دانلود رایگان مقاله انگلیسی استراتژی ارتقاء لرزه نگاری غیر تهاجمی برای بار ثقلی اتصالات تیر ستون خارجی - الزویر 2018

abstract

Existing gravity load designed (GLD) structures are vulnerable to seismic event due to their inherent weaknesses. The present study, focuses on the development of non-invasive and feasible strategies for seismic upgradation of these non-seismically designed structures. Three novel schemes, namely (i) single haunch upgradation scheme (U1), (ii) straight bar upgradation scheme (U2) and (iii) simple angle upgradation scheme (U3) are proposed for seismic upgradation of GLD specimens. The efficacy and effectiveness of these upgradation schemes are evaluated by conducting the reverse cyclic load tests on control and upgraded GLD exterior beam-column sub-assemblages. The performance of the upgraded specimens is compared with that of the control GLD beam-column sub-assemblage, in terms of load–displacement hystereses, energy dissipation capacities and global strength degradation behaviour. Tremendous improvement in the energy dissipation capacity to the tune of 2.63, 2.83 and 1.54 times the energy dissipated by the control GLD specimen is observed in single haunch upgraded specimens, straight bar upgraded specimen and simple angle upgraded specimenrespectively. The specimen with single haunch upgradation performed much better compared to the GLD specimens upgraded with the other two schemes, by preventing the brittle anchorage failure, delaying the joint shear damage and redirecting the damage partially towards the beam.

12. Conclusions

The upgradation of typical GLD exterior beam-column subassemblage is carried out using three different novel schemes, namely (i) single haunch upgradation scheme, (ii) straight bar upgradation scheme and (iii) simple angle upgradation scheme. The efficacy of the upgradation schemes is evaluated by conducting reverse cyclic load tests on control and three upgraded GLD exterior beam-column sub-assemblages. The single haunch upgraded GLD specimen SP1-U1 and straight bar upgraded specimen SP1-U2 showed superior hysteretic behaviour with the improved load carrying capacity in both positive and negative cycles compared to that of control GLD specimen SP1. Further, both these upgraded specimens could sustain larger drift ratios and exhibited better hysteretic behaviour when compared to the control GLD specimen. The upgraded GLD specimen SP1-U1 showed far superior performance by preventing anchorage failure, delaying joint failure and succeeding in partially redirecting the damage to the beam. The upgraded GLD specimen SP1-U2 avoided the brittle anchorage failure of the beam bottom reinforcement and exhibited the uniformly degrading hysteretic performance. This also demonstrated its fulfilment of the intended purpose of enhanced seismic performance of GLD beam-column subassemblages, particularly during positive drift cycles. The simple angle upgraded GLD specimen SP1-U3 could be able to shift the anchorage failure of the beam bottom bars from drift ratio of 1.47% (as noticed in the case of control GLD specimen SP1) to 2.2% even though improvement in load carrying capacity in the positive cycles is less when compared to the other two upgradation specimens (SP1-U1 and SP1-U2). However, the load carried by SP1-U3 in the positive cycles is 30% higher than that of control GLD specimen SP1.