A Study on Blast Mitigation by Meandering the Possible Blast Impact

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A Study on Blast Mitigation by Meandering the Possible Blast Impact

Sarath Raj1, Berlin Sabu2

1Student, Department of Civil Engineering, Mar Athanasius College of Engineering, Kothamangalam, Ernakulam, India.

2Assistant Proffessor, Department of Civil Engineering, Mar Athanasius College of Engineering, Kothamangalam, Ernakulam.

Abstract – In response of the increased terror threat in recent year, there is an increasing trend in blast mitigation at sites that are categorized by an increased likelihood of being the target of a terrorist attack. A latest data reveal that unprotected areas of mass congregation of people have become attractive to terrorist groups. Such control zones could be located within the building that has to be protected or attached to it. Elevated security needs for these areas call for a design that will consider the risk of internal explosive events. This study includes strategy for limiting the consequences of an internal blast, while guaranteeing that the produced blast wave does not propagate into vulnerable areas. The introduction of a protective wall system in the form of a meander that allows unobstructed access of the public and at the same time reduces the possible blast inflow to the buildings interior. ANSYS software is used to assess the possible blast pressure and structural damage of the protective wall.

KeywordsControl Zones, ANSYS, Protective Wall

  1. INTRODUCTION

    Research on the use of fibers to increase the strength of both blast and impact structures has typically been limited to steel fibers and, to a lesser degree, polypropylene fibers. Carbon fibers possess many potential benefits over other fibers, including stiffness and high strength, as well as increased durability. Carbon fibers are very economical as they are readily available as a waste product from the aerospace industry.

    The use of long carbon fibers within a concrete mix can be an economical option for improving blast resistance with distinct advantages over other blast-resistant materials. The long carbon fibers will also reduce secondary fragmentation by improving the spalling resistance of the concrete which is a critical property for protecting personnel and equipment during a blast and difficult to prevent with current materials. With the use of long carbon fibers, these improvements come with little to no modification of current design practices, allowing implementation to occur quickly and easily.

    Two concrete models one without long carbon fibre and one with long carbon fibre incorporated is taken into account for analysis in ANSYS. Blast load at an eccentricity 0mm, 500mm, 1000mm and 1500mm is studied for both the cases. The parameters studied are directional deformation and normal stresses along the direction of application of load.

  2. MODELLING

    M30 concrete wall with C – shape without steel plates is analysed in ANSYS-Autodyn to study the behaviour of concrete in such a high strain loading. The properties of concrete used are tabulated in Table 2.1

    Table 1. Material Properties

    Properties

    Value

    Unit

    Density

    2400

    Kg/m3

    Youngs Modulus

    30000

    MPa

    Poissons Ratio

    0.18

    Fig. 1. Modelled Meandering Wall

    The concrete wall is modelled in Explicit Dynamics module of ANSYS with the plan dimensions as 5m × 3m with thickness of 0.2m as shown in Fig. 1. The analysis is done by using a charge weight of 100 kg TNT at a height of 1m above ground surface with a stand-off distance of 3m. Concrete wall is modelled as a solid part and the end conditions are fixed. The contact regions are defined by bonded contact.

  3. NORMAL CONCRETE MODEL

    The maximum positive deformation, maximum negative deformation, maximum normal stresses and maximum negative normal stresses are obtained as shown in Table 2.

    Table 2. Consolidated Results

    Distance from Centre (mm)

    Max. Positive Deformation (mm)

    Max. Negative Deformation (mm)

    Max. Positive Normal Stress (MPa)

    Max. Negative Normal Stress (MPa)

    0

    21.015

    -206.54

    21.765

    -61.294

    500

    8.218

    -139.110

    12.792

    -49.472

    1000

    15.529

    -191.600

    50.724

    -31.171

    1500

    32.291

    -203.490

    14.415

    -31.447

    Maximum Positive Deformation v/s Distance

    35

    30

    25

    20

    15

    10

    5

    0

    Maximum Positive Deformation v/s Distance

    35

    30

    25

    20

    15

    10

    5

    0

    Maximum Positive Deformation (mm)

    Maximum Positive Deformation (mm)

    0

    0

    500

    500

    1000

    1000

    1500

    1500

    2000

    2000

    Maximum Negative Normal Stress v/s Distance

    0

    0 500 1000 1500

    -20

    -40

    -60

    -80

    Distance to the Wall (mm)

    Maximum Negative Normal Stress v/s Distance

    0

    0 500 1000 1500

    -20

    -40

    -60

    -80

    Distance to the Wall (mm)

    Distance to the Wall (mm)

    Distance to the Wall (mm)

    Maximum Normal Stress (MPa)

    Maximum Normal Stress (MPa)

    Fig. 2. A Plot showing Maximum Positive Deformation v/s Distance to the Wall

    0

    0 500 1000 1500 2000

    Maximum Negative Deformation (mm)

    Maximum Negative Deformation (mm)

    -50

    -100

    -150

    -200

    -250

    Distance to the Wall (mm)

    Fig. 5. A Plot showing Maximum Negative Normal Stress v/s Distance to the Wall

    The positive normal stress was found to be varying in an irregular manner. The negative normal stress was found to be increasing and then remain almost constant for 1000mm and 1500mm eccentricity from the center of the wall.

