The Use and Misuse of Structural Damping in Blast Response Calculations


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Title: The Use and Misuse of Structural Damping in Blast Response Calculations

Author(s): Sam A. Kiger and Hani A. Salim

Publication: Special Publication

Volume: 175


Appears on pages(s): 121-130

Keywords: blast loads; damping; deflection; reinforced concrete

Date: 12/1/1998

This paper investigates the use of structural damping in blast response calculations. In recently published literature, there are many examples of structural damping being used in computational models with little or no experimental or theoretical justification. The use of even small amounts of damping in computational models involving nonlinear plastic response can significantly influence the response calculations. For example, for a given blast loading, a reinforced concrete slab with only 48 kPa maximum capacity and 25 percent of critical damping (a value typically recommended) will deflect the same as (i.e., provide the same level of protection as) a slab with 690 kPa maximum capacity and no damping. Clearly a fictitious damping term that provides as much as 93 percent of the resistance is problematic. Structural damping during plastic response cannot be clearly defined or verified experimentally. Therefore, the use of damping in plastic response calculations should be avoided.