دانلود رایگان مقاله انگلیسی دمپرهای اصطکاکی قابل رفع برای اتصالات میله تا ستون فولادی کم زیان - الزویر 2018

ABSTRACT

Beam-to-column joints equipped with friction dampers are promising solutions to improve the performance of steel moment resisting frames due to the possibility to guarantee large dissipation capacity limiting the structural damage under severe seismic conditions. In this paper, the experimental tests and the numerical simulations of two types of joints are shown and discussed with the aim of developing pre-qualified configurations. The friction dampers are designed to be easily removable from both the lower beam flange and the column face by means of bolted connections. The devices are composed of a stack of steel plates conceived to assure symmetrical friction. The friction surface is set in vertical direction in first case and in horizontal direction in the second type. The experimental tests confirmed the effectiveness of both examined joints and the finite element analyses allowed characterizing their local response, thus providing additional insights to improve the design requirements.

Conclusive remarks

The seismic response of steel beam-to-column assemblies equipped with two types of friction dampers has been investigated by means of both experimental tests and finite element simulations. Based on the obtained outcomes, the following remarks can be drawn: • Both types of friction joints provided satisfactory overall performance with stable and predictable hysteretic response, as well as preventing from damage the non-yielding members. However, nonsymmetry response under sagging and hogging was observed. • The joint configuration dictates the level of the response symmetry under sagging and hogging bending. The configuration with vertical friction surface exhibited slightly better response, showing lower degradation under cumulated rotation demand with smaller difference between hogging and sagging resistance. Indeed, the different resistance under sagging and hogging conditions ranges about 25% for the configuration with horizontal friction surface and 15% for that with vertical friction surface. • The FE models accurately predict the response of experimental tests. The models allowed characterizing the local response of the joints, which exhibit some plastic deformations in the bolts and in the connecting L-stubs and T-Stubs. The FE analyses also showed that the joints equipped with the vertical friction damper exhibit plastic deformations lower than the corresponding device with horizontal friction surface. • The variation of the bending capacity of both joint configurations is directly proportional with the bolt pretension force. Therefore, the bolt tightening process needs to be very well controlled because either larger or smaller tightening forces can impair the proper dissipative mechanisms. Indeed, the upper bound values lead to the development of larger forces in the damper, situation that hinders the hierarchy in the joint, while lower clamping forces can lead to sliding in the damper under serviceability conditions. • The randomness of the friction properties has to be as much as possible mitigated and accounted for in the design phase, because this variability can inflict in the joint response and, consequently, the global behavior of the structure.