ANALYSIS OF BLAST RESISTANT STRUCTURE

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 09 Issue: 07 | July 2022 www.irjet.net p-ISSN: 2395-0072
© 2022, IRJET | Impact Factor value: 7.529 | ISO 9001:2008 Certified Journal | Page 1219
ANALYSIS OF BLAST RESISTANT STRUCTURE
Shreya Vedpathak1, Prof. Ajay Hamane2
1 Student, Department of Civil Engineering, M. S. Bidve Engineering College, Latur, Maharashtra, India
2 Professor, Department of Civil Engineering, M. S. Bidve Engineering College, Latur, Maharashtra, India
---------------------------------------------------------------------***---------------------------------------------------------------------
Abstract - Bomb explosion near a building can cause
disastrous damage to the building externally and internally.
This can cause minor, moderate or major damage to the
building. The main aim of this study is to do a comparative
analysis of building models and know the response when
subjected to blast loads using ETABS software. In this study a
12-storey building is subjected to 100kg and 200kg TNT
charge weight with stand of distance 20m and 40m. Blast
parameters are calculated using IS 4991-1968.Further four
models are considered by implementing different structural
systems and response of the models in terms of storey
displacement and storey drift is considered to know the model
with the structural element that helps resist the effect of blast.
Key Words: Analysis, ETABS, Blast, Storey Displacement,
Storey Drift
1. INTRODUCTION
Structures, majorly that have higher chances of being target
of terrorist attacks should be safe from the blast effects. It is
important to study accordingly into this area to reduce the
losses caused due to the blast effects on the buildings. The
dynamic replica of the structure to blast loading is
complicated to analyse because of the non-linear action of
material. Blast explosions result in voluminous dynamic
loads, more complex than the original design loads, so for
analysis and design of blast loading detailed knowledge is
required of blast and its phenomena. Due to increase in
technology, the buildings mostly in large cities are
concentrated much on the comfort of living and the safety
against earthquake and wind loads but not concentrated
much on the blast loads. As explosions are becoming
common in metropolitan cities consideration of blast loads
on tall buildings especially public and commercial buildings
is necessary. In blast analysis, one can determine the
acceptable damage level that a structure can go through and
designed accordingly so that the structure can manage to
withstand even under worst conditions. Whenthe explosion
occurs, the damage can occur directly or indirectly,
externally or internally and so it should be possibly safe in
all the ways; prediction, prevention and mitigation of such
events are of major concern. This study referstotheanalysis
of the building under blast load and its impact on the
structure in response to storeydisplacementandstoreydrift
for different models implemented with different structural
elements. The models are analysed and compared to know
the blast resistant building model topreventoverall collapse
of the building in reference to the storey displacement and
storey drift.
1.1 Blast Loading Categories:
•Unconfined Explosions:
The explosion that occurs in open air causes a wave that
spreads from the source of detonation to the structure
without any wave amplification, as the explosion is at a
certain distance and height of structure the wave increases
due to the reflection of ground before it contacts the
structure.
The explosion near the ground is anexplosionoccurringnear
or on the ground and the initial pressure is immediately
increased as a result of refraction on the ground.
•Confined Explosions:
If the explosion occurs inside the structure, the peak
pressures associated with the initial wave fronts are
extremely high. They are enhanced by the refraction within
the structure. In addition to this, depending on the degree of
confinement, high temperatures and the accumulation of
gaseous products of chemical reactions in the blast would
produce more pressureandincreasetheloaddurationwithin
the structure. The combined effects of these pressures can
lead to the collapse of the structure, if the structure is not
designed to withstand internal pressure.Effect of pressureis
different in structures with openings and structures without
openings.
1.2 Expected Damage Levels:
•Minor:
o Non-structural failure of building elements such
windows, doors.
o Injuries may be expected and deaths are possible
but unlikely.
•Moderate:
o Structural damage is confined to a localized area
and is usually repairable.
o Structural failure is limited to secondary structural
members, such as beams, slabs and non-load
bearing walls.

