Questions & Answers on EN 81-77:2013 N 1390portailgroupe.afnor.fr/public_espacenormalisation/CENTC10... · (Lift category) Is it possible for one lift in one building to have more

Questions & Answers on EN 81-77:2013 N 1390 October 2014

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During the first months of harmonization of the standard EN 81-77, some questions have been raised to the CEN TC10 WG1 about the proper interpretation and

application of certain clauses of the standard.

To allow everyone to benefit from the knowledge gained from the answers to these questions, CEN TC10 WG1 decided to collect the questions and answers in

this document which has to be considered as a guideline for better understanding of the questions raised on EN 81-77.

It is the intension of CEN TC10 WG1 that this document is freely distributed by CEN TC10 in order to give all interested parties guidance on some Frequently

Asked Questions associated with the implementation of EN 81-77.

Clause Questions/Problem Answers

General

(Lift category)

Is it possible for one lift in one building to have more than one

Acceleration design connected with different level of service (different

travel)?

No, the acceleration design is one and has to be calculated with the hardest

and more conservative conditions (i.e. the maximum height of the building

served and the maximum travel of the lift).

General

(Scope)

Is EN 81-77 also applicable for lifts which are used temporarily during

erection of the building? I don’t mean construction hoists. What I

mean are such lifts which are used during construction as goods

passenger lift and which are slightly modified after finalization of the

building and then used as normal passenger lifts. In specific cases such

lifts could also have increasing number of floor and a machine room

which is moved up with the growing building, sometimes called jump

lift

No, because these temporary lifts are installed in not complete buildings not

in compliance to EN 1998

5.6.1 Does the retainer allowed to be fixed no more than 15° each direction

from the points where the ropes enter and leave the grooves? If yes,

does it make disadvantageous influence of the function of the

retainer?

No, the devices for preventing the ropes from leaving the grooves of traction

sheaves and pulleys shall include one retainer no more than 15° from the

points where the ropes enter and leave the grooves in the direction of the

wrap.


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5.9 Overturning and displacement as a result of the forces imposed on

them including forces generated by the design acceleration.

For info, A17 states:

8.4.2 Machinery and Sheave Beams, Supports, and Foundations

8.4.2.1 Beams and Supports. Overhead beams and supports including

hitch-plate blocking beams shall be anchored to prevent overturning and

displacement as a result of a seismic force acting in a horizontal direction …

Q1: Do we have to consider slack rope on the traction sheave so that

the lift machine is not tensioned by the ropes?

A1: Calculations shall be done in favour of safety, so tension on ropes shall

not be considered

Q2: Do we have to consider dynamic effects due to the design

acceleration which may create larger amplitudes due to resonance? If

yes, which frequencies should be considered?

A2: Dynamic effects shall not be considered: also in EN 1998-1, 4.3.5 -

calculations for "Non-structural elements" are made without take into

account dynamic effects.

5.9 Internal components of controls

Due to the design acceleration internal components of controls may

get loose which may lead to a break down. Do we have to consider

such failures which are not directly addressed in the standard?

We have not directly covered this type of failures because statistical data we

have consulted do not show particular problems about this issue, the major

problem we have seen is the overturning of the control cabinet.

Considering that control cabinet shall be designed and anchored to prevent

overturning and displacement due to the design acceleration, the probability

that internal components of controls get loose can be considered sufficient

low and corrective actions can be neglected.


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5.9 Possible suppliers of seismic detection systems told us that the

triggering level for the primary wave detection is too low and not

feasible. Any shaking in the building due to other reasons (e.g. metro

passing by) would initiate the system.

This value was introduced taking into account the document coming from

Japan describing P wave sensor in the Jea Guide [10 GAL = 0,1 m/s2]

The value introduced in the standard is in line with the sensors available on

the market.

This value may be updated at the next revision of the standard.

[collect other official information from the suppliers]

Q1: Furthermore they didn’t understand how the functional and

interface test according to 5.10.3.4 should be done.

A1: All these electronic devices shall have self-testing functions which result

in a shout down of the seismic switch and the shout down of the seismic

switch shall put the lift into the seismic mode.

Q2: Could you please let me know if these requirements have been

discussed with suppliers of seismic detection systems?

