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Plain and Reinforced Concrete Targets Subjected to Projectile Impact
Available online at www.sciencedirect.com
ScienceDirect Procedia Engineering 173 (2017) 138 – 144
The 11th International symposium on plasticity and impact mechanics, IMPLAST 2016
Plain and reinforced concrete targets subjected to projectile impact M A Iqbal*, Abhishek Rajput, P. Bhargava Department of Civil Engineering, Indian Institute of Technology Roorkee, Roorkee, 247667, India
Abstract The ballistic performance of plain concrete and reinforced concrete targets of unconfined compressive strength 40 MPa was studied against projectile impact. The squarer plates of (450 mm x 450 mm) and thickness 60 mm with and without (8 mm@100 mmc/c) reinforcement were subjected to normal impact of hardened steel ogive nosed projectiles with diameter 19 mm and mass 0.5 kg. The incident velocities of the projectiles were varied between 28 to 102 m/s. The amount and area of damage, volume of spalling and scabbing as well as the ballistic limit of plain and reinforced concrete have been obtained and their results have been compared and discussed. The influence of reinforcement is clearly visible in minimizing the scabbing and spalling of material. The magnitude of scabbing decreased with increase in the projectile incidence velocity while the spalling of material remained unaffected. The ballistic limit of reinforced concrete target was 20% higher than plain concrete target for 60 mm thickness. © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of IMPLAST 2016. Peer-review under responsibility of the organizing committee of Implast 2016 Keywords: Crater; Spalling; Scabbing; Calibre Radius Head (CRH); Steel Projectile
1. INTRODUCTION The ballistic evaluation of reinforced concrete is highly important in order to design protective structures, bunkers, ammunition stores and nuclear storage facilities. The mechanism of penetration of concrete is relatively more complex than metals due to its complex material behaviour. Although a number of empirical and analytical models have been proposed for predicting the projectile penetration depth in concrete targets [1-3] and as such these are based on the proper experimental validation. However, most of these analytical expressions are focused on
* Corresponding author. Tel.: +91 1332 285866. E-mail address: [email protected]; [email protected] Fax: +91 1332 275568
1877-7058 © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of Implast 2016
doi:10.1016/j.proeng.2016.12.050
139
M.A. Iqbal et al. / Procedia Engineering 173 (2017) 138 – 144
determination of the penetration depth and scabbing thickness assuming the target to be semi-infinite and the influence zone to be highly localized [1, 4]. The effect of reinforcement is therefore not considered important. However, the mechanism of penetration in reinforced concrete targets requires closer examination of both local as well as global structural behaviour which depends upon a large number of parameters including but not limited to the strength of concrete, size and type of aggregate and detailing and percentage of reinforcement [2, 5]. The effect of some of the basic parameters on the perforation behavior and ballistic resistance of reinforced concrete still remains to be unclear. Hanchak et al. [6] carried out ballistic tests on 48 MPa and 140 MPa reinforced concrete plates and concluded that an increase of compressive strength by three times, had insignificant influence on the ballistic resistance of the target. On the other hand, the ballistic experiments conducted by Shirai et al. [7] on 35 MPa and 57 MPa reinforced concrete targets led to the conclusion that strength plays a major role to stop the projectile penetration and scabbing of material. Simillarly, Hanchak et al. [6] found that the reinforcement had an insignificant effect on the residual velocities while Haifeng and Jiangou [8] reported that dynamic load carrying capacity of reinforced concrete was significantly dependent upon the magnitude of reinforcement such that the reinforced concrete performed better than plain concrete target at higher ratios of reinforcement while an opposite trend was observed at low reinforcement ratios. The present experimental study is based on the assessment of deformation and ballistic resistance of plain and reinforced concrete targets of unconfined compressive strength 40 MPa. The square shaped target plates of plain and reinforced concrete of 60 mm thicknesses were subjected to normal impact of 19 mm diameter and 0.5 kg hardened steel projectiles. The impact and residual velocities of the projectile was calculated with the help of coordinate system available in the output window of Phantom V-411 high speed camera system, the frame rate was kept 15000 -20000 per second. The ballistic limit of plain and reinforced concrete target has also been evaluated. The volume of scabbing and spalling has been found to a function of incidence velocity. The ballistic limit of each of the concrete targets was computed by taking average of the highest velocity not giving perforation and the lowest velocity giving complete perforation of the target, however the ballistic resistance of reinforced concrete has been found to be 20% higher than that of the plain concrete.
