Study On Cable Force Optimization And Dynamic Behavior Of Asymmetric Concrete Filled Steel Tubular Pylon Cable-Stayed Bridge

Special-shaped cable-stayed bridge is a kind of bridge type in which the components of cable-stayed bridge show special characteristics compared with traditional cable-stayed bridge,such as inclined tower,heterogeneous bridge,asymmetric span,special cable arrangement and so on.With the transformation of China’s economic development from high speed to high quality,and the improvement of people’s pursuit and yearning for a better life,special-shaped cable-stayed bridge has been favored by bridge designers and builders because of its beautiful shape,easy to combine with local scenery,cultural factors,strong visual impact and so on.However,as the construction of special-shaped cable-stayed bridges in China is much later than that in foreign countries,the relevant research is not sufficient,especially reflected in the research of various scholars in the direction of special cases of bridges or special cases of materials,sections and so on.On the other hand,the " SPECIAL " of special-shaped cablestayed bridges are different from each other,so it is difficult to form a unified standard for reference.Therefore,it is of great importance and necessity to enrich the research samples of this kind of bridge and explore the calculation and analysis methods suitable for this kind of bridge.This paper takes the main bridge of Huaihe River Bridge in Xixian County,Henan Province(asymmetrical,inclined concrete filled steel tube tower cable-stayed bridge)as the engineering background,based on the field measured cable force and relevant codes,this paper makes an in-depth study on the key contents in the calculation and analysis of cable-stayed bridges: the completion of the bridge and the optimization of construction cable forces.In addition,considering the importance of cable force measurement and control during construction,a Python program is compiled to analyze the cable vibration equations under different boundary conditions by using the measured cable frequency.The main research contents are as follows:(1)Through the solution of the reasonable completion state of an example bridge with the bridge engineering finite element analysis software Midas civil,it is found that the existing analysis methods for the reasonable completion stage of cable-stayed bridges(rigid braced continuous beam method,zero displacement method and minimum bending energy method)show a certain degree of inapplicability to special-shaped cable-stayed bridges with asymmetric and inclined towers.Therefore,this paper presents a comprehensive cable adjustment method of "first solving the preliminary reasonable cable force by using the minimum bending energy method,and then fine-tuning the cable force with Midas civil software".After comparative analysis,the cable force calculated by this method makes the stress and alignment of each part of the bridge better meet the requirements of the code and fit the engineering practice.(2)First of all,through the theoretical analysis,the analysis method of the reasonable construction state of each cable-stayed bridge including the process of "upside-down" cannot avoid the inconsistent cable force in the stage of bridge completion,that is,the problem of "nonclosure" of the bridge.Then the construction stage of the example bridge is analyzed by using the formal assembly iteration and the stress-free iteration which does not include the upsidedown process.After three and four iterations respectively,the calculation results of the two methods,that is,the stress and alignment of the bridge in the important construction stage can meet the requirements of the code and construction,but the alignment of the inclined tower calculated by the non-stress state method is better than the formal iteration method.(3)The program for solving the transcendental equation is compiled by using Python software.Combined with the cable frequency measured in the field,the vibration transcendental equation considering the bending stiffness and sag effect of the cable is solved under three boundary conditions(two ends hinged,two ends consolidated,one end hinged,and one end consolidated).The results show that for the application analysis of the vibration method of this kind of special-shaped cable-stayed bridge,the calculation results which are more suitable to the reality can be obtained according to the vibration equation selected according to the actual construction procedure of the cable.In this paper,as an example,the construction procedure of bridge-type cable-stayed cable is "first fixed on the bridge tower,then tensioned on the beam",so the vibration equation under the condition of one end hinged and one end consolidation has obtained better calculation results,and the cable force error rate is less than 10% under the actual working condition,while the calculation results of two end consolidation and two end hinged vibration equations deviate from the reality.