Optimization Design Of Asymmetrical Continuous Rigid Frame Bridge Basis On The Margin Of Safety

Topographical feature of the western region is mountainous and the relief is also excessive.So "U" or "V" shaped canyons are very common.Based on the typical topography,structurally asymmetric bridges are preferred to be the best bridge type choice.Asymmetric bridge can effectively reduce the damage to the ecological environment and reduce the cost of the project.To carry out more research on the asymmetric bridge,this paper relies on an asymmetric continuous rigid frame bridge.On the basis of structure force,the paper focuses on the optimization calculation.The main researches are as follows:(1)Do plenty of investigations about current situation of asymmetric bridge construction abroad ? current optimization algorithm ? characteristics of asymmetric continuous rigid frame bridge and so on.(2)Analyzing mechanical behavior of asymmetric rigid frame bridge.The mechanical behaviors of main beam and end reaction are studied when asymmetrical cross-stride.The end reaction result shows that when design an asymmetric rigid frame bridge,astride proportionality coefficient should be controlled in 0.4 or it's easy to emerge tension at the position of fulcrum.The conclusion of mechanical behaviors of main beam is that with the decrease of astride proportionality coefficient,main beam stress value tends to increase.And the value increase more around astride proportionality coefficient of 0.4.Study on the symmetrical main beam with asymmetric piers shows that with any one pier's height reduced,all pier top moments increase.(3)Relying on the construction internal force analysis,the maximum positive moments are beard near the closure sections and the value is also different between the bigger side span and the smaller one.The root negative moments are also different from the envelope condition.That means main beam is symmetrical discontinuity.(4)Analyzing the safety performance of the structure Ultimate flexural?shearing strength of the diagonal section and torsion resistance checking calculation under the limit state of bearing capacity is carried.And the results show the project's carrying capacity can meet the specification requirements.Crack checking calculation under the limit state of serviceability shows the serviceability state can also meet related requirements.Margin of safety is defined to compute security reserves of structurebearing capacity.(5)On the basis of the control principle,optimization calculation of prestressed steel beams on asymmetric continuous rigid frame bridge is carried out.According to the calculation,the total strand bundle savings are 17702.4m and 19490.34 KG weight.When the girder web is an overall reduction 10 cm,bearing capacity and stress in use phase can all meet the requirements.But the amount of safety margin of carrying capacity of the structure is reduced.After optimization calculation of main beam alignment,the root of the smaller T part can have a reduction of 120 cm and the bigger one is 33.8cm.After the optimization calculation we know,the best scheme of asymmetric continuous rigid frame bridge is: the larger and smaller T parts of main beam have a reinforcement asymmetrical design and two T parts' box beam alignment using different times of the parabola.