塔吊是建(jian)筑工地上常(chang)用的一種起(qi)(qi)重(zhong)設備(bei) 又名”塔(ta)式起(qi)(qi)重(zhong)機“，以一節一節的接(jie)長(chang)（高）（簡稱(cheng)“標準節”），用來吊施工用的(de)鋼筋、木(mu)楞、混凝土、鋼管等施工的(de)原材料。塔吊是工地(di)上一種(zhong)必不可少的(de)設備。
塔吊（tower crane）尖(jian)的(de)(de)(de)(de)功能(neng)是承受臂架拉繩(sheng)(sheng)及平(ping)(ping)(ping)衡臂拉繩(sheng)(sheng)傳來的(de)(de)(de)(de)上(shang)(shang)部(bu)(bu)荷載，并(bing)通(tong)過(guo)回(hui)轉(zhuan)(zhuan)塔架、轉(zhuan)(zhuan)臺、承座(zuo)等(deng)的(de)(de)(de)(de)結構(gou)部(bu)(bu)件式(shi)(shi)直接(jie)通(tong)過(guo)轉(zhuan)(zhuan)臺傳遞給塔身(shen)結構(gou)。自(zi)升(sheng)(sheng)塔頂有截(jie)錐柱式(shi)(shi)、前傾或后傾截(jie)錐柱式(shi)(shi)、人(ren)字架式(shi)(shi)及斜(xie)撐架式(shi)(shi)。 凡是上(shang)(shang)回(hui)轉(zhuan)(zhuan)塔機均(jun)需(xu)設平(ping)(ping)(ping)衡重(zhong)(zhong)(zhong)(zhong)，其功能(neng)是支(zhi)承平(ping)(ping)(ping)衡重(zhong)(zhong)(zhong)(zhong)，用以(yi)構(gou)成(cheng)設計上(shang)(shang)所(suo)要(yao)求的(de)(de)(de)(de)作用方面與(yu)起重(zhong)(zhong)(zhong)(zhong)力(li)矩方向相反(fan)的(de)(de)(de)(de)平(ping)(ping)(ping)衡力(li)矩。除(chu)平(ping)(ping)(ping)衡重(zhong)(zhong)(zhong)(zhong)外，還(huan)常在(zai)(zai)其尾(wei)部(bu)(bu)裝(zhuang)設起升(sheng)(sheng)機構(gou)。起升(sheng)(sheng)機構(gou)之(zhi)所(suo)以(yi)同(tong)平(ping)(ping)(ping)衡重(zhong)(zhong)(zhong)(zhong)一(yi)(yi)起安(an)放在(zai)(zai)平(ping)(ping)(ping)衡臂尾(wei)端，一(yi)(yi)則可(ke)(ke)發(fa)揮(hui)部(bu)(bu)分配重(zhong)(zhong)(zhong)(zhong)作用，二(er)則增大繩(sheng)(sheng)卷筒與(yu)塔尖(jian)導(dao)輪間的(de)(de)(de)(de)距離，以(yi)利(li)鋼絲(si)繩(sheng)(sheng)的(de)(de)(de)(de)排繞并(bing)避免發(fa)生(sheng)亂繩(sheng)(sheng)現象。平(ping)(ping)(ping)衡重(zhong)(zhong)(zhong)(zhong)的(de)(de)(de)(de)用量(liang)與(yu)平(ping)(ping)(ping)衡臂的(de)(de)(de)(de)長度(du)(du)成(cheng)反(fan)比關系(xi)，而(er)平(ping)(ping)(ping)衡臂長度(du)(du)與(yu)起重(zhong)(zhong)(zhong)(zhong)臂長度(du)(du)之(zhi)間又存在(zai)(zai)一(yi)(yi)定比例關系(xi)。平(ping)(ping)(ping)衡重(zhong)(zhong)(zhong)(zhong)量(liang)相當(dang)可(ke)(ke)觀，輕型塔機一(yi)(yi)般至(zhi)少要(yao)3～4t，重(zhong)(zhong)(zhong)(zhong)型的(de)(de)(de)(de)要(yao)近30t。
