structure equipped with double treadwheels. These cranes were placed docksides for the loading and unloading of cargo where they replaced or complemented older lifting methods like see-saws, winches and yards.
Two different types of harbor cranes can be identified with a varying geographical distribution: While gantry cranes which pivoted on a central vertical axle were commonly found at the Flemish and Dutch coastside, German sea and inland harbors typically featured tower cranes where the windlass and treadwheels were situated in a solid tower with only jib arm and roof rotating. Interestingly, dockside cranes were not adopted in the Mediterranean region and the highly developed Italian ports where authorities continued to rely on the more labor-intensive method of unloading goods by ramps beyond the Middle Ages.
Unlike construction cranes where the work speed was determined by the relatively slow progress of the masons, harbor cranes usually featured double treadwheels to speed up loading. The two treadwheels whose diameter is estimated to be 4 m or larger were attached to each side of the axle and rotated together. Today, according to one survey, fifteen treadwheel harbor cranes from pre-industrial times are still extant throughout Europe.[28] Beside these stationary cranes, floating cranes which could be flexibly deployed in the whole port basin came into use by the 14th century.
Renaissance
A lifting tower similar to that of the ancient Romans was used to great effect by the Renaissance architect Domenico Fontana in 1586 to relocate the 361 t heavy Vatican obelisk in Rome. From his report, it becomes obvious that the coordination of the lift between the various pulling teams required a considerable amount of concentration and discipline, since, if the force was not applied evenly, the excessive stress on the ropes would make them rupture.
Early modern age
Cranes were used domestically in the 17th and 18th century. The chimney or fireplace crane was used to swing pots and kettles over the fire and the height was adjusted by a trammel.
3. Mechanical principles
There are two major considerations in the design of cranes. The first is that the crane must be able to lift a load of a specified weight and the second is that the crane must remain stable and not topple over when the load is lifted and moved to another location.
Lifting capacity
Cranes illustrate the use of one or more simple machines to create mechanical advantage.
? The lever. A balance crane contains a horizontal beam (the lever) pivoted about a point called the fulcrum. The principle of the lever allows a heavy load attached to the shorter end of the beam to be lifted by a smaller force applied in the opposite direction to the longer end of the beam. The ratio of the load's weight to the applied force is equal to the ratio of the lengths of the longer arm and the shorter arm, and is called the mechanical advantage.
? The pulley. A jib crane contains a tilted strut (the jib) that supports a fixed pulley block. Cables are wrapped multiple times round the fixed block and round another block attached to the load. When the free end of the cable is pulled by hand or by a winding machine, the pulley system delivers a force to the load that is equal to the applied force multiplied by the number of lengths of cable passing between the two blocks. This number is the mechanical advantage.
? The hydraulic cylinder. This can be used directly to lift the load or indirectly to move the jib or beam that carries another lifting device.
Cranes, like all machines, obey the principle of conservation of energy. This means that the energy delivered to the load cannot exceed the energy put into the machine. For example, if a pulley system multiplies the applied force by ten, then the load moves only one tenth as far as the applied force. Since energy is proportional to force multiplied by distance, the output energy is kept roughly equal to the input energy (in practice slightly less, because some energy is lost to friction and other inefficiencies).
Stability
For stability, the sum of all moments about any point such as the base of the crane must equate to zero. In practice, the magnitude of load that is permitted to be lifted (called the "rated load" in the US) is some value less than the load that will cause the crane to tip (providing a safety margin).
Under US standards for mobile cranes, the stability-limited rated load for a crawler crane is 75% of the tipping load. The stability-limited rated load for a mobile crane supported on outriggers is 85% of the tipping load. These requirements, along with additional safety-related aspects of crane design, are established by the American Society of Mechanical Engineers in the volume ASME B30.5-2007 Mobile and Locomotive Cranes.
Standards for cranes mounted on ships or offshore platforms are somewhat stricter because of the dynamic load on the crane due to vessel motion. Additionally, the stability of the vessel or platform must be considered.
For stationary pedestal or kingpost mounted cranes, the moment created by the boom, jib, and load is resisted by the pedestal base or kingpost. Stress within the base must be less than the yield stress of the material or the crane will fail.
4. Types of the cranes
Mobile
Main article: Mobile crane
The most basic type of mobile crane consists of a truss or telescopic boom mounted on a mobile platform - be it on road, rail or water.
Fixed
Exchanging mobility for the ability to carry greater loads and reach greater heights due to increased stability, these types of cranes are characterized that they, or at least their main structure does not move during the period of use. However, many can still
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