The
Dimensions Program
Engineering Marvels Project
Laboratory A
Washington Monument
Figure 1 Washington Monument – Courtesy of U.S. Navy
Project Grant Team
Prof. Karen Gaines
Project Designer
St. Louis Community College
St. Louis, Missouri
Dennis C. Ebersole
Principal Investigator
Northampton Community College
Bethlehem, Pennsylvania
John S. Pazdar
Program Director
Asnuntuck Community College
Enfield, Connecticut
Prof. Shanna Goff
Project Tester
Grand Rapids Community College
Grand Rapids, Michigan
Patricia L. Hirschy
Principal Investigator
Asnuntuck Community College
Enfield, Connecticut
Engineers face many obstacles during the design and construction process. They must work
within the constraints of time, money, physics, location, and often politics. The process evolves
over time with many changes and adjustments happening throughout. The Washington
Monument was no exception for the many engineers involved in its design and construction.
Original Design
The Washington Monument story begins in May of
1783 when Congressman Arthur Lee first proposed a
tribute to George Washington.
•
The initial proposal was a simple and dignified statue
of Washington sitting on a horse. The proposal
passed, but it took more than 60 years before work
moved forward.
Fig 2 Washington D.C.
Courtesy of Lorax
By 1845 a design by Robert
Mills had been chosen. His
design called for a circular
colonnaded pantheon with a 250
ft diameter and 100 ft high.
Above the pantheon roof would
be a huge obelisk with a 70 ft sq
base, a 40 ft sq top and rising
500 ft above the roof.
Fig 3 Washington Monument
Courtesy of Library of Congress
Engineering Marvels – Lab A - 2
Foundation
In 1848, work began on the foundation. It was decided that
only the obelisk (and not the circular colonnaded pantheon)
would be built in phase one.
By 1854 it has risen to 152 ft, but money was running out
quickly and the Civil War was on the horizon.
Fig 4 Partially Completed Monument
Courtesy of Library of Congress, circa 1860
When work started up again after the war, structure safety was questioned. As a result of several
studies, it was concluded that the existing foundation (a truncated square pyramid with an 80 ft
sq base tapering to 58.5 ft at the top with a height of 23.34 ft) would only support a 400 ft shaft.
Also, the top 200 – 250 ft must be constructed of bricks instead of stone to reduce its weight.
In 1878, a lieutenant colonel in the Corps of Engineers took charge of the project and redesigned
the foundation again. His design required removal of 10,334 cu yd of earth from under the old
foundation and replacing it with concrete.
Fig 5 New Foundation Diagram
Courtesy of National Archives
This new foundation was 126.5 ft on a side, which was a big increase from the 6,400 sq ft of the
original foundation. The new foundation, extending 23.5 ft in each direction, allowed for
buttresses to be built for further support.
Engineering Marvels – Lab A - 3
Shaft
While the foundation was being built, engineers had to figure out a method for raising
construction materials up as the monument grew in size.
An elevator was constructed in the
shaft’s center and served as a hoist
not only for stones, but also take
workers to appropriate heights.
Upon construction completion, the
new elevator design would carry
visitors to the monument’s top.
Fig 6 Platform Elevator
Courtesy of Library of Congress
Fig 7 Complete Monument
Courtesy of Wikipedia Commons
Pyramidion
(Square-Based Pyramid)
The final phase would be the pyramidion. Transition from shaft to pyramidion
would be built of marble slabs that were less than 7 in thick. Slabs would rest
on marble ribs (3 on a side) that all converged at the pyramidion top. The
pyramidion’s main part would be a single piece of stone (capstone) with a metal
tip.
The metal apex was 5.6 in on each side of its’ base and
was 8.9 in tall. It was made of aluminum to avoid rust
and also to act as a lightening rod.
The entire pyramidion weighed 300 tons. The capstone
weighed 3,300 lb and the metal apex weighed 100 oz.
Fig 8 Pyramidion Diagram
Courtesy of National Archives
Fig 9 Pyramidion
Courtesy of David Bjorgen
On December 6, 1884, all of the struggles faded into the past as a capstone and metal apex were
set and was officially dedicated in 1885. While it took over 100 years to complete, it is a
testament to the ingenuity of the engineers and workers involved.
