3rd International Conference on PROTECTION OF HISTORICAL CONSTRUCTIONS

Lisbon, Portugal, 12 – 15 July, 2017

PRESERVATION OF HISTORICAL BRIDGES IN USA: THE GOLDEN GATE BRIDGE AND THE

ALBION RIVER BRIDGE CASES

Abolhassan Astaneh-Asl*

* University of California, Berkeley, USA e-mails: Astaneh@Berkeley.edu

Keywords: Golden Gate Bridge; Albion River Bridge; Experimental testing; Seismic retrofit; Steel bridges; Timber bridges.

Abstract. The Golden Gate Bridge opened to traffic in 1937, is located between two major and active seismic faults, the San Andreas Fault, capable of creating an M8.3 earthquake, and the Hayward Fault capable of creating an M7.3 earthquake. The bridge is only 16 km from San Andreas and 11 km from the Hayward faults. The main challenges in seismic retrofit of this iconic and historical bridge were: (a) to establish the strengths of the critical components of the bridge; (b) to design seismic retrofit concepts that will enable the bridge to withstand its maximum credible earthquake, and; (c) most importantly, to ensure that the historical appearance of the bridge is preserved. The author of this keynote paper, who has been closely involved with the project, discusses critical aspects of these three important items. The Albion River Bridge has a length of 302 meters, opened to traffic in 1944, and is a fine example of a historical timber bridge and one of the last remaining engineered timber bridges in California. The bridge is located in Northern California about 10 km to the east of the San Andreas Fault capable of creating M8.3 earthquakes. The bridge is currently in very fine condition, however, since 2013, the State Department of Transportation has intensified its efforts to demolish the bridge and replace it with a reinforced concrete bridge. The majority of local residents opposing the demolition invited the author to investigate the condition of the bridge and to assess its seismic safety and needs for retrofit. The paper discusses the results of this investigation and how the efforts helped to register the bridge as a U.S. National Historic Place with the Federal Government.

1 INTRODUCTION

In the United States, the main vehicle to preserve historical buildings, bridges, and other structures is through the use of National Register of Historic Places (NRHP) [1], which is a Federal program of National Park Service of the Department of the Interior [1]. The NRHP is based on the 1966 National Historic Preservation Act passed by U.S. Congress as Public Law 102-575 [2]. In the United States, the National Register of Historic Places is the official list of the Nation's historic places worthy of preservation. Authorized by the National Historic Preservation Act of 1966, the National Park Service's National Register of Historic Places is part of a national program to coordinate and support public and private efforts to identify, evaluate, and protect America's historic and archeological resources.[2].”

In order for a property in a State to be on the list of National Register of Historic Places, it has to be nominated by property owner, an agency, a historical society or by any individual by filling out a standard form available at [2, 3] and submitting it to the Office of Historic Preservation of the state that the property is located in. Then the SHPO notifies the property owner of the filing of the application and asks for input and comments. Regardless of how the property owner responds or replies at all, the State Office of Historic Preservation proceeds with the review of the application and solicits public comments on the registration and prepares a case for consideration of the State Historic Preservation Commission. After the nomination is approved by the State Commission, the recommendations are submitted by the

 

 

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ft). The structure has six lanes of car and truck traffic with two pedestrian lanes one on each side of the bridge. Although Joseph Straus was the Chief Engineer of the bridge in charge of its design and construction, Leon Moisseiff is credited with the most graceful aspect of the bridge which is its single suspension span. Charles Alton Ellis was the main engineer of the bridge and Irving Morrow designed the architectural aspects of the main towers. The stunning suspension concept of the bridge designed connecting the north side of the San Francisco to the Marin County to the north.

Even before the design of the Golden Gate Bridge started, historical preservation was a major consideration. The alignment of the bridge was passing over the Fort Point, which is a fort built before the Civil War between 1853 and 1861, more than 70 years before the construction of the Golden Gate Bridge started. Currently, the Fort Point is a U.S. National Historic Landmark. At the time of design of the Golden Gate Bridge, an arch bridge was designed over the Fort Point, Figure 1(a), to cross over the historical building.