2. Experimental procedure The experiments were conducted on a pneumatic gun capable to launch 1 kg projectile up to an incidence velocity of 180 m/s. The length of the barrel was considered 18 m to enable adequate acceleration of the projectile for obtaining the required velocity. The angle of incidence was considered normal to the target. In the previous readings researchers have studied with high strength concrete and also normal strength concrete but they have found that there is very minor effect in performance of the concrete targets with respect to their compressive strengths. The used concrete grade was M40 see Table-1. Concrete cubes were casted and kept carefully in the fresh water for wet curing of 28 days. After curing of concrete cubes had been tested on compression testing machine which gives unconfined average compressive strength of 48 MPa. Table 1. Constituents of concrete Cement
water
Aggregate (10mm)
Sand
admixture
437.9
166.4
1040.92
720
0.25%
The square concrete plates of span 450 mm x 450 mm were taken and concrete plates thickness were considered 60mm. The reinforcement grid has been incorporated in the middle of the concrete plate see fig-1(a) and 1(b) a cross section of concrete plate shown in fig-1b. The experiments were conducted on a pneumatic gun in the laboratory. 0.5 kg hard steel projectile as shown in Fig-1c, was launched between the incidence velocity range of 90-180 m/s.
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Fig. 1. Geometry of concrete plate and projectile (all dimension in mm) 3. Quantification of damage The damage induced in the plain and reinforced concrete targets during experimentation has been quantified by measuring the volume of material removed from the front and rear target surface. The equivalent diameter of the spalled and scabbed area was calculated as indicated in Fig. 2 in four different directions and the mean diameter has been obtained. Tables-2 shows the variation in the front and rear surface crater diameters as a function of incidence velocity of projectile for 60 mm thickness. It has been found that equivalent scabbing diameter increases with decrease in impact velocity. It may therefore be concluded that the global deformation has decreased with increase in projectile velocity. The spalling of material however is not influenced significantly by the incidence velocity. The volume of spalling and scabbing has also been calculated as a function of incidence velocity and the variation thus obtained has been plotted in Figs. 4(L) and 4(R) respectively for plain and reinforced concrete targets. The volume of material removed due to scabbing has been found to increase almost linearly with decrease in incidence velocity for both target thicknesses. The volume of spalling however remained almost constants for both the thicknesses in the considered velocity regime. For a given incidence velocity, the volume of scabbing has been found to be higher in the smaller thickness. For a given thickness however, the volume of both scabbing and spalling of material has been found to be comparatively lesser in reinforced concrete target compared to plain concrete target. This is due to the fact that the pressure wave propagation in reinforced concrete are very slow due to confinement of concrete hence the cracks were very small. On the other hand, in case of plain concrete cracks wide and long cracks were observed.
M.A. Iqbal et al. / Procedia Engineering 173 (2017) 138 – 144
4. Ballistic impact The projectile of 0.5 kilogram at the different striking velocity were impacted into the plain and reinforced concrete plates and residual velocity of projectile was measured using Phantom high speed digital camera system after perforation of target see Table-3. The ballistic resistance of the 60 mm thick plain and reinforced concrete plate has obtained. The damage induced in the plain and reinforced concrete targets during experimentation has been quantified by measuring the volume of material removed from the front and rear target surface. The equivalent diameter of the front and rear surface craters were calculated as indicated in Fig. 2 in four different directions and the mean diameter has been obtained. Table-2 shows the variation in the front and rear crater diameters as a function of incidence velocity of projectile for 60 mm target thickness. It has been found that equivalent scabbing diameter increases with decrease in impact velocity until ballistic limit. It may therefore be concluded that the global deformation has decreased with increase in projectile velocity. The spalling of material however is not influenced considerably by the incidence velocity.
