Most empirical formulas were proposed to evaluate the local damage to reinforced concrete (RC) structures based on impact tests conducted with a rigid projectile at an impact angle normal to the target structure. Only a few impact tests were performed involving a soft projectile. Therefore, in this study, we conducted a series of impact tests to evaluate the local damage to RC panels subjected to normal and oblique impacts by rigid and soft projectiles. This paper presents the test conditions, test equipment, test results, and obtained knowledge on local damage to RC panels subjected to normal and oblique impacts.

The influence evaluation against projectile impacts has attracted much attention for the safety assessment of nuclear-facility buildings subjected to projectiles, such as tornado missiles or aircraft. Many experimental studies have been reported on the impact resistance of reinforced concrete (RC) structures. Based on these results, many empirical formulas for penetration depth, scabbing limit thickness, and perforation-limit thickness have been proposed for the local damage evaluation. However, most formulas were derived from impact tests based on normal impact to target structures using rigid projectiles that do not deform during impact. Therefore, this study develops a local damage evaluation method considering the rigidity of projectiles and oblique impacts that should be considered in realistic projectile impact phenomena. Specifically, we focused on scabbing, defined as the peeling off the back face of the target opposite the impact face, and conducted impact tests on RC panels to clarify the scabbing limit by changing the impact velocity in an oblique impact. The effects of the projectile rigidity and oblique impact on the scabbing limit were investigated based on the test results. This work presents the test conditions, equipment, results, and the scabbing limit on the local damage to RC panels subjected to oblique impacts.

The basemat uplift is a phenomenon that the bottom of the basemat of a building partially rises from the ground due to overturning moments and vertical motions during earthquake. The degree of the basemat uplift can be indicated using a ground contact ratio which is defined as a ratio of the contact area of the bottom of the basemat to its entire area. The problem is that, at a large earthquake, the basemat uplift becomes large, so-called low ground contact ratio state, and the basemat falls resultant to recontact between the basemat and the ground, and large acceleration response occur on the floor of the building. It is a crucial aspect in the seismic evaluation of a nuclear facility building. It affects not only structural integrity of the building but also the response of the equipment installed in the building. However, the building behavior under the low ground contact ratio state lacks sufficient study. In this study, we conducted seismic response analyses for the building using a three-dimensional finite element model and simulated shaking table experiments focused on the basemat uplift and confirmed the validity of this analysis method. Since the basemat uplift is a strong non-linear phenomenon, we conducted computer simulations under the same analysis conditions with three different analysis codes, namely E-FrontISTR, FINAS/STAR, and TDAPIII, and compared the results. We investigated the influence on the structural response caused by the difference of the adhesive force of the basemat and the bearing ground at the low ground contact ratio state. In addition, we studied the influence of numerical parameters to the structural response through sensitivity analyses. This paper reports the analysis results and the insights obtained from our investigations.

This study aims at proposing a numerical analysis method to evaluate local damage to reinforced concrete (RC) panel caused by projectile impact. To validate the proposed numerical analysis method, we recently conducted a series of impact tests with normal and oblique impacts due to rigid and soft projectiles. We intend to compare the numerical results with experimental results including reaction forces, damage modes of RC panel and soft projectile in oblique impact. In the numerical analysis for evaluation of local damage to RC panel, there are several key parameters, such as material properties, contact conditions between concrete and projectile. In addition to these parameters, we also focused on the reaction forces of RC panel, which is important when investigating the impact effects on structure under projectile impact. Since the stiffness of support structure is represented as a spring element in finite element (FE) model, we examined the relationship between the spring stiffness and numerically computed reaction forces in oblique impact. The numerical analysis method for oblique impact is validated, and the local damage in the RC panel is evaluated, by comparing experimental and numerical results.

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