拱(gong)板設(she)備拱(gong)形(xing)所承受的(de)(de)荷載(zai)不同，其壓力(li)曲線(xian)的(de)(de)線(xian)形(xing)也不相同，一般按恒載(zai)下壓力(li)曲線(xian)確定;在活載(zai)作用下，拱(gong)內(nei)力(li)可能產生(sheng)彎矩，這時鉸(jiao)的(de)(de)設(she)置就會(hui)影(ying)響拱(gong)內(nei)彎矩的(de)(de)分(fen)布狀況。與剛架(jia)相仿，只有地基良好或兩側拱(gong)肢(zhi)處有穩定邊跨結構時才(cai)采用無(wu)鉸(jiao)拱(gong)，這種拱(gong)很少用于(yu)房屋(wu)建筑。雙鉸(jiao)拱(gong)應用較多，為適應軟弱地基上支座沉(chen)降差(cha)及拱(gong)拉桿(gan)變形(xing)，最好采用靜(jing)定結構的(de)(de)三(san)鉸(jiao)拱(gong)。
拱(gong)(gong)(gong)(gong)以曲桿抗(kang)衡并(bing)傳遞外力(li)(li)(li)給支座(zuo)(zuo)，故(gu)鉸支座(zuo)(zuo)不(bu)(bu)僅(jin)承(cheng)受豎(shu)向(xiang)力(li)(li)(li)，并(bing)有相當大的(de)(de)(de)水平向(xiang)外的(de)(de)(de)拱(gong)(gong)(gong)(gong)腳(jiao)(jiao)推力(li)(li)(li)，其(qi)合(he)力(li)(li)(li)就位(wei)于拱(gong)(gong)(gong)(gong)軸曲線在(zai)支座(zuo)(zuo)點的(de)(de)(de)切線方(fang)向(xiang)上。拱(gong)(gong)(gong)(gong)腳(jiao)(jiao)有推力(li)(li)(li)是(shi)其(qi)主要力(li)(li)(li)學特征之(zhi)一，矢高f越小，推力(li)(li)(li)越大。一次超靜定(ding)的(de)(de)(de)雙鉸拱(gong)(gong)(gong)(gong)，支座(zuo)(zuo)的(de)(de)(de)垂直(zhi)或水平位(wei)移均會引起(qi)內力(li)(li)(li)變化，對支座(zuo)(zuo)在(zai)推力(li)(li)(li)作(zuo)用下無變位(wei)的(de)(de)(de)要求(qiu)就更(geng)嚴格(ge)。由此可(ke)見，為了使拱(gong)(gong)(gong)(gong)保(bao)持正常工(gong)作(zuo)，務必(bi)確(que)保(bao)其(qi)支座(zuo)(zuo)能承(cheng)受住推力(li)(li)(li)而不(bu)(bu)位(wei)移，故(gu)拱(gong)(gong)(gong)(gong)腳(jiao)(jiao)推力(li)(li)(li)的(de)(de)(de)結構處理(li)，是(shi)拱(gong)(gong)(gong)(gong)結構設(she)計的(de)(de)(de)中心問題。
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