鋼(gang)橋(qiao)桁(heng)(heng)(heng)架(jia)(jia)單元由上(shang)(shang)、下弦桿(gan)，豎桿(gan)和(he)斜撐(cheng)焊接(jie)而成。上(shang)(shang)、下弦桿(gan)的一(yi)端為陰(yin)頭(tou)(tou)，另一(yi)端為陽頭(tou)(tou)，在陰(yin)、陽頭(tou)(tou)上(shang)(shang)都有(you)銷子孔(kong)(kong)(kong)。兩(liang)節(jie)桁(heng)(heng)(heng)架(jia)(jia)拼接(jie)時(shi)(shi)(shi)，將一(yi)節(jie)的陽頭(tou)(tou)插(cha)入另一(yi)節(jie)的陰(yin)頭(tou)(tou)內，對準銷子孔(kong)(kong)(kong)，插(cha)上(shang)(shang)銷子。桁(heng)(heng)(heng)架(jia)(jia)各孔(kong)(kong)(kong)的用(yong)(yong)途如下:弦桿(gan)螺栓(shuan)孔(kong)(kong)(kong)用(yong)(yong)于(yu)拼裝(zhuang)雙(shuang)層(ceng)或加強(qiang)鋼(gang)橋(qiao)時(shi)(shi)(shi)，將桁(heng)(heng)(heng)架(jia)(jia)螺栓(shuan)或弦桿(gan)螺栓(shuan)插(cha)入弦桿(gan)螺栓(shuan)孔(kong)(kong)(kong)內，使雙(shuang)層(ceng)桁(heng)(heng)(heng)架(jia)(jia)或桁(heng)(heng)(heng)架(jia)(jia)與加強(qiang)弦桿(gan)連接(jie)起來；支(zhi)撐(cheng)架(jia)(jia)孔(kong)(kong)(kong)用(yong)(yong)來安裝(zhuang)支(zhi)撐(cheng)架(jia)(jia)，當桁(heng)(heng)(heng)架(jia)(jia)用(yong)(yong)作主梁時(shi)(shi)(shi)，用(yong)(yong)中間(jian)(jian)兩(liang)個孔(kong)(kong)(kong)，用(yong)(yong)作橋(qiao)腳(jiao)時(shi)(shi)(shi)，用(yong)(yong)端部兩(liang)個孔(kong)(kong)(kong)，以(yi)加強(qiang)兩(liang)排桁(heng)(heng)(heng)架(jia)(jia)間(jian)(jian)的聯系；風構孔(kong)(kong)(kong)用(yong)(yong)于(yu)連接(jie)抗風拉(la)桿(gan)；端豎桿(gan)上(shang)(shang)的支(zhi)撐(cheng)架(jia)(jia)孔(kong)(kong)(kong)，用(yong)(yong)于(yu)安裝(zhuang)支(zhi)撐(cheng)架(jia)(jia)、斜撐(cheng)和(he)聯板(ban)；橫(heng)梁夾具(ju)孔(kong)(kong)(kong)用(yong)(yong)于(yu)安裝(zhuang)橫(heng)梁夾具(ju)。下弦桿(gan)上(shang)(shang)設有(you)4塊橫(heng)梁墊板(ban)，墊板(ban)上(shang)(shang)有(you)栓(shuan)釘，用(yong)(yong)于(yu)限定(ding)橫(heng)梁的位置。