Many empirical formulas have been proposed for evaluating local damage to reinforced concrete structures caused by impacts of rigid missiles. Most of these formulas have been derived based on tests involving impact perpendicular to target structures. Thus far, few tests with oblique impact onto target structures have been carried out. In this study, we aim to propose a new formula for evaluating the local damage caused by oblique impact based on previous experimental and simulation results. In this study, we perform simulation analyses for evaluating the local damage to reinforced concrete panels subjected to oblique impacts by soft missiles under various impact velocities by using a simulation method that was validated using the results of previous impact experiments. Based on the results of these simulation analyses, quantitative evaluation of the reduction in local damage due to the difference in impact angle and impact velocity is investigated.
Most impact research has been presented on the basis of impact tests and numerical analysis performed by rigid projectile impact perpendicular to the target structure. On the other hand, there are only few reports on impacts at an oblique angle. To evaluate more realistic conditions regarding issues related to oblique impacts to reinforced concrete (RC) structures, we have proposed an analytical method to estimate the local damage to RC structures by oblique impact and have validated the evaluation approach by comparison with experimental results. At present, we have finalized simulation analyses of oblique impact assessments on RC panels using rigid/soft projectiles with flat nose shape utilizing the validated approach. In this study, we focus on impacts caused by rigid/soft projectiles with hemispherical nose shape. The same analytical method is applied to simulate the structural damage of the RC panel due to rigid/soft projectile with hemispherical nose shape. Results on the penetration depth of the RC structure and the energy-contribution ratio are presented. By comparing the results of local damage to RC structure caused by projectiles with flat and hemispherical nose shapes, the influence of the nose shape of projectile on local damage of RC panel has been investigated.
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.
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.
In case of a projectile impact on a reactor building of a nuclear power plant, stress waves propagate from the impacted wall to the structure’s interior. It is important to assess the effect of dynamic responses generated by the projectile’s impact on internal equipment, because stress waves are likely to excite high-frequency vibrations of internal equipment. The OECD (Organization for Economic Co-operation and Development) / NEA (Nuclear Energy Agency) launched the IRIS (Improving Robustness Assessment Methodologies for Structures Impacted by Projectiles) benchmark project in order to assess the dynamic response of a nuclear facility to projectile impact, and the third phase of IRIS (IRIS 3) [1] contributes to the investigation of the dynamic responses of reinforced concrete (RC) structures that house internal equipment. We have participated in IRIS 3 and have performed calibration analyses of projectile impact tests on a structure that models a reactor building that houses internal equipment. Specifically, we have developed and validated a numerical approach to investigation of impact responses of an RC structure that houses internal equipment through calibration correction. This paper presents partial simulation results of the dynamic responses of this structure and discusses the effects of support conditions of the internal equipment and stress wave propagation.
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