Taipei Financial Center

by James W. Fortune

When completed in 2003, the 101-story Taipei Financial Center (TFC) office tower in Taipei, Taiwan will be the worldÕs tallest building at 508 meters and be equipped with the worldÕs fastest elevators at 16.8mps. The building floors will be divided into three local zones and will have dual, upper-level sky lobbies. Each sky lobby will be served by a five-car, double-deck group of express shuttle elevators, while each local zone will be served by two groups of four double-deck local lifts.

Two high-speed, single-deck, observation-level shuttle cars will run express from the B1 level to the observation deck on Floor 89. These two lifts will be the worldÕs fastest elevators with a contract speed of 16.8mps (3,280fpm) up and 9.0mps (1,800fpm) down so as not to violate the inner-ear atmospheric-pressure change protocols. The elevator up speed will be a dramatic increase in elevator velocity and will establish a new world record, which is currently 12.5mps (2,500fpm) in JapanÕs Yokohama Landmark Tower.

Lerch Bates & Associates Inc. (LBA) designed the complete elevatoring for the project, created the lift and escalator contract documents and will oversee the installation.

The WorldÕs Fastest Passenger Elevators Ð Concept to Completion

Toshiba/G.F.C. Elevator Co. is installing the worldÕs fastest passenger elevators in the TFC. The installation is scheduled for completion in late 2004. Recent innovations in the elevator-hoist machine, motor drive, hoist-rope construction, motion control and ride-quality technologies have made these speeds possible. Even with all of these technological improvements, Toshiba Elevator had to design, produce and install a number of brand-new components to make these cars a reality.

Background

Figure 1 summarizes the current listing of the worldÕs fastest passenger elevators. These super-fast elevators have typically been installed in pairs and are utilized to express visitors to a buildingÕs observation levels. These trips are usually not free with a charge of US$10-12 per person as the normal cost. The faster speeds are not necessarily needed to significantly reduce the transit time. For instance, both the former New York World Trade Center towers and the Sears Tower shuttle elevator travels were/are greater than the TFC units, but the elevator speeds are less.

Why do it? Everyone wants to visit the worldÕs biggest, smallest, tallest, fastest, whatever record holders. This is the reason that the Guinness Book of World Records was established to record and keep track of these Òmodern marvels.Ó And, yes, there is a category called the ÒFastest Passenger Lifts,Ó where the Yokohama Landmark Towers units are listed. Mitsubishi Elevator Co. was awarded a Guinness Book of World RecordÕs plaque commemorating the achievement.

Having the worldÕs tallest building can also be a prestigious boom to a city in transition from developing country status to high-tech arrival in the 21st century. Just look at the impact that the 88-story twin Petronas Towers had in placing Kuala Lumpur Òon the map.Ó A similar impact should be gleaned for the city of Taipei, once this new record holder has its grand opening. AsiaÕs one-upmanship will no doubt continue.

In the case of elevators, people simply want to ride on the worldÕs fastest elevators and experience the sensation of doing so. This is the reason that the high-speed lifts in the Yokohama Landmark Tower and Sunshine 60 buildings are equipped with onboard velocity meters so that the lift speed is continually scanned and displayed on the car visual display units (VDU) for the elevator riders, much like an automobile speedometer. Since these elevator speedsters are almost always installed in mega-high-rise projects with top-floor observation decks or restaurants, the attraction of riding on these lifts is complimented by the sensation of Òclimbing to the top of the mountainÓ to experience the ÒbreathtakingÓ view firsthand.

In this case, the elevator Òthrill rideÓ then becomes the gateway to the Òview from the top.Ó The TFC observation lifts will be similarly equipped with onboard digital speedometers that will be continually displayed on the car VDUs. Unlike a high-speed roller coaster or amusement ride, where the object is to present the rider with a sensation of speed through rapid changes in travel direction (jerk) and abrupt accelerations/decelerations, modern high-speed elevators are designed to run quietly and with the least possible perception of movement. In fact, modern elevator ride quality is so good it is sometimes difficult to ascertain when the elevator is actually moving without onboard visual cues in the form of car position and travel direction indicators.

