反复荷载作用下钢-聚丙烯混杂纤维混凝土与钢筋黏结强度研究

考虑钢纤维和聚丙烯纤维的体积率、长径比等因素的影响，设计制作36个钢-聚丙烯混杂纤维混凝土试件，通过中心拉拔试验，研究低周反复荷载作用下钢-聚丙烯混杂纤维混凝土与变形钢筋间的黏结强度。结果表明：混杂纤维的掺入对混凝土与钢筋间的黏结强度存在正混杂效应，其中钢纤维对黏结强度的提高作用更为明显。对于混杂纤维混凝土，在聚丙烯纤维体积率为0.15%、长径比为167的情况下，当钢纤维体积率从0.5%增长到1.5%、长径比从30增加到80时，黏结强度分别提高了20.57%和14.75%，而聚丙烯纤维体积率和长径比的变化对黏结强度没有明显影响；当混杂掺入体积率为1.5%、长径比为60的钢纤维与体积率为0.15%、长径比为167的聚丙烯纤维时，与相应的单掺钢纤维混凝土、聚丙烯纤维混凝土和普通混凝土相比，黏结强度分别提高了14.64%、31.37%和46.55%。此外，基于厚壁圆筒理论，针对实际受力情况，建立了钢-聚丙烯混杂纤维混凝土与变形钢筋黏结强度的理论模型，计算结果与实测结果吻合良好。

Study on bond strength between steel-polypropylene hybrid fiber reinforced concrete and deformed bar under cyclic loading

In order to study the cyclic bond strength between the steel rebar and steel-polypropylene hybrid fiber reinforced concrete （HFRC）, a total of 36 specimens were designed by means of pull-out test taking the effects of volume fraction and aspect ratio of steel fiber （SF） and polypropylene fiber （PF） into consideration. The results show that the introduction of hybrid fibers has a synergetic effect on improving the bond strength, and SF exhibits a more pronounced influence. For the HFRC specimen, whose volume fraction and aspect ratio of PF were 0.15% and 167, the bond strength is increased by 20.57% and 14.75% respectively, when the volume fraction of SF varies from 0.5% to 1.5%, and 30 to 80 for the aspect ratio. However, no significant influence is observed when the volume fraction and aspect ratio of PF varies. Moreover, when comparing with the SFRC, PFRC and PC specimens, HFRC specimen having SF of 1.5% in volume fraction and 60 in aspect ratio, and PF of 0.15% in volume fraction and 167 in aspect ratio exhibits higher bond strength, and the improvement could reach up to 14.64%, 31.37% and 46.55% respectively. Furthermore, based on the theory of thick-walled cylinder and actual stress state, a modified model was proposed to calculate the bond strength between steel rebar and HFRC. The analytical solutions were then validated by the results from current study and other literatures.