Testing Protocol for Short Links in Eccentrically Braced Frames

Richards, P. W.; Uang, Chia‐Ming

doi:10.1061/(asce)0733-9445(2006)132:8(1183)

Cited by 131 publications

(97 citation statements)

References 11 publications

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“…The difference is likely due to the web haunch plates located at the outer edges of the flange for the primary links, where the proof-of-concept test had a gusset at mid-width of the flange, away from the web-to-flange weld. Research by Richards and Uang (2003) indicated that the loading protocol for EBF links in the 2002 AISC Seismic Provisions is overly demanding in terms of the number of high rotation cycles it requires. As such, they proposed a new loading protocol that has been adopted in the 2005 AISC Seismic Provisions that more realistically represents the maximum rotation demand EBF links must sustain.…”

Section: Link Testing -Resultsmentioning

confidence: 99%

“…The supplementary link with cross-section 2, Specimen AX2L1.6, was tested using the loading protocol specified in the recent 2005 AISC Seismic Provisions (AISC 2005). This protocol was developed by Richards and Uang (2003) considering tabulated cumulative plastic rotation and cumulative energy dissipation demand from various eccentrically braced frames subjected to many ground motions. The protocol requires more cycles at lower rotation levels and fewer cycles at larger rotations relative to the protocol of the 2002 Seismic Provisions.…”

Section: Link Testing -Specimensmentioning

confidence: 99%

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Development of Self-Stabilizing Links for Eccentrically Braced Frames

Berman

Bruneau

2007

New Horizons and Better Practices

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This paper highlights aspects of the development of self-stabilizing links having tubular cross-sections for use in eccentrically braced frames (EBF's). EBF's utilizing this type of link could be used in bridge piers or other applications where lateral bracing to prevent lateral torsional buckling is difficult to provide. The development of design recommendations for these types of links consisted of three parts, namely, a proof-ofconcept experiment, a finite element parametric study, and testing of links with various cross-sectional properties and lengths; the latter two parts are discussed in this paper. The finite element parametric study involved over 200 links with various cross-sections, lengths, and yield strengths and resulted in recommendations for compactness ratio limits for webs and flanges of links with tubular cross-sections which were valid for a range of typical steel yield strengths. Links with three different tubular cross-sections having compactness ratios near and well below the proposed limits were then investigated experimentally. These links also had various lengths covering the full range of link behavior (i.e., shear to flexural dominated yielding). Fourteen links in total were tested. The results indicated that the proposed design recommendations were adequate to ensure tubular links can achieve plastic rotation levels equivalent to the maximum allowed for wide-flange links considering the loading protocol from the 2005 AISC Seismic Provisions.

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Section: Link Testing -Resultsmentioning

confidence: 99%

Section: Link Testing -Specimensmentioning

confidence: 99%

Development of Self-Stabilizing Links for Eccentrically Braced Frames

Berman

Bruneau

2007

New Horizons and Better Practices

View full text Add to dashboard Cite

show abstract

“…The Large Magnitude-Short Distance (LMSR) bin caused the most critical structural response and was therefore utilized in subsequent studies which required a representative set of ordinary ground motion records. This included the work of Richards et al (Richards et al 2006) for the development of cyclic loading and testing protocol for eccentrically braced frames. LMSR earthquakes were defined as those with moment magnitude between 6.5 and 7.0 and distance from fault between 13km and 30km and included 20 records.…”

Section: Representative Crustal Earthquake Setmentioning

confidence: 99%

Bridge Seismic Retrofit Measures Considering Subduction Zone Earthquakes

Dusicka¹,

Bazaez²,

Knoles³

2015

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Research was conducted to investigate the effect of subduction zone earthquakes on structural damage. The study suggests that large magnitude ground motions of long duration have the potential of significantly increasing the number of inelastic excursions and consequently incur more extensive structural damage as compared to ground motions with similar elastic spectral demands but of shorter duration. This increase in demand plays a crucial role in the Pacific Northwest where a mega subduction zone earthquake is impending. Typical reinforced concrete bridge bents constructed in the 1950 to mid-1970 in the State of Oregon were designed and built with minimum seismic considerations. This resulted in inadequate detailing within plastic hinge zones, leaving numerous RC bents highly susceptible to damage following an earthquake. In this study, the cyclic performance of an asbuilt RC square column and a reinforced concrete bridge bent retrofitted using buckling restrained braces (BRBs) was experimentally evaluated using quasi-static cyclic loading protocols aiming to reflect subduction zone earthquake demands up to displacement ductility. The buckling restrained braces were designed as replaceable elements in order to take the earthquake-induced energy and dissipate it through nonlinear hysteretic behavior. Two BRB designs were considered in the study in an effort to assess the influence of BRB stiffness on the overall structural performance. The results of these large-scale experiments successfully demonstrated the effectiveness of utilizing buckling restrained braces for achieving high displacement ductility of the retrofitted structure, while also controlling the damage of the existing vulnerable reinforced concrete bent up to the design performance levels. The potential of improving the overall seismic behavior and the design performance levels with BRBs offers structural design professionals a viable method for performance driven retrofit of reinforced concrete bents. 17. Key Words Subduction zone earthquakes, reinforced concrete bridge bents, plastic hinge zone, performance levels, bridge seismic retrofit, quasi-static loading protocol, buckling restrained braces.18. Distribution Statement: Copies available from NTIS, and online at

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“…Additionally, elastic out-of-plane slab stiffness outside the link regions may help reduce residual frame drifts, providing a kind of self-centering behavior. While several analytical studies have investigated seismic demands in EBF systems and components (Ricles and Popov, 1994;Richards and Uang, 2006;Richards, 2009;Kanvinde et al, 2012), the majority of these studies either neglect the concrete slabs or replace the concrete slabs by rigid-diaphragm constraints.…”

Section: Introductionmentioning

confidence: 99%

Effect of Slab Stiffness on EBF Link Rotation Demands and Implications for Link Ultra Low-Cycle Fatigue Susceptibility

Prinz

Sousa

2014

Structures Congress 2014

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This study aims to quantify slab contributions in eccentrically braced frames (EBFs) by investigating the dynamic performance of two 3-story EBF configurations with and without concrete slabs: one configuration having long (flexural yielding) links and the other having shorter (shear yielding) links. Particular effort is spent investigating the relative accumulation of ultra low-cycle fatigue damage within the link regions during dynamic loading. All slab and major frame geometries are modeled using shell elements. Linear springs and nodal constraints model the discrete slab-to-beam interactions. Recorded earthquake ground accelerations, scaled to design-level intensities, load the EBFs. Ultra low-cycle fatigue damage is investigated using a calibrated micro-mechanics based ductile fracture model. Results indicate reduced system-level frame demands (inter-story drift, residual drift, and link rotation) due to increased system stiffness from the concrete slabs. Reductions in these demands were larger for EBFs with long (flexural yielding) links as compared to the short (shear yielding) links. Even with reduced rotation demands, EBF models with slabs sustained similar link fatigue damage, as compared with the bare-steel models, due to increased plastic strain demands presumably from a neutral axis shift.

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Testing Protocol for Short Links in Eccentrically Braced Frames

Cited by 131 publications

References 11 publications

Development of Self-Stabilizing Links for Eccentrically Braced Frames

Development of Self-Stabilizing Links for Eccentrically Braced Frames

Bridge Seismic Retrofit Measures Considering Subduction Zone Earthquakes

Effect of Slab Stiffness on EBF Link Rotation Demands and Implications for Link Ultra Low-Cycle Fatigue Susceptibility

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