The importance of accidental design eccentricity in seismic design of steel buildings with dual system under the effect of far- and near-fault ground motions

Document Type : Research Article


Sahand University of Technology


Seismic responses of buildings are amplified due to torsion. To account for the effects that cause torsion and are not considered in the design process of buildings, the seismic codes introduce “accidental design eccentricity (ADE)”. In this study, the adequacy of the Iranian Standard No. 2800 provisions about the design eccentricity was investigated. To this end, the 5-story torsionally-stiff and torsionally-flexible buildings with dual lateral load resisting system were studied. The mass eccentricity in plan-asymmetric buildings was assumed to be equal to 0.10b and 0.20b where b is the plan dimension. Nonlinear time history analyses were performed using far-field (FF), non-pulse (NP) and pulse-like (FD) near-field records for the models in two cases. In the first case, the effect of the ADE on the seismic demands of symmetric and asymmetric-plan buildings was investigated. Finally, to consider what happens when an actual accidental mass eccentricity (AME) is introduced in an already designed building, the mass center of the buildings was shifted by ±0.05b (b is the dimension of the building perpendicular to the earthquake direction) simultaneously in both directions and the buildings (with and without ADE) were analyzed for the earthquake sets described above. For the buildings investigated in this research, the results indicate that the provision related to the accidental design eccentricity has little influence (less than 10%) on the inelastic seismic responses for torsionally-stiff buildings and can be ignored. Also, the accidental mass eccentricity has more influence (maximum 38%) on the inelastic seismic responses of torsionally-flexible buildings but the accidental design eccentricity has less influence on the reduction of seismic responses. Therefore, it seems that the accidental design eccentricity needs to be modified for torsionally-flexible buildings.


