Study On Seismic Performance Of Steel Plate-concrete Composite Reinforced Railway Gravity Pier

Our country has now built one of the most comprehensive railway network and high speed railway network in the world.There are a large number of railway Bridges.Railway gravity piers have been widely used in railway line.Some of these piers which are designed according to old code and damaged during earthquake activity have hidden dangers of safety,thus cannot meet the standard of seismic protection according to the current code.Therefore,it is particularly necessary to study the reinforcement scheme of the existing gravity pier which fails to meet the existing seismic fortification standard.Based on the summary and improvement of the traditional reinforcement scheme,this paper puts forward a steel-concrete composite reinforcement method which is suitable for the gravity pier with less reinforced concrete.The failure mode and seismic performance of pier before and after reinforcement are compared by theoretical analysis,pseudo-static test and numerical simulation,and the feasibility of this method is verified.The reinforcement effect of this method is evaluated based on Pushover method.The main research contents of this paper are as follows:(1)By reading a large number of relevant literature,the seismic reinforcement methods of existing pier are summarized,and then the shortcomings of the seismic reinforcement methods of existing railway gravity pier are summarized from the seismic damage characteristics of railway gravity pier.(2)Based on the theoretical analysis of the composite reinforcement scheme,combined with the existing problems of traditional reinforcement,reinforcement objectives and factors to be considered in reinforcement,a seismic reinforcement method using steel plate-concrete composite reinforcement for gravity pier is proposed,and the reinforcement height and planting reinforcement depth are calculated.(3)Taking the gravity pier of a 16 m simply-supported beam bridge of a railway as the prototype,two pier models were designed and made according to the scale ratio of 1:8.The pseudo-static test was carried out to analyze the characteristics of the two piers,such as hysteretic curve,energy dissipation capacity,skeleton curve and stiffness degradation,and the differences of these characteristics between the two piers were explained combined with the failure modes.The test results show that the strength,stiffness and energy dissipation of the steel-concrete composite reinforced pier are higher than those of the original pier.(4)According to the stress mechanism of the test model pier,a simplified calculation model of the reinforced pier is proposed.The simplified model of the test pier is established by using OPENSEES software,and the key steps in the modeling process are explained in detail.The results of finite element analysis and test are compared and analyzed,and the results show that they are in good agreement.(5)Based on OPENSEES finite element software,the reinforced model and unreinforced model of prototype railway gravity pier are first established.The capability spectrum and demand spectrum curves of prototype reinforced pier and unreinforced pier are established by Pushover analysis,and their seismic performance is evaluated.The results show that the unreinforced pier can only meet the seismic requirements in the seismic intensity zone of 7degrees,while the steel-concrete reinforced pier can meet the seismic requirements in the seismic intensity zone of 8 degrees,which further verifies the feasibility of steel-concrete reinforced railway pier.