cal lewis

November 27, 2018 § 5 Comments

An immeasurably sad week.  Iowa has lost one of its great architects, and many of us have lost a great friend and mentor.  Cal Lewis, who had been a partner in the Des Moines firm HLKB and then department chair at Iowa State for ten years, died Saturday. He’s left a legacy of buildings in Des Moines and throughout the state–many that he designed, many that he subtly influenced, encouraged, or nurtured into being through his quiet persistence and vision.  But more importantly, the people he supported, taught, and encouraged, during his career have gone on to found dedicated practices, to design thoughtful spaces and buildings, and to pass on his caring, challenging studio teaching.

Cal began his chairmanship the week I arrived at Iowa State, in 2000, and he was patient and supportive while I found my feet in academia.  (Years later he would admit to me that he was finding his as well).  He championed young faculty, finding ways for us to present at four or five conferences a year, realizing that exposure like that was important for our careers and for a program trying to make its mark nationally.  He and I shared a basement studio space in the College for three years, where I learned the craft of teaching from him and we convinced students that being hidden away gave us the advantage that no one knew what we were up to.  And, last year, Cal volunteered to nominate me for AIA Fellowship.  Joining him in the College of Fellows was a distinct honor, and the extra letter after my name is one of dozens of reminders of a career and a life that truly made a difference.


hancock elevator “plunge?”

November 19, 2018 § Leave a comment


hancock sofitel

Juicy story yesterday about the failure of an elevator cable in the John Hancock Tower’s 96th floor express shaft. According to the Tribune:

On the return trip, the elevator started going down faster than they were expecting, said one of the students, who didn’t want her name used for privacy reasons.

“It was really bumpy — it felt like a flight into Chicago,” she said.

Married couple Jaime and Maña Montemayor of Mexico City were on a business trip and had just finished dinner with a large group. After getting in the elevator they suddenly heard a loud “clack clack clack clack clack,” said Jaime Montemayor, 50.

Then dust particles began seeping into the elevator, and they panicked. “I knew something wasn’t OK,” said Maña Montemayor, 49.

Initial press coverage talked about the elevator “plunging” 84 floors, finally becoming stuck between the 11th and 12th floors, and the fact that the elevator was in a “blind shaft,” meaning firefighters had to cut through “concrete walls” to access the cab.

Scary stuff if you’re stuck in the cab, for sure.  And some commenters have noted that safety brakes should have engaged if the elevator did, in fact, ‘plunge.’  But I think there’s a slightly more benign explanation, especially given some confusion about the sequence of events.

The express elevators in the Hancock are fast–really fast–1,800 fpm, which makes them as speedy as any others in the U.S.  The ride down, especially for those on their first trip, is pretty dramatic and, frankly, bumpy.  And its elevators, like every other one in the U.S., has multiple hoisting cables, designed to ensure that, if one fails, there’s plenty of redundancy.

The Washington Post’s version of the story gets the timing a bit different:

It whizzed past all the usual stops, falling and falling and falling 84 floors before coming to an abrupt stop somewhere between the 11th and the 12th.

Then came the dust and dirt, floating into the elevator from the ceiling.

And then came the panic.

If that’s accurate, then it’s entirely possible that nothing went wrong until the cable failed.  The safety brakes may have engaged then–or, alternatively, since there would have been plenty of redundancy, it’s possible that the elevator never exceeded its safe travel speed, and only got jammed when the snapped cable ended up getting snagged in the guide rails.  A falling cable is a pretty grave hazard, but the “clack clack clack” jibes with the loose end banging against the other, remaining cables as it fell.

