دانلود رایگان مقاله انگلیسی در مورد رفتار لرزه ای سازه های فولادی مهاربندی شده متحد المرکز تنش واحد - الزویر 2018

ABSTRACT

This paper summarizes the estimated results from three-dimensional non-linear time-history seismic analysis of tension-only concentrically braced steel structures. The braces of these type of steel structures are properly detailed in order to sustain only tension and no compression. In particular, a cheap and easy to fabricate brace detailing allows the brace to slide when in compression and to develop a resisting force when in tension. A comparison between steel structures designed with the proposed tension-only braces and with buckling-restrained braces is performed on the basis of commonly used seismic response and demand indices. It is shown that tension-only and buckling-restrained braced structures may exhibit similar behavior. Nevertheless, column overstress in compression is larger for the tension-only braced structures. Preliminary conclusions regarding the use of the proposed tension-only braces as a seismic force-resisting system for steel structures are drawn.

Conclusions and future needs

In this paper, the concept of tension-only concentrically braced steel structures is revisited and it is shown that common steel braces can be detailed to sustain only tension and no compression. Therefore, usual buckling problems associated with steel braces are eliminated. The proposed brace detailing is considered to be cheap and easy to fabricate. Various seismic response and demands results are presented and from them it can be generally assessed that tension-only braced structures have a comparable behavior to the BRB structures. As holds for BRB structures, tension-only braced structures face the issue of significant residual displacements. The threshold RIDR value of 0.5%, accepted by the engineering community, is surpassed for both types of structures. But for the tension-only braced structures, even more important is the overstress in compression induced to the columns of the lower storeys, something that the present work highlights but cannot, at the time being, propose a remedy for it. On the other hand, an appropriate slot clearance ensures that compression to the tension-only braces is not developed. The level of the friction forces needed to be surpassed before sliding is not modeled, but it is deemed that its contribution is small and does not substantially alter the seismic response results obtained herein. However, the impact of the pin to end of the slotted hole when tension is developed is a matter of further investigation. A hardening or a quenching procedure for the steel surfaces near to the end of the slotted holes in conjunction with a detailed finite element analysis is suggested in order to assess the stress field around the slot during impact. Taking also into account, that the philosophy of current seismic design codes precludes any recommendation for impact forces in the design of conventional (i.e., those that are not equipped by energy dissipation devices or by other kinds of seismic fuses) structures, the aforementioned investigation on impact forces, even it is mandatory, may not be easily accepted by the engineering community.