Experimental And Numerical Investigation On Composite CFRP Ground Anchors

Carbon fiber reinforced polymer(CFRP),as a kind of high-performance non-metallic composite material,has been used in aviation,aerospace,automobile and other projects,and gradually developed into the reinforcement,repair and transformation of concrete structures.In recent years,it has been developed rapidly in the field of geotechnical anchorage,which represents the development direction of geotechnical anchorage materials in the future.Compared with reinforced bar,CFRP composite bar has the advantages of light weight,high strength,corrosion resistance,convenient construction and so on.It is one of the effective ways to solve the problem of anchor corrosion by using FRP bar instead of reinforced bar.Based on the literature review,laboratory tests and numerical simulation on CFRP composite anchors,the load transfer mechanism and anchoring performance were studied in this thesis.The main works and conclusions are summarized below:(1)Based on the existing composite anchorage,an improved carbon fiber composite anchorage is designed,and the anchorage performance of the composite anchorage is studied through the pull-out test to investigate the improved CFRP composite anchor’s anchoring performance,which include the ultimate load,the measured point strain of the steel sleeve,and the final overall failure form of the anchor.Results showed that the improved composite anchor nut’s vertical fastening force effectively prevents clip slip without applying pretension force,so the improved composite anchor’s anchoring performance is greatly improved when compared to conventional composite anchor anchoring performance.The load has a positive relationship with the total amount of CFRP rib slip.The ribbed material’s surface form has a significant impact on anchoring performance,and when the ribbed material is ribbed,the shear stress between the bonding material and the rib material is greater,increasing the anchoring efficiency by14.3%.(2)The soil and ground anchor interaction was studied using the finite element method under various overburden pressures.The soil and anchor interaction,as well as soil behavior,are modeled using the Drucker-Prager model,which allows for sliding and loss of contact during loading.The numerical modeling method applied to the previous numerical and field test results using Midas GTS NX FEM to the new CFRP composite anchor in compression as well tension and then subjected to pullout loads to ensure the accuracy of the numerical analysis.Results showed that the soil-grout and grout-CFRP rebar interface modeling has a significant impact on the findings of computational simulations of the load transfer process of ground anchors.(3)A case study of the Menhyiaa shopping mall was examined.Shoring the excavation with a pile anchored by CFRP composite anchors is an important part of site works.The numerical calculations of both the conventional ground anchors and the CFRP composite ground anchor were compared using MIDAS GTS NX to model the real situation.Results showed that the maximum horizontal and vertical displacements are both within 8 meters of the pile at the top of the pit.It is explained that,in order to prevent the foundation pit from being destroyed,it is necessary to prohibit stacking heavy objects within 8m of the pile at the top of the pit.Moreover,it can be concluded that CFRP composite bars are more suitable for practical engineering than conventional steel anchors after a comprehensive and detailed comparison of displacement(deformation)and stress as well as the cost on the market.