Analysis Of The Scheme For Removing The Prestressed Concrete Continuous Girder Bridge's Scaffolds

Full support method is a method which is widely used in Passenger dedicated line and urban bridge construction.But the study is less which is specifically for stent removal.This paper is based on a Railway prestressed concrete continuous girder bridge.The bridge along the length direction is from high to low The constructor plan to use the high ground to make a soil model under the original construction plan,the other two span set up the scaffolds.Obviously,the general method of scaffold removal is obviously not applicable to the situation in this paper.In order to verify the safety of the scheme of the scaffold removal,the main work of this paper includes the following aspects:(1)During my practicing in a construction site,I have collected the construction drawings and construction documents of the continuous girder bridge.And I also have some insight into the scheme of the scaffold removal and the construction points,and summed up the 4 extreme conditions which may occurred in the dismantling process.(2)Through looking up norms and reading a large number of relevant literature,I summarize the index which influence the safety of the scheme of the scaffold removal.(3)According to the construction drawings,I choose the MIDAS/Civil beam grid modeling assistant to establish the 3 * 32 m continuous girder model,in which the beam element is used to simulate the beam,the equivalent load method is used to simulate the effect of prestressed steel,and the elastic support nodes are used to simulate the soil form and support role.(4)By changing the boundary conditions of the model to simulate various conditions,I obtain the stress,deflection and bearing force of girder under different working conditions.After the calculation results of several working conditions are collated,compared,analyzed and compared with the standard requirements.Aiming at the most unfavorable working conditions,some countermeasures and prevention methods should be put forward.Through the results analysis,the following main conclusions are obtained:(1)The side span(the left cross)'s transverse inhomogeneously digging out the soil model will cause a greater principal tensile stress on the edge of the region's middle and cause the Counter force's redistribution in the abutment 1.The difference of the support's counter force in which side that had removed the soil model and the side which had removed the soil model in the same time is a little great that may cause the bearing and the beam's separation.While it also caused large deflection that are detrimental to the construction safety.So when we remove the left cross ground,the soil model must be removed transversely symmetry and monitor the side of the left across where may occur tensile stress.(2)When the soil model is not removed,the compressive stress of removing the right side span and the mid span's scaffolds in the same time is smaller than removing the mid span's only.According to this rule,the midspan can be removed first and then removed.(3)As long as the left side span 's transverse homogeneously digging out the soil model,the bridge are all under the pressure state,that meets the safety requirements.If the constructor still use the original construction scheme,I recommended that the middle and right across drop first,and then the left cross soil using transverse symmetrical drop.Aiming at the upper deflection of the span without removing the scaffolds,the temporary load can be used to reduce the upper deflection before the landing.