دانلود رایگان مقاله انگلیسی "روش مستقیم پنج مرحله ای" برای طراحی لرزه ای اولیه ساختمان ها با میراگرهای ویسکوز - الزویر 2018

ABSTRACT

In the present work a direct procedure for the preliminary seismic design of building structures with added dampers is described which represents the simplification of the so-called “five-step procedure” originally developed in 2010 by some of the authors. The procedure is applicable to yielding frame structures with a generic along-the-height distribution of inter-storey viscous dampers. It is aimed at guiding the structural engineer through the sizing of both viscous dampers and structural elements making use of an equivalent static analysis approach. First, the peak structural response under earthquake excitation is reduced by imposing an overall reduction factor accounting for both the ductility demand and the viscous damping provided by the added dampers. Second, linear damping coefficients are calculated in order to reduce the structural response according to the selected target damping ratio. Then, analytical formulas allow the estimation of peak velocities and forces in the dissipative devices, and an energy criterion is used to identify the non-linear mechanical characteristics of the actual manufactured viscous dampers. Finally, the internal actions in the structural elements are estimated through the envelope of two equivalent static analyses (ESA). At this initial stage of the research, the procedure appears suitable for the preliminary design phase, while correction factors for the higher modes contributions need to be applied to improve its accuracy, especially for high-rise buildings. A numerical verification of the final behaviour of the system by means of non-linear time-history analyses is recommended. An applicative example is finally developed to highlight the soundness of the procedure.

13. Conclusions

A “direct five-step design procedure” for the preliminary seismic design of frame structures equipped with inter-storey viscous dampers has been presented. The procedure is aimed at guiding the structural engineer from the choice and sizing of the added viscous dampers to the evaluation of peak internal actions in both dampers and structural members for their preliminary sizing. It allows to obtain direct estimations/predictions of peak floor displacements, peak inter-storey drifts and velocities, maximum forces in the dampers and maximum internal actions in the structural elements with no need of developing numerical dynamic time-history analyses. The proposed estimates are based on an assumed elastic first mode shape modified through various correction coefficients accounting for higher modes contributions and inelastic frame behaviour. Although the procedure can be further improved through an accurate calibration of those correction coefficients (accounting for higher modes contribution and non-linear frame behaviour), it produces results of sufficient accuracy for the sake of preliminary design of regular moment-resisting frames. Nonetheless, at the present stage, the final design has to be developed through non-linear time-history analyses. Thanks to its simplicity, the proposed procedure can be very helpful to professional engineers not dealing everyday with the seismic design of structures equipped with added viscous dampers and not expert with the development of computer based time-history analyses. At the same time it may be also used as simple tool to check the results of more complex design procedures or even time-history numerical simulations.