| People’s cognition of things is gradually developed,which promotes the progress of technology,so does the development of modern bridge technology.Throughout the history of Bridges,it can be found that the design size of bridge structure becomes thinner and thinner with the development of bridge technology.Secondly,designers combine the existing basic bridge types and make use of the characteristics and advantages of each bridge type to develop a new combination system.In the design of bridges,due to the poor economics of traditional cable-stayed bridges and the large cross-section of prestressed concrete continuous beam bridges,a new type of bridge between cable-stayed bridges and continuous beam bridges has emerged,that is,low pylon cable-stayed bridge.Although its appeared is nearly 40 years later than the traditional cable-stayed bridge,its economy and practicability have been sought after by various countries.Therefore,the study of mechanical response characteristics and parameter sensitivity analysis of low pylon cable-stayed bridge has important theoretical significance for the design of bridge structure.Based on a large amount of literature,this paper finds that most scholars perform parameter analysis on the static performance of low pylon cable-stayed bridge from the influence of the layout of the cable and the constraints of the main beam.In comparison,the parameter sensitivity analysis of the cable spacing arrangement,the stiffness of the main beam and the stiffness ratio of the tower beam are few.In addition,the space variability of ground motion should be fully considered when analyzing the seismic performance of low pylon cable-stayed bridge with large span.In this paper,the double tower three span prestressed concrete low pylon cable-stayed bridge is taken as the research object,and the finite element calculation model is established by using the bridge finite element software Midas/Civil2019.The structural internal force change and displacement change of low pylon cable-stayed bridge affected by different parameters and the seismic performance of low pylon cable-stayed bridge under local site conditions are discussed.First of all,the first chapter introduces the origin and development of low pylon cablestayed bridge at home and abroad,summarizes the research status of parameter sensitivity and seismic response of low pylon cable-stayed bridges at home and abroad,and puts forward the research content of this paper.The second chapter then introduces the structural design of the low pylon cable-stayed bridge and the finite element calculation theory of the low pylon cable-stayed bridge,including spatial static analysis theory,geometric nonlinear analysis,site effect analysis and dynamic time-history analysis method.The third chapter establishes a finite element calculation model of a two-tower threespan prestressed concrete low pylon cable-stayed bridge,and then analyzes the natural vibration characteristics of the bridge and studies the influence of three parameters on the bridge structure internal force and bridge structure displacement.The three parameters are cable spacing,stiffness of main beam and stiffness ratio of tower beam.The results show that these three single parameters have significant influence on the internal force and displacement of the structure,and the optimal value range of these three parameters is obtained: The value range of cable spacing suitable for this bridge is 3.8~4.0m.The stiffness coefficient of the main beam ranges from 0.8 to 1.2.The stiffness ratio of tower beam ranges from 1.0 to 1.2.In chapter 4,relative motion method is used to analyze the seismic response of the bridge under multi-point excitation.The effect of the seismic response of the structure on the optimized bridge structure model is studied,and the results show that the seismic performance of the structure has been greatly improved.Then,the influence of site conditions on the seismic response of the low pylon cable-stayed bridge is mainly discussed,and the conclusion is: the softer the site conditions,the larger the seismic response of the structure;under the action of spatially varying site conditions,the seismic response of the bridge structure is significantly larger than that of the consistent site condition.In the seismic design of low pylon cable-stayed bridge,the influence of spatially varying site conditions should be fully considered,and seismic performance analysis of low pylon cable-stayed bridge with consistent site conditions will underestimate the seismic requirements of the bridge.Figure [44] table [11] reference [64]... |
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