Special Situations and their effect on the Round Trip Time Equation 8.1 INTRODUCTION
This chapter indicates how the round trip time equation might need to be changed to deal with a number of special situations. Such situations will be discussed with respect to considerations by lift function, building form and building function. For example a firefighting lift (lift function) installed in a tall building (building form) used as a hospital (building function). The target equation is Equation (4.11):
(4.11) 8.2 CONSIDERATION BY LIFT FUNCTIONS
8.2.1 Shuttle Lifts (with sky lobbies)
Many tall buildings are divided into several zones: low zone, mid zone, high zone, etc., with service direct from the main terminal floor, situated at ground level. These are called “local” zones. This becomes impractical with very tall buildings of 70 stories or more and shuttle lifts are employed
(Schroeder, 1989b) to take passengers from the ground level main lobby to a “sky lobby” (Browne and Kelly, 1968). Passengers disembark at the sky lobby and then take the local lifts to their final
destination. Service is then provided to further low, mid, high zones, etc. using the sky lobby as an upper main terminal floor. The advantage is that the core efficiency is improved (Fortune, 1995, 1996), as the hoistways extend the whole height of the building (except for the intervening equipment spaces) and occupy the same hoistway “footprint”. Sometimes passengers travel down from the sky lobby as well as up (Fortune, 1986, 1990). Most shuttle lifts are single deck, but there are a number of double deck installations. Schroeder (1989a) defines four basic sky lobby configurations:
1. Single deck shuttles, single deck locals, eg: World Trade Center. 2. Double deck shuttles, single deck locals, eg: Sears Tower. 3. Double deck shuttles, double deck locals, eg: Petronas Towers. 4. Single deck shuttles, single deck top/down locals, eg: none.
Configuration 4 would be difficult to engineer, as offset lobbies would be required. A configuration Schroeder did not consider should be added:
5. Double deck shuttles, single deck top/down locals, eg: UOB Plaza. Examples of these configurations are discussed in Section 8.3.2.
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Shuttle lifts are sometimes employed over shorter travel distances, such as from car parks to a main terminal and at underground railway stations, or very long distances to observation platforms. Generally shuttle lifts serve between two stops only, hence the term “shuttle”, but sometimes serve three stops, ie: with two1 sky lobbies.
Shuttle lifts are usually quite large and fast and provide an excellent service to the sky lobby. Their main disadvantage is that the passengers must change lifts mid journey, hence increasing their total journey time. When a traffic design involves a change of lift, the two journey times are best quoted separately. There is no need to modify Equation (4.11). However, note that the value for tv will be for the travel between the stopping floors. This could be 200 m or more.2
As the cars are generally large (<2000 kg) and will fill more fully than is usual for a group of lifts, the passenger transfer times (tp) when loading and unloading will be more efficient and smaller. The
reasons for this is that waiting passengers are “batched” outside a shuttle entrance expecting its arrival; the lift doors will be 1100 mm or more wide; and there may be through cars, allowing the separation of the incoming and outgoing passengers. Example 5.6 indicated that for a 16 person lift the total
passenger transfer time for 12.8 passengers, each requiring a tp of 1.2 s, was 11.3 s, ie: tp is less than one second on average. For a 5000 kg lift, where it might be possible for 44 persons to be
accommodated, the total passenger transfer could be 30.0 s, ie: the average tp becomes 0.7 s.
The traffic design of a shuttle lift can use Equation (4.11), but as both H and S are known (usually “1”). then Equation (8.1) can be proposed:
(8.1) where T is the performance time as defined by Definition 4.23.
Example 8.1
Consider a shuttle lift transporting passengers from a main terminal to a single sky lobby (N=1) during uppeak with the following data:
Thus:
(from discussion above). Using Equation (4.11):
1 Sears Tower, Chicago, USA.
2 Petronas Towers, Kuala Lumpur, Malaysia.
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Using Equation (8.1):
Such a shuttle lift would have a 5-minute handling capacity of nearly 100 persons. When a shuttle lift is serving a balanced two way traffic situation, then the lifts would fill fully at each lobby and the round trip time would increase by a further 2Ptp seconds. If there were two sky lobbies then the first term of Equation (8.1) would be 3T, etc.
