Research On The Standardization Design Of Prefabricated CFRP Prestressed Concrete T-Beams

CFRP(carbon fiber reinforced plastic)has excellent material properties.CFRP has advantages such as high tensile strength and good corrosion resistance compared with conventional prestressed steel strands;the excellent properties of CFRP materials make it extensive in the field of bridge engineering.The use of CFRP as a prestressed tendon in prestressed bridge structures can fully utilize its high tensile strength and corrosionresistant material properties,while at the same time improving the mechanical performance and durability of prestressed bridge structures,which are in a harsh natural environment.This is of great significance for the bridge structure.In this paper,CFRP prestressed tendons are used to replace the steel strands of prestressed concrete T-beams.The design principles,design methods,mechanical properties and structural measures of CFRP prestressed concrete T-beams are studied.The difference of mechanical properties between CFRP prestressed concrete T-beam and prestressed concrete T-beam of steel strand was compared.The specific research work is as follows:(1)The value of the design value of tensile strength of CFRP tendons was studied.The calculation method of the value was proposed.The design principle of failure mode and ultimate capacity of CFRP prestressed concrete T-beams was studied,and calculation method of the height of the relative boundary pressure zone,bending capacity,shear capacity was proposed.(2)The design principles and methods of normal use state of CFRP prestressed concrete T-beams were studied.According to the difference between CFRP tendons and steel strands,the calculation method of prestress loss was given;after considering the characteristics of CFRP materials,the different calculation methods of cracking moments,maximum crack widths and post-cracking bending stiffness were compared and analyzed.Calculation method of cracking moment,maximum crack width and bending stiffness after cracking of CFRP prestressed concrete was proposed.(3)A finite element model of a 30 m prestressed concrete T-beam with CFRP tendons and steel strands as prestressing tendons was established,and the mechanical properties of the 30 m prestressed concrete T-beams were compared and analyzed;the differences of the prestress loss,bending capacity,shear load,deflection and section stress of the two were compared and analyzed.(4)By establishing a finite element model of CFRP prestressed concrete T-beam,the effects of different tension control stresses,concrete strength,temperature effect and bond length of CFRP tendons on the mechanical properties of the T-beam were compared.(5)The effect of different laying patterns on the mechanical performance of the structure was compared and analyzed by establishing a finite element model with different laying patterns of CFRP tendons.The difference in tensile strength,shear capacity,T-beam deflection and cross-sectional stress different laying patterns of CFRP tendons were compared and analyzed.(6)Through the research on the CFRP tendon anchorage form,the bond anchorage construction,the anchorage length,the reinforcement structure under the anchorage,the CFRP prestressing tendon and the common tendon structure,the specific structural requirements are given.(7)The standard drawing of CFRP prestressed concrete T-beam was designed based on the full text research results.The differences between the CFRP prestressed concrete Tbeam design drawings and the steel strand prestressed concrete T-beams are given.