Influence of fire damage on the modal parameters of a prestressed concrete double‐tee joist roof

SUMMARY This paper examines the influence of fire damage on experimentally measurable modal parameters to explore the potential role of vibration-based structural identification in post-fire condition assessment. Experimental modal analysis of a precast, prestressed concrete roof comprised of modular double-tee joists was performed following exposure to an accidental fire. Empirical evidence of localized structural degradation is identified in the mode shapes, which suggests that modal parameters are sensitive to fire-induced damage in prestressed concrete members. Additionally, measured out-of-plane global modes are correlated with finite element simulations using a model of the as-built roof as well as a model updated using a large set of impact-echo measurements across the double-tee roof to spatially map localized reductions in stiffness. The comparisons support the experimental conclusions and further demonstrate that, by coupling nondestructive techniques, it is possible to construct a validated analytical model of structural components with sufficient fidelity to assess suitability for rehabilitation and reuse. With further development, vibration-based monitoring and structural identification may be an attractive alternative to physical load testing, particularly when the risk of structural collapse under proof testing loads is high. Copyright © 2014 John Wiley & Sons, Ltd.

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