• Advances in concrete construction
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• v.7 no.1
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• pp.23-30
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• 2019

Five key items were used to create an economical and physically small impact test device for concrete panels subject to high speed collision: an air-compressive system, carbon steel pipe, solenoid valve, carrier and carrier-blocking, and velocity measurement device. The impact test device developed can launch a 20 mm steel spherical projectile at over 200 m/s with measured impact and/or residual velocity. Purpose for development was to conduct preliminary materials tests, prior to large-scale collision experiments. In this paper, the design process of the small impact test device was discussed in detail.

• Steel and Composite Structures
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• v.44 no.2
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• pp.225-240
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• 2022

Local responses of steel plate-concrete composite (SC) walls under impact loads are typically evaluated using design equations available in the AISC N690s1-15. These equations enable design of impact-resistant SC walls, but some essential parts such as the effects of wall size and shear reinforcement ratio have not been addressed. Also, since they were developed for design basis events, improved equations are required for accurate prediction of the impact behaviors of SC walls for beyond design basis impact evaluation. This paper presents a numerical study to construct a robust numerical model of SC walls subjected to impact loads to reasonably predict the SC-wall impact behavior, to evaluate the findings observed from the impact tests including the effects of the key design parameters, and to assess the actual responses of full-scale SC walls. The numerical calculations are validated using intermediate-scale impact tests performed previously. The influences of the fracture energy of concrete and the conservative aspects of the current design equations are discussed carefully. Recommendations are made for design practice.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.3
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• pp.576-585
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• 2002

A three-dimensional Lagrangian explicit time-integration finite element code for analyzing the dynamic impact phenomena was developed. It uses four node tetrahedral elements. In order to consider the effects of strain rate hardening, strain hardening and thermal softening, which are frequently observed in high-velocity deformation phenomena, Johnson-Cook model is used as constitutive model. For more accurate and robust contact force computation, the defense node contact algorithm was adopted and implemented. In order to evaluate the performance of the newly developed three-dimensional hydrocode NET3D, numerical simulations of the oblique impact of mild steel plate by mild steel sphere were carried out. Ballistic limit about various oblique angle between 0 degree and 80 degree was estimated through a series of simulations with different initial velocities of sphere. Element eroding by equivalent plastic strain was applied to mild steel spheres and targets. Ballistic limits and fracture characteristics obtained from simulation were compared with experimental results conducted by Finnegan et al. From numerical studies, the following conclusions were reached. (1) Simulations could successfully reproduce the key features observed in experiment such as tensile failure termed "disking"at normal impacts and outwards bending of partially formed plus segments termed "hinge-mode"at oblique impacts. (2) Simulation results fur 60 degrees oblique impact at 0.70 km/s and 0.91 km/s were compared with experimental results and Eulerian hydrocode CTH simulation results. The Lagrangian code NET3D is superior to Eulerian code CTH in the computational accuracy. Agreement with the experimentally obtained final deformed cross-sections of the projectile is excellent. (3) Agreement with the experimental ballistic limit data, particularly at the high-obliquity impacts, is reasonably good. (4) The simulation result is not very sensitive to eroding condition but slightly influenced by friction coefficient.

• Journal of the Korea institute for structural maintenance and inspection
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• v.19 no.6
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• pp.55-62
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• 2015

An importance of infrastructures' protection against crash or blast loading has been an emerging issue as structures are becoming much bigger and population densities in downtown are growing up. However, there exists no such a standard to evaluate the protection performance of construction material itself. Prior to building standards for protection assessment techniques, this study performed gas-gun propelled projectile impact tests with series of contact-type monitoring systems to investigate the applicability of each sensing type. Through the impact tests, failure modes and protection performances of both normal concrete and UHPC (Ultra High Performance Concrete) reinforced by steel fibers were also evaluated. The results showed that LVDT could be applicable for the impact test among contact-type sensors and UHPC with fibers had a remarkable potential to improve protection against impact loading.

