Analysis of Mechanical Behavior of a Presressed Concrete Open-Web Continuous Rigid-Frame Bridge in Construction Process

The main bridge of Beipan River Bridge is a prestressed concrete open-web continuous rigid-frame bridge with span arrangement(82.5+220+290+220+82.5) m.The lower chord of the triangle area of the bridge was concreted by the form traveler by the aid of fastening stays,the upper chord was concreted in situ on scaffolding supported on the top of the lower chord and the successive segments of the main girder were cantileveredly concreted also by the form traveler.To study the mechanical behavior of the bridge in the construction process,the finite element model of whole bridge was established and the load cases of tensioning and removing of the temporary fastening stays,tensioning of prestressing and construction of the successive segments were calculated and analyzed.The results of the calculation and analysis show that owing to the influence of concreting of the segments and tensioning of the fastening stays and prestressing,the stress in the part of the scaffolding supporting the upper chord is concentrated,the variations of cable forces in the fastening stays in the triangle area are not great and basically become less and less with the proceeding of the construction.After the closure of the central span is completed,the influence of removing of the scaffolding on the force conditions of the main girder and slant legs is not much and the removing of the fastening stays effectively reduces the peak values of the stress in the girder and legs.