2.1 Structure of the Golden Gate Bridge and its current condition

The Golden Gate Bridge, shown in Figure 1(b) on the previous page, consists of three distinct segments: the San Francisco approach structures, the Marin approach structure and the main suspension bridge. The two main towers of the suspension spans consist of two multi-cell steel tower legs connected to each other by horizontal trusses above the deck and cross bracings below the deck. The cross-section of the towers is formed with 1 meter (3-1/2 ft) square cells and the base of each leg is 15 cells long and nine cells wide. The cell walls at the base of the tower are 22mm (7/8 inch) thick silicon steel plates. As the tower approaches the top, the cross-section is reduced by reducing the number of cells until only 21 cells remain at the top. At the top of the towers, the suspension cables pass through a cable groove on the saddle. The cables are tied down to the concrete pylons at each end and are connected to the anchorages. The suspended bridge is connected to the shore by two approach structures. The Marin approach has a series of five 53.4-meter (175 ft.) deck truss spans supported on high, four-legged steel towers. The San Francisco approach has one two-hinged arch over the historical fort, two 38.1-meter (125 ft.) deck truss spans supported on two steel towers, one 53.4-meter (175 ft) deck span, and three 21.7-meter (71 ft.) plate girder spans.

2.2 Seismic response of the Golden Gate Bridge and seismic retrofit needs

The Golden Gate Bridge being a long period structure is particularly sensitive to two phenomena: (a) the near-field velocity pulse [4], and (b) the long period component of the far-field strong motions [5]. The first phenomenon, the near-field velocity pulse, results in permanent displacement at the site of the structures located near the ruptured fault. Due to velocity pulse, larger forces and displacements can be generated in the structures [4]. However, this phenomenon is not currently considered in the seismic design of bridges. The second and equally important phenomenon is the effect of long distance earthquakes on long period structures, such as the Golden Gate Bridge. This phenomenon also is not generally considered in the seismic design.

In recent years, the author has undertaken several projects [5], focusing on studying the effects of long-distance earthquakes on long-span bridges and tall buildings, both having long periods of vibration. When a fault ruptures, the ground motion moving away from the ruptured fault becomes weaker but its period of vibration is elongated. When the long period surface waves arrive at the site of a long period structure such as the Golden Gate Bridge, even though the amplitude of the ground motion is relatively small, because of its period is close to the period of the structure, the response of the structure can be quite large. Figure 2

 

 

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RIDGE

is located alifornia Hi

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has been donke to prevenwers of the odel of the Ato conduct

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lhassan Astaneh

9

in northernighway-1, oPacific Oc

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ment of Trending the bearings of tnt of future bridges in spans. The

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Abolhassan Astaneh-Asl

 

 11

California to supply steel for the bridge, the only items they received was two steel trusses, recovered from an old railroad bridge and some railroad rails and a limited amount of rebars. The steel trusses were used in the main span over the river. The rails were used as longitudinal rebars in the columns and rebars were used in various concrete elements. This connection of the Albion River Bridge to World War II has made the bridge significant as far as the U.S. history is concerned and satisfies the Criterion (a) mentioned in the previous page. The bridge also satisfies the Criterion (b) of the National Register of Historic Places as given in the previous page since it is one of the last remaining “well-engineered” timber bridges in California, and probably in the U.S. and represents a type, period, or method of construction that is no longer used.

4.2 Historical Registration of the Albion River Bridge

In 2015, a National Register Form was filed by John Johansen, a local architect, to register the Albion River Bridge as a United States National Historic Place. After more than one and a half year review of the application, the California Office of Historic Preservation [3] placed the case of the Albion River Bridge historical registration on the May 10, 2017 meeting agenda of the State Historical Resources Commission and asked for public comments. The author prepared a 14-page letter in support of the application and submitted it to the Commission, attended the meeting of the Commission and made in-person public comments in support of the application. At the meeting, the Commission unanimously approved the Albion River Bridge to be listed in the U.S. Register of National Historic Places and forwarded its recommendations to the Department of the Interior for final approval. 4.3 Challenges faced in historical registration of the Albion River Bridge

The efforts to register the Albion River Bridge as a National Historic Place has been quite challenging, though at the end, very rewarding when the bridge was registered. The main challenge and difficulty was that the California Department of Transportation (Caltrans),the state agency that owns, maintains, and operates the Albion River Bridge, not only was not supporting the historical registration efforts but appeared to be determined to push for demolition and replacement of this perfectly fine historic bridge in a very good condition and replace it with a reinforced concrete bridge. Caltrans was giving numerous reasons for replacement in its reports, such as, “the timber deck is rotten and crushing”, “the bolts are corroding”, “the steel truss has corrosion”, “the treatment material of the timber is releasing arsenic to the environment”, “the tsunamis can collapse the bridge”, “the cost of maintenance justifies spending more than $50 million to replace the bridge “, and several other reasons. The author using the results of his 3 years of investigation of the condition of this bridge, in his letter to the Historical Preservation Commission showed that none of the above-mentioned reasons are true and the bridge is in very good condition.

