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ETAM Report on the Albania earthquake of November 26, 2019. Structural and Geotechnical Damage

Albania'Earthquake,'November'26,'2019'–'HAEE'Report'on'Structural'and'Geotechnical'Damage'
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in collaboration with the Earthquake Planning and Protection Organization of
Greece (EPPO OASP), the University Network of Seismic Engineering
Laboratories of Italy (ReLUIS) and the University of Bristol, UK
Albania earthquake of November 26, 2019
Report on Structural and Geotechnical Damage
Reconnaissance Team: Anastasios Sextos (President, HAEE-ETAM), Eftimios Lekkas
(President EPPO-OASP), Stefanidou Sotiria (HAEE-ETAM), Baltzopoulos Georgios, (RELUIS,
Italy), Fragkiadakis Michalis (HAEE-ETAM), Giarlelis Christos (HAEE-ETAM), Luca
Lombardi (University of Bristol), Markogiannaki Olga (HAEE-ETAM), Mavroulis Spyridon
(National and Kapodistrian University of Athens), Plaka Aristo, Pnevmatikos Nikolaos (HAEE-
ETAM), Skoulidou Despoina (HAEE-ETAM), Tsiatas George (HAEE-ETAM), Tsopelas Panos
(HAEE-ETAM).
November 2020
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Contents'
1. INTRODUCTION ............................................................................................................................................... 3
December 14th, 2019 (Day 1 - Saturday) ................................................................................................................ 3
December 15th, 2019 (Day 2 - Sunday) .................................................................................................................. 4
2. SEISMOLOGICAL DATA AND RECORDED GROUND MOTION .............................................................. 4
3. ALBANIAN SEISMIC CODE KTP-N.2-89 ....................................................................................................... 7
4. EUROPEAN UNION CIVIL PROTECTION ................................................................................................... 10
5. POST-QUAKE RAPID VISUAL INSPECTION (RVI) TOOL ....................................................................... 11
6. STRUCTURAL DAMAGE ............................................................................................................................... 12
6.1 Building performance in Durrës ...................................................................................................................... 13
6.1.1. Residential buildings ............................................................................................................................... 14
6.1.2. Hotels ....................................................................................................................................................... 24
6.2. Building performance in Thumanë ................................................................................................................. 25
6.2.1. Religious establishments ......................................................................................................................... 26
6.2.2. Residential buildings ............................................................................................................................... 28
6.3. Post-Quake Rapid Visual Inspection Aggregated Data .................................................................................. 37
7. GEOTECHNICAL DAMAGE .......................................................................................................................... 41
8. SUMMARY AND CONCLUSIONS .................................................................................................................... 44
References .................................................................................................................................................................. 45
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1. INTRODUCTION
On November 26th 2019, Northwestern Albania was struck by an Mw6.4 earthquake, resulting in
more than three thousand injuries, including fifty-one fatalities. The Hellenic Association of
Earthquake Engineering (HAEE/ETAM) in collaboration with the Earthquake Planning and
Protection Organization (EPPO/OASP), the University Network of Seismic Engineering
Laboratories of Italy (ReLUIS) and the University of Bristol (UoB), UK, organized a field mission
on the 14th and 15th of December 2019 to inspect structural and geotechnical damage in Durrës and
Thumanë. The scope of the mission was to collect data related to damage patterns and extent,
evaluate the seismic performance of structures providing preliminary conclusions and, potentially,
to transfer knowledge regarding the current code provisions for the design and retrofit of
earthquake-resistant structures.
The HAEE/EPPO/RELUIS/UoB team lead by Prof. A. Sextos, University of Bristol (HAEE
president) and Prof. E. Lekkas, National & Kapodistrian University of Athens (EPPO president),
consisted of 14 experienced Civil Engineers, Professors and Researchers from National Technical
University of Athens, National & Kapodistrian University of Athens, Aristotle University of
Thessaloniki, University of Patras, University of Naples Federico II, University of Bristol, University
of West Attica, University of Western Macedonia and the University of Porto as well as freelancers
and chartered civil engineers.
The agenda of the HAEE field mission in Albania is outlined below:
December 14th, 2019 (Day 1 - Saturday)
§ Meeting with the staff of the Greek Embassy and the Ambassador Mrs. Sofia Filippidou.
Description of the scope of the field mission. Discussion of potential actions related to
knowledge transfer of current European code provisions for seismic design (including
assessment and retrofit) to the local professional structural engineering community.
§ Meeting with the European Union Civil Protection coordinating committee, located at the
Prefecture building in Durrës, to be briefed on the progress of the post-earthquake
inspection program in the area, as well as the general planning and coordination of the
international inspection teams working on it.
§ Field Inspections/reconnaissance mission in the city of Durrës.
§ Participation in AACE (Albanian Association of Consulting Engineers) conference in
Tirana. Prof. Anastasios Sextos was invited as a panellist to comment on the current
European practice for the design and assessment of existing buildings.
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Figure 1: ETAM mission - Meeting with the Ambassador Mrs. Sofia Filippidou at the Greek Embassy
Figure 2: ETAM mission - Meeting with the EU Civil Protection coordinating committee (left), participation
in AACE (Albanian Association of Consulting Engineers) conference in Tirana (right)
December 15th, 2019 (Day 2 - Sunday)
§ Meeting with Archbishop Anastasios of Tirana, Durrës and all Albania, to be informed about
the extent of damage on religious establishments in the area.
§ Field Inspections/reconnaissance mission in Thumanë and Romano Port.
2. SEISMOLOGICAL DATA AND RECORDED GROUND MOTION
According to the USGS National Earthquake Information Center, the epicenter of the moment
magnitude Mw6.4 earthquake, was 16km southeast of Mamurras (long. 41.514°N, lat. 19.526°E;
Fig.1). The same source reports that the causal focal mechanism is related to reverse movement on
a NW-SE trending fault (USGS event page; last accessed 20/02/2020). The maximum macroseismic
intensity, estimated by the USGS based on instrumental data and witness reports, was VIII on the
Modified Mercalli intensity scale.
