The Seismic Retrofit of Marquam Bridge a Case Study


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Title: The Seismic Retrofit of Marquam Bridge a Case Study

Author(s): Renzo Medeot

Publication: Special Publication

Volume: 164


Appears on pages(s): 529-544

Keywords: Bridge bearings; dynamic structural analysis; earthquake-resistant structures; energy dissipation; shock-mechanics; dumping; structural analysis; tests.

Date: 11/1/1996

The seismic retrofit project of the Marquam Bridge in Portland, Oregon is the first example, in the United States, of the application of high dissipative capacity isolators in conjunction with shock transmitters. This technique was developed and has been vastly applied to the seismic engineering of bridges in Italy during the last twenty years. After a brief description of the structure, the paper lists the seismic requirements of the structure and illustrates the design approach adopted. It then describes the model used for the time history, step-by-step non-linear analysis and comments on the results obtained. The latter demonstrate that the utilization of the above mentioned devices has permitted ensuring complete anti-seismic protection for bridges without the need to strengthen existing structural elements, particularly piers and foundations. In other words, the seismic demand has been reduced below the actual capacity of the structure. In conclusion, the paper describes in detail the testing procedures, the acceptance criteria and the results of the five different severe tests: two for the shock-transmitters and three for each type of isolator. The tests were conceived so as to simulate both, long term service actions and seismic attack conditions and necessitated the use of specialized equipment.