A2: Our driving documents for this value were:

Suppl. A ; Suppl. B and Japan guide (see P-wave sensor)

It is possible to evaluate to modify this value in the next revision of the

standard

5.9 In case of cantilever car slings (rucksack slings) due to the eccentric

centre of gravity of masses of the car and load (see sketch below)

additional forces will be applied on the guide rails which seem not to

be taken into consideration in the formula in Annex D.8. This will

create higher stresses but especially movements of the car which

could lead to collisions. Did WT5 by purpose not consider such

arrangements?

Annex D in EN 81-77 is informative and gives example of calculation taking

into account only G.7.2 Centrally guided and suspended car – of the

EN 81-1/2;

if there is a cantilever car slings is necessary to take into account horizontal

acceleration for the formulas of G.7.3 Eccentrically guided and suspended car

– of EN 81-1/2 in the same way as above.

It is possible evaluate to add also this example in the next revision of the

standard


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5.10.2 In seismic risk zone 2 and greater, failure of mains power supply

(5.10.2) requires to move the car to the next landing in up or down

direction. In seismic risk zone 2 we don't have a seismic switch. This

means we cannot distinguish between an ordinary power cut off and a

power cut off due to seismic activity. In seismic risk zone 3 we have a

seismic switch. The signal of the seismic switch requires us to move

away from the counterweight (5.10.4).

Is it correct that after failure of the mains power supply, the car can be

moved in emergency power in any direction with any speed as long as

we don't have a seismic signal from the seismic detection system?

Yes; to understand better this point, delete the words “In case of seismic

events” at the beginning of point 5.10.2 Behaviour of the lift in case of failure

of the mains power supply - at the next revision of the standard.

5.10.2

5.10.4

Is it correct that after failure of the mains power supply, the car can be

moved in emergency power in any direction with any speed?

1) if there is no activation of the seismic switch, after failure of the mains

power supply, the behaviour of the lift has to comply 5.10.2 (so ever for lifts

in seismic category 2 for those is not required the seismic switch): the car can

be moved in emergency power in any direction with any speed;

2) if there is activation the seismic switch, after failure of the mains power

supply the behaviour of the lift has to comply 5.10.4: the car shall reduce the

speed or stop and proceed to the next possible landing away from the

counterweight or balancing weight with maximum 0,3 m/s car speed


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5.10.3.4 § 5.10.3.4 says “The seismic detection function, including interface

between seismic detector system and lift controller, shall be tested

every 24 h. If a failure is detected during the test or the interface

between the seismic detection system and the lift controller is

interrupted, the lift shall remove itself from normal operation on its

next stop at a landing and park with its doors open”.

Q1: If the interface is interrupted and it is just not during the test, shall

the lift switch into seismic mode (see 5.10.4) or into failure mode (see

5.10.3.4)?

A1: As is written in point 5.10.3.4, if the interface is interrupted and it is just

not during the test, the lift shall remove itself from normal operation on its

next stop at a landing and park with its doors open.

Q2: Does the interface that need automatic system test every 24 h

refer to the interface that sends seismic signal and makes the lift

switch into seismic mode(see 5.10.3.4) , or the interface that sends

failure signal and makes the lift switch into failure mode (see 5.10.4)?

A2: The interface that need automatic system test every 24 h refers to the

interface that sends seismic signal and makes the lift switch into seismic

mode

5.10.4

The lift shall reduce the speed to 0,30 m/s or stop and proceed at this

reduced speed to the next landing.

Q1: Is it acceptable if the next landing is close to continue for some

time with full speed and than approach this landing with normal

deceleration instead of reaching the landing with immediately reduced

speed much later? Would a delay for speed reduction of 3 s be

acceptable according to reaction time specified in 5.10.3.5?

A1: 5.10.3.5 describes the System reaction time.

The system reaction time describes the maximum allowed time period

between the point in time when the seismic wave exceeds the selected

seismic trigger level for the first time and the point in time when the lift

switches into the seismic mode described in 5.10.4. The system reaction time

shall not exceed 3 s. So, is possible to have 3 s of delay from the point in time

when the seismic wave exceeds the selected seismic trigger level for the first

time and the point in time when the lift will reduce the speed to 0,30 m/s.


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5.10.4

(continued)

Q2: Is it acceptable for reducing the speed to initiate an emergency

stop? Some controls are not designed for a controlled speed reduction.

A2: Yes. After the car is stopped it has to proceed to the next possible

landing away from the counterweight or balancing weight with maximum 0,3

m/s car speed

Q3: In case of lifts with an express zone travelling with reduced speed

of 0,3 m/s could take a very long time until a next landing is reached. Is

this requirement also applicable to such lifts or would it be better to

continue for some time in full speed?

