A professional assessment of the elevators

From: Leslie Robertson, LRE

Subject: How to get to the top


Rick Barker (barkermohandas.com)is known to be at the top of his field.  At this moment, for example, we are working together on an overseas, multi-use, building, to be one of the tallest in the world.

It occurred to me that a way through the mechanical levels could be to exit the lifts inside of the building at the top, then pass to the outside of the building above the tenant areas, in order to reach the roof.  Such an outside structure would not suffer the difficulties with stack pressures, could be glass-enclosed and the like.  The point, here is that, in the tenant areas, there would be no structure outside of the building. As a word of warning, many persons afraid of heights, would not use such an structure.  Perhaps one lift could be completely enclosed with opaque walls.



This is one of those US corporate office towers with an abundance of elevators, due to the elevator traffic design standards involved — dense office occupancy, and elevator group handling capacity that allows for inter-floor traffic for a single corporate occupant (before email, before no smoking, etc.).  And of course these are single deck elevators, all out of the main lobby.  Pittsburgh was such a Westinghouse town back then that Otis had little chance to sell double deck elevators.  Granted these are large floor plates, but even in Southeast Asia where we actually have dense occupancy, we would be fired from any 60-story office building design where we planned 6 groups of 8 elevators at the main lobby! 

Since this is a great place to work I am sure there are still some large multi-floor tenants, involving inter-floor traffic.  But, for today’s occupancy densities this building appears to be “over-elevatored”, or our choice of words, “under-populated”.   I have studied several such buildings in the past, one mentioned below, also Sears Tower which had/has the same good problem.  For example, one could find an extra elevator per group, that could be luxuriously-used to facilitate maintenance and repairs (like rotating crops), or that spare capacity could help with the goal here.

Not really important here, but in confidence I called Dr. Bruce Powell to confirm that the elevators are/were Westinghouse.  Bruce worked at the (W) corporate R&D center back then, supporting the elevator division with next-generation computer-based traffic calculations to optimize multiple elevator groups.  (Bruce was the first to develop such a program, and now we are the only consultant with such a tool, and we think only Otis has an outdated simpler version of such a tool).  Bruce later joined Otis where we worked together on such things, and he now consults for another elevator company.  Bruce believes that Schindler modernized the Westinghouse elevators quite a while back.

Something that both of you mentioned is interesting, that everybody or most people entering/exiting need ascend escalators to 2ndlevel, which is the main lobby.

Of course changing to double deck elevators is worth studying if all floor heights are equal starting from 2ndlevel, one could create an equal height dual boarding level (via an interstitial level below Floor 2 or using the entire ground lobby height), andthe space savings would be useful and rentable — to help pay for the large costs involved!  Likely the flexibility of steel frame construction would allow for certain adjustments if needed, for example at machine room levels for what “might” be larger-footprint machines for double deck elevators (while certain machine designs are now more efficient in size)… then you would quickly know how the present supports would handle the increased loads, but from fewer elevators.  To of course use existing hoistways, where there is a 4000lb single deck elevator, it could be likely be changed to 3500+3500lb double deck (larger car framing and rails), and for highest rise groups swap a 3500lb car with a 3000+3000lb double deck, both worst case conditions. 

Of course with 7000lb elevator in a 4000lb hoistway, we are not surprised today when we find up to 40% savings in hoistways in a new building design, compared to single deck, for the same occupancy densities – but with a bit higher floor populations with double deck because of the space returned.  Then of course the additional costs of double deck (2X a new elevator), are offset by the space returned.  Of course in an existing building, you already have the single deck elevators, and lots of them.

So, double deck is just one element in an arsenal that should be studied.  I would bet with a good re-study, and today’s populations, a couple “spare” hoistways could be found without double deck.  Then with some luck, that might even be a high-rise group that gets close to the top, or a group or two with things above the machine room that could be displaced.  And if the market is now smaller tenants, we might split some 8-car groups in half, and leave the machines high (and install longer ropes so the lower-rise elevators do not travel higher).  Again, one of many things to study.

Since all office tenants apparently ascend to the 2ndfloor main lobby, it seems logical that the ground level would be a good place to separate tourists, restaurant-goers, etc. boarding new OB deck elevators.  But I’ve never seen the building or plans (beyond one steel framing plan in the book). 

I cannot say this is feasible, but this is most definitely worth studying to find different solutions to get to the top, via the existing core to start.  The studies are a significant effort.  We would need all the net useable areas, ideally the present populations, and the current details since this book (a trip to Pittsburgh). 

But, going back to the multi-elevator-group software tool I mentioned, this is a side reason we built it!  Years ago before joining Otis (at JB&B) I re-elevatored the oldMetLife building (almost 90,000 SF floors at the base) for a large financial company that moved in.  I swore I would never do that again, manually, one group at a time!  Pei’s BDNI was another reason, as their designs continually changed!

Then in parallel, it would also be fun to find an architecturally and tenant -pleasing (6 corner offices per floor.. hmm) solution to place observation deck + restaurant elevators at the exterior.  As you know, together with the architect down under we just planned what we will become the world’s record-travel, scenic, double-deck elevators, at an exterior wall.  One deck suits tourists, the other a restaurant.  During off-hours for the restaurant, we have both decks stopping sequentially at 1 boarding level for tourists.  We could even need to think about special shape scenic elevators, if the cab floor plan is still useful. 

While double deck lifts are green as a system, fewer of them, fewer stops, and fewer stops still with today’s destination dispatching, the other view is to reuse what we have and save money.  Likely Schindler modernized the (W) elevators with new power electronics drives, replacing the motor-generator sets, re-using the machines including their DC motors.  These were certainly a nasty drive using SCR transistors (low power factor, high harmonics, line notching, high peak currents to magnetize transformers used for line isolation.. very unkind to existing electrical wires and emergency power systems).  Finallyavailable for existing DC elevator motors, is the drive technology we now apply to the latest high-speed elevators.  (See the CV of George Wisner on our website – George studied such drives way back at Otis R&D.)  Replacing one static drive with another will not benefit the Client that much on paper, as doubtfully Pittsburgh penalizes buildings for poor power factor (like they did the USS mills), and if they did the electrical engineer could add correction capacitors, but works for PR and with the right type of dispatching there would be some benefits.  But the bigger benefits would be in studying all things as a whole with the goal involved. 

This is just from a quick browse of the book, and a call to confirm that these are Westinghouse elevators.  Of course, you will associate this mind dump with Barker Mohandas doing the work!  Very exciting also, because Pittsburgh is called the best place to live in the Northeast these days.

Rick Barker