鋼橋桁(heng)(heng)架(jia)(jia)單元由上、下(xia)弦桿，豎(shu)桿和斜撐(cheng)焊接而(er)成。上、下(xia)弦桿的(de)(de)(de)一端(duan)(duan)為陰(yin)頭，另一端(duan)(duan)為陽頭，在陰(yin)、陽頭上都有銷(xiao)(xiao)子(zi)孔(kong)(kong)。兩(liang)節桁(heng)(heng)架(jia)(jia)拼接時(shi)，將(jiang)一節的(de)(de)(de)陽頭插(cha)(cha)入(ru)另一節的(de)(de)(de)陰(yin)頭內(nei)，對(dui)準銷(xiao)(xiao)子(zi)孔(kong)(kong)，插(cha)(cha)上銷(xiao)(xiao)子(zi)。桁(heng)(heng)架(jia)(jia)各孔(kong)(kong)的(de)(de)(de)用(yong)(yong)途如下(xia):弦桿螺栓孔(kong)(kong)用(yong)(yong)于(yu)拼裝雙(shuang)層(ceng)或加強(qiang)(qiang)(qiang)鋼橋時(shi)，將(jiang)桁(heng)(heng)架(jia)(jia)螺栓或弦桿螺栓插(cha)(cha)入(ru)弦桿螺栓孔(kong)(kong)內(nei)，使(shi)雙(shuang)層(ceng)桁(heng)(heng)架(jia)(jia)或桁(heng)(heng)架(jia)(jia)與(yu)加強(qiang)(qiang)(qiang)弦桿連接起來；支撐(cheng)架(jia)(jia)孔(kong)(kong)用(yong)(yong)來安裝支撐(cheng)架(jia)(jia)，當桁(heng)(heng)架(jia)(jia)用(yong)(yong)作主梁(liang)時(shi)，用(yong)(yong)中間兩(liang)個孔(kong)(kong)，用(yong)(yong)作橋腳時(shi)，用(yong)(yong)端(duan)(duan)部兩(liang)個孔(kong)(kong)，以(yi)加強(qiang)(qiang)(qiang)兩(liang)排桁(heng)(heng)架(jia)(jia)間的(de)(de)(de)聯系；風(feng)構孔(kong)(kong)用(yong)(yong)于(yu)連接抗(kang)風(feng)拉(la)桿；端(duan)(duan)豎(shu)桿上的(de)(de)(de)支撐(cheng)架(jia)(jia)孔(kong)(kong)，用(yong)(yong)于(yu)安裝支撐(cheng)架(jia)(jia)、斜撐(cheng)和聯板(ban)；橫(heng)梁(liang)夾(jia)具孔(kong)(kong)用(yong)(yong)于(yu)安裝橫(heng)梁(liang)夾(jia)具。下(xia)弦桿上設有4塊橫(heng)梁(liang)墊板(ban)，墊板(ban)上有栓釘，用(yong)(yong)于(yu)限定(ding)橫(heng)梁(liang)的(de)(de)(de)位(wei)置。