Simplified Analysis Model of Longitudinal Constraint Effect of High-speed Railway Simply-supported Bridge Under Earthquake
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Abstract The structure of a high-speed railway (HSR) bridge with a track system is complex, and the computational efficiency of seismic analysis for a fine HSR bridge with a track system model (BM) is low. This study considers an HSR bridge with CRTS II slab ballastless track system as a case study and develops a simplified model (SM) based on a method for simulating track constraints with equivalent springs. To obtain the optimal stiffness of SM equivalent springs, a finite element (FE) structural parameters updating framework utilizing an improved genetic algorithm (GA) is established, and the updated SM's dynamic characteristics and seismic response are compared to BM's. In addition, it uses SM to analyze the over-limit state and applicability of the bridge structure's critical components. The results indicated that the model simplification ratio of SM reaches 95%. The seismic response outcomes of SM and BM accurately agree with an average relative error of 3% and a maximum relative error of less than 5%. The over-limit state of the seismic response structure tends to be stable as the number of ground motion samples increases. The shear and bending capacity of the pier and the deformation of the fixed support have a high over-limit risk under longitudinal seismic, which is worth noting in the engineering design.Keywords:
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Bridge (graph theory)
Limit state design
Slab
Ballast
Substructure
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Plastic hinge
Bridge (graph theory)
Mode (computer interface)
Seismic loading
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In this paper, in order to do research on the characteristics of reducing vibration and declining noise of concrete floating slab track, the vertical dynamic analysis model of vehiclefloating slab track is established with the use of finite element analyses method. By using this model, dynamic responses of floating slab track are studied under different conditions of train’s speed, stiffness and damping of infrastructure, structure size, etc. On the basis of this research, some suggestions for design of floating slab track are put forward.
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The lateral finite strip and slab segment element is used to simulate the slab track with the structure features of the slab track considered.Based on the principle of total potential energy with stationary value in elastic system dynamics and the rule of set-in-right-position for formulating system matrixes,the vertical vibration equation set of the high-speed train and slab track time-dependent system are established with the vertical connecting condition between the wheel and the rail considered.The effect of the stiffness change of the slab track on the vertical dynamic characteristics of the system is analyzed.The calculated results demonstrate that the reasonable stiffness of the slab track can effectively reduce the vertical vibration response of the system.The proposed stiffness value ranges of CA mortar and rail pad are 1000—1500 MPa/m and 60—80 kN/mm respectively.
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Position (finance)
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The history of slab track construction in Germany is described. A total of 155 km of double-track slab track has been constructed on the Cologne-Rhine/Main 300 km/hour high-speed line. The design parameters that led to slab track being chosen over ballast track for the high-speed line are outlined. Construction of the slab track on the new line is discussed with reference to the rail supports, concrete-embedded two-block sleepers, the Rheda and Zueblin systems, turnouts, bridges and expansion joints. The other slab track systems used in the high-speed network of DB Netz AG are outlined.
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Ballast
Railway line
Line (geometry)
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Deteriorated track-slabs have been so far found in some areas subject to cold weather conditions. For track-slab maintenance purposes, it is very important to understand the causes of this deterioration. Visual inspections of track-slabs and investigation of samples of materials used in track-slabs were therefore carried out. Visual inspections found that deterioration occurred more frequently on south facing sides of track-slabs exposed longest to the sun. Material investigations showed that track-slab deterioration was caused by an alkali-silica reaction and frost damage.
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Frost (temperature)
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Research purposes: The basic component of the track structure with isolated rubber floating slab is the concrete slab track born by the elastic element.The research was done on the mechanical properties of the floating slab,the analysis was made for the natural frequencies,mechanical response under dynamic load and damping performance,and the discussion was made on the reasonable thickness of the ballastless track to provide the reference to the track design. Research conclusions:The research results show that the natural frequency of the track system decreases with the increase of the thickness of the ballastless track,and the rate of change decreases with increase of the track thickness.The acceleration insertion loss of the track basis increases with the increase of the thickness of the ballastless track,and the rate of change decreases with increase of the track thickness.When the thickness of the ballastless track reaches at 0.4m,the corresponding dynamic performance,the damping performance effect and the concrete amount of track bed are rather economical.From the present theoretical analysis and online testing,it can be seen the damping performance effect of the isolated rubber floating slab system is obvious,and its construction and maintenance programs are systematic.
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Natural frequency
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Both ballasted track and slab track are commonly used in high-speed railways. Based on the theory of vehicle-track coupled dynamics, the wheel-rail dynamic responses in the rail weld zones of these two tracks are investigated, and the P 1 , transient high-frequency impact force, and the P 2 , low-frequency impact force are analysed. The results show that, due to the high stiffness and small damping ratio of the vehicle and the ballasted track system, the P 1 force of the ballasted track is generally greater than that of slab track while the P 2 force is smaller than slab track. Furthermore, the duration of the impact load of ballasted track is longer than that of slab track. The results will provide a reference for the analysis and evaluation of ballasted tracks in high-speed railways.
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Reactive Powder Concrete is proposed to be used in the ballastless track for its excellent material properties due to existing problems of high speed railway ballastless track. Three different unit types of RPC frame slab track were proposed through optimization design and the mechanical behavior of these frame slab track was analyzed. The results show that the RPC slab track meet the requirements of bearing capacity, the suggested type of RPC slab track is a frame slab with increased thickness because of its higher techno-economic advantages.
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