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POST-EARTHQUAKE INTERVENTIONS :PREVENTION AND SAFETY TECHNIQUES
FACTORY BUILDINGS:
THE MAIN FEATURES, THE
Author: Anna Marzo
Working group: Alessandra GugliandoloMaurizio Indirli
Giuseppe MarghellaMaria-Anna Segreto
INEFFICIENCIES AND THE
SUITABLE INTERVENTIONS
ACCORDING TO THE EUROPEAN
REGULATIONS
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ENEA ACTIVITIES FOR SEISMIC PROTECTION
Supporting the Italian Civil Protection
L’Aquila earthquake (2009) - 6.3 Richter
damage/safety evaluation for cultural heritage
Emilia Romagna earthquake (2012) – 5.9 Richter
damage/safety evaluation for several typologies of
constructions
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ENEA ACTIVITIES FOR SEISMIC PROTECTION
Research activity: innovative seismic protection devices
SEISMIC ISOLATION OF VALUABLE OBJECTS
T
ERCOLANO SHIP
Springs and hydraulic system
BASE ISOLATION OF BUILDINGS
O E
U
S P A C E P R O J E
Rolling element
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EUROPEAN SEISMIC MAPS
Distribution of the seismicity on the European territory
form the highest (red) to the lowest (bleu) seismic areas
The reduction of the seismicity from south to north due to the plates localization. The more seismic countries are located along the Italy is located on the plate limitation
The earthquakes occur along the plate perimeter, when they move
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FACTORY BUILDINGS: Surveyed multi storey typologies
Two levels
Alveolar panels
Notes:
Precasted buildings
Realization: 1960-2000
Reinfoced Prestressed
Concrete
Two-three levels
Precasted slab
ree eve s
Tile TT
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Horizontal precast panels
FACTORY BUILDINGS : Cladding typologies
Vertical precast panels Notes:
Precasted vertical/horizontal panels
Panels-structure connections realized by steel anchorages
Regular opening
Claddings façades are very commonin industrial buildings. In these cases
it is very important to check the
fixing system to the buildingstructure taking into account thevertical force distributed on thesingle panel.The seismic action may beevaluated by considering a force
applied to the center of gravity of the
Brick masonry claddings
Notes:
Traditional brick masonry
claddings
Cladding fill the empties between the structures
Traditional mortar
element.
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Connections among structural and completion elements
FACTORY BUILDINGS: Connections
Ad omega
CONNECTION TYPOLOGIES
Tiles simply supported by the beams
Beams simply supported by the pillars
Pillars fixed to foundation
Cladding panels connected to the structures by means of steel brackets
Beam
Mortar or rubber layer
Pillars
Beam
Pillar
Fork
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Connections among structural and completion elements
FACTORY BUILDINGS: Connection cladding-beam and cover-beam
Ad omega CONNECTION TYPOLOGIES
✔Tiles simply supported by the beams
✔Beams simply supported by the pillars
✔ Pillars fixed to foundation
✔Cladding panels connected to the structures by means of steel brackets
weldingL shapedplate
ScrewΦ16 with washer
and nut
steel ancor plate
L SHAPED PLATE 130x65x10L=75mm
hole Φ17
buttonhole
steel ancor plate
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FACTORY BUILDINGS: Current rules
UNI ENV 1992-1-3 30-09-1995. Eurocode 2. Design of concrete structures . General rules and rules forbuildings
Connections
• Damage due to cyclic deformation in plastic field should be considered; the strength design of the connections should be reduced in order to
taken into account of seismic stress, if it is required;
•in case of panel-bearing structures both r.c. and welded joints effectiveness should be experimentally tested;
•beam-pillar connections should guarantee the matching of both vertical and horizontal displacements and the stress should be transferred by
means of mechanical devices;•it is consented the realization of a sliding support at one end of the beam, but the sliding surface should be more extended then the seismic
displacement required;
•in case of connection between non monolithic parts ad hoc design criteria should be considered (three types are possible);
•Pillar-horizontal elements connection should be fix (rigid or elastic) when the pillars are isostatic elements;
•In general, the connections between both structural and completion elements should be guarantee the transmission of both static and seismic
The main requirements for structural elements and connections
UNI ENV 1998-1-4 31-10-1999. Eurocodice 8 - Design of structures for earthquake resistance. Part 1: General
rules, seismic actions and rules for building.
stress in the safe side, therefore simply friction connections are not permitted.
Beams
•The beam width should be greater then 20 cm, while for small beams (namely “flat beams”) it should not exceed the pillar width, increased on
both sides by the half height of the same beam;
•The ratio between transversal dimension of the beam (width/height) should not exceed 0.25;
•Axes of both beam and pillars supported (namely “in false”) should be aligned; in addition the beams should have at least two supports (pillars or
shell); the shell can not be supported on beam or plate “in false”;
•The critic zones are extended to 1 or 1,5 times the beam height for slow ductility class or high ductility class, respectively. In case of beam which
supports “in false” pillars the critic zone should be extended for two times of the beam high, starting from the beam-pillar node in all cases.
