钢筋与钢纤维再生混凝土黏结滑移性能及模型

Constitutive Model and Bond Stress-slip Behavior Between Rebar and Steel Fiber Reinforced Recycled Concrete

为了推广钢纤维再生混凝土在道路、桥梁等工程中的应用,以再生骨料取代率(0%、30%、50%和100%)和钢纤维体积率(0%、0.5%、1.0%、1.5%和2.0%)为试验参数,设计了11组不同配合比的钢纤维再生混凝土,制作了33个钢筋与钢纤维再生混凝土黏结试件,进行内贴应变片的钢筋与钢纤维再生混凝土黏结试件的拔出试验。结果表明:钢筋与钢纤维再生混凝土黏结应力沿黏结区段的分布存在2~3个峰值,黏结段内的黏结刚度沿黏结长度变化是引起黏结应力和滑移沿黏结段不均匀分布的主要原因;黏结刚度分布的均匀性随再生骨料取代率的增加而提高,再生骨料取代率为50%时的黏结刚度分布均匀性较好;掺入钢纤维后,黏结刚度均匀性得到了提高,但钢纤维体积率2.0%试件的黏结刚度均匀性变差;加载端滑移随再生骨料取代率的增加而增大,随着钢纤维体积率的增加而降低;黏结应力分布均匀性随再生骨料取代率和钢纤维体积率的增加而提高,距离自由端最近的峰值应力随再生骨料取代率的增加而增大,钢纤维体积率的影响较小;钢筋与钢纤维再生混凝土黏结应力滑移曲线的形状不随黏结位置的变化而改变。最后,提出了考虑再生骨料取代率和纤维体积率影响的钢筋与钢纤维再生混凝土黏结-滑移本构模型。

To promote the application of steel fiber-reinforced recycled concrete（SFRAC）in road and bridge engineering,11 different mixture proportions of SFRAC were designed and a total of33 bond specimens of rebar and SFRAC were cast with the test parameters of the recycled coarse aggregate（RCA）replacement ratio（0%,30%,50%,and 100%）and steel fiber contents（0%,0.5%,1.0%,1.5%,and 2.0% by volume）.Pull-out tests were conducted for the bond specimens between the rebar with strain gauges inside and SFRAC.It was found that there were two or three bond stress peak values in the bonding segment between the rebar and SFRAC.The change in the bond stiffness at the different bonding positions is the main reason for the nonuniform distribution of the bond stress.The uniformity of the bond stiffness in the bonding segment increases by increasing the replacement ratio of the RCA,and 50% is the optimal replacement ratio of RCA.This is also improved by adding steel fibers into recycled aggregateconcrete（RAC）,but their effect decreases when its volume fraction is 2.0%.Furthermore,the relative slip at the loading end increases with the increasing replacement ratio of the RCA and decreases with the increasing volume fraction of the steel fibers.The uniformity of the bond stiffness in the bonding segment is improved with increasing replacement ratio of the RCA and volume fraction of the steel fibers.The peak values of the bond stress in the bonding segment next to the free end increase with increasing replacement ratio of the RCA and has little relation with volume fraction of the steel fibers.The shape of the bond stress and slip curve between the rebar and SFRAC does not change with the bonding positions.Finally,a constitutive model for the bond stress-slip relation of the rebar embedded in the SFRAC is proposed,which considers the influence of the replacement ratio of the RCA and volume fraction of the steel fibers.