Physiological Problems Associated with High-Speed Lifts

The human body has various internal sensors that are sensitive to external motion forces, noise and vibrations. These sensors provide constant feedback to the brain and are quite responsive to any Òout-of-the-ordinaryÓ elevator vibrations or noises, as the lifts travel through the hoistways.

The elevator industry has developed the following physiological limits which standing elevator riders can tolerate without feeling discomfort:

Most of the major elevator companies have recently developed completely new Òsuper-quietÓ elevator ride quality protocols for use in mega-high-rise structures. These include maximum interior sound levels of ²45dBa and horizontal vibrations in the 8-10mg range.

All of the physiological elevator design parameters, except ear-pressure changes, can be regulated by proper equipment designs. Ear comfort/pressure changes do not usually affect elevator riders, unless the descent speeds exceed 485-610mpm (1,600-2,000fpm) and the vertical travel exceeds 300 meters (1,000 feet).

In 1956, when Frank Lloyd Wright revealed his plans for the Illinois (Mile High) Office Tower to the Chicago Daily News, which subsequently published a story reviewing the proposed method of elevatoring the project, the paper immediately received comments from a number of airline pilots questioning the ability of 1,610mpm (5,280fpm) elevators to serve the project without causing eardrum damage in the riding public. Airline pilots are well aware of the problems associated with too rapid a change in altitude. Apparently, the inner ear can react adversely to changes in pressure associated with rapid ascents and descents that are experienced as aircraft change altitudes. The same condition can affect elevator riders traveling in the down direction, at high speeds and long travels. Elderly persons, those with colds, flu or allergies, or those who cannot rapidly clear their ear passages are more at risk. Obviously, if the 1,610mpm (5,280fpm), quintuple-deck, atomic-powered elevators envisioned by Frank Lloyd Wright were to really rise and then descend about 1,610 meters (5,280 feet), above grade in just one minute, the riders would probably experience considerable pain if they did not sufficiently ÒclearÓ their ears en route or if the cabin (cab) pressure was not controlled.

Think of the middle ear as a balloon that expands as exterior pressure decreases during ascent and contracts as exterior pressure increases during descent. As pressure in the airliner cabin or elevator cab decreases during ascent, the expanding air in the middle ear pushes the normal Eustachian tube (Figure 2) open (at about 4,000 Pa) letting the increased pressure escape down into the nasal passages until the pressure in the inner ear and the cabin, cab or final ascent level is equalized. However, during rapid descent, the passenger must consciously open the Eustachian tube by swallowing, yawning, tensing muscles in the throat or by closing the mouth and pinching the nose closed and attempting to blow through the nose (Valsalva maneuver) to equalize the pressure. If either the ascent or descent (particularly, the descent) is too rapid and the pressure is not relieved, a painful condition called ÒEar BlockÓ can develop. Ear block can produce severe inner-ear pain and loss of hearing that can last from several hours to several days. If not treated, fluid can accumulate in the middle ear and become infected. In extreme cases, eardrum rupture can occur.

Reportedly, the two 2,725kg at 540mpm (1,800fpm) observation elevators that express 410 meters (1,346 feet) from the ground to the 103rd observation deck in the Chicago Sears Tower had to be slowed down to 485mpm (1,600fpm) in order to minimize the problems and potential litigation associated with ear block (Figure 3). Supposedly, one of the building visitors suffered a broken eardrum sometime after descending from the observation deck via the shuttles, when they were running at their original contract speed.

