report - Earthquake Clearinghouse

PRELIMINARY REPORT ON THE 2012, MAY 20TH, EMILIA EARTHQUAKE
May 2012, v.1
Luis D. Decanini1 Domenico Liberatore2 Laura Liberatore3 Luigi Sorrentino4
Sapienza University of Rome
Department of Structural Engineering and Geotechnics
via Antonio Gramsci 53,
00197 Roma
Italy
Cite as:
Decanini LD, Liberatore D, Liberatore L, Sorrentino L 2012. Preliminary Report on the 2012, May 20,
Emilia Earthquake, v.1, http://www.eqclearinghouse.org/2012-05-20-italy-it/
1
[email protected]
[email protected]
3
[email protected]
4
[email protected]
2
ABSTRACT
This report presents the results of a preliminary survey in the area affected by the May 20, 2012 Emilia,
Northern Italy, earthquake. In this report, a reconstruction of the local seismic catalogues is presented, the
damage to historical buildings, rural buildings, industrial buildings and reinforced-concrete buildings surveyed
on May 21-22 is described, and a short account on soil liquefaction and strong ground motion is given.
Keywords: May 20, 2012 Emilia, Northern Italy, earthquake; historical seismic catalogues; historical
buildings; rural buildings; industrial buildings; reinforced concrete buildings; soil liquefaction; strong ground
motion.
2
TABLE OF CONTENT
1
2
3
INTRODUCTION ........................................................................................................................................ 4
HISTORICAL CATALOUGES .................................................................................................................... 7
HISTORICAL BUILDINGS ....................................................................................................................... 10
3.1
Mirabello......................................................................................................................................... 10
3.2
Sant’Agostino ................................................................................................................................. 11
3.3
Buonacompra (Sant’Agostino) ....................................................................................................... 13
3.4
Alberone (Cento) ............................................................................................................................ 15
3.5
Massa Finalese .............................................................................................................................. 15
3.6
Finale Emilia................................................................................................................................... 16
3.7
Rivara (San Felice sul Panaro) ...................................................................................................... 19
3.8
San Felice sul Panàro .................................................................................................................... 21
3.9
San Biagio (San Felice sul Panaro) ............................................................................................... 25
3.10
Mirandola........................................................................................................................................ 27
3.11
Mortizzuolo (Mirandola).................................................................................................................. 33
3.12
Casumaro Finalese (Finale Emilia) ................................................................................................ 35
3.13
Not surveyed buildings and preliminary conclusions ..................................................................... 36
4 RURAL BUILDINGS................................................................................................................................. 39
5 INDUSTRIAL BUILDINGS........................................................................................................................ 44
5.1
Sant’Agostino (industrial area) ....................................................................................................... 44
5.2
San Felice sul Panàro (industrial area) .......................................................................................... 49
5.3
Mirandola (industrial area) ............................................................................................................. 50
6 REINFORCED CONCRETE BUILDINGS ................................................................................................ 55
6.1
San Felice sul Panaro .................................................................................................................... 55
6.2
Mirandola........................................................................................................................................ 59
6.3
Sant’Agostino ................................................................................................................................. 64
7 LIQUEFACTIONS..................................................................................................................................... 65
8 STRONG GROUND MOTION.................................................................................................................. 67
Acnowledgements ........................................................................................................................................... 69
References ...................................................................................................................................................... 69
3
1 INTRODUCTION
The 2012 Emilia earthquake occurred on May 20 at 02:03:52 UTC (04:03:52 local time). The local
magnitude is 5.9, the epicentre has coordinates: 44.89°N, 11.23°E, the ipocentral depth is 6.3 km. The
focal mechanism is inverse, with maximum compression along the N-S direction (dip = 46.45, strike =
103.279, rake = 93.87). The municipalities which suffered the highest damage are located in the
districts of Modena and Ferrara (INGV 2012).
The main shock was preceded by foreshocks, begun on May 18, the strongest of which, with local
magnitude 4.1, occurred on May 19 at 23:13:27 UTC. After the main shock, several aftershocks have
been occurring. At 23:00 of May 25, more than 500 events took place, two of which with magnitude
greater than 5.0 (event of May 25, 02:07:31 UTC, local magnitude 5.1; event of May 20, 13:18:02
UTC, local magnitude 5.1), and 15 with magnitude ranging between 4.0 and 4.9. The map of the
aftershocks shows that the epicentres are aligned E from Ferrara, up to a distance of 70 km,
approximately along the E-W direction (INGV 2012).
A first estimation of the macroseismic intensities was performed on the basis of recorded
accelerations and velocities. Because instruments were not present in the epicentral area at the
moment of the main shock, the estimation was performed on the basis of attenuation laws and local
amplification, the latter depending on soil type. The maximum estimated intensity is VII-VIII degree of
the Modified-Mercalli (MM) scale, which corresponds to values slightly greater than VIII degree of the
Mercalli-Cancani-Sieberg (MCS) scale (INGV 2012). The maximum horizontal acceleration measured
in the epicentral area is 0.26 g, while the maximum vertical acceleration is 0.31 g (§ 8).
From historical seismic catalogues, many earthquakes result in the adjacent areas. The area of
Ferrara was stricken by an earthquake with magnitude 5.5 in 1570, with maximum intensity VIII
degree. In 1987, an earthquake with magnitude 5.4 stroke the area between Bologna and Ferrara.
Finally, on July 17, 2011, an earthquake of magnitude 4.7 stroke the area of Reggio Emilia (§ 2).
The present seismic zonation specifies, for the epicentral area and return period of 475 years, an
expected maximum horizontal acceleration approximately equal to 0.15 g on stiff soil, and to 0.22 g on
type C soil. Altogether, based on historical data, the seismicity of the area can be defined as mediumlow (DMIT 2008).
The residential building stock in the area consists of unreinforced masonry and reinforced-concrete
(RC) buildings. The cultural heritage consists of churches, bell towers, towers, palaces and castles.
Several industrial plants, mainly of precast concrete, are present in the area, as well as several
masonry rural buildings. Damage is particularly serious for cultural heritage, industrial plants and rural
buildings. These types of buildings have natural period greater than that of ordinary buildings,
suggesting low frequency components in the ground motion. Moreover, some damage modes
highlight a strong influence of the vertical component, which is common for a near-fault earthquake
with inverse focal mechanism.
The casualties of the earthquake are seven, four of which caused by the collapse of the industrial
plants of three different sites, one by the falling of rubble, and two because of sudden illness (La
Repubblica, May 21, 2012). The injured under treatment in the hospital are 47 (La Repubblica, May
22, 2012). The number of casualties has been limited by the time when the main shock occurred: most
people were in dwellings, which were less damaged compared to industrial plants and churches. It is
also worth mentioning that in the morning of May 20, First Communion and Confirmation were
scheduled in many parish churches, with foreseeable large crowd. Similarly, a main shock during
working hours would have caused much more victims in the plants.
The National Cabinet declared the state of emergency for 60 days in the districts of Bologna, Modena,
Ferrara and Mantua, and decided a first allocation of 50 million Euro, together with the suspension of
real estate taxes for red-tagged houses and plants (La Repubblica, May 23, 2012). The first 10 million
Euro will be used “to cover the expenses for the relief, the assistance, and the provisional
interventions on buildings at risk of collapse” (Gazzetta di Modena, May 23, 2012).
4
On May 23, 5292 people were hosted in the tent cities got ready by the Emergency Management
Agency (DPC = Dipartimento di Protezione Civile), 3515 of which in the district of Modena, 1635 in the
district of Ferrara, 116 in the district of Bologna and 26 in the district of Reggio Emilia. 509 volunteers
are deployed, 178 of which coming from other Regions (Corriere della Sera, May 23, 2012).
According to the safety checks performed by the Fire Service on 2159 dwelling, up to May 23, 98%
resulted safe (Gazzetta di Modena, May 23, 2012).
According to the estimate of Confindustria, the Industrialists Association, the losses to plants amount
to several hundred million Euro. According to the estimate of a union, CGIL Emilia-Romagna, 13 000
workers are temporary unemployed, 7000 of which in the mechanical industry, 1500 in the food
industry and 1400 in the bio-medical industry. 5000 jobs are presently at risk. The losses to agriculture
and cattle-breeding, according to the estimate of Coldiretti, the Farmers Association, amount to 200
million Euro. 450 000 Parmesan and Grana Padano cheese pieces have been damaged (La
Repubblica, May 22, 2012). According to the estimate of Confesercenti, the Traders Association,
almost all the commercial activities inside the historical centres of the stricken municipalities are
damaged (between 70% and 90%). Just outside the historical centres, the damaged activities range
between 20% and 50% (Corriere della Sera, May 24, 2012).
Fig. 1. Investigated area. a: epicentre of the 4.03 shock (ML = 5.9), b: epicentre of the 15.18
shock (ML = 5.1). 1: Mirabello, 2: San'Agostino, 3: Buonacompra, 4: Alberone; 5: Finale Emilia,
6: Massa Finalese, 7: Rivara, 8: San Felice sul Panaro, 9: San Biagio, 10: Mirandola, 11:
Mortizzuolo, 12: Casumaro Finalese.
