Study On PC Steel Bar’s Failur On Unit Of Crts I Slab Track Performance

Pre-stressed steel bars in the CRTS I slab track will inevitably be invalid under repeated actions of complex external loads, which will change the structural properties of the track and effect its durability. At present, the influences of the failure of pre-stressed steel bars on the mechanical characteristics of track are not clear, and there is a lack of the maintenance standards after failure. Research about the failure of pre-stressed steel bars in the CRTS I slab track are proceeded in the thesis, the main contents and conclusions are listed as follows:(1) The major diseases existing in slab track in combination with the present application situation of slab track at home and abroad are introduced, and the characteristics of the failure for the pre-stressed steel bars are elaborated. Based on the material properties of steel bar and the brittle fracture mechanical performance, the factors in steel bar failure are discussed.(2) Mostly the failure of pre-stressed steel bars is closely related to the contact loss of track slab, so the research should be considered in practice (considering the contact loss). CRTS I slab track was used as an example here to introduce in detail the calculation model and calculation method in terms of the failure of pre-stressed steel bars and contact loss of slab. Also evaluation standards used for results processing are elaborated. The most unfavorable force situation of the slab with effective pre-stressed steel bars is taken into consideration. The calculation results show that under the condition of the slab ends under the action of train load and the positive temperature gradient, the maximum tensile stress occurs at the first fastener position with the slab breakthrough in transverse (Condition3); under the condition of the middle of the slab under the action of train load and the positive temperature gradient, the maximum tensile stress occurs at the place where the longitudinal length of contact loss is400mm with a breakthrough in transverse (Condition7).(3) Based on the most unfavorable conditions, the ABAQUS software was used to solve the calculation model. And the influences of different locations and quantities of invalid pre-stressed steel bars on the slab performance were simulated. In combination with the evaluation standard the maximum value of the invalid steel bars and the critical state in which the slab will crack from the partially pre-stressed structure were summarized, based on which the maintenance suggestion values were proposed. The calculation results show that under the condition of the unidirectional pre-stressed steel bar failure, the slabs without contact loss suffer more disadvantages. The limit numbers of failed steel bars in the transverse and longitudinal direction are2and5respectively, which are recommended as the maintenance value. Similarly, the middle of the slab with contact loss suffers has more disadvantage for the structure. The limit numbers of failed steel bars in transverse and longitudinal direction are3and1respectively, which are recommended as the maintenance value. As to the failure of the bi-directional pre-stressed steel bars, the limit number is roughly the same as that for the unidirectional pre-stressed steel bar failure.