Effects Of Loading Damage On Dynamic Properties Of Concrete

Based on the current development situation of high-speed railway in China, this paper study the dynamic characteristics under the dynamic load and static load function for the main structure of high speed railway infrastructure--concrete. The paper by modern analytical means and the experimental, study the dynamic characteristics change of the dynamic elastic modulus, shear modulus, Poisson’s ratio, damping ratio for different parameters of concrete under static loading and fatigue loading conditions, and analyzes the relationship between the concrete dynamic mechanics properties and porosity.Research shows that:(1) in the28d age, mineral admixture doped can lead to concrete elastic modulus, dynamic shear modulus and damping ratio decreases; and compared with the single fly ash, while maintaining the same contents, fly ash and silica fume admixture, fly ash,silica and limestone powder three admixture, dynamic modulus and damping ratio of concrete decreased more significantly; as the water binder ratio increases, the concrete move lower modulus and shear modulus, the damping ratio increases; composition parameters of concrete for the Poisson’s ratio of concrete was not affected. Between the concrete strength and the elastic modulus and shear modulus there is a good linear correlation.(2) the fatigue load stress level and the fatigue load times have obvious effect on the dynamic properties of concrete. With fatigue cycle increasing, elastic modulus and the dynamic shear modulus is reduced, but the damping ratio of concrete enlarge; compared with the number of fatigue, fatigue stress level have a more significant effect for the lower rate of concrete elastic modulus, shear modulus and the rate of increase of damping ratio. Under the condition of the stress level in the investigation of the fatigue load (ultimate load of not more than65%),the lower rate of the dynamic elastic modulus of concrete is within20%, the lower rate of the shear modulus is in the range of30%, and the lower rate of compressive strength is not more than30%.With respect to the effect of fatigue load, the lower rate of the dynamic mechanical properties of concrete is smaller, the lower rate of the dynamic elastic modulus, shear modulus is in the range of6%.(3) there is a close relationship between the concrete dynamic elastic modulus, shear modulus and water absorption rate; with the increase of stress level fatigue load or fatigue cycle, concrete water absorption rate increased, and the elastic modulus and shear modulus decreased, namely between the change of the concrete dynamic elastic modulus and shear modulus and the change of water absorption rate are more obvious correlation. In static loading condition survey (static load stress is less than the limit stress of65%), the concrete elastic modulus, shear modulus changes and water absorption rate of change anr no significant correlation.