無梁拱,拱形屋面被(bei)廣泛用于工業廠房、倉儲庫房、無(wu)梁拱體育場館、集貿市場、車庫機庫等，它無(wu)梁無(wu)擦、空間(jian)高大開闊，可以隨意分割組(zu)合，使用方便，自重(zhong)輕、剛性(xing)強、彈性(xing)好、抗震(zhen)性(xing)能優(you)越等特點。
無梁拱(gong)(gong)(gong),拱(gong)(gong)(gong)形屋面還(huan)具有(you)承(cheng)壓(ya)(ya)(ya)效果，拱(gong)(gong)(gong)所承(cheng)受的荷載不同，其壓(ya)(ya)(ya)力曲(qu)線(xian)的線(xian)形也不相同，一般按恒(heng)載下(xia)壓(ya)(ya)(ya)力曲(qu)線(xian)確定(ding);在活載作用(yong)(yong)下(xia)，拱(gong)(gong)(gong)內力可能產生彎矩(ju)，這(zhe)時鉸(jiao)(jiao)(jiao)的設置就會影響拱(gong)(gong)(gong)內彎矩(ju)的分(fen)布狀況。與剛(gang)架相仿，只有(you)地基(ji)良好(hao)或兩側(ce)拱(gong)(gong)(gong)肢處有(you)穩(wen)定(ding)邊跨(kua)結(jie)構(gou)時才采用(yong)(yong)無鉸(jiao)(jiao)(jiao)拱(gong)(gong)(gong)，這(zhe)種拱(gong)(gong)(gong)很少用(yong)(yong)于房(fang)屋建筑(zhu)。雙鉸(jiao)(jiao)(jiao)拱(gong)(gong)(gong)應用(yong)(yong)較多(duo)，為(wei)適應軟弱地基(ji)上(shang)支座沉降差及拱(gong)(gong)(gong)拉桿變形，好(hao)采用(yong)(yong)靜定(ding)結(jie)構(gou)的三鉸(jiao)(jiao)(jiao)拱(gong)(gong)(gong)。
拱(gong)以曲桿抗(kang)衡并傳(chuan)遞(di)外力(li)(li)(li)(li)給支(zhi)座，故(gu)鉸支(zhi)座不(bu)僅承受(shou)(shou)豎向(xiang)(xiang)力(li)(li)(li)(li)，并有相當大的(de)(de)水平(ping)向(xiang)(xiang)外的(de)(de)拱(gong)腳推(tui)力(li)(li)(li)(li)，其(qi)合力(li)(li)(li)(li)就(jiu)位(wei)于拱(gong)軸曲線(xian)(xian)在支(zhi)座點的(de)(de)切線(xian)(xian)方向(xiang)(xiang)上。拱(gong)腳有推(tui)力(li)(li)(li)(li)是其(qi)主(zhu)要(yao)力(li)(li)(li)(li)學特征之一(yi)，矢高f越(yue)小，推(tui)力(li)(li)(li)(li)越(yue)大。一(yi)次(ci)超靜定(ding)的(de)(de)雙鉸拱(gong)，金屬(shu)屋面支(zhi)座的(de)(de)垂直(zhi)或(huo)水平(ping)位(wei)移均(jun)會引起(qi)內力(li)(li)(li)(li)變化，對支(zhi)座在推(tui)力(li)(li)(li)(li)作用下(xia)無變位(wei)的(de)(de)要(yao)求就(jiu)更嚴(yan)格(ge)。由(you)此可(ke)見，為了使拱(gong)保持正(zheng)常(chang)工(gong)作，務必確保其(qi)支(zhi)座能承受(shou)(shou)住推(tui)力(li)(li)(li)(li)而不(bu)位(wei)移，故(gu)拱(gong)腳推(tui)力(li)(li)(li)(li)的(de)(de)結構處理(li)，是拱(gong)結構設計的(de)(de)中心(xin)問題。
|