  4. LONG CARBON FIBRE MODEL

    The study was conducted for meandering wall made of concrete with Long Carbon Fibre. Long Carbon Fibre is a twined, 48K, polypropylene backbone carbon fibre with an optimized application of 100 mm long fibres and a dosage rate of 1% by volume. The maximum positive deformation, maximum negative deformation, maximum normal stresses and maximum negative normal stresses are obtained as shown in Table 3.

    Table 3. Consolidated Results

    Fig. 3. A Plot showing Maximum Negative Deformation v/s Distance to the Wall

    The maximum positive deformation in all cases was found to be first decreasing and then increasing. The maximum deformation was found when the detonation point was at 1500mm eccentricity from the center of the wall. The maximum negative deformation was found to be first

    Distance from Centre (mm)

    Maximum Positive Deformation (mm)

    Maximum Negative Deformation (mm)

    Maximum Positive Normal Stress

    Maximum Negative Normal Stress

    1000

    (MPa)

    (MPa)

    0

    18.972

    -214.77

    2.3523

    -3.5852

    500

    8.2181

    -139.11

    0.79059

    -3.8518

    6.58

    -152.19

    1.3056

    -4.8625

    1500

    9.9788

    -153.29

    2.1151

    -6.3561

    (MPa)

    (MPa)

    0

    18.972

    -214.77

    2.3523

    -3.5852

    500

    8.2181

    -139.11

    0.79059

    -3.8518

    1000

    6.58

    -152.19

    1.3056

    -4.8625

    1500

    9.9788

    -153.29

    2.1151

    -6.3561

    increasing and then decreasing. The maximum negative deformation was found to be 206.54mm.

    Positive Deformation v/s Distance

    Maximum Positive Deformation (mm)

    Maximum Positive Deformation (mm)

    20

    15

    10

    5

    0

    0 500 1000 1500

    Distance from Centre (mm)

    Maximum Positive Normal Stress v/s Distance

    60

    50

    40

    30

    20

    10

    0

    0 500 1000 1500

    Distance to the Wall (mm)

    Maximum Positive Normal Stress v/s Distance

    60

    50

    40

    30

    20

    10

    0

    0 500 1000 1500

    Distance to the Wall (mm)

    Maximum Positive Stress (MPa)

    Maximum Positive Stress (MPa)

    Fig. 6. Plot of Positive Deformation v/s Distance

    Fig. 4. A Plot showing Maximum Positive Normal Stress v/s Distance to the Wall

    Negative Deformation v/s Distance

    0

    0 500 1000 1500

    -50

    -100

    -150

    -200

    -250

    Distance from Centre (mm)

    Negative Deformation v/s Distance

    0

    0 500 1000 1500

    -50

    -100

    -150

    -200

    -250

    Distance from Centre (mm)

    Maximum Positive Deformation (mm)

    Maximum Positive Deformation (mm)

    Fig. 7. Plot of Negative Deformation v/s Distance

    The maximum positive deformation was found to be initially decreasing and then slightly increasing. The maximum deformation was found at the point of zero eccentricity from the center of the wall. Negative deformation was found to be first increasing and then decreasing.

    The positive normal stress was found to be first decreasing and then increasing. The negative normal stress is found to be gradually decreasing with respect to distance.

  5. INTERPRETATION OF RESULTS

    Maximum Deflection in Concrete Model v/s Long Carbon Fibre Model

    Maximum Deflection in Concrete Model v/s Long Carbon Fibre Model

    35

    30

    25

    20

    15

    10

    5

    0

    35

    30

    25

    20

    15

    10

    5

    0

    Maximum Positive Stress (MPa)

    Maximum Positive Stress (MPa)

    2.5

    2

    1.5

    1

    0.5

    0

    Maximum Positive Stress v/s Distance

    0 500 1000 1500

    Distance from Centre (mm)

    0

    0

    500

    500

    1000

    1000

    1500

    1500

    Maximum Positive Deformation in Normal Concrete Model(mm)

    Maximum Positive Deformation in Long Carbon

    Fibre Concrete Model (mm)

    Maximum Positive Deformation in Normal Concrete Model(mm)

    Maximum Positive Deformation in Long Carbon

    Fibre Concrete Model (mm)

    Fig. 9. Plot of Maximum Deflection in Normal Concrete v/s Maximum Deflection in Long Carbon Fibre Model

    The maximum deflection at detonation points 0mm, 500mm, 1000mm and 1500mm was found to be decreasing while introducing long carbon fibre into the concrete. At eccentricity 0mm, there is a small reduction in deflection. At 500mm eccentricity, the deflection remains almost the same while at eccentricity 1000mm, there is a considerable reduction in deflection. The maximum reduction in deflection is found between the detonation points 1000mm and 1500mm.

