doi:10.1016/j.engstruct.2005.02.002
Copyright © 2005 Elsevier Ltd All rights reserved.
Re-examination of damage distribution in Adapazarı: Geotechnical considerations
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B. Sadık Bakır, M. Tolga Yılmaz, Ahmet Yakut and Polat Gülkan
, 
Department of Civil Engineering, Middle East Technical University, ODTU 06531 Ankara, Turkey
Received 1 March 2004;
revised 29 January 2005;
accepted 2 February 2005.
Available online 10 March 2005.
Abstract
The role of ground conditions in damage distribution patterns of buildings in the city of Adapazarı during the 17 August 1999 İzmit (Kocaeli) earthquake 
is investigated. Damage was concentrated in the central districts of the city over the alluvial basin where four- to seven-story reinforced concrete buildings were most adversely affected. Two distinct and mutually exclusive modes of building damage were observed on the alluvium: structural system failures due to strong ground shaking, and foundation bearing failures apparently associated with soft or liquefiable surface deposits. To estimate the variation of surface response during the earthquake, the sites were classified as either stiff or soft, based on the amplification and de-amplification characteristics determined through analysis of one-dimensional soil response models. The results are compiled to develop an idealized codification of site-specific spectra that is utilized to assess the variation of spectral accelerations associated with the earthquake throughout the city. The outcome is consistent not only with the general trends pertaining to the distribution of building damage in terms of collapse data and post-earthquake observations, but it also predicts the respective sites of occurrence of the two distinct damage modes successfully. Accordingly, it is concluded that the buildings over soft sites benefited from significant reductions in seismic demand owing to the strong nonlinear soil response, and escaped pancake-type collapse.
Keywords: Foundation failure; Kocaeli earthquake; Liquefaction; Nonlinear soil response; Site effects
Fig. 1. Main geological features of the Adapazarı environs.
Fig. 2. Central municipality districts of the city of Adapazarı and variation of depth to bedrock.
Fig. 3. Building damage in the form of structural system failures at stiff sites.
Fig. 4. Building damage in the form of foundation displacements at soft sites.
Fig. 5. Idealized site response model.
Fig. 6. Contours of amplification ratios obtained from the analytical model study for a harmonic wave of period 0.2 s and surface deposit thicknesses of (a) 5 m and (b) 10 m. Gray lines indicate the estimated range for Adapazarı soft surface deposits.
Fig. 7. Database relating shear wave velocity of surface deposits to SPT blow counts in Adapazarı.
Fig. 8. Variation of SPT blow counts with depth in silt–clay mixtures from different sites of observed foundation displacements.
Fig. 9. Deep borehole logs, idealized soil profile and variation of shear wave velocity.
Fig. 10. Set of plots used to construct site-specific spectra at stiff sites in Adapazarı.
Fig. 11. Sample spectra for soft and stiff sites (the outcrop spectrum is the smoothed response spectrum of Adapazarı record).
Fig. 12. Collapsed building statistics for buildings with four and more stories in Adapazarı on the basis of municipal districts compared to the variation of surface deposit characteristics in the upper 10 m of the profile.
Fig. 13. Variation of spectral acceleration corresponding to a 0.5 s period. Squares indicate locations of collapsed buildings and dark gray patches mark the soft sites.
Corresponding author. Tel.: +90 (312) 210 2446; fax: +90 (312) 210 1193.
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