Seismic Analysis Of Long Span Railway Concrete-filled Steel Tube Arch Bridge

Arch bridge is one of the ancient bridge form which span a large distance and has a excellent carrying capacity, high stability and better durability. And its advantages also conclud that it has amount typies of construction materials,low project cost and maintenance cost and magnificent look. With the application of new materials, the span of arch bridges is longer, especially after the rapis development of concrete-filled steel tube arch bridge.The concrete-filled steel tube arch bridge has higher bearing capacity, longer span,aseismatic performance as well as its convenient construction environment. Because earthquake often happens in our country, and this type of bridge is built more and more widely in earthquake areas in our country for its great performance.All of the country in the world attaches a great agreement on the research filed of bridge seismic theory and design practice, and draw up the structure seismic fortification principle and the aseismatic design criterion according to the condition of a country.Our country also established corresponding anti-earthquake design specification in the railway engineering, but the standard only applies to seismic design of the bridge whose span is less than 150m of steel-box girder and less than 120m of reinforced concrete and prestressed concrete beam. Because of its large span, arch bridge has a different mechanical characteristics comparing with common small-span bridge,and the seismic design specification should be studied separately.Based on the project of concrete-filled steel tube arch bridge of BAO XI railway, this paper use the finite element software MIDAS to establish the space finit element model of the whole bridge and have done several aspects of works as following show:(1) Based on the analysis of self-vibration characteristics of the bridge, paper analyzed the seismic response of the bridge respectively along the bridge vertical, horizontal, vertical by inputing response spectrum. Paper also use the arch rib bend internal force and displacement as the research objects to analysis the influence of self-vibration characteristics and seismic response under the geometric nonlinear which caused by initial dead load internal forces.(2) Considering the geometrical nonlinearity influence to earthquake reaction, the seismic waves are inputted in longitudinal, transverse and vertical direction.paper analized the internal force and displacement variation as the input direction is changing in the spot of arch feet, L/8 span, L/4 span,3L/8 span and L/2 span.The results show that geometrical nonlinearity has a slight influence in long-span concrete-filled steel tube arch bridge of railway. In order to get some common conclusion, the paper sumed up some of results about the concrete-filled steel tube arch bridge in references and gained some conclusions for reference.(3) Input three existing eathquake acceleration records of frequent earthquakes to this bridge respectively. By using dynamic time-history analysis, it was conducted that the comparisons of the results of analysis of six input mode under the uniform seismic excitation such as longitudinal seismic effect, lateral seismic effect, vertical seismic effect, longitudinal+vertical, lateral+vertical and longitudinal+lateral+vertical. After that, the variation of internal force and displacement of the arch rib was investigated. Finally, confirmed the worst input mode for this bridge.(4) Considering the material nonlinearity influence to seismic response of long-span concrete filled steel-tube arch bridge piers, on the conditions of equal strength and stiffness, piers of this bridge are instead of rectangular and round-ended hollow piers which can resist large earthquake. Comparing the elastic-plastic analysis result of the two type piers under strong seismic action, which are simulated by fiber model, and obtained some meaningful conclusions.