Analysis And Research On Design Parameters Of Open-web Prestressed Concrete Continuous Rigid Frame Bridge

Open-web prestressed concrete continuous rigid frame bridge,with oblique legs set on the box girder at the pier position,improves the rigidity of the pier-beam consolidation area.Through hollowing out the web of the box girder near the pier,the mechanical properties of the beam-arch combination are formed,and the spanning capacity of the beam bridge is improved from the force.In addition,this new type of bridge is very suitable for the cantilever construction method,which has been relatively mature at present.The construction cost is low,and it has important development significance in the beam bridge.The beam height at different positions and the design of curve form have great influence on the mechanical safety and project economy of such open-web rigid frame structures.Through the finite element simulation analysis of the structure,the optimization research of the structural design parameters can verify the rationality of this new type of bridge from the theoretical level and obtain a reasonable design scheme,which is of great significance and needs further study.The main research contents and conclusions of this paper are as follows:(1)In this paper,the stress characteristics of PC continuous rigid frame bridge are introduced in detail,and through a large number of statistical investigation and research,the research status and existing problems of key design parameters of this type of bridge are summarized;(2)Multi-parameter comprehensive analysis of parabola number at the bottom of beam,the height of lower chord beam and the total beam degree at the top of pier is conducted.The results show that the number of parabola at the bottom of the beam and the height of the lower chord have significant effects on the total price of materials,and the number of parabola at the bottom of the beam has the greatest impact on the total price of materials.Therefore,it is necessary to attach great importance to the influence of the power of the curve at the bottom of the beam on the economy of such bridges,to determine reasonable design parameters and to improve the economic performance of structures;(3)For this type of bridge,it is most reasonable to adopt the design scheme that the total girder height at the root is L/8,the parabola number at the bottom of the girder is 2.75,and the lower chord girder height is L/50;(4)The results show that the open-web rigid frame can be used in the span range of 200m～360m.When the span is fixed,the amount of concrete needed decreases with the decrease of the total beam height at the top of pier,but the amount of prestressing steel bar needed increases with the decrease of the total beam height at the root.The change curve of total material cost shows an upward trend.When the total beam height is about L/7～L/9,the total material cost is the lowest;(5)The larger the ratio of midspan height to span is,the more disadvantageous the structural force is.In the design of such bridges,the smaller the ratio of midspan height to span should be selected within a reasonable range.(6)The study of fasting inclination shows that when the fasting opening height is 33 m,30.75 m,29m and 27 m respectively,the reasonable angles are 53.75 degrees,55.63 degrees,57.20 degrees and 59.03 degrees,respectively.When the hollow closure point is 45 m to the center of pier,the force acting on this type of bridge is more reasonable.