Fig. 2. Equivalaent diameter measurment of affected area after perforation
Dequivalent
D1 D2 D3 D4 4
The volume of spalling and scabbing has also been calculated as a function of incidence velocity and the variation thus obtained and variation has been plotted in Fig.4L-4R for Plain and reinforced concrete target respectively. The volume of material removed due to scabbing has been found to increase almost linearly with decrease in incidence velocity for both type of concrete. The volume of spalling however remained almost constants for both types of concretes in the considered velocity regime. For a given incidence velocity, the volume of scabbing has been found to be higher in the smaller thickness. For a given thickness however, the volume of both scabbing and spalling of material has been found to be comparatively lesser in reinforced concrete target compared to plain concrete target. This is due to the fact that the pressure wave propagation in reinforced concrete was very slow due to partial confinement of concrete hence the cracks were very small. On the other hand, in case of plain concrete cracks wide and long cracks were observed. Equivalent diameter at front and rear face of the impacted specimen have been measured in four different directions and find out the mean of that four diameters in in four directions which is termed as equivalent diameter at front and rear face. It is found that equivalent diameter was increases with decrease of the impact velocity till ballistic limit however at low velocity higher global deformation had been found when compare to higher velocity for the same specimen. The typical failure modes of the impacted concrete target have been shown in Fig. 3, plain concrete target experienced the brittle cracking however reinforced concrete was failed in a little bit ductile manner.
141
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Fig. 3. Typical 60 mm thick target after projectile impact (a) plain and (b) reinforced concrete
Fig. 4. Front and rear surface eroded material of (L) Plain concrete (R) Reinforced concrete
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Table 2 Equivqlent diameter of 60 mm thick Plain concrete (PCC) and reinforced concrete (RCC) target after Impact
Front Surface Target Thickness (mm)
Specimen No.
60 60 60 60
Rear Surface
D1 (mm)
D2 (mm)
D3 (mm)
D4 (mm)
Equivalent Diameter (mm)
D1 (mm)
D2 (mm)
D3 (mm)
D4 (mm)
Equivalent Diameter (mm)
PCC-156 PCC-135 PCC-120 PCC-100
72 62.4 76 92
89.1 68.0 88.2 77.7
77.9 72.16 90.2 73.8
84 71.4 69.7 100.8
80.7 68.5 81.0 86.1
118.5 193.5 173.8 234.6
145.8 170.1 205.7 247.0
156 187.2 204 224
253.1 214.9 199.2 234.0
168.3 191.4 195.6 234.9
60
RCC-162
104
93.1
89.38
87.3
93.4
140.6
174.1
128
132.8
143.8
60
RCC- 145
56.8
58.3
53.3
68.8
59.3
100.3
147.4
175.2
118.6
135.4
60 60
RCC- 126 RCC-107
104 64
90.7 76.9
77.9 65.6
89.0 75.6
90.4 70.5
196.7 277.2
214.6 268.9
232.8 217.6
245.6 283.8
222.4 261.9
Table 3 Incidence and residual projectile velocities for different concretes
Plate thickness (mm)
60
Experimental Results Plain concrete Reinforced concrete Ini. Vel. (m/s)
Fin. Vel. (m/s)
Ini. Vel. (m/s)
Fin. Vel. (m/s)
180
105
162
80
156
70
145
51
135
45
126
28
100
18
115
10
90
0
107
0
5. CONCLUSION Conducting ballistic performances on plain concrete and reinforced concrete plates taking 48 MPa as unconfined compressive strength of the target specimen for both plain concrete plates and reinforced concrete plates of dimensions 450mm x 450mm x 60 mm for both plain concrete and reinforced concrete plates and studied the outcomes for both plain concrete and reinforced concrete plates. from the experiments it is found that The ballistic limit of reinforced concrete target was found 20% higher than plain concrete target. Also Residual velocities for reinforced concrete plates are decreased when compared to plain concrete plates. Due to the incorporation of reinforcement in the concrete plates there is very huge decrease in the scabbing however when striking velocity of the projectile is low then scabbing in the rear face of the concrete plate is high for plain concrete plates and as well as reinforced concrete plates. Spalling is almost same for plain concrete plates and reinforced concrete plates. Scabbing were increase with decrease of the velocities until ballistic limit of the
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specimens have been reached. Global deformation was higher at lower velocities while at higher velocities local deformation was found. Acknowledgement Authors gratefully acknowledge the financial support provided by the Science and Engineering Research Board, Department of Science and Technology through the research grant no. SB/S3/CEE/0032/2014 for the present study.
