دانلود رایگان مقاله انگلیسی اثربخشی دامپرهای مایع ویسکوز برای بهبود عملکرد لرزه ای ساختمان ها - الزویر 2018

ABSTRACT

The use of fluid viscous dampers (FVDs) together with isolators, frequent in near-fault buildings, is effective in reducing displacements of the isolation layer. Such a hybrid system is also beneficial in the case of inter-storey isolation with the aim of limiting P-Δ effects. However, previous research on base isolation shows that this additional damping may also be detrimental, as inter-storey drifts and floor accelerations may increase. This paper analyses the effectiveness of FVDs for enhanced seismic performance of systems with inter-storey isolation. A seven-floor building, with natural and lead rubber bearings between the second and third levels, was used as a case study, and a multi-objective optimal design was performed to identify the best damper parameters. In particular, time-history analyses with various natural records were carried out and two competing objectives were examined: minimisation of the deflection of the isolation layer and minimisation of the total drift of the superstructure. The results show not only the effectiveness of optimal FVDs but also the fact that their optimal linearity degree depends to a great extent on the non-linear seismic response of the structure, i.e., on the type of earthquake. The simplest design approach, consisting of applying an optimization algorithm for each design accelerogram, did not seem, in this case, to be sufficient to identify the best overall design solution. The design consequences of these findings are discussed.

Conclusions

This work investigates the effectiveness of FVDs for the improved seismic performance of building structures with inter-storey isolation systems. In particular, a seven-floor building was considered as the case study, with natural and lead rubber bearings placed between the second and third floors; a multi-objective optimal design procedure (genetic algorithm NSGA-II) was applied to identify the optimal parameters (damping constants c and exponents α) of dampers which, placed inside the isolation system, allow simultaneous minimisation of isolator displacement OF1 and total drift of the superstructure OF2, while performing time-history analyses with various natural records. The two objective functions (OF) are in conflict with each other, leading to the need for an optimization algorithm. Although the numerical results depend on the structural configuration of the case study, it is reasonable to believe that the potential shown by FVD systems, optimized to work together with an inter-storey isolation system, is a general result.