金(jin)匱(kui)大橋(qiao),簡(jian)稱金(jin)匱(kui)橋(qiao)。現(xian)有(you)金(jin)匱(kui)橋(qiao)位于無錫市(shi)中心城區(qu)南長區(qu),為城市(shi)主干道太湖(hu)大道跨越(yue)京(jing)杭運河的一(yi)座橋(qiao)梁(liang)。原(yuan)金(jin)匱(kui)橋(qiao)為鋼筋混凝(ning)土(tu)剛(gang)架(jia)拱(gong)橋(qiao),由(you)于拱(gong)趾沉降(jiang)不均勻,現(xian)已限載通行(xing)。根據城市(shi)規劃,擬在舊橋(qiao)原(yuan)址(zhi)上重(zhong)建(jian)本(ben)項(xiang)目(mu)。改建(jian)后金(jin)匱(kui)橋(qiao)采用55m+105m+55m鋼桁(heng)架(jia)鋼箱(xiang)梁(liang)橋(qiao),橋(qiao)寬(kuan)46m,主跨跨越(yue)京(jing)杭大運河,邊跨跨越(yue)運河東路和運河西路。
金匱橋(qiao)地處太湖廣場,景觀要求(qiu)高,因(yin)此需(xu)要大橋(qiao)具(ju)有較強的標志性。大橋(qiao)橋(qiao)面(mian)較寬(kuan),既要滿足通航及(ji)運河東路(lu)凈空(kong)要求(qiu),又(you)需(xu)盡(jin)早落地進(jin)入兩端連接的隧道,故(gu)梁體高度應盡(jin)可能小。
在比選(xuan)了各種(zhong)橋型方案后,對于(yu)主跨為100m左右,橋寬46m的(de)橋梁,采用(yong)下承(cheng)式鋼桁(heng)(heng)梁可謂(wei)最佳(jia)選(xuan)擇。設計中創新地將(jiang)懸索橋造(zao)(zao)型與(yu)傳統鋼桁(heng)(heng)梁有機地結合,利(li)用(yong)主桁(heng)(heng)富于(yu)變化的(de)曲線,塑造(zao)(zao)出風格獨特的(de)鋼桁(heng)(heng)梁橋。
主(zhu)(zhu)梁(liang)采用(yong)(yong)開口式主(zhu)(zhu)桁(heng)與鋼箱梁(liang)相結(jie)合,此類結(jie)構在國內(nei)應(ying)用(yong)(yong)較少。開口式主(zhu)(zhu)桁(heng)由(you)于沒(mei)有橫(heng)聯與平(ping)聯,橋面(mian)(mian)(mian)視線更開闊,景觀效(xiao)果更好。但在汽車活載(zai)作用(yong)(yong)下,主(zhu)(zhu)桁(heng)上弦(xian)跨中桿件受壓(ya),容易(yi)發生整體(ti)(ti)失(shi)穩,對于跨度不(bu)大、桁(heng)高不(bu)高的鋼桁(heng)梁(liang),通過控制主(zhu)(zhu)桁(heng)上弦(xian)跨中桿件應(ying)力水平(ping),能(neng)有效(xiao)地解決主(zhu)(zhu)桁(heng)的整體(ti)(ti)失(shi)穩問題。對主(zhu)(zhu)桁(heng)桁(heng)數的選擇(ze),可采用(yong)(yong)3片主(zhu)(zhu)桁(heng),橋面(mian)(mian)(mian)系(xi)(xi)采用(yong)(yong)縱、橫(heng)肋(lei)加固的正(zheng)交(jiao)異(yi)性鋼橋板(ban)(ban)面(mian)(mian)(mian)體(ti)(ti)系(xi)(xi);也可采用(yong)(yong)2片主(zhu)(zhu)桁(heng),橋面(mian)(mian)(mian)系(xi)(xi)采用(yong)(yong)正(zheng)交(jiao)異(yi)性板(ban)(ban)鋼箱梁(liang)體(ti)(ti)系(xi)(xi),這兩種均能(neng)滿足通航凈(jing)空要求(qiu)。經(jing)多方面(mian)(mian)(mian)比較,采用(yong)(yong)2片主(zhu)(zhu)桁(heng)、橋面(mian)(mian)(mian)系(xi)(xi)為(wei)正(zheng)交(jiao)異(yi)性板(ban)(ban)鋼箱梁(liang)體(ti)(ti)系(xi)(xi)。