锥台嵌挤预应力约束混凝土抗冲击性能研究

Study on impact resistance of pre-stressed confined concrete with a wedge-tightened truncated cone

钢管混凝土具有优良的抗冲击性能,为提高钢管在弹性阶段对混凝土的约束作用,设计并制备了锥台嵌挤预应力约束混凝土,以实现钢管对混凝土的主动围压约束。采用6 m高度落锤冲击试验,对比了预应力约束混凝土、素混凝土和常规钢环约束混凝土的破坏模式,分析了主要参数的影响。结果表明,当预应力约束混凝土试件的平均预应力大于1 MPa时,其产生初始可见裂缝时的冲击能量是素混凝土和钢环约束混凝土的4~20倍;其破坏时的冲击能量远高于素混凝土和钢环约束混凝土,甚至超过40倍;相比钢环约束混凝土,预应力约束混凝土破坏时裂缝更细,整体性更好,且可以更为显著的提高高强混凝土的抗冲击性能。为有效提高预应力约束混凝土的抗冲击性能,钢环的锥面倾角不宜大于3°,采用正六角形钢环要优于圆形和正四角形钢环。提出的锥台嵌挤预应力约束形式可以用于提高钢管混凝土的抗冲击能力,也可应用于防护门面层或遮弹层等结构中。

A concrete-filled steel tube has superior impact resistance.In order to improve the constraining effect of the steel tube on concrete at the elastic stage,this paper designs and prepares pre-stressed confined concrete with a wedge-tightened truncated cone,thereby completing the active pressure restraint of the steel tube to the concrete.The damage modes of the pre-stressed confined concrete,the plain concrete and the conventional steel ferrule confined concrete are compared by using a six-meter-high drop hammer impact test,and the effect of the main parameters is analyzed.The results show that when the mean pre-stress of the confined concrete specimen is greater than 1 MPa,the absorbed energy of the specimen when the initial visible cracks generate is 4 to 20 times that of the plain concrete and the steel ferrule confined concrete.This absorbed energy during the damage is much higher and even more than 40 times that of the plain concrete and the steel ferrule confined concrete.Compared with the damage pattern of the steel ferrule confined concrete,the pre-stressed confined concrete has finer damage cracks and better integrity when it is being damaged,which can significantly improve the impact resistance of the high strength concrete.In order to effectively improve the impact resistance of the pre-stressed confined concrete,the taper angle of the steel ferrule should not be greater than 3°;the impact resistance of the steel ferrule with a hexagonal truncated cone is better than that with a circle or a square truncated one.The proposed pre-stressed confinement form of the wedge-tightened truncated cone can be used to improve the impact resistance of a concrete-filled steel tube,and can also be applied to protective door layers or bomb shielding layers.