Once the elevator was stuck, getting the passengers out was a definite problem.  Express elevators typically are placed in ‘blind shafts’ that bypass floors they don’t serve.  Every elevator door costs roughly the same as a small car, so if there’s no reason for the elevator to stop on, say, the garage floor on 11, there’s no reason to spend the money.  My initial thought was that the ‘concrete’ that firefighters had to dig through may have been a shear wall, which would be a pretty heroic job, but Chicago Fire Department photos show that it was actually a concrete masonry wall–not structural, and not reinforced–that they had to get through:

Screen Shot 2018-11-19 at 8.31.40 AM

All of that is scary enough, especially if you’re the one trapped in the cab for 2-3 hours.  But, as often happens, the press coverage veered pretty quickly toward the sensational.  A cable snapping in a high-rise elevator is a vanishingly rare occurrence, whereas a century ago this happened with alarming regularity–and universally fatal consequences.    It’ll be interesting to see what the final report on the incident says, but if, in fact, the above scenario plays out then the fact that no one was even hurt–and that an event like this is so unusual–speaks to just how safe modern (or, even, half-century-old) elevators are.

encoding design

November 10, 2018 § 1 Comment

Looks promising, doesn’t it?1951 code cover

In Chicago for this weekend’s Chicago Design Conference at the Art Institute, presenting a rabbit-hole of research on Chicago’s 1951 Building Code, which is a great story about how political and economic considerations end up being imprinted–literally ‘encoded’–into buildings through these documents.

The city’s code through WWII had been a ‘specifications’ code, one that held architects and builders to strictly defined materials and dimensions depending on the level of fire resistance a building type and location demanded. This worked well for an era where brick, concrete, stone, plaster, and terra cotta were pretty much the only materials being considered for building exteriors and walls.  But technical developments in the 1930s and, especially, during the war meant that the code left a lot of innovation on the table, with no way for designers to take advantage of new materials like, say, aluminum in skyscraper construction.  Or new production techniques like gypsum drywall in residences.

John O. Merrill was the choice of a coalition of civic leaders to put a new code together.  They had hired the John Pierce Foundation to prepare a study of new types of building code, and the Foundation was familiar with Merrill’s work on the extensive housing constructed for Oak Ridge, Tennessee–which because of wartime exigencies had been largely unregulated and, therefore, particularly innovative.  Merrill and his team put a draft code together in 1948, and it spent two years in limbo as building trades, manufacturers, developers, and politicians argued over its merits.

The full story is in  the conference paper here, but suffice to say that the proposed code served as a lightning rod for everyone who had a stake in the changing nature of high-rise and domestic construction.  Labor-saving technologies like drywall drew the ire of tradesmen and their unions, who used fears about fire to bolster their arguments against such threats.  Developers and other trades–in particular carpenters, who stood to benefit from relaxed standards for frame construction–lined up in favor of Merrill’s code.  Ultimately, after controversies, an underhanded attempt to sneak 25 amendments in without the public noticing, and a brokered compromise by new reformer mayor Martin Kennelly, the code passed on New Year’s Eve, 1949.

Among other things, the new code’s relaxed standards eliminated tight specifications for spandrel walls in high-rise construction.  The old code had dictated upstand walls between windows, assuming that all skyscrapers would have more or less solid skins with punched windows:

“Every window in a non-combustible wall shall have a non-combustible sill and spandrel wall equivalent in fire-resistive value to two-hour fire-resistive construction for a vertical distance not less than three feet between such opening and any opening in the story next below such opening.”

The new code required structural elements to maintain a three-hour fire rating, but loopholes in definitions and classifications left no such requirements for the remaining territory of any non-bearing exterior wall that faced a street or a court.

The result can best be seen in Mies van der Rohe’s first two projects for developer Herbert Greenwals–Promontory, which was completed in 1949 to the old code’s spandrel standards, and 860-880 Lake Shore Drive, which was permitted after the new code took effect, and which took notable advantage of the newly-freed exterior wall:

Encoding Design Slides Nov 2018 Promontory 860.001

The code linked construction downtown and development further afield in balancing concerns for safety with innovation and the political power of unions and developers against one another.  As such, it’s one of several precursors I’m looking at in trying to figure out how innovative high rise construction took root in the city some twenty years after development ground to a halt during the Depression.  Codes are always political documents, but this episode illustrates this brilliantly.

Thanks to colleague and office-mate Andrew Gleeson for pointing me in the direction of numerous assessments of Promontory’s spandrels–theories on them have ranged from lack of steel to a conservative building culture, but the impact of the code’s restrictions seems to be a new piece to add to the puzzle.

