ALTERNATIVE ELEVATOR CONFIGURATIONS

In tall commercial buildings, as defined in this design guide (i.e., greater than 20 to 24 floors), multiple banks of elevators will be required to meet the handling capacity and interval criteria that have been established for office buildings. There are also other accepted standards that will affect the elevator configuration. These are:

• In the United States, for office buildings, the platform size for first-class office

buildings should have a capacity between 3,500 lb (1,600 kg) and 4,000 lb (1,800 kg). In most cases, the platform dimension should have greater width than depth to facilitate the entering and leaving of passengers. Figure 9-1 provides the typical dimensions for a 3,500 lb (1,600 kg) elevator.

• The handling capacity and interval of each bank in a project should be relatively

equal, but neither criteria should ever differ in a bank-to-bank comparison by more than 10 percent.

• The maximum number of elevators in any one bank is generally limited to eight and

they should be arranged as four opposite four to make the necessary movement from the call button to any responding elevator as direct as possible.

• If four or six elevators are determined as acceptable, they should also be arranged

in facing sets of two or three.

The arrangement of eight, six, and four elevators in a bank is shown in Figure 9-2. The above standard requiring relative parity in the handling capacity and interval from bank to bank in a given property will usually result in an unequal number of floors served by each bank. This results from the longer travel distance for the banks serving upper floors and the inherently longer travel time to complete a round trip. Accord- ingly, the banks serving the upper floors frequently serve fewer floors to reduce the round-trip travel time and maintain approximate parity in the interval.

Figure 9-1. Typical size of commercial passenger elevator. Capacity: 3500 lb (1600 kg). --``,,,``,`,,`````,,,,``,`````,`-`-`,,`,,`,`,,`---

With these guidelines in hand, it is possible for the elevator consultant to select and configure the elevators for a building. This may involve a process of give-and-take with the architect who is incorporating the elevator selections into the core design, but through the process of alternative selections of elevator systems with different platform sizes, speed, and the number of floors served, a mutually acceptable solution will be determined.

9.2.1 Configurations for Super Tall Buildings

Over the past several decades, innovations in the available elevator types have become available to meet the special needs of the super tall building. The definition of a super tall building is somewhat arbitrary but could well fit the design of a building with a minimum of 60 stories. There are two conceptual configurations available from the major elevator manufacturers. These are a system utilizing a sky lobby approach and a system using double-deck elevators.

9.2.1.1 Sky Lobby Concept

In the sky lobby concept, high-speed, high-capacity shuttle cars transport passen- gers from the entrance level to a sky lobby located at the point where the passengers transfer to a second bank of elevators that serve the local floors above the sky lobby. Figure 9-3 shows in cross section an arrangement of elevators for a building with a sin- gle sky lobby. The lower half of the building is served by local elevators configured with low-rise, mid-rise, and high-rise groupings. An express shuttle is available to take building occupants to a single-level sky lobby where they will have a second arrange-

Figure 9-2. Typical alternative passenger car configurations.

Chapter 9—Vertical Transportation | 85

ment of low-rise, mid-rise, and high-rise elevators. This configuration effectively has two standard buildings one on top of the other.

This process in a super tall building of 80 or 90 stories or more could be repeated with passengers being express-carried to a second sky lobby from the entrance level where they transfer to the bank of elevators that serve the floors to which they are going. In this latter case, the result would be a building that, in effect, would resemble three standard build- ings being stacked one on top of the other, each of the buildings having its own indepen- dent local elevator system served from the entrance level by the express shuttle elevators.

9.2.1.2 Double-Deck Elevators

An alternative to the sky lobby that has found application in tall buildings is a dou- ble-deck elevator. In this alternative, a dramatic reduction in the area required by the elevator shafts in the building core is possible. Each elevator is two cabs high and each cab serves every other floor. One serves all of the even number floors, the other every odd number floor. The two floors at the entrance level are connected by escalators to allow a passenger to get to the cab serving the floor he is attempting to reach. What results is a system where the two elevator cabs use a single hoistway, which, in turn, results in a more efficient core design for the project inasmuch as the number of elevator shafts is reduced. This benefit is obtained through a substantial premium in the cost of the elevators. Figure 9-4 shows in cross section the double-deck arrangement in a build- ing with local floor stops.

This arrangement of double-deck elevators serving local floors has had limited application and has usually been installed in a single-tenant building with a high density

Figure 9-3.

Configuration for super tall building.

of population or a building where the saving in shaft space is considered of prime import. The most common application of double-deck elevators has been in super tall buildings in combination with the sky lobby concept. In this case, the shuttle elevators to the sky lobby will be double-deck elevators. When the vertical transportation system is provided in this configuration, escalators are required at the entrance level to allow people entering the building to efficiently proceed to the correct level of elevator. Esca- lators will also be required at each sky lobby to simplify the movement up or down to the proper bank of local elevators to take a passenger to his or her local floor destina- tion. A typical configuration of the double-deck elevator with a sky lobby is shown in cross section in Figure 9-4.