Engineering Marvels – Lab A - 4
The
Dimensions Program
Engineering Marvels Project
Laboratory B
Hoover Dam
Figure 1 Hoover Dam – Courtesy of Bureau of Reclamation
Project Grant Team
Prof. Karen Gaines
Project Designer
St. Louis Community College
St. Louis, Missouri
Dennis C. Ebersole
Principal Investigator
Northampton Community College
Bethlehem, Pennsylvania
John S. Pazdar
Program Director
Asnuntuck Community College
Enfield, Connecticut
Prof. Shanna Goff
Project Tester
Grand Rapids Community College
Grand Rapids, Michigan
Patricia L. Hirschy
Principal Investigator
Asnuntuck Community College
Enfield, Connecticut
Just as the Washington Monument required the ingenuity of many talented engineers and
workers, so did the Hoover Dam. The overriding problems in this case, however, were due to
location, geological, and climate issues that arose. The Hoover Dam was constructed due to the
persistence of a few politicians and the visionary leadership of its chief engineer.
Need for a Dam
Flooding or draught and nothing in between; this
was the story of the West in the early 20th century.
As more people were flocking to the western United
States a need to control water supplies became very
important.
Fig 2 Hoover Dam Site
Courtesy of Wikipedia Commons
The main source, the 1,400
mi long Colorado River,
flowed through the states of
Wyoming, Colorado, Utah,
New Mexico, Nevada,
California, and Arizona.
The original series of canals
constructed to supply the
water were causing flooding
so the Army Corps of
Engineers determined that a
dam was necessary.
The task was so
overwhelming, that the
contact was awarded to Six
Companies (a company
formed by six companies
joining forces).
Fig 3 Upper & Lower Basin
Courtesy of Colorado River Commission of Nevada
Engineering Marvels – Lab B - 2
Support System
The engineers had a lot of design and work to do before construction of the actual dam could
begin. In order to transport materials, railroad tracks were laid from Las Vegas to the canyon.
At the peak of construction there were over 5,000 workers, along with their families, that needed
to be housed and fed. Workers were thrilled that cheaply built homes were built for them and
tolerated deplorable temperatures of 110° – 120° F because it meant they had jobs during the
Great Depression.
Prep Work
Four long diversion tunnels were created to temporarily divert the river around the site of the
dam so that a clean and dry base could be established for the construction.
Fig 4 Hoover Dam Diagram Showing Long Diversion Tunnels by Dotted Lines on Top and Bottom 1930
Courtesy of Wikipedia Commons
Work on the four 56 ft diameter, 4,000 ft long tunnels was treacherous as 1,500,000 cu yd of
rock had to be blasted and cleared away. This required setting up scaffolding, performing work,
taking the scaffolding down, and starting over again on the next section. One of the engineers on
site designed a special truck to speed up the process.
Fig 5 Supporting the Tunnel
Courtesy of Bureau of Reclamation
Fig 6 Post-concrete Diversion Tunnel
Courtesy of Bureau of Reclamation
Despite all of the problems (including temperatures over 120° F and high carbon monoxide
levels) the tunnels were dug out by March of 1932 and by October water was being diverted.
Engineering Marvels – Lab B - 3
The Dam
Finally it was time to actually begin construction on the dam itself. The dam is a concrete archgravity type dam with a trapezoidal cross-section 660 ft wide at the base, 45 ft wide at the top,
and 727 ft high. The arch withstands the water pressure the same way an eggshell provides a
surprisingly strong protection for an egg. The dam’s immense weight will hold it in place
against the water’s force.
The concrete would have taken 150
years to cure had it been poured all at
once, so instead concrete was poured
in many vertical interlocking
columns.
Engineers designed a complex cable
system was designed to deliver the
concrete. In order to aid in the
cooling process, cooling pipes were
placed in the concrete.
Later the pipes were filled with
grout to solidify the structure when
the concrete was all poured.
Fig 7 Dam Under Construction 1934
Courtesy Bureau of Reclamation
The dam also included components for
production of power. Four hollow
concrete cylindrical intake towers (each
375 ft tall) were constructed to control
water flow into the power plant.
Inside the power plant are 17 generators
that produce power roughly equivalent
to two nuclear power plants.
Fig 8 Four Intake Towers
Courtesy of Bureau of Reclamation
Finally on February 29, 1936 the Six Companies “turned over the keys” to the government.
Today this grand structure (now called Hoover Dam) stands as a monument to the dedicated
engineers and workers who labored in horrible conditions, during the Great Depression to create
this dam.
