Great Moments in Structural Engineering | Letters | Chicago Reader

Great Moments in Structural Engineering 

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To the editors:

As a licensed structural engineer I wish to thank Geoffrey Johnson for his lengthy story on the Masonic Temple (September 11, 1987). I do wish, however, to make some comments on the article from a professional point of view on behalf of the Structural Engineers Association of Illinois (SEAOI).

One particular sentence caught my eye. "In 1869 [John Wellborn] Root graduated from New York University with a degree in civil engineering." However, throughout the article he is continually referred to as an architect.

Many of the architectural giants of this period, including Root and William Le Baron Jenney (the father of the modern skyscraper) and later, Frank Lloyd Wright, had strong engineering background and experience.

When you discuss tall buildings you ought to focus on engineering (not architecture) because tall buildings are basically engineering achievements. The Masonic building and other tall buildings were made possible because designers of this period understood structural engineering principles.

This was the era of the master builder; a person trained in the arts (architecture) as well as the sciences (i.e. structural engineering).

It is interesting to note that in today's complex society major changes have taken place in the way tall buildings are designed. Today's young architects are trained with only rudimentary skills in engineering. These architects devote most of their time to appearances and functions. While this is significant a major design parameter is missing. Structural engineers are retained by architects to design the structural framework so modern high rises can stand up. Simply put, today's skyscrapers could not stand without the structural engineer's design. Most journalists when discussing architecture ignore the significant contributions of the structural engineering professional to the design of major buildings and structures.

This is why your story interested me. Basic elements of engineering were addressed and the fact that Mr. Root originally was trained as an engineer even though he practiced architecture.

On the other hand, I wish you would have spent less time discussing various architectural concepts and spend more time discussing engineering principles which differentiated the Masonic Temple from other buildings of the period. In particular, I wish you would have discussed how the structural framework made possible modern high-rise structures.

Among engineers, William Le Baron Jenney's Home Insurance Building (1884) is generally considered to be the first true skyscraper. (Not the Montauk building of 1882, as you noted.) This is so because the Home Insurance Building employed a structural frame to transfer forces to the foundation. With Jenney's Home Insurance Building, a skeletal frame was employed as the structural support system. (See Chicago Tribune Sunday Magazine, October 26, 1986, "Way We Were.")

In modern skyscrapers, steel, concrete, or a combination of both are used to transfer loads. Reinforced masonry may also be used as a structural material.

During Root's professional career masonry structures, as you remarked, were the primary method of supporting loads. One of the last of these tall masonry structures to be constructed was the Monadnock Building (1891). Do you know the masonry walls of the Monadnock Building are six feet thick! The introduction of the structural frame made the structural design concepts of the Monadnock Building obsolete.

Structural frames as used by Root in the Masonic Temple made its record height possible. While you discussed the materials involved in the design of this and other buildings no engineering concepts of the frame were addressed. Graphic representation of frame action might have been used to communicate these ideas to the layman. From the Masonic Temple, to the Flat Iron Building, to the Woolworth Building, on to the Chrysler Building, and finally with a culmination in the Empire State Building, the structural steel frame grew to astonishing heights, then no innovations occurred for over 30 years.

It took another giant in the engineering community to spark interest in the tall building. From the time of John Wellborn Root to the 1960s structural materials were improved but engineering concepts employed in the design of structural frames remain unchanged: Enter Dr. Fazler Rahman Khan (1929-1982), from Skidmore, Owings & Merrill, Chicago, and with the Dewitt Chestnut Apartment Building, Chicago, structural engineer Khan showed the engineering world that a tubed frame (in this case of concrete) could be used to resist lateral loads. (See Technique and Aesthetics in Design of Tall Buildings edited by David P. Billington and Myron Goldsmith.)

At this time it should be noted the wind loads (applied horizontally) are the primary forces governing tall building design. In earthquake zones such as California, it is earthquake loads (again loading applied horizontally) which control the frame design.

In Khan's tubed structure closely spaced exterior columns were used to resist wind loads. Later, Khan tied nine of these tubed structures together and what resulted was the current record holder for tall buildings, the Sears Tower.

