19-07-2014, 02:46 PM
BASE ISOLATION OF ALLIED JOIN FORCE COMMAND HEADQUARTES NAPLES
BASE ISOLATION OF ALLIED JOIN FORCE COMMAND.pdf (Size: 393.32 KB / Downloads: 45)
ABSTRACT
Seismic protection is a primary task for strategic structures such as military buildings, power
stations, chemical and nuclear plants, hospitals; these structures must survive and be
functioning during emergencies due to strong earthquakes.
In order to guarantee the previous task the seismic isolation technique has been adopted for
the new allied command headquarters located in south Italy near Napoli.
The base isolation seismic protection technique allows the structure to function with no
damage after major earthquakes with a negligible construction costs increase or even cost
reduction in high intensity seismic areas.
This paper describes a general overview of the project and the adopted seismic protection
devices provided by ALGA S.p.A
INTRODUCTION
The main task of an optimal seismic isolation system is to minimize the acceleration into the
structure limiting as much as is possible the relative displacement between the structure and
the ground; in order to reach the previous goals the isolation system must be flexible in order
to reach the target isolation period and capable to dissipate energy to reduce the response.
The strategy to obtain the previous performances for this project a combined base isolation
system composed by high damping rubber bearings (HDRB) and hysteretic dissipators
coupled with free sliding POT bearings has been adopted. The design follows the new Italian
code for earthquake resistance structure design.
The combination of HDRB isolators and hysteretic dampers provides a very effective
seismic protection system coupling the flexibility and the dissipation capacity of the rubber
isolators with the high damping capacity of the hysteretic dampers.
The suitable location in plan of the devices allows the isolated structure to behave as a rigid
STRUCTURE DESCRIPTION
The allied joint force command headquarters consists of different buildings isolated at the
base, the seismic devices provide by ALGA S.p.A. are number 299 high damping rubber
isolators (there are 4 types with different horizontal stiffness and vertical load capacity) and
number 104 slider POT bearings equipped by hysteretic dampers (there are 2 types with
different vertical load capacity).
High damping rubber bearing
The high damping rubber bearing are the most used and kwon isolation devices suitable for
building and bridges. They allow to carry the isolated structure vertical loads, to obtain a
flexible connection between structure and ground to reach the optimal isolation period and to
dissipate energy thanks to a suitable rubber compound. The isolators have a very high
durability and they are designed to be replaceable if required.
The rubber compound used for this project is the Algasism SOFT, the main properties of the
isolators are:
Slider POT bearing with hysteretic dampers
The hysteric devices are obtained by the combination of POT slider bearings to carry the
vertical load and hysteretic steel dissipators for the response in the horizontal plane. The
hysteretic dissipators acts as force control devices: they react as an elastic component up to a
defined displacement and they work with a plastic reaction with predefined maximum
reaction force if the displacement exceeds the elastic one. In this way is possible to limit the
horizontal force in a defined support of the structure and to dissipate a lot of energy in case
of earthquake excitation.
The hysteric dissipators, patented by ALGA S.p.A., have been deeply investigated and
applied in many projects and the design is made according to the theory shown in the paper 1.
The hysteretic dissipators are made of high ductility steel and are capable to allow great
displacement with an high dissipation over 60%.
CONCLUSIONS
The papers showed the seismic protection system for a strategic headquarters of military
forces; the use of the base isolation technique allows the structure to survive being operative
to high intensity earthquakes with return period at least of 475 years according to the Italian
seismic code.