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<p>The evolution of Iran’s Seismic Design Standard No. 2800, including the transition from the fourth to the draft fifth edition, has largely relied on linear analyses with limited nonlinear verification, leaving uncertainty regarding the effects of recent revisions on actual seismic performance. This issue is particularly relevant for Special Concentrically Braced Frames (SCBFs), which are widely used yet insufficiently evaluated within performance-based frameworks. To address this gap, this study presents a nonlinear assessment of SCBF systems designed according to the fourth and fifth editions of Standard 2800, focusing on three key revisions: the response modification factor (R), the approximate fundamental period coefficient, and the importance factor. Five representative SCBF archetypes, ranging from 2 to 14 stories, were designed in ETABS and modeled in OpenSees. Nonlinear static and dynamic analyses were performed under 44 far-fault and 50 near-fault ground motion records following the FEMA P695 methodology. Engineering demand parameters, including peak and residual interstory drift ratios, peak floor accelerations, deflection amplification ratios, and normalized story-shear participation, were evaluated, while cumulative and probability density functions quantified response variability. Results indicate that linear analyses predict a 7–13% reduction in design base shear for mid-rise and tall frames under the fifth edition; however, nonlinear responses show improved post-buckling stability and reduced mean PIDR and RIDR due to deformation redistribution rather than force reduction. Short-period frames exhibit amplified nonlinear drift under near-fault pulse-type motions, with Cd-normalized ratios exceeding unity, whereas longer-period frames show normalized interstory drift ratios of 0.8–0.9, indicating conservative deformation estimates. Far-fault records produce pronounced upper-story acceleration amplification, confirming that acceleration-controlled performance remains critical in tall SCBFs.</p>

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Seismic performance evaluation of SCBF systems designed under Iran’s seismic design provisions (standard 2800) using FEMA P695 methodology

  • 期刊论文

  • 发表日期：

    2026年5月4日

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  • Amirali Hadinejad,
  • Abazar Asghari

摘要

The evolution of Iran’s Seismic Design Standard No. 2800, including the transition from the fourth to the draft fifth edition, has largely relied on linear analyses with limited nonlinear verification, leaving uncertainty regarding the effects of recent revisions on actual seismic performance. This issue is particularly relevant for Special Concentrically Braced Frames (SCBFs), which are widely used yet insufficiently evaluated within performance-based frameworks. To address this gap, this study presents a nonlinear assessment of SCBF systems designed according to the fourth and fifth editions of Standard 2800, focusing on three key revisions: the response modification factor (R), the approximate fundamental period coefficient, and the importance factor. Five representative SCBF archetypes, ranging from 2 to 14 stories, were designed in ETABS and modeled in OpenSees. Nonlinear static and dynamic analyses were performed under 44 far-fault and 50 near-fault ground motion records following the FEMA P695 methodology. Engineering demand parameters, including peak and residual interstory drift ratios, peak floor accelerations, deflection amplification ratios, and normalized story-shear participation, were evaluated, while cumulative and probability density functions quantified response variability. Results indicate that linear analyses predict a 7–13% reduction in design base shear for mid-rise and tall frames under the fifth edition; however, nonlinear responses show improved post-buckling stability and reduced mean PIDR and RIDR due to deformation redistribution rather than force reduction. Short-period frames exhibit amplified nonlinear drift under near-fault pulse-type motions, with Cd-normalized ratios exceeding unity, whereas longer-period frames show normalized interstory drift ratios of 0.8–0.9, indicating conservative deformation estimates. Far-fault records produce pronounced upper-story acceleration amplification, confirming that acceleration-controlled performance remains critical in tall SCBFs.