The Key Construction Technology On Double Composite Continuous Box-girder Bridge By Pre-jacking Method

Continuous double steel-concrete composite beam is a new structural system developed on the basis of common steel-concrete composite beam. Although it has gotten stronger and stiffer than the common composite beam, the tension cracks will occur at the top concrete slab in the negative moment region. Therefore, controlling concrete slab crack width in a continuous double composite beam is a significant content in the bridge construction process. That is controlling the stress state of concrete slab.Controlling concrete slab crack width by pre-stressed concrete method has some disadvantages in composite bridge construction practice. Jacking-up and landing bearing supports method will be applied to the double composite girder bridge construction and its structural mechanical behaviors in the whole process will be simulated in this dissertation. The main contents are concluded as follows:(1)It is described that the present research situation of composite beam at home and abroad and several common methods of applying pre-stressed on composite beam are introduced.(2)The principle of applying pre-stressed on composite structure by jacking-up and landing bearing supports are introduced. The analysis of the stress state and deformation of composite beam during the whole construction process and serviceability stage is carried out through building general calculation model. The obtained results are analyzed and evaluated.(3)The whole construction process can be completely monitored through analyzing the finite element model of software ANSYS. The reasonable range of jacking-up is obtained with the comparison of the result of different jacking-up values.The result of theoretical calculation and numerical simulation shows that, it is improved that the stress state of the top concrete slab in the negative moment regions by pre-jacking bearing supports method; the stress of concrete slab shifts from tensilestress to compressive stress. By comparison, the theoretical calculation is relatively conservative; the result of the finite element software is close to the actual situation.The result of theoretical calculation can be taken to control the whole construction process, being on the safe side, when applying pre-stressed by Jacking-up and landing bearing supports method.