高强CFRP拉索-弯折锚固系统静力性能研究

Study on Static Behavior of High-strength CFRP Cable Bending Anchoring System

为了满足索承结构对拉索索力增长的需求,增加单筋直径和数量来提升索力是一种有效方法,但同时会导致索体直径和盘卷直径过大。为此,基于先前开发的变刚度锚固荷载传递介质,提出一种采用多根高强小直径CFRP筋的弯折锚固系统(简称弯折锚)来同时提升索力和弯曲性能。针对多筋拉索建模复杂以及计算效率低的问题,提出了基于等效圆环的应力释放模型,并利用足尺试验对应力释放模型的可靠性以及锚固方法的有效性进行验证。结果表明:改变单筋间距有利于减小平行锚最外层筋内外侧轴向拉应力差,但对轴向应力和径向应力影响较小。应力释放模型可以有效解决封闭圆环模型的“环箍效应”,使拉索内层筋的环向挤压应力更加趋近于真实的多筋模型。高强CFRP拉索失效模式为整体炸裂式破坏,荷载传递介质几乎没有受到可见的挤压和剪切损伤。应力释放模型对荷载-位移曲线、轴向位移和锚固区拉索轴向应变均具有较高的模拟精度。Φ4-91高强CFRP拉索的实测极限抗拉力为3 393 kN,相应的锚固效率为91%,而锚固效率低的原因在于多筋受力不均匀和未对锚具进行重新设计。自由段拉索轴向应变随荷载的增加而增大,应变片粘贴位置、胶层厚度以及筋材长度误差是导致轴向应变差过大的主要原因。相同荷载下锚固区中心筋轴向应变自加载端至自由端近似线性减小,锚固区30~360 mm范围内中心筋平均剪应力呈缓慢增长趋势,表明变刚度锚固设计有利于缓解拉索剪应力集中。

In order to accommodate the growing demand for cable force in cable-supported structures,increasing the diameter and number of individual bars is considered an effective method for augmenting cable force,thereby resulting in increased cable and coil diameters.Therefore,this paper proposes a dispersed anchoring system(DAS)that utilizes multiple high-strength and small-diameter CFRP bars in conjunction with the previously developed variable-stiffness load transfer component(LTC)to simultaneously enhance cable force and bending behavior.A simplified stress-releasing model(SRM)based on equivalent rings was proposed to address the challenges of complex modeling and low computational efficiency in multi-tendon cable systems.The reliability of the SRM and effectiveness of the DAS were validated through a full-scale experiment.The results indicate that adjusting the spacing between tendons is effective in reducing axial tensile stress discrepancies between the inner and outermost layer tendons in a parallel-tendon anchoring system,while having minimal impact on axial and radial stresses.The SRM effectively addresses the“hoop effect”of the closed ring model,resulting in circular extrusion stress for inner cable tendons that more closely approximates a real multi-tendon model.The high-strength CFRP cable demonstrates a burst failure overall,while the LTC exhibits minimal visible extrusion and shear damage.The load-displacement curve and axial displacement can be accurately simulated using SRM.The ultimate tensile load of the high-strength CFRP cable was measured at 3393kN with an anchoring efficiency of 91%.The relatively low anchoring efficiency may be attributed to the uneven distribution of stress and the type of anchorage employed.The axial strain in the cable increases as load is applied,particularly at the free end,and excessive differences in axial strain can be caused by factors such as gauge placement,adhesive layer thickness,and errors in tendon length.Under the same load,the axial strain of the central tendon in the anchoring zone exhibits a nearly linear decrease from the loading end to the free end.Meanwhile,within a range of 30-360 mm,there is only a slight increase in average shear stress of the central tendon.These findings suggest that variable-stiffness anchoring design can effectively alleviate shear stress concentration.