5
The Attorney of Ferrara opened an inquiry into the collapse of the industrial plants which caused
casualties (La Repubblica, May 22, 2012).
In this report, a reconstruction of the local seismic catalogue is presented, the damage to historical
buildings, rural buildings, RC buildings and industrial plants surveyed on May 21-22 is described (Fig.
1), and a short account on soil liquefaction and strong ground motion is given.
6
2 HISTORICAL CATALOUGES
It is always useful to reconstruct the seismic catalogue of an area in order to corroborate the seismic
hazard studies based on fault location. According to the Italian seismic standard (DMIT 2008) the
municipalities of the area have an expected horizontal acceleration on a horizontal stiff soil for a 475
years return period in the range 0.14-0.15 g (Table 1, last column). Moreover, the knowledge of the
historical seismicity can guide the interpretation of building practices, for instance wall thickness, use
of iron ties, and so on.
Italy is one of the countries with the richest macroseismic observations catalogues. Resorting to the
most up-to-date (Locati et al 2011), starting from 1000 AD, it was possible writing down a first list of
two to twelve events, depending on the considered municipality (Table 1, second column), whose local
felt intensity is above the damage threshold (≥ V MCS).
However, it can be expected that felt earthquakes in the area are more than those. Such limited
number is due to the fact that not always the historical evidence related to earthquakes is still existent,
or has been located or has been studied. In such cases it is useful to exploit an attenuation law to get
felt intensities from known epicentral ones.
In this case the law defined by Decanini and Mollaioli (1997) has been applied to a catalogue of
epicentral intensities (Rovida et al 2011), and again only felt intensities higher than IV-V ° MCS have
been retained. A total (observed + attenuated) list of 18 to 25 events has been reconstructed (Table 1,
third column, and Fig. 2-Fig. 5). Maximum (observed + attenuated) intensity is in the range between
VI-VII and VII MCS. As an example, the local seismic catalogue of Finale Emilia is presented in Table
2; from there it is possible to highlight that 2012 magnitude is the largest so far observed in this part of
the Emilian Po valley.
Different correlations between macroseismic intensity and effective peak ground acceleration are
available in the literature. In this occasion has been used that proposed by Decanini et al (1995),
calibrated over Central Italy data. To make a direct comparison with the acceleration expected for a
specific time span, e.g. 475 years, it is necessary to define the law of occurrence of macroseismic
intensities. Following the approach used for magnitude (Gutenberg and Richter 1954, pp. 16-25), as
already done by Hays (1980) and Decanini et al (2000, pp. 98-102), this law has been reconstructed
for the time window 1117-2011. The same computation has been repeated assuming the time window
1501-2011, obtaining similar results. The acceleration related to a 475 years return period resulted in
the order of 0.08-0.10 g, much lower than that of the code. Recorded values are even higher, at least
in Mirandola where a horizontal PGA of 0.26 g has been reported (RAN 2012). Although this value
may suffer of a high frequency peak, nor is clear if the signal has been corrected, it is evident that the
code values are much closer to what observed than historical macroseismic data, even when the latter
has been enriched through the application of an attenuation law.
Table 1. Macroseismic data for municipalities of the affected area
Municipality
N. of
N. of Maximum
Maximum
observations observations observsed
observsed
+
intensity
+
attenuations
attenuated
intensity
Sant’Agostino
Finale Emilia
San Felice sul
Panàro
Mirandola
2
9
7
25
21
19
° MCS
V
VII
VI
° MCS
VI-VII
VII
VI-VII
Effective
acceleration
related to
occurrence
law of
intensities
g
0.079
0.097
0.087
12
18
VI
VII
0.083
7
2008 code
acceleration
0.140
g
0.153
0.149
0.150
Table 2. Local seismic catalogue of Finale Emilia. Only felt intensities ≥ V MCS considered.
When CFTI11 is the source an attenuation law has been considered to calculate felt intensity.
Felt Source
Year
Month Day Area of maximum
Equivalent Epicentral
intensity
Intensity
effects
moment
magnitude
MCS
MCS
1117
1
3 Veronese
6.69
IX-X
VI-VII CFTI11
1234
3
20 Ferrara
5.14
VII
V CFTI11
1285
12
13 Ferrara
5.14
VII
V CFTI11
1365
7
25 Bologna
5.35
VII-VIII
V CFTI11
1411
1
9 Ferrara
5.14
VII
V CFTI11
1501
6
5 Appennino modenese
5.98
IX
VI-VII CFTI11
1542
6
13 Mugello
5.94
IX
V CFTI11
1570
11
17 Ferrara
5.46
VII-VIII
VI DBMI11
1574
3
17 Finale Emilia
4.72
VI
VII DBMI11
1661
3
22 Appennino romagnolo
6.09
IX
V CFTI11
1688
4
11 Romagna
5.78
VIII-IX
V CFTI11
1695
2
25 Asolano
6.48
X
V-VI CFTI11
1781
4
4 Romagna
5.94
IX-X
VI CFTI11
1891
6
7 Valle d'Illasi
5.86
VIII-IX
V CFTI11
1908
6
28 Finale Emilia
4.27
V
VI DBMI11
VII
1914
10
27 Garfagnana
5.76
VI DBMI11
1963
4
5 Finale Emilia
4.09
V-VI
V-VI DBMI11
1978
12
25 Bassa mantovana
4.52
V-VI
V DBMI11
1986
12
6 Bondeno
4.70
VI
VI DBMI11
1987
5
2 Reggiano
5.09
VI
V DBMI11
1987
5
8 Bassa modenese
4.65
VI
V-VI CFTI11
Intensity (MCS)
8
6
4
2
0
1000
1200
1400
1600
1800
Time (year)
Fig. 2. Time-macroseismic intensity plot of Sant'Agostino.
8
2000
Intensity (MCS)
8
6
4
2
0
1000
1200
1400
1600
1800
2000
Time (year)
Fig. 3. Time-macroseismic intensity plot of Finale Emilia.
Intensity (MCS)
8
6
4
2
0
1000
1200
1400
1600
1800
2000
Time (year)
Fig. 4. Time-macroseismic intensity plot of San Felice sul Panàro.
Intensity (MCS)
8
6
4
2
0
1000
1200
1400
1600
1800
Time (year)
Fig. 5. Time-macroseismic intensity plot of Mirandola.
9
2000
3 HISTORICAL BUILDINGS
The survey of the historical buildings, mainly churches, secondly palaces and fortresses, only in a few
cases ordinary buildings, has been usually performed from the outside. The construction makes
systematic use of unreinforced brick masonry, contrary to what happens in other Italian areas where
rubble masonry is the rule (e.g., Sorrentino et al 2009). The mortar, observed when debris were
present and accessible, is usually average to good, again contrary to what has been noted elsewhere.
Typically, the survey has been performed from the outside, with only a few, remarkable exceptions.
Therefore, damage could be underestimated. Whenever possible the building and the structural
elements have been measured. Building sizes have been surveyed through a laser distance meter.
However, frequently the survey has been performed from a safe position; thus, the figures given in the
following shall be considered approximate.
The churches have usually three naves, with a basilica cross-section, i.e., the central nave is taller
than the lateral ones. The clerestory walls have windows to give light to the main nave. Less frequent,
but observed in a few cases, is a single nave church. Bell towers are very common and rather tall.
This is possibly an indication that past seismicity has been moderate. They could be adjacent to the
building or separated from it. The first case is more frequent in the Modena district, while closer to
Ferrara the opposite happens. It is possible that the separation was suggested by differential
settlements concern, but there is no sufficient data to sustain this hypothesis.
The castles have usually a rectangular layout, with taller square towers protruding from the perimeter.
3.1
Mirabello
The cathedral of Mirabello (corso Italia, Fig. 6a), dedicated to San Paolo, has three naves, the central
one having six bays covered by vertical stacked bond brick masonry vaults. A cloister dome covered
the crossing. The roof is supported by king-post trusses. Evidence of iron ties is present in the
transept (Fig. 7b). The façade is 14.9 m tall (survived portion). On the left of main building is a 56 m
tall bell tower. The current edifice was built between 1929 and 1943, by engineer Luigi Gulli, on the
site of a previous church built in 1795-1804 and later demolished. The bell tower is a design of Gulli as
well dating back to 1905. The church is probably the most damaged church in the area; it has suffered
the out-of-plane collapse of the façade tympanum and the failure of transept and apse. The collapse of
the tympanum has been observed frequently. It seems related to the weak connection to the roof on
one hand, and the good connection between masonry walls on the other. Such connection, made
possible by the brick masonry, involves in the out-of-plane response the adjacent section of the
longitudinal walls (Fig. 6b). The vault on the first bay has collapsed as well, probably as a
consequence of the tympanum-roof collapse. Significant shear cracks are present in lateral chapels.
