The extended N2 method considering higher mode effects in both plan and elevation

Abstract

The extended N2 method has been developed, which takes into account higher mode effects both in plan and in elevation. The extension is based on the assumption that the structure remains in the elastic range when vibrating in higher modes. The seismic demand in terms of displacements and storey drift can be obtained by combining the results of basic pushover analysis and those of standard elastic modal analysis. In the paper, the proposed procedure was summarized and applied to a test example which represents an actual 8-storey reinforced concrete building. The results obtained by the extended N2 method were compared with the results of nonlinear response history analysis and basic N2 analysis without the consideration of higher modes. The extended N2 method was able to provide fair, conservative estimates of response in the case of the test example. In comparison to the basic N2 method, the prediction of seismic demand was greatly improved in the upper part of the building and at the flexible edges.

Analysis in seismic provisions for buildings: past, present and future

“…Baros and Anagnostopoulos (2008) wrote: ''The nonlinear static pushover analyses were introduced as simple methods … Refining them to a degree that may not be justified by their underlying assumptions and making them more complicated to apply than even the nonlinear response-history analysis … is certainly not justified and defeats the purpose of using such procedures. '' In this section, the extended N2 method (Kreslin and Fajfar 2012), which combines two earlier approaches, taking into account torsion (Fajfar et al 2005) and higher mode effects in elevation (Kreslin and Fajfar 2011), into a single procedure enabling the analysis of plan-asymmetric medium-and high-rise buildings, will be discussed. The method is based on the assumption that the structure remains in the elastic range in higher modes.…”

“…the bending moments and shear forces, should be consistent with the deformations. For more details, see Kreslin and Fajfar (2012) and Fardis et al (2015). Note that a variant of Modal pushover analysis is also based on the assumption that the vibration of the building in higher modes is linearly elastic (Chopra et al 2004).…”

Accuracy of Advanced Methods for Nonlinear Static Analysis of Steel Moment-Resisting Frames

“…The equivalent linearization procedures have been modified leading to improved estimates of equivalent period and damping and an adjustment has been introduced to generate a Modified Acceleration-Displacement Response Spectrum (MADRS) that does intersect the capacity spectrum at the Performance Point. Recently, the capacity spectrum method of ATC-40 has been adopted as a seismic evaluation method in the Japanese structural design code and the nonlinear static N2 method [17] has been implemented in both Eurocode-8 [9] and in Italian Seismic Code [10].…”

“…The effectiveness and accuracy of the approximated analysis algorithms are verified through an extensive comparative study involving four nonlinear static procedures: a) N2-EXT: Extended N2 method considering higher mode effects both in plan and in elevation [17]; b) MMPA: Modified Modal Pushover Analysis procedure assuming higher modes as elastic [31]; c) ACSM1: Adaptive Capacity Spectrum Method based on Inelastic Demand Response Spectrum [32]; d) ACSM2: Adaptive Capacity Spectrum Method based on high damping modified acceleration-displacement response spectrum (MADRS) [33].…”

Farklı Deprem Düzeyleri İçin Betonarme Çerçevelerin Plastik Enerji İstemlerinin Belirlenmesi

“…Yapının belirli yatay yükler altında artımsal olarak adım adım itilmesi esasına dayanan statik artımsal itme analizinde, yapının doğrusal olmayan davranışı daha pratik bir şekilde belirlenebilmektedir (Jiang vd., 2010;Reyes ve Chopra, 2011;Sucuoğlu ve Günay, 2011;Mortezaei vd., 2011;Kreslin ve Fajfar, 2012;Camara ve Astiz, 2012;Alıcı vd. 2013;Kaatsız ve Sucuoğlu, 2014 …”