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Figure 3 : Shakemap for the Nov 26, 2019, M6.4 Albania earthquake (source:USGS; last accessed 20/02/2020)
Figure 4. Shakemaps in terms of Peak Ground Acceleration (left), Peak Spectral Acceleration at 0.3s (middle)
and Peak Spectral Acceleration at 1.0s (right); data retrieved from the INGV Shakemap archive (last accessed
18/02/2020).
The Italian Institute for Geophysics and Volcanology (INGV) shakemap service further provided
estimates of the spatial distribution of instrumental shaking intensity in terms of peak ground
acceleration (PGA) and 5% damped pseudo-spectral acceleration (PSA) at vibration periods of 0.3s
and 1.0s, all of which are shown in Figure 4.
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Four accelerometric recordings were obtained within an epicentral distance of 100 km or less (7
within 130km). The acceleration time history recorded closest to the epicenter was the one obtained
at the building of the Institute of GeoSciences, Energy, Water and Environment (IGEWE) in Tirana,
with a PGA of 0.114g. The PSA response spectra of the two as-recorded horizontal and vertical
components are shown in Figure 5.
From the figure it can be seen that the two horizontal components exhibit similar spectral
amplitudes, with a slight preponderance of the east-west component, and a PSA that peaks at 0.40g
at a period of 0.22s. The vertical component has lower spectral amplitudes than the horizontal ones,
which is not unexpected for ground motion not recorded near the fault. Epicenter locations for the
mainshock and aftershocks with M>4.0 recorded within twenty days of the mainshock, are depicted
in Figure 6. Until December 15, that the field mission took place, four aftershocks having M ≥ 5.0
were recorded and eighteen with magnitude between M4-M4.9. The largest aftershock occurred less
than four hours after the mainshock in the vicinity of Thumanë, having a magnitude of M5.4.
It is noted that the unique ground motion recorded in Durrës is not complete due to electricity
supply disruption. Processing and interpretation of the recording shows a horizontal PGA of 0.192g
(N-S component), 0.122 (E-W component) and 0.114g (Z component) which is in good agreement
with the average predicted value by a regional Ground Motion Prediction Equation (Duni &
Theodoulidis, 2019). The same study also highlights the rich frequency content of the recorded
motion with spectral acceleration at least 0.50g, along a wide range of periods between 0.3sec and
1.0sec, that is the result of the soft soil formations at the location of the recording station DURR
characterized by an average shear wave velocity of the uppermost soil layers of Vs=200m/sec (Duni,
2013).
Figure 5. Pseudo-acceleration response spectra of the TIR1 station record’s horizontal and vertical
components. (epicentral distance 28.7 km, corrected acceleration time series obtained from the Engineering
Strong Motion database, left). Pseudo-acceleration response spectra (for 2%, 5%, 10% and 20% damping) of
the first 15sec of the acceleration time history recorded at the DURR station (Duni & Theodoulidis, 2019).
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Figure 6. Location of epicentre and aftershocks within the first twenty days after the mainshock.
(source:https://en.wikipedia.org/wiki/2019_Albania_earthquake#/media/File:Aftershock_locations_Alba
nia_2019.png)
An insight on the co-seismic ground deformation induced by the 26th November 2019 earthquake
can also be found (Markogiannaki et al., 2020) combining SAR interferometry using Sentinel-1
images and open geospatial information to develop deformation maps of the affected area including
local exposure data.
3. ALBANIAN SEISMIC CODE KTP-N.2-89
In order to evaluate the seismic performance of buildings in Durrës and Thumanë based on the
observed damage modes and intensity, the provisions of the Albanian seismic code for the design
of structures are presented herein along with the relevant of Eurocode 8 clauses for comparison.
The details presented are based on recent literature (Frangu & Bilgin, 2014; Kokona et al., 2016).
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Provisions for the design of earthquake resistant structures were incorporated in Albanian codes
nearly five decades ago. The first version of Albanian code started as a legal provision (KTP – 63)
in 1963. In 1970, the countries of the region (except for Albania) worked on projects REM/70/172
and REM/74/09 under the auspices of UNDP and UNESCO, providing a survey of seismicity for
the region. Soon, the Albanian code was amended in 1978 (KTP-78), following the most recent
revision implemented in 1989, that formed the KTP-89, or KTP-N.2-89 (Seismic Center, Academy
of Science of Albania. Department of Design, 1989), which is the current code. According to this
code, the spectral acceleration is defined as follows:
𝑆!= 𝑘"𝑘#𝜓𝛽$𝑔
(1)
where kE is the seismic coefficient, kr a building importance coefficient (typically equal to 1 for
standard structures), ψ a structural coefficient (given in Table 4 of KTP-89) and g is the gravitational
constant. The dynamic coefficient βi is defined as:
0.65 ≤ 𝛽$=%.'
(
!
≤ 2.3
for soil category I (2.1)
0.65 ≤ 𝛽$=%.)
(
!
≤ 2.0
for soil category II (2.2)
0.65 ≤ 𝛽$=*.*
(
!
≤ 1.7
for soil category III (2.3)
Seismic coefficient KE is listed in Table 1 as a function of soil types I, II, III that roughly correspond
to Eurocode 8 (CEN, 2004) soil classes A, B and C, respectively (Frangu & Bilgin, 2014). There is
no soil amplification factor as in recent versions of Eurocode 8. The division of seismic zones in
Albania is made by means of the intensity seismic scale MSK-64 (as also shown in Table 1), while a
probabilistic seismic hazard map for the country with 475 years return period is illustrated in Figure
7.
Soil category
Seismic coefficient kE
Intensity VII
Intensity VIII
Intensity IX
I
0.08
0.16
0.27
II
0.11
0.22
0.36
III
0.14
0.26
0.42
Table 1. Seismic coefficient according to KTP-N.2-89 (Seismic Center, Academy of Science of Albania.
Department of Design, 1989).