o Injuries and deaths are expected.
•Major:
o Loss of primary structural members such as
columns.
o In this case, extensive deaths are expected.
o Building becomes non repairable.
1.3 Need:
 To resist or survive terrorist attacks.
 To minimize damage to the assets.
 To minimize the loss of lives.
 To subside social panic.
 To protect the historical monumentsandimportant
buildings.
1.4 Blast Phenomena:
The term blast is used commonly to describe situation in
which rapid release of energy occurs from a chemical,
mechanical or nuclear source. Structures designed to resist
blast load are subjected to completely different type of load
than considered in regular design. Here they are hit with a
rapidly moving shock wave which may exert pressure many
times greater than those experienced under storms. A blast
load is the load applied to a structure or object from a blast
wave, which is described by the combinationofoverpressure
that is the rise in pressureaboveatmosphericpressuredueto
the shock wave from an air blast, and either impulse or
duration that causes catastrophic damage to the building
both externally and internally. Blast effect is the damage
caused by the force of an explosive blast. When the blast
occurs at a location there will be a huge amount of hot gases
released which is the compresses the surrounding gases and
travels away from the blast source with higher velocity. The
distance between the blast source point and the structure is
called as the standoff distance.Astheblastwavetravelsaway
from the blast source the pressure or the intensity of the
wave goes on reducing and due to this the effect on the
building with higher standoff distance will be less and the
time duration required to reach the building is reduced. the
blast wave propagation curves depending on the pressure
and distance from the explosion or the blast source. A blast
wave generated during an explosion spreads through the
surrounding air and due to which a shock front or wave is
created. This shock wave created surround the entire
building subjected to blast pressure. Due to the impulsive
load developed by an explosion is highly nonlinearandcause
pressure in an extremely short duration, analysis of the
reinforced concrete frame structure is difficult. Pressure
intensities will be depended upon the charge weight (bomb
size) and standoff distances between blast source and
impacted structure (target). The factors affecting the blast
load are the material type, weight of the explosive, amountof
the energy released during the blast, distance between the
detonation point and the structurecalledasstandoffdistance
and intensity of the pressure released.
1.5 General Recommendations for Planning Blast
Resistant Buildings:
The IS Code 4991-1968 appendix C gives the general
recommendations for planning blast resistant buildings.
•Size of rooms: small size of rooms generally confines the
blast damage to a limited area of the structure,becauseofthe
screening action of the partition walls.
•Corridors: long narrow corridors should be avoided as
they tend to increase the extent of damagealongthelengthof
the corridors because of ‘multiple reflections.
•Projections: all slender projections like, parapets and
balconies specially those made of brittle materials should be
avoided as far as possible.
•Chimneys: masonry chimneys on factory buildings and
boiler houses are a potential hazard and should be avoided.
•Roofing andcladdingmaterials:brittleroofingmaterials,
such as tiles and corrugated asbestos sheets are especially
prone to blast damage. When corrugated galvanized iron
sheets are used for roofing and/or cladding, particular
attention should be paid to the fixtures fastening the
corrugated galvanized iron sheets to the framework.
•Use of timber andotherinflammablematerials:theseare
especially prone to catch fireinastrafingorincendiaryattack
and should be bestavoidedinstrategicstructureswheresuch
attacks might be expected.
•Electric wiring: conduit wiring is preferable to open
wiring, as in case of large movement of the walls the conduit
will give an added protection tothewiringinsideandprevent
them from getting cut thus preventing fire hazards due to
short circuits.
•Glass panes: the most widespread damageduetoblastis
the breaking of glass panes. The splinters from shattered
glass window are dangerous to personnel safety. It is
preferable to use non-splintering type glass panes wherever
their use cannot be avoided.
•Doors: doors should be designed for the front face load.
Wall thicknesses against flying splinters for protection
against splinters from bombs with equivalent bare charges
exploding at a distance of 15 m, the wall thicknesses given in
table 8 will be adequate.
1.6 Blast Load Parameters:
According to the IS Code 4991-1968: Criteria for blast
resistant design of structureforexplosionsabovegrounduse

