Research On Construction Control Technology Of Low Tower Cable-stayed Bridge

The short-pylon cable-stayed bridge is a new bridge form between the cable-stayed bridge and the continuous beam bridge.Its shape is similar to that of cable-stayed bridge,both of which have pylons and cables.However,the biggest difference between the low-pylon cable-stayed bridge and the cable-stayed bridge is that the pylons of the low-pylon cable-stayed bridge are lower.In addition,the ratio of the side span to the middle span and the stiffness of the main girder are relatively large.At the same time,compared with the general bridge,the short tower cable-stayed has the characteristics of advanced technology,graceful shape,slender structure system and so on,which has been widely used.In order to make the actual state of the bridge structure as close as possible to the theoretical design state,ensure the safety of the overall structure of the bridge and reduce the deviation caused in the construction process,it is of great significance to study the construction control theory.Based on the Chongzuo bridge in Guangxi,combined with the construction control theory and method of short-pyloned cable-stayed bridge,this paper simulated and analyzed the construction and operation status of the whole bridge by using the numerical simulation software MIDAS/Civil,and analyzed the displacement and stress changes of beams,0 # blocks and hanging baskets in the construction process and operation stage of the short-pyloned cable-stayed bridge.The construction monitoring scheme and control measures of low tower cable-stayed bridge are put forward.(1)The construction control theory of bridge is expounded,and the construction control system of low-pylon cable-stayed bridge is proposed from the aspects of geometric alignment,stress control,cable force control and stability.(2)The chongzuo bridge,in Guangxi province,was taken as the research object.The numerical simulation analysis model of chongzuo bridge was established by MIDAS/Civil,and the displacement and stress changes of the main beam,block 0 and hanging basket of the low-pylon cable-stayed bridge were analyzed.The vertical deformation of the main girder and the longitudinal displacement of the cable tower meet the requirements.The stress of the main girder and the stress of the main tower in the construction process is calculated and analyzed according to different working conditions,and the results all meet the requirements.The cable force of the bridge is calculated.By comparing the measured value of cable force with the theoretical value,it can be seen that the cable force error is within 2%,and the maximum cable force error is-1.98%,which meets the requirements of the specification.The maximum tensile stress of no.0 roof is about 0.4mpa,and the maximum compressive stress of no.0 roof is about2.3mpa.The maximum stress of the hanging basket was 164.1mpa under the condition of working condition 3,and the structural strength met the requirements.(3)The construction control and monitoring scheme of chongzuo bridge was determined,and the cable force monitoring data of the main girder,stress and cables of the bridge were compared and analyzed,and the control work was introduced in detail.Through the analysis of the control data,it can be found that the measured values of the alignment,stress and cable force of the main girder of the bridge differ little from the theoretical values,which meet the requirements of the construction specifications.The biggest difference between the calculated value and the theoretical value of the deflection of each beam section of the main beam occurs in the tension completion phase of the J6 stay cable,and the difference value is 6.6mm,which is less than the 10 mm required by the specification.The displacement of the tower top in each construction stage of the bridge is well controlled.The deviation displacement of the cable tower is well controlled,which is in agreement with the calculated value.There is a process of increasing the difference between the measured stress and the theoretical stress of the concrete main beam.The maximum value of the cable force test of chongzuo bridge is 4624 k N,and the maximum error between the measured value and the theoretical value is 6.46%,which meets the requirement of the cable force error in the specification.(4)The sensitivity of the main parameters affecting the construction control error of the bridge is calculated,among which the main parameters are the stiffness of the main beam,the stiffness of the stay cable,the bulk density of the main beam,the temperature,etc.,and the sensitivity of the above parameters is compared.The dead weight of the main beam has the greatest influence on its linear shape.When the dead weight increases by 10%,the linear shape changes to 30.755 mm.The second is the influence of temperature.When the temperature increases by 20?,the linear change is 11.76 mm.Temperature has the greatest influence on the stress.When the temperature increases by 20?,the bottom plate of the main beam bears the maximum compressive stress and tensile stress at the same time,among which the compressive stress is 14.56 mpa and the tensile stress is 1.696 mpa.The deflection of the top of the tower caused by the main parameters is small.The stiffness of the cable has the greatest influence on the stress of the cable tower.The influence of the main parameters on the stress of the cable tower and the cable is similar and small,which can be ignored.The stiffness of the main girder has the greatest influence on the cable stress,with the maximum stress of 913.50 MPa and the minimum stress of 703.01 MPa.By means of least square method,the dead weight of main girder and the initial tension of cable are corrected,and the results are very close to the actual structure.This paper has 57 pictures,34 tables,52 references.