無梁拱,拱形屋面被(bei)廣(guang)泛用于(yu)工業廠房(fang)、倉儲庫房(fang)、無梁拱體育場館、集貿市場、車庫機庫等，它無梁無擦(ca)、空(kong)間高大開闊，可(ke)以隨意分割(ge)組合，使用方便(bian)，自重輕、剛性強、彈性好、抗震性能優越等特(te)點。
無(wu)梁拱(gong)(gong),拱(gong)(gong)形(xing)屋(wu)面還具有(you)承壓效果，拱(gong)(gong)所承受的荷載(zai)不(bu)同(tong)，其壓力(li)曲(qu)線的線形(xing)也(ye)不(bu)相同(tong)，一般(ban)按(an)恒載(zai)下壓力(li)曲(qu)線確定(ding)(ding);在活載(zai)作用下，拱(gong)(gong)內力(li)可(ke)能產生彎(wan)矩，這(zhe)時(shi)鉸的設置就會影響拱(gong)(gong)內彎(wan)矩的分布狀況。與剛架相仿，只有(you)地(di)(di)基良好或(huo)兩側拱(gong)(gong)肢處有(you)穩定(ding)(ding)邊跨結(jie)構時(shi)才(cai)采(cai)用無(wu)鉸拱(gong)(gong)，這(zhe)種拱(gong)(gong)很少用于房屋(wu)建(jian)筑(zhu)。雙鉸拱(gong)(gong)應用較多，為適應軟弱地(di)(di)基上支(zhi)座(zuo)沉降差及(ji)拱(gong)(gong)拉桿變形(xing)，最好采(cai)用靜定(ding)(ding)結(jie)構的三鉸拱(gong)(gong)。
拱以曲桿抗衡(heng)并(bing)傳(chuan)遞(di)外力(li)(li)給支(zhi)(zhi)座(zuo)(zuo)(zuo)(zuo)，故鉸支(zhi)(zhi)座(zuo)(zuo)(zuo)(zuo)不僅承受(shou)豎向力(li)(li)，并(bing)有(you)相(xiang)當大的水(shui)(shui)平向外的拱腳推(tui)力(li)(li)，其(qi)合力(li)(li)就位(wei)(wei)(wei)于(yu)拱軸(zhou)曲線在(zai)(zai)支(zhi)(zhi)座(zuo)(zuo)(zuo)(zuo)點的切(qie)線方向上。拱腳有(you)推(tui)力(li)(li)是其(qi)主要力(li)(li)學特(te)征之一，矢高f越小(xiao)，推(tui)力(li)(li)越大。一次(ci)超靜定的雙(shuang)鉸拱，金(jin)屬屋面支(zhi)(zhi)座(zuo)(zuo)(zuo)(zuo)的垂直(zhi)或水(shui)(shui)平位(wei)(wei)(wei)移均(jun)會引起內力(li)(li)變化(hua)，對支(zhi)(zhi)座(zuo)(zuo)(zuo)(zuo)在(zai)(zai)推(tui)力(li)(li)作用(yong)下無變位(wei)(wei)(wei)的要求(qiu)就更嚴(yan)格。由(you)此可見，為了(le)使(shi)拱保持(chi)正常(chang)工作，務(wu)必確保其(qi)支(zhi)(zhi)座(zuo)(zuo)(zuo)(zuo)能承受(shou)住推(tui)力(li)(li)而(er)不位(wei)(wei)(wei)移，故拱腳推(tui)力(li)(li)的結(jie)構處理(li)，是拱結(jie)構設計的中心問題(ti)。
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