of TNT (Trinitrotoluene) which is a pale yellow,solidorganic
nitrogen compound used chiefly as an explosive, is
considered as a reference for determining the blast
parameters for different charge weights and standoff
distances. The blast parameters calculated for the study are
in the similar way as shown in the example in the IS Code.
Example from IS Code4991-1968,appendixAforcalculation
of blast parameters for the rectangular building above
ground
Blast parameters due to the detonation of a O.1 tonne
explosive are evaluated on an above ground rectangular
structure, 3 m high, 10 m wide and 8 m long, situated at 30 m
from ground zero.
a) Characteristics of the Blast:
Scaled distance x = 30/ (0.1)1/3 = 64.65 m
From Table 1 of IS Code assuming pa = 1.00 kg/cm2 and
linearly interpolating between 63 m and 66 m for the scaled
distance 64.65 m, the pressures are directly obtained:
Pso= 0.35 kg/cm2; Pro = 0.81 kg/cm2; qo= 0.042 kg/cm2
The scaled times to and td obtained from Table 1 of IS Code
for scaled distance 64.65 m are multiplied by (0.1)1/3 to get
the values of therespectivequantitiesfortheactualexplosion
of 0.1 tonne charge.
to = 37.71 (0.1)1/3 = 17.5 milliseconds; td=28.32(0.1)1/3=
13.15 milliseconds
M = 1+ 6 pso / 7pa = 1.14
a = 344 m/s; U = 1.14 * 344 = 392 m/s = 0.392
m/millisecond
b) Pressures on the Building:
Here H = 3 m, B = 10 m, and L = 8 m
Then S = 3 m
tc = 3S/U= 3x3/0.392= 23.0 milliseconds> td
tt = L/U = 8/0.392 = 20.4 milliseconds > td
tr = 4S/U = 4*3/0.392 = 30.6 milliseconds > td
As tr > td no pressure on the back face are considered.
For Front Face:
Pro = 0.81 kg/cm2
For roof and sides:
Cd= -0.4; pso+ Cd*qo = 0.35-0.4 * 0.042 = 0.33 kg/cm2
Here, 0.1 Tonne TNT Explosive is considered for standoff
distance 30 m
pro= peak reflected overpressure; qo = peak dynamic
pressure
to = positive phase duration; td = duration of equivalent
triangular pulse
M = mach no. = 1+ 6 pso / 7pa
a = velocity of sound in air
U = shock front velocity = M*a
S = H or B/2 whichever is less.
Cd = drag coefficient, considered from table 2 of IS Code.
3. METHODOLOGY
ETABS software is used in this study. A 12-storeystructureis
considered subjected to 100kg and 200kg charge weight for
different standoff distances of 20m and 40 m for each charge
weight. Dead load, live load and blast load are considered for
the analysis. Four cases are considered corresponding to the
charge weights and standoff distances respectively. All the
blast parameters are calculated using the IS Code4991-1968
for the four cases. The peak reflected overpressure obtained
for the front and side face of the structure is multiplied with
the tributary area of the joint and blast load iscalculated.The
calculated blast load is applied as the joint load on all the
storeys of the structure and analysis is done using software.
Response of the structures for four cases in terms of storey
displacementandstoreydriftareobserved.Forfurtherstudy,
four models are generated; the structure among the four
cases that shows maximum displacement and drift is
considered as first model and other three models are
generated with different structural elements respectively.
Now all the four models are analyzed in the software to
observe the response of models in terms of storey
displacement and storey drift to conclude by analyzing the
model that is more resistant to blast load.
 Cases considered for analysis:
Case 1: Blast of 100kg explosive with standoff distance of
20m
40m
20m
40m
 Four different models generated for analysis:
Model 1 - Normal Building Structure
Model 2- Building Structure with increased column & beam
sizes.
pa = ambient atmospheric pressure; pso= peak side-on
overpressure

