Abstract
Extensive studies have confirmed the good performance of the N2 method, recommended by Eurocode8, when performing pushover analyses in regular structures. However, this procedure shows lack of accuracy in predicting the torsional motion of plan-asymmetric buildings. In order to overcome this problem, Peter Fajfar and his team have proposed an extension of the method based on a combination of a pushover analysis and of an elastic response spectrum analysis. Since definitive answers about this topic have not yet been reached, this paper intends to proceed the study applying the extended N2 method to real existing RC buildings. Three real plan-asymmetric buildings with three, five and eight storeys were assessed. The results obtained with the extended N2 method were compared with the ones evaluated by means of the original N2 and with the nonlinear dynamic analysis through the use of semi-artificial ground motions. The analyses were performed for different seismic intensities in order to evaluate the torsional response of the building through different stages of structural inelasticity. The results obtained show that the extended N2 method generally reproduces in a very good fashion the real torsional behavior of the analyzed buildings. The conclusions herein outlined, added to the ones already published by the aforementioned authors, seem to confirm that the extended N2 method can be introduced in the next version of Eurocode8 as a nonlinear static procedure capable of accurately predicting the torsional response of plan-asymmetric buildings.
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References
Bento R, Bhatt C, Pinho R (2010) Using nonlinear static procedures for seismic assessment of the 3D irregular SPEAR building. Earthquakes Struct 1(2): 177–195
Bhatt C, Bento R, Pinho R (2010) Verification of nonlinear static procedures for a 3D plan-irregular building in Turkey. Proceedings of the 14th European conference on earthquake engineering, Ohrid, Macedonia
CEN (2004) Eurocode8: design of structures for earthquake resistance. Part 1: general rules, seismic actions and rules for buildings. EN 1998-1:2004 Comité Européen de Normalisation, Brussels, Belgium
Chopra AK, Goel RK (2004) A modal pushover analysis procedure to estimate seismic demands for unsymmetric-plan buildings. Earthquake Eng Struct Dyn 33: 903–927
Erduran E, Ryan K (2010) Effects of torsion on the behavior of peripheral steel-braced frame systems. Earthquake Eng Struct Dyn. doi:10.1002/eqe.1032
Fajfar P, Fischinger M (1988) N2—a method for non-linear seismic analysis of regular buildings. Proceedings of the 9th World conference in earthquake engineering, vol 5, Tokyo-Kyoto, Japan, pp 111–116
Fajfar P, Marusic D, Perus I (2005) Torsional effects in the pushover-based seismic analysis of buildings. J Earthquake Eng 9(6): 831–854
Fajfar P (2000) A nonlinear analysis method for performance-based seismic design. Earthquake Spectra 16(3): 573–592
Fardis MN (2002) Design of an irregular building for the SPEAR project—description of the 3-storey structure. Research report University of Patras, Greece
Fardis MN, Negro P (2006) SPEAR—seismic performance assessment and rehabilitation of existing buildings. Proceedings of the international workshop on the SPEAR project, Ispra, Italy
Filippou FC, Popov EP, Bertero VV (1983) Modelling of R/C joints under cyclic excitations. J Struct Eng 109(11): 2666–2684
Freeman SA (1998) Development and use of capacity spectrum method. Proceedings of the 6th US National conference on earthquake engineering, Seattle, Oakland, USA
Freeman SA, Nicoletti JP, Tyrell JV (1975) Evaluation of existing buildings for seismic risk—a case study of puget Sound naval shipyard, Bremerton, Washington. Proceedings of US National conference on earthquake engineering, Berkley, USA, pp 113–122
Hancock J, Watson-Lamprey J, Abrahamson NA, Bommer JJ, Markatis A, McCoy E, Mendis R (2006) An improved method of matching response spectra of recorded earthquake ground motion using wavelets. J Earthquake Eng 10(S1): 67–89
Mander JB, Priestley MJN, Park R (1988) Theoretical stress–strain model for confined concrete. ASCE J Struct Eng 114(8): 1804–1826
Martinez-Rueda JE, Elnashai AS (1997) Confined concrete model under cyclic load. Mater Struct 30(197): 139–147
Menegotto M, Pinto PE (1973) Method of analysis for cyclically loaded RC plane frames including changes in geometry and non-elastic behavior of elements under combined normal force and bending. Symposium on the resistance and ultimate deformability of structures anted on by well defined loads, International association for bridge and structural engineering, Zurich, Switzerland, 15–22
PEER (2009) Strong ground motion database, http://peer.berkeley.edu/nga/
Priestley MJN, Grant DN (2005) Viscous damping in seismic design and analysis. J Earthquake Eng 9(1): 229–255
SeismoSoft (2006) SeismoStruct—a computer program for static and dynamic nonlinear analysis of framed structures. Available online from URL: www.seismosoft.com
Stefano M, Pintucchi B (2010) Predicting torsion-induced lateral displacements for pushover analysis: influence of torsional system characteristics. Earthquake Eng Struct Dyn. doi:10.1002/eqe.1002
Vuran E, Bal ÝE, Crowley H, Pinho R (2008) Determination of equivalent SDOF characteristics of 3D dual structures. Proceedings of the 14th World conference on earthquake engineering, Beijing, China, paper no: S15–031
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Bhatt, C., Bento, R. Assessing the seismic response of existing RC buildings using the extended N2 method. Bull Earthquake Eng 9, 1183–1201 (2011). https://doi.org/10.1007/s10518-011-9252-8
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DOI: https://doi.org/10.1007/s10518-011-9252-8