References [1] G. Hughes, Hard missile impact on reinforced concrete, Nuclear Engineering and Design, vol. 77, pp. 23-35, 1984. [2] Q. M. Li, Z. Q. Ye, G. W. Ma, S. R. Reid, Influence of overall structural response on perforation of concrete targets, International Journal of impact engineering, vol. 34, pp. 926-941, 2007. [3] G. G. Corbett, S. R. Reid, W. Johnson, Impact loading of plates and shells by free-flying projectiles: A review, International Journal of Impact Engineering, vol.18, pp.141-230, 1996. [4] Q. M. Li, S. R. Reid, H. M. Wen, A. R. Telford, Local impact effects of hard missiles on concrete targets, International Journal of impact engineering, vol. 32, pp. 224-284, 2005. [5] A. N. Dancygier, D. Z. Yankelevsky, C. Jaegermann, Response of high performance concrete plates to impact of non-deforming projectiles, International Journal of Impact Engineering, vol. 34 , pp.1768-1779, 2007. [6] S.J. Hanchak, M.J. Forrestal, E.R. Young, J.Q. Ehrgott, Perforation of concrete slabs with 48 MPa (7ksi) and 140 MPa (20 ksi ) unconfined compressive strengths, International Journal of Impact Engineering, vol.12, pp.17, 1992. [7] T. Shirai, A. Kambayashi, T. Ohno, H. Taniguchi, M. Ueda, N. Ishikawa, Experiment and numerical simulation of double-layered RC plates under impact loadings. Nuclear Engineering and Design, vol.176, pp. 195-205, 1997. [8] L. Haifeng, N. Jianguo, Mechanical behavior of reinforced concrete subjected to impact loading, Mechanics of Materials, vol.41, pp. 1298-1308, 2009.
ScienceDirect Procedia Engineering 173 (2017) 138 – 144
The 11th International symposium on plasticity and impact mechanics, IMPLAST 2016
Plain and reinforced concrete targets subjected to projectile impact M A Iqbal*, Abhishek Rajput, P. Bhargava Department of Civil Engineering, Indian Institute of Technology Roorkee, Roorkee, 247667, India
Abstract The ballistic performance of plain concrete and reinforced concrete targets of unconfined compressive strength 40 MPa was studied against projectile impact. The squarer plates of (450 mm x 450 mm) and thickness 60 mm with and without (8 mm@100 mmc/c) reinforcement were subjected to normal impact of hardened steel ogive nosed projectiles with diameter 19 mm and mass 0.5 kg. The incident velocities of the projectiles were varied between 28 to 102 m/s. The amount and area of damage, volume of spalling and scabbing as well as the ballistic limit of plain and reinforced concrete have been obtained and their results have been compared and discussed. The influence of reinforcement is clearly visible in minimizing the scabbing and spalling of material. The magnitude of scabbing decreased with increase in the projectile incidence velocity while the spalling of material remained unaffected. The ballistic limit of reinforced concrete target was 20% higher than plain concrete target for 60 mm thickness. © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of IMPLAST 2016. Peer-review under responsibility of the organizing committee of Implast 2016 Keywords: Crater; Spalling; Scabbing; Calibre Radius Head (CRH); Steel Projectile
1. INTRODUCTION The ballistic evaluation of reinforced concrete is highly important in order to design protective structures, bunkers, ammunition stores and nuclear storage facilities. The mechanism of penetration of concrete is relatively more complex than metals due to its complex material behaviour. Although a number of empirical and analytical models have been proposed for predicting the projectile penetration depth in concrete targets [1-3] and as such these are based on the proper experimental validation. However, most of these analytical expressions are focused on
* Corresponding author. Tel.: +91 1332 285866. E-mail address: [email protected]; [email protected] Fax: +91 1332 275568
1877-7058 © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license
(http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the organizing committee of Implast 2016
doi:10.1016/j.proeng.2016.12.050
139
M.A. Iqbal et al. / Procedia Engineering 173 (2017) 138 – 144
