Abstract
The design of steel chevron-braced frames as per Eurocode 8 is based on the idea that only the braces should buckle and yield during ground motions, while other members should remain elastic. The elastic design of the braced frames is also allowed. However, in both cases, the seismic performance of the frame may be compromised because of premature yielding/buckling of columns. This paper proposes an alternative design procedure that promotes yielding of beams in addition to yielding of braces. This mitigates the vertical unbalanced force transmitted by compressive and tensile braces to the beam and in turn reduces the internal forces of the columns. The result is the overall improvement of the seismic performance owing to the reduction of the number of cases in which failure of the columns occurs before full exploitation of the ductility capacity of the dissipative members. The proposed design procedure is validated by incremental dynamic analyses performed on a set of chevron-braced frames. In particular, the peak ground accelerations of the frames designed by the proposed procedure at the attainment of Significant Damage and Collapse Prevention limit states are determined and compared to those of frames designed according to Eurocode 8. Furthermore, frames designed according to the Eurocodes and to the proposed method are compared in terms of structural cost.
Highlights
Chevron-braced frames have been widely investigated by the scientific community.Studies on these structures were intended either to (i) examine the cyclic response of the brace; (ii) assess the dynamic response of braced structures designed according to seismic codes; or (iii) propose alterative design procedures.Regarding the first issue, experimental activities were carried on braces with a different slenderness and cross-section shape [1,2,3,4] to evaluate their cyclic behaviour and axial displacement capacity [5]
Thispaper paperproposes proposesaadesign designapproach approachfor forchevron-braced chevron-bracedframes framesininlow lowseismicity seismicity of k, whereas cases Q1.0, Q1.5 and Q2.5 provide a probability of exceedance close or larger than 50%
Structures with a 4-storey or 8-storey standing on stiff soil were designed according to the proposed procedure and following the procedures stipulated in Eurocode 8 for dissipative or non-dissipative braces
Summary
Chevron-braced frames have been widely investigated by the scientific community Studies on these structures were intended either to (i) examine the cyclic response of the brace; (ii) assess the dynamic response of braced structures designed according to seismic codes; or (iii) propose alterative design procedures. Experimental activities were carried on braces with a different slenderness and cross-section shape [1,2,3,4] to evaluate their cyclic behaviour and axial displacement capacity [5]. In this regard, the displacement capacity is expressed as a function of the slenderness of the brace, cross-section aspect ratio and width-to-thickness ratio. Based on an analysis of features and the shortcomings of these approaches, a new design method is formulated, proposed and investigated in the paper
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