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PROPOSAL TO CITY OF SANTA ANA PAGE 22 AMENDMENT TO BRIDGE RETROFIT CONTRACT SEISMIC RETROFIT STRATEGY 2. Seismic analysis will follow the procedures as outlined in Caltrans SDC and chapter 20 of the Caltrans Memo to Designers. Effect of the combined structures will be analyzed, and additional retrofit requirement in addition to the bridge widening will be evaluated. 3. Bridge aesthetics of any structure additions as result of the seismic retrofit strategy will /bllow the treatment on the existing structure to the extent possible. 4. Bridge structures will be designed following the latest Caltrans Seismic Design Criteria (SDC). 5. Utility list will be updated at the bridge. No utility relocation or addition of new utility is assumed at this time. For the purpose of establishing a scope of work for the seismic retrofit strategy design, discussed below is a list of possible retrofit elements that are envisaged by the consultant at this time. The proposed work is based on consultant's past experiences working on similar type of structures in a similar environment and geological hazard condition. A. Abutment retrofit will be required due to the high skew of the structure. In addition to the shear keys that will be required to hold the structure securely on the abutment seats, the high skew angle would require the comer with an acute angle to be stabilized with addition of large diameter piles. B. Bent retrofit may be required due to a number of unique conditions of the as-built condition. The bent cap is supported on the pier wall in a "pinned" condition. This creates a pier wall vulnerable to high force at the base of the wall at the connection with the foundation. The lack of confinement reinforcement of the pier walls at the base could render the pier wall vulnerable to failure at the base where short the rebars are lapped spliced with the foundation dowels. C. The same concern with the pier walls could also render the foundation vulnerable. Pier wall foundation is traditionally more vulnerable due to the large transverse responses generated along the pier wall due to the wall stiffness. The skew angle, combined with the pier wall boundary condition, would make the foundation more vulnerable. The list of plans is shown below: TABLE 1- PLAN SHEET No. of Sheet Title Sheets Seismic Retrofit Strategy General Plan 1 Foundation Plans 1 Abutment Retrofit Details Bent Retrofit Details Foundation Retrofit Details Log of Test Borings I Comments Assuming new piles will be required Assuming new piles will be required at bents and abutments Page 5 of 22