The left transept, the intersection and the apse have collapsed completely (Fig. 7a). It is difficult to
explain the poor performance of the transept-apse system, compared to the rest of the building.
Probably this part of the construction has suffered some problems in the past, as the steel ties, not
used in the rest of the church, indicate. Moreover, cracks have been observed in the roads close to
this part of the building; perhaps, the soil might have contributed to the observed damages. Finally the
transept was as tall as the central nave, without benefitting from the lateral naves. Surprisingly, and
contrary to what systematically observed elsewhere in this earthquake, no significant damage has
been observed on the bell tower.
10
a)
b)
Fig. 6. Mirabello, Cathedral of San Paolo. Front.
a)
b)
Fig. 7. Mirabello, Cathedral of San Paolo. Back.
3.2
Sant’Agostino
In Sant’Agostino two monumental buildings, being one in front of the other along a N-S axis, have
been surveyed.
The church of Sant’Agostino (piazza I maggio, Fig. 8) has been originally built in the 16th century.
After a disastrous flood severely hit the building in 1763, the current construction has been built at the
beginning of the 19th century (Ferrari-Bravo 2005, p. 710). The church has suffered a triggering of an
out-of-plane mechanism of the 17.0 m tall façade. The mechanism has involved the longitudinal walls,
causing inclined cracks. An horizontal crack at the base of the tympanum seems to suggest a rocking
response. The statues at the left and at the centre of the façade have fallen. The 37.5 m tall bell tower
(neglecting the top spire) has suffered significant shear cracks between the window and the gable.
The tip of the spire has collapsed. The earthquake has blocked the clock mechanism. No evidence of
ties has been observed. At the left of the bell tower there is a smaller sacred building, which has
suffered some damages at the intersection between façade and longitudinal walls.
11
The Town hall (piazza I maggio, Fig. 9) has three storeys above ground level, for a combined height of
12.0 m, and a hip roof. On the main façade a seven bays porticus is present. The brick masonry is just
two withes thick at the second and third storeys. Floors and roof have a timber structure. At least one
opening flat arch presents an iron tie. The palace has been significantly damaged. The pillars have a
large residual out-of-plumb and one of them has collapsed, probably due to a marked out-of-plane
rocking (Fig. 10). It is almost incredible to register that the façade wall above the collapsed pier has
been able to resist gravity loads; however, part of the cross vault failed after loosing its support. It was
probably above such vault that the loose material, observed close to the collapsed pillar, was stored.
The lateral walls have suffered significant shear cracks, more marked toward the porticus. On the right
side, these cracks have induced the collapse of the façade wall corresponding to a large hall having
openings taller than those on the parallel opposite side (Fig. 9b). A terracotta vertical pipe has
contributed weakening the wall. It has to be stressed that this façade was very slender, both vertically
and horizontally. The damage observed on the afternoon of the morning of May 21st is more
pronounced than media reports; thus, the 20th afternoon aftershock has increased the collapse. The
back façade is much less damaged, although shear cracks are present. The observed damage seem
to indicate a strong polarity in the ground motion, directed from the church to the palace, thus inducing
opposite inertia forces. This direction is approximately normal to that of the presumed causative fault
(Fig. 1).
a)
b)
Fig. 8. Sant’Agostino, Cathedral of Sant’Agostino.
12
a)
b)
Fig. 9. Sant’Agostino, Town hall.
a)
b)
Fig. 10. Sant’Agostino, Town hall. Response of the porticus.
3.3
Buonacompra (Sant’Agostino)
The church of San Martino (via Bondonese, Fig. 11) has a single nave, with lateral chapels, and a
semicircular apse. The nave is covered by a reed mat false vault, and the roof is supported by timber
queen-post trusses. Close to the church is a 23.5 m tall bell tower (neglecting the top spire). The
bricks used in the masonry are 280×130×60 mm approximately; the mortar joint is 10 mm thick. The
exam of the debris has highlighted a rather good mortar and a high-quality adhesion with the bricks.
The walls have three withes that do no seem to have a good transverse interlocking. The building has
suffered severe damages. The top half of the façade has collapsed as well as the left clerestory, which
has fallen on the lateral chapels. Consequently the roof of the central nave failed The top masonry of
13
the apse has rotated out-of-plane, resulting in a partial collapse and in a permanent out-of-plumb. The
bell tower has lost the tip of its spire (Fig. 12). Moreover, it suffered a torsion that induced shear
cracks just above the base.
a)
b)
Fig. 11. Buonacompra, municipality of Sant’Agostino, Church of San Martino.
a)
b)
Fig. 12. Buonacompra, municipality of Sant’Agostino, Church of San Martino. Bell tower. a)
Back view; b) lateral view toward the church.
14
3.4
Alberone (Cento)
In Alberone the church of Beata Vergine del Salice (via Chiesa, Fig. 13) has been surveyed. The
building has three naves with an Hallenkirche transverse section, i.e. the naves have similar height
and there is no vertical wall above the lateral naves with windows enlightening the central nave. The
roof is supported by king-post trusses. The façade is 15.1 m wide and 12.7 m tall; the nave, having
three bays, is 15.9 m long. The pillars are roughly .0.8 m wide. The apse is polygonal. Close to the
church is a 26.8 m tall bell tower (neglecting the top spire). The bricks used in the masonry are
300×140×50 mm approximately; the mortar joint is 10 mm thick. There is no evidence of ties in the
church or the bell tower, although they are present in buildings close by. The church has suffered the
collapse of the back tympanum, which consisted of a rather thin brick masonry. It is possible that the
Hallenkirche solution has contributed to the better performance, compared to other surveyed
buildings. The bell tower has a quasi-horizontal crack close to the base.
a)
b)
Fig. 13. Alberone, municipality of Cento, Church of Beata Vergine del Salice.
3.5
Massa Finalese
A church dedicated to San Geminiano has been built in Massa Finalese by marquises Aldrovandino
and Jacopo Rangone in 1385. The current building (via per Modena, Fig. 14) does not retain much of
the late-medieval one. The façade, 12.0 m tall, is neoclassic. The plan presents three naves, with a
central apse covered by a masonry vault. Laterally three chapels per side are present. In 1926 a new
bell tower replaced the previous one of limited height. The façade has been acted out-of-plane; cracks
involve the longitudinal walls close to the façade, and some limited collapses are present in the same
region of both clerestories. Shear cracks are present in the main plane of the façade. The bell tower,
separated form the church, has only minor corner spalling.
15
a)
b)
Fig. 14. Massa Finalese, Church of San Geminiano.
3.6
Finale Emilia
Finale Emilia has been one of the centres most damaged by the earthquake. During the survey it was
possible to visit only some buildings, while for others media reports have been used to gain an
indication about the damage level.
The cathedral of Santi Filippo e Giacomo (corso Giuseppe Mazzini, Fig. 15a) has the exterior and the
bell tower dating back to the 15th century. The interior, with a three naves layout, and the façade are
of the 18th century (Ferrari-Bravo 2005, p. 366). The central nave is covered by reed mat false vaults,
hanged to the queen-post trusses. The masonry walls seem to a have a less than perfect transverse
interlocking. As a consequence of the earthquake, the façade has suffered the collapse of the
tympanum. Currently the performance of the bell tower is unknown.
The Town hall (piazza Verdi, Fig. 15b) is a 1744 palace. The building has three stories and an attic
above ground level. As a consequence of the shaking the bell gable suffered the collapse of one of its
two-withes brick-masonry support.
The clock (or Modenesi) tower is a 1212 construction, rebuilt in the 15th century (piazza Alfredo
Baccarini, Fig. 16). The tower had four levels above ground level, covered by barrel vaults. There is no
evidence of iron ties. The tower collapsed as a consequence of the two main shocks: 4.03 and 15.18
(local time), May 20th (Fig. 1). After the first shock only the east portion of the tower collapsed; it is
possible that the thrust of the barrel vaults contributed to this type of damage.
The Rocca Estense (viale Trento e Trieste, Fig. 17), was built in 1402 by Bartolino da Novara on a
previous medieval fort. In 1425-30 Giovanni da Siena enlarged it (Ferrari-Bravo 2005, p. 365).
Currently is partially underground, due to the deviation of river Panàro. The building has been restored
at the turn of the millennium; there is evidence of reinforced concrete interventions. The structures on
viale Trento e Trieste, including the main tower, dramatically collapsed; the top of the internal cloister
failed as well. Moreover, the upper portion of the N-W tower suffered a partial collapse. The tower,
which was reinforced by a steel double ring, collapsed almost on its own position. This could be
evidence of a significant vertical ground motion (§ 8). It has been shown that masonry walls having not
appropriately connected withes can be particularly sensible to this type of ground shaking (Meyer et al.
2007).
The church of Annunziata (via Aurelio Saffi, Fig. 18), has the nave covered by reed mat false vaults,
hanged to queen-post trusses. The façade is 14.4 m wide and 9.5 m tall. The brick used in the façade
is 280×160×60 mm approximately; the mortar is of good quality. During the years before the
earthquake, the building was unused. The façade suffered the out-of-plane collapse of the tympanum.