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Figure 7. Probabilistic seismic hazard map of Albania with 475 years return period, expressed in PGA on
rock soil (Fundo et al., 2012) (left) and map of Albania (Apple maps, right).
Comparison between the Eurocode 8 and the KTP-89 design spectrum is presented in Figure 8
(Kokona et al., 2016) indicatively for soil type B, PGA=0.32g, importance factor 1.0 and behavior
factor q=3.0. From Figures 7 and 8, it is seen that the design accelerations prescribed by the current
Albanian code are lower compared to the respective ΕC8 ones. Moreover, the horizontal PGA of
0.192g recorded (on soft soil, Figure 5) in Durrës is also estimated to be lower than that derived by
means of PSHA for the same area (given the value of 0.24g predicted on rock with the free field one
assumed to be typically higher, Figure 7). The above observations imply that the buildings in the
region have been designed for lower base shear compared to Eurocode 8, but on the other hand,
the ground motion acceleration itself was also less intense compared to the corresponding one
predicted with 10% probability to be exceeded in 50 years.
Figure 7. Design response spectrum according to KTP-89 & EC8 (Kokona et al., 2016).
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4. EUROPEAN UNION CIVIL PROTECTION
At the time of the visit, the European Union Civil Protection Team had already been working in
Albania for more than a month, organizing field missions for visual inspections mainly in Durrës
and Thumanë, involving a large number of civil engineers working in groups (of the order of 100 at
the peak of their activities). The HAEE/EPPO/RELUIS/UoB team visited the European Union
Civil Protection office, located at the Prefecture Building in Durrës, and was informed of the building
damage recorded in Durrës, Thumanë, Lezhë, Krujë and other regions that were affected by the
earthquake (Figure 8). Until December 14th, approximately 2,000 visual building inspections had
been completed. The most severe damage was recorded in Durrës and Thumanë. Based on the
recommendations of the European Union Civil Protection Team, the HAEE/EPPO/
RELUIS/UoB team organized two daily field missions in Durrës and Thumanë in order to gather
data and photos related to structural and geotechnical damage, perform Rapid Visual Inspections
(RVI) for the evaluation of damage and make proposals to the Albanian authorities about recovery
plans and retrofit prioritization.
Figure 8. Premises of the European Union Civil Protection Team, Prefecture Building, Durrës.
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5. POST-QUAKE RAPID VISUAL INSPECTION (RVI) TOOL
Many methodologies are available for pre- and post-earthquake rapid visual inspection of structures,
while the most popular and widely used is the FEMA method for Rapid Visual Screening (RVS) or
Rapid Visual Inspection (RVI) of Buildings (FEMA P-154 (2015), FEMA 356, (2000)). The NZSEE
(New Zealand National Society for Earthquake Engineering), JBDPA (Japan Building Disaster
Prevention Association, 1990) and the GNTD (Gruppo Nationale Per La Difesa Dai Terremoti,
1993) are also widely applied methodologies for Rapid Visual Screening. The RVI procedure
prescribed by FEMA uses a methodology based on the building survey inspection and requires the
filling of a data collection form based on visual observation of the building from the exterior, and if
possible, the interior. The two-page data collection form includes building identification information
(i.e. usage, area, floor number, etc.), a photograph of the building, sketches, and documentation of
pertinent data related to seismic performance. Based on the data collected during the survey, a score
is calculated that provides an indication of the expected seismic performance of the building.
Figure 10. Post-Quake RVI (Safer) mobile app.
Simple survey procedures for seismic risk assessment are proposed and applied to urban building
stocks to provide damage statistics (Sucuoglu & Yazgan, 2003). In order to perform Post-Quake
RVI, store the relative information in an online database, the use of a tool for rapid visual survey
was necessary. The HAEE/EPPO/RELUIS/UoB team, consisting of experienced and qualified
civil engineers, used the Post-Quake RVI (SAFER) app
1
(Figure 10), a tool developed by the
1
https://play.google.com/store/apps/details?id=uk.ac.bristol.rit.safer2&hl=el
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University of Bristol following its first pilot application during the 2016 central Italy earthquake
(Sextos et al., 2018; Stewart et al., 2018). For every building inspected, the app retrieves the GPS
location (Sextos et al., 2008), while the user stores (and the app wirelessly transmits) external and
internal photos and general building information affecting its seismic performance (structural
system, extent of damage, number of storeys, soil conditions, etc.). Furthermore, information related
to the type of damage (i.e. beam flexural or shear damage, panel out-of-plane cracking, etc) is also
collected for every building. The data of all buildings inspected is then saved and uploaded to a
central data server, that is accessible through a dedicated WebApp (more in Section 7).
6. STRUCTURAL DAMAGE
According to the European Union Civil Protection, the most severe structural damage was observed
along the coastline around the large port city of Durrës and the village of Kodër-Thumanë, which
was near to the epicentre of the earthquake. For this reason, the HAEE/EPPO/RELUIS/UoB team
efforts focused on the city of Durrës and the village of Thumanë. In all cases, the RVI was performed
for selected buildings using the Post-Quake RVI (SAFER) application described above. The
buildings were mainly inspected from the exterior and, in some cases, from the interior as well.
Statistics of damaged buildings in Durrës and Thumanë are presented in the following, along with
damage classification and preliminary conclusions based on field observations. The damage extent
was classified as light, moderate, severe (major) and collapse in accordance to the four pre-
earthquake performance objectives defined in FEMA 356 against which the post-earthquake damage
description is classified (Table 2). It should be noted that in Albania the majority of the existing
buildings, were designed to resist only vertical loads until the implementation of the seismic code of
1989 (Bilgin & Korini, 2013), which unavoidably contributed to the poor seismic performance of a
number of structures considering the earthquake magnitude and ground motion intensity of the
November 26th event. Given that a number of parameters such as, the structural system and materials
used, construction age, building height (number of storeys), the existence of irregularities in plan and
elevation, construction stages, soil type, etc. strongly affect the structural performance, they were
also collected as part of structural performance assessment. However, for the majority of cases where
architectural and design drawings were not available, or for cases that it was impossible to inspect
the interior of buildings and identify the structural configuration on site, this report does not make
any explicit (i.e., building specific) interpretation of the damage mechanisms.
