【作者】 王芳；

【导师】 韩冰；

【作者基本信息】 北京交通大学 ， 防灾减灾与防护工程， 2013， 硕士

【摘要】 在钢管混凝土构件中钢材与混凝土两种材料协同工作,使各自的优点得到充分发挥。目前,钢管混凝土拱桥在我国快速发展,并得到了广泛应用。不同于其他混凝土结构,钢管混凝土中核心混凝土在较早时刻即承担荷载,因此其早龄期徐变问题较为突出。本文基于BP-2模型和按龄期调整有效模量法,把核心混凝土的早龄期徐变影响等效为混凝土弹性模量的改变,推导出考虑施工步骤的钢管混凝土拱肋中核心混凝土早龄期徐变计算方法,并将钢管混凝土徐变计算方法和有限元方法相结合,建立了考虑早龄期徐变影响的钢管混凝土拱桥拱肋的有限元分析模型。对一座跨径125m钢管混凝土拱桥进行考虑施工步骤的计算,进行早龄期徐变影响的对比分析,认为早龄期徐变对钢管混凝土拱桥有不可忽略的影响。随后,采用三种矢跨比及不同的施工工序对钢管混凝土拱桥早龄期徐变进行对比分析,对比可知：(1)施工工序会影响成桥后的拱肋应力分布,先浇筑的混凝土应力水平大于后浇筑的混凝土；(2)拱肋混凝土的徐变对同一截面不同龄期的混凝土应力影响效应是不同的,先浇筑混凝土因应力水平较后浇筑混凝土大,故其因徐变引起核心混凝土上应力减少的现象更明显；(3)矢跨比越大的钢管混凝土拱桥,钢管混凝土早龄期徐变对拱顶位移及应力分布的影响越小；(4)采用不同的施工顺序对钢管混凝土拱桥早龄期徐变影响较为明显,选择合理的施工顺序对于钢管混凝土拱桥施工有重要意义。更多还原

【Abstract】 Concrete-filled steel tubular (CFT) arch bridges take the advantages of steel arch bridge and concrete arch bridges. In concrete-filled steel structures, the cooperative work of concrete and steel can make the best of both worlds. Because of the good performance, concrete-filled steel tubular arch bridges has a rapid development and is used widely now. Unlike other concrete structures, the core concrete of CFT structures bears load in the early age of construction, so the early-age creep effect is more obvious.Based on the creep calculating method the BP-2model, which is suitable to early age creep of concrete, and Age-Adjusted Effective Modulus Method, the early-age creep effects of the concrete core can be equivalent to the change of elastic modulus of concrete. This paper establishes an early-age creep effects model for CFT arch bridge by combining creep calculating method for axial compressed Concrete-filled steel tubular members with Finite Element Method. After calculating a CFT arch bridge, with a span of125m, it can be concluded that the early-age creep influence on CFT arch bridges is considerable and should not be ignored.Analysis of the influence of rise-span ratio and construction sequence on the early-age creep of concrete-filled steel tubular arch bridges are proposed in this paper.(1) Construction sequence has a influence on the distribution of arch rib stress, the stress of early casted concrete is bigger than lately casted concrete.(2)The creep of concrete of the same section but different age is not the same, the stress decrease phenomenon caused by creep of early casted concrete is severer.(3)In the bridges having a larger rise-span ration, displacement of the arch top and stress of concrete caused by creep is smaller. Considering the cost and beauty of arch, a1/5rise-span ratio is better.(4)Construction sequence has a great influence on the early-age creep of concrete-filled steel tubular arch bridges, so it is very important to choose a right sequence.更多还原