Papers by Keyword: Time-Dependence

Abstract: Load effects and resistance are supposed to constant in traditional reliability theory. In fact, load effects and resistances change with time because some influent factors of structures change in long working life. Thus, only structures are safe at every moment in working life are structures safe. A synthetical method of qualitative and quantitative analysis is proposed in this paper to study the time-dependence problem of a RC free beam. Firstly, the time-dependence character of a free beam is simulated by ANSYS program. Then, a time-dependent reliability model of the free beam is established, and a program is edited to get values of resistance and index of reliability in different years, thus, the time-dependent reliability of the RC free beam is assessed. The results showed that the value of the resistance decreased 20 percent and the reliability index cut half down after 50 years, so time-dependence should be considered to achieve correct results when the reliability of in-service structures is estimated and new structures are designed.

Abstract: The cyclic deformation behavior of 6061Al-T6 alloy was studied by uniaxial cyclic straining or stressing tests at room and high temperatures. The cyclic softening/hardening feature of the material and its effect on the uniaxial ratcheting occurred under asymmetrical cyclic stressing were discussed. The cyclic deformation behaviors of the material presented at various loading rates and with certain peak and/or valley strain or stress holds were addressed. It is concluded from the experimental results that 6061Al-T6 alloy presents slightly cyclic softening feature, and its cyclic deformation is time-dependent even at room temperature. The ratcheting strain produced at lower stressing rate and with longer hold-time is apparently larger than that at higher stressing rate and with fewer hold-time. Some significant conclusions useful to construct the constitutive model to describe such cyclic deformation behaviors are obtained.