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采用无支架施工的大跨径双曲拱桥,一般在拟定拱肋截面尺寸时,拱肋高度h由纵向稳定计算确定,拱肋宽度b由横向稳定计算确定。根据《公路双曲拱桥设计施工技术规范(试行)》第7条规定,h≮(0.009～0.012)l,b≮(0.6～1.0)h,式中l为拱肋跨径。选用上述式中的系数是当跨径较大时取较小值,跨径较小时取较大的系数值。目前除了具有强大吊装设备的专业施工队伍外,一般桥梁工地的吊装能力仍然有限,即构件的吊装重量受到限制。类此情况,设计无支架施工的双曲拱桥,选择h和b时,取用的系数值尽管仍在上述规定范围内,也往往不能满足规范规定的稳定要求,尤其是拱肋宽度b由于选用较小的系数值而使横向稳定安全系数大为减小。在这种情况下,采用单肋分段吊装合拢成拱的方式,依靠加大尺寸就会增加吊装困难,同时也不经济。除
In the case of large-span double-curved archless bridges with unsupported construction, the height h of the arch rib is usually determined by the longitudinal stability calculation and the width b of the arch rib is determined by the transverse stability calculation. According to Article 7 of “Technical Specifications for Design and Construction of Double Curved Arch Bridge for Highway (Trial)”, h ≮ (0.009 ~ 0.012) l, b ≮ (0.6-1.0) h, where l is the span of the arch rib. Use the coefficients in the above formula is when the span is larger, take a smaller value, when the span is smaller, take a larger coefficient value. At present, except for the professional construction team with strong lifting equipment, the lifting capacity of the general bridge site is still limited, that is, the lifting weight of the components is limited. In this case, the design of unsupported construction of double curved arch bridge, choose h and b, access to the value of the coefficient although still within the above-specified range, often can not meet the requirements of the norms of the stability requirements, especially rib width b due to selection Smaller coefficient values make the transverse stability safety factor greatly reduced. In this case, the use of single-ribbed hoisting arch approach, relying on increasing the size will increase the lifting difficulties, but also uneconomical. except