Research On Seismic Performance Index And Reliability Of Railroad Tunnel Lining Structure

With the continuous development of national economic construction,the construction of railroad tunnels is increasing,how to ensure the safety of the construction and operation of railroad tunnels is particularly important,and some high-intensity earthquakes in recent years have not only led to structural damage of railroad tunnels but also caused huge economic losses.Therefore,the seismic design concept that is not limited to the structural load-bearing capacity requirements but takes into account a variety of factors such as structural safety and economic efficiency is gaining more and more attention,namely the performance-based seismic design theory.In this thesis,the types of seismic damage and damage mechanisms of railroad tunnels are studied,and performance indicators that can be applied to railroad tunnel lining structures are proposed,the quantitative study of performance indicators of railroad tunnel lining structures is carried out based on the elastic-plastic time analysis,the study of factors influencing the seismic susceptibility of railroad tunnel lining structures is carried out based on the principle of susceptibility,and the probability density evolution method is used to calculate the seismic reliability of railroad tunnel lining structures.The main research results of this thesis are as follows:(1)Through the collection and collation of railroad tunnel seismic hazard data,the damage mechanism of railroad tunnel lining structure is summarized and analyzed,and the damage pattern of railroad tunnel lining structure is mainly bending-tension damage.Through the elastic-plastic time course analysis of railroad tunnel lining structure under different working conditions,it is concluded that the tensile-plastic damage area of the structure is much larger than the compressive-plastic damage area,and the tensile equivalent plastic strain of the structure can better describe the damage process of the structure.(2)According to the division of seismic performance level of railroad tunnel,the ultimate tensile strain of concrete and yield strength of reinforcement were selected as the basis for the judgment of the first and second limit values of seismic performance level of railroad tunnel lining structure,through the incremental dynamic analysis of railroad tunnel lining structure,the overall plastic damage of the structure reaching 70% was recognized as the structural collapse point and used as the basis for the judgment of the third limit value of performance level.(3)By summarizing other structural performance indicators and combining the damage mechanism of railroad tunnel lining structure,a two-parameter damage model based on relative deformation rate and accumulated plastic tensile strain is proposed and used as the seismic performance index of railroad tunnel lining structure.(4)The incremental dynamic analysis method is used to quantify the performance indices of shallow buried railroad tunnel lining structures with different rock envelope levels,burial depths,seismic groupings,and concrete strengths and to obtain the performance index limits of railroad tunnel lining structures at different performance levels.Based on the single-parameter damage model(relative deformation rate and capacity demand ratio),the performance indices are influenced by environmental and material factors.Under the same performance level requirements,the higher the rock level,the shallower the burial depth,the higher the seismic grouping,and the higher the concrete strength of the lining,the smaller the limits of the performance level of the railway tunnel lining structure obtained.The performance indices based on the two-parameter damage model(Chen-Ying Ye’s two-parameter damage model and this thesis’ s two-parameter damage model)are less influenced by environmental and material factors.(5)The seismic performance of railroad tunnel lining structures with different rock levels,tunnel burial depths,seismic groupings,and concrete grades is studied through the principle of susceptibility to damage.For shallowly buried railroad tunnel lining structures,the poorer the stability of the surrounding rock,the deeper the burial depth,the smaller the seismic grouping,and the smaller the concrete grade,the greater the probability that the structure will exceed the performance level.At a seismic intensity of 9 degrees(0.4 g),the probability that the railroad tunnel lining structure exceeds the performance level one under different surrounding rock grades ranges from 35% to 65%.The probability that the railroad tunnel lining structure exceeds the performance level one under different burial depths ranges from 65% to86%.The probability that the railroad tunnel lining structure exceeds the performance level one under different seismic grouping waves ranges from 31% to 65%.The probability that the railroad tunnel lining structure exceeds the performance level one under different concrete.The probability that the railroad tunnel lining structure exceeds performance level 1 for different concrete strengths ranges from 36% to98%.(6)The probability density evolution method is used to analyze the seismic reliability of the railroad tunnel lining structure.The tunnel working condition is class V surrounding rock,5 m burial depth,concrete grade C35,design earthquake grouping is group one,seismic intensity is 9 degrees(0.4 g),under the seismic requirements of performance level one,with relative deformation rate as the performance index,the seismic reliability of the railroad tunnel lining structure is0.037.With the two-parameter damage model as the performance index,the seismic reliability of the railroad tunnel lining structure is 0.014.