Research On The Load Transfer Failure Mechanism For Dowel Bar In Concrete Pavement

Damage of the contact interface between dowel bar and concrete (CIDC) is themain reason for the transferring failure of dowel bar and early damage of shrinkjoints in the cement concrete pavements (CCP). Focused on the problem oftransferring failure, mechanical characteristics of dowel bar were studied in t histhesis. The failure process of dowel bar under different damage mode was explodedby means of tests, and the physical mechanics of transferring failure were presentedby the following two aspects: mechanical performance degradation of CIDC;cracking of covering layer.3types of transferring failure of dowel bar weremechanically simplified by means of theoretical model establishment, and the crackextension in the peripheral concrete of dowel bar was simulated by numericalmethod. And then the test and numerical calculation method of critical guidepostsof vehiculary axel load were indicated. The work in this thesis can be summarizedas the follows:First of all, the three-dimensional finite element model of CCP was established,the different contact situations of dowel bar to concrete and surface to base wereconsidered. By varying the combination characteristic of axel load, temperature andshrink joints, the mechanical characteristics of dowel bar were researched. Theunfavorable position of shrink joint where is most easily to be damaged was located.On this basis, testing system of CIDC was developed. According to differentdamage modes, different test schemes were accordingly designed.Secondly, by using the testing system, limited bearing capacity test, fatigue testand accelerated corrosion test were separately implemented to simulate the failureprocess under three damage modes of CIDC. Based on the obtained signal of soundemission test, the mechanics of transferring failure under three types of differentdamage modes was studied in the perspective of CIDC’s mechanical performancedegradation and cracking of covering layer. And then the test method of criticalvehicle axel load of shrink joint structure was proposed.Once again, according to the physical phenomenon of CIDC during its damageprocess, the following models of dowel bar were abstracted. They are limited damage model, fatigue loose model, dowel bar-corrosion product-covering layercoupled model. By applying numerical method, crack extension behavior in theposition of peripheral concrete of dowel bar was simulated under the three failuremodes. And then the numerical calculation method of critical vehicle axel load ofshrink joint structure was indicated.Finally, the durability improve method of dowel bar under the cryohydriccircumstance was proposed. Structural form of newtype steel dowel bar wasdesigned. Endurance coating mixture was developed, which is not affecting themechanical performance of steel dowel bar’s anchored-end. Design and checkmethod of GFRP dowel bar was also studied.Researches in this thesis are conducive to correctly evaluate the work status ofdowel bars, and also let people know about the failure process of dowel bar underdifferent damage modes. At the same time, offered engineers a referential scheme todesign more durable dowel bars, and presented a series of references to reduce thedamage of transverse shrink joint of CCP structure.