APTWGLC and CHSA joint symposium in Chicago, 17 May 2019

November 7, 2018 § Leave a comment

blackstone-hotel-1909Couldn’t be happier about this–two great organizations joining forces to spend a day talking about old structures, how they were built, and how to make sure we keep them around.  Please consider submitting an abstract–the list of potential topics is wide open, and we’re always keen to hear from new voices and to discover new topics.

Call for Abstracts




Preservation of Industrial Archaeology and its Construction History


Friday, May 17, 2019

Program:  8:00 am – 4:00 pm

Reception: 4:00 pm – 5:00 pm


School of the Art Institute of Chicago’s Ballroom

112 S. Michigan Ave. Chicago, IL


The Association of Preservation Technology, Western Great Lakes Chapter (APT WGLC) and the Construction History Society of America (CHSA) invite interested parties to submit abstracts for presentations to be considered for the joint 2019 Symposium on the theme:Preservation of Industrial Archaeology and its Construction History.  The program will offer a single track, intermingling the two disciplines of preservation technology and construction history with a scientific committee composed of members from APT WGLC and CHSA.

Abstracts focusing on subjects related to industrial construction during the 19th C. in the mid-west are encouraged such as:

–  Mill design and construction

– Fireproofing options for industrial buildings

– Lighting solutions prior to electricity

– Industrial power sources

– Railroad construction in the area

–  Iron & steel manufacturing innovations

– Evolution of industrial structural design

–  Canals, waterways and Great Lakes transportation

– Incorporating historic industrially zoned sites with modern approaches to urban planning

– Challenges of preserving industrial sites and buildings

– Interpreting historic equipment in a modern reuse of an industrial site

– Archaeology at an industrial site – how discoveries inform design

– Abatement of archaeological sites


Professional presentations (including five minutes for Q&A) should be 20 minutes, while Student presentations should be 10 minutes. See below for further submission clarifications.

Abstracts for Professional presentations should be no more than 4000 characters and should include:

  • Title of presentation
  • Author’s name & contact information (include title and/or credentials as preferred for publication)
  • 200 word or less biographical statement (for speaker introductions)

Abstracts for Student presentations should be no more than 4000 characters and should include:

  • Title of presentation/research study
  • Student Name, University & contact info (include title and/or credentials preferred for publication)
  • 200 word or less statement of future professional or research interest (for speaker introductions)

All abstracts should be submitted via EasyChair –


Deadlines and notification dates will be:

  • Deadline to submit:January 7, 2019
  • Author NotificationJanuary 25, 2019
  • Speaker Registration DeadlineFebruary 8, 2019
  • Presentation submission:April 17, 2019
  • SymposiumMay 17, 2019


Presenters are not required to be members of APT WGLC or CHSA. Each accepted abstract will receive discounted conference registration for one Member-presenter. Discounted registration will be provided for a second Member presenter and Non-member presenters.

Accepted abstracts will be published on APT WGLC and CHSA websites. Submission of an abstract implies agreement that if accepted the abstract may be posted on said websites or other symposium marketing materials.

For more information, please visit:

Should you have questions regarding this call for abstracts, please email the APT WGLC board at or CHSA at



go big…

October 24, 2018 § Leave a comment

EVt5PI5nTlCnTxOvthYKPg…or go home.  Mid-reviews last week for studio, which this semester is looking at a high-rise University Center in the South Loop.  Picking up on projects by the seven colleges and universities in the neighborhood, we’re proposing joint dormitories, academic facilities, and social spaces that would provide the schools with common facilities, on a site that’s equally convenient to each of them.

And, frankly, a doozy of a site.  The long block at Harrison and State is wedged up against the Green line El tracks, and it faces a variety of building types–a large college prep school to the west, a pretty lousy dryvit wonder university building to the north, and the venerable South Loop Club to the south.  The string of buildings on Wabash, to its east, includes the historic Studebaker building, and the vacant lot that was the site of Sullivan’s Wirt Dexter Building (R.I.P.).  So there’s a lot to respond to in terms of scale and composition.EPsQU3FzT46BWt4v8+cO9A


The program?  Well, working with alums at SOM, we came up with a modest 1.7 million square feet of space, working toward an FAR of about 16.  That’s translating to anywhere between 900 and 1500 feet of tower, depending on how you work setbacks, open space, and how much air gets pumped into the academic program.  The results are, well, pretty tall, but they’re likely to be more and more ‘contextual’ as the neighborhood develops.