Table 2. Qualitative description of damage states according to FEAM 356 (American Society of Civil
Engineers (ASCE), 2000) and association with observed post-earthquake damage states.
Target Building
Performance Levels
Post-earthquake
Damage
Immediate Occupancy
Level (1-B)
Light
Life Safety Level (3-
C)
Moderate
Collapse Prevention
Level (5-E)
Severe (major)
Collapse
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6.1 Building performance in Durrës
The majority of buildings in Durrës are reinforced concrete buildings of 4-10 storeys. i.e., mid- to
high-rise for the Albanian standards, constructed after 1990. The use of precast panels and masonry
is also common. Regarding masonry building typologies, it is noted that unreinforced masonry
buildings (URM), and in particular confined masonry, had been widely used before the 1980’s, while
confined reinforced masonry buildings were introduced later (Kokona & Kokona, 2015)). When the
KTP-89 was established it included specific provisions for the latter under the description of a
‘complex system’. Based on the data presented at the AACE (Albanian Association of Consulting
Engineers) conference in Tirana on 14/12/2019 (Table 3 (Novikova et al., 2015)), the buildings that
were built after 1990 are more than 40% of the total building stock. This figure is even higher in the
capital where, as anticipated, newer construction is more extensive. Overall, they both reflect the
trends of urbanization and internal migration of the population towards the capital and the coastal
areas of the country (INSTAT, 2016; Novikova et al., 2015).
Table 3. Number of buildings per time of construction and seismic code in Durrës
City
Time of construction
Before
1945
1945-
1960
1961-
1980
1981-
1990
1991-
1995
1996+
Total
Durrës (population 113,000)
1,778
3,485
7,016
5,188
4,312
8,417
30,196
Without seismic code
57.8%
With seismic code
42.2%
Table 4. Number of buildings per time of construction and seismic code in Tirana
City
Time of construction
Before
1945
1945-
1960
1961-
1980
1981-
1990
1991-
1995
1996+
Total
Tirana (population 418,000)
5713
5905
11,698
10,585
11,406
21,231
66,538
Without seismic code
50.9%
With seismic code
49.1%
Figure 11. Distribution of housing units of buildings, year of construction and municipality (Republic of
Albania et al., 2020).
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Figure 12. Distribution of damaged housing units per year of construction (Republic of Albania et al., 2020).
Figure 12 presents the percentage of buildings that have experienced a degree of damage in 10
different municipalities in Albania classified per year of construction, with the threshold being in
1993 (Republic of Albania et al., 2020). It is shown that the extent of damage was twice as high (29%
for pre-1993 versus 14% for post-1993) for the entire building stock. The same analogy holds for
Durrës, where 42% of the pre-1993 buildings and 24% of the post-1993 buildings were damaged.
Overall, the most common damage pattern observed was the out-of-plane failure of infill walls, both
external and internal, followed by in-plane diagonal (‘X’-shaped) cracking due to diagonal tension,
concrete spalling, hoop fracture, buckling of longitudinal reinforcement, concrete core crushing and
shear cracking of short columns. At the time of the visit the debris of the collapsed buildings had
been removed, while most of the buildings at the onset of collapse had already been demolished. As
a result, it was not possible to know if the collapse was total or partial, or to evaluate the failure
mechanism.
6.1.1. Residential buildings
Structural damage patterns, classified as slight, moderate, severe (major) and collapse are depicted in
Figures 13 to 22 characterizing the seismic performance of buildings in Durrës. An example of light
damage is the multistorey RC building that performed well during the earthquake (Fig.13), with only
slight horizontal and diagonal cracking at external infill panels observed. Multistorey RC buildings
that performed rather well during the earthquake (Fig.15,16). Figures 14-15 illustrate cases of
moderate damage including diagonal cracks at non-structural elements along with flexural cracks at
columns. Figure 16 shows an example of a multistorey RC building with poor seismic performance
and major damage due to the earthquake, including extensive in-plane and out-of-plane failure of
masonry infill panels. The latter is a widespread building practice in southern Europe and usually
consist of perforated clay bricks. Their interaction with the encasing RC frame is typically neglected
during seismic design calculations and also by the codes as it is perceived as a secondary horizontal
load bearing system. When the panels are well-connected to the surrounding frame and are arranged
in a regular pattern that does not create stiffness discontinuities, the contribution of the infills can
enhance the seismic response of the RC building, a fact that has been long and well-documented in
the literature (Dolšek & Fajfar, 2008; Panagiotakos & Fardis, 1996; Ricci et al., 2013; Zarnic &
Tomazevic, 1985). On the other hand, poor connection with the frame can lead to premature out-
of-plane failure of the infills, at it was observed in several cases in Durrës.
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Figure 13. Light damage of an 8-storey RC building
Figure 14. Moderate damage of a 5-storey RC building
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Figure 15. Moderate damage of a 7-storey RC building
Figure 16: Major damage of an 8-storey RC building
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As seen in Figure 16, masonry infills of the perimeter frames were inadequately confined by the
surrounding frames due the lack of columns at the ends, which is in itself a rather unfortunate design
choice. As the infill walls tend to follow the inter-storey drifts experienced by the surrounding frame
during the earthquake-induced ground motion, they experience shear diagonal cracks; the absence
of vertical RC elements at the edges providing some confining contact pressure to the deformed
panel, makes the masonry panel extremely susceptible to out-of-plane collapse, due to the inertial
forces caused by the component of floor response perpendicular to the infill’s plane (Morandi et al.,
2014). This type of damage is concentrated to the lower floors of the building, which is anticipated,
since RC frames tend to exhibit a shear-type lateral deformation pattern, with greater concentration
of inter-storey drifts closer to the ground floor.
