Research On Damage Mechanism Of Wide And Narrow Joints In CRTS? Slab Track Structure Under Temperature Load

CRTS ? slab track gradually expose many problems in their usages,especially their vulnerabilities to environmental changes.A wide range of interfacial cracks and structural fragmentations appearing on the wide and narrow joints,important linking parts of tracks,have an adverse effect on the stability of struck structures and high-speed moving of trains.Therefore,the paper basically studies main factors that do damages to the wide and narrow joints.And contents and conclusions of the research are as follows:1.According to results of my practical investigation on damages of CRTS ? track structures,I summarize types of damages and expound the main factors in the paper including great differences in sizes of the wide and narrow joints,insufficient structural strength and interfacial bond strength,and long-term effects of the external environment.2.A detailed finite element analysis model of the joint is established on basis of the theory of damage and fracture mechanics as well as damage characteristics of the track structure,so as to analyze influences of the temperature load on the structural bearing capacity and damage.The results show that overall rising temperature is the main factor resulting in structural fragmentation.Firstly,damage presents itself on both ends of the narrow seam and then extends its range to the interior of the wide joint.Finally,distribution of damage is more similar to the one in site;Overall cooling first leads to cracks on the upper parts between wide joints and bonding interfaces of track slabs,finally making wide joints and track plates almost completely fail to use;The maximum depth between the mortar and track plates is 0.237m although gaps among other parts are small.While hardly leads to breaking of joints,the positive temperature gradient first has damage to junctions of both sides of wide and narrow joints,resulting in the separation of the wide seams from the narrow seams.The overall damage degree of wide and narrow joints can be effectively reduced through increasing the material strength of joints.Given the rapid increases of local damage,therefore,I suggest that it is better to adopt concrete strength with the degree of C50.3.In the worst load condition,I study influences of difference of elasticity modulus and interface bonding strength on the bearing capacity and damage of wide and narrow joints.The results of my research suggest that enhancing the strength of the narrow joint is favorable for reducing the structural eccentric loading and the overall damages of track structures to ensure its overall stability;It is optimal to adopt a higher degree of concrete strength in narrow joints than that in wide joints,that is to say the former with a degree of C50 and the latter with a degree of C45.The strength of interface has a bearing on the distribution and further deterioration of damages in wide and narrow joints.The increase of the strength can improve the overall mechanical performance between joints and other track structures,which restrains the development of structural damage to a certain extent,but it is apt to aggravate local damage of narrow joints.Therefore,I suggest that it is appropriate to choose interfacial materials with strength of 60%to 80%.4.The finite element analysis model of narrow joints with different widths is established to study the stress and damage behavior of wide and narrow joints under the most unfavorable loading conditions.According to the result,the difference between the size of the wide joint and the narrow joint is the most important factor leading to structural damage and eccentric loading.A bigger size of the narrow joint is able to effectively lessen the structural damage,optimizing the structural loading capacity.Hence width of wide joints should be same with that of narrow joints.