并筋黏结锚固性能试验研究

针对并筋后钢筋与混凝土之间的有效接触面积减小、黏结性能相对变差的问题,通过57个拉拔试件和6个半梁式试件的并筋黏结锚固试验,研究了并筋的黏结锚固性能.试验中考虑了并筋根数、钢筋直径、混凝土强度、锚固长度等因素对并筋黏结滑移性能的影响.试验结果表明:并筋根数越多,名义黏结强度降低;试验方式、锚固长度、钢筋直径、混凝土强度、钢筋位置等因素对并筋黏结强度的影响与这些因素对单根钢筋黏结强度的影响相似,可以引用单根钢筋的试验研究结果分析并筋的黏结锚固性能.基于各国规范黏结强度经验公式和本文的试验数据分析,建议二并筋、三并筋的等效钢筋直径分别取值1.41和1.73.当保护层厚度减小时,可适当延长并筋的锚固长度.

Experimental Study on Bond Anchorage Properties of Bundled Bars

Aiming at the problems that the effective contact area between the steel bar and concrete decreases and the bonding property becomes worse after the reinforcement is bundled, the bond anchorage property of the rein? forcement was studied through the bond anchorage tests of 57 pull out specimens and 6 beam specimens. The influ? ences of the number of rebars, test method, diameter of rebar, strength of concrete, anchorage length and the position of rebar on the bond slip performance of the bundled bars were studied. The test results show that the greater the num? ber of parallel bars, the lower the nominal bond strength; Compared with a single steel bar, the test method, anchor? age length, diameter of steel bar, concrete strength and position of steel bar have a similar influence on the bond strength of bundled bars, but the influence degree is different. Based on the test data analysis on the empirical for? mula of bond strength in design codes, it is suggested that the equivalent diameters of 2 and 3 bundled bars should be 1.41 and 1.73, respectively, so as to be used for the values of anchorage length and thickness of cover. When the thickness of cover is reduced, the anchorage length of the bundled bars can be appropriately extended.