determination of the penetration depth and scabbing thickness assuming the target to be semi-infinite and the influence zone to be highly localized [1, 4]. The effect of reinforcement is therefore not considered important. However, the mechanism of penetration in reinforced concrete targets requires closer examination of both local as well as global structural behaviour which depends upon a large number of parameters including but not limited to the strength of concrete, size and type of aggregate and detailing and percentage of reinforcement [2, 5]. The effect of some of the basic parameters on the perforation behavior and ballistic resistance of reinforced concrete still remains to be unclear. Hanchak et al. [6] carried out ballistic tests on 48 MPa and 140 MPa reinforced concrete plates and concluded that an increase of compressive strength by three times, had insignificant influence on the ballistic resistance of the target. On the other hand, the ballistic experiments conducted by Shirai et al. [7] on 35 MPa and 57 MPa reinforced concrete targets led to the conclusion that strength plays a major role to stop the projectile penetration and scabbing of material. Simillarly, Hanchak et al. [6] found that the reinforcement had an insignificant effect on the residual velocities while Haifeng and Jiangou [8] reported that dynamic load carrying capacity of reinforced concrete was significantly dependent upon the magnitude of reinforcement such that the reinforced concrete performed better than plain concrete target at higher ratios of reinforcement while an opposite trend was observed at low reinforcement ratios. The present experimental study is based on the assessment of deformation and ballistic resistance of plain and reinforced concrete targets of unconfined compressive strength 40 MPa. The square shaped target plates of plain and reinforced concrete of 60 mm thicknesses were subjected to normal impact of 19 mm diameter and 0.5 kg hardened steel projectiles. The impact and residual velocities of the projectile was calculated with the help of coordinate system available in the output window of Phantom V-411 high speed camera system, the frame rate was kept 15000 -20000 per second. The ballistic limit of plain and reinforced concrete target has also been evaluated. The volume of scabbing and spalling has been found to a function of incidence velocity. The ballistic limit of each of the concrete targets was computed by taking average of the highest velocity not giving perforation and the lowest velocity giving complete perforation of the target, however the ballistic resistance of reinforced concrete has been found to be 20% higher than that of the plain concrete.
2. Experimental procedure The experiments were conducted on a pneumatic gun capable to launch 1 kg projectile up to an incidence velocity of 180 m/s. The length of the barrel was considered 18 m to enable adequate acceleration of the projectile for obtaining the required velocity. The angle of incidence was considered normal to the target. In the previous readings researchers have studied with high strength concrete and also normal strength concrete but they have found that there is very minor effect in performance of the concrete targets with respect to their compressive strengths. The used concrete grade was M40 see Table-1. Concrete cubes were casted and kept carefully in the fresh water for wet curing of 28 days. After curing of concrete cubes had been tested on compression testing machine which gives unconfined average compressive strength of 48 MPa. Table 1. Constituents of concrete Cement
water
Aggregate (10mm)
Sand
admixture
437.9
166.4
1040.92
720
0.25%
The square concrete plates of span 450 mm x 450 mm were taken and concrete plates thickness were considered 60mm. The reinforcement grid has been incorporated in the middle of the concrete plate see fig-1(a) and 1(b) a cross section of concrete plate shown in fig-1b. The experiments were conducted on a pneumatic gun in the laboratory. 0.5 kg hard steel projectile as shown in Fig-1c, was launched between the incidence velocity range of 90-180 m/s.