A3: This situation was not taken into account by the standard. Due to the

fact that in the standard there aren’t controls of the guides and ropes, the

WT5 considered that the risk to the achievement of the nearest floor was

acceptable only moving the car at low speed.

Table B.1 For Ta in table B.1, “Maximum among fundamental periods of

vibration of the parts of the lift” is difficult to be understood.

Does it mean “the maximum fundamental periods of vibration of the

parts of the lift”?

As defined, Ta is the fundamental vibration period, expressed in seconds,

of the non-structural element (Ta = 0 if the lift does not affect the

fundamental vibration period of the building. In other cases this value

shall be increased according to calculation.

Annex B.1

&

EN 1998-1

The formulae for calculation of the design acceleration in EN 81-77 as

well as EN 1998-1, 4.3.5.2 include the importance factor of the lift γa.

EN 1998-1 includes an additional importance factor for the

building γ1 (see 2.1 ) which may be considered by national

authorities in case of specific buildings which should be designed with

higher resistance to earthquakes. According to clause 3.2.1 the

reference peak ground acceleration agR has to be multiplied with this

importance factor for calculation of the design ground acceleration ag

(ag = γ1 · agR).

This approach has been implemented in Germany and may be in other

countries which leads to the situation that for a safety related lift (e.g.

firefighting lift) in a building with an increased importance factor (e.g.


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Annex B.1

&

EN 1998-1

(continued)

hospital) both importance factors may need to be considered. The

consequence is that a higher design acceleration and in some cases a

higher seismic lift category is applicable as if only one of these

importance factors would have to be considered.

Q1: Is it the intention of EN 81-77 to consider both important factors

or would it be sufficient just to consider one?

A1: EN 81-77 considers both: γa (directly in the formula in EN 81-77) and γI

(indirectly, in the formula of α; α is the ratio of the design ground

acceleration on type A ground, ag, to the acceleration of gravity g (α = ag/g is

non dimensional).

ag is equal to agR times the importance factor γI

(ag =γI.agR) (EN 1998-1, point 3.2.1 (3)).

In the Introduction of EN 81-77 is clearly descript that “It is assumed that

negotiations have been made for each contract between the customer and

the supplier/installer about the design acceleration (ad) to be considered …

The building designer or the lift owner should provide the design

acceleration (ad.) which will be documented in the information for the owner

provided by the installer”.

Q2: In case of only one importance factor need to be considered which

one has to be taken?

A2: Not applicable

Q3: For which kind of lifts should γa be considered (all lifts in a hospital

of only those with a safety related operation, e.g. fire fighting lifts)?

A3: See the definition of γa in EN 1998 where is written:

“4.3.5.3 Importance factors

(1) P For the following non-structural elements the importance factor γa

shall not be less than 1,5:

- anchorage elements of machinery and equipment required for life safety


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Annex B.1

&

EN 1998-1

(continued)

systems;

- tanks and vessels containing toxic or explosive substances considered to be

hazardous to the safety of the general public.

(2) In all other cases the importance factor γa of non-structural elements

may be assumed to be γa = 1,0”.

EN 81-77 has not defined which kind of lifts have to be considered as “life

safety systems”: it depends from National Regulations. Where National

Regulations are not provided, should be considered as safety related lifts for

example those for firefighters, those used for evacuation of people and those

installed in hospitals or other buildings defined for use in emergency

circumstances.

Q4: Which value should be taken for γa in case of safety related lifts?

EN 1998-1 doesn’t specify a value for such lifts and just mentions a

minimum value of 1,5 for other safety related applications?

A4: EN 81-77 doesn’t define which value has to be considered for γa in case

of safety related lifts.

We think that is not our task but it may be taken into account in the next

revision of the standard, if necessary.

Annex D.2 What is the load distribution of QSE? Is it on ¾ of the car area as in load

case for normal operation or is it evenly distributed?

It is evenly distributed according with the fact that for 5.4.1 the rated load is

evenly distributed.

Annex D.7 In addition the question on the height of the centre of gravity of

passengers and loads has not been finally answered at the last WG1

meeting. Is there any new conclusion of WT5?

The position of gravity centre was a point still open last year. At the

beginning we proposed 1,1 m but taking into account anthropometrical

information we can reduce it and assume 0,80 m.

Documents

Questions & Answers on EN 81-77:2013 N 1390portailgroupe.afnor.fr/public_espacenormalisation/CENTC10... · (Lift category) Is it possible for one lift in one building to have more