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華 東 交 通 大 學(xué)
畢 業(yè) 設(shè) 計（論 文）
題 目: 橋式起重機主體結(jié)構(gòu)設(shè)計
Design of main body structure of bridge-type hoist crane
學(xué) 院: 機電工程學(xué)院
專 業(yè): 機械設(shè)計與制造 班 級: 01機設(shè)（1）班
學(xué)生姓名: 陳向城 學(xué) 號: 20010310010807
指導(dǎo)教師: 范士娟 完成日期: 2005-6-13
畢業(yè)設(shè)計（論文）誠信聲明
本人鄭重聲明：所呈交的畢業(yè)設(shè)計（論文）是我個人在導(dǎo)師指導(dǎo)下進行的研究工作及取得的研究成果。就我所知，除了文中特別加以標(biāo)注和致謝的地方外，論文中不包含其他人已經(jīng)發(fā)表和撰寫的研究成果，也不包含為獲得華東交通大學(xué)或其他教育機構(gòu)的學(xué)位或證書所使用過的材料。
如在文中涉及抄襲或剽竊行為，本人愿承擔(dān)由此而造成的一切后果及責(zé)任。
本人簽名
導(dǎo)師簽名
2005年 6月 13日
華東交通大學(xué)畢業(yè)設(shè)計（論文）任務(wù)書
姓 名
陳向城
學(xué) 號
20010310010807
畢業(yè)屆別
2005
專 業(yè)
機械設(shè)計
畢業(yè)設(shè)計（論文）題目
橋式起重機主體結(jié)構(gòu)設(shè)計
指導(dǎo)教師
范士娟
學(xué) 歷
碩 士
職 稱
講 師
具體要求：
一、設(shè)計參數(shù)
1．起重量：Q=10t,工作級別為A5（中級 JC=25%）；
2．跨度L=16.5m,大車輪距B=4.5m,小車輪距b=1.6m；
3．大車運行機構(gòu)重Gy=2200kg,小車自重Gx=4800kg；
4．小車運行速度u=40m/min，大車運行速度v=90m/min；
二、任務(wù)要求
1．進行橋架結(jié)構(gòu)設(shè)計與計算；
2．編制詳細(xì)的設(shè)計計算說明書；
3．繪制主梁結(jié)構(gòu)圖、端梁結(jié)構(gòu)圖、橋式起重機總圖。
進度安排：
4.16~4.20 做好各項準(zhǔn)備，查閱相關(guān)的文獻及書籍
4.21~5.15 完成所有的設(shè)計計算
5.16~5.30 畫出設(shè)計要求的圖紙：主梁結(jié)構(gòu)圖、端梁結(jié)構(gòu)圖、橋式起重機總圖；
6.1~6.10 打出計算說明書及畢業(yè)總結(jié)（含英文摘要）
6.11~6.18 為畢業(yè)論文答辯作準(zhǔn)備
6.20~6.22 畢業(yè)答辯
指導(dǎo)教師簽字：
年 月 日
教研室意見：
教研室主任簽字：
年 月 日
題目發(fā)出日期
設(shè)計（論文）起止時間
附注：
華東交通大學(xué)學(xué)生開題報告書
課題名稱
橋式起重機主體結(jié)構(gòu)設(shè)計
課題來源
課題類型
AY
導(dǎo) 師
范士娟
學(xué)生姓名
陳向城
學(xué) 號
20010310010807
專 業(yè)
機械設(shè)計
開題報告內(nèi)容：
起重機是在建筑工地、工廠等場所廣泛使用的一種機械裝置，它的廣泛應(yīng)用是現(xiàn)代化生產(chǎn)特點的標(biāo)志，它將人們從繁重是體力勞動中解放出來，提高生產(chǎn)率。
這次設(shè)計是橋式起重機的主體結(jié)構(gòu)部分，主要包括橋式起重機的主梁和端梁的設(shè)計計算。通常把橋式起重機的主梁與端梁等部件組成的結(jié)構(gòu)稱為橋架，本次設(shè)計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。主梁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。小車軌道通過焊接在主梁上的壓板固定于蓋板中央，故稱正軌箱形梁。
橋式起重機是廣泛應(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、工作可靠的橋式起重機在實際生產(chǎn)中具有積極的現(xiàn)實意義。
方法及預(yù)期目的：
方法：
（1）確定起重機的總體方案，主梁采用正軌箱形結(jié)構(gòu)；
（2）確定起重機的各個參數(shù)，初定跨度L=16.5m；
（3）計算橋架主梁結(jié)構(gòu)，初步確定主梁的各個尺寸；
（4）在確定主梁的初定尺寸后，對所選參數(shù)進行驗算，然后合理調(diào)整尺寸；
（5）對橋架結(jié)構(gòu)進行校核，使之符合基本設(shè)計要求；
