system design and traffic analysis.ppt [ ۮe Ҧ ])

1Only for circulation in lectures

System Design and

Lift Traffic Analysis

IMechE CPD Certificate Course7 Dec, 2016



Ideal Kinematics (1)





j

a

a

v+=

++ JerkAccJerk

for Time





Time taken to complete a journey of distance d with top

speed of v, top acceleration a and top jerk j can be

calculated as follows under three different conditions:

Let’s derive the first relationship


( ) ( )

( )

( ) ( ) ( )

a

V

j

a

V

D

V

a

V

j

VaD

t

a

V

j

Vaddd

V

j

a

j

aVtt

jtt

attvd

tjtavvtt

j

aVttavv

a

V

j

Vattattvdtt

j

a

dt

ddv

j

ajtd

j

at

++=

+−

+=

+=++

=∴

−=−−−+−=

−+=

−=−+=

+−=−+−=

====⇒=

2

3

2

321

2

33

23

2

232323

232

2

1212

22

12121221

2

12

33

111

2

1

22

2 timeTotal

2

1

2

until travelleddistance Total

6

1

62

)2

1( , to From

2

2

1

2

1

2

1 , to From

2

1)( and

6

1

6

1

examplefirst theUse

a

vt

jtv

j

at

=

==

2

2

111 ;

2;



Car Position during Up-peak


Car Position during Down-peak


• door closing time (tc) - period measured from the instant the

car doors start to close until the doors are locked;

• door opening time (to) - period measured from the instant that

the car doors start to open until they are open 800 mm;

• interval (INT) - period between successive car arrivals at the

main terminal with cars loaded to any value;

• performance time (T) - period between the instant the car doors

start to close and the instant that the car doors are open 800

mm at the next adjacent floor (Note: sometimes called ‘door-

to-door’ time);

Terminology


• passenger arrival rate - rate at which passengers arrive for

service by a lift system (Note: often given as a percentage of a

building’s population arriving within a 5-minute period);

• passenger average journey time (AJT) - average period of time

from when a passenger either registers a landing call, or joins a

queue, until the passenger alights at the destination floor (Note:

a passenger is deemed to have alighted, when any passenger

detection device is interrupted or the passenger physically

crosses the door sills);


• passenger average time to destination (ATTD) - average period

of time from when a passenger either registers a landing call,

or joins a queue, until the responding lift begins to open its

doors at the destination floor;

• passenger average transfer time (tp) - average period of time

for a single passenger to enter or leave a lift car;

• passenger average transit time (ATT) - average period of time

from when a responding lift begins to open its doors at the

boarding floor until the doors begin to open again at the

destination floor (Note: the passenger transit time commences,

if the responding lift doors are open, when a passenger arrives);


• passenger average waiting time (AWT) - average period of time

from when a passenger either registers a landing call, or joins a

queue, until the responding lift begins to open its doors at the

boarding floor;

• Notes:

• (1) The passenger waiting time continues if a passenger does

not enter the responding lift, e.g. because the lift is full.

• (2) The passenger waiting time is zero if the responding lift

doors are open when a passenger arrives.

• (3) If a passenger may register a destination call before

arriving at the lift lobby, waiting time may be divided into two

components: walking time (time to reach the lobby) and

standing time (time waiting in the lobby).

• single floor flight time (tf(1)) - period of time measured from

the instant that the car doors are locked until the lift is level at

the next adjacent floor;


• up-peak handling capacity (UPPHC) - number of passengers

that a lift system can theoretically transport during the up-peak

traffic condition with a car occupancy of 80% of the actual

capacity (Note: this is calculated by determining the number of

trips made by the lifts, which occur over the worst five minute

(300 second) period and then multiplying it by the average

number of passengers (P) carried in that five minutes;

• up-peak interval (UPPINT) - average time between successive

car arrivals at the main terminal (or other defined) floor with

cars assumed to be loaded to 80% of actual capacity during the

up-peak traffic condition.


Conventional

Belief :

If a Lift Group

can handle Up-

peak, normally

30 minutes, at

15% / 5 min, it

can handle any

traffic.



CIBSE Guide D 2015


RTT – the

most

important

parameter

in Lift

Traffic

Analysis



adocsdf

vs

tttttT

tTt

−+++=

−

)1(

tochanged is

2015, D Guide CIBSEIn

• Performance time (T) - period between the instant

the car doors start to close and the instant that the car

doors are 800 mm open at the next adjacent floor;

Note: Sometimes called ‘door-to-door’ time.