140
M.A. Iqbal et al. / Procedia Engineering 173 (2017) 138 – 144
Fig. 1. Geometry of concrete plate and projectile (all dimension in mm) 3. Quantification of damage The damage induced in the plain and reinforced concrete targets during experimentation has been quantified by measuring the volume of material removed from the front and rear target surface. The equivalent diameter of the spalled and scabbed area was calculated as indicated in Fig. 2 in four different directions and the mean diameter has been obtained. Tables-2 shows the variation in the front and rear surface crater diameters as a function of incidence velocity of projectile for 60 mm thickness. It has been found that equivalent scabbing diameter increases with decrease in impact velocity. It may therefore be concluded that the global deformation has decreased with increase in projectile velocity. The spalling of material however is not influenced significantly by the incidence velocity. The volume of spalling and scabbing has also been calculated as a function of incidence velocity and the variation thus obtained has been plotted in Figs. 4(L) and 4(R) respectively for plain and reinforced concrete targets. The volume of material removed due to scabbing has been found to increase almost linearly with decrease in incidence velocity for both target thicknesses. The volume of spalling however remained almost constants for both the thicknesses in the considered velocity regime. For a given incidence velocity, the volume of scabbing has been found to be higher in the smaller thickness. For a given thickness however, the volume of both scabbing and spalling of material has been found to be comparatively lesser in reinforced concrete target compared to plain concrete target. This is due to the fact that the pressure wave propagation in reinforced concrete are very slow due to confinement of concrete hence the cracks were very small. On the other hand, in case of plain concrete cracks wide and long cracks were observed.
M.A. Iqbal et al. / Procedia Engineering 173 (2017) 138 – 144
4. Ballistic impact The projectile of 0.5 kilogram at the different striking velocity were impacted into the plain and reinforced concrete plates and residual velocity of projectile was measured using Phantom high speed digital camera system after perforation of target see Table-3. The ballistic resistance of the 60 mm thick plain and reinforced concrete plate has obtained. The damage induced in the plain and reinforced concrete targets during experimentation has been quantified by measuring the volume of material removed from the front and rear target surface. The equivalent diameter of the front and rear surface craters were calculated as indicated in Fig. 2 in four different directions and the mean diameter has been obtained. Table-2 shows the variation in the front and rear crater diameters as a function of incidence velocity of projectile for 60 mm target thickness. It has been found that equivalent scabbing diameter increases with decrease in impact velocity until ballistic limit. It may therefore be concluded that the global deformation has decreased with increase in projectile velocity. The spalling of material however is not influenced considerably by the incidence velocity.
Fig. 2. Equivalaent diameter measurment of affected area after perforation
Dequivalent
D1 D2 D3 D4 4
The volume of spalling and scabbing has also been calculated as a function of incidence velocity and the variation thus obtained and variation has been plotted in Fig.4L-4R for Plain and reinforced concrete target respectively. The volume of material removed due to scabbing has been found to increase almost linearly with decrease in incidence velocity for both type of concrete. The volume of spalling however remained almost constants for both types of concretes in the considered velocity regime. For a given incidence velocity, the volume of scabbing has been found to be higher in the smaller thickness. For a given thickness however, the volume of both scabbing and spalling of material has been found to be comparatively lesser in reinforced concrete target compared to plain concrete target. This is due to the fact that the pressure wave propagation in reinforced concrete was very slow due to partial confinement of concrete hence the cracks were very small. On the other hand, in case of plain concrete cracks wide and long cracks were observed. Equivalent diameter at front and rear face of the impacted specimen have been measured in four different directions and find out the mean of that four diameters in in four directions which is termed as equivalent diameter at front and rear face. It is found that equivalent diameter was increases with decrease of the impact velocity till ballistic limit however at low velocity higher global deformation had been found when compare to higher velocity for the same specimen. The typical failure modes of the impacted concrete target have been shown in Fig. 3, plain concrete target experienced the brittle cracking however reinforced concrete was failed in a little bit ductile manner.
141
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M.A. Iqbal et al. / Procedia Engineering 173 (2017) 138 – 144
Fig. 3. Typical 60 mm thick target after projectile impact (a) plain and (b) reinforced concrete
Fig. 4. Front and rear surface eroded material of (L) Plain concrete (R) Reinforced concrete
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Table 2 Equivqlent diameter of 60 mm thick Plain concrete (PCC) and reinforced concrete (RCC) target after Impact
Front Surface Target Thickness (mm)
Specimen No.
