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Frontiers of Structural and Civil Engineering

Front. Struct. Civ. Eng.    2018, Vol. 12 Issue (3) : 270-290
Confined masonry as practical seismic construction alternative–the experience from the 2014 Cephalonia Earthquake
Fillitsa KARANTONI1(), Stavroula PANTAZOPOULOU2, Athanasios GANAS3
1. Department of Civil Engineering, University of Patras, Rio?Achaia 26504, Greece
2. The Lassonde Faculty of Engineering, Deptartment of Civil Engineering, York University, Toronto M3J 1P3, Canada
3. Institute of Geodynamics, National Observatory of Athens, Athens, Greece
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During August 1953 three strong earthquakes of magnitude ranging from 6.3 to 7.2 shook the Ionian Island of Cephalonia (Kefalonia), Greece, and destroyed almost the entire building stock of the Island which consisted primarily of traditional unreinforced masonry (URM) houses. The authorities went on to restructuring of the building stock, using a structural system that is most like what is known today as confined masonry. They designed about 14 types of one- to two-storey buildings providing the engineers with detailed construction plans. These buildings are known as “Arogi” buildings (Arogi in Greek meaning Aid). On the 24th of January and 3rd of February 2014, two earthquakes of magnitude 6.1 and 6.0 struck the island, causing significant soil damages, developing excessively high ground accelerations. Surprisingly, no damage was reported in the “Arogi” buildings. The seismic behavior of the buildings is examined by FEM linear analysis and it is compared to that of URM structures. Computed results illustrate that the displacements of identical URM buildings would be about twice the magnitudes observed in the corresponding “Arogi” ones, with the implication that the earthquake sequence of 2014 would have caused critical damage should the type of structure be of the URM type. Furthermore, it is illustrated that this low cost alternative method of construction is a very effective means of producing earthquake resilient structures, whereas further reduction of seismic displacement may be achieved in the order of 50% with commensurate effects on damage potential, when reinforced slabs are used to replace the timber roofs.

Keywords Cephalonia      confined masonry      comparative FEM analysis      unreinforced masonry      seismic damage     
Corresponding Authors: Fillitsa KARANTONI   
Online First Date: 13 April 2017    Issue Date: 22 May 2018
 Cite this article:   
Fillitsa KARANTONI,Stavroula PANTAZOPOULOU,Athanasios GANAS. Confined masonry as practical seismic construction alternative–the experience from the 2014 Cephalonia Earthquake[J]. Front. Struct. Civ. Eng., 2018, 12(3): 270-290.
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Athanasios GANAS
Fig.1  The Cephalonia Transform Fault (CTF) and the epicenters (yellow stars) of the main events of the seismic sequence of January – February 2014
Fig.2  Seismic damage due to the 2014 Cephalonia Eartquake, (a) and (b) recently constructed R.C. buildings with notable deficiencies non-conforming to the established code practices, (c) and (d) in URM buildings built prior to the big earthquake of 1953
Fig.3  The town of Argostoli, capital of Cephalonia, after the 12/8/1953 earthquake
Fig.4  Typical plans of two Arogi houses. (a) 70.63 m2; (b) 65.65 m2
Fig.5  An unfinished brick CM
Fig.6  Reinforcing detail in the pilasters
Fig.7  Vertical section of a wall of concrete units
Fig.8  Structural print with plan view of the buildings of concrete units masonry depicted in Fig. 4
Fig.9  A wall comprising concrete-block masonry. Note the arrangement of the lintel beam
Fig.10  In the entrance corner of the semi-complete house note the vertical reinforcement as well as the starter bars for lap splicing reinforcement of the second floor at the crest of the first floor perimeter beam
Fig.11  Structural print, plan view of buildings of Fig. 4 of clay brick masonry units
Fig.12  Two “Arogi Houses” - condition of both as was after the earthquake. (a) As built (b) with lateral extension to the left, through a URM addition
Fig.13  Extension in height with the addition of a reinforced concrete frame
building typesumber of storiesfloor typeroof typecase ID
(concrete block masonry)
1-timberCM-1T *
1-R.C. slabCM-1S
2R.C. slabtimberCM-2ST
R.C. slabCM-2SS
stone URM1-timberURM-1T
1-R.C. slabURM-1S
2R.C. slabtimberURM-2ST
R.C. slabURM-2SS
plain masonry1-timberPM-1T
Tab.1  Cases studied in parametric investigation
Fig.14  Acceleration response spectra of the strong ground motion recorded in the Chavriata Station on 03/02/2014 (in g)
Fig.15  Displacement response spectra (for 5% damping) of the strong ground motion recorded in the Chavriata Station on 03/02/2014 (in cm)
Fig.16  Idealized buildings studied parametrically and corresponding finite element discretization
Fig.17  The basis of the proposed failure criterion
buildingdeformed shapepeak displacementdpl/%dh/%
% reductionreductionreduction
URM-1T3.64 mm0.140.13
reference valuereference valuereference value
UMR-1S0.93 mm0.010.03
CM-1T1.3 mm0.040.07
CM-1S0.6 mm0.0040.03
PM-1T1.53 mm0.050.08
Tab.2  Distribution of displacement and drifts of 1-storey buildings for G + Ex + Ey
building IDoverstressed area
percent reduction
reference value
Tab.3  Wall areas where failure criteria is exceeded
building????deformed shapemax displacement /mmdpl/%dh/%
% reduction from reference% reduction from reference% reduction from reference
URM-2TT8.25 mm0.2850.18
ref. valueref. valueref. value
URM-2ST5.6 mm0.1560.15
URM-2SS3.54 mm0.0070.03
CM-2TT2.64 mm0.0660.06
CM-2ST2.09 mm0.0370.08
CM-2SS2.05 mm0.0030.05
PM-2TT3.21 mm0.080.08
Tab.4  Distribution of displacement and drift ratios of 2-storey buildings for G + Ex + Ey
IDoverstressed areaIDoverstressed area
Tab.5  Wall areas where failure criterion is exceeded in two-storey building models
Fig.42  Max displacement (a) and failure criteria values (b) for one-storey buildings under G + 0.3Q + Ex + Ey; (c) comparison of relative drift ratios
Fig.43  Max displacement (a) and failure criteria values (b) for two-storey buildings under G + 0.3Q + Ex + Ey; (c) comparison of relative drift ratios
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