Engineering Marvels – Lab B - 4
The
Dimensions Program
Engineering Marvels Project
Laboratory C
Golden Gate Bridge
Figure 1 The Golden Gate Bridge – Courtesy of PDPhoto.Org
Project Grant Team
Prof. Karen Gaines
Project Designer
St. Louis Community College
St. Louis, Missouri
Dennis C. Ebersole
Principal Investigator
Northampton Community College
Bethlehem, Pennsylvania
John S. Pazdar
Program Director
Asnuntuck Community College
Enfield, Connecticut
Prof. Shanna Goff
Project Tester
Grand Rapids Community College
Grand Rapids, Michigan
Patricia L. Hirschy
Principal Investigator
Asnuntuck Community College
Enfield, Connecticut
At approximately the same time the Hoover Dam was being constructed, another major project
was in process in California – the Golden Gate Bridge.
Fig 2 State of California
Courtesy of The General Libraries, The Univ of Texas at Austin
Fig 3 Highlight of San Francisco Bsy Area
Courtesy of Wikipedia Commons
The bridge had to span a fairly inhospitable body of water and withstand the forces of Mother
Nature. The courage of the workers and the design and leadership of a true visionary made the
Golden Gate Bridge construction possible.
Need for a Bridge
In 1848 “Gold Fever” struck in the west. A new breed of people settled in San Francisco causing
a 7,000% increase in population in a very short time. Even with the invention of cars, travel
from one side of the bay to the other could involve an 18-hour trip.
Fig 4 San Francisco Bay
Courtesy of USGS Photo
In 1929, the some people in the area actually allowed liens on their homes to back the bonds for
the project, and the engineers began work.
Engineering Marvels – Lab C - 2
Tower Foundations
The bridge was to be a suspension bridge in which two cables would be draped over two towers.
The towers would be 746 ft tall and weigh 21,500 tons, so a solid foundation was crucial.
North Tower
The tower on the north end was built at the
base of a cliff. A cofferdam (178 ft by 264 ft)
was built by lowering concrete sections into
the water to form a corner and then sinking
steel beams, setting wood braces, and pouring
tons of rock.
The water was then pumped out and the
truncated rectangular pyramid foundation (80
ft by 160 ft at the base, 65 ft by 134 ft at the
top, with a vertical height of 64 ft) was poured
for the north pier.
Fig 5 North Tower
Illustration by Chesly Bonestell
South Tower
The tower on the south end was built 1,125 ft from the shore in the tide-driven waters. The first
step was building a 1,100 ft long trestle (like a long dock) that would reach out to the work site.
Once the trestle was stabilized the work on the tower began.
Engineers first used a 14 in diameter pipe
that was mounted on a barge through which
they dropped a 20 ft long steel shaft with a 2
ft long tapered tip.
The shaft was dropped repeatedly until a
small hole was made into which they
detonated small bombs. Once larger holes
were made, the barge was moved, and larger
bombs were lowered and detonated.
Once the 50,000 cu yd of rock was removed,
a steel guide frame was set to guide the
forms for the concrete.
Fig 6 South Tower Fender
Illustration by Chesly Bonestell
Engineering Marvels – Lab C - 3
Towers and Cables
Each 746 ft tower was then constructed by
creating a series of honeycomb cells that
decreased in dimension as the tower height
increased.
Once the towers were completed, the cables
could be constructed. The wire was strung
and woven into huge cables. Fifty-seven
strands were put together to form a
honeycomb-shaped cable 36 inches in
diameter encased in a steel tube.
The 2 11/16 inches in diameter suspended
ropes were hung in grooves along the cable
(the grooves were cut so that the ropes hung
perfectly vertical). The ropes were hung 50 ft
apart (measured from center).
Fig 7 Cable Construction
Marin Free Library
Roadway
The six-lane (60 ft wide)
roadway and two 10 ft wide
sidewalks was constructed
using 25 ft long stiffening
trusses (two between each
suspender rope) and then
running 90 ft long beams
perpendicular to the trusses.
Fig 8 Roadway Construction
Marin Free Library
Then, as is true now, this beautiful engineering marvel is a monument to the hard working and
never-give-up attitude of the San Francisco area people.
