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In order to explore the influence of initial strain on the photo-oxidation aging process of HDPE sheath, the actual strain value of HDPE sheath was calculated based on the design method and the production process of parallel steel wire suspender. The initial strain of HDPE specimen was applied by fixture, and xenon arc lamp accelerated aging test of HDPE were carried out. The results show that after 5000 h xenon arc lamp accelerated aging, the tensile strength, yield strength and secant modulus of the elastic stage of the specimen decrease by 11.19%, 9.15% and 40% respectively. During the aging process, there is no obvious increase or decrease in the elongation at break.There is a critical time in the aging process, when the aging time exceeds the critical time, the yield elongation of HDPE specimen will increase sharply; When the aging time is less than the critical time, the tensile properties of the specimens are basically unchanged with the increase of the initial strain; When the aging time is greater than the critical time, with the increase of initial strain, the tensile strength of the specimen decreases gradually, while the yield strength and secant modulus increase gradually. The critical time increases with the increase of initial strain. In addition, based on the experimental results, the prediction model of HDPE strength and secant modulus is established. The results of this paper lay a foundation for the prediction of the remaining service life of HDPE sheath, which can provide a theoretical basis for the durability design of suspension bridge cable system. • The tensile properties of HDPE sheath for parallel wire suspender after photo-oxidative aging is explored. • The characteristics of elastic stage, strain softening stage, necking stage and orientation hardening stage are analyzed. • With the increase of aging time, the tensile and yield strength and secant modulus in the elastic stage decrease. • When the aging time exceeds a critical time, the yield elongation of the specimen suddenly rises. [ABSTRACT FROM AUTHOR]

Semi-parallel wire suspenders with spherical plain bearings have untwisting under axial force, and the collision in the untwist process bring adverse effects on the structure. To investigate the axial mechanical response of semi-parallel wire suspenders with spherical plain bearings, the equilibrium equations of suspender are deduced by assuming the distribution of steel wire after deformation, the forms of boundary conditions are distinguished according to the use of spherical plain bearing, and the linear equation expressed by equivalent stiffness coefficients is deduced. The Costello theory and finite element modeling are used to verify the proposed calculation method in this paper, and the influence of suspender parameters on the stiffness equivalent coefficient is analyzed. The results show that the proposed calculation method is suitable for multi-layer semi-parallel wire suspenders; the twist angle and the total number of layers of wires have the greatest effect on the stiffness equivalence factor; when the twisting angle is close to 0, the torsional stiffness of suspender is 0.010–0.21 of that of the steel rod with the same section; the axial tensile stiffness of the conventional suspender is basically the same as that of the steel rod with the same section, but the torsional stiffness is only 0.012–0.023 of the steel rod with the same section, and the tension-torsion coupling effect cannot be ignored. The research results provide a concise method to calculate the axial response of semi-parallel wire suspenders, which lays a foundation for the engineering treatment of the untwisting problem of semi-parallel wire suspender using spherical plain bearings. • The axial mechanical response of semi-parallel wire suspenders with spherical plain bearings is investigated. • The expression between axial resultant force, torque and overall strain of twisting structures is deduced and verified. • A concise method to calculate the axial response of semi-parallel wire suspenders is proposed. [ABSTRACT FROM AUTHOR]