• tad - Advance door opening time (s).

• tsd - Start delay time (s).

• to – Door opening time (s).

• tc – Door closing time (s).


CIBSE Guide D 2015


Assumptions of most basic equation for the

RTT:1. Equal floor populations in the derivation of H and S. Equal

floor heights.

2. Passenger choices of floors are independent of each other

(this affects the derivation of H and S).

3. Constant passenger arrival rate. It is assumed that the arrival

process of passengers is not random and that passengers

arrive in a uniform manner with equal time spacing between

them. In reality passengers arrive randomly in a process that

is best represented by a Poisson arrival process.

4. An important assumption made in the derivation of the round

trip time equation is that the top speed is attained in one floor

journey. This is not correct in many cases where the speed is

above 2.5 m/s.

5. Both traffic profile and supervisory control are ideal.


Assumptions of basic equation for the RTT:5. Only one passenger is boarding or alighting at the same time.

6. Only type of traffic present is the incoming traffic (up peak

traffic).

7. Equal floor heights have been assumed.

8. Doors starts closing immediately after the last passenger has

boarded or alighted. In reality there will be delay depending

on the timer controlling the door operation, and depending on

whether other passengers use the door close button.

9. Passengers enter the building from one single entrance. In

reality many buildings have underground car parks or

different level street entrances.

10. No door re-openings have been assumed.

11. It has been assumed that all lifts in the same group serve all

floors and that any passenger regardless of his/her destination

can board any available lift.


Questions asked:• Do passengers arrive uniformly in time?

• Can the rated load be used to determine the number of

passengers a lift car can accommodate?

• Why should lifts load to 80% of probable capacity?

• What happens if all floors are not equally populated?

• What happens if the rated speed is not reached in a single floor

jump and if the interfloor heights are not equal?

• What are landing and car call dwell times?

• What are lobby loading times?

• Is the traffic controller ideal?

• Are all the adjustments described above necessary?

• How can the calculation deal with transfer floors?

• How does lift function, building form and building function

affect the calculations?

• Will the RTT value obtained by calculation be the same as that

obtained by simulation?


P = 0.8 CC

For Equal Demand (Up-Peak)

Prob. at least a stop at a

particular floor =


For Equal Demand (Up-Peak)

pppP

N

i

iNN

Ni

=

+−

−−

−

=+

1

11

1

11

11

floor th ... 1)th,(at car theleavespassenger no Prob.

L

Nobody leaves the car

at a particular floor

Prob. that i is the highest floor = prob. not higher than

ith floor – prob. not higher than (i-1)th floor

∑=

−−

=

N

i

pp

N

i

N

iiH

1

1


For Down-Peak


For Unequal Demand (Up-Peak)

∑∑−=

−−=

−=

−=

N

i

p

i

i

p

i

p

i

U

UU

N

NN

U

UUS

U

UUi

1

N

1

-1

-1 floor th at the stopscar that Prob.

∑=

+

+−

=

++=

−−

−−

−

−−

−

=

i

j

p

j

p

i

p

i

i

p

N

NN

p

N

U

U

U

UU

UU

UU

UU

UUU

U

UU

i

1

1

2

11

floor th nhigher tha no stopsCar

L

L

LL

∑ ∑

∑ ∑∑

−

= =

=

−

==

−=

−

=

1

1 1

1

1

11

N

i

pi

j

j

i

j

i

j

p

j

p

jN

i

U

UN

U

U

U

UiH


For Interfloor Flight Time Variations and Unequal

Interfloor Distances

• Determine H/S to give average interfloor jump (1).

• Determine height of building (dH) to floor H and divide by H

to give average interfloor height (2).

• Multiply the above two (1) x (2) to give average distance

travelled (3).

• Look up on a manufacturer’s time/distance graph the time (4)

to travel the distance (3) found above.

• Calculate the assumed time (5) to travel the distance

calculated in (3).

• Calculate the difference between time obtained in (4) and (5).

• Add the time obtained to ts when calculating the RTT.


Some Lost Times

• First two terms of RTT equation are idealized.

• Third term depends on human behaviour.

• A passenger may hold a door whilst finishing a conversation.

• A tea trolley may be loaded thereby reducing the car capacity.

• A person may enter additional car calls with no passenger.

• Difficult to quantify these disruptions, say add 10% to RTT.

• Some lift control systems cause a lift to remain at the main terminal

for a fixed time interval (dispatch interval).

• Some hold a lift at the main terminal for a fixed time for the

registration of first car call (loading interval).

