Numerical studies on eccentrically braced frames

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Tezin Türü: Doktora

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, İnşaat Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2014

Öğrenci: AHMET KUŞYILMAZ

Eş Danışman: CEM TOPKAYA, AFŞİN SARITAŞ

Özet:

Numerical studies were performed on eccentrically steel braced frames to ascertain seismic performance factors and to examine dynamic characteristics of eccentrically braced frames (EBF). Pursuant to this goal a computer program which facilitates EBF designs was developed. In the first phase, the approximate period formula given in ASCE7-10 was evaluated and a technique based on global deformation characteristics was developed to improve the fundamental period estimates for EBFs. The results indicate that the developed method accurately predicts the fundamental period and reduces the scatter by a significant amount when compared with the estimations of the approximate formula. In the second phase, an analytical study on the design overstrength of EBFs was performed. The results reveal that designed frames have on average higher overstrength values when compared with the codified value. Afterwards, a numerical study was performed to evaluate the displacement amplification factor (Cd) given in ASCE710 for EBFs and the rigid-plastic mechanism used for calculating link rotation angles. Based on the results, EBFs were redesigned and analyzed using a new set of Cd factors and a more accurate procedure to estimate link rotation angles. Finally, response modification factors of EBFs were evaluated utilizing a novel procedure given in FEMA P695. The results reveal that collapse probability of link sections go beyond fifty percent for procedure defined in FEMA P695. Six archetypes were redesigned using the proposed modifications to Cd factor and reevaluated using FEMA P695 methodology. The results indicate that proposed modifications are adequate to satisfy the target collapse probability.