Experimental study on axial compression performance of circular medium-long timber columns strengthened with CFRP sheets and near surface-mounted steel bars
To study the axial compression performance of medium-long circular timber columns strengthened with carbon fiber reinforced polymer(CFRP)sheets and near surface-mounted steel bars,8 specimens were conducted and tested under axial compression force.The load-displacement curves and load-strain curves were obtained.Furthermore,the effects of the number of embedded steel bars and the wrapping form of CFRP sheets on the axial compression performance of medium-long timber columns were analyzed.The test results indicate that medium-long circular timber columns show two failure modes under axial compression,including crushing failure and bending failure,both of which occur in the initial defect area with wood knot concentrated.The bending performance of timber columns can be effectively improved with embedded steel bars.The axial compressive bearing capacity of timber columns is increased by 58.11％-100.68％,the longitudinal strain is reduced by 12.03％-28.89％,and the transverse deformation is reduced by 20.72％-38.57％ at the load of 965 kN.Wrapped with CFRP sheets,the timber column is subjected to triaxial compression,and the axial compressive load capacity of the timber column is increased by 65.19％,and the longitudinal and transverse strains under the same load were reduced by 8.7％ and 67.02％,respectively,at the load of 965 kN.The composite strengthened timber columns maximized the use of the confinement effect of CFRP sheets and the bearing effect of steel bars.Its axial compressive capacity can be increased by 45.66％-121.03％,the longitudinal strain under the same load is reduced by 19.24％-28.49％,the transverse strain is reduced by 34.05％-79.93％,and the ductility can be increased by 22.86％ at the load of 965 kN.Based on the theory of composite reinforcement,the experimental data was fitted,and a calculation formula was proposed to estimate the axial compression bearing capacity of medium-long circular timber columns.The calculated values were compared with the experimental values,and the results are in good agreement,which verifies the reliability of the calculation formula.
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