Engineering Marvels – Lab C - 4
The
Dimensions Program
Engineering Marvels Project
Laboratory D
Gateway Arch
Figure 1 Gateway Arch – Courtesy of Daniel Schwen
Project Grant Team
Prof. Karen Gaines
Project Designer
St. Louis Community College
St. Louis, Missouri
Dennis C. Ebersole
Principal Investigator
Northampton Community College
Bethlehem, Pennsylvania
John S. Pazdar
Program Director
Asnuntuck Community College
Enfield, Connecticut
Prof. Shanna Goff
Project Tester
Grand Rapids Community College
Grand Rapids, Michigan
Patricia L. Hirschy
Principal Investigator
Asnuntuck Community College
Enfield, Connecticut
While some structures are built out of practical need, others are built out of a need to celebrate or
commemorate a person, event, or ideal. The Hoover Dam and Golden Gate fall into the former
category, whereas the Washington Monument and the Gateway Arch are two examples of the
latter. The Gateway Arch is a monument that represents the gateway into the western United
States. This incredible structure was the result of a grass roots effort to build a monument in St.
Louis and the design of gifted architect.
Location
In 1764, the village of St. Louis was established by a
group of Frenchman as a fur-trading post.
Its location along the banks of the Mississippi River
and near the Missouri River was ideal for trade. At that
time rivers were the highways of trade.
In the 1940s it was decided that there should be a nation
park honoring the spirit of the settlers and explorers.
On the site a monument would be constructed.
Fig 2 St. Louis on the Mississippi River
Courtesy of Blessed Hope Academy
Design
The architect decided not to make a traditional arch as was often found in Roman architecture,
but rather a catenary curve. This is the shape that would be created by hanging a rope or chain
between two fixed points. The architect simply turned it upside down.
The architect decided on a height of 630 ft so that it
would tower above any other building in the city. For a
bit of artistic symmetry, he decided to make the
distance between its base legs 630 ft, also.
Unlike other structures, this creation would not have
any inner skeletal framework, but the structure would
provide its own support system. The cross-section is an
equilateral triangle. The distance between outer and
inner skins diminished from 3 ft to 7 in and section
sizes diminished from 54 ft on a side to 17 ft on a side
as the structure rose.
Fig 3 The Gateway Arch
Courtesy of National Park Service
Inside the legs, design of an elevator system proved a difficult task. Because of the curved
shape, a standard elevator could not be used, so a system was designed loosely based on a Ferris
wheel idea. Barrel-shaped cars begin at the bottom of the monument suspended from a track.
As the cars climb, they eventually end up on top of the track.
Engineering Marvels – Lab D - 2
Construction
In February of 1963, the foundation was dug and concrete was poured. The engineers had to
make sure the initial leg parts were set accurately. In order for the legs to meet at the top (both
legs were constructed simultaneously) their initial placement had only 1/64 of an inch of
tolerance.
After reaching a certain height, it was
obvious that ground cranes were not big
enough to hoist sections on top of the
existing structure.
Engineers put their heads together and came
up with the idea of creepers. A set of tracks
was mounted on each Arch leg and a derrick
was designed that would move up the track.
Fig 4 Arch Begins to Take Shape
Courtesy of National Park Service
Fig 5 Crane Creeper
Courtesy of National Park Service
Fig 6 Arch Continues to Rise
Courtesy of National Park Service
A total of 142 triangular cross section pieces, each 12 ft high, plus a keystone were used for the
legs. To provide stability, concrete was poured between the metal skin walls, up to the 300 ft
level.
Engineering Marvels – Lab D - 3
At the 530 ft level it was apparent that the
legs could not withstand the creepers
weight.
Engineers designed a truss and it was very
carefully lifted up by the two creepers and
mounted between the legs.
Fig 7 Arch Near Completion
Courtesy of National Park Service
On October 28, 1965 the keystone was set. At
that time the legs were only about 2 ft apart, as
designed.
A jack was inserted to separate the legs to create
an opening wide enough so an 8 ft keystone
could be inserted.
The fire department also had to hose down one
leg so that it cooled and was aligned correctly.
Fig 8 Keystone Installed
Courtesy of National Park Service
Legacy
On a good day, visitors to the Arch can look
thirty miles to see where the settlers and
explorers headed as they braved the
unknown and headed west.
The work by the designers, engineers, and
workers on this and other major engineering
marvels is a testament to the power of the
human spirit and mind to create truly
unbelievable structures.
Fig 9 Gateway Arch
Courtesy of U.S. Air Force
Engineering Marvels – Lab D - 4