On the
Bridge
A Paper
By Sean
Vitousek
The Bixby Creek Bridge of Highway 1 is
California’s favorite coastal bridge. The bridge is
technically sound, but more than being thoughtfully
planned and well constructed; it is socially purposeful
and symbolically important to its travelers. Building the
bridge and Highway 1 were important public works projects
which brought relief to California’s unemployed during
the Great Depression, and which today connects travelers
though this dramatic coastal region. This setting makes
the projects’ environmental concern and aesthetics
important to avoid detracting from the natural beauty of
the region. While works of humans are often looked down
upon by environmentalists, the bridge rises above these
issues in its true concern for nature, and gives
travelers a new perspective of nature viewed from above.
This bridge not only connects travelers to their
destination, but connects travelers with nature.
Connecting
California’s Coast
The California coast with its purple
mountains dropping off into the sea is the end of the
nation and the destination of historical westward travel
by early pioneers. As California matured and grew in
population, transportation engineers conceived a route
running directly along the coastline to best serve the
purpose of connecting California’s coast. This route,
Highway 1 has become the symbol of the California coast.
The highway serves purposes above and beyond those of the
classic highway which provides a commercial network,
linking goods and persons to their destinations as
quickly and efficiently as possible. This classic purpose
is aptly demonstrated by Inter-state 5, build on level
terrain in California’s central valley and better suits
high-speed transportation. Highway 1 on the other hand is
unsuitable of mass transit because of its geographic
characteristics; elevated, meandering and dramatic.
Through accommodating and accentuating these
characteristics into the design of Highway 1 a much
different purpose is attained. Highway 1 serves to
connect and conduct travelers though and to the natural
and cultural environments in a manner perhaps more
spiritual than commercial. As a journalist affirmed,
“Traveling Highway 1 is more than just a scenic drive,
it’s a pilgrimage, a reconnection to California’s
history, environment, mythology – its spirit.” Due to its
character Highway 1 serves to uphold “the spirit” of this
coastline.” And there is no better example of this spirit
in practice than the design and construction of the Bixby
creek bridge.
Building the
Bridge
The completion of a coastal highway
depended on spanning five canyons, one of which was Bixby
Canyon. The construction of the Bixby Creek Bridges and
Highway 1 to the south exemplifies an approach to these
natural ‘obstacles’ that gave the greater highway project
identity and purpose and demonstrated the designers’ and
builders’ great care of the environment.
The first engineering concern was assessing
how the highway would cross Bixby Canyon. The options
were either a coastal bridge or a much smaller inland
bridge and a 900 ft tunnel cutting though the Santa Lucia
Mountain Range at the valley’s origin. This tunnel would
not allow for scenic views, and would align Highway 1 in
a way that would cut directly though the Los Padres
National Forest, which local environmentalists wished to
preserve. A bridge was a worthy option in the eye of
these environmentalists as it preserved one area of
resource value and did not adversely impact on Bixby
Canyon or Creek. In doing so it became a symbol of
passing above the environment, and of accomplishing a
practical objective while still allowing the
environmental processes such as the creek to run their
natural course.
The next decisions were what kind of bridge
to design and where it should be located relative to the
coastline. An arch bridge serves an aesthetic purpose as
it heightens the affect of rising above the environment
and reflects contours of the canyon. The decision to
locate the bridge directly on the coast would help to
define the rest of the Highway 1 project (completed after
Bixby Bridge) as well as remain essential in its
environmental concern. Near the coast, erosion and the
coastal environment limit the further growth of forests
like the inland forests the environmentalists wanted to
preserve. As a coastal project was desirable in the eyes
of both the developers and environmentalists, the way was
clear for Highway 1.
The final decision was what material should
be used in construction of this bridge, steel or
concrete. The decision to make the bridge out of concrete
reflected both economic and aesthetic concerns. A steel
bridge would cost more to build, be negatively affected
by fog and salt spray and require expensive maintenance
and painting. A rusting steel bridge would not be in
harmony with the rest of the verdant environment.
Building the bridge out of concrete would provide much
less of an industrialist contrast (which steel would
have) to the natural environment and echo the color and
composition of the natural rock cliff formations of the
area. Although the Gustav Eiffel’s steel Garabit Viaduct
on the Thuyere River in France contrasts nicely with its
surrounding environment, its ‘poinsettia’ red color seems
to standout against rather than harmonize with its
setting which detracts from the overall aesthetics.