The number of shuttle lifts that are installed world wide is not large. Their traffic design is relatively simple, but their application in a building requires expert consideration.
8.2.2 Double Decker Lifts
Double deck lifts comprise two passenger cars one above the other connected to one suspension/drive system. The upper and lower decks can thus serve two adjacent floors simultaneously. During peak periods the decks are arranged to serve “even” and “odd” floors respectively, with passengers guided into the appropriate deck for their destination. Special arrangements are made at the lobby for
passengers to walk up/down a half flight of stairs/escalators to reach the lower or upper main lobby. Double deck lifts, which are common in the USA and elsewhere, but unusual in Europe, are used in very tall buildings (see Section 8.3.2). Fortune (1996) indicated 465 double deck lifts in 34 buildings across the world.
Table 8.1 World wide location of double deck lifts
Location Number Buildings
North America 317 17 Singapore 55 5 Malaysia 29 1 Japan 17 3 Spain 15 3 Taiwan 12 1 Australia 11 1 England 4 1 Hong Kong 4 1 China 1 1 Total 465 34
There are many advantages and disadvantages to double deck operation (Fortune 1996) and special care has to be taken with the lobby arrangements (see Section 8.3.5). One advantage for double deck lifts is that the “hoistway” handling capacity is improved, as effectively there are two lifts in each shaft. A disadvantage for passengers during off peak periods is when one deck may stop for a call with no coincident landing, or car call, required in the other deck. Fortune (1996) describes special control systems that are available during off peak periods, such as skip/stop, trailing deck and restricted deck service.
Fortune (1996) expounds the advantages of double deck installations as: 1. Fewer lifts
2. Smaller car sizes 3. Lower rated speeds
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Page 174 4. Fewer stops
5. Increased zone size
6. Quicker passenger transit times 7. 30% less core space
8. Taller buildings on same footprint 9. Smaller lobbies
10. Fewer entrances 11. Faster installation
12. Reduced maintenance costs and the disadvantages as: 1. One significant supplier 2. Passenger misuse
3. Zone populations must be large
4. Balanced demand from even and odd floors 5. Interfloor distance must be regular
6. Slightly larger hoistways
7. Increased pit and machine room loadings 8. Lobby exits need to be larger
9. Special facilities for disabled access to “other” floor.
Kavounas (1989) developed a very succinct analysis of double deck lifts following the direction of the uppeak analysis method described in Chapter 5, starting with Equation (4.11). He makes a number of assumptions:
■ The double deck lift serves 2N floors above the main terminals.
■ Both decks are the same size (CC) and carry identical passenger loads (P).1 ■ Both decks experience the same arrival process (pattern).
The expression for the high call reversal floor (H) is not changed and is given by Equation (5.12) as usual. The expected number of stops (Sd) the double deck lift will make is changed and can be derived by following the same arguments used in Section 5.3, but because the two decks together carry 2P passengers the expression becomes:
(8.2)
The evaluation of this equation could be achieved by using the familiar probable stop table (Table 5.1). However, as 2P is likely to be larger (numerically) than 26.4 persons (equivalent to a 33 person rated load) then the evaluation often falls outside the range of the table. Fortunately Equation (8.2) can be simplified2 to an easier expression:
(8.3)
1 Kavounas counsels that a more accurate expression could be obtained if the variances of the number of passengers carried on each deck were to be considered. The improvements would only be secondary as most double deck cars will be designed to fill to capacity during uppeak, thus reducing the variances. 2 To prove this, replace S in Equation (8.3) by the expression for S given by Equation (5.5), expand, combine and simplify to obtain Equation (8.2).
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For interest Kavounas also derives expressions for coincident, non-coincident stops and a Figure of Merit.1
Definition 8.1: Coincident stops will occur when both decks load or unload at the same time during