Mid-reviews last week focused on elevatoring, fire exiting, and wind bracing, as you’d expect.  But with most of the projects on their way to putting ticks in those boxes we’re on to elevations and cladding this week, turning them from just really tall towers to the ‘proud and soaring things’ they’d need to be.  Good fun, and happy to be back in the city, spiritually, at least…


inland steel’s ‘non-budging’ windows

September 24, 2018 § 3 Comments

inland 1Diving into press coverage of the 1957 Inland Steel Building and finding good corroboration for my research team’s work over the last couple of years that argues for its curtain wall as a true touchstone in the development of the postwar high-rise.

Inland Steel was really the Reliance Building of its day–a groundbreaking advance in moment frame steel structures clad by an equally visionary thin cladding system that, together, defined a generation’s worth of skyscraper engineering and design.  I’m currently working on the influence of the city’s 1951 Building Code on its generation, and Inland did take advantage of new performance based provisions that allowed its skin to be far thinner and more open than its predecessors–more on that later this Fall.

For the moment, it’s interesting to read in contemporary press coverage how shocking its glass curtain wall was.  Ernest Fuller, one of the Tribune‘s real estate columnists in the 1950s, expressed surprise and excitement over its “non-budging” windows:

“If you have a window at home that won’t open no matter how you tug at it, consider the owner of a building with 1,491 windows that refuse to budge. Yet, Inland Steel company is putting up such a building and intends to live happily in it.

“The company’s 19 story office building under construction at the northeast corner of Monroe and Dearborn sts. is currently being outfitted with the glass part of its stainless steel and glass exterior.  The window work is progressing from the top and the bottom of the structure at the same time.

“Architects report the concept of intentionally fixed windows is about eight years old, said a company spokesman.  (There is no record of when windows first became fixed out of pure orneriness). Both the Seagram’s and Lever House buildings in New York City have the fixed type and some smaller installations have been made in Chicago.”  [Ernest Fuller, “Inland Unit Windows Are Nonbudging Kind.”  Chicago Daily Tribune, July 28, 1957.  A9.]

This is a good reminder that, although air conditioning had been installed in Chicago commercial buildings throughout the 1930s, Inland was only the third high-rise in the Loop to be built in the intervening decades.  Prudential’s windows, Fuller notes, were designed to stay shut, but could be pivoted open for cleaning.  The Sinclair Building, completed in 1954 at the corner of Wacker and Randolph and designed by Holabird, Root & Burgee, may have been the “smaller” installation referred to by Fuller (long since demolished).

It’s interesting to note that Lever House and Seagram’s were the examples that immediately came to mind for Fuller–showing that these two buildings were in fact considered state-of-the-art for Chicago’s frustrated skyscraper designers in the 1950s.  The city would have to wait for a comprehensive re-zoning before buildings taller than Inland were constructed, though by 1957 relief was in sight.

Fuller goes on to note what my team documented–that these ‘non-budging’ windows were important counterparts to air conditioning in enabling the glass curtain wall, since they were composed of glass that was not only insulated, but also heat-absorbing:

“Inland’s double-paned windows will do more than admit light, however. They will insulate against cold in the winter and heat in the summer, aided in the latter job by the sun filtering blue-green tint of the outer pane.  Incidentally, although the glass will have a decided hue to outsiders, insiders will not be aware of the color, said the Inland spokesman.”

What really struck Fuller and others, though, wasn’t just Inland’s non-budging, insulated and tinted windows.  It was the way these were to be maintained.  Borrowing from Lever House’s intentionally visible window-washing system (appropriate, of course, for a soap manufacturer), SOM’s Chicago office detailed a similar system for Inland that relied on rail-like window mullions, providing sidewalk drama for pedestrians who had, to that point, yet to see anything like it in the Loop.


