Structural Engineering
Loads

Earthquake Load - Countries prone to earthquakes must design their structures with this as a primary concern.

Southern California - This bridge collapsed during an earthquake.

Earthquake Engineering

John Hancock Centre in Chicago showing the massive crossbeams and tapering design which enable it to resist earthquakes and winds of up to 132 miles per hour by having the forces absorbed by all three dimensions of the building.

Trivia - Wall climber "Spider" Dan Goodwin successfully scaled the John Hancock Centre in 1981 using suction cups. The Chicago Fire Department was not amused.

Light arches in Seattle

(photo courtesy of Dr. R. Loov)

 Wind Load - Sometimes structures must be designed to withstand high winds.

In a huge wind storm, a bridge that is not well designed against wind load can start to bounce and eventually will collapse like the Tacoma Narrows Bridge in Seattle.

The bridge was too flexible. It started to move up and down in waves as traffic crossed it. A wind storm caused the waves to increase in strength and eventually the bridge collapsed.

More about the Tacoma Narrows Bridge failure
Soil Movement -

Soil settlement in one side only beneath the Pisa Tower in Italy. It still tilts more and more every year. They are using counter weights to reduce this increase in tilt. (photo courtesy of Dr. R. Loov)

Civil engineers learn from these mistakes. For the CN tower in Toronto, they rested its foundation on a strong soil base 15m beneath the ground surface. It needed 62000 tons of soil excavation to achieve this. The CN tower is 553 m high, was completed in 1975. It opened June 26, 1976 and was considered the world's tallest free-standing for that time.

Did you know that Canada once had its own "leaning tower"?

Load - Hydrostatic pressure of the water against the upper face of the dam.

The arch dam is used in tall rocky gorges and is curved facing the reservoir so as to transmit the major part of the water load to the abutments and to keep the masonry joints closed tight.

The Hoover Dam was built 1931-1936, 7 miles northeast of Boulder City Nevada on the Colorado River. It is a concrete masonry thick arch.
photos courtesy of United States Department of the
Interior Bureau of Reclamation - Lower Colorado Region
History of the Hoover Dam

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