• If these two intervals < time to load 80% of rated car capacity, no

effect.

• Some hold a lift at the main terminal for (nextcar).

• Some cause lift doors to be held open for a fixed time at each stop

(door holding interval or door dwell time) to allow movement of

passengers in and out without colliding the doors.

• But if door swell time is long, put tp = 0.


Determination of Passenger Demand

• Quantity of Service

• Quality of Service

• Passenger Data Sets (no. of passengers boarding from

and alighting at specific floors; traffic mode –

unidirectional or multidirectional; transfer time;

passenger actions)

• Up-peak Traffic (passengers only load at lobby;

passengers never alight at lobby; unidirectional; short

transfer time; little opportunity of misbehavior)

• Purpose of Building (residential; commercial;

institutional)

• 3 main types of commercial tenancy (diversified; mixed;

single)


Geographical factors

• Lift sizing based on US and UK values.

• Asia/Pacific people are smaller.

• Scandinavians are taller.

• Europeans from Latin countries smaller than

North Europeans.

• 90 years ago, a male assumed to weigh 68 kg

with an area of 0.19 m2.

• By 1971, area became 0.21 m2 and weight

became 75 kg.

• Same ratio: 360 kg/m2.


Determination of Passenger Demand• Main Terminal Population (80%-85% of building population)

• Usable Area (rentable area = 90%-95% of gross area; usable area =

75%-80% of gross area)

• Arrival rate (multiple)

= 11%-15% for regular;

17% for prestige

• Arrival rate (single) =

15% for regular; 17-

25% for prestige

• Interval < 20 s for

excellent; < 25 s for

good; > 50 s for

unacceptable


Parameters measuring

Traffic Performance

• Average Waiting Time

• Average Travel Time


AJT

= AWT + ATT < 90s

Under Up-peak

Condition

AWT =

[0.4 + (1.8P/CC – 0.77)2 ]

UPPINT for car loads from

50% to 80%; or

AWT = 0.4 UPPINT

for car loads less than 50%


Average (Lift) System Response Time (ASRT)

• AWT calculated by adding all individual waiting times

together and dividing by their number

• Difficult to measure

• ASRT is the period of time that it takes for a group of lifts

to respond to the first registered landing call at a floor

• SRT is measured from the time the first passenger at a floor

registers a landing call until the car doors of the lift

servicing that call has opened its doors to a width of 800

mm


AJT = 0.5 (H tv + S ts + 3 P tp ) + AWT Barney 1992

AJT = 0.5 (H tv + S ts + 2 P tp ) + AWT Barney 2002 –

Calculate ATT to the midpoint of the local travel for any group

of lifts, i.e. travel for a distance of H/2 with the number of stops

being S/2 and a transfer of P/2 passengers boarding and P/2

passengers alighting.

PtS

t)(SS

HtATT psv +

+++=

2

11

2

Equations for ATT under Up-peak Condition


An Example by Conventional Hand Calculation

• A building, of no great prestige, with N = 10

• GFA/floor = 1500 m2 ; df = 3.3 m ; tp = 1.2 s

• 80% usable area = 1200 m2

• 10 m2 per person from table, i.e. 120 persons/floor; 1200 total

• 80% daily attendance, i.e. 960 persons

• 15% up-peak arrival rate in 5 min from table, i.e. 144 persons

• Interval assumed 30 s, from table

• To design a lift system to handle 144 persons in 5 min with an

interval of 30 s


• A building, of no great prestige, with N = 10

• GFA/floor = 1500 m2 ; df = 3.3 m ; tp = 1.2 s

• To handle 144 persons in 5 min with an interval of 30 s

• 80% car occupancy

• Capacity = 14.4 per trip / 0.8 = 18 persons at least, pick 21

• Select rated speed = 1.6 m/s

• Select 1100 mm centre opening; to = 0.8 s; tc = 3 s; tf(1) = 6 s

• H = 9.8; S = 8.3 ; P = 21 x 0.8 = 16.8; tv = 3.3/1.6 = 2.1

• ts = 0.8 + 3 + 6 – 2.1 = 7.7 s

• RTT = 2 x 9.8 x 2.1 + (8.3+1) x 7.7 + 2 x 16.8 x 1.2 = 153.1

• Need 5 cars; UPPINT = 153.1 / 5 = 30.6

• UPPHC = (300 x 16.8) / 30.6 = 165 persons / 5-min


END

system design and traffic analysis.ppt [ ۮe Ҧ ])

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