Research On Construction Control Technology Of Long-span Cable-stayed Bridge With Steel Box Girder

Modern cable-stayed bridges have the advantages of beautiful appearance,high structural stiffness,the axial force in self-anchored system and so on.In terms of long-span bridge scheme selection,cable-stayed bridges have stronger competitiveness.Due to the influence of some uncertain factors,such as temporary load,construction technology,construction monitoring and so on,it will inevitably lead to the deviation between the actual bridge state and the design state,and even endanger the safety of the structure during the construction of cable-stayed bridge.The cable-stayed bridge is a high-order statically indeterminate structure.With the increasing of span and the cross-influence of various factors,it is necessary to strictly control the construction of cable-stayed bridge so that the safety and the advance smoothly of bridge construction,as well as the state of bridge meeting the design requirements can be ensured.Based on the actual project,this paper makes a systematic study on the reasonable state of the long-span steel box girder cable-stayed bridge,the installation control,parameter identification,linear predictive control and cable force adjustment of the steel box girder in construction.The main works and research results are as follows:(1)Research on the reasonable completion of Cable-Stayed Bridge.The final goal of construction control is to make the cable-stayed bridge in a reasonable state.How to determine a group of cable forces to make the cable-stayed bridge in a reasonable state is the key problem in the design.Based on the function of Midas civil unknown load coefficient,taking cable force as design variable and key node displacement as constraint condition,the initial cable force which meets the constraint condition is calculated,and at the same time,the influence matrix of calculation model is got.Using the optimization solution function of Excel,the cable force of the cable-stayed bridge is optimized on the basis of influencing matrix and with the goal of the minimum bending moment of the whole structure,which makes the final cable force distribution of the cable-stayed bridge tends to be uniform.The main beam,the main tower and other key component force is in a reasonable state,and themain beam line meet the design requirements,that is,the cable-stayed bridge is in a reasonable state of completion.(2)Research on reasonable construction state of Cable-Stayed Bridge.On the basis of reasonable state of the bridge,the non-stress state control method is adopted to establish the connection between the construction status and the bridge state.The reasonable construction state is the state of the stress and deformation on each construction stage.Then on the basis of the reasonable construction state,the key parameter of the tension of the cable at each stage and the elevation of the cantilever end is calculated.Finally,the rationality of the construction stage is verified by comparing the completed construction state with the target completion state,and the results show that the construction completed bridge is highly consistent with the reasonable bridge completion state.(3)Research on construction control system of Cable-Stayed Bridge.Based on the modern control theory and adaptive control thought,the construction control system of a cable-stayed bridge is established in view of the many factors affecting the construction of the cable-stayed bridge,which includes construction control management subsystem,structure state monitoring subsystem and construction site control subsystem.The field control subsystem includes simulation analysis,parameter identification,error analysis,state prediction,comprehensive adjustment and so on.(4)Research on construction control technology of steel box girder.The hoisting construction scheme and monitoring and measuring scheme of steel box girder are established.Based on the designed bridge line type of the cable-stayed bridge,and according to the theoretical value of the main girder line and the length of the main girder,the manufacturing length of main beam section and the compensation amount of beam length are calculated to determine the material length of main beam without stress.At the same time,the calculation results of manufacturing line,the calculation method of beam end rotation angle and the adjustment method are given.(5)Research on construction process error of cable stayed bridge.Based on geometric control theory,the sensitivity of structural parameters is analyzed and sorted by Midas civil.On this basis,the neural network model is established by using BP neural network algorithmand MATLAB.The main beam displacement during construction is taken as input sample data,and the network is trained with the parameters to be identified as output data.Using the trained network to identify the parameters of the construction stage,and then to modify the calculation model,according to the temperature of the environment during the installation of the cable-stayed bridge during the construction,the inclination angle of the stay cable,The distance from the beam section to the axis of the main tower is used as the input parameter of the network.By predicting the errors between the theoretical elevation of the main beam and the measured elevation,the prediction of the erection height of the main beam in the next construction stage is realized.Using the influence matrix method,the cable force adjustment is calculated by multiple iterations.