鋼橋桁架(jia)(jia)(jia)單元(yuan)由上(shang)(shang)(shang)、下弦(xian)桿(gan)(gan)，豎(shu)桿(gan)(gan)和斜撐(cheng)(cheng)焊接而成。上(shang)(shang)(shang)、下弦(xian)桿(gan)(gan)的一(yi)(yi)(yi)端(duan)為陰頭(tou)，另(ling)一(yi)(yi)(yi)端(duan)為陽(yang)頭(tou)，在陰、陽(yang)頭(tou)上(shang)(shang)(shang)都有(you)銷子孔(kong)(kong)。兩(liang)節(jie)桁架(jia)(jia)(jia)拼接時(shi)(shi)，將(jiang)一(yi)(yi)(yi)節(jie)的陽(yang)頭(tou)插入另(ling)一(yi)(yi)(yi)節(jie)的陰頭(tou)內，對準銷子孔(kong)(kong)，插上(shang)(shang)(shang)銷子。桁架(jia)(jia)(jia)各孔(kong)(kong)的用(yong)(yong)(yong)(yong)途如下:弦(xian)桿(gan)(gan)螺(luo)(luo)栓(shuan)孔(kong)(kong)用(yong)(yong)(yong)(yong)于(yu)(yu)拼裝(zhuang)雙層(ceng)或(huo)加強鋼橋時(shi)(shi)，將(jiang)桁架(jia)(jia)(jia)螺(luo)(luo)栓(shuan)或(huo)弦(xian)桿(gan)(gan)螺(luo)(luo)栓(shuan)插入弦(xian)桿(gan)(gan)螺(luo)(luo)栓(shuan)孔(kong)(kong)內，使(shi)雙層(ceng)桁架(jia)(jia)(jia)或(huo)桁架(jia)(jia)(jia)與加強弦(xian)桿(gan)(gan)連接起來；支撐(cheng)(cheng)架(jia)(jia)(jia)孔(kong)(kong)用(yong)(yong)(yong)(yong)來安裝(zhuang)支撐(cheng)(cheng)架(jia)(jia)(jia)，當桁架(jia)(jia)(jia)用(yong)(yong)(yong)(yong)作(zuo)主梁時(shi)(shi)，用(yong)(yong)(yong)(yong)中間兩(liang)個(ge)孔(kong)(kong)，用(yong)(yong)(yong)(yong)作(zuo)橋腳時(shi)(shi)，用(yong)(yong)(yong)(yong)端(duan)部兩(liang)個(ge)孔(kong)(kong)，以加強兩(liang)排桁架(jia)(jia)(jia)間的聯系(xi)；風構(gou)孔(kong)(kong)用(yong)(yong)(yong)(yong)于(yu)(yu)連接抗(kang)風拉(la)桿(gan)(gan)；端(duan)豎(shu)桿(gan)(gan)上(shang)(shang)(shang)的支撐(cheng)(cheng)架(jia)(jia)(jia)孔(kong)(kong)，用(yong)(yong)(yong)(yong)于(yu)(yu)安裝(zhuang)支撐(cheng)(cheng)架(jia)(jia)(jia)、斜撐(cheng)(cheng)和聯板；橫(heng)(heng)梁夾具(ju)孔(kong)(kong)用(yong)(yong)(yong)(yong)于(yu)(yu)安裝(zhuang)橫(heng)(heng)梁夾具(ju)。下弦(xian)桿(gan)(gan)上(shang)(shang)(shang)設有(you)4塊橫(heng)(heng)梁墊板，墊板上(shang)(shang)(shang)有(you)栓(shuan)釘，用(yong)(yong)(yong)(yong)于(yu)(yu)限(xian)定橫(heng)(heng)梁的位置。