Another issue with masonry infills is the irregularity of lateral stiffness along the height of an RC
frame, caused by interruption of the infills at the ground floor. This practice is often dictated by
commercial use of the building at ground level and can lead to a concentration of flexural
deformations at the ground floor columns (Ricci et al., 2011). Evidence of this effect can be seen in
Figure 17.
Figure 17: Major damage of 4-storey RC building
In fact, flexural and shear cracks are visible at the external ground floor columns, which can be
attributed to the aforementioned effect of stiffness irregularity-in-height. The out-of-plane buckling
of a segmented metal-sheet garage door, also attests to the concentration of drift at the ground floor.
Furthermore, the spalling of concrete cover, visible at the base of one of the columns, reveals poor
detailing of transverse reinforcement; the 20 cm spacing of the stirrups is not up to par with modern
seismic code ductility requirements for confinement reinforcement in columns. It should also be
noted, that the adjacent building suffered collapse and had already been demolished by the time
these pictures were taken; in this light, some of the damage that can be observed the outer-most
non-structural elements could have been due to pounding between the two buildings during strong
ground motion.
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Figure 18: Major damage of 5-storey building.
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Another interesting and typical structural typology that suffered extensive damage is that of
unreinforced brick masonry buildings with RC slabs (Fig. 18). This typology can be characterized as
a template design building, which were used for building development by the Albanian authorities
until the end of the communist period in 1990 and nowadays are mainly used as residential buildings
(Bilgin & Korini, 2012).
This structural system follows the concept of similar building types developed in Italy and in other
areas in the world between 1920’s-1930’s called “modern” masonry buildings (MMB) (Sandoli &
Calderoni, 2018) with the introduction of reinforced concrete elements (especially for the floors) to
reduce the seismic vulnerability of buildings (Calderoni et al., 2020). The masonry material was
perforated clay blocks. Flexural and shear cracks at structural and non-structural elements were
observed externally, mainly around openings. In particular, “X”-shaped cracks due to diagonal
tension were observed at both external and internal infill walls, while wider cracks and detachments
were also apparent. Severe damage of internal walls (clay bricks) was observed; out-of-plane wall
failure and partial collapse. There were also significant out-of-plane displacements of corner walls
due to very large diagonal cracking near the building corners. This mechanism has been also observed
in private residential masonry buildings in Italy after strong earthquake events such as that of
L’Aquila (Calderoni et al., 2020) and can be probably attributed to the decompression of portions of
corner walls after cracking, that is, not necessarily due to overturning phenomena of the external
facades. The observed damage could also have been developed due to insufficient interlocking
between intersecting walls and lack of anchorage between wall and concrete floor slabs along with
low-quality masonry materials and mortar, as it is noted also on a work on the performance of
masonry buildings in Albania (Kokona & Kokona, 2015).
Figure 19 offers another example of a multistorey RC building exhibiting major seismic damage,
where the two defects highlighted above are both present: masonry infill panels not adequately
aligned with the perimeter frames and interruption of the infills at the ground floor. In fact, these
issues are a recurrent theme also in the following cases examined. In this case too, out-of-plane
failure of infill walls was observed in several location around the perimeter. The partial collapse of
extruded volumes of unreinforced masonry, provided for aesthetic and architectural reasons, is also
visible. This can be attributed to lack of adequate connection to the load-bearing RC frame between
floors, as stability was apparently relying exclusively on small portions of the floor slab cantilevering
out to accommodate the masonry elements.
Another multistorey RC building with major damage due to the earthquake is illustrated in Figure
20. Flexural cracks and out-of-plane failure of infill walls, partial collapse of infill walls and facades,
wide cracks and detachments, were observed. Significant damage was observed at the interior of the
building, with wide flexural and shear cracks, mainly at infill walls and “X”-shaped cracks at infill
walls around the staircase location. The absence of a RC core at the staircase and the elevator should
be commented, along with the severe damage of the staircase. Similar structural pathology is depicted
in Figure 21.
As already stated, at the time of the reconnaissance mission, the debris of the collapsed buildings
had been removed and partially collapsed structures had been demolished. Therefore, it was not
possible to evaluate their failure mechanism (Fig. 22). It is noted that the sites of the (fully or partially)
collapsed buildings were cleaned in very short time after the earthquake event.
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Figure 19: Major damage of a 5-storey RC building. No confinement of the brick masonry walls to the RC
frame is observed.
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Figure 19 (continued)
Figure 20: Major damage of a 6-storey RC building
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Figure 20: Major damage of a 6-storey RC building (continued).
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Figure 21: Major damage of a 10-storey RC building.
Figure 22: Collapsed and/or demolished buildings.
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6.1.2. Hotels
Severe damage was observed at several hotels in Durrës. Hotel Ljubljana, Hotel MiraMare and Hotel
Villa Verde are some examples. As with the residential buildings, at the time of the visit the debris
of the collapsed buildings had been removed (Figure 23). Light damage was observed at several
hotels in the close proximity of the collapsed hotels. Flexural and shear cracks were observed, mainly
at infill walls, as depicted in Fig. 24.
Figure 23: Vila Verde Hotel (left) and Lubjana Hotel (right).
Figure 24: Photos at the location MiraMare Hotel.
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Figure 25: Light damage at hotels in Durrës
6.2. Building performance in Thumanë
Most buildings in Thumanë are single or two-storey (rarely three-storey) buildings built after 1950
until recently. Regarding the structural system, the most popular is RC frames with infills and
masonry with timber roofs. In most cases the buildings were constructed by the owners themselves,
therefore, without necessarily following structural design code prescriptions. Unreinforced masonry
buildings (URM) are also common. It is noted that many buildings were constructed in stages using
different materials and structural systems, being extended in plan and/or elevation years after their
initial construction, using RC frames and infill walls.
