Mechanical Behavior Analysis For High Speed Railway Long-span Segmental Assembling Bridge In The Process Of Construction

Bridges of high speed railway mainly use simply-supported box girder structure. For more than 40 meters large span simply supported box girder bridge, the precast segmental assembly construction technology is used presently. Because of the complexity of the construction technology and the specific characteristics of equipment requirement, the technology started late and developed very slowly in China. Nowdays, for China high-speed rail is in the period of the golden development, to study and summarize the technology and related technology has very important practical significance. In this paper, in the background of Xi-Cheng passenger dedicated line Han jiang extra large bridge, and combined with the latest research achievements at home and abroad, the key technologiesthe of the whole construction process is simulated mechanically, analyzed and monitored actually presently, and the corresponding improvement measures are proposed.Assembly lion control is very important in the precast segmental assembly construction process, directly affecting the beam body’s shape. This paper analyses the main factors influencing the beam body line in construction process. The line control is divided into three stages: the precast segmental stage, the assembly stage, and the prestressed tension stage. Through the line control of the three stages, it can ensure that the beam assembly line meets the design requirements. MSS(Movable scaffolding system) is the main load-bearing structure in the whole construction process of assembling. The stress and the performance of the deformation of the beam directly influence the construction quality and the assembly line. Before the construction, the pre pressure test is conducted for MSS. Through the real-time measuring the flexural deformation of the control section and the stress of the main stress bars, analyzes the strength and the stiffness of MSS whether can meat the requirements of the biggest construction load. After the pretension is finished, the linear of bridge floor is mearsured. The mearsurment results show that the line control effect is good, can satisfy the requirements.Before the prestressed tensioning, through the booms, the whole beam body weight support MSS. With the prestressed tensioning, the beam body gradually begin to bear weight, the booms strength decrease at the same time,and MSS rebound. Because the beam body and MSS stiffness is uncoordinated, in order to avoid the top beam juncture crack which is caused by the beam body producing too much stress on the upper edge under the itself weight, the prestress and the derrick force, the stress of the beam body is analyzed in the tensioning process, to determine whether the suspension system is needed to unload or not, reducing MSS on the lift force of the beam body.Finally, using MIDAS Civil software analyze the shrinkage and creep effects of the 64 m segment assembling beam. Analysis compares the late creep effect of the segmental assembling beam and the whole precast beam. The analysis shows that the previous shrinkage and creep effects of the precast segment beams is litter than the integral precast beams’, while the latter deformation is more greater. At last, the factors affecting the aging deformation of concrete is analyzed respectively about the sensitivity of parameters. With the increase of the wet joint concret curing age or the second phase of pavement premature, the previous creep effect of structure is small, the later is relatively large. Besides, ambient humidity for Shrinkage effect of structure is also a sensitive control element.