Model 3 - Building Structure with addition of shear walls at
the corners.
Model 4 - Building Structurewith addition of steel bracing at
the corners.
4. MODELING AND ANALYSIS
Table -1: Model data
No of grid in x direction 5
No of grid in y direction 4
Spacing of grid in x direction 5
Spacing of grid in y direction 4
No of storey 12
Storey height 3 m
Bottom storey height 3 m
Size of column 400*400 mm
Size of beam 300*300 mm
Thickness of slab 150 mm
Live Load 3 kn/m2
Brick Masonry external wall 0.230 m
Brick Masonry internal wall 0.115 m
Fig -1: Plan view of building.
Fig -2: 3D view of building.
Table -2: Blast load calculations
Blast Parameters Case 1 Case 2 Case 3 Case 4
Blast (kg) 100 100 200 200
Standoff distance (m) 20 40 20 40
Scaled distance (m) 43.08 86.17 34.19 68.39
pa (kg/cm2) 1 1 1 1
pso(kg/cm2) 0.724 0.232 1.120 0.324
pro(kg/cm2) 1.858 0.508 2.981 0.730
qo(kg/cm2) 0.170 0.018 0.388 0.035
to(milliseconds) 13.915 19.820 14.99 22.602
td(milliseconds) 9.626 14.940 9.91 17.047
M 1.26 1.095 1.39 1.132
a(m/s) 344 344 344 344
U 0.433 0.376 0.478 0.389
B 12 12 12 12
L 20 20 20 20
S 6 6 6 6
tc 41.57 47.87 37.65 46.27
tt 46.18 53.19 41.84 51.41
tr 55.42 63.82 50.20 61.69
Cd -0.4 -0.4 -0.4 -0.4
Front Face Pressure 1.858 0.508 2.981 0.730
Side Face Pressure 0.656 0.224 0.964 0.31
Loads on front face joints of the structure x-direction (KN)
Load on side joints 675 187.5 1087.5 270
Load on edge joints 1350 375 2175 540
Load on centre joints 2700 750 4350 1080
Loads on side face joints of the structure y-direction (KN)
Load on side joints 540 150 870 216
Load on edge joints 1080 300 1740 432
Load on centre joints 2160 600 3480 864
Fig -3: Load application on building for four cases.

Fig -4: Displacement comparison for four cases
Fig -5: Displacement comparison for four cases
Fig -6: Drift comparison for four cases
Fig -7: Drift comparison for four cases
Model 1: Among the four cases analyzed the case 3 has the
maximum displacement and drift. It shows that for increase
in blast load and decrease in standoff distance,displacement
and drift increases drastically. For further study case 3 is
considered as model 1 and response in terms of storey
displacement and storey drift is observed.
Model 2: For creating the model 2, themodel 1isconsidered
and changes are done in terms of columns and beams of the
structure for the similar blast load. Column is a structural
element that transmits, through compression, the weight of
the structure above to the other structural elements below.
Beam is a horizontal member spanning an opening and
carrying a load that may be a brick or stone wall above the
opening. For this model the column and beam sizes are
increased. Column size is changed from 400x400 mm to
600x600 mm. Beam size is changed from 300x300 mm to
450x450 mm. The model is then analyzed and response in
terms of storey displacement and storey drift is observed.
and changes are done in terms of adding shear wall to the
structure for the similar blast load. Shear wall is structural
element that is a rigid vertical diaphragm capable of
transferring lateral forces from exterior walls, floors and
roofs to the ground foundation in a direction parallel totheir
planes, it resists the forces such as wind, seismic and also
blast. For this model shear walls are added at the corners of
the structure, the thickness of the shear wall isconsidered as
150 mm. The model is then analyzed and response in terms
of storey displacement and storey drift is observed.
and changes are done in terms of adding bracings to the
structure for the similar blast load. Bracings are structural
elements that provide stabilityandresistsloads,theyconsist
of devices that clamp parts of structure together in order to
strengthen or support it, it resists the forces such as wind,
seismic and also blast. For this model bracings are added at