The most common damage patterns observed were the in-plane diagonal (‘X’-shaped) cracking and
out-of-plane failure of infill or masonry walls, both external and internal. Other damage patterns
observed were concrete spalling, hoop fracture, buckling of longitudinal reinforcement and concrete
core crushing and shear cracking. Unreinforced masonry buildings (low-middle rise) presented
extended damages, as it is very common during strong earthquakes due to poor quality of
construction, poor workmanship, aging and the lack of maintenance.
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6.2.1. Religious establishments
Slight to moderate damage was observed at the mosque of Thumanë (Fig. 26-27). The structural
system of the mosque is mainly masonry with RC frames at the interior. The horizontal and vertical
joints are irregular (in terms of shape and thickness), while the mortar thickness varies. Wide “X”-
shaped cracks due to diagonal tension were observed at the exterior infill walls together with cover
spalling at the interior. Small cracks were also observed at the dome as well as along the dome ring
due to excessive horizontal stresses. No significant damage was observed on the interior RC frame
elements. This is the result of their small stiffness compared to the stiffness of the masonry walls at
the perimeter of the structure that provided the main seismic resistance. The minaret appears to have
suffered moderate damage. Minarets in general exhibit seismic behavior not similar to other known
structures, because of their unique characteristics in terms of slenderness and shape. The minaret
has a hexagonal cross-section and it is constructed with RC columns of approximately 10x10 cm2 at
every vertice of the hexagon and tie-beams every 3m along its height. Extended cracking and spalling
were observed, at the base and along the shaft. Cracks are also present at the connection of the
minaret to the main mosque structure. These cracks are very common when minarets are contiguous
and integral with the main mosque structure. They come as result of the out-of-phase vibration of
the two parts of the structure due to the difference of their dynamic properties.
Figure 26: Damage of the mosque in Thumanë
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Figure 27: Damage of the mosque in Thumanë
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6.2.2. Residential buildings
Most buildings in Thumanë developed moderate to major damage, if they did not collapse either
partially or totally. An example of light-to-moderate damage is the single-storey masonry building
with clay bricks shown in Figure 28. “X”-shaped, wide cracks due to diagonal tension at masonry
walls were observed, along with cracking and spalling at the base of slender vertical load bearing
elements. The in-plane diagonal cracking is related to the shear failure of the masonry piers and
spandrels due to excessive stresses induced by in-plane vertical and horizontal forces. Similar extent
of damage is presented in Figure 29 followed by a three-storey RC building irregular in elevation in
Figure 30. Figures 31-33 illustrate a three-storey, irregular in elevation, masonry building with RC
slabs and confined masonry walls that was heavily damaged. The walls were thick enough, but
masonry was constructed using low-strength clay bricks (partially fired or unfired). A detachment of
the external staircase, wide cracks and failure at the corner and partial collapse of the timber roof
were also observed. In addition, the vertical concrete members were constructed with an attempt to
follow an Italian and South American practice from the 1970s for concrete beams utilizing a welded
steel-truss type reinforcement (Colajanni et al., 2017) instead of a regular arrangement of longitudinal
reinforcement bars and transverse. Regarding poor concrete quality, rounded large-size gravel
aggregates were observed in the concrete mixture.
One-storey masonry building with RC slabs and masonry columns is also shown in Figure 34, with
major damage and complete collapse of the masonry-RC frame porch in front of the house. The
collapse of the masonry columns at the entrance resulted in the collapse of the RC roof slab.
Apparently, this part was built at another construction phase and was not properly connected to the
building in order to transfer loads safely. Wide diagonal tension cracks at masonry external and
internal walls and “X”-shaped cracks between openings were observed, along with the partial
collapse of the timber roof.
A two-storey masonry building with stone bricks, extended in plan with R/C frames, with severe
moderate damage of the older masonry part of the structure is shown in Figure 35. The new RC
frame part of the structures suffered no damage at all. It should be pointed herein, that the owner
built the RC frame section on his own, falling back to his experience working in the construction
industry abroad, without any structural design and supervision by licensed professional engineers.
Diagonal tension cracks mainly at masonry walls, partial failures of bricks, wide cracks and
detachments, were observed, as well as partial failure of mortar and bricks at the base of masonry
walls.
Figure 28: Moderate damage of single-storey building in Thumanë
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Figure 29: Moderate damage of two-storey building in Thumanë
Figure 30: Moderate damage of three-storey building in Thumanë
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Figure 31: Major damage of three-storey confined masonry building in Thumanë.
Figure 37 illustrates a two-storey RC building that suffered significant damage in the infill. Shear
cracks due to diagonal tension are observed around the openings, as well as out-of-plane failure,
partial collapse of infill walls, wide cracks and detachments. Concrete spalling is observed at external
columns along with corrosion of longitudinal reinforcement. Despite being built rather recently the
lack of quality control during the construction of the building (or the lack of compliance with up-to-
date standard provisions during the design) is evident from the large and irregular spacing of the
hoops in the RC columns revealed after spalling.
It is worth mentioning that with the exception of the heavy damage observed in the RC building
presented in Fig. 39, very few RC buildings performed poorly in Thumanë. The latter is either due
to the small number of RC buildings that exist in Thumanë (a rural area with a building inventory
dating back to the 1950s) or due to the superior performance of the RC buildings in the seismic
event. It is recalled that in old buildings with extensions of RC systems, damage was only observed
in the older part of the building, whereas the RC part remained undamaged.
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Figure 32: Major damage of three-storey confined masonry building in Thumanë.
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Figure 33: Major damage of three-storey confined masonry building in Thumanë.
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Figure 34: Major damage of single-storey building in Thumanë
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Figure 35: Moderate damage of two-storey masonry building with stone bricks, extended in plan with RC
frames in Thumanë.
Figure 36: Major damage of two-storey RC building in Thumanë
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Figure 37: Major damage of two-storey building in Thumanë
Figure 38: Major damage of single-storey building in Thumanë
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Figure 39: Major damage in the infill brick walls of a two-storey building in Thumanë.
