| Abstract: | Full-scale poles, pipes, and rods, representing postulated tornado-borne missiles, were rocket-propelled into reinforced concrete panels with thicknesses typical of walls and roofs in the auxiliary buildings of nuclear power plants. Data from the 18 tests can be used directly for structural design or for validating design and analysis techniques. The test panels, constructed with 3000-psi design strength concrete and minimum allowable reinforcement, were 12, 18, and 24 in. thick with 15 × 15-ft unsupported spans. The results show that a 1500-lb utility pole, 1-in rod, and 3-in. pipe are ineffective for producing significant local and structural damage even under the improbably severe tornado-missile impact conditions represented by the tests. The front several feet of the poles disintegrated upon impact without damaging the face of the panels. Although 12-in. pipes produced craters in the face of the panels, impact tests with these missiles showed that 18-in. thick walls are adequate for preventing backface scabbing (secondary missiles) in the highest tornado-intensity region of the US, while 12-in. thick walls are adequate in other regions. Data on penetration depths and scabbing thresholds for 12-in. pipe impacts could be fitted reasonably well only with a modified NDRC design formula. Examination of structural response was aided by electronic records of reaction forces, missile deceleration, panel velocity, and strains during impact. Contrary to the predictions of conventional structural design methods, which do not account for missile deformation, no overall permanent deflections of the panels were produced by any of the missiles. |
