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 <http://www.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

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