The Anti-seismic Green Lift complying with EN 81-77
According to EN 81.77, lifts must be designed, developed and manufactured taking into account the seismic risk of the area where the lift is to be installed. The standard was harmonized in the first months of 2014.
Specific maps indicate the potential seismic risk areas for each European country.
According to national law, construction companies are committed, for each edifice to be constructed in the respective region, to determine the maximal possible horizontal acceleration (Ah) caused by an earthquake. The criteria of the construction project must be adapted to the seismic risk level of the construction area.
According to the standard EN 81.77, criteria of the lift designing as well have to take into account the value of acceleration (Ah).
It is a matter of common sense to decide upon the installation of an elevator in compliance with the standard EN 81.77 in seismic risk areas, where new constructions already comply with the criteria of seismic risk, namely because a lift may result unusable after an earthquake while the building itself has structurally survived.
Hydraulic systems require less adaption to comply with the regulation EN 81.77. This is why conformity-based hydraulic systems have a competitive advantage in terms of simplicity and pricing, compared to mechanical systems complying with the same standard.
Elevators complying with the standard EN 81.77 present the following features:
- The lift car frame has appropriate protections to exclude the guide shoes dropping out of the guides during an earthquake
- Guides calculation takes into account the entity of inertial forces created by the maximal horizontal acceleration (Ah)
- Car doors are equipped with an additional blocking device with the same characteristics as the landing doors, in order to prevent an unintended opening
- For lifts with travel heights superior to 20 m (typical for electric lifts), the directive requirements are even more severe.
- In case of an earthquake, electric lifts, in contrast to hydraulic lifts, must stop operating and move to the preset floor with reduced speed, opening the doors and stay out of service with open doors. To detect an earthquake, the electric systems must be equipped with special sensors. This is why hydraulic systems can work even during an earthquake.
- In case of power breakdown (which frequently occurs during an earthquake) both electric and hydraulic systems, however, need a battery power supply in order to allow emergency operations.
The anti-seismic systems are especially suited for areas with high seismic risk: in Europe, there are Italy, Greece, Romania, Portugal, Turkey and some areas of Spain and France.
In Italy areas such as Sicily, the Eastern Alps, the cities and towns situated along the central and southern Apennines, from Abruzzo to Calabria, are subject to frequent and intense earthquakes due to the geological structure of our country.
From 2002, Italy has been divided in four seismic areas, based on the classification given by the National Institute of Geophysics and Vulcanology (INGV):
- Area 1 – The most dangerous zone. Very intense earthquakes may occur
- Area 2 – Intense earthquakes possible
- Area 3 – Intense earthquakes possible, but very rarely
- Area 4 – The less dangerous zone. Earthquakes are rare.
HYDRAULIC LIFT SYSTEMS, SYSTEMS WITH LOW EARTHQUAKE VULNERABILITY
Regardless of the compliance with the standard EN 81.77, which states how anti-seismic lifts have to be built, it is important to take into account that hydraulic lifts have a low seismic vulnerability thanks to their structural characteristics.
Regarding recent seismic events in Italy and abroad, several scientific articles published on the most authoritative specialist magazines in the elevator branch1, declare unanimously in relation to earthquake-caused damages of lift systems, that in case of an earthquake, lift systems with hydraulic technology are much less vulnerable than electric lift systems of latest generation, which have counterweights and machinery fixed on top of the lift shaft.
In fact, hydraulic systems
- Don’t have suspended masses of the machinery and counterweight
- The main problem of electric systems during an earthquake was the dropping out of the counterweight from its guides, which caused damages to the shaft walls and sometimes to the car roof as well.
- The machinery (the piston and the power unit) is located on the bottom (in the pit or next to it)
- Unlike electric lifts (with traction), the rescue system of hydraulic lifts does not require an emergency power supply. The rescue system of an electric lift requires an expensive battery pack and the intervention of a highly qualified technician of the installation company. In contrast, hydraulic systems are equipped with a simple and effective rescue system, based on fluid draining (thanks to gravity), by simply pressing the button on the valve block. This is possible even during a total mains failure and without any intervention of a qualified technician (for example a concierge).
As a consequence, as there are fewer downtimes of hydraulic systems caused by seismic events, the elevator might be kept operating, for some reasons, even during or directly after an earthquake.
¹ “Terremoto in Israele” of Ami Lustig – Elevatori Marzo/Aprile 1996 – “Terremoto in Umbria: gli effetti sugli ascensori” of Paolo Tattoli (Engineer and researcher in the ISPESL – National Institute for Occupational Safety and Prevention) – Elevatori Marzo/Aprile 1998 – “Elevator Safety in Seismic Regions” of Dr. F. Celik – LiftReport 2/2006 “Ascensore antisismico” of Lazaros Asvestopoulos & Lazaros Baliktsis – Elevatori Novembre/Dicembre 2007 – “Terremoto” di Giovanni Varisco – Elevatori Maggio/Giugno 2009.