    Maximum Stress in Concrete Model v/s Long Carbon Fibre Model

    Maximum Negative Stress (MPa)

    Maximum Negative Stress (MPa)

    Fig. 8. Plot of Maximum Positive Stress v/s Distance

    Maximum Negative Stress v/s Distance

    Maximum Negative Stress v/s Distance

    0

    -1

    -2

    -3

    -4

    -5

    -6

    -7

    0

    500

    1000

    1500

    0

    -1

    -2

    -3

    -4

    -5

    -6

    -7

    0

    500

    1000

    1500

    Distance from Centre (mm)

    Distance from Centre (mm)

    FiG. 8. Plot of Maximum Negative Stress v/s Distance

    60

    50

    40

    30

    20

    10

    0

    0 500 1000 1500

    Maximum Positive Normal Stress in Normal Concrete Model (MPa)

    Fig. 10. Plot of Maximum Stress in Normal Concrete v/s Maximum Stress in Long Carbon Fibre Model

    The maximum stress at detonation points 0mm, 500mm, 1000mm and 1500mm was found to be decreasing while introducing long carbon fibre into the concrete. At eccentricity 0mm and 500mm there is a reduction in deflection. There is a considerable reduction in deflection at eccentricity 1000mm. The maximum reduction in deflection is found between the detonation points 1000mm and 1500mm.

  6. CONCLUSIONS

It was found that deformation of the concrete wall was decreased with addition of long carbon fibre in to the concrete in resisting the blast load. For a concrete wall without long carbon fibre, the maximum deformation is when the detonation point is kept at an eccentricity of 1500mm with the center of the wall and is 32.29mm whereas in case of concrete wall with long carbon fibre, the maximum deformation was reduced to 9.98mm at the same detonation point. Similarly the normal stresses were also considerably reduced in case of concrete wall with long carbon fibre. In case of normal concrete, the maximum stress is at an eccentricity 1000mm and is 50.72MPa whereas in case of long carbon fibre the stress was reduced to 1.30MPa.

ACKNOWLEDGMENT

I take this opportunity to express my deep sense of gratitude and sincere thanks to all who helped me to complete the work successfully. First and foremost, I thank God Almighty who showered his immense blessings on my effort. I express my deep and sincere gratitude to my guide Asst. Prof. Berlin Sabu, Assistant Professor in Civil Engineering, for giving me her valuable suggestions and guiding me throughout the course of my project. I also like to record my gratitude to our coordinator

Prof. Elson John, Associate Professor and Prof. Leni Stephen, Head of the Department, for their enterprising attitude, timely suggestions and support. I am thankful to my parents, my friends and all others who have helped me directly or indirectly for the successful completion of this project.

REFERENCES

  1. Zahra S. Tabatabaei , Jeffery S. Volz, Jason Baird, Benjamin P. Gliha, Darwin I. Keener; Experimental and Numerical Analyses of Long Carbon Fibre Reinforced Concrete Panels Exposed to Blast Loading, International Journal of Impact Engineering, Vol. 57, No. 1, 9 February 2013, pp. 70-80.

  2. Martin Larcher , Georgios Valsamos, and Vasilis Karlos; Access Control Points: Reducing a Possible Blast IMPact by Meandering, Advances in Civil Engineering, Vol. 2018, Article ID 3506892, 11 February 2018, pp. 1-12.

  3. Ashish Kumar Tiwary, Aditya Kumar Tiwary and Anil Dhiman; Analysis of Concrete Wall under Blast Loading, International Journal of Computer Applications, Vol. 126, Article ID 325673174, 14 June 2016, pp. 12-23.

  4. Weifang Xiao, Matthias Andrae, Norbert Gebbeken; Numerical study of blast mitigation effect of innovative barriers using woven wire mesh, Engineering Structures, Vol. 213, Article ID 110574, 24 March 2020, pp. 1-17.

  5. Xingxing Liang, Zhongqi Wang, Runan Wang; Deformation model and performance optimization research of composite blast resistant wll subjected to blast loading, Journal of Loss Prevention in the Process Industries, Vol. 17, No. 6, 24 July 2017, pp. 12-29.

  6. Mitsuhiro Okayasu, Yuki Tsuchiya; Mechanical and fatigue properties of long carbon fibre reinforced plastics at low temperature, Journal of Science: Advanced Materials and Devices, Vol. 4, No. 2, 6 October 2019, pp. 577-583.

  7. Tao Liu, Wei Feng, Zhi-mei Zhang, Yu OuyanG; Experimental study on ductility improvement of reinforced concrete rectangular columns retrofitted with a new fibre reinforced plastics method, Journal of Shanghai University, Vol. 12, No. 1, February 2008, pp. 7-14.

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