• Nuclear Engineering and Technology
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• v.54 no.10
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• pp.3745-3765
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• 2022

The concrete structures related to nuclear safety are threatened by accidental impact loadings, mainly including the low-velocity drop-weight impact (e.g., spent fuel cask and assembly, etc. with the velocity less than 20 m/s) and high-speed projectile impact (e.g., steel pipe, valve, turbine bucket, etc. with the velocity higher than 20 m/s), while the existing studies are still limited in the impact resistant design of nuclear power plant (NPP), especially the primary RC slab. This paper aims to propose the numerical simulation and theoretical approaches to assist the impact-resistant design of RC slab in NPP. Firstly, the continuous surface cap (CSC) model parameters for concrete with the compressive strength of 20-70 MPa are fully calibrated and verified, and the refined numerical simulation approach is proposed. Secondly, the two-degree freedom (TDOF) model with considering the mutual effect of flexural and shear resistance of RC slab are developed. Furthermore, based on the low-velocity drop hammer tests and high-speed soft/hard projectile impact tests on RC slabs, the adopted numerical simulation and TDOF model approaches are fully validated by the flexural and punching shear damage, deflection, and impact force time-histories of RC slabs. Finally, as for the two low-velocity impact scenarios, the design procedure of RC slab based on TDOF model is validated and recommended. Meanwhile, as for the four actual high-speed impact scenarios, the impact-resistant design specification in Chinese code NB/T 20012-2019 is evaluated, the over conservation of which is found, and the proposed numerical approach is recommended. The present work could beneficially guide the impact-resistant design and safety assessment of NPPs against the accidental impact loadings.

• Structural Engineering and Mechanics
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• v.32 no.5
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• pp.685-699
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• 2009

Current research and development of high performance concrete, together with study of phenomena that are pertinent to impact resistance, have lead to a new generation of barriers with improved properties to resist impact loads. The paper reviews major properties and mechanisms that affect impact resistance of concrete barriers as per criteria that characterize the resistance. These criteria are the perforation limit, penetration depth and the amount of front and rear face damage. From the long-known, single strength parameter that used to represent the barriers' impact resistance, more of the concrete mix ingredients are now considered to be effective in determining it. It is shown that the size and hardness of the aggregates, use of steel fibers and micro-silica have different effects on performance under impact and on the resistance. Additional pertinent phenomena, such as the rate and size effects, confinement and local versus global response, are pointed out with their reference to possible future developments in the design of impact resisting concrete barriers.

• Computers and Concrete
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• v.12 no.1
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• pp.37-51
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• 2013

The responses of reinforced concrete slabs subject to an impact loading near the ultimate load range are explored. The analysis is carried out on a simply supported rectangular reinforced concrete slab using a nonlinear explicit dynamic procedure and considering three material models: Drucker-Prager, modified Drucker-Prager, and concrete damaged plasticity, available in the commercial finite element software, ABAQUS/Explicit. For comparison purposes, the impact force-time response, steel reinforcement failure, and concrete perforation pattern are verified against the existing experimental results. Also, the effectiveness of mesh density and damage wave propagation are studied independently. It is shown that the presently adopted finite element procedure is able to simulate and predict fairly accurate the behavior of reinforced concrete slab under impact load. More detailed investigations are however demanded for the justification of effects coming from an imperfect projectile orientation as well as the load and structural surface conditions, including the impulsive contacted state, which are inevitable in an actual impact environment.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.158-159
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• 2017

In this study, it evaluate the strain properties of fiber reinforced concrete and fiber reinforced cement composite. The types of fiber are Hooked steel fiber and it was mixed 0.5, 1.0 vol.% in concrete and 1.0, 2.0 vol.% in cement composites. The impact test was conducted by using a projectile (diameter: 25mm, velocity: 170m/s) and strain properties on the rear side of each specimen was evaluated by strain gage. After the impact test, fracture grade, fracture depth was evaluated.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.10a
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• pp.37-38
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• 2016

In this study, it evaluate the coarse aggregate mixed effect to impact resistance performance of the fiber reinforced cement-based material. The type of fiber is Hooked-ended steel fiber, and mixed 1vol.% in concrete and cement composites. The impact experiment was conducted by using a spherical shape projectile diameter of 25mm to 170m/s speed and Impact resistance performance was evaluated by measuring the fracture grade, fracture diameter and depth.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.37 no.4
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• pp.269-273
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• 2014

The objective of this study is to safety assessment for human body on the guided missile combustion products. This study is to verify the safety assessment when operating the interior missile ejection take on verify the safety of the human body. During the missile ejection of combustion products, this study is analyzed combustion products. Result are accepted NIOSH and KOSHA of the safe guideline, and 6 exposure gas to the specified values 42% (CO), 22% ($CO_2$), not detected (others) are within minimal exposures criteria of the reference value respectively. Contribution of these results supported that interior missile ejection during combustion products may have been ensured human safely. Therefore, the future for improving the environmental safety of the shooting projectile steel plate round, dust collector, ventilation and other facilities is to improve environmental safety and efficient renovated design needed by target focused areas.