The Empire State Building
Hoover Dam


Regency Skyway Disaster

Tacoma Narrows Bridge




The Empire State Building

    Construction of the Empire State Building began in March of 1930 at the site of the old Waldorf-Astoria Hotel at 350th Avenue and 34th Street in New York City.  It was completed 14 months later in May 1931, and was the world’s tallest building at the time (for 40 years, until 1972 when the 1st tower of the World Trade Center was constructed) standing an astounding 1,453 ft - 8 9/16th in (102 stories).  The Empire State Building became the tallest building by overtaking the height of the Chrysler building in New York by 407 feet. 

    The Empire State Building is a great engineering achievement because of the overall size of the building.  It was not only the tallest building ever built in 1931, but remained the tallest for 40 years.  Modeled after a pencil, the design was believed to be better in the wind and only deflects approximately 1.48 inches in 110 mph winds.  The American Society of Civil Engineers also considers the building as one of the 7 Modern Civil Engineering Wonders.

Below is a list of facts about the Empire State Building:
Total cost (including land):  $40,948,900  
Architects:  Shreve, Lamb & Harmon Associates
Builders:  Starrett Brothers & Eken, Inc.
Managing Agents: Helmsley Spear, Inc.

For more information on the Empire State Building, please visit [1]:


Hoover Dam

     Hoover Dam was without precedent, the greatest dam of its day; it is still a world-renowned structure. Located in Black Canyon between Nevada and Arizona, the dam is a National Historic Landmark and a National Historic Civil Engineering Landmark. In 1994, the American Society of Civil Engineers named it one of America's Seven Modern Civil Engineering Wonders.      

Construction of Hoover Dam began in 1931, and the last concrete was poured in 1935 - 2 years ahead of schedule.  The power plant wings were completed in 1936, and the first generator began operation in October of that year. The 17th and final generator went into commercial operation in 1961. Hoover Dam's reservoir, Lake Mead, is America's largest man-made reservoir and can store 28.5 million acre-feet (9.2 trillion gallons!) of water, or nearly 2 years of the river's average annual flow.   

    The power plant located with the dam, is one of the largest in the world.  From 1939-1949, the dam had the largest hydroelectric installation at 2.08 million kilowatts, and is still one of the country’s largest power suppliers.  Today, with 17 large turbines, the power plant has a total horsepower output rated at 2,998,000 hp.  This provides the generation of low-cost hydroelectric power for use in Nevada, Arizona, and California. The Hoover Dam alone generates more than 4 billion kilowatt-hours a year- enough to serve 1.3 million people.

    During the construction of the Hoover Dam, tunnels were dug to divert the water around the construction site.  Tunnels were used to divert water flow during construction. Four tunnels were dug, each 56 feet in diameter and a total length of about 3 miles (16,000 ft). For nearly two years, the Colorado River flowed unchecked through the diversion tunnels. Cofferdams were built in 1934 at the entrances to tunnels 2 and 3, those closest to the river. Concrete plugs 405 feet thick were dovetailed into the tunnels, closing the bores forever.  Tunnel 1 was plugged in the winter of the same year; with 6-foot diameter holes left in the plugs and sealed off with gate valves.  In 1935, a huge steel gate weighing more than 1000 tons was lowered over the entrance to tunnel # 4. By opening the valves in plug #1, sufficient amounts of water were released downstream while the waters of the Colorado River began to back up behind Hoover Dam to form Lake Mead. For the first time in history, the Colorado River was under man's control. [2]

Hoover Dam Statistics

Structural Height:  726.4 ft.
Base Width:  660 ft.
Crest Length:  1244 ft.
Crest Width:  45 ft.
Volume of Concrete:  4.4 million cubic yards.

View plan of Hoover Dam



Regency Skyway Disaster

    On July 17, 1981, the Hyatt Regency Hotel in Kansas City, Missouri held a dance party, which resulted in tragedy.  The second and fourth floor walkways collapsed due to a structural failure, which killed 114 people and left around 200 injured.  The incident is the most devastating structural failure in terms of lives lost in the United States.

    The failure was caused during the design stage when there was miscommunication between the fabricator (Havens Steel Company) and the engineering team (G.C.E International, Inc.).  Plans were changed by the fabricator, which doubled the load on the supporting box beam.  Another reason for the collapse was the negligence of the working conditions by the engineers. They should have been able to realize the mistake by the fabricator, and estimate an applied load that would accommodate almost any social function that would take place in the hotel.  As a result many people were killed and the engineering team lost their professional licenses.  

For more detailed information and photographs visit [3]:



Tacoma Narrows Bridge

Tacoma Narrows’ Bridge constructed in 1940 is considered a major failure in Civil Engineering and changed the designs of every preceding bridge. Built as a logical path between the eastern shores of Puget Sound and the Kitsap Peninsula it would open up a new commercial market. The Tacoma Narrows Company set out to build the bridge suffered both financially and environmentally in the construction process. Financially from the fact the United States was in an economic slumber and governmental funds were difficult to obtain. While environmentally from the terrain the bridge connected. The bridge design was significantly influenced by the deep and swift moving Tacoma Narrows’ water, which suggested that a long-span suspension structure was the only practical bridge to span the channel. It was 5,939 feet in length; the main span was 2,800 feet and was only stiffened with eight-foot plate girders because it was much narrower than most bridges with a width of 39 feet. With a longer span, a shallow depth, and a narrow width, the bridge was much more flexible than any other bridge built in that time. Four months into operations, a 42-mile-per-hour wind side-walled the bridge and sent it into a violent oscillation dubbing it "Gallping Gertie". The reason as to why the bridge went into to a disastrous oscillation can be modeled and argued on many levels, however some of the more predominant reasons can be listed as follows: 

1. "The collapse was not do to the brute force of the wind but due to the resonance between the natural frequency of oscillation of the bridge and the frequency of the wind-generated vortices that pushed and pulled alternately on the bridge structure."

 2. "...vortices were pouring off the top and bottom of the bridge, driving at its resonant frequency, which eventually led to its collapse." 

3. "Thus vortex shedding allows us to understand the origin of the fluctuating vertical forces on the Tacoma Narrows Bridge." [4]  

    However technical expert, K. Billah and R. Scanlan, posses a different point. They disputed the idea of the bridge natural frequency reaching its resonant frequency leading to the violent oscillation. They proposed the failure of the bridge is directly related to the aerodynamic induce condition of self-excitation or ‘negative damping’ in a torsional degree of freedom. The aeroelastic phenomenon involved was an interactive one in which developed wind forces were strongly linked to structural motion. The street of vortices, which bordered the top and both, fluttered the bridge deck sideways simultaneously with vertical undulations. From fall of the Tacoma Narrows bridge, every bridge that was constructed from that point on were designed and tested using wind tunnels. Aerodynamic data are collected and factored in to the model to test the aeroelastic strength of the structure, which is assumed to be a bluff (non-streamline) body. As a result majority of bridges today are unaffected by side force winds or any opportunity to oscillate. 

Movie of Tacoma Narrows oscillation