In order to better understand the pressure differential problem and suggest some solutions that may assist in designing future mega-high-speed, high-travel observation lifts, it would be beneficial to review how the airlines handle rapid altitude changes. Most jet aircraft cruise at altitudes of 9,100-12,200 meters (30,000-40,000 feet) above sea level, while the cabin is pressurized to a maximum of 2,450 meters (8,000 feet) to protect the crew and passengers from discomfort. After takeoff, the cabin is pressurized at a nominal ascent rate of 105mpm (350fpm), even though many jets climb at a rate of 915-1,220mpm (3,000-4,000fpm). This combination of pressurization and ascent speeds are apparently agreeable with the passengers and little discomfort is normally experienced. However, because of the difficulty some people have in clearing their Eustachian tubes, the descent process can be much more complicated. During descent, the cabin is depressurized at a nominal descent rate of 105mpm (350fpm) after the aircraft descends to 2,450 meters (8,000 feet) while the actual descent is accomplished at about 150mpm (500fpm).

At this rate, it would take about 23 minutes to reduce cabin pressure to that experienced at sea level. Notice that the salient points here are that ascent can be accomplished very rapidly with little discomfort while descent must be carefully controlled. Have you ever noticed a baby crying on an airplane during descent? The baby cannot consciously clear its ears, so when the inner-ear pressure builds up causing pain, the baby cries in response, and, voila!, the painful inner-ear pressure is naturally cleared.

New Technologies

Major automobile manufacturers often experiment with new, exotic equipment designs on race cars to perfect their operations and improve the car performance before later incorporating these improvements into their everyday products. Similarly, elevator manufacturers will utilize specialized, high-speed elevator applications in order to perfect their new equipment offerings. In order to install the worldÕs fastest lifts, Toshiba Elevator had to develop and adopt a number of new technologies in order to bring these elevators to fruition:

New Gearless Hoist Machines and Drives

Beginning in the late 1980s and early 1990s, most major elevator companies started switching from direct current, gearless hoist machines and SCR power conversion units (DC VV drives) to alternating current, variable voltage, variable frequency (ACV3F) machines and drives. These ACV3F machines were more efficient, had smaller profiles, better power factors and were cheaper to run (lower power costs) than their DC counterparts. The new ACV3F induction gearless hoist machines (lifting capacities up to 100 tons) were also much more powerful than the shunt wound, DC gearless hoist machines (lifting loads about 70 tons maximum) that they replaced. The early ACV3F power conversion units (drives) utilized were very expensive as they included up to 50 each, integrated gate bipolar transistors (IGBT) in the drive. For very high-speed lifts, two IGBT drive units were often used in parallel to provide enough amperage to run the elevators. IGBT drives could cost two to three times as much as the DC SCR drives that they replaced and had limited output amperages available to run the hoist machines. This is the reason that some elevator companies, to this day, still try to provide ACV3F machines and drives that have limited acceleration/ deceleration values and jerk rates and are non-regenerative until the duties reach ³300mpm (1,000fpm).

Just as Toshiba was developing and perfecting their ACV3F gearless induction hoist machines and IGBT drives for use on the TFC observation level shuttles, the available technology again changed with the advent of the permanent magnet synchronous motor (PMSM), ACV3F gearless hoist machine. These new PMSM hoist machines are even more powerful and efficient than their ACV3F induction counterparts even though they tend to be smaller. In a PMSM motor, copper-wire wound armatures are not required as the rare-earth neodymium permanent magnets are glued directly to the hoist machine armature, sometimes in a vertical, disc configuration and the motor frame sizes are further reduced. In some cases, more efficient, dual disc hoist machine brakes can be utilized in lieu of the standard drum brakes.

Hoist Ropes, Car Safeties and Buffers

Extra high-strength steel hoist ropes with solid-steel cores that are connected to the car and counterweight with wedge-type shackles have been developed to give the required 10:1 safety factor. Solid-core hoist ropes have superior wear characteristics and do not stretch as much as conventional, hemp-core hoist ropes when utilized on high-speed lifts. Most elevator codes require the car safeties and pit buffers be capable of providing at least 1g (9.8mps) deceleration during an emergency stop.