60 60 60 60
Rear Surface
D1 (mm)
D2 (mm)
D3 (mm)
D4 (mm)
Equivalent Diameter (mm)
D1 (mm)
D2 (mm)
D3 (mm)
D4 (mm)
Equivalent Diameter (mm)
PCC-156 PCC-135 PCC-120 PCC-100
72 62.4 76 92
89.1 68.0 88.2 77.7
77.9 72.16 90.2 73.8
84 71.4 69.7 100.8
80.7 68.5 81.0 86.1
118.5 193.5 173.8 234.6
145.8 170.1 205.7 247.0
156 187.2 204 224
253.1 214.9 199.2 234.0
168.3 191.4 195.6 234.9
60
RCC-162
104
93.1
89.38
87.3
93.4
140.6
174.1
128
132.8
143.8
60
RCC- 145
56.8
58.3
53.3
68.8
59.3
100.3
147.4
175.2
118.6
135.4
60 60
RCC- 126 RCC-107
104 64
90.7 76.9
77.9 65.6
89.0 75.6
90.4 70.5
196.7 277.2
214.6 268.9
232.8 217.6
245.6 283.8
222.4 261.9
Table 3 Incidence and residual projectile velocities for different concretes
Plate thickness (mm)
60
Experimental Results Plain concrete Reinforced concrete Ini. Vel. (m/s)
Fin. Vel. (m/s)
Ini. Vel. (m/s)
Fin. Vel. (m/s)
180
105
162
80
156
70
145
51
135
45
126
28
100
18
115
10
90
0
107
0
5. CONCLUSION Conducting ballistic performances on plain concrete and reinforced concrete plates taking 48 MPa as unconfined compressive strength of the target specimen for both plain concrete plates and reinforced concrete plates of dimensions 450mm x 450mm x 60 mm for both plain concrete and reinforced concrete plates and studied the outcomes for both plain concrete and reinforced concrete plates. from the experiments it is found that The ballistic limit of reinforced concrete target was found 20% higher than plain concrete target. Also Residual velocities for reinforced concrete plates are decreased when compared to plain concrete plates. Due to the incorporation of reinforcement in the concrete plates there is very huge decrease in the scabbing however when striking velocity of the projectile is low then scabbing in the rear face of the concrete plate is high for plain concrete plates and as well as reinforced concrete plates. Spalling is almost same for plain concrete plates and reinforced concrete plates. Scabbing were increase with decrease of the velocities until ballistic limit of the
144
M.A. Iqbal et al. / Procedia Engineering 173 (2017) 138 – 144
specimens have been reached. Global deformation was higher at lower velocities while at higher velocities local deformation was found. Acknowledgement Authors gratefully acknowledge the financial support provided by the Science and Engineering Research Board, Department of Science and Technology through the research grant no. SB/S3/CEE/0032/2014 for the present study.
References [1] G. Hughes, Hard missile impact on reinforced concrete, Nuclear Engineering and Design, vol. 77, pp. 23-35, 1984. [2] Q. M. Li, Z. Q. Ye, G. W. Ma, S. R. Reid, Influence of overall structural response on perforation of concrete targets, International Journal of impact engineering, vol. 34, pp. 926-941, 2007. [3] G. G. Corbett, S. R. Reid, W. Johnson, Impact loading of plates and shells by free-flying projectiles: A review, International Journal of Impact Engineering, vol.18, pp.141-230, 1996. [4] Q. M. Li, S. R. Reid, H. M. Wen, A. R. Telford, Local impact effects of hard missiles on concrete targets, International Journal of impact engineering, vol. 32, pp. 224-284, 2005. [5] A. N. Dancygier, D. Z. Yankelevsky, C. Jaegermann, Response of high performance concrete plates to impact of non-deforming projectiles, International Journal of Impact Engineering, vol. 34 , pp.1768-1779, 2007. [6] S.J. Hanchak, M.J. Forrestal, E.R. Young, J.Q. Ehrgott, Perforation of concrete slabs with 48 MPa (7ksi) and 140 MPa (20 ksi ) unconfined compressive strengths, International Journal of Impact Engineering, vol.12, pp.17, 1992. [7] T. Shirai, A. Kambayashi, T. Ohno, H. Taniguchi, M. Ueda, N. Ishikawa, Experiment and numerical simulation of double-layered RC plates under impact loadings. Nuclear Engineering and Design, vol.176, pp. 195-205, 1997. [8] L. Haifeng, N. Jianguo, Mechanical behavior of reinforced concrete subjected to impact loading, Mechanics of Materials, vol.41, pp. 1298-1308, 2009.