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Determining the effective system damping of highway bridges.

File Language:
English


Details

  • Creators:
  • Corporate Creators:
    University of California, Irvine. Department of Civil and Environmental Engineering
  • Subject/TRT Terms:
  • Publication/ Report Number:
    CA-UCI-2009-001
  • Resource Type:
    Tech Report
  • Geographical Coverage:
    California
  • Corporate Publisher:
    California. Department of Transportation
  • Abstract:
    This project investigates four methods for modeling modal damping ratios of short-span and isolated

    concrete bridges subjected to strong ground motion, which can be used for bridge seismic analysis

    and design based on the response spectrum method. The seismic demand computation of highway

    bridges relies mainly on the design spectrum method, which requires effective modal damping.

    However, high damping components, such as embankments of short-span bridges under strong

    ground motion and isolation bearings make bridges non-proportionally damped systems for which

    modal damping cannot be calculated using the conventional modal analysis. In this project four

    methods are investigated for estimating the effective system modal damping, including complex

    modal analysis (CMA), neglecting off-diagonal elements in damping matrix method (NODE),

    composite damping rule (CDR), and optimization in time domain and frequency domain (OPT) and

    applied to a short-span bridge and an isolated bridge.

    The results show that among the four damping estimating methods, the NODE method is the most

    efficient and the conventional assumption of 5% modal damping ratio is too conservative for short-span bridges when energy dissipation is significant at the bridge boundaries. From the analysis of

    isolated bridge case, the effective system damping is very close to the damping ratio of isolation

    bearing.

  • Format:
    PDF
  • Funding:
    RTA59A0495
  • Collection(s):
  • Main Document Checksum:
    urn:sha256:1b3b3be02adcfe6f8ea29d7555f7a15ca8fc064d60cce7efd3d39b0409ce3d32
  • Download URL:
  • File Type:
    Filetype[PDF - 1.94 MB ]
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