無梁拱,拱形屋面被(bei)廣(guang)泛用(yong)于工(gong)業廠房、倉(cang)儲(chu)庫(ku)房、無梁拱體(ti)育(yu)場(chang)館、集(ji)貿市(shi)場(chang)、車庫(ku)機庫(ku)等，它無梁無擦、空間高大開(kai)闊，可以(yi)隨意(yi)分割組合(he)，使用(yong)方便，自(zi)重輕、剛性(xing)強、彈(dan)性(xing)好(hao)、抗震性(xing)能優越等特點。
無(wu)梁拱(gong)(gong)(gong),拱(gong)(gong)(gong)形(xing)屋(wu)面還具有(you)承壓效果，拱(gong)(gong)(gong)所承受(shou)的荷載(zai)不同，其(qi)壓力(li)曲(qu)(qu)線(xian)的線(xian)形(xing)也不相(xiang)同，一(yi)般按恒載(zai)下(xia)壓力(li)曲(qu)(qu)線(xian)確定(ding);在活載(zai)作用(yong)下(xia)，拱(gong)(gong)(gong)內(nei)力(li)可能(neng)產生彎(wan)矩，這時鉸(jiao)(jiao)的設(she)置就會影響拱(gong)(gong)(gong)內(nei)彎(wan)矩的分布狀況。與剛架相(xiang)仿(fang)，只有(you)地基(ji)良好或兩側拱(gong)(gong)(gong)肢處有(you)穩(wen)定(ding)邊跨(kua)結(jie)構(gou)(gou)時才采(cai)用(yong)無(wu)鉸(jiao)(jiao)拱(gong)(gong)(gong)，這種(zhong)拱(gong)(gong)(gong)很少用(yong)于(yu)房屋(wu)建筑。雙鉸(jiao)(jiao)拱(gong)(gong)(gong)應(ying)用(yong)較(jiao)多，為適應(ying)軟弱地基(ji)上支座沉(chen)降差及拱(gong)(gong)(gong)拉桿變形(xing)，最好采(cai)用(yong)靜定(ding)結(jie)構(gou)(gou)的三鉸(jiao)(jiao)拱(gong)(gong)(gong)。
拱(gong)以曲桿抗衡并(bing)傳遞(di)外力(li)給支(zhi)(zhi)座(zuo)，故鉸支(zhi)(zhi)座(zuo)不僅(jin)承(cheng)(cheng)受豎向(xiang)(xiang)力(li)，并(bing)有相當大的水平向(xiang)(xiang)外的拱(gong)腳推(tui)力(li)，其合力(li)就(jiu)位(wei)于拱(gong)軸曲線(xian)(xian)在(zai)支(zhi)(zhi)座(zuo)點的切線(xian)(xian)方向(xiang)(xiang)上。拱(gong)腳有推(tui)力(li)是(shi)其主要(yao)力(li)學特(te)征(zheng)之一(yi)，矢高f越(yue)小(xiao)，推(tui)力(li)越(yue)大。一(yi)次超靜定(ding)的雙鉸拱(gong)，金屬屋面支(zhi)(zhi)座(zuo)的垂直或水平位(wei)移均會引起內力(li)變(bian)化，對支(zhi)(zhi)座(zuo)在(zai)推(tui)力(li)作(zuo)用下無變(bian)位(wei)的要(yao)求就(jiu)更嚴(yan)格。由此可(ke)見，為了使(shi)拱(gong)保持(chi)正常工作(zuo)，務必確保其支(zhi)(zhi)座(zuo)能承(cheng)(cheng)受住推(tui)力(li)而不位(wei)移，故拱(gong)腳推(tui)力(li)的結(jie)構處理，是(shi)拱(gong)結(jie)構設計(ji)的中心(xin)問(wen)題。
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