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6.3. Post-Quake Rapid Visual Inspection Aggregated Data
During the field mission, the data (Listed in Table 5) were combined with those collected by the
Earthquake Engineering Field Investigation Team (EEFIT, UK) and resulted into inspection surveys
for 75 buildings mainly in Durrës and Thumanë (Figure 40). The structural typology of the inspected
buildings are depicted in Fig. 41; the categories of structural systems considered are similar to the
ones prescribed in FEMA 154 ((FEMA P-154, 2015). The majority of the 75 buildings inspected
were reinforced concrete (RC) buildings and the most common structural systems were RC4 (RC-
MRF - Modern Code-24%) and URM2 (Unreinforced Brick Masonry with RC slabs-19%). When
the classification considers the height of the buildings, the most common structural typologies of
low-rise (i.e., less than 5 stories) buildings is URM1 (Unreinforced Brick Masonry -29%) and URM2
(Unreinforced Brick Masonry with RC slabs-23%). For higher buildings with more than (or equal
to) 5 stories, the most common structural typology was that of RC4 (RC-MRF - Modern Code-38%)
and RC2 (RC-MRF - Old Code -19%). It should be noted that the buildings’ sample inspected during
the field mission mostly referred to damaged buildings, therefore the statistical distribution and
conclusions should be evaluated considering that the sample was not unbiased in terms of seismic
performance. A summary of building tagging for the entire portfolio of the city of Tirana and
Durres/Kruja/Shijak is given in Tables 5 and 6, respectively.
The distribution of damage level per structural typology of the inspected sample of buildings is
depicted in Fig. 42. Most RC buildings designed with old codes (RC2) and unreinforced brick
masonry (URM1) suffered severe damage. Buildings with designed to modern codes (RC4) and
unreinforced (confined) masonry with RC slabs (URM2), perform better, yet there were cases where
they experienced light-to-moderate damage. When building height (number of storeys n) is
introduced as a classification criterion, with a threshold of n=5), it is evident that for low- to mid-
rise buildings (n<5) the damage extend is higher for URM buildings with the majority of URM1 and
URM2 developing major damage or collapse. The latter were mainly unreinforced brick masonry
(URM1) and RC buildings designed with old codes (RC2), whereas RC buildings designed with
modern codes (RC4) experienced a lower level of damage. For the case of mid- to-high-rise buildings
(n ≥5), the majority of RC buildings designed with modern codes (RC4) experienced only minor to
moderate damage, with most of the older RC buildings (RC2) and unreinforced brick masonry with
RC slabs (URM2), suffering moderate to major. Based on the same figure, the damage extend is
higher for lower buildings (n <5 , T~0.5sec) in accordance with the response spectra presented in
Fig. 5, where for both cases (i.e., earthquake records at the Tirana (TIR) and Durres (DURR) station),
the spectral amplification is higher for a period range T=0,2~0,5sec.
The above damage statistics on the limited sample of 75 characteristic buildings inspected are in
good agreement with the comprehensive post-earthquake inspection campaign in Tirana (Table 6)
(World Bank, 2019) and the qualitative results are in since the majority of buildings with severe
damage (i.e., tagged as red) were low rise buildings, designed with old (pre 1992) codes. It is also
noted that the distribution of tagging (i.e., green, yellow, red) between Tirana (Table 6) and the
municipality of Durrës was also similar (approximately 60% deemed as safe). Figure 43 illustrates
the frequency of damage patterns observed in the building sample inspected. The most frequent
damage type for both low-to-mid height (H<5m), URM (unreinforced masonry) and mid-to-high
RC buildings (H>=5m) was in-plane and out-of-plane wall failure. As anticipated, beam and column,
flexural and shear damage was more frequent for buildings designed with old codes (RC2). Finally,
Figure 44 relates the inspected damage per building height. It is seen that both low- to mid-height
and mid- to high- rise buildings develop in and out-of-plane failure of infill panels, while in plane
failure is more frequent for low-rise buildings, which can be expected given the flexibility of high
rise buildings. Moreover, RC column flexure failure is more frequent in mid- to high-rise buildings,
while shear and short column failure are more frequent for low- to mid-rise ones, as anticipated.
Overall, the damage level developed can be characterized as disproportionate to the seismic intensity.
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However, the damage patterns developed are similar to observed cases after strong earthquake
events in other parts of the world where poor construction quality was also reported.
Table 5: List of collected data using Post-Quake RVI (SAFER)
Location
GPS latitude/longitude, Country
Building Information
Structural System, Extend of damage, Number of Stories, Soil
Conditions, Regularity in plan and elevation
Type of Damage
Settlement (S) Infill panel cracking in plane, Infill panel cracking out of
plane, Beam flexure failure, Beam flexure shear, Column flexure
failure, Column flexure shear, Shear wall failure flexure, Shear wall
failure shear, Short column failure, Joint failure, Soft storey, Pounding
Other Information
Notes, Date/time, Username
Figure 40: Location and density of inspected buildings (each number indicates the number of inspected
buildings in the respective area).
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Number of Stories < 5
Number of Stories ≥5
Figure 41: Structural typologies of inspected buildings
Number of Stories < 5
Number of Stories ≥5
Figure 42: Structural typologies of inspected buildings classified by damage level.
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Table 6: Analysis of building damage statistics in Tirana from the Tirana Municipality by period of
construction, number of floors, type of structure and 3-colour scheme damage levels (World Bank, 2019).
Building characteristics
Green (safe)
Yellow (review)
Red (evaluate)
Pre-1992
56.3%
23.6%
20.0%
Post-1991
71.6%
15.3%
13.1%
Unclassified
47.0%
16.6%
36.5%
1-2 floors
29.8%
22.2%
48.0%
3-5 floors
60.6%
23.5%
16.1%
6+ floors
78.0%
14.0%
8.1%
Unclassified
66.3%
12.5%
21.2%
Adobe walls
17.4%
17.4%
65.2%
Brick Masonry
56.1%
20.9%
23.0%
Concrete Block Masonry
9.1%
9.1%
81.8%
Prefabricated
86.2%
10.3%
3.4%
Reinforced concrete
71.7%
16.0%
12.3%
Structural Masonry
62.8%
21.8%
15.4%
Unclassified
4.0%
36.0%
60.0%
TOTAL
60.6%
19.2%
20.2%
Table 7: Table 3: Building damage statistics from the Office of Natural Disaster Management Operations in
three municipalities in the epicentral region (as of Dec. 10, 2019) (World Bank, 2019).