An iron wall anchor, having square cross-section, whose side in equal to 26 mm, while the length of
the element is around 0.9 m, has been observed among the debris.
16
The palace in via Cesare Frassoni 21a (Fig. 19) has two storeys and an attic above ground level, for a
combined height of 17.0 m approximately. The second floor is very tall, containing a large hall. Such
large wall was just two withes thick. Moreover, the building seemed to be not well maintained. The
connection between the trussed roof and the masonry walls was apparently relying only on friction. It
is worth noting that other palaces on the same street have suffered much less damages, mainly
limited to vertical cracks aligned with the openings. The same applies to ordinary unreinforced
masonry buildings of the historical centre. Even potentially vulnerable buildings, such as those
displaying cloisters on pillars (intersection between via G Oberdan and via G Marconi) are unscathed.
a)
b)
Fig. 15. Finale Emilia. a) Cathedral; b) Town hall.
17
Fig. 16. Finale Emilia. Clock (or Modenesi) tower (from: www.ansa.it). a) before the earthquake;
b) after the 4.03 shock; c) after the 15.18 shock.
a)
b)
Fig. 17. Finale Emilia, Rocca Estense. a) Before (www.google.it) and b) after the earthquake
(www.ilrestodelcarlino.it).
18
a)
b)
Fig. 18. Finale Emilia, Church of Annunziata.
a)
b)
Fig. 19. Finale Emilia, Palace in via Cesare Frassoni 21a.
3.7
Rivara (San Felice sul Panaro)
The church of the Natività di Maria Santissima (via degli Estensi, Fig. 20) has a large nave, covered by
a flat soffit, hanged at the roof. On the sides are shallow chapels.
The building has suffered the collapse of the tympanum. In this case it is possible to highlight that the
roof has been rebuilt, resorting to precast beams and thin clay blocks (Fig. 20b). This type of damage
has been observed in other churches whose original timber roof has been replaced by a reinforced
concrete one (Sorrentino et al. 2009). There is a crack between the façade and the longitudinal walls,
but the good masonry quality has avoided the out-of-plane overturning of the façade (Fig. 21a). The
16.4 m tall (excluding the top spire) bell tower has the base corners cracked (Fig. 21b); the tower
appears to be out-of-plumb. The bell gable, strengthened by ties lying within the wall section, has
sustained the shaking without visible damage.
Close to the church a war memorial obelisk has collapsed due to the shaking (Fig. 22). The base has
a square cross-section, 0.47 m wide. The obelisk has a base 0.33 m wide, that is tapered to 0.23 m at
the top, the height of the obelisk is 1.55 m.
19
a)
b)
Fig. 20. Rivara, municipality of San Felice sul Panàro, Natività di Maria Santissima.
a)
b)
Fig. 21. Rivara, municipality of San Felice sul Panàro, Natività di Maria Santissima. a)
Triggering of the out-of-plane mechanism of the façade; b) spalling of the corners at the base
of the bell-tower.
20
a)
b)
Fig. 22. Rivara, municipality of San Felice sul Panàro, war memorial.
3.8
San Felice sul Panàro
Similarly to Finale Emilia, San Felice sul Panàro has been one of the centres most damaged by the
earthquake.
The church of San Felice (corso Mazzini, Fig. 23a) is a 15th century building with a neoclassic façade
(Ferrari-Bravo 2005, p. 364). The church has a large single nave, with chapels on the sides, covered
by vertical stacked bond vaults. The apse was covered by a reed-mat quarter-of-sphere false vault. At
the left of the vault was a squat bell tower (Fig. 24a). The brick masonry walls are three withes thick;
there is extensive use of iron ties (Fig. 23b), sometimes embedded within the masonry section. The
tympanum of the façade has collapsed out-of-plane, and the lower part of the wall has been detached
from the longitudinal walls. Moreover, it suffered extensive in-plane cracks. Inclined and quasi-vertical
in-plane cracks are visible in the chapels. The vaults and the roof failed completely, possibly as a
consequence of the collapse of the bell tower (Fig. 24b).
The church of San Giuseppe (via del Molino, Fig. 25) is a three-naves, basilica-section church. The
central nave is covered by a vertical stacked bond brick-masonry barrel-with-lunes vault, ant the roof
is supported by king-post trusses. The façade is 11.9 m wide and 7.2 m tall; the naves are 17.7 m
long. The brick masonry walls are three-withes thick, with average to poor transverse connection. The
church presents tapered buttresses on the right side and on the apse (Fig. 25b and Fig. 26a). Iron ties
are present across the central nave and along the arches between the naves. A tie is embedded
within the façade and a ring tie reinforces the top of the apse. These ties were fully engaged by the
earthquake, which caused the failure of at least one of them (Fig. 26b). They certainly contributed to
limit the damages, although this was very extensive. The top of the façade has collapsed out-of-plane,
thus affecting the adjacent roof. This mechanism caused the cracking of the connection between
façade and longitudinal walls. The vaults of the naves and of the transept partially collapsed, and
those survived are markedly deformed. Extensive cracks are present in the arches and the upper
longitudinal walls between the naves (Fig. 26b). The apse ring tie was effective in preventing the
cracking of the top masonry, but a significant inclined crack is present at a lower height.
Probably the most prominent monument of the city is the Rocca Estense (corso Mazzini, Fig. 27). Built
in 1340 by Bartolino da Novara, was refurbished in the 15th century (Ferrari-Bravo 2005, p. 364). The
fortress suffered the collapse of the roof on all the secondary towers, while the main tower presents
inclined cracks at the corners and a vertical crack through the base opening. A similar crack is present
21
in the NE tower as well. However, the damage level is not as dramatic as in the similar Rocca of
Finale Emilia. The main body of the castle, where ties are present and that is buttressed by the
towers, seem to have sustained much less damages.
As systematically observed in this earthquake the performance of the churches has been much worse
compared to the that of residential buildings. A few partially collapsed buildings have been observed
close to San Felice (Fig. 28) and on via Terrapieni (Fig. 29). The affected buildings seemed not
adequately maintained. Moreover, they might had suffered an amplification related to land fill. Overall,
the cases of partial collapse of unreinforced-masonry ordinary buildings have been very rare.
Overturned artefacts have been observed more than once both at ground level (Fig. 30), or in gables
(via Fossetta). Boundary walls have collapsed rather frequently.
a)
b)
Fig. 23. San Felice sul Panàro, San Felice. a) Façade; b) Connection between façade and right
longitudinal wall.
a)
b)
Fig. 24. San Felice sul Panàro, San Felice. Left side: a) before (www.google.it) and b) after the
earthquake.
22
a)
b)
Fig. 25. San Felice sul Panàro, San Giuseppe.
a)
b)
Fig. 26. San Felice sul Panàro, San Giuseppe. a) View froim the outside of the transept; b)
Apse.
23
a)
b)
Fig. 27. San Felice sul Panàro, Rocca Estense (a from: www.ilrestodelcarlino.it).
a)
b)
Fig. 28. San Felice sul Panàro, Buildings on via Circondaria.
24
a)
b)
Fig. 29. San Felice sul Panàro, Buildings on via Terrapieni.
a)
b)
Fig. 30. San Felice sul Panàro, Overturned artifacts. a) via Garibaldi; b) via del Molino.
3.9
San Biagio (San Felice sul Panaro)
The church of San Biagio (via Primo Maggio, Fig. 31) has a single nave with some side spaces. The
nave is covered by a reed mat false vault hanged to king-post trusses. Close to the semicircular apse
was a bell tower (Fig. 32a). Adjacent to the church are smaller buildings. The façade is 13.0 m wide
and 7.0 m tall (survived portion); the nave is 17.8 m long. The brick masonry is just two-withes thick.
The building suffered the out-of-plane collapse of the upper part of the façade. The connection to the
transverse walls has been cracked. The roof of the nave has failed. Moreover, the bell tower collapsed
on top of one of the adjacent buildings (Fig. 31a and Fig. 32b). Extensive quasi-vertical and inclined
cracks are present in most of the walls. In the case of the building at the rear of the church, they are at
least partially induced by a very large rafter, which caused also marked deformations (Fig. 31b).
Close to the church is also a canopy (Fig. 33), which has been badly damaged by the earthquake
despite the presence of ties on each of the four sides. Apparently these failed without being able to
present the overturning of one of the pilasters. This collapse caused that of the roof. At the time of the
survey the municipality was considering the demolition of the survived structures.
25
a)
b)
Fig. 31. San Biagio, municipality of San Felice sul Panàro, Church of San Biagio.
a)
b)
Fig. 32. San Biagio, municipality of San Felice sul Panàro, Church of San Biagio. The bell
tower: a) before (www.google.it) and b) after the earthquake.
26
a)
b)
Fig. 33. San Biagio, municipality of San Felice sul Panàro, Canopy close o the church: a) before
(www.google.it) and b) after the earthquake.
