罕台川特大桥优化设计

Optimal Design of Hantaichuan River Bridge

罕台川特大桥跨越罕台川,同时上跨包神和包西2条电气化铁路。为了解决该桥原设计(三跨连续梁)存在的分段悬浇施工周期长、对铁路的运营干扰大,大直径长桩成孔困难、工期长且桩质量不易得到保证,实体墩自重大、不利于抗震、承载力要求高等问题,对原设计做了如下优化:将中跨跨中35 m梁段改为钢-混结合梁,采用工厂化制作、现场吊装法施工;将实心墩改为矩形空心墩(主桥)及双方柱框架墩(引桥)。对优化后的桥梁结构进行地震作用下墩底内力计算及地震作用动力弹塑性验算,结果表明,按照承载能力极限状态基本组合计算的桥墩承载力和稳定性均满足要求,桥梁结构满足抗震规范要求。

The Hantaichuan River Bridge spans the Hantaichuan River and also two electrified railways from Baotou to Shenmu and from Baotou to Xi＇an.To resolve the problems in the original design（a 3-span continuous girder） of the bridge,such as the long construction cycle of cantilever segmental concreting of the girder and the considerable interference of the construction with operation of the railways;the difficult boring of large diameter and long piles for the foundations,the long construction time schedule and the uneasy guarantee of quality of the piles;the heavy weight,unfavorable seismic resistance and demanding bearing capacity of the solid piers,the original design was therefore optimized as follows： the 35 m long girder section at the midspan of the central span was changed into a steel and concrete composite girder section which would be fabricated in shop,lifted and installed in field.The solid piers were changed into the rectangular hollow piers（for the main bridge） and double square column frame piers（for the approach bridges）.The internal forces in the pier footings of the optimized structure under the action of earthquake were calculated and the dynamic elasticity and plasticity of the structure were checked.The results of the calculation and checking indicate that the calculation of the bearing capacity and stability of the piers in accordance with the basic combination of ultimate state of the bearing capacity can accord with the relevant requirements and the structure can satisfy the requirements for seismic resistance as well.