| The use of anchor cable technology to enhance the strength and stability of rock and soil is a common means in the field of geotechnical engineering.The core of the work of this technology is the bonding of the anchor cable to the concrete material.The effective bonding between steel strand and concrete is the basis of the interaction between the two.The two-transfer stress and coordinate deformation through this very complex interaction.Interfacial bonding between steel strand and concrete is an important part of the overall performance of prestressed anchor structures,so the study of interfacial bonding is of great significance.However,there are relatively few research results on the interfacial bonding between steel strand and reactive powder concrete,and the research method is still limited to the traditional mechanical test,for which the computational theory and the combination of non-destructive testing technology research is less.Therefore,it is of great engineering application value and theoretical significance to carry out the applied research on the interfacial bonding problem between steel strand and reactive powder concrete.(1)The pull-out tests of prestressed steel strands with basalt fiber reactive powder concrete(BFRPC)and M40 ordinary cement mortar(PC)were carried out.The bond properties of steel strands under three nominal diameters of 12.7 mm,15.2mm and 17.8 mm,two concrete materials and three anchorage lengths(100 mm,200 mm and 300 mm)were studied.According to the experimental phenomena,the bond failure mode is divided into pull-out failure and splitting failure,and the bond-slip curve is divided into linear stage,development stage and slip(pull-out/splitting)stage.Analyzing the difference of bond performance under different test variables,the initial bond stress and ultimate bond stress of strand are negatively correlated with anchorage length and strand diameter,and positively correlated with material strength.(2)According to the characteristics of the bond-slip curve,the bond strength,strand diameter and compressive strength of concrete material are taken into account to obtain the expressions for bond-slip calculation of BFRPC and steel strand,and finally to establish the analytical model of bond stress-slip relationship between steel strand and basalt fiber activated powder concrete that can effectively distinguish the linear and slip sections.(3)Considering the rotational slip characteristics of the steel strand structure so that it exists in the concrete structure pull-out process,the ultimate bond strength calculation model of the steel strand in the BFRPC under the rotational pull-out failure mode is modified,and the calculation results and verification of the modified model,the calculation error can be controlled within ±8% on both sides of the theoretical calculation control line,and the model accuracy is good.(4)The distribution law of acoustic emission characteristic parameters(Energy,Amplitude and Ringing count)is closely related to the damage process of steel strand and concrete material during drawing damage.And by comparing and analyzing the RA-AF values,it is clear that shear cracks and tensile cracks in the steel strand-concrete drawing process are developed during the loading process,and the shear cracks mainly occur near the concrete at the interface;while the tensile cracks are macroscopically reflected as cracks perpendicular to the loading direction.(5)The acoustic emission Ib-value derived from Gutenberg-Richter theory is used to evaluate the damage process of the anchorage system.According to the Ibvalue,the various stages of crack development of steel strand concrete material under different stress states are identified.BFRPC can inhibit the initiation and development of initial cracks to a certain extent while ensuring the overall bond strength,which proves its superiority as an anchor cable anchoring medium. |
PDF Full Text Request