（6）用AUTOCAD繪制主梁、端梁以及總體結(jié)構(gòu)圖；
（7）編輯論文
預(yù)期目的：
主體結(jié)構(gòu)設(shè)計符合基本要求，功能實現(xiàn)合理、結(jié)構(gòu)簡單使用、工作可靠。
指導(dǎo)教師簽名： 日期：
課題類型：（1）A—工程設(shè)計；B—技術(shù)開發(fā)；C—軟件工程；D—理論研究；
（2）X—真實課題；Y—模擬課題；Z—虛擬課題
（1）、（2）均要填，如AY、BX等。
華東交通大學(xué)畢業(yè)設(shè)計(論文)評閱書(1)
姓 名
陳向城
學(xué) 號
20010310010807
專 業(yè)
機械設(shè)計與制造
畢業(yè)設(shè)計(論文)題目
橋式起重機主體結(jié)構(gòu)設(shè)計
指導(dǎo)教師評語：
得分
指導(dǎo)教師簽字：
年 月 日
評閱人評語：
得分
評閱人簽字：
年 月 日
等級
華東交通大學(xué)畢業(yè)設(shè)計(論文)評閱書(2)
姓 名
陳向城
學(xué) 號
20010310010807
專 業(yè)
機械設(shè)計與制造
畢業(yè)設(shè)計(論文)題目
橋式起重機主體結(jié)構(gòu)設(shè)計
答辯小組評語：
等級
組長簽字：
年 月 日
答辯委員會綜合評語：
等級
答辯委員會主任簽字：
年 月 日（學(xué)院公章）
注：答辯小組根據(jù)評閱人的評閱簽署意見、初步評定成績，交答辯委員會審定，蓋學(xué)院公章。
“等級”用優(yōu)、良、中、及、不及五級制（可按學(xué)院制定的畢業(yè)設(shè)計(論文)成績評定辦法評定最后成績）。
華東交通大學(xué)畢業(yè)設(shè)計（論文）答辯記錄
姓 名
陳向城
學(xué) 號
20010310010807
畢業(yè)屆別
2005
專 業(yè)
機械設(shè)計
題目
橋式起重機主體結(jié)構(gòu)設(shè)計
答辯時間
答辯組成員（簽字）：
答辯記錄：
記錄人（簽字）：
年 月 日
答辯小組組長（簽字）：
年 月 日
附注：
橋式起重機主體結(jié)構(gòu)設(shè)計
摘要
起重機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)，起重機一般具有使物品沿空間的三個方向運動的機構(gòu)。橋式類型的起重機是依靠起重機運行機構(gòu)和小車運行機構(gòu)的組合運動使所搬運的物品在長方形平面內(nèi)作運動。
起重機是現(xiàn)代生產(chǎn)不可缺少的組成部分，借助起重機可以實現(xiàn)主要工藝流程和輔助作業(yè)的機械化，在流水線和自動線生產(chǎn)車間中，起重機大大提高了生產(chǎn)效率。
本文主要完成了橋式起重機主體結(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度、剛度和穩(wěn)定性。設(shè)計時，同時還注意了起重機的結(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；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 起重機的概述‥…………………………………………………………………………1
1.2 起重機發(fā)展趨勢………………………………………………………………………‥1
第2章 起重機總體方案設(shè)計……………………………………………………………………3
2.1 起重機參數(shù)確定…………………………………………………………………………3
2.2 起重機總體方案……………………………………………………………………………3
2.3 橋架主體結(jié)構(gòu)方案…………………………………………………………………………3
第3章 起重機主體結(jié)構(gòu)設(shè)計………………………………………………………………………5
3.1 起重機鋼結(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…………………………………………………………………………………………………21
附錄A：英文原文………………………………………………………………………………………22
附錄B：英文譯文………………………………………………………………………………………25
謝辭…………………………………………………………………………………………………………28
華東交通大學(xué)畢業(yè)設(shè)計（論文）任務(wù)書
姓名
陳向城
學(xué)號
20010310010807
畢業(yè)屆別
2005
專業(yè)
機械設(shè)計及制造
畢業(yè)設(shè)計（論文）題目
橋式起重機主體結(jié)構(gòu)設(shè)計
指導(dǎo)教師
范士娟
學(xué) 歷
碩士
職 稱
講師
具體要求：
