고속비상체 충돌에 의한 콘크리트의 손상예측식(수정 NDRC) 적용을 위한 섬유보강계수의 검토

Study of Fiber Reinforced Factor for the Application of the Damage Prediction Formula(modified NDRC) of Concrete due to the Impact of the High-Velocity Projectile

Elements of penetration and scabbing in fracture behavior of concrete subjected to high-velocity impact are compressive strength and flexural-tensile strength respectively. Crack and scabbing of fiber reinforced concrete by high-velocity impact can be suppressed by improved flexural-tensile performance with bridging action of reinforcement fiber. However, since existing NDRC formula mainly considers properties of projectile, impact velocity, and compressive strength as parameter, it is difficult to predict scabbing limit thickness of fiber reinforced concrete with increase of flexural-tensile performance. Therefore, in this study, fracture depth, diameter, and scabbing limit thickness of steel and polyamide fiber reinforced concrete were evaluated by high-velocity projectile impact test, and fracture reduction coefficient according to fiber types and volume fraction was calculated. Also, scabbing limit thickness prediction method was presented by applying modified fracture reduction coefficient to NDRC formula. As results, scabbing thickness and diameter and scabbing limit thickness were suppressed with increasing volume fraction of fiber. Futhermore, it was possible to make accurate prediction for scabbing limit thickness of fiber reinforced concrete by applying modified fracture reduction coefficient to NDRC formula.