اثر کاربرد میکروسیلیس در بتن مصرفی بر شکل پذیری اتصال خارجی تیر-ستون بتن مسلح در دمای محیط و پس از تحمل حرارتهای ناشی از آتش سوزی

The present study has been conducted with the main objective of evaluating the influence of employing micro-silica in the mix proportion of concrete on the ductility behavior of exterior reinforced concrete (RC) beam-column joint (BCJ) at ambient temperature as well as after exposure to high temperatures of fire. In this way, six similar scaled RC BCJ specimens were fabricated under two conditions of utilizing and not utilizing micro-silica in concrete. BCJ specimens were subjected to cyclic loading at two conditions of ambient temperature and ۲۴ hours after exposure to the heating regimes with target temperatures of ۴۰۰ and ۶۰۰. Based on results at the ambient temperature, the utilization of micro-silica was accompanied by the predominant mechanism of beam rocking movement in the flexural failure mode, negligible changes in the ductility factor, and noticeable enhancement in the energy dissipation. Under the applied heating regimes, relative reductions in the mentioned parameters (relative to the corresponding counterparts at ambient temperature) were intensified for the BCJs due to the ۷% replacement of cement by micro-silica, so that under the effect of the ۶۰۰ heating regime, relative reduction values in ductility factor, cumulative energy dissipation, and maximum load increased by ۱۳.۶%, ۲۶.۰%, and ۱۳.۴% and reached to considerable reductions of ۵۱.۹%, ۶۴.۱%, and ۴۶.۷%, respectively. Also, despite the observation of shear failure mode for all heated BCJs, employing micro-silica led to noticeable changes in the details of damage mechanisms under the effect of the ۶۰۰ heating regime and led to more brittle failure at the joint core.

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اتصال خارجی ، بتن مسلح ، میکروسیلیس ، شکل پذیری ، حرارت ، آتش سوزی