一、設(shè)計參數(shù)
1．起重量：Q=10t,工作級別為A5（中級 JC=25%）；
2．跨度L=16.5m,大車輪距B=4.5m,小車輪距b=1.6m；
3．大車運行機構(gòu)重Gy=2200kg,小車自重Gx=4800kg；
4．小車運行速度u=40m/min，大車運行速度v=90m/min；
二、任務(wù)要求
1．進行橋架結(jié)構(gòu)設(shè)計與計算；
2．編制詳細(xì)的設(shè)計計算說明書；
3．繪制主梁結(jié)構(gòu)圖、端梁結(jié)構(gòu)圖、橋式起重機總圖。
三、進度安排：
4.16~4.20 做好各項準(zhǔn)備，查閱相關(guān)的文獻及書籍
4.21~5.15 完成所有的設(shè)計計算
5.16~5.30 畫出設(shè)計要求的圖紙：主梁結(jié)構(gòu)圖、端梁結(jié)構(gòu)圖、橋式起重機總圖；
6.1~6.10 打出計算說明書及畢業(yè)總結(jié)（含英文摘要）
6.11~6.18 為畢業(yè)論文答辯作準(zhǔn)備
6.18~6.21 畢業(yè)答辯
指導(dǎo)教師簽字：
2005 年 月 日
教研室意見：
教研室主任簽字：
2005年 月 日
題目發(fā)出日期
設(shè)計（論文）起止時間
附注：
華東交通大學(xué)學(xué)生開題報告書
課題名稱
橋式起重機主體結(jié)構(gòu)設(shè)計
課題來源
模擬課題
課題類型
AY
導(dǎo) 師
范士娟
學(xué)生姓名
陳向城
學(xué) 號
20010310010807
專 業(yè)
機械設(shè)計及制造
開題報告內(nèi)容：
起重機是在建筑工地、工廠等場所廣泛使用的一種機械裝置，它的廣泛應(yīng)用是現(xiàn)代化生產(chǎn)特點的標(biāo)志，它將人們從繁重是體力勞動中解放出來，提高生產(chǎn)率。
這次設(shè)計是橋式起重機的主體結(jié)構(gòu)部分，主要包括橋式起重機的主梁和端梁的設(shè)計計算。通常把橋式起重機的主梁與端梁等部件組成的結(jié)構(gòu)稱為橋架，本次設(shè)計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。主梁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。小車軌道通過焊接在主梁上的壓板固定于蓋板中央，故稱正軌箱形梁。
橋式起重機是廣泛應(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、工作可靠的橋式起重機在實際生產(chǎn)中具有積極的現(xiàn)實意義。
方法及預(yù)期目的：
方法：
（1）確定起重機的總體方案，主梁采用正軌箱形結(jié)構(gòu)；
（2）確定起重機的各個參數(shù)，初定跨度L=16.5m；
（3）計算橋架主梁結(jié)構(gòu)，初步確定主梁的各個尺寸；
（4）在確定主梁的初定尺寸后，對所選參數(shù)進行驗算，然后合理調(diào)整尺寸；
（5）對橋架結(jié)構(gòu)進行校核，使之符合基本設(shè)計要求；
（6）用AUTOCAD繪制主梁、端梁以及總體結(jié)構(gòu)圖；
（7）編輯論文
預(yù)期目的：
主體結(jié)構(gòu)設(shè)計符合基本要求，功能實現(xiàn)合理、結(jié)構(gòu)簡單使用、工作可靠。
課題類型：（1）A—工程設(shè)計；B—技術(shù)開發(fā)；C—軟件工程；D—理論研究；
（2）X—真實課題；Y—模擬課題；Z—虛擬課題
（1）、（2）均要填，如AY、BX等。
橋式起重機主體結(jié)構(gòu)設(shè)計
摘要
起重機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)，起重機一般具有使物品沿空間的三個方向運動的機構(gòu)。橋式類型的起重機是依靠起重機運行機構(gòu)和小車運行機構(gòu)的組合運動使所搬運的物品在長方形平面內(nèi)作運動。
起重機是現(xiàn)代生產(chǎn)不可缺少的組成部分，借助起重機可以實現(xiàn)主要工藝流程和輔助作業(yè)的機械化，在流水線和自動線生產(chǎn)車間中，起重機大大提高了生產(chǎn)效率。
本文主要完成了橋式起重機主體結(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度、剛度和穩(wěn)定性。設(shè)計時，同時還注意了起重機的結(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；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
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