Seismic performance evaluation of traditional timber Hımış frames: capacity spectrum method based assessment

Bulletin of Earthquake Engineering, Jun 2016

Timber constructions have been widely suggested to be seismically resistant based on post-disaster reconnaissance studies. This observation has, however, remained to a large extent anecdotal due to the lack of experimental work supporting it, especially for certain timber architectural forms, including traditional timber frame “hımış” structures. To fill this gap, the authors carried out an extensive full-scale testing scheme using frames of various geometrical configurations, tested under reverse-cyclic lateral loading with/without infill (brick and adobe) or cladding (bağdadi and şamdolma) (Aktas et al. in Earthq Spectra 30(4):1711–1732, 2014a, b). The tests concluded that hımış frames had high energy dissipation capabilities due mostly to nailed connections. Infill/cladding significantly helped improve stiffness and lateral load strength of the frames, and timber type did not seem to make a remarkable impact on the overall behaviour. The current paper, on the other hand, uses test data to calculate capacity/demand ratios based on capacity spectrum method and Eurocode 8 to elaborate more on the performance of “hımış” structures under seismic loading. The obtained results are discussed to draw important conclusions with regards to how frame geometry and infill/cladding techniques affect the overall performance.

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Seismic performance evaluation of traditional timber Hımış frames: capacity spectrum method based assessment

Bull Earthquake Eng Seismic performance evaluation of traditional timber Hımıs¸ frames: capacity spectrum method based assessment Yasemin Didem Aktas¸ 0 1 2 3 Ahmet Tu¨ rer 0 1 2 3 0 Present Address: Epicentre Research Group, Civil, Environmental and Geomatic Engineering, University College London (UCL) , Gower Street, London WC1E 6BT , UK 1 Restoration Program, Middle East Technical University (METU) , Dumlupınar Bulvarı, 06800 C ̧ ankaya, Ankara , Turkey 2 & Yasemin Didem Aktas ̧ 3 Civil Engineering Department, Middle East Technical University (METU) , Dumlupınar Bulvarı, 06800 C ̧ ankaya, Ankara , Turkey Timber constructions have been widely suggested to be seismically resistant based on post-disaster reconnaissance studies. This observation has, however, remained to a large extent anecdotal due to the lack of experimental work supporting it, especially for certain timber architectural forms, including traditional timber frame ''hımıs¸'' structures. To fill this gap, the authors carried out an extensive full-scale testing scheme using frames of various geometrical configurations, tested under reverse-cyclic lateral loading with/ without infill (brick and adobe) or cladding (bag˘ dadi and s¸amdolma) (Aktas et al. in Earthq Spectra 30(4):1711-1732, 2014a, b). The tests concluded that hımıs¸ frames had high energy dissipation capabilities due mostly to nailed connections. Infill/cladding significantly helped improve stiffness and lateral load strength of the frames, and timber type did not seem to make a remarkable impact on the overall behaviour. The current paper, on the other hand, uses test data to calculate capacity/demand ratios based on capacity spectrum method and Eurocode 8 to elaborate more on the performance of ''hımıs¸'' structures under seismic loading. The obtained results are discussed to draw important conclusions with regards to how frame geometry and infill/cladding techniques affect the overall performance. Timber frame; hımıs¸; Capacity spectrum method 1 Introduction Traditional hımıs¸ houses are composite structures, characterized by upper floors composed of a timber frame load-bearing system constructed on top of a masonry ground floor that may or may not be timber-strengthened. Despite slight differences in different regions, especially in terms of infill/cladding materials/types, the same form and design principles were generally applied over a vast geographic area, regardless of differences in climate, extending from the inner sections of Anatolia to the Balkans and Greece (Kuban 1995; Cerasi 1998; So¨ zen 2001). There are many post-disaster studies reporting a favourable seismic performance of timber frame ‘‘hımıs¸’’ houses (e.g. see Ambraseys et al. 1968 for 1967 Mudurnu Earthquake; Sahin Gu¨ c¸han 2007; Penzien and Hanson 1970 for 1970 Gediz Earthquake; Erdik et al. 1992 for 1992 Erzincan Earthquake; Gu¨ lhan and O¨ zy o¨r u¨k Gu¨ ney 2000; Tobriner 2000, and Langenbach 2007 for 1999 Du¨ zce Earthquake; Demirtas¸ et al. 2000 for 2000 Orta Earthquake). In those cases where ‘‘hımıs¸’’ houses were reported to have behaved poorly, the damage was often either triggered by the failure of masonry ground floor or initiated by non-structural masonry elements such as chimneys, or associated with lack of maintenance, material degradation, improper connections, and heavy roofs (e.g. see Erdik et al. 2002a, b; Koc¸yi g˘it et al. 2002 for 2002 C¸ ay Earthquake and Erdik et al. 2003 for 2003 Bingo¨ l Earthquake). Despite these post-disaster observations, the seismic resistance of ‘‘hımıs¸’’ houses has remained largely anecdotal due to the lack of experimental work supporting this conclusion. To provide this empirical baseline data, in 2010 a research project was set up and funded by the Scientific and Technological Research Council of Turkey (106M499). To this end, a number of frame tests and capacity/demand calculations were carried out with the aim of assessing and quantifying the seismic resistance of traditional timber hımıs¸ frames. The findings from these frame tests have been presented and discussed elsewhere (Aktas et al. 2014a, b). This paper reports the ATC-40 based capacity calculations using the data obtained from the frame tests and comparison of these against demand values Fig. 1 An overall view of the test setup calculated by using Eurocode 8 (2004), in order to evaluate the seismic performance of each frame with different geometrical configurations, with and without infill/cladding. 2 Frame tests For frame tests, a total of 6 frames that reflect the geometrical and constructive features of traditional hımıs¸ frames were selected from Safranbolu, a UNESCO World Heritage site in northern Turkey for its authentic townscape characterized by hımıs¸ houses (for more detailed information about frame selection, see Aktas et al. 2014a). Out of 6 selected frame geometries, 2 were built twice by local builders using yellow pine and fir (see Aktas et al. 2014a for material properti (...truncated)


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Yasemin Didem Aktaş, Ahmet Türer. Seismic performance evaluation of traditional timber Hımış frames: capacity spectrum method based assessment, Bulletin of Earthquake Engineering, 2016, pp. 3175-3194, Volume 14, Issue 11, DOI: 10.1007/s10518-016-9943-2