Durrës
Kruja
Shilak
Combined
Inspected
2112
2499
1670
6281
Safe
1368 (64.8%)
1533 (61.3%)
346 (20.7%)
3247 (51.7%)
Uninhabitable
651 (30.8%)
921 (36.9%)
900 (53.9%)
2472 (39.4%)
Demolition
93 (4.4%)
45 (1.8%)
424 (25.4%)
562 (8.9%)
Demolished
34
12
0
46
Figure 43: Structural pathology of inspected buildings per number of storeys and typology.
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Figure 44: Structural pathology of inspected buildings per number of storeys.
7. GEOTECHNICAL DAMAGE
Based on field observations, the M6.4 earthquake that struck Albania on 26 November 2019, resulted
mainly in structural damage, whereas geotechnical damage was not explicitly reported. However,
there are areas in Durrës, known for their soft soil conditions, which might have contributed to the
observed extent and localization of building damage. The main types of geotechnical phenomena
observed, were soil liquefaction, settlements and permanent ground displacements. They developed
at the coastal area of Durrës, where a number of damaged hotels are located. The map in Fig. 45
(left) shows the liquefaction potential map of the city (Kociu, 2004) with numbers 1, 2 and 3 denoting
areas highly, moderately and high susceptibility to liquefaction, respectively. On the right, it is evident
the location of the hotel buildings that suffered extensive settlement and titling.
/
Figure 45: Liquefaction potential map of Durrës (Kociu, 2004) and map showing the location of Hotels
Lubjana and Villa Verde Beach.
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The Hotel Lubjana situated at the seafront of Durrës, was one of the structures that experienced
such extensive tilt due to soil liquefaction as shown in Fig. 46. The damage was beyond repair and it
was demolished during the first weeks after the seismic event. The Villa Verde Beach Hotel was also
located in the high risk for liquefaction area. Although the main cause of its collapse seems to be the
development of a soft-storey mechanism, the soil conditions may have contributed to the failure.
Figure 46: Tilting of Hotel Lubjana due to soil liquefaction and resulting settlement (left). Collapse of the
Villa Verde Beach Hotel (photos courtesy of J. Psaropoulos)
Figure 47: Permanent ground displacements.
Soil liquefaction, resulting in the ejection of the liquefied material through cracks, due to increased
pore water pressure, affects loose saturated cohesionless soils especially if the cyclic loading has a
large intensity and long duration. Large parts of the coast line of Albania from Vlora to Velipoja are
susceptible to liquefaction (Daja et al., 2016). An example of such liquefaction phenomena observed
in the bay of Porto Romano (10km from Durrës) is shown in Figure 48 with several sand boils and
craters extending across a large area.
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Figure 48: Sand boils and craters due to soil liquefaction in the bay of Porto Romano.
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For the visual inspection of liquefied soils at Porto Romano Bay, two flying drones were used and
the relevant photos were saved and evaluated (Fig. 49). It should be outlined, that despite the fact
that liquefaction phenomena were evident at the Port, no damage was reported.
Figure 48: Drone images of liquefied soils (top). Field mission of the Hellenic Association for Earthquake
Engineering (bottom).
8. SUMMARY AND CONCLUSIONS
The most critical findings of the field mission of HAEE/EPPO team and the rapid visual inspection
performed, are summarised below:
In terms of structural damage:
In Durrës
§ The majority of the buildings in Durrës are masonry infilled RC frame structures with 4 to
10 storeys, built after 1990. Unreinforced confined masonry buildings are also common.
§ Moderate and major damage was observed in many buildings, even some recently
constructed, since they were not designed according to the code provisions.
§ The most common damage pattern observed was the out-of-plane failure of infill walls (both
external and internal) and the collapse of facades. It was observed that the common
construction practice does not connect and confine properly the brick masonry walls to the
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surrounding RC frame, thus leading to out-of-plane failure of infill walls. The vulnerability
of unreinforced, unconfined masonry is particularly highlighted.
§ Other damage patterns involved in-plane, shear diagonal cracking of infill panels and load
bearing masonry walls, as well as concrete spalling, hoop fracture, buckling of longitudinal
reinforcement, concrete core crushing and shear cracking at short-span beams and columns
in RC buildings.
§ The absence of RC concrete cores around the staircase and the elevator of multi-storey
buildings should be outlined. Soft storey mechanisms have also played a detrimental role and
have lead several buildings to collapse.
§ Insufficient quality control and low-quality materials clearly undermined the structural
integrity of buildings, especially of those constructed prior to the enforcement of the latest
KTP-89 seismic code.
In Thumanë
§ Most buildings in Thumanë are single or two-storey (rarely three-storey) structures built after
1950. They are mainly RC frames with brick infills or masonry structures with timber roofs.
§ In most cases, the buildings were constructed by the owners without any structural design
and supervision by licenced professional engineers. Furthermore, most buildings were
constructed in different eras (sometimes more than 30 years apart), using different materials
and structural systems. This unauthorized addition of floors or horizontal expansions,
together with removal of load-bearing elements has contributed to the observed poor seismic
performance in several cases.
§ Most buildings in Thumanë suffered moderate to major damage, and in some cases partial
or total collapse was observed.
§ Structural damage modes are similar to those observed in Durrës.
§ Major damage was also observed at the mosque located in Thumanë. Extended cracking and
spalling at the masonry minaret, at the base and along its height.
Geotechnical damage:
Soil liquefaction, settlements and permanent ground displacements were observed along the coast
of Durrës, leading to or amplifying structural damage. Extensive liquefaction was also evidenced at
Porto Romano Bay.
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