Keywords: dynamics, dynamic amplification factor, assessment dynamic ratio, truss, bridge, probabilistic, assessment, reliability, monitoring, vibration, signal, filter.

In a traditional deterministic assessment, a dynamic amplification factor (DAF) is applied to the static loading in order to account for dynamics. The codified DAF values are appropriately conservative in order to consider the wide range of structures and load effects to which they are applied. In the current analysis, a site specific assessment dynamic ratio (ADR) is calculated from direct measurement on an eighty year old steel truss railway bridge. The ADR is defined as the ratio of characteristic total stress to the characteristic static stress. The application of an ADR is a relatively new concept which has rarely been considered for railway bridges. An assessment performed on the bridge in question showed a decrease in the dynamic allowance when considering the site specific ADR, corresponding to a twenty-six percent decrease in the calculated stress. The measurements available were also used to derive a robust stochastic model for dynamic allowance which considered the correlation between DAF and stress level. The developed model was applied to a probabilistic assessment and resulted in a nine percent increase in reliability.

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