Nonsymmetrical loading protocols for shear links in eccentrically braced frames

Abstract

The AISC Seismic Provisions for Structural Steel Buildings (AISC 341-16) provide a testing protocol for qualification of link-to-column connections in eccentrically braced frames (EBFs). This symmetrical testing protocol was developed by conducting nonlinear time history analysis on representative EBFs designed according to the International Building Code. Although the testing protocol is intended for qualification of link-to-column connections, many research programs have employed this recommended protocol for testing of shear links. Recent numerical investigations on constructed EBFs and archetype models showed that links can be subjected to one-sided loadings with significantly higher link rotation angles than the codified limits. A numerical study has been undertaken to develop nonsymmetrical loading protocols for shear links in EBFs. Pursuant to this goal, 20 EBF archetypes were designed according to the ASCE7-16 standard. The main parameters investigated were the link length to bay width ratio (e/L), number of stories, type of EBF, and the ground motion level. The archetypes were subjected to maximum considered earthquake and collapse level earthquake as recommended by FEMA P695. The results showed that the history of link rotation is single sided and depends strongly on e/L and the level of ground motion. Nonsymmetrical loading protocols that depend on the aforementioned variables were developed and are presented herein.

H- ve I- enkesitli Avrupa profillerinden teşkil edilen bağ kirişlerinde pekleşme katsayısının incelenmesi

“…Çalışma kapsamında bağ kirişi maksimum kesme kuvveti dayanımının bağ kirişi karakteristik kesme kuvveti dayanımına oranı pekleşme katsayısı olarak dikkate alınmıştır. Bağ kirişlerinin gerekli dönme kapasitelerinden daha yüksek dönme kapasitesine ulaşabildikleri durumlar bulunmaktadır [36]. Ancak bağ kirişlerinin hedef dönme değerlerinin altında veya bu değerlere yakın dönme kapasitelerine sahip olduğu durumlar da raporlanmıştır [8, 20,37].…”

Frictional mid‐spliced shear links for eccentrically braced frames

“…The far-field ground motion set of FEMA P695 5 was used in a number of studies on the response of EBF buildings. [6][7][8] These ground motions were scaled to MCE level or above MCE level with different probabilities of collapse. Kuşyılmaz and Topkaya 6 performed a numerical study on six EBF archetypes designed with current response factors and reported that median LRAs can be as much as 0.23 rad when these archetypes are subjected to ground motions scaled according to 20% probability of collapse at MCE (i.e., 1.09 to 1.15 times MCE).…”

“…The same value increased to 0.38 rad if the deformations of other members were neglected. The far‐field ground motion set of FEMA P695 5 was used in a number of studies on the response of EBF buildings 6–8 . These ground motions were scaled to MCE level or above MCE level with different probabilities of collapse.…”

Cyclic Behavior of Tubular Steel Columns with High Yield‐to‐Tensile Strength Ratio under Asymmetric Loading Protocols

“…Al-Janabi et al [5] carried out nonlinear time-history analyses to investigate the median link rotation angle demands and then, develop loading protocols for short links of eccentrically braced frames (EBF). The results indicated the single-sided nature of link rotation histories and the need to develop asymmetrical loading protocols.…”

“…Suzuki et al [6] proposed a methodology to construct a set of loading protocols which combines the asymmetric lateral loading and varying axial loading as near-collapse protocol for hollow square steel (HSS) columns. Accordingly to Al-Janabi et al [5], they have pointed out that the conventional symmetric loading protocols provide an overall conservative estimation of the seismic demands in individual structural components.…”