Abstract
The paper is devoted to the investigation of the seismic response of eccentrically braced frames characterised by links having different length. In addition, the analysed structures have been designed according to a methodology, already proposed by the authors, aiming to guarantee a collapse mechanism of global type. Therefore, the results of the nonlinear analyses herein presented provide the validation of the proposed design procedure, by testifying that all the designed structures exhibit a global failure mode where all the links are yielded while all the columns remain in elastic range with the exception of the base section of first storey columns, leading to high energy dissipation capacity and global ductility. Furthermore, two different distributions of the link lengths are examined. The first one is characterised by short links with uniform lengths along the height of the structure. The second one is characterised by the use of link elements having different length at the different storeys which are selected to assure the same value of the non-dimensional link length. The seismic response of EB-Frames with such distributions of the link length is investigated by means of both push-over analyses and dynamic non-linear analyses. The comparison of the performances is mainly carried out in terms of plastic hinges distribution, local ductility demand and frame lateral stiffness.
Highlights
It is well known that eccentrically braced frames (EBFs) constitute a suitable structural typology for both interstorey drift limitation and energy dissipation capacity
EBFs are characterised by adequate lateral stiffness, as required to satisfy the serviceability limit state requirements, and high global ductility, as required to assure collapse prevention under severe earthquakes
The main parameter governing the seismic response of such structural typology, both in elastic and post-elastic range, is the length e of the links, which constitute the dissipative zones
Summary
It is well known that eccentrically braced frames (EBFs) constitute a suitable structural typology for both interstorey drift limitation and energy dissipation capacity. The shear action is dominant for e 1.6 Mp/Vp (i.e. in case of short links), while the bending moment becomes more and more relevant as far as the link length e increases, until it becomes dominant for e 3.0 Mp/Vp (i.e. in case of long links) Due to their performance in terms of both stiffness and ductility, short links are in several cases the most suitable choice for seismic-resistant EBFs. the cyclic behaviour of short links is characterised by wide and stable cycles allowing the development of high energy dissipation capacity, provided that adequate web stiffeners are adopted along the element length to prevent web local buckling. The main results of non-linear analyses will be presented and discussed
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