Main Subjects

[1]A.K. Chopra, J.C. De la Llera, Accidental and natural torsion in earthquake response and design of buildings, in: Eleventh World Conference on Earthquake Engineering, Acapulco, Mexico, Acapulco, Mexico, 1996.
[2]D.J. DeBock, A.B. Liel, C.B. Haselton, J.D. Hooper, R.A. Henige, Importance of seismic design accidental torsion requirements for building collapse capacity, Earthquake Engineering & Structural Dynamics, -831 (2014) (6)43 850.
[3]S. Anagnostopoulos, M. Kyrkos, K. Stathopoulos, Earthquake induced torsion in buildings: critical review and state of the art, Earthquakes and Structures, (2)8 377-305 (2015).
[4]J.C. De La Llera, A. Chopra, Evaluation of code accidental torsion provisions using earthquake records from three nominally symmetric-plan buildings, Rep. No. UCB/ EERC1992) 9 ,92-).
[5]J.C. De la Llera, A.K. Chopra, Evaluation of code accidental-torsion provisions from building records, Journal of Structural Engineering, 616-597 (1994) (2)120.
[6]J.C. De la Llera, A.K. Chopra, Accidental torsion in buildings due to stiffness uncertainty, Earthquake Engineering and Structural Dynamics, -117 (1994) (2)23 136.
[7]J.C. De la Llera, A.K. Chopra, Using accidental eccentricity in code‐specified static and dynamic analyses of buildings, Earthquake Engineering and Structural Dynamics, (9)23 967-947 (1994).
[8]J.C. De la Llera, A.K. Chopra, Accidental torsion in buildings due to base rotational excitation, Earthquake Engineering and Structural Dynamics, -1003 (1994) (9)23 .1201
[9]P. Fajfar, D. Marušić, I. Peruš, Torsional effects in the pushover-based seismic analysis of buildings, Journal of Earthquake Engineering, 854-831 (2005) (06)9.
[10]A.K. Chopra, R.K. Goel, A modal pushover analysis procedure to estimate seismic demands for unsymmetricplan buildings, Earthquake engineering & structural dynamics, 927-903 (2004) (8)33.
[11]A. Chandler, J. Correnza, G. Hutchinson, Influence of accidental eccentricity on inelastic seismic torsional effects in buildings, Engineering Structures, (1995) (3)17 178-167.
[12]S.L. Dimova, I. Alashki, Seismic design of symmetric structures for accidental torsion, Bulletin of Earthquake Engineering, 320-303 (2003) (2)1.
[13]J. De-la-Colina, C. Almeida, Probabilistic study on accidental torsion of low-rise buildings, Earthquake Spectra, 41-25 (2004) (1)20.
[14]O. Ramadan, S. Mehanny, A. Mostafa, Revisiting the %5 accidental eccentricity provision in seismic design codes for multi-story buildings, in:  14th World Conference on Earthquake Engineering, Beijing, China, 2008.
[15]K.G. Stathopoulos, S.A. Anagnostopoulos, Accidental design eccentricity: Is it important for the inelastic response of buildings to strong earthquakes?, Soil Dynamics and Earthquake Engineering, 797-782 (2010) (9)30.
[16]J. De-la-Colina, B. Benítez, S.E. Ruiz, Accidental eccentricity of story shear for low-rise office buildings, Journal of Structural Engineering, 520-513 (2010) (4)137.
[17]ASCE, Minimum Design Loads for Buildings and Other Structures, Standard ASCE/SEI 10–7, in, ASCE Reston, VA, 2010.
[18]S. Anagnostopoulos, M. Kyrkos, A. Papalymperi, E. Plevri, Should accidental eccentricity be eliminated from Eurocode 8?, Earthquakes and Structures, (2015) (2)8 484-463.
[19]J. De-la-Colina, C.A. González-Pérez, J. Valdés-González, Accidental eccentricities, frame shear forces and ductility demands of buildings with uncertainties of stiffness and live load, Engineering Structures, 127-113 (2016) 124.
[20]J.-L. Lin, W.-C. Wang, K.-C. Tsai, Suitability of using the torsional amplification factor to amplify accidental torsion, Engineering Structures, 17-1 (2016) 127.
[21]Standard No. 15-2800. Iranian code of practice for seismic resistant design of buildings. Fourth ed. Iran: Building & Housing Research Center,  (2015).
[22]V. Gioncu, F. Mazzolani, Earthquake Engineering for Structural Design, CRC Press, 2011.
[23]J.D. Bray, A. Rodriguez-Marek, Characterization of forward-directivity ground motions in the near-fault region, Soil Dynamics and Earthquake Engineering, 828-815 (2004) (11)24.
[24]P.G. Somerville, N.F. Smith, R.W. Graves, N.A. Abrahamson, Modification of empirical strong ground motion attenuation relations to include the amplitude and duration effects of rupture directivity, Seismological Research Letters, 222-199 (1997) (1)68.
[25]E. Kalkan, S.K. Kunnath, Effects of fling step and forward directivity on seismic response of buildings, Earthquake Spectra, 390-367 (2006) (2)22.
[26]M. Poursha, F. Khoshnoudian, A. Moghadam, A consecutive modal pushover procedure for nonlinear static analysis of oneway unsymmetric-plan tall building structures, Engineering Structures, 2434-2417 (2011) (9)33.
[27]Specification for Structural Steel Buildings (ANSI/AISC 10-360), American Institute of Steel Construction, Chicago-Illinois,  (2010).
[28]SAP2000, Computers and structures Inc, Berkeley, CA, USA,  (2016).
[29]Peer ground motion database, Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, http://ngawest2. berkeley. edu,  (2017).
[30]Baker Research Group, https://web.stanford. edu/~bakerjw/pulse-classification_old.html,  (2016).
[31]J.W. Baker, Identification of near-fault velocity pulses and prediction of resulting response spectra, in:  Geotechnical Earthquake Engineering and Soil Dynamics IV, 2008, pp. 10-1.
[32]ASCE, Sseismic Evalution and Retrofit of Existing Buildings, Standard ASCE/SEI 13–41, in, ASCE Reston, VA, 2013.
[33]O. Pekau, R. Guimond, Accidental torsion in yielding symmetric structures, Engineering Structures, (2)12 (1990) 89-501