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Blast Pressure Example

This document contains calculations for blast loading on an enclosed building from an external explosion. The building is 90m long, 98.4m wide and 70m tall. Calculations are presented for peak pressures, durations, impulses and equivalent static pressures on the front, side, roof and rear walls based on the building's dimensions and ASCE standards for blast-resistant design. Dynamic response factors are also calculated based on the fundamental period of vibration of the structure.

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709 views14 pages

Blast Pressure Example

This document contains calculations for blast loading on an enclosed building from an external explosion. The building is 90m long, 98.4m wide and 70m tall. Calculations are presented for peak pressures, durations, impulses and equivalent static pressures on the front, side, roof and rear walls based on the building's dimensions and ASCE standards for blast-resistant design. Dynamic response factors are also calculated based on the fundamental period of vibration of the structure.

Uploaded by

keshavnvaity
Copyright
© Attribution Non-Commercial (BY-NC)
We take content rights seriously. If you suspect this is your content, claim it here.
Available Formats
Download as XLSX, PDF, TXT or read online on Scribd
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Ref.

BLAST LOAD CALCULATION FOR ENCLOSED BUILDING Calculation

Rev.

Dimensions: Length of Building = L = Breadth of Building = B = Height of Building = H = 90 m. 98.4 m. 70 m.

2 Ductility = m = 1.5 (For Low Damage) (Refer Table 5.B.3 for Framed members) Energy Absorption (2m-1) = 2.0 Factor (a) Notes : 1 Using the maximum height of the Building. 2 Calculations as per ASCE Publication on "Design of Blast Resisant Buildigns in Petrochemical Facilities".

ASCE

Calculation of Blast Loading Peak side-on pressure = Duration of Blast = Pso = td = 14 kPa 40 milliseconds

Refer 3.5 page 3-9 Refer 3.6 page 3-9

0.5 Shock front Velocity= U = 345*(1+0.0083*Pso)

364.5 m/s

Length of Pressure = Lw = U*td Wave

14.58 m

Refer 3.6 page 3-9

2 Peak dynamic Wind = qo = (0.0032*Pso ) Pressure

0.627 kPa

Front Wall Loading Reflected Overpressure Pr = (2+0.0073*Pso)*Pso Clearing Distance S = 29.41 Kpa

= minimum of H or B/2

49.2 m

Ref.

Calculation Reflected Overpressure Clearing time tc = 3(S/U)<td

Rev.

0.04 sec

sec. 3.3.3

Drag Coefficient Cd =

Page 1 of 14

3.7, page 3.-14

Stagnation Pressure Ps = Pso+Cd*qo

14.63 kPa

3.9, page 3.-15

Front Wall Impulse Iw = 0.5*(Pr-Ps)*tc+0.5Ps*td

0.588 kPa-sec

3.10, page 3.-15

Effective Duration te = 2Iw/Pr

0.040 sec

Side Wall Loading sec. 3.3.3 3.9, page316 Drag Coefficient Cd = = -0.4

Equivalent Load Coeffiecient Ce =

Lw/L1 = L1~ 1 m

14.58

3.11 page 3.-16

Equivalent Peak Pressure Pa = Ce*Pso+Cd*qo

13.7 kPa

Rise Time tr = L1/U Total Phase duration = to = tr+td = = 0.003 sec 0.043 sec

Ref. For Average Pressure 3.9, page316 Equivalent Load Coeffiecient Ce =

Calculation

Rev.

0.15

Lw/L =

0.162

3.11 page 3.-16

Average Pressure Pa = Ce*Pso+Cd*qo

1.8 kPa

Rise Time tr = L/U = 0.247 sec

Roof Loading sec. 3.3.3 Drag Coefficient Cd = Page 2 of 14 = -0.4

3.9, page316

Equivalent Load Coeffiecient Ce =

0.7

Lw/L1 = L1~ 6 m

2.43

3.11 page 3.-16

Equivalent Peak Pressure Pa = Ce*Pso+Cd*qo

9.5 kPa

Rise Time tr = L1/U Total to = tr+td For Average Pressure 3.9, page316 Equivalent Load Coeffiecient Ce = = = 0.016 sec 0.056 sec

0.15

Lw/L =

0.162

3.11 page 3.-16

Average Pressure Pa = Ce*Pso+Cd*qo Rise Time tr = L/U

1.8 kPa

0.247 sec

Ref. 3.5.4 sec. 3.3.3 3.9, page316 Rear Wall Load Drag Coefficient Cd =

Calculation

Rev.

-0.4

Equivalent Load Coeffiecient Ce =

0.2

Lw/S =

0.296

3.11 page 3.-16

Equivalent Peak Pressure Pa = Ce*Pso+Cd*qo

2.5 kPa

Time of arrival ta = L/U = 0.247 sec

Rise Time tr = S/U = 0.135 sec

duration

td =

0.04 sec

Total Phase duration

= to = tr+td

0.175 sec

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Time Period of Structure T = Ct (hn)3/4


Numerical co efficient based on the Type of the Structure.

UBC 1997,Section 1630.2.2,Formula 30-8 For all other buildings.

Ct =

0.049

Height of the Building above Base level.

hn = Ct = T =

70 m 0.049 1.186 Sec

Ref.

Calculation

Rev.

Element Front Wall Loading Side Wall Loading Roof Loading Rear Wall Load

Dynamic Response Dynamic Peak Presure Duration Pa (Kpa) td (sec) 29.4 13.7 9.5 2.5 0.040