Research Of Construction Monitoring For Continuous Steel Truss Girder Cable-stayed Bridge

The Yellow River highway-railway bridge in Zhengzhou is an extra-large one used for both Shiwu railway passenger dedicated line and the assistant highway of the new 107 national road, which has two-track passenger dedicated line and 6 lane highway and adopts the method of separately arranging the highway and railway on the upper and lower decks. The steel truss girder of main bridge is divided into two units, the first-unit of which is a continuous steel truss girder with span arrangement 1080m, and with six pylons. And the second-unit is a continuous steel truss girder with span arrangement 601.9m. Taking the first-unit of main bridge as its engineering background, this thesis uses finite element software Midas/Civil to build the space finite element calculating model and check its construction program. According to the filed construction monitoring situation, I carry out the construction monitoring recheck on the whole process of incremental launching construction of the first-unit steel truss girder and conduct the monitoring work with its feedback. The following is the major work completed in this thesis and the main conclusions:First, a study on construction calculating of the main bridge of the Yellow River highway-railway bridge in Zhengzhou based on the finite element model:According to the first-unit structure of the main bridge, we simulate each member of main truss with space beam element and adopts the rigid arm to simulate the whole gusset plate's influence. Railway bridge panel is the orthotropic plate. With the plate element simulation, its in-plane and out-plane stiffness is calculated separately in both longitudinal and transverse directions. The finite element calculating model of the bridge is finally built, which will be beneficial to the later recheck calculation of the construction monitoring.Second, the first-unit of the Yellow River highway-railway bridge in Zhengzhou adopts the multiple-points incremental launching method to erect its main truss, which has much difficulty in the construction process. In addition, there is little relevant experience can be learned. Based on the multiple-points incremental launching method and the finite elements simulation of the whole process of construction, the present study gives a detailed analysis of potential dangers during the operating process. The calculating results indicate that it is feasible to erect the steel truss girder before the construction of highway deck, main pylon and stay-cable by using the multiple-points incremental launching method.Third, according to the assembling and incremental launching situation of the first-unit of the Yellow River highway-railway bridge in Zhengzhou, we implement a full monitoring recheck on the erection of the bridge. The rechecking results show that the monitoring measured value, the monitoring calculated value and the rechecking calculated value of the steel truss girder'elevation and stress are in consistent with each other. What's more, the stress of bar member and railway deck is within safety range throughout the whole process, which ensures the bridge's incremental launching in place smoothly. After the main truss folded, the linear and internal forces meet the design requirements, which also achieves the purpose of bridge construction monitoring recheck.