3.10 Mirandola
The preliminary survey of Mirandola has shown a lesser damage level compared to San Felice sul
Panàro and Finale Emilia, especially with regard to the historical buildings.
The church of San Francesco (via Volturno, Fig. 34a) has three naves with three bays in the central
one, and six in the lateral ones. The naves are covered by ribbed cross vaults. The intersection
between central nave and transept is covered by a dome. To the left of the polygonal apse is a bell
tower. Iron ties are systematically used in the building, both in the transverse and the longitudinal
directions. The chapel at the end of the right nave has a top iron ring (Fig. 34b), probably related to the
thrusting rafters roof (Fig. 36b). In the bell tower, just above the roof of the church is an iron ring and a
set of four ties, one per side (Fig. 35b). Apparently above the bell gable is present only one tie on the
N side (opposite to the church). The façade is 14.3 m tall and 19.8 m wide; the naves are 26.4 m long.
Already existing in the 13th century, the building has been remade in the 15th century (Ferrari-Bravo
2005, p. 379). The church has been damaged, but the ties seem to have effectively limited the
impairment. The connection between façade and longitudinal walls has been severed (Fig. 35a). The
vaults are extensively cracked, but there seem to be just one significant displacement: in the
transverse arch between first and second bays of the central nave, and the collapse of the transverse
arch between first and second bays of the right nave. The vertical stacked bond flat vault above the
chapel at the end of the left nave has collapsed, despite the iron ring, due to a spreading of the walls,
which cracked the arches. The dome above the intersection presents a horizontal crack, as typical in
such structures when excited by earthquake ground motion (Sorrentino et al. 2009). The bell tower
has its corner spalled just above the church roof, while the iron ring has been effective in preventing
the formation of cracks.
The cathedral of Santa Maria Maggiore (via Giovanni Pico, Fig. 37) has a three-nave basilica-type
cross section. The bell tower is to the right of the apse. Iron ties connect the façade to the longitudinal
walls between the naves; they are present also in the bell tower below the lower gable (Fig. 38). The
bell tower has a stone-plate date of 1449. However, this is probably related the construction of the
church by Giovanni and Francesco Pico. The current bell tower dates back to the 17th century, while
the façade is of the 19th century (Ferrari-Bravo 2005, pp. 378-379). The church suffered the initiation of
an out-of-plane mechanism, which caused the failure of the connection with the transverse walls and
yielded the wall anchors (Fig. 38a). Moreover, the centre-left spire of the façade collapsed, while the
centre-right and the left ones are cracked at the base (Fig. 37b). The bell tower is cracked above and
below the lower gable (Fig. 38b).
The oratory of Santa Maria della Porta (piazza Costituente, Fig. 39) has a central plan layout,
organised around a vertical axis. The church was built in 1602-1604 and financed by Federico II Pico,
27
although the façade dates to 1868. A small bell gable is present on the back right corner. The drum
displays shear cracks on all the eight sides, more pronounced where windows are present. The
corners of the pillars of the bell gable are cracked. The façade has a central vertical crack. At least
from the outside, the overall damage level seems light.
No significant damage was visible in the façades of the Gesù and of the Sacramento churches.
The Town hall (piazza Costituente, Fig. 40a), built in 1468 (Ferrari-Bravo 2005, p. 378), has three
storeys above ground level, and two porticus: on the main façade of piazza Costituente and on the
opposite façade on via Castelfidardo (Fig. 41a). The first porticus rests on stone round columns (Fig.
40b); the second on square brick pillars. The walls show a multiple-withes masonry, with poor
transverse interlocking in some points. Iron ties are used in the front porticus and in the back porticus,
where two levels are present (Fig. 41b). Ties embedded within the wall section are present also at the
intersection between via Castelfidardo and via Curtatone. The palace has suffered limited outside
damage. The corner columns of the main façade show spalling at the base, probably as a
consequence of initiation of rocking (Fig. 40b). The domical vaults of the back are cracked.
Nonetheless the performance is much better than that of the Town hall of Sant’Agostino (§ 3.2).
The origin of the extensive use of ties in the area is not clear, considering that in Mirandola the
maximum macroseismic felt intensity before 2012 has been VII MCS. However, two levels of ties are
present also in the palace Bergomi in piazza Costituente. Moreover, an ordinary building at the
intersection of via Castelfidardo and via Giuseppe Luosi shows timber girders systematically
connected to the walls through iron strips and wall anchors (Fig. 42). This solution is similar to that
proposed in Luigi Valadier’s treatise (Fig. 43).
a)
b)
Fig. 34. Mirandola, Church of San Francesco. a) General view; b) Roof of the chapel at the end
of the right nave.
28
a)
b)
Fig. 35. Mirandola, Church of San Francesco. a) Connection between façade and right
longitudinal walls; b) Bell tower.
a)
b)
Fig. 36. Mirandola, Church of San Francesco. a) Vaults of the central nave; b) Chapel at the end
of the right nave.
29
a)
b)
Fig. 37. Mirandola, Cathedral of Santa Maria Maggiore.
a)
b)
Fig. 38. Mirandola, Cathedral of Santa Maria Maggiore. a) Yielded wall anchor of the façade; b)
Cracks and ties in the bell tower below the lower gable.
30
a)
b)
Fig. 39. Mirandola, Oratory of Santa Maria della Porta.
a)
b)
Fig. 40. Mirandola, Town hall. Façade on piazza Costituente: a) General view; b) Spalling of one
the corner column.
31
a)
b)
Fig. 41. Mirandola, Town hall. Façade on via Castelfidardo: a) General view; b) Two levels of
ties and cracks in the vaults.
a)
b)
Fig. 42. Mirandola, Building at the intersection of via Castelfidardo and via Giuseppe Luosi.
32
a)
b)
Fig. 43. Tying the walls together and to the floors (Valadier 1828-39, vol. 4, plate 276).
3.11 Mortizzuolo (Mirandola)
The church of San Leonardo Limosino (via Imperiale, Fig. 44) has three naves, with two bays in the
central one and four in the lateral naves. The naves are covered by cross vaults; the roof is supported
by king-post trusses. To the left of the round apse is a bell tower. The façade presents two ties
embedded within the wall section: an iron tie at the top of the lateral naves, a timber tie just above the
central window (Fig. 45a). Two sets of iron ties strengthen the bell gable. The façade has a maximum
height of 11.5 m, while the lateral naves are 5.4 m tall and the apse is 6.2 m tall. The naves are 13.4
m wide and 22.4 m long. The bell tower is 22.0 m tall, neglecting the spire. The church dates back to
the 15th century, while the parish house is of the 18th century. The building has suffered important
damages. The tympanum of the façade collapsed out-of-plane, with the mechanism influenced by the
timber tie as observed in churches of the district of L’Aquila (Sorrentino et al. 2009). There are other
inclined cracks in the top part of the façade, while the iron tie seems to have been effective in
preventing damages in the lower part of the wall. The connection between façade and longitudinal
walls has been severed both in the clerestory and in the lateral walls (Fig. 45b). However the most
evident damage is that of the bell tower, which has lost the tip of its spire, presents vertical cracks
below the gable, and has its corner spalled just above the roof level of the church (Fig. 46). Moreover,
the tower presents an evident out-of-plumb. A boundary wall collapsed.
33
Fig. 44. Mortizzuolo, municipality of Mirandola, Church of San Leonardo Limosimo.
34
a)
b)
Fig. 45. Mortizzuolo, municipality of Mirandola, Church of San Leonardo Limosimo.
a)
b)
Fig. 46. Mortizzuolo, municipality of Mirandola, Church of San Leonardo Limosimo.
3.12 Casumaro Finalese (Finale Emilia)
The church of San Lorenzo (via Correggio, Fig. 47) has a single nave layout with a bell tower to the
right of the building. The façade is 9.6 m wide and 12.3 m tall; the bell tower is 17.6 m tall (neglecting
the spire). The building façade has the connection to the longitudinal walls cracked; a vertical central
crack connects the openings. However, the most significant damage is that of the bell tower. Although
the front view might suggest that the tower is separated from the main building, the back view shows
this not to be the case. Therefore, the tremendous change of vertical stiffness has brought to
extensive and severe cracking of the base.
35
a)
b)
Fig. 47. Casumaro Finalese, municipality of Finale Emilia, Church of San Lorenzo.
3.13 Not surveyed buildings and preliminary conclusions
The phenomena surveyed directly have been observed on other buildings quoted in media reports.
The bell tower of the church of Caselle (Fig. 48a) has suffered a corner mechanism just above the
height of the main building. The bell gable on the main tower of the Rocca Estense in Ferrara has lost
one of its pillars (Fig. 48b), similarly to the Town hall of Finale Emilia. The tower of the Town hall of
Poggio Renatico has collapsed similarly to the tower of the Rocca Estense in Finale Emilia (Fig. 49).