August 31, 2018 § Leave a comment

aerial 02 onramp

(UPDATE: Sept. 6, see below)

The collapse, two weeks ago, of a span of the Polcevera Creek Viaduct in Genoa is a particularly sobering structural failure.  Authorities put the death toll at 43, and beyond this is the fact that the bridge was literally a textbook example–one of the truly great pieces of structural expressionism that was, for more than fifty years, hailed as a work of structural art.  Its designer, the Roman engineer Riccardo Morandi (1902-1989),  was a near-contemporary of Nervi.  His path took him to bridge design after a similar early career in cinema and theatre roofs.  Morandi’s practice represents a shift in Italian engineering from the lingering economic and cultural influences of autarchy, which emphasized concrete as a locally-produced material, to steel, which had been unavailable in Italy during the fascist era, but which proved itself economical during the post-“Italian Miracle” era of rising inflation and thus the need for more rapid construction.

sectionsThe Polcevera viaduct, completed in 1966, was his masterpiece–a muscular but finely proportioned march of concrete towers across an urban valley that provided a crucial autostrada link between Genoa and the resort town of Savona to the north.  Morandi’s solution to the difficulty of the 1200-meter span was two-fold: a viaduct on the northern half of the valley supported by vee-shaped compression towers, and three cable-stayed, cantilevered spans supported by taller towers on the southern half.  These spans used what would become Morandi’s signature technique, combining steel and concrete into massive pre-stressed tendons.  While ordinary cable-stayed spans rely on multiple, individual strands of steel cable, Morandi’s solution gathered hundreds of these strands into single elements.  Other engineers critiqued this idea, noting that since cable-stayed bridges rely on a deck that can absorb huge compressive forces, this necessitated a stiffer than normal roadway and thus a tremendous amount of extra dead weight.  But Morandi argued for the technique for its elimination of costly cable maintenance.  Wrapped in concrete, the steel strands would not require the near constant painting involved with the traditional fan-shaped solutions, and the resulting visual effect was particularly striking; the simplicity of the structural diagram made the bridge’s structural performance evident even to laypersons.

Const 02 three towersConstruction photos reveal a great deal about the behavior of the bridge.  In the above image, you can see that the decks were actually self-supporting under their own loads.  They are actually supported by diagonal members that frame into the towers’ bases, and were formed by traveling formwork that balanced around each tower.  This shot shows each of the three towers at successive stages–the one in the center shows just how far the decks could cantilever under their own weight, making the tendons themselves responsible primarily for carrying the bridge’s live loads.

Const 01 two towersHere, too, you can see the cables being draped from the tower on the left–not yet carrying any load.  Once these were tightened, encased in concrete, and assisted by further post-tensioned cables in their concrete jacket, the short span between the two cable-supported decks could be placed.  This sequence was much like that of the Firth of Forth Bridge, where the steel cantilever towers were gradually extended, and then the span between them filled with a short, beam-like infill.

Const 03 one towerThis shows the steel tendons being wrapped with their concrete jackets after they’ve been tensioned–the deck is actually warping upwards, a deformation that would be corrected once the load of the spanning element was added to it.

completed viaductThe result was a particularly elegant bit of structural sculpture, but one that did have problems.  In the 1990s, concerns about deterioration of the concrete led to a full survey of the structure, which found that the internal strands in the southernmost tendons had been corroded by water infiltration due to flaws in construction that left permeable voids in the concrete jackets.  In 1996 these tendons were supplemented by steel cables grafted onto the outside of the structure:

retrofit sectionIn this diagram, by Profs. Gentile and Martinez Y Cabrera of the Politecnico di Milanoyou can see both the new ‘jacket’ of reinforcing steel and a new steel ‘saddle’ at the top of the tower.  Recent Google Earth imagery shows the condition of this repair recently:

Screen Shot 2018-08-15 at 11.20.47 AM

The tower that collapsed was the one farthest north, where the span switched from the cable-stayed elements to the pure viaduct.  In the one video of the collapse (available elsewhere), the first few seconds appear to show the tower itself collapsing, and while it’s difficult to see through the driving rain, it appears that the deck has already collapsed.  If that was the sequence, it would make sense that the (now gravely unbalanced) tower would become unstable, too.  Coupled with the 1996 repair of the south tower, this suggests an obvious possibility: on a busy afternoon, with a full live load, cables that had been slowly and invisibly corroding finally failed in tension, leading to the collapse of the end of the deck and then the unbalanced tower.