So from Jenney, to Root, to Khan with many unnamed structural engineers in between, the tall building continues to evolve, and who gets all the credit--the architects! Many journalists fail to recognize that the structural framework is the foundation from which all great architecture springs forth.

Paul Gapp, Chicago Tribune architectural critic, years ago wrote: "Structural engineers play a major role in the visual quality of our built environment, yet they seldom get public recognition for it. Skyscrapers are a prime example of this. Engineers create framing systems that give such buildings their shape and permit the manipulation of spaces and functions. Architects sometimes do nothing more creative than gussy up the exterior with a particular kind of curtain wall." (See Chicago Tribune, August 10, 1980.)

In discussing the 190 S. LaSalle building and architect, Phillip Johnson and you totally ignored the structural engineer's contribution to the project.

For the record, the 190 S. LaSalle building was structurally designed by the office of Cohen Barreto Marchertas, Chicago, and represents a new trend in structural frame design. Though not the first, the 190 S. LaSalle building has a hybrid structural frame, consisting of both concrete and steel. Wind (lateral) loads are resisted by concrete walls (shear walls) conveniently located around the elevators within the interior of the building. Gravity loads (vertical loads) are resisted by steel columns around the perimeter of the tower. This type of frame, sometimes referred to as the "Denver Frame" where it originated, has gained acceptance by several engineering firms as an economical and rapid method of constructing tall buildings. Therefore, I would have to disagree with your statement that there was nothing innovative structurally with the 190 S. LaSalle project.

In 1986 the Structural Engineers Association of Illinois (SEAOI) recognized the 190 S. LaSalle project with an award of merit for its structural design.

I suggest you walk past the 35 N. Wacker Building to observe a "Denver Frame" project currently under construction. Not surprisingly this building is also structurally designed by Cohen Barreto Marchertas.

But as I close this letter, I wish to return to Root's structural engineering and the "Masonic Temple."

Your article has showed your readers and me the origins of today's high-rise buildings.

Chicago architects (and let's not forget the structural engineers) have been in the forefront of skyscraper design. One hundred years ago Chicago was showing the way to the future with its innovative structures as the Masonic Temple.

Today some of the most significant structures are located in Chicago.

1. Sears Tower, world's tallest building, bundled steel tube.

2. Water Tower Place, currently world's tallest all-concrete building, concrete tube.

3. 311 S. Wacker (under construction) will be world's tallest concrete building when completed.

4. Amoco Building, fourth tallest building in the world, steel tube framing.

5. Hancock Building, fifth tallest building in the world, diagonalized exterior braced tube.

6. Lake Point Tower, world's tallest apartment building, concrete shearwall.

7. 10 and 30 S. Wacker, the Chicago Mercantile Exchange Center, 40-story office building with 38' story--32' long cantilever (see Paul Gapp, Chicago Tribune, March 25, 1984, "A Master Piece of Engineering").

8. 900 N. Michigan (under construction), novel 69-story concrete and steel mixed-use building, 39 floors of concrete supported by 30 floors on structural steel.

9. Onterie Center, apartment building, diagonalized framed concrete tube, 1986 SEAOI Best Structure.

10. 10 S. LaSalle, 40-story office building, "Denver Frame." Existing foundations and first five floors of previous building's exterior cladding salvaged and incorporated into new building. SEAOI 1987 Most Innovative Structure.

Suggested reference: A Review of Structural Systems in Recent Chicago High Rises, unpublished thesis of William C. Moy, University of Illinois at Chicago, College of Architecture, June 1987.

These projects and many others too numerous to mention have made Chicago the architectural showcase of the world. But let us not forget the engineering, and the unrecognized structural engineers behind these architectural treasures.

It would be refreshing to see a feature story focusing on the engineering of Chicago's well-known buildings. If there is any interest in the subject, SEAOI could put you in contact with the engineers who designed these structures. Chicago's structural design heritage is rich, a fact often overlooked by the press.

Once again, thank you for shedding some light on the origins of the tall modern building.

Robert B. Johnson

Public Relations Chairman

Structural Engineers Association of Illinois


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