Static loading

PANELS
The permissible deflection is 1/300 of the length of a panel, i.e. 2mm for 600 x 600 mm panel.
Uniform distributed load:
This type of loading, which is still currently referred to, is not representative of the mechanical performance of an access floor.
However, the admissible uniform distributed load is admitted to be 5 times the measured centre of edge point load.
According to the types of panel and framework, the distributed load varies from 10 000 to 30 000 N/m².

Concentrated load:
It is applied by the way of a 25 x 25 mm indentor:
a) either at the centre of a panel.
b) or at the centre of one edge.
With very few exceptions, this type of loading is the most unfavorable.

Safety factor - failure load
The failure load applied on the weakest point of the panel must be at least equal to 2.5 times the edge point load.

PEDESTALS
a) Concentrated load:
The pedestal is progressively loaded, by way of a 40 x 40 mm plate, until it reaches the buckling point. See the graphs on Pedestal page for permissible loads.

b) Eccentric load:
The 40 x 40 mm plate is moved out of centre in order to simulate the edge of a panel.
The loading before buckling must be at least equal to twice the edge point load.

Coverings
Wear and punching classification
The reports No. 1504 dated may, 1978 and No. 2183 dated September, 1987 have set up the UPEC classification for non-industrial applications.
In this document:
U = Wear
P = Punching
E = Waterproofness
C = Chemical
All these characteristics have rising indexes from 0 to 5 according to the required degree of resistance.
The reports No. 1716 and 1717 dated July, 1981 concerning PVC coverings and report No. 2288 dated October, 1988 concerning textile coverings defined test methods to determine coverings' indexes for the above U-P-E-C characteristics.
So, a U3P2E2C1 classified room, for example, can only be equipped with a covering which has characteristc indexes identical or superior to those of the room, in ou example U3 minimum, P2 minimum, E2 minimum, C1 minimum.
Within the framework of the European regulations, UEATC (European Union of Agrement) has published instructions for the agrement of PVC floor coverings. These instructions appear in the CSTB report No. 2182 dated September, 1984.
They recapitulate the classification of rooms and coverings. The used characteristics are GW:
G = Wear + Punching (index 1 to 5)
W = Waterproofness
Tables enable the connection between G and U.P.
Please note that the UP or G classifications are available for a covering bonded on a continuous and rigid surface and cannot be valid for the same covering bonded on raised floors.
The vertical warpings due to tolerances of the panels' thickness and deflections under loading can provoke partial deterioration of trim edges when moving furniture or castor chairs.

Electrical characteristics

A. ELECTROSTATIC PROPERTIES
The ability of a covering to accumulate electrostatic loads and its ability to eliminate these loads quickly are essential for the antistatic properties of an access floor. The measurement of the transversal resistivity-Rt enables the estimation of the ability to eliminate the electrostatic loads.
The used method has been set up by the Standard NFP 62-001 part C issued from the Standard NFPA 99. The CEN-ELEC (European Committee for Standardisation for Electricity) has set up Working groups in order to harmonise the characteristics of classifications and the measuring methods.
The following classifications and definitions can be used until the development of future European Standards: Physiological antistatic: Electrostatic charging potential < 2.5 KV and Rt < 10¹² Ohms.
Dissipative: Rt between 5 x 10⁵ and 10⁸ ohms
Electrostatic conductive: Rt between 10⁴ and 5 x 10⁵ ohms - Discharge time < 1 second.

B. INSULATION PROPERTIES
For some applications, insulating access floors are required.

EQUIPONTENTIAL BONDING AND EARTHING
It has 2 purposes:

• To enable an easy electrostatic discharge. The purpose is easily achieved.
• To ensure peoples security by linking the metallic parts that constitute the access flooring. The second purpose is made difficult by the lack of definition concerning the metallic earthing.

The equipotential bonding is automatically achieved by the contact between the metallic parts of the framework and the metallic bottom of the panels. The electrostatic conductive joints are obstacles to an efficient equipotential bonding.
The equipotential bonding is completed by copper strap network connecting some pedestals to each other. Finally, this network is connected to the earthing by companies in charge with electricity.

Fire protection.

The regulations for access flooring refer to:

• the reaction in front of fire.
• the partitioning of the plenum.
• the calorific potential.

They vary according to the use of the rooms and the classification of the building inside which the access floors are installed.

REACTION IN FRONT OF FIRE
For the moment, there is no uniform classification method in Europe. In France, the decree dated June 30th, 1983 defines 5 classes for the materials: M0, M1, M2, M3, M4.
The test method used is the radiation test. The tested side is the bottom of the panel. The classification of the superior part of the panel is the same as for the covering.

PARTITIONING OF THE PLENUM
Plenum dividers made of M0 materials or fireproof partitions, with a 1/4 hour flame protection, can be provided if required by regulation.
Every partitioned area has a maximum surface of 300m² and a maximum length of 30 meters.

Acoustic insulation
Please note that acoustic insulation tests for access floors do not exist in Europe and elsewhere. Studies concerning this subject have been carried out by the TC 126 group with CEN (European Committee for Standardization), since 1992. The results of the TC 126 works and its applications by way of a CEN Standard will require several years.
By that time, the figures provided by some manufacturers, and obtained by way of different methods and indexes cannot be compared.
The testing method used for suspended ceilings, but reversed in the case of raised floors, could be used as a basis for TC 126 studies.
In that case the acoustic insulation would be then measured between 2 adjacent rooms equipped with access floors and seperated by a partition.
Under such conditions, our access floors can reach airborn sound insulation values from 38 to 44 dbA, as stated on individual technical sheets of our panels. The insulation to impact sound depends mainly on the type of coverings bonded on the panels. The textile coverings are most efficent.

Requirement for rooms to be installed with access flooring
Conditions:

• Not to be exposed to bad weather
• Rooms must be equipped with outside glazing
• Concrete slab and plaster walls must be dry.
• Not to be exposed to rehumidification risks.
• To get a concrete floor conform to article 5.2.2 of DTU 21:the raw concrete is not allowed
• Not to be encumbered with materials or tools and get a dry and clean concrete.
• Free of any other trades.
• All rooms adjacent to the access floor must have the same floor height.
• The ambient temperature of the rooms where the access floor is to be installed should be kept between 5^oC and 24^oC and the relative humidity between 45% and 70%. If the temperature is above 24^oC (but never above 30^oC) the relative humidity should not be over 50%. The subfloor temperature should not be below 5^oC.
• No water or any other liquid should be spread under or on top of the access floor.

Seismic zones
The decree No. 91.461 dated May, 14th 1991 defines the building classes, and classifies the French regions in seismicity zones.
For normal risk buildings classified C and D and within the zones II and III special steps must be taken, i.e:

• Every pedestal must be fixed to the concrete by way of adhesive or mechanical process.
• In the case of plenum heights superior to 250 mm the pedestal must lay on stringers which are mechanically fixed to the pedestals.

Access floor levelling

FINISHED HEIGHT:
An adjustment inferior or equal to 5 mm is possible compared to the theorical finished height.

HORIZONTALITY:
Within a 5 m x 5 m area, the difference in horizontality must not exceed 3 mm.
Within the total surface of the access floor, the difference must not exceed 10 mm.

FLATNESS:
Along a 2 metre long profile, the level variation must not exceed 2 mm. The tolerances of manufacturing come in addition to this figure.

VERTICAL WARPING BETWEEN PANELS:
The vertical warping between the upper part of two adjacent panels must not exceed 1mm. The panels peripheral edgings are not taken into account.

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