带肋钢筋与超高延性水泥基复合材料的黏结性能

超高延性水泥基复合材料(UHDCC)是新型纤维增强混凝土,受拉时表现出超高的延性和应变硬化能力.为提供UHDCC应用于受力构件的界面黏结理论依据,进行了45个钢筋在UHDCC中锚固的拉拔试验,考察了锚固长度、浇筑方式、保护层厚度、90°弯钩等对黏结性能的影响.试验结果表明:由于纤维约束作用,试件未发生劈裂破坏;UHDC...

Bond behavior between ribbed steel bar and ultra-high ductile cementitious composite

Ultra-high ductile cementitious composite (UHDCC), a new type of fiber reinforced concrete, exhibits ultra-high ductility and strain hardening ability during stretching. In this study, pull tests were conducted on 45 specimens whose ribbed steel bars were all anchored in UHDCC. The influences of anchorage length, pouring method, protective layer thickness, 90-degree hook, and other parameters on the bonding performance were investigated, and a theoretical basis for the bonding strength of the force-bearing members using UHDCC was provided. Results show that all the specimens did not split due to the restraint of the fiber in the UHDCC. The pouring method of UHDCC had significant impact on the bonding strength, and the bonding strength of the specimen poured vertically was greater than that of the specimen poured horizontally. As the anchorage length of the specimen increased from 4d to 6d, the bonding strength tended to increase due to the strain hardening of UHDCC. When the anchorage length was longer than 6d, the anchorage length of the central anchoring specimen (with a thicker protective layer) had little effect on the bonding strength. However, the bonding strength of the eccentric anchoring specimen (whose restraint of UHDCC to the ribbed steel bar decreased due to the thinner protective layer) decreased with the anchorage length increased. A 90-degree hook with the length of 4d was added at the end of the steel bar when the length of the straight anchor section was 4d, and the ultimate bearing capacity was increased by 67%. However, when the length of the straight anchor section increased, the effect of the 90-degree hook on the ultimate bearing capacity began to decrease. When the absolute anchorage lengths were the same, the bearing capacity of the specimens without hooks was greater than that of the specimens with hooks. For the specimen whose steel bar had a 90-degree hook, the anchorage length must be guaranteed. Based on the test results, the bond-slip mechanism between ribbed steel bar and UHDCC was analyzed, and the equation of bonding strength between UHDCC and ribbed steel bar without 90-degree hook was given.