Pillars
•The pillar transversal section should be grater then 25 cm, while for small beams it should not exceed the pillar width, increased on both sides by
the half height of the same beam.
•In addition, the codes provide same limitation about reinforcement, which are evaluated case by case.
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Buildings with double inclined beams: Lack of the support and collapse of the cover
FACTORY BUILDINGS: Damages surveyed after the sesmic events(may 20th and 29th)
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Lack of support due to the break of the upper forks of the pillars: collapse of the cover
FACTORY BUILDINGS: Damages observed after the sesmic eventsin Emilia Romagna region (May 20th and 29th, 2012)
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Collapse of the cladding panels
FACTORY BUILDINGS: Damages observed after the sesmic events inEmilia Romagna region (May 20th and 29th, 2012)
Connession panel-pillar
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Collapse of the beam: separation of the two composing parts of the 2-body beam
FACTORY BUILDINGS: Damages observed after the sesmic events inEmilia Romagna region (May 20th and 29th, 2012)
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Mixed precast reinforced concrete structures: Shear collapse of the masonry pears
FACTORY BUILDINGS: Damages observed after the sesmic events inEmilia Romagna region (May 20th and 29th, 2012)
Beneficial effects of the metallic ties
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FACTORY BUILDINGS: Damages observed after the sesmic events inEmilia Romagna region (May 20th and 29th, 2012)
THE IMPORTANCE OF THE CONSTRUCTIVE DETAILS: These building are not collapsed thanks to the realization of good connections
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FACTORY BUILDINGS: Reduction of the seismic vulnerability
PILLAR-BEAM
- Evaluation of the damages and of their
mechanisms;
- Evaluation of mechanical properties of the
constitutive materials;
- Evaluation and upgrading of stiffness,
strength and ductility against the design
stresses, by considering the suitable static
scheme (usually cantilever);
-
CONNECTIONS
Laboratorio LAERTE Anna Marzo ENEA - UNITA' UTSISM
FOUNDATION - Assessment of any damage and identification of its mechanisms;
- Knowledge of the type of soil for the characterization of the seismic
response with appropriate investigations (spreading seismic);
- Evaluation of the possibility of differentiated sags;
- Stiffness against rotation, such as to guarantee the joint at the base
of the pillars;
- Resistance against lateral actions, transmitted from the pillar (in thecontext of a hierarchy of resistors, the resistance of this element
should be oversized with respect to the superstructure)
beams and roof elements must not introduce significant bending
moments at the end of the connected elements since they are not
sized to absorb it;
-Simple supports must be transformed into hinges, in order to not
change the original static scheme;
- Sliding may also be permitted, but it should be, in any case,
limited by properly-sized restraints.
- Torsion rotation of the beams must be tackled ;
- The strength hierarchy should be considered whendimensioning the connections (links ductile and weaker than
the connected elements);
- The used fasteners (typically wall plugs) shall be more resistant
than the connecting devices set by them.
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Beam
FACTORY BUILDINGS: Reduction of the seismic vulnerability
It has been providing some suggestions for professional engineers, suitable to evaluate quickly seismic safety and set upreasonable anti-seismic strengthening interventions for simple-storey. Reinforced prestressed precast concrete construction,taking into account both the safeguard of human life and the recovery of serviceability conditions, saving machinery andequipment.
Guideline for both local and global interventions on factory buildings developed by Eurocode.
SLIDING SUPPORTS • Evaluation of the section features and of the related forks (reinforcement, transversal
sections, and so on ;• Realization of constraint elements, when any fork is present
Pillar
Fork
Beam
Pillar
Sliding plain(teflon)
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FACTORY BUILDINGS: Reduction of the seismic vulnerability
CONNECTIONS BETWEEN STRUCTURAL ELEMENTS
CONNECTION WITH COLD FORMED PROFILES
Beam
Pillar
• Evaluation of the section features and of the related forks (reinforcement,
transversal sections, etc)
• Any substitution of the forks with other support system in order to avoid the
beam overturning
Pre-existing hole
Steel pin
Supporting steel plate
Ancor steel bars
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FOUNDATIONS
FACTORY BUILDINGS: Reduction of the seismic vulnerability
Ringing with concrete
Forks for both bars and brackets
connectionBars which connect the
concrete ring
Brackets
Requirements for foundation elements:
• Adequate stiffness against rotation, sufficient to ensure the joint at the base of the pillars.
• Adequate resistance against lateral actions transmitted from the pillar
Intervention’s category
• Connecting the plinth with the industrial floor
Improvement of the mechanical
properties of the soil
Connection steel bar
Additional concrete
cast
Industrial floor
Hole in the industrial
floorInjection with water-
concrete mixture