the corners of the structure, X-steel bracings, ISWB500 are
considered. The model is then analyzed and response in
terms of storey displacement and storey drift is observed.
Fig -7: Model 1 Fig -8: Model 2
Fig -9: Model 3 Fig -10: Model 4
5. RESULTS AND DISCUSSION
The aim of blast resistant building study is to prevent the
overall collapse of the building and prevent more damage to
the building. In spite of the fact that the extent of the
explosion and the loads cannot be predicted perfectly or
accurately. Themostpossibleactionsandconsiderations will
help to find the necessary engineering solutions for it.
In this study the scenario considered are the response for
assumed blast on the structure in terms of storey
displacement and storey drift.
Storey Displacement: It is the total displacement of the
storey with respect to ground.
Storey Drift: It is the lateral displacement of a floor relative
to the floor below.
Fig -11: Displacement comparison for four models
0
2000
4000
6000
8000
10000
1 2 3 4 5 6 7 8 9 10 11 12 13
Displacement
Model 1 Model 2 Model 3 Model 4
Fig -12: Displacement comparison for four models
Fig -12: Drift comparison for four models

0
0.1
0.2
0.3
0.4
0.5
1 2 3 4 5 6 7 8 9 10 11 12 13
Drift
Model 1 Model 2 Model 3 Model 4
Fig -13: Drift comparison for four models
6. CONCLUSION
 From the four cases studied, it shows that as the
blast load increases and the standoff distance
decreases the storey displacements and storey
drifts increase drastically.
 The blast parameters and effect of blast dependson
the charge weight and standoff distance values.
 From the models studied, it shows remarkable
change in the storey displacement and storey drift,
due to adding of different structural elements,there
is reduction in the storey displacement and storey
drift
 In the model 2, where column and beam sizes are
increased, the results show that structure will
improve the resistance, but as huge cross section of
columns and beams is needed it will not be possible
in many circumstances.
 In the model 3, where the shear walls are added at
the corners of the structure, the results show
effective improvement in the resistance and can be
considered for the structure to bedesignedfor blast
resistance.
 In the model 4, where the steel bracings are added
at the corners of the structure, the results show
improvement in the resistance and can be
considered for the structure to bedesignedfor blast
resistance.
 It is observed that adding shear wall and steel
bracings give effective results and shows decrease
in the storey displacement and storey drift. But it is
clearly observed that the addition of shear walls
give the good results and show minimum storey
displacement and storey drift in the structure
compared to the other models.
6. REFERENCES
[1] M. J. Sonavne, To Study And Analysis of RCC
Structure Under BlastLoadingbyJournal OfApplied
Science And Computations (2019)1076-5131
[2] P. Srikant Reddy, Blast Resistant Analysis And
Design Techniques For RCC MultistoreyBuildingBy
International Journal Of Civil Engineering And
Technology (2018)0976-6308
[3] Shobha R, Response Of Tall Structures Along Face
Exposed To Blast Load Applied At Varying Distance
By International Journal Of Recent Technology And
Engineering (2020)2277-3878
[4] T. P. Nguyen, Response Of Vertical Wall Structures
Under Blast Loading By Dynamic Analysis,Procedia
Engineering 14 (2011) 3308–3316
[5] C. M. Deshmukh, Behavior Of RCC Structural
Members For Blast Analysis: A Review By
International Journal Of Engineering Research And
Application (2016)2248-9622
[6] M. Meghanadh, Blast Analysis And Blast Resistant
Design Of R.C.C Residential Building By
International Journal Of Civil Engineering And
Technology (2017)0976-6308
[7] Sana N. Kazi, Analysis Of Blast Resistant RCC
Structure By International Research Journal Of
Engineering And Technology (2017)2395-0056
[8] Sajal Verma, Blast Resistant Design Of Structure By
International Journal Of Research In Engineering
And Technology (2015)2319-1163

ANALYSIS OF BLAST RESISTANT STRUCTURE

More Related Content

Similar to ANALYSIS OF BLAST RESISTANT STRUCTURE (20)

More from IRJET Journal (20)

Recently uploaded (20)

ANALYSIS OF BLAST RESISTANT STRUCTURE