The main reason for demolition was given by Caltrans was that the timber deck of the Albion River Bridge “was rotten and crushing”. Under pressure from the Albion Community members and the author, in 2015 Caltrans materials laboratory did conduct actual in-situ tests and laboratory tests of the deck core samples and concluded that the deck, in fact, is in very good condition and is not rotting nor crushing. The corrosion of steel elements also proved to be not true and not a justifiable reason to demolish a perfectly fine historical bridge. The corrosion of galvanized bolts can be managed by proper maintenance of the bridge and by replacing the corroded bolts with better galvanized modern bolts that resist corrosion better.

Abolhassan Astaneh-Asl

 

 12

5 CONCLUSION

1. The tests reported in this paper formed the basis of the seismic retrofit of the critical elements of the Golden Gate Bridge, which were the main stiffening truss and the base of the main towers. In both cases, the problem was that the truss chords and the base of the tower had relatively high width-to-thickness ratios, resulting in a very brittle local buckling of these elements under compression.

2. The local buckling problem of the main truss chords of the Golden Gate Bridge could not be retrofitted with the economy. Therefore, by using hydraulic dampers between the main trusses and the tower legs, the seismic forces expected during the future strong earthquakes were reduced and the local buckling of the truss chords prevented.

3. The tower legs of the Golden Gate Bridge do not have anchor rods to connect them to the foundations. As a result, during a major earthquake, the tower legs of the bridge are expected to uplift and compress down on the caisson foundations. Under the compression, the plates at the base of the tower legs can buckle locally prior to ductile yielding. The towers were retrofitted to prevent the local buckling by bolting vertical wide flange stiffeners to the mid-width of the plates. The tests summarized in this paper showed that the retrofit measure was able to prevent local buckling and enable the plates to reach their capacity in compressive yielding and have sufficient ductility.

4. Registering the Albion River Bridge as a U.S. National Historic Place was very challenging although eventually successful. The State Department of Transportation, the owner of the bridge, was not supporting the historical registration. The State Department of Transportation was and still is pushing for the demolition of this perfectly fine historically significant bridge and wants to replace it. This case showed that through the efforts of the Community and fact-based data supplied by the author, it was possible to stop the transportation agency from the demolition of a valuable historical bridge.

6 REFERENCES

[1] NRHP, “National Register of Historic Places”, website, National Park Service, Department of the Interior, Washington D.C., 2017.

[2] ACT, “National Historic Preservation Act of 1966 as amended through 1992, website, Public Law 102-575,16 U.S.C. 470, Passed by Congress, 1966.

[3] COHP, “California Office of Historic Preservation”, website, State of California, 2017.

[4] McCallen, D. Astaneh-Asl, A., and Larsen, S., “Seismic Studies of the San Francisco-Oakland Bay Bridge”, Proceedings of the 12th World Conference on Earthquake Engineering, Auckland New Zealand, (Paper # 2792), 8pp, 2000.

[5] Astaneh-Asl, A., “Seismic behavior and earthquake design of long-period structures”, Proceedings of the 5th International Conference on Structural Engineering, Mechanics and Computation, Cape Town, South Africa, (5-7/16), 81-424, 2012.

[6] Ingham, T.J., Rodriguez, S., Nader, M., and Taucer, F. “Seismic retrofit of the Golden Gate Bridge”, Proceedings of the 11th World Conference on Earthquake Engineering, Acapulco, Mexico, (Paper # 1396), 8pp, 1996.

[7] Cho, S-W., Astaneh-Asl, A., and Blondet, M., “Post-buckling ductility of critical members of the Golden Gate Bridge”, Report No. UCB/CEE-Steel-93/01, Dept. of Civil and Environmental Engineering, University of California, Berkeley, 1993.

[8] Bowen, C.M., and Astaneh-Asl, A., “Buckling Behavior of the Tower Legs of the Golden Gate Bridge”, Report No. UCB/CEE-Steel-96/07, Dept. of Civil and Environmental Engineering, University of California, Berkeley, 1996.