不同缝高比自密实混凝土梁断裂及疲劳特征

Fracture and fatigue characteristics of self-compacting concrete beams of different crack-depth ratios

为探究自密实混凝土(Self-Compacting Concrete,SCC)梁的断裂特性与疲劳断裂行为,针对3种初始缝高比(0.1、0.2和0.3)的SCC梁开展准静态断裂试验。结果表明,SCC梁的临界缝高比和失稳韧度均随初始缝高比的增大而增大。与普通混凝土相比,SCC的阻裂能力较弱,且SCC梁的失稳韧度比普通混凝土有所下降。同时,对初始缝高比为0.2的SCC梁开展循环荷载与激增荷载交替作用的变幅疲劳断裂试验。结果表明,在激增荷载作用下,SCC梁的疲劳行为受加载速率的影响。当激增荷载超过SCC梁的静态承载力时,裂缝增长速率加快,导致SCC梁破坏。低荷载比的循环荷载有助于提高SCC抵抗激增荷载的能力。当荷载比小于0.5时,SCC破坏前能承受更多次激增荷载作用。

In order to investigate the fracture characteristics and fatigue fracture behavior of self-compacting concrete(SCC)beams,quasi-static fracture tests were carried out on SCC beams of three crack-depth ratios(0.1,0.2 and 0.3).The results show that the critical crack-depth ratio and instability toughness increase with the increase of initial crack-depth ratio.Compared with ordinary concrete,the cracking resistance of SCC is weaker,and the instability toughness of SCC beams is lower than that of ordinary concrete.At the same time,the variable amplitude fatigue fracture tests were carried out on SCC beams with the initial crack-depth ratio of 0.2 under cyclic load and surge load.The results show that the fatigue behavior of SCC beams is affected by loading rate under surge load.When the surge load exceeds the static bearing capacity of the SCC beam,the crack growth rate accelerates,leading to the failure of the SCC beam.Cyclic load with low load ratio can improve the ability of SCC to resist surge load.When the load ratio is less than 0.5,SCC can withstand more surge loads before failure.