Built as a castle in 1475 by the Bolognese family Lambertini, the Town hall was almost completely
rebuilt two centuries later. It was transformed in 1880 and 1898 (Ferrari-Bravo 2005, p. 710). Partial
exceptions to the confirmation of previously observed phenomena are the castles of Galeazza and
Ronchi, where the damage has affected the lower buildings and not the towers (Fig. 50).
Therefore, from indirect and direct observations the following preliminary conclusions can be drawn.
The masonry quality is average to good. Thus, no clear example of masonry disgregation has been
observed, contrary to what frequent in and around L’Aquila (Sorrentino et al. 2012). Nonetheless,
sometimes the transverse interlocking is not adequate. The quality of the masonry, together with the
limited height, is certainly the reason for the low damage level observed from the outside in ordinary
buildings. Moreover, in churches, it limited the local collapse mechanisms. These are usually
concentrated in the tympanum of the façade, suffering from a poor connection to the roof, or in the top
portion of the façade where friction reaction is lower due to reduced gravity load.
The use of ties is not frequent, probably due to the moderate historical seismic activity. It appears to
be more systematic in Mirandola, although it has been observed also elsewhere. In some cases, such
as San Francesco in Mirandola, it has been crucial to preserve the building from worse damages.
However, in the case of the main tower of the Rocca Estense in Finale Emilia the iron rings where not
enough. It is possible that this failure is related to a significant vertical component of the ground motion
(§ 8), because the debris is rather close to the construction’s original position.
The performance of the bell towers can be classified into two cases: bell tower 1) independent or 2)
connected to the main building. It is not clear what the origin of the first solution, more common in the
Ferrara district, is. Probably the soft soils usually present in this area suggested a separation between
tower and church in order to reduce the shortcomings of differential settlements. Anyway, from an
earthquake engineering point of view, this avoided pounding phenomena and shear cracks due to
severe change of the stiffness along the height of the construction. On the contrary, the second
36
solution has brought to much worse performance with very marked shear and corner cracks, only
partially limited by the presence of steel ties and rings.
a)
b)
Fig. 48. a) Church of Caselle, municipality of Crevalcore; b) Rocca Estense of Ferrara
(www.ilrestodelcarlino.it).
a)
b)
Fig. 49. Town hall of Poggio Renatico: a) before (www.comuninverso.it), and after the
earthquake (www.ilrestodelcarlino.it).
37
a)
b)
Fig. 50. Caste of: a) Galeazza, and b) Ronchi, municipality of Crevalcore
(www.ilrestodelcarlino.it).
38
4 RURAL BUILDINGS
The May 20, 2012 earthquake stroke an area of agricultural production, with several rural buildings
spread over the territory. The rural buildings stock consists of dwellings and stable-haylofts. These
buildings have little relevance if considered individually, but altogether witness the traditional rural
civilization of the area. Part of these buildings is still used as hayloft and shelter of machinery.
In the Bologna Po valley the house is separated from the stable-hayloft, as a consequence of the
richer condition compared to other Italian areas, such as Tuscany (Barbieri and Gambi 1970, p. 213).
This has been observed frequently in the investigated area. According to Ortolani (1953, p. 36)
already in the 18th century this separation was rather common. The dwelling has usually a rectangular
layout, with a double-pitched roof; typically the stable-hayloft is bulky.
In the Ferrara countryside the farm is usually called boarìa, whose etymology comes from bue = ox.
The reason of this name lies in the fact that the sharecropper was responsible also for the cattle
(Castellano 1986, p. 178). The presence of the livestock called for large stables and ample farms. The
buildings frequently present refined architectural elements, for instance pilasters, capitals, arches,
related to the urban origin of the landowners.
There is a large use of porticus, documented also in archive drawings (Fig. 51a).
The specific lithology of the area (§ 6) made the stone a very expensive building material (Ortolani
1953, p. 11). This explains the wide use of brick masonry. However, because the fuel necessary to fire
the bricks was rather short, and thus expensive, unfired bricks were rather common. Fired bricks were
used only up to the height of the expected flood. As a matter of fact, the 1886 Reno river flood, 1.5 m
high, induced in the Bologna district several collapses in unfired brick masonry buildings (Ortolani
1953, p. 18). Fired bricks became more affordable when the road system improved, and grew to be
prevalent in the 19th and 20th centuries (Ortolani 1953, pp. 36-38).
a)
b)
Fig. 51. a) San Martino in Rio, Modena district, Villa di Prato. Archive drawing, 1771: 1: rural
dwelling, 2: stable; 3: porticus, 4: oven (Ortolani 1953, fig. 7). b) Plan of a typical Ferrara stablehayloft (Ortolani 1953, fig. 13).
The house has usually two storeys above ground level, for a combined height of 5-6 m. In the Modena
Po valley the building has usually three storeys, but a smaller plan surface. The walls are 30 cm, twowithes, thick; they are not plastered (except close to Modena). There is frequently a porticus in front of
39
the house, built with 60×60 cm brick masonry pillars. The roof, of both porticus and house, have oak
girders and poplar beams. The second storey of the house is used for storage of commodities, and is
not inhabited (Ortolani 1953, pp. 43-46).
The stable-hayloft is a tall canopy that hosts the stable in a central position at ground floor. The hay is
stacked above the stable. A porticus is present on one or more sides of the building (Fig. 51b). Both
the porticus and the roof are supported by 60×60 cm brick masonry pillars. The porticus, porticaglia in
local dialect, is used to shelter straw, carts and machinery (Ortolani 1953, p. 47).
Another typical construction is the so called casella or barchessa (Fig. 52b). The building is an
elongated rectangular canopy, supported by king-post trusses resting on 60×60 cm brick masonry
pillars, 5-7 m tall. The back side is usually infilled by a single wythe wall (Ortolani 1953, pp. 52, 87-88;
Castellano 1986, p. 181), sometimes in a vertical stacked bond. The construction is used for stacking
hemp (Ferrara and Bologna) or straw (Modena).
The stable-hayloft is normally made of masonry piers and walls. The roof is made of timber king posts
or timber beams. In the latter case the roof exerts a thrust on the piers. In some cases tie-rods are
present.
The stable-hayloft has a high seismic vulnerability, because of the slenderness of masonry piers and
walls, the large distance between the walls, the flexibility of the roof, the poor connection between roof
and piers.
Approximately one hundred rural buildings suffering from a partial or total collapse have been counted
along the two hundred km of survey performed. Damage typically consists of out-of-plane failure of
masonry piers and walls. Some cases are described in the following.
A collapsed rural building close to Sant’Agostino shows flexural collapse of the façade because of the
lack of intermediate walls and restraint from the roof. A good connection with perpendicular walls can
be observed (Fig. 52a).
A hayloft in Massa Finalese, on via per Modena, close to via Canaletto, shows tilting of the piers and
out-of-plane collapse of the walls (Fig. 52b).
A rural building in Massa Finalese, on via per Modena close to via Monte Bianco, shows: flexural
collapse of the wall because of the lack of restraint from the roof (Fig. 53a), tilting of the masonry piers
of the porticus (Fig. 53b), ineffective connection between the pier and the wall with ensuing debonding
(Fig. 53c), thrusting roof (Fig. 53d).
a)
b)
Fig. 52. a) Collapsed rural building in Sant’Agostino, close to Strada Statale 225, in front of
collapsed factory (Fig. 57); b) Barchessa ina mssa Finalese, on via per Modena, close to via
Canaletto.
40
a)
b)
c)
d)
Fig. 53. Stable-hayloft in Massa Finalese, on via per Modena, close to via Monte Bianco.
A rural building at Buonacompra, municipality of Sant’Agostino, has been surveyed. It is 22.5 m long,
13.0 m wide and 5.5 m tall at the eaves of the roof. The piers have 0.6×0.6 m cross-section, with
280×130×60 mm, with 10 mm thick mortar. The building has a thrusting roof and shows: short-column
failure of the piers just above the inner stable walls (Fig. 54a), decayed mortar and rough repointing in
a pier (Fig. 54b).
A rural building in Finale Emilia suffered total collapse (Fig. 55a). A detail of a collapsed corner pier
and two withes walls is shown in Fig. 55b. From the cross section of a pier, the lack of interlocking
between the inner core and the outer leaf can be observed (Fig. 55c), although the piers usually
collapsed without a marked disgregation. A detail of a steel beam of the roof shows an advanced
corrosion state (Fig. 55d).
A set of rural buildings in Finale Emilia shows some constructive solutions and related damage. A
casella, 17.1 m long, 8.6 m wide, 5.5 m tall, with walls on three sides is shown in Fig. 56a. The high
slenderness of the 0.6×0.6 m2 piers and of the walls can be observed, as well as the lack of
intermediate walls; the collapse involved part of the wall top and of the roof; the piers are tilted.
Another view is shown in Fig. 56b: the timber king-post trusses can be observed, as well as the
longitudinal tie-rods meant to equilibrate the thrust of the arches. Another building, 20.6 m long, 8.6 m
wide, 5.5 m tall, is shown in Fig. 56c, which has tie-rods at the first level along the transverse and
longitudinal directions; most probably, tie-rods are present also at the top, as indicated by the cracks.