In 1931, CH Purcell, the California state
highway engineer and FW Panhorst, the bridge engineer and
designer were given the job of making the project a
reality. The bridge contract was awarded to the Ward
Engineering co. of San Francisco for $203,334 and
concrete placing began on Nov 4. Wooden false work, built
up 240 ft from the floor of the creek, provided support
for the arch’s concrete as it was hardening. Ocean swells
pounded this false work and delayed the bridges
completion until the winter swells passed highlighting
how close this bridge is to the ocean. Upon its
completion the bridge, costing $199,861, had the longest
concrete arch span, 320 ft, on the California State
Highway System and a rise of 120 ft. The bridge’s
roadway: 714 ft long (only 45% of it lies above the arch)
and 24 ft wide, cost $11.66 per square foot, which seems
economic considering all the structure that supports it.
The arch supports a live load of these 2 lanes of traffic
at 640 lb./ft each and a dead load of the combined masses
of all concrete used in the arch (per total length). All
together the bridge needed to support a load of 28700
lb./ft*. Because the bridge is an arch bridge much of
this load is carried to the sides of the canyon. The
equations that govern the vertical and horizontal forces
are:
Vertical Force, V = qL = 28700(320) =
4,600,000 lb.
2 2
Horizontal Force, H = qL2 = 28700(320)2 =
3,061,333 lb.
8d 8(120)
From these forces we can determine the
stress, f, put on the arch at midspan by the
equation:
f = H = 1530666.5 = 472.4 psi
A 3240*
-Where H = the horizontal force (in lb.)
and A = the cross-sectional area (in sq. in.)
-As you can see the H in the stress
equation is half that of the initial H. This is because
the bridge has two arches which support the load
equally.
And from the stress put on the system we
can calculate the safety factor:
Safety Factor, SF = fc = 3000 = 6.35
f 472.4
-Where fc is the breaking stress of
concrete 3000 psi and f is the actual stress of the arch
(in psi)
This safety factor says that it can support
more than 6 times as much weight as it was designed to
support and is considerably ‘safe.’
Social
Concerns
Highway 1 and its five bridges were popular
since their construction 1931-1937. These large scale
construction projects acted as a major benefit to the
population suffering from the great depression. Public
works projects created jobs and provided significant
relief from the decline in private development caused by
severe economic downturn.
Preservation of the natural and cultural
environments is an important social concern. This is the
premise of the National Environmental Policy Act of 1969,
which required all public development projects to be
supported by an Environmental assessment and/or an
Environmental Impact Statement which assesses the
potential negative effects the project may have on the
environment. The primary purpose of this act is to
‘encourage productive and enjoyable harmony between man
and his environment.’ Although the bridge was completed
almost 40 years prior to the passage of this act, the
bridge exemplifies how early and thorough consideration
of these environmental concerns and values, promotes the
‘productive and enjoyable harmony between man and the
environment.’ Today Bixby Bridge and Highway 1 connect
travelers to Big Sur’s beaches, state parks, mountains
and National Parks, and do so without detracting from
their natural beauty. In fact, the people of the Pelican
network believe that as Highway 1 reveals Big Sur’s
beauty, and creates in travelers a sense of
environmentalism compelling them to preserve this
beautiful environment.
On the Road, On
the Bridge
The bridge and the road have become
symbolic of the California coast and its beauty. Jack
Kerouac represented this beauty in his book Big
Sur, where he speaks of his escape to Lawrence
Ferlinghetti’s cabin in Bixby Canyon, to escape his
problems of alcoholism and city life. Upon his night
arrival to the bridge, Kerouac notices ‘an awful roar of
surf but it isn’t coming from the right place, like you’d
expect it to come from ‘over there’ but it’s coming from
‘under there’ (pg. 9). This quote begins to show
Kerouac’s awe of Bixby and Big Sur and how the bridge may
from his perceptions. During his stay, Kerouac has a
series of primal visions of the environment some of which
are characterized by literary critics as ‘nightmarish’.
But these visions are finally righted in Kerouac’s ending
of Big Sur, where he finally states his belief that ‘To
be afraid of nature is to be afraid of yourself’. And
despite his ‘nightmarish’ experiences, he finds salvation
if only for a brief moment in Bixby Canyon. Unfortunately
his salvation was short lived as he drank himself to
death five years later at the age of 47. Kerouac’s
literary works and the spirit of Kerouac live on. Kerouac
was a traveler. Many of his literary works reveal his
travels across America. In a sense Kerouac was a new
pioneer for the traveling lifestyle of seeking new
experiences on the road. This notion parallels that of
early westward pioneers, who set off on their travels
across America to explore the land and the environment.
