Research On Several Key Problems Of Construction Control And Construction Process Of Honghe Bridge

As the main structural form of long-span bridges,cable-stayed bridges have been widely used,and composite beams have become one of the common forms of main girder of cablestayed bridges because of their high strength,high stiffness,and good ductility.Compared with a cable-stayed bridge using a single material,a composite-beam cable-stayed bridge is more complex and more difficult to construct,so it is of great practical significance to study the control of the whole construction process and the optimization of construction methods.Based on the engineering background of Zhuhai Honghe Bridge,this paper analyzes its construction process and construction methods,and the specific research contents are as follows:(1)The finite element model of the whole bridge is established by using Midas Civil,and it is used to simulate and analyze the main channel bridge of Modaomen Channel.Combined with the method of minimum bending energy,and considering the control conditions of each component comprehensively through the influence matrix,a set of reasonable bridge cable forces can be solved simply by using the function of "unknown load coefficient" and cable force adjustment function of the software.At the same time,the modification method of elastic modulus of cable of steel strand is analyzed and the general formula of elastic modulus modification of multi-wire steel strand is deduced.Through the research on the influence of the modification of the elastic modulus of the cable,it is concluded that the elastic modulus of the cable is the main influencing parameter in the construction process control of the large span composite beam cable-stayed bridge.The modification of elastic modulus of strand cable should be considered in the simulation calculation of large span cable bridge with parallel strand cable.(2)The construction scheme of the diamond-shaped main tower with the 8# pier in the transverse direction is expounded in detail.The calculation and analysis of the temporary transverse tension rods and struts in the construction of the main tower show that the temporary tension rods and struts can effectively reduce the tensile stress and prevent the concrete tower column from cracking.It is necessary to avoid great changes in the field temperature during use and demolition stage because the temperature has a great influence on the transverse struts force of steel tube.The temporary transverse struts itself is a slender compression rod,and the concrete at the end of the transverse struts meets the local pressure-bearing state.The results show that the strength of the transverse struts and the local bearing surface of the concrete meet the safety requirements when the stability of the transverse struts and the local bearing capacity at the end of the transverse struts are calculated and analyzed respectively.(3)The cumulative calculation expression of the fabrication and installation errors of the beam section is deduced by establishing the relative coordinate system,and the influence of the assembly errors on the profile and internal forces of the closure and the bridge is calculated and analyzed based on this,and it is concluded that it is very necessary to control the assembly errors in the construction process.The relationship and difference between the installation profile and the installation elevation are studied,and a "relative height difference method" to control the elevation of the steel beams during the assembly process is proposed.The adjustment measures of the closure error are elaborated in detail,and a temporary lock closure technology is proposed.The closure efficiency can be improved,the difficulty of closure can be reduced and the safety of bridge structure can be guaranteed by observing the closure state in advance,adopting the tool plate welding to temporarily lock the closure state,and immediately removing the temporary anchorage of tower beam after closure.(4)The construction method of three-segment composite beam on pier top without support on the 8# pier is studied.The key technical point of this method is that a piece of equipment is required to assemble a beam crane on segment No.0,and the assembled beam crane can rotate safely on segments No.0 and No.1.In this method,the measures of asymmetrical initial tensioning of No.1 cable can effectively reduce the construction risk and improve the stress condition of the steel beam.It can play a guiding role in site construction by calculating the key points of its technology.