Study On Construction Technology Of Main Arch Structure And Construction Technology Of 300m Cantilever Pouring Arch Bridge

The reinforced concrete arch bridge constructed by cantilever casting method has good structure integrity,strong terrain adaptability,good durability,low maintenance cost in the later stage,and is suitable for the mountainous terrain without construction site.It been competitive in the arch bridge with a span of 200m～300m,and the largest span built in China is 240 m at present.With the continuous increase of arch bridge span,the section and segment weight of arch ring increase,which not only increases the load bearing requirements of anchor system,but also puts forward higher requirements for arch ring alignment and stress control.Therefore,this dissertation relies on technology projects “key technology of design and construction of 300 m grade cantilever cast reinforced concrete arch bridge” of Chongqing education commission,the main research contents are as follows:(1)Based on the theory of elastic thin plate theory and equivalent compression column of arch,taking the reasonable order of arch destruction: strength destruction →whole destruction → local destruction as the objective,the calculation formulas of critical width,critical height and critical plate thickness of main arch ring of concrete arch bridge are deduced,and the correctness of the formulas been verified by numerical analysis method,which provides theoretical basis for arch ring design of long-span concrete arch bridge.(2)A new type of box section with longitudinal ribs on the top and bottom plate been proposed in view of the large weight of the arch ring and the poor local stability of the top and bottom plate of the single box and single chamber section.Under the premise of keeping the box cross-sectional area unchanged,through the local stability analysis of the top and bottom plate of the arch ring under different longitudinal rib heights,the reasonable value of longitudinal rib heights been obtained.According to the stress characteristics of the top,bottom and web plate of the arch ring,the structural design concept of "high section,thin top and bottom plate and thick web plate" was put forward.The advantages of this concept were verified by theoretical derivation and numerical analysis method.(3)By using the calculation formula of main arch structure deduced in this dissertation,the section size of the main arch of 300 m reinforced concrete arch bridge been worked out,and the design parameters such as the ratio of arch to span,the arch axis coefficient and the building form on the arch analyzed,and the bearing capacity and stability of the whole bridge are checked according to the existing design codes.(4)The cantilever pouring construction of 300 m reinforced concrete arch bridge been analyzed.The deformation,stress and anchor cable forces of the main arch ring in the whole construction process are calculated by using the method of "double control of stress and alignment".The stress characteristics of the new type box section with longitudinal ribs and the single box and double chamber section in the construction process were compared and analyzed to further verify the rationality of the new type box section.