Standard car safeties have historically utilized bronze-faced safety shoes that were good for speeds up to about 600mpm (2,000fpm). Beyond these speeds, the bronze shoes would tend to melt as they slid along the car rails during a safety test. Consequently, Toshiba had to develop new ceramic shoed safeties. At 1,010mpm (3,300fpm), the ceramic safety shoes seem to dissipate the heat generated quite nicely, although sparks actually fly off of the car rails while the safety gradually sets. Each shoe is good for about three-to-five safety settings before they must be replaced.

The car and counterweight overspeed, oil-hydraulic buffers are located in a pit below the car. Since the units are all rated to give a 1g, deceleration value, as the car speed increases, the buffer stroke increases, and the elevator pits also get deeper. At speeds from 300mpm (1,000fpm) up to 540mpm (1,800fpm) reduced stroke buffers (300mpm) are typically utilized in conjunction with a speed-reducing device (ETS) so that the clear pit depths are about 5.3 meters (17 feet and 6 inches) deep. With a contract speed of 1,010mpm (3,314fpm), a normal buffer stroke with ETS would require the pit to be 22.5 meters (74 feet) deep. In response to this dilemma, Toshiba developed a triple-acting (three-plunger) compact buffer with ETS so that 16.5 meters (54 feet) deep pits could be utilized.

Windage, Pressure and Noise Abatement

High-speed, nuclear-powered submarines are equipped with rounded, bullet-shaped snouts and rounded fuselages to minimize water-induced noise and vibrations as they slice undetected through the seas. High-speed elevators are similarly equipped with an aerodynamic capsule, top and bottom shrouds with spoilers to provide for a smooth exterior air flow and a narrow wake, as they travel at high speeds through the hoistways. To further reduce windage noise, the TFC observation shuttles will be equipped with super-sound isolation shrouds, double-plenum cabs, acoustic ceiling tiles and double-isolated car platforms. The counterweights will be similarly encapsulated with windage shrouds to minimize the pressure column buildup that can occur between the counterweight and the passing elevator car.

The TFC shuttle cars will be provided with two air pressure/ exhaust control blowers mounted on each car top to decompress and recompress the air pressure inside the cabs. These devices will partially mitigate the physiological, aurial discomfort associated with rapid ascent and descent speeds and travel distances as they will pre-condition the cab pressure as soon as the car doors close and the elevators start to accelerate.

Elevator Ride Qualities

In order to achieve world-class ride-quality standards (8-10mg horizontal displacements) on the TFC shuttle lifts, Toshiba has developed a number of new technologies to ameliorate and counteract the normal Òcar sway and vibrationsÓ associated with high-speed lifts. Toshiba has developed large diameter (350-millimeter) car roller guide shoes to run on the car rails. It is a generally accepted design rule that the larger the car guide shoe roller diameter, the better the car ride is due to the reduced rpms, and less vibrations are induced into the car frame. The new roller guides are also center spring loaded and utilize a balance weight to dramatically reduce the lateral shaking associated with car-rail deformations.

The Toshiba power conversion units will use inverse linear quadratic (ILQ) theory chips to measure hoist rope induced vibrations and counteract the low frequency vibrations by controlling the frequency, pulse and amplitude of the ACV3F current fed to the PMSM hoist machine. The car rails will be jumbo unit matched sets, joined by full section modulus fishplates with smooth joints and correctly positioned by laser alignment. The most unique innovation will be the first use of active-tuned mass dampers (AMD) mounted to an elevator car. By moving a small mass mounted on a screw jack by a servo motor to counteract objectionable car vibrations that are sensed by an accelerometer, the AMD can reduce the vibrations and immensely improve the car ride. The beauty of applying AMD technology to high-speed elevators is that they can be switched on to counteract bad vibrations caused by building sway, building movement and rail misalignments, regardless of the load in the car, the machine room temperature variations or the hoist rope stretch.

Reprinted with permission from The Council on Tall Buildings and Urban Habitat James W. Fortune is president of Lerch, Bates & Associates Inc. He has a BS degree in industrial technology with a major in architecture from California State Polytechnic University and an MBA from the University of Denver.