工程科学与技术2025，Vol.57Issue(6)：201-212,12.DOI:10.12454/j.jsuese.202301006
FRP筋-变刚度夹片锚具静力性能研究
Study on Static Behavior of FRP Tendon-Variable Stiffness Wedge Anchorage
摘要
Abstract
Objective The fiber-reinforced polymer(FRP)tendon possesses high specific strength,good corrosion resistance,and high creep rupture stress,making it an ideal material to resolve the critical issues of excessive weight and corrosion in prestressed steel bars or strands.However,develop-ing a novel anchorage with high connection efficiency is essential due to the anchoring challenges associated with anisotropic FRP tendons.The second-generation variable-stiffness wedge(VSW)anchorage,referred to as the second-generation anchorage,is developed to address the limita-tions of the first-generation VSW anchorage,including size,assembly complexity,cost,and wedge follow-up,while maintaining comparable an-choring performance.The development cycle of new anchorages can be significantly shortened by verifying the universal applicability of the second-generation VSW anchorage to various FRP tendons,enhancing engineering practicality and cost-effectiveness. Methods Firstly,three types of epoxy resin cast bodies modified with quartz sand,basalt fiber,and carbon fiber,respectively,were prepared to evaluate their compressive behavior.The failure mode and load-displacement curve of the cast bodies were analyzed,and the compressive str-ength and elastic modulus were calculated based on the testing standards.Secondly,the VSWs were manufactured using the molding method.Composite layers consisting of chopped fibers impregnated with vinyl resin and bidirectional fiber cloth were alternately stacked to enhance struc-tural integrity.The layered materials were compression-molded at 120 ℃ for 20 minutes using a hydraulic press.Post-machining involved angu-lar cutting of high-modulus segments followed by surface roughening to improve interfacial bonding.A dual-material system(quartz-modified resin and epoxy resin)was cast in a split mold for ambient curing.A 0.03 mm stainless steel foil was epoxy-bonded to the collet surface to reduce friction and enhance wedging synchronization with FRP tendons.Thirdly,the end-splitting and surface sandblasting anchoring methods were uti-lized to investigate the tensile properties of BFRP and CFRP tendons.Fourthly,an auxiliary set of steel wedges was installed at the end of the VSW anchorages to achieve synchronous wedging action of multiple wedges.Three types of anchorages were compared:the first-generation an-chorage,the second-generation anchorage,and the stainless steel wedge anchorage.The static anchoring performance of these anchorages was evaluated through static tensile tests. Results and Discussions The findings indicated that the displacement corresponding to the maximum load of the quartz sand-modified resin de-creased with the increasing mass fraction of quartz sand compared to pure resin.This behavior was attributed to the resin matrix's dominant con-tribution to deformation,where reduced resin content diminished the matrix's deformation capacity.In contrast to both pure resin and quartz sand-modified resin,the chopped fiber-modified resin exhibited superior load-bearing capacity and enhanced post-peak load retention.This improve-ment primarily resulted from the inherent high strength of the fibers and the effective constraint on transverse deformation and crack propagation achieved through the randomly distributed chopped fibers,which collectively improved the modified resins'strength and modulus.The compres-sive strength and elastic modulus of the pure resin were measured as 106.6 Mpa and 3.1 Gpa,respectively.For the quartz sand-modified resin,the compressive strength initially decreased and then increased with rising sand content,rather than exhibiting a monotonic growth trend.When main-taining identical preparation processes and reinforcement materials,the accuracy of the compressive strength was influenced by void defects and size effects.Subsequent optimization was achieved through vacuum degassing to mitigate these interfacial imperfections.The processes of end splitting and surface sandblasting were beneficial for enhancing the interfacial bonding capacity between the FRP tendons and resin.The small steel wedge anchorage with a limiting action effectively addressed the issue of asynchronous sliding among multiple VSWs,and the stainless steel sheet attached to the outer surface of the VSWs contributed to improving their sliding capability with the FRP tendons.The variable-stiffness design was advantageous in mitigating stress concentration in the FRP tendons within the anchoring area.The anchoring efficiency(ηa)for roundϕ7 BFRP tendons,round ϕ10 BFRP tendons,and round ϕ10 CFRP tendons using the second-generation anchorages was recorded as 88％,86％,and 99％,respectively.When BFRP tendons were anchored,the anchoring efficiency of the second-generation anchorages significantly surpassed that of the steel wedge anchorages(ηa=78％)and approached that of the first-generation anchorages with larger anchorage size(ηa=91％).When CFRP tendons were anchored,the anchoring efficiency achieved by the second-generation anchorages remained comparable to that at-tained by the stainless steel wedge anchorage(ηa=107％). Conclusions For the second-generation anchorage,the VSW consists of three segments with varying elastic moduli:a low-elastic-modulus seg-ment made of epoxy resin,a medium-elastic-modulus segment composed of quartz sand-modified epoxy resin(with a quartz sand to resin mass ratio of 100％),and a high-elastic-modulus segment incorporating vinyl resin-impregnated chopped fibers and bidirectional fiber fabric.The end splitting combined with surface sandblasting effectively enhances the bond strength between smooth FRP tendons and resin.The auxiliary steel wedge anchorage resolves the asynchronous wedging problem of multiple VSWs,while externally bonded stainless-steel thin sheets improve the synchronous wedging capability of VSWs with FRP tendons.The variable-stiffness design significantly mitigates stress concentration in FRP bars within the anchorage zone.For BFRP tendons,the second-generation anchorage achieves substantially higher efficiency than stainless-steel wedge anchors while approaching the performance of larger first-generation anchors.For CFRP tendons,the efficiency not only exceeds the code-specified requirement of 90％but also matches that of stainless-steel wedge anchorages.Future work will focus on continuous optimization of variable-stiffness wedge dimensions and materials,as well as refining manufacturing processes to reduce production costs.Further investigation of the impact performance of FRP tendon-VSW anchorages will also enhance their engineering applicability.关键词
桥梁工程/BFRP筋/CFRP筋/变刚度夹片锚具/锚固效率Key words
bridge engineering/BFRP tendon/CFRP tendon/variable-stiffness wedge anchorage/anchoring efficiency分类
交通运输引用本文复制引用
周竞洋,汪昕,丁里宁,张晓非,李元琪,吴智深..FRP筋-变刚度夹片锚具静力性能研究[J].工程科学与技术,2025,57(6):201-212,12.基金项目
国家自然科学基金青年基金项目(52208233) （52208233）
国家自然科学基金面上项目(52278244) （52278244）
江苏省自然科学基金青年基金项目(BK20220855) （BK20220855）
中国博士后科学基金面上项目(2022M720726) （2022M720726）
江苏省前沿技术研发计划(BF2024011) （BF2024011）