Such travels represent discovery; Kerouac’s travels
represent self discovery. Each traveler also represents a
connection with nature as their life changing experiences
come from their journey in nature. The California coast
was a significant place for these travelers, as it was
their destination. The spirit of the coast is enriched by
such historic and significant travelers, and today
travelers cannot help but feel the effect of this
spirit.
On the
Bridge
The Bixby Bridge is aesthetically pleasing;
it combines a picturesque setting with form. It is
interesting to look at how the bridge achieves such
aesthetics and compare its effect to similar bridges.
The five major bridges along Highway 1 all
have similar design, with the Bixby Creek Bridge and
Rocky Creek Bridge having the most surprising similarity.
Each is a single span with 2 parallel arches connecting
to large abutments extending down into the walls of the
canyon. The bridges are criticized for having these
abutments as they are practically nonfunctional. These
large abutments used medieval architecture provided
increased support for the arch pushing outward. Yet as
the arches of Bixby and Rocky Creek Bridge are supported
by the walls of the canyon, no extra horizontal backing
is necessary. The Russian Gulch Bridge of Northern
California, another coastal arch bridge demonstrates
this, as it does not have such abutments. Despite their
structural function (or non-function), the abutments have
aesthetic functions as do the other thinner supports.
Bixby and Rocky have 10 evenly spaced column supports
from their arch to their roadway, and supports outside
the arch of longer (yet still even) spacing than that of
the supports between the abutments. The Russian Gulch has
supports of gradually increasing distance apart from each
other (16-20 ft) from the center outward. This
practically even spacing without abutments creates a
uniform look in the bridge, which does not divert
attention to any particular feature. Where as the effect
of the abutments create a frame diverting attention to
and emphasizing the concentrated supports over the arch
and the arch itself. This, in my opinion, seems to be a
reasonable purpose as the arch is the premiere aesthetic
feature.
The dimensions of the arch also play a
major role in the aesthetics of a bridge. The only major
noticeable difference between Bixby and Rocky other than
the size is the span to rise ratio. Bixby’s ratio of 2.66
gives a much higher look while Rocky’s ratio of 4 is more
spread out. Figure # shows Bixby Bridge with different
arches.
Arch 1 is a longer spanning, lower rise
bridge which gives it a streamlined look. Arch 2 is the
Bixby’s current arch. And Arch 3, draw to simulate a high
rising bridge, is not as aesthetically pleasing as the
other two as it seems bulky, unnatural and exaggerated
especially in a natural environment. Arch 1 is similar to
Rocky creek but more so resembles the Swiss bridges of
Robert Maillart, most closely the Salginatobel Bridge.
This bridge has a sleek streamlined look, which looks
light in contrast to its surroundings, whereas many
bridges appear massive. This bridge has thin, evenly
spaced supports extending outward, and would certainly
not produce a streamlined effect if it had bulky
abutments. I believe that as the bridge gets higher and
narrower; abutments become increasingly acceptable,
because they lose a streamline look and gain a towering
look as abutments enhance the effect of height. The Bixby
Bridge uses the effect of diverting attention to its
heightened arch, and still does not unnaturally contrast
or detract form the its dramatic environment. As it
combines all aspects of purpose and beauty, it is truly
California’s favorite coastal bridge.
Works cited list:
1. Leger, Mark. “Roadway to California’s
Spirit.” Gorp.com
<http://www.gorp.com/gorp/activity/byway/ca_hwy_1.htm>
(Nov. 21, 2001)
2. Mitchell, Stewart. Engineering
News-Record, “A 320-Ft. Concrete Arch on Scenic Route
Along California Coast” April 13, 1933, pp 467-470
3. Gallagher, James. California Highways
and Public Works, “Longest Concrete Arch in State Among
Carmel Coast Link Bridges” Nov. 1931, pp. 34-35
4. Billington, David P. The Innovators.
“Modern Engineering and the Transformation of America,”
John Wiley and Sons, Inc. New York, 1996
5. Ellwanger, Jack. “Highway One in Big
Sur.” Pelicannetwork.net
</hwy.one.bigsur.htm>
6. Kerouac, Jack. Big Sur. Penguin Books,
New York, 1962
7. Kupahal, Henry E. Civil Engineering,
“Simplicity Marks Esthetic California Bridge” Nov 1945,
pg 536
8. Asher, Levi “About: Big Sur” <
http://www.poembeat.com/asher.htm>
To contact the author Sean
Vitousek
11-15-01