PUNCHING FAILURE OF A REINFORCED CONCRETE SLAB DUE TO HARD MISSILE IMPACT (IRIS_2010 CASE)

摘要

In the framework of the design of nuclear facilities reinforced concrete structures have to be assessed concerning their robustness against impacts of different kinds of either externally or internally generated missiles. Experimental results are required for the validation of analysis methods that are used for the assessment of impact events.Currently, medium scaled impact tests are carried out by VTT in the framework of an international research project called IMPACT. There is also an on-going OECD project called IRIS_2010 in which three different types of tests are benchmarked by a wide international community. Missile impacts are usually classified as either "hard" or "soft" according to the missile's deformability. They may give rise to phenomena of localized target damage such as punching as well as global dynamic flexural response of the target.The present paper describes three nearly identical repetitions of a hard missile impact test included as a blind benchmark case in IRIS_2010 project. The 0.25 m thick square slab was simply supported on all four edges with a span of 2 m and reinforced with longitudinal bending bars. No transverse shear reinforcement was provided. In all these tests, successfully conducted at VTT, the missile perforated the slab. Very similar punching behaviour of the slab was observed.This benchmark test was analysed by several authors, who all are members of the IMPACT project, using complex computer codes as well as simplified analytical methods. The test was simulated in a blind analysis without knowing the test results beforehand.The comparative analyses show that the complex analysis methods employed are able to predict the mechanical behaviour of reinforced concrete structures subjected to hard missile impact, such as perforation, but they are very sensitive to certain parameters partly with physical and partly with numerical relevance. The methods, codes and computational capacity allow very sophisticated and detailed simulations, but more experience in using the7se varying methods and better understanding of the physical phenomena is needed among their users.