【摘要】 混凝土材料在动载作用下具有与静载不同的特性。从实时CT扫描试验出发,以素混凝土圆柱体试样为研究对象,分析了正弦波动压和动拉荷载作用下,混凝土的细观结构变化对动态力学特性中诸如强度、变形和破损形态的影响。通过CT差值图像研究,得出动压荷载作用下混凝土裂纹具有发展迅速,破坏过程短,破坏裂纹多,破坏面积大等特点;通过CT数等密度分割图研究,得出动拉荷载作用下混凝土微裂纹突然合并形成一条主裂纹贯穿试件,试件突然断裂;通过加载过程中CT数变化规律研究,得出动压荷载作用下混凝土的密度经历了一个先增大后减小的过程,试件经历了压密、扩容、裂纹贯通直至最后破坏的过程,而动拉荷载后试件的密度持续减小直至断裂,荷载初期无压密现象。混凝土试件形成单位面积的压、拉裂纹面所需的能量基本相同,形成单位面积的动力裂纹面所需的能量略大于静力裂纹面所需能量。混凝土动压、动拉的应力状态不同,导致其破坏程度不同,所形成的裂纹面积不同,所需的总能量也不同,最终导致测定的强度不同,应力状态不同是动压、动拉强度差异的根本原因。更多还原

【Abstract】 Concrete material under dynamic loads has different characteristics comparing with those under static loads. Here,CT tests of concrete material were investigated taking,plain concrete specimens under dynamic loading as study objects. The effects of concrete meso structure change on its dynamic characteristics,such as,strength,deformation and damage morphology under the sine wave dynamic pressure and dynamic tensile load were analyzed. Through studying CT difference images,it was shown that cracks in concrete under compressive loads grow rapidly,their failure process is short,failure cracks have many,damage area is large,etc. Through CT number equidensity segmentation image study,it was shown that under dynamic tensile loading,concrete micro cracks suddenly merge to form a main crack passing through the specimen,the specimen breaks suddenly. Through studying the CT number change law in loading process it was shown that the concrete density decreases after a first increase under the dynamic compressive loads,specimens experience a process of compaction,expansion,crack coalescence until final failure,and under the dynamic tensile load the specimen density continuously drops until its fracture,early without compaction; different stress states of concrete under dynamic compressive loads and dynamic tensile loads lead to its different damage levels,different crack areas formed,different total energy required,and its different strengths neasured finally; different stress states are the essential cause to cause the difference between dynamic tensile strength and dynamic compression one.更多还原