دانلود رایگان مقاله انگلیسی مقاوم سازی لرزه ای اتصالات تیر-ستون RC غیرلرزه ای با ماهیچه کرنش ناپذیر - تیلور و فرانسیس 2018

Abstract

Many existing RC structures around the world were designed to sustain gravity and wind loads only. Past earthquake reconnaissance have shown that strong earthquakes can lead to substantial damage ranges to non-seismically designed RC buildings, particularly to beam-column joints. This paper presents a novel retrofit method using buckling restrained haunches (BRHs) to improve the seismic performance of such joints. A numerical model for RC joints is introduced and validated. Subsequently, a new seismic retrofit strategy using BRHs is proposed, aimed at relocating plastic hinges and increasing energy dissipation. The results indicate the retrofit method can effectively meet the performance objectives.

7. Conclusions

This paper proposes a novel seismic retrofitting method using BRHs for typical non-seismically designed RC joints. This seismic retrofit method is based on the concept of relocating plastic hinges into beams and increasing energy dissipation under earthquakes. A proof-of-concept test on a reduced scale BRH specimen was conducted and test results indicated that the proposed BRH provides stable energy dissipation capacity, in addition to bracing action, under cyclic loading. A seismic retrofit design methodology for non-seismically designed beam– column joints using BRHs is proposed, and its effectiveness is validated by numerical simulations of two representative cases. Compared with the original non-seismically designed RC joints, the retrofitted joints demonstrate significantly enhanced seismic performance in terms of strength, ductility, and energy dissipation. This is attributed to the load redistribution among different components (i.e., the joints and beams) and the contribution of BRHs. Due to the load redistribution between the joints and beams, plastic hinges are relocated further away from the joint, which consequently reduced the stress and strain in the joints. Damage modes imply that the plastic hinges develop in the beams at the haunch intersection instead of in the columns, and meanwhile shear failure of the joints is avoided, which satisfactorily achieves the retrofit objective. It is to be noted that the BRH design parameters of this study do not represent an optimal design for the retrofitted specimen. An optimal design, as such, was not the purpose of the study It would be possible to optimize the design based on the retrofitted target. The retrofit technique introduced here is regarded as a local strengthening method focusing on damage control in the joint subassembly. The local and global retrofit strategies may be combined in engineering practice to consider different retrofit performance levels for joints and other components.