Evaluation of Local Effect
Evaluation of local effects consists of estimating the extent of local damage and characterization of the interface force-time function. Local damage is confined to the immediate vicinity of the impact location on the containment shell and consists of missile deformation, penetration of the missile into the shell, possible perforation of the element, and in the case of concrete containment, production of secondary missiles by the dislodging of concrete particles from the back face of the containment (spalling). Due to the complex physical processes associated with missile impact, local effects are evaluated primarily by application of empirical relationships based on missile impact test results.
Concrete containments subject to missile impact are generally required to have a thickness sufficient to preclude spalling. Steel containments, on the other hand, are generally designed to preclude perforation.
There is a significant amount of data on various types of missiles impact tests on different targets [2, 48-54]. This information is useful for local damage assessments for postulated missile impacts on containments as well as for determining interface forcing functions which are utilized in global response evaluations as described below.