CFRP筋黏结型锚具受力性能分析及试验

Analysis and experiment on mechanical performance of bond-type anchorage for CFRP tendons

为了研究碳纤维增强复合材料(carbon fiber reinforced polymer,CFRP)筋黏结型锚具的受力特征,设计了直筒式、内锥式和复合式3种锚具,并采用有限元法分析3种锚具内部筋材和套筒自身的应力分布特征,然后通过试验测试CFRP筋材在锚具内部的应力变化规律和滑移特征,并测试锚具套筒自身的三向应力,研究锚具形式、锚固长度等对锚固性能的影响以及锚固传力机理。研究结果表明:锚具端堵的设置能使受荷端筋材应力峰值处于锚具当中,复合式锚具的传力模式最合理,可以防止内锥式锚具出现切口效应;在加载前期,黏结应力峰值靠近受荷端,随着荷载的持续增加,受荷端逐渐只剩下残余黏结强度,在加载后期,黏结应力峰值靠近锚具自由端;CFRP筋材在自由段的应力-应变基本呈线性关系;锚具的荷载-滑移曲线呈明显的非线性趋势,在加载前期,CFRP筋材的滑移量较小,随着荷载的持续递增,筋材的滑移量迅速增大,当接近破坏时,滑移量明显增加;随着荷载的逐渐增加,筋-胶界面上的黏结应力先增加到峰值,然后其化学胶着力逐渐失效,只剩下残余应力;黏结应力峰值由受荷端逐渐向自由端转移,表现为自由端附近套筒的正应力最大,套筒上的应力分布可以间接反映出CFRP筋材的应力变化情况和滑移情况。

In order to study the mechanical characteristics of bond-type anchorage for carbon fiber reinforced polymer （CFRP） tendons, straight-tube-type, inner-cone-type and composite-type anchorage were designed. In addition, stress distribution characteristics of inner tendon and sleeve itself of three kinds of anchorages were analyzed by using finite element method. Then, stress variation rules and slip features of CFRP tendons in anchorage were tested by experimental methods. Also, three directional stress of anchorage sleeve itself was tested. The effect of anchorage form and anchorage length on anchorage performance and the anchoring mechanism were studied. The results show that peak stress at loading end can be kept inside of anchorage by setting anchorage plug. Load transfer mode of composite anchorage is the most reasonable. Thenotch effect of inner-cone-type anchorage can be prevented in composite-type anchorage. In the early stage of loading, peak value of bonding stress is close to the loading end. With the increase of load, only the residual bond strength gradually exists at the loading end. In the later stage of loading, peak value of loading stress is near the free end of anchorage. The relationship between stress and strain of CFRP tendon at free part shows typical linearity. The bond-slip relationship obviously shows nonlinearity. In the early stage of loading, slippages of CFRP tendons are small. With the increase of load, slippages of CFRP tendons increase quickly. When closed to damage, slippages increase significantly. With the increase of load, bond stress between tendon and colloid firstly increases to a peak, then chemical adhesive force gradually failures, only residual stress exists at last. Peak point of bond stress gradually transfers from loading end to free end, which reflect that the phenomenon that normal stress of sleeve is the largest near the free end. Stress distribution in sleeve of anchorage can indirectly reflect the change of stress and slip of CFRP tendons. 1 tab, 13 figs, 24 refs.