The response of a two-storey RC school building in the town of Argostoli, Cephalonia Island, Greece, during the seismic sequence of January and February 2014, is examined. The structure was built following an older generation of seismic codes dating from the 1950s, which provide limited strength and ductility against lateral loads. Despite the severity of ground shaking and the two successive events, the building suffered relatively minor damage, like most of the RC buildings in the town. Following a short presentation of some basic seismological, structural and geotechnical aspects of the seismic sequence, the paper focuses on the seismic performance of the structure at hand. To this end, a series of detailed non-linear static and time-history dynamic analyses are reported, which highlight the interplay of soil, foundation and superstructure in modifying the seismic demand. It is demonstrated that SSI had an unexpectedly important (detrimental) role in the behaviour of the structure, increasing its natural period by about 25% and aggravating ductility demand in almost all columns, despite the moderately soft soil conditions (average VS = 180 m/s). The results shed light on the seismic performance of the building and help drawing conclusions on the engineering effects of the 2014 Cephalonia earthquake sequence.
The response of a two-storey RC school building in the town of Argostoli, Cephalonia Island, Greece, during the seismic sequence of January and February 2014, is examined. The structure was built following an older generation of seismic codes dating from the 1950s, which provide limited strength and ductility against lateral loads. Despite the severity of ground shaking, the building suffered relatively minor damage, like most of the RC buildings in the town. Following a short presentation of some basic seismological, structural and geotechnical aspects of the seismic sequence, the paper focuses on the seismic performance of the structure at hand. To this end, a series of detailed non-linear static and time-history dynamic analyses are reported, which highlight the interplay of soil, foundation and superstructure in modifying the seismic demand. It is demonstrated that SSI had an unexpectedly important (detrimental) role in the behaviour of the structure, by increasing its natural period by about 11-13% and aggravating ductility demand in almost all columns, despite the stiff soil conditions (Vs = 440 m/s). The results shed light on the seismic performance of the building and help drawing conclusions on the engineering effects of the 2014 Cephalonia earthquake sequence.
Christos Kostikas, Civil Eng.; Mary Dalakiouridou, Civil Eng.; Christos Giarlelis, Civil Eng.; Evlalia Lamprinou, Civil Eng.; OMETE SA Consulting Engineers, Athens, Greece. Contact: giarlelis@alumni.rice.eduA preliminary structural study indicated that the architectural concept (the need for small size columns on the perimeter (Fig. 2) to permit a clear view of the egg-shaped interior shell and the presence of marble facades) could not be met with the high-performance seismic specifications that were set by the owner, considerably higher than those required by the Greek seismic code. 1 In addition, the protection of the contents of the building (i.e. artefacts, recording equipment, etc.) from induced seismic accelerations could not be ensured. Thus the incorporation of a seismic isolation system of friction pendulum AbstractThe Onassis House of Letters and Arts is a reinforced concrete (R/C) structure having a unique shape and dynamic behaviour. The main feature of the building is an egg-shaped shell structure, hosting a large auditorium, with slender columns along its perimeter. In order for the structural design to meet the high performance seismic specifications that were set, seismic isolation was deemed necessary. Friction pendulum (FPS) type isolators were selected and placed under the ground floor slab, for reasons of reduced cost and construction effectiveness. Dynamic response spectrum analyses as well as non-linear time history analyses using selected earthquake records were performed on a three-dimensional (3D) model of the structure shedding light on the seismic behaviour of the building. However, applying seismic isolation results in problems regarding the significant concentrated compressive forces from the isolators and in construction difficulties such as the potential replacement of isolators and the design of construction joints that ensure the free movement of the building despite the existence of ramps, elevators and staircases that pass through the level of seismic isolation. In addition, special care was needed for the design of the ground floor slab and the eggshaped shell structure housing the auditorium.
<p>The 2014 earthquake sequence in Cephalonia, Greece, resulted in a number of structural failures. In Argostoli, the capital of the island, a school building suffered light damage; however, the structural assessment following the analysis procedures of the recently published Greek Code for Structural Interventions, showed that seismic strengthening is required. The structure was built on the aftermath of the catastrophic 1953 Ionian earthquake sequence based on older code requirements, which are much outdated, as indicated from the results of both modal response spectrum analyses and non-linear static analyses. The retrofit aims to increase the very low structural capacity of the building and as a means for that the use of concrete jackets is selected. Based on the results of the assessment, it was decided that concrete jackets should be applied to all columns, while large structural walls running along the transversal direction were strengthened with single-sided reinforced concrete jacketing. The interventions are limited by architectural demands and cost considerations. However, analyses of the strengthened structure show that the interventions improve its seismic behaviour adequately. The detailing of interventions is thoroughly presented. What makes this case study interesting is the unusual structural system of the building, which is an ingenious combination of frame elements and lightly reinforced concrete walls and its behaviour to one of the strongest recent Greek earthquakes. The rehabilitation study had to model correctly the structure and propose interventions that were in agreement with the architectural demands and the cost consideration.</p>
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