A masonry silo confined by 50×8 mm2 metal strips to contrast the inner pressure is shown in Fig. 56d.
It can be noted that the three lowest strips were removed in order to open the door at the ground level.
The earthquake caused the fall of part of the top.
41
a)
b)
Fig. 54. Rural building in via Alberghini at Buonacompra, municipality of Sant’Agostino.
a)
b)
c)
d)
Fig. 55. Collapsed rural building in Finale Emilia, on via per Modena, close to via Canalvecchio.
42
a)
b)
c)
d)
Fig. 56. Set of rural buildings in Finale Emilia, on via per Modena, close to via Trombata.
43
5 INDUSTRIAL BUILDINGS
A significant number of industrial buildings are present in the affected area. The majority of the
surveyed building are made of precast reinforced-concrete elements. Precast structures are often
used in Italian industrial buildings. Thorough inventories of the typologies of precast buildings adopted
since the late 1940s of the last century in Italy are reported in Bonfanti et al. (2008a, 2008b) and
Capozzi (2010). Extensive studies on the seismic behaviour of the precast existing structures have
been performed in the context of the ReLUIS Project, Line 2, 2005-2008 (Cosenza and Monti, 2009
and references therein). Key aspects that have been identified are: dry friction supports, diaphragm
action, lateral supports and second order effects.
In the area affected by the strong ground motion, some recent buildings, built during the last decades
collapsed. Many of these building were not designed to withstand seismic action because the zone
was not classified as a seismic prone area. Only since 2003, the affected municipalities were included
in the third seismic zone (anchor point of the acceleration spectrum ag = 0.15 g) of the seismic
classification.
Examples of collapse are reported in the following. The majority of the surveyed buildings have been
inspected only from the outside and just preliminary hypothesis can be made on the causes of failures.
5.1
Sant’Agostino (industrial area)
The building reported in Fig. 57 was used for the storage of pottery produced in a near factory. The
building seems made of steel truss stands connected to each other only at roof level, where a truss
beam linked the stands in the transversal direction (Fig. 58); in the longitudinal direction no braces are
visible. The high flexibility of the structure and the presence of considerable masses are likely to be
the causes of collapse. The second order P-∆ effect due to the horizontal deformations and increased
by the heavy masses triggered the loss of stability and bought to the consequent total failure of a
significant part of the building (Fig. 59).
Fig. 57 Sant’Agostino, pottery warehouse on Strada Statale 225, close to Roversetto.
44
Fig. 58 Sant’Agostino, pottery warehouse.
Fig. 59 Sant’Agostino, pottery warehouse.
In Fig. 60 the collapse of a precast RC building is shown. The beams are simply supported on the
columns, and are laterally restrained by RC elements, many of which failed due to the pounding
between the beam and the restraint (Fig. 61). In the collapsed part of the building the fall of the roof
was due to the unseating of the beams (Fig. 62a).
Beams in the longitudinal direction of the building are not present. The external RC panels were not
adequately connected to the structure and many of them fell down (Fig. 62b), also due to the pounding
with the contents.
45
Fig. 60 Sant’Agostino, precast RC industrial building on Strada Statale 225, close to
Roversetto.
a)
b)
b)
a)
Fig. 61 Sant’Agostino, precast RC industrial building. Failure of lateral restraints
46
a)
b)
Fig. 62 Sant’Agostino, precast RC industrial building: a) unseating of the transversal beams; b)
falling of precast panels.
Very close to the above mentioned building, another RC structure suffered severe damage (Fig. 63).
The building is infilled with solid clay brick walls. The top of the columns are also made of clay brick
masonry and neither transversal or longitudinal beams are visible. The concrete beam in Fig. 64 is not
reinforced. The details, particularly the connections between structural elements (Fig. 65) are very
unusual even for a building not designed to withstand earthquake loads. The damage at the bottom of
two columns is shown in Fig. 66, while in Fig. 67 it is shown the detachment of a masonry panel at the
back of the building.
Fig. 63 Sant’Agostino, RC industrial building on Strada Statale 225, close to Roversetto.
47
Fig. 64 Sant’Agostino, RC industrial building.
Fig. 65 Sant’Agostino, RC industrial building. Detail of column-roof connection.
Fig. 66 Sant’Agostino, RC industrial building. Damage at the bottom of two columns.
48
Fig. 67 Sant’Agostino, industrial building. Detachment of the masonry panel.
5.2
San Felice sul Panàro (industrial area)
The RC building, hosting a turnery, shown in Fig. 68 and Fig. 69 suffered the collapse of the marquise.
The damage can be attributed to the high length of the cantilever beam and to the vertical component
of the ground motion.
Fig. 68. San Felice sul Panàro. RC building on Strada Provinciale 468, close to via
dell’Agricoltura, collapse of the marquise.
Fig. 69. San Felice sul Panàro. RC building, collapse of the marquise.
49
5.3
Mirandola (industrial area)
Several buildings in the industrial area of Mirandola suffered severe damage or collapse. The factory
in Fig. 70, involved in the development and manufacturing of machines and systems for the healthcare
industry, suffered the tilting of external panels, which were not adequately anchored to the columns.
Details of the connection between columns and panels are shown in Fig. 71. Moreover, part of the roof
collapsed as well where crane was located. However, the inspection of that area was restricted.
Fig. 70. Mirandola. Industrial building on via dell’Industria with via San Faustino. Collapse of
external panels.
Fig. 71. Mirandola. Industrial building. Detail of the connection between columns and panels.
In Fig. 72 the entrance of a collapsed building is shown. The building, built in 2005, hosts a
metallurgical industry. It is made of precast RC members. The columns, arranged along three rows,
are 10 m spaced in the direction parallel to the beams and 20 m spaced in the perpendicular direction.
The beams are simply supported and the roof is made of inclined slabs and sub-vertical skylights (Fig.
73 and Fig. 74).These kind of roofs are considered one of the critical points for the seismic response,
due to the reduced diaphragm stiffness.
It is not clear if connectors between beams and columns are present. As shown by past earthquakes,
the seismic force transmission cannot rely on friction alone (Bonfanti et al 2008b). This is especially
true when the vertical component of the motion is significant. In fact, the combined effect of horizontal
50
displacements and vertical seismic loads can cause the unseating of the beams and the consequent
collapse of the roof. In Fig. 75 the collapsed part of the building, with two internal beams and the roof
slabs fallen, is shown. The column supporting the collapsed beams is not visible under the debris.
Therefore it is not clear whether the damage was caused by the unseating of the beams or by the
initial failure of the column.
In the survived part of the building an out-of-plumb of about 1.4° has been measured.
In Fig. 76, the separation of vertical panels in different locations of the structure is shown.
Very close to this building, two other buildings suffered partial collapse (Fig. 77 and Fig. 78).
Fig. 72. Mirandola. Industrial building on via dell’Industria, close to via San Faustino. Collapse
of the roof.
Fig. 73. Mirandola. Industrial building. Survived part of the building.
51
Fig. 74. Mirandola. Industrial building. Beam-column-slab detail in the part of the survived part
of the building.
Fig. 75. Mirandola. Industrial building. Collapse of the internal beam and of the roof.
Fig. 76. Mirandola. Industrial building. Separation of vertical panels.
52
Fig. 77. Mirandola. Industrial building on via 2 Giugno. Collapse of the roof.
Fig. 78. Mirandola. Partial collapse of a building on via 2 Giugno.
The mechanical factory in Fig. 79 has a quite common configuration, with RC beams in the transversal
direction supported by two rows of RC columns and constrained at the edges by lateral restraint.
Longitudinal beams are also present (Fig. 80a). The span is 17.5 m long and the distance between
columns in the longitudinal direction is equal to 9.8 m. The internal height of the building is equal to 7.5
m. The building suffered only minor damages. In Fig. 80b the damage to a lateral restraint and the
sliding of a beam are shown. Fig. 81 shows a provisional buttress, which was improvised to avoid the
tilting of an external panel.
It is worth noting that the transverse beams of Fig. 79 are oriented approximately along the E-W axis,
while those of the buildings in Fig. 70, Fig. 75, Fig. 77 and Fig. 78 are oriented approximately along
the N-S axis. This seems again a suggestion of a possible polarisation of the ground motion (§ 8).
53
Fig. 79. Mirandola. Precast RC industrial building on via 2 Giugno.
Fig. 80. Mirandola. Precast RC industrial building: a) beam-column joint; b) damage in a lateral
restraint and sliding of the beam.
Fig. 81. Mirandola. Precast RC industrial building. Improvised buttress.
54
6 REINFORCED CONCRETE BUILDINGS
Some reinforced concrete residential and office buildings have been surveyed. The buildings are
masonry infilled RC frames; shear walls structural systems are not frequently adopted in Italy and the
use of RC walls is limited to the elevator and stairwell cores of new buildings or to the retrofitting of
existing one.