If, in fact, that is what investigators determine, it raises a much larger set of questions, many of which are already being shouted loudly.  The bridge’s condition had, in fact, been the subject of much concern among the pubic and the engineering community–University of Genoa engineering professor Antonio Brencich went on record in 2016 as saying that the bridge was conceptually “bankrupt” and “a disaster waiting to happen,” a seemingly prescient claim that, notably, didn’t suggest what exactly would cause the failure.   Calls for replacement, however, led to political headwinds; the right-wing Five Star party, now in power, has blamed budget limitations imposed by the EU, but in 2014 the party campaigned against replacing the bridge, on the grounds that such a large construction project would only encourage corruption, calling concerns about its collapse a “fairy tale.”

To complicate the politics of the collapse further, the motorway was privatized in the early 2000s, and the concessionaire, Autostrade, has mishandled the aftermath of the collapse horribly, with embarrassing claims that the collapse was simply a natural disaster (there were initial claims that the bridge had been struck by lightning just before the collapse–but this wouldn’t, on its own, have had any effect at all on the structure).  The company had, in fact, been doing foundation repairs on the span on the day of the collapse, part of an unending series of patches.  (Excavations during a torrential rain might suggest that the foundations were undermined, but the apparent sequence from the video and the initial survival of the tower argue against this as a cause).

In all of this, Morandi’s design has largely escaped blame, though it’s worth noting in hindsight that his revolutionary approach to stayed structures may have contributed to the disaster in at least two ways.  First, collecting all of the cable support into monolithic tendons left the structure with no redundancy; if a cable on a typical, fan-shaped stayed bridge deteriorates, there are dozens of others that can carry its load, at least under emergency conditions until it can be replaced.  That wasn’t the case at Polcevera, obviously.  The loss of one tendon necessarily meant the loss of the span.  Second, the concrete cover meant that there was no way to visually assess the state of the steel itself. Corroded or compromised steel cables can be easily spotted and accessed in traditional cable bridges.  But here, it took a full survey in 1996 to determine that there was even the possibility of corrosion.

Still, Morandi was designing in an era where the expectation was that such a bridge would be fully staffed, and its maintenance fully funded over its lifetime.  Deferred maintenance has become the norm in Italy and throughout the developed world, as governments and voters forget that the cost of large infrastructure is just the down payment on life cycle costs that are necessary to maintain structures’ health and integrity.  Houses need new roofs every twenty years.  Bridges need regular monitoring and, often, invasive, surgical repair of corroded or deteriorated pieces.  The running joke in American politics this year has been “Infrastructure Week,” which keeps getting announced and then trampled by more sensational news.  Meanwhile, the American Society of Civil Engineers reported recently that 9% of bridges in the United States–more than 56,000–are known to be “structurally deficient,” most of them due to lack of maintenance.  40% of American bridges are older, in fact, than the Polcevera Viaduct, meaning that whatever the proximate cause of the next large collapse here, no one should be able to get away with saying it was “unexpected and unforeseen,” the terms used, unconvincingly, by Stefano Marigliani, head of Autostrade’s Genoa bureau, to describe the Genoa collapse.

UPDATE (Sept. 6, 2018):  A good overview on the New York Times website today confirms that the collapse began in the southern pair of cable stays and cites the lack of redundancy as a contributing factor…

Image sources:

Gentile And F. Martinez Y Cabrera (Department Of Structural Engineering, Politecnico Di Milano), “Dynamic Investigation Of A Repaired Cable-Stayed Bridge.”  Earthquake Engineering And Structural Dynamics,Vol. 26, (1997). 41-59.

Prof. Ing. Riccardo Morandi, “Viaducto Sobre el Polcevera, en Génova-Italia.”  Informes de la Construcción,vol. 1, no. 200. 57-99.  May, 1968.  Available online at:

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