Seismic Damping Effects on Bridges

The American Association of State Highway and Transportation Officials (AASHTO) Guide Specifications for Load and Resistance Factor Design (LRFD) Seismic Bridge Design currently allow for increased structural damping to be used in certain cases for the analysis and design of bridges, due to soil-structure interaction at integral or semi-integral abutments. This increased damping, from an equivalent viscous damping ratio of 2%–5% up to potentially as high as 10%, can work out to as much as a 24% reduction in structural design loads, which is substantial and could be advantageous to highway bridge designers. The AASHTO possibility of using increased bridge damping for integral abutment bridges does not yet appear to include any potential benefit from friction damping due to the connected structural approach pavements (“approach slabs”) sliding on their bearing pad support atop the foundation (at an expansion joint, away from the bridge) or by sliding over the subbase—however, these effects could be significant. It is also unclear whether such damping can be effectively mobilized in both the longitudinal and transverse directions of a bridge (perhaps in conjunction with wingwalls). This project will investigate and answer the key questions outlined above through a series of nonlinear time history structural analyses of representative Illinois Department of Transportation highway bridges. Comparisons will also be made to simpler linear models with 5%–10% viscous damping. The overall research objectives are to determine the extent to which increased damping from all sources can be relied upon when designing integral abutment bridges against seismic effects as well as to recommend what damping coefficient value can be applied.

Language

• English

Project

• Status: Active
• Funding: $281586
• Contract Numbers:

  R27-257

• Sponsor Organizations:

  Illinois Department of Transportation

  Bureau of Materials and Physical Research
  126 East Ash Street
  Springfield, IL  United States  62704-4766
• Managing Organizations:

  University of Illinois, Urbana-Champaign

  Illinois Center for Transportation
  1611 Titan Drive
  Rantoul, IL  United States  61866
• Principal Investigators:

  LaFave, James

  Fahnestock, Larry

• Start Date: 20240101
• Expected Completion Date: 20251231
• Actual Completion Date: 0

Subject/Index Terms

• TRT Terms: Abutments; Bridge design; Damping (Engineering); Earthquake resistant design; Highway bridges; Load and resistance factor design; Structural analysis
• Subject Areas: Bridges and other structures; Design; Highways;

Filing Info

• Accession Number: 01903883
• Record Type: Research project
• Source Agency: Illinois Department of Transportation
• Contract Numbers: R27-257
• Files: RIP, STATEDOT
• Created Date: Jan 2 2024 10:03AM