The number of storeys of the inspected buildings ranges between 3 and 6.
Considering the surveyed buildings, the level of exterior damage varies between slight and severe, no
cases of collapse have been observed. However, a more accurate damage assessment would require
inspections of the internal parts of the buildings (structural elements, staircases, etc.), that was not
possible to perform during the survey.
The outline of the observed damages is reported in the following.
6.1
San Felice sul Panaro
The building in Fig. 82 suffered severe damages. It is located on Via Campo di Pozzo. The building
seems built very recently.
The damage is mostly concentrated at the ground storey. The failure of columns in Fig. 83 was
probably due to the interaction with the masonry infills. This kind of damage was observed also after
L’Aquila 2009 earthquake (Verderame et al. 2010) and it is due to irregular distributions of the infills.
However, during the 2009 earthquake, the presence of infill walls allowed many structures to survive
with minor or even without structural damage (Decanini et al. 2009).
The failure of several short columns is shown in Fig. 84 and Fig. 85, the disgregation of the concrete
and the buckling of the longitudinal bars can be observed. In the same figures the damage in the
circular cross section columns is noted, anyway the damage is mainly concentrated in the short
columns where the effect of the shear force was higher.
Infills are made of two masonry layers; the internal one is a vertical hollow brick masonry, while the
external layer is a solid brick masonry. Damage to masonry is shown in Fig. 87 and Fig. 86.
Fig. 82. San Felice sul Panaro. Damaged RC building on Via Campo di Pozzo.
55
Fig. 83. San Felice sul Panaro. Damage to ground storey columns.
Fig. 84. San Felice sul Panaro. Damage to ground storey short columns.
56
Fig. 85. San Felice sul Panaro. Damage to ground storey short columns.
57
Fig. 86. San Felice sul Panaro. Damage to external masonry.
Fig. 87. San Felice sul Panaro. Damage to external masonry.
58
Fig. 88. San Felice sul Panaro. Falling of the external layer of masonry.
6.2
Mirandola
Two RC residential buildings located on Via Prampolini were surveyed. The first one (Fig. 89) has six
storeys above ground and an underground parking level. The building consists in two similar blocks. It
is about 18.5 m tall and 37 m wide, the height of the ground storey is about 4 m. The longitudinal span
is equal to 5 m. The cross section dimensions of the external columns of the ground floor are equal to
40 cm x 45 cm. The back side of the building is shown in Fig. 90. At the centre of the front side a RC
core about 3.3 m large (Fig. 91) suffered in-plane damage, as revealed by the typical inclined cracks
(Fig. 92). The second building in Via Prampolini (Fig. 93) has five storeys above ground and is
consists of two blocks connected by a gallery. The building suffered apparently only minor damages to
the external covering (Fig. 94). In Fig. 94. a detail of the support of the RC beam of the gallery, the
support is typical of Gerber’s beams.
Fig. 89. Mirandola. RC residential building on Via Prampolini.
59
Fig. 90. Mirandola. RC residential building. Back side of the building.
Fig. 91. Mirandola. RC residential building. Stairwell core.
Fig. 92. Mirandola. RC residential building. Cracks in RC walls.
60
Fig. 93. Mirandola. RC residential building on Via Prampolini.
Fig. 94. Mirandola. RC residential building.
61
The building in Fig. 95a, located on Via Recchi, has five storey above ground. It suffered exterior
damage, as shown in Fig. 95b, Fig. 96, Fig. 97 and Fig. 98.
a)
b)
Fig. 95. Mirandola. RC residential building on Via Recchi. Damage to covering masonry and to
plaster.
Fig. 96. Mirandola. RC residential building. Damage to plaster.
62
Fig. 97. Mirandola. RC residential building. Damage to plaster.
Fig. 98. Mirandola. RC residential building. Damage to plaster.
63
6.3
Sant’Agostino
No damaged RC buildings were surveyed in Sant’Agostino. Anyway, it interesting to mention that a
RC building located very close to the Town hall, having an irregular configuration in plan and a partial
open ground storey, survived the earthquake without damages (Fig. 99).
Fig. 99. Sant’Agostino. RC irregular building located close to the Town hall.
64
7 LIQUEFACTIONS
The Emilian Po valley has a recent geological formation. It presents a combined slope from South to
North and from West to East, which determines the specific direction of the hydrographic grid, oriented
from SSW to NNE. In the Emilian lowlands fine compact clay soils are more frequent. The water table
is usually very close to the surface, although the water might not be drinkable (Ortolani 1953, pp. 710).
The current route of the Po river is the result of several tremendous floods. Between the 6th century
(Cucca flood) and the 12th century (Ficarolo flood) the river route was that of the Volano river, passing
through Ferrara (Fig. 100). Therefore, the presence of sand is very common in the area.
The area affected by this earthquake has witnessed among the most ancient cases of liquefaction
(Berardi et al 1991). The 1570 Ferrara earthquake and the have induced sinking, generally with tilting,
of buildings erected on sandy deposits. The soil liquefaction affected the Po valley in the vicinity of the
river. In Ferrara some buildings collapsed due to earth sinking. The 1505 Zola Predosa (Bologna
district) and the 1624 Argenta (Ferrara district) earthquake seismic events induced outflow of watersand or water-mud mixtures from cracks in the soil with the formation of small sand volcanoes. This
phenomenon has been observed in Sant'Agostino during the survey here reported.
According to Berardi et al (1991) liquefaction phenomena are missing in epicentral areas of Italian
earthquakes with IO < VIII MCS (or MS < 5.7), while for the same intensity soil liquefaction occurs
consequent to earthquakes with higher epicentral values. Confirmation of this correlation are the 1796
Ferrara (IO = VII MCS) and the Argenta 1898 (IO = VII-VII MCS) earthquakes, when no liquefaction
was observed.
Fig. 100. Scheme of the hydrography of the Ferrara plain. The dot line indicates an isoipsa; the
dashed line indicates the Volano, a previous route of the Po river (Ortolani 1953, fig. 10).
65
During the May 20, 2012 earthquake, soil liquefaction phenomena, with the formation of sand
volcanoes, occurred in several sites: Mirabello (Fig. 101a, b and c), San Carlo (Fig. 101d), San Felice
sul Panàro (Fig. 101a e).
a)
b)
c)
d)
e)
Fig. 101. Sand volcanoes originated by soil liquefaction. a, b, c) Mirabello; d) San Carlo;
e) San Felice sul Panàro (Courtesy of Riccardo Caputo).
66
8 STRONG GROUND MOTION
At the time when this report has been written no strong motion records have been published.
RAN (2012) presents only a table of maximum recorded accelerations a synopsis of which is in Table
3. The same source presents a plot of the three components, without specifying if the signals have
been corrected (Fig. 102). The maximum acceleration has been recorded along the vertical
component, thus confirming the impression derived from damage observations (Fig. 17 and Fig. 69).
However, the N-S component presents a rather large pulse after 5 s from the instrument triggering.
Again this seems is reasonable agreement with what observed in the Town hall of Sant’Agostino (Fig.
9-Fig. 10) and in the plants of Mirandola (Fig. 75 and Fig. 79). The longer period content of the N-S
component is clear in the pseudo-acceleration spectra of Fig. 103. Structures with rocking elements,
such as the stable-haylofts with tall piers weakly connected to the roof, can be sensible to long period
pulses (Sorrentino et al 2006).
Table 3. Maximum accelerations recorded by the National Accelemoteres Network (RAN 2012).
Only values larger than 30.0 cm/s2 are presented. The source does not specify if the records
have been corrected.
Station
Location
District
Epicentral distance
PGA
km
cm/s2
MRN
Mirandola
Modena
13.4
303.3*
NVL
Novellara
Reggio Emilia
39.7
51.07
SRP
Sorbolo
Parma
62.1
40.75
MDC
Medicina
Bologna
55.4
38.89
MDN
Modena
Modena
38.3
36.32
ALF
Alfonsine
Ravenna
76.8
33.06
* Vertical component; maximum horizontal acceleration 258.63 cm/s2.
Fig. 102. Waveforms of the three components recorded by the Mirandola Station.
From the top: Up-Down, N-S, E-W components (RAN 2012). Time in s, acceleration in m/s2.
67
Fig. 103. Pseudo-acceleration spectra (5% critical damping ratio) of the horizontal components
recorded by the Mirandola Station. From left to right: N-S, E-W components (RAN 2012).
Periods in s, acceleration in m/s2. Right plot has been resized to match the vertical axis of the
left plot.
68
Acnowledgements
This work has been partially carried out under the program “Dipartimento di Protezione Civile –
Consorzio RELUIS”, signed on 2009-09-24 (no. 823), Thematic Area 1, Research Line 1, Task 1 and
Line RS 2. The authors acknowledge the valuable contribution of architects Chiara Andreotti (Fig. 44),
Alessandra Marotta (bibliographical researches), Elisabetta Raglione (Fig. 1) and of Professor
Riccardo Caputo, University of Ferrara (Fig. 101).
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