Study on Dynamic Damage Process of Concrete Based on X-Ray CT Technique

Abstract eng:
Research on the strength and the failure mechanism of concrete under dynamic loading is a weak point in seismic safety assessment for concrete structures. X-ray computed tomography (CT) technique is a useful tool to detect the process of the initiation, propagation and continuous accumulation of interior micro damage leading to macro crack and finally to the complete failure of concrete by non-destructive way. A portable test device for dynamic tensile and compressive loading specially designed to fit the conventiona l medical CT scanner has been manufactured. Based on the medical CT scanning system and the special designed and manufactured portable test device the static and dynamic real time CT tests for concrete specimens under compressive loading have been carried out. The provided CT images verified the expected requirements to the designed CT test system. The difference of cracking process between the static and dynamic compression loading conditions was investigated in detail. In high strain rate, concrete fracturing points increase and mesocrack seems straight. The phenomenon that crack cut across aggregate grows. So concrete dynamic strength can increase. The preliminary results prepared the ground for setting the crack evolution models of concrete under different loading conditions. In order to intuitively demonstrate the crack morphology character and crack evolution process during the loading, the formation of 3D images and the animated cartoons displaying technique of the crack development by using the CT test results have been completed using 3DMAX software. All the abovementioned research works have brought forth some new ideals in the study on dynamic behavior of concrete for evaluation seismic safety of concrete structures.

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