Modified empirical formulas for predicting the thickness of RC panels under impact loading

Thai, Duc-Kien,Kim, Seung-Eock,Bui, Tinh Quoc Elsevier 2018 Construction and Building Materials Vol.169 No.-

<P><B>Abstract</B></P> <P>Most existing empirical formulas available in the current literature do not take into account the effect of reinforcement in predicting penetration depth and perforation thickness of reinforced concrete (RC) panels subjected to impact loads. In this paper, novel modified empirical formulas are proposed for better prediction. For the purpose of this study, finite element (FE) simulation using a commercial software LS-DYNA is employed. A nonlinear model of materials involving the strain rate effect is considered. Recent impact test results are used for the validation of FE results. Parametric analysis with different longitudinal and shear rebar ratios is then performed to investigate their influence on the penetration depth and perforation thickness of RC panels and to derive the modified empirical formulas. It is shown that the proposed formulas accurately predict the penetration depth and perforation thickness of the RC panels subjected to the impact with velocities in the range of 50 m/s–250 m/s.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Novel modified formulas for predicting of RC panel thickness are proposed. </LI> <LI> Effects of reinforcement on RC panel thickness are taken into account. </LI> <LI> Parametric investigation is carried out using numerical simulation. </LI> <LI> A number of experimental data are also used for the purpose of this investigation. </LI> </UL> </P>

Numerical simulation of reinforced concrete slabs under missile impact

Thai, Duc-Kien,Kim, Seung-Eock Techno-Press 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.53 No.3

This paper presents a numerical analysis of reinforced concrete slabs under missile impact loading. The specimen used for the numerical simulation was tested by the Technical Research Center of Finland. LS-DYNA, commercial available software, is used to analyze the model. The structural components of the reinforced concrete slab, missile, and their contacts are fully modeled. Included in the analysis is material nonlinearity considering damage and failure. The results of analysis are then verified with other research results. Parametric studies with different longitudinal rebar ratios, shear bar ratios, and concrete strengths are conducted to investigate their influences on the punching behavior of slabs under the impact of a missile. Finally, efficient designs are recommended.

Numerical simulation of reinforced concrete slabs under missile impact

Duc-Kien Thai,김승억 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.53 No.3

This paper presents a numerical analysis of reinforced concrete slabs under missile impactloading. The specimen used for the numerical simulation was tested by the Technical Research Center ofFinland. LS-DYNA, commercial available software, is used to analyze the model. The structuralcomponents of the reinforced concrete slab, missile, and their contacts are fully modeled. Included in theanalysis is material nonlinearity considering damage and failure. The results of analysis are then verifiedwith other research results. Parametric studies with different longitudinal rebar ratios, shear bar ratios, andconcrete strengths are conducted to investigate their influences on the punching behavior of slabs under theimpact of a missile. Finally, efficient designs are recommended.

Safety assessment of an underground tunnel subjected to missile impact using numerical simulations

Duc-Kien Thai,Duy-Liem Nguyen,Thanh-Tung Pham,Thai-Hoan Pham 사단법인 한국계산역학회 2021 Computers and Concrete, An International Journal Vol.27 No.1

This work presents a safety assessment of an underground tunnel subjected to a ballistic missile attack employing the numerical approach. For the impact simulation, a box shaped reinforced concrete (RC) structure with a cross section dimension of 8.0×10.0 m under a soil layer that was attacked by a SCUD missile was modeled using finite element (FE) software LS-DYNA. SCUD missile is one of a series of tactical ballistic missiles developed by Soviet Union during the Cold War, which is adopted for a short-range ballistic missile. The developed FE simulation for the penetration depth of the missile impacting into the soil structure was verified from the well-known formula of the penetration prediction. The soil-structure interaction, the soil type, and the impact missile velocity effects on the penetration depth of the missile into the different soil types were investigated. The safety assessment of the underground tunnel was performed with regard to the different depths of the underground tunnel. For each missile velocity and soil type, a specific depth called the unsafe depth was obtained from the analysis results. The structure beneath the soil beyond this depth remains safe. The unsafe depth was found to be increased with the increasing missile velocity.

Numerical Study on Nuclear Building under Aircraft Impact

Thai Duc Kien,Lee, Hyuk kee(이혁기),Kim, Seung Eock(김승억) 대한토목학회 2013 대한토목학회 학술대회 Vol.2013 No.10

Empirical evaluations for predicting the damage of FRC wall subjected to close-in explosions

Duc-Kien Thai,Thai-Hoan Pham,Duy-Liem Nguyen,Tran Minh Tu,Phan Van Tien 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.49 No.1

This paper presents a development of empirical evaluations, which can be used to evaluate the damage of fiberreinforced concrete composites (FRC) wall subjected to close-in blast loads. For this development, a combined application of numerical simulation and machine learning approaches are employed. First, finite element modeling of FRC wall under blast loading is developed and verified using experimental data. Numerical analyses are then carried out to investigate the dynamic behavior of the FRC wall under blast loading. In addition, a data set of 384 samples on the damage of FRC wall due to blast loads is then produced in order to develop machine learning models. Second, three robust machine learning models of Random Forest (RF), Support Vector Machine (SVM), and Extreme Gradient Boosting (XGBoost) are employed to propose empirical evaluations for predicting the damage of FRC wall. The proposed empirical evaluations are very useful for practical evaluation and design of FRC wall subjected to blast loads.

Numerical simulation of pre-stressed concrete slab subjected to moderate velocity impact loading

Thai, Duc-Kien,Kim, Seung-Eock Elsevier 2017 Engineering failure analysis Vol.79 No.-

<P><B>Abstract</B></P> <P>This paper presents an efficient numerical analysis procedure to simulate failure analysis of a pre-stressed concrete slab subjected to the hard impact using LS-DYNA commercial software. In this study, the moderate velocity (60m/s–300m/s) used in the corresponding tests, is chosen in order to assess the punching resistant capacity of the slabs. Material nonlinearity is employed to consider failure and damage. The structural dynamic behavior of the materials is considered by taking into account the strain-rate effect, and damping effects are also investigated. An efficient method on the simplified modeling of pre-stressed concrete, namely the “Spotweld” method, is proposed, which allows introducing the pre-stressing force directly into the pre-stressing bars. To illustrate the accuracy of the proposed numerical analysis procedure, two different impact tests are used for the verification of the numerical modeling. The effects of modeling parameters are examined by several parametric analyses. It is shown that proposed modeling may be effectively used to investigate the structural behavior of pre-stressed concrete structures subjected to hard missile impact.</P> <P><B>Highlights</B></P> <P> <UL> <LI> An efficient FE model of pre-stressed concrete slab under missile impact is proposed. </LI> <LI> A simple method is proposed to introduce the pre-stressing force into the strands. </LI> <LI> FE model is validated using the available test data. </LI> <LI> Effects of damping, erosion, and pre-stressing values are investigated and discussed. </LI> </UL> </P>

Numerical investigation of the damage of RC members subjected to blast loading

Thai, Duc-Kien,Kim, Seung-Eock Elsevier 2018 Engineering failure analysis Vol.92 No.-

<P><B>Abstract</B></P> <P>This paper presents a numerical investigation into the damage of the reinforced concrete (RC) columns under the effect of the blast loading. A reliable finite element (FE) modeling of the blast test of a RC member is developed and analyzed using LS-DYNA. FE modeling is then verified by using the blast test data given in the recent works. Six series of RC columns having different section dimensions, subjected to explosions with different standoff distances are analyzed. Analysis results show that while the “stocky” columns demonstrate the local damage only, the slender columns display both local and global damage. Moreover, the charge position also plays an important role in the damage of the column. The RC column subjected to the explosion charged at mid-height shows a more significant damage than compared to one charged at its base. Axial compressive load in the range of 0.1 to 0.4<I>f</I> <SUB> <I>c</I> </SUB> <I>'A</I> <SUB> <I>g</I> </SUB> is found to have a significant effect on increasing the damage level of the slender column, but not the stocky column. The evaluations of damage of the RC columns and its residual load carrying capacity with different scaled distances are also provided as important results of this study.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A efficient FE model of RC column under blast loading is proposed. </LI> <LI> FE model is verified using the recent experimental data. </LI> <LI> Six series of RC columns having different section dimensions are analyzed. </LI> <LI> The local and global damages of columns are investigated and evaluated. </LI> </UL> </P>

Numerical investigation on local damage of proposed RC panels under impact loading

Thai, Duc-Kien,Nguyen, Duy-Liem,Kim, Seung-Eock Elsevier 2019 Nuclear engineering and design Vol.341 No.-

<P><B>Abstract</B></P> <P>The effects of transverse reinforcing rebar on the penetration resistant capacity of the reinforced concrete (RC) panel still remains a challenging problem in the field of civil and structural engineering. In the present paper, we numerically analyze the penetration resistant capacity of three proposed panels with different transverse reinforcing rebar arrangements. The obtained results are then compared with reference solutions derived from the conventional RC panel using T-bars. The components of the RC panel, missile, and support system are fully developed. Material nonlinearity, which considers erosion damage, is employed in this simulation. The IRIS Punching tests are used for validating the numerical modeling of the RC panel subjected to impact loading. Parametric studies with varying transverse reinforcing rebar arrangements and ratios are performed to investigate the penetration response of RC panels. The present numerical result shows that the proposed panels offer a better penetration resistant capacity than that of conventional panels using T-bars. We thus recommend an efficient design of RC panels with a proposed transverse reinforcing rebar arrangement.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Analysis of RC panels with different transverse reinforcement are presented. </LI> <LI> The conventional RC panel with T-bar is used for the purpose of comparison. </LI> <LI> Effects of transverse reinforcement arrangement and its ratio are presented. </LI> <LI> Efficient design of RC panel is recommended. </LI> </UL> </P>

A new empirical formula for prediction of the axial compression capacity of CCFT columns

Viet-Linh Tran,Duc Kien Thai,김승억 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.33 No.2

This paper presents an efficient approach to generate a new empirical formula to predict the axial compression capacity (ACC) of circular concrete-filled tube (CCFT) columns using the artificial neural network (ANN). A total of 258 test results extracted from the literature were used to develop the ANN models. The ANN model having the highest correlation coefficient (<i>R</i>) and the lowest mean square error (<i>MSE</i>) was determined as the best model. Stability analysis, sensitivity analysis, and a parametric study were carried out to estimate the stability of the ANN model and to investigate the main contributing factors on the ACC of CCFT columns. Stability analysis revealed that the ANN model was more stable than several existing formulae. Whereas, the sensitivity analysis and parametric study showed that the outer diameter of the steel tube was the most sensitive parameter. Additionally, using the validated ANN model, a new empirical formula was derived for predicting the ACC of CCFT columns. Obviously, a higher accuracy of the proposed empirical formula was achieved compared to the existing formulae.