Conceptual Design And Aseismatic Analysis Of Qiongzhou Strait Ultra-long Multi-span Highway-railway Suspension Bridge

The static and seismic safety of Qiongzhou Strait ultra-long multi-span suspension bridge was analyzed. The fictitious beam method was improved. By applying the improved fictitious beam method a-feasibility research scheme of Qiongzhou Strait suspension bridge was proposed. The response of the scheme subjected to consistent and multi-support earthquake excitations was analyzed using self-programmed software. The power spectrum method solver in the self-programmed software was programmed according to the specifications based on the pseudo-excitation method. The self-programmed software was also applied to the analysis of the power spectrum of the scheme subject to consistent earthquake and considering the traveling wave. The main research work covers the following aspects:(1) A4x3000m multi-span highway-railway suspension bridge was proposed according to Qiongzhou Strait meteorological, hydrological, geological conditions. In order to meet the demands of railway suspension bridge, the vertical load deflection 1/600 requirements, the area of the main cable and the main components of the size and layout of the form was initially fixed. The strength and stiffness of the scheme under the dead loads, vehicle loads and lateral ultimate wind loads was calculated using self-programmed software.(2) The fictitious beam theory has been improved, is derived for the compatibility equation of the virtual beam method. By introducing the concept of longitudinal stiffness of the bridge tower make the improved virtual beam method used in the analysis of multi-span suspension bridge. On this basis, to explore the vertical stiffness of the tower, the central button, main cable section size, materials density, carbon fiber main cables and so on influence on the main cable vertical stiffness of multi-span suspension bridge. The vertical stiffness of the research Suspension bridge scheme for the highway-railway demanding characteristics is proposed to use map-selection method to determine a reasonable span suspension bridge main cables layout and section size.(3) An improvement was made for the current HOP method. The improved HOP method generate the artificial ground motion time history fitting better with the given power spectrum. The artificial earthquake can be used in seismic analysis of intensive spectrum structure. By the improved HOP method synthesized the Qiongzhou Strait multi-point ground acceleration history. The calibration method of ETZ (End Time Zero Technique) was simplified and was used in the artificial ground acceleration history. After calibration, only cause a small amount of change, guarantee the end ground acceleration and displacement equal to zero, can be directly used in the quasi-static displacement calculation.(4) In order to analyze the origin of quasi-static displacement and dynamic displacement, multi-point excitation dynamic equilibrium equation is derived. According to the multi-point excitation dynamic equilibrium equation independently programmed a finite element program, and through theoretical analysis and commercial software corresponding calculation results verified the correctness of self-programmed programs. The finite element program environment and dynamic calculation class can be used as the base class of power spectrum analysis class. All the procedures used to study the multi-point earthquake excitation of the suspension bridge scheme.(5) Based on the theory of the power spectrum and pseudo-excitation method, programmed to achieve the analysis of structural power spectrum response under a consistent and multi-point excitation. Derivation of the whole solution of single degree of freedom system response in the virtual harmonic excitation, and calibrate use sub-analytical method. Finally, the author programmed to achieve the evaluation of the power spectrum of structural dynamic response.(6) The time history response of the scheme under excitation of consistent and multi-point respectively was caculated. Through superimposed the stress results of time history analysis and the stress result of dead load and compared with the material strength, the strength of the research scheme under the action of E2 seismic can be considered meet the requirements. According to the specifications, calculated separately in the horizontal and lateral the power spectrum response of the scheme under seismic excitation, the dynamic safety of the Qiongzhou Strait Suspension Bridge was evaluated. Without considering the structure response of non-stationary, the research program was designed to more conservative due to the main cable stress is low and there is surplus. Bridge tower using concrete materials, the quality of their own larger and compressive strength is low, uniform excitation in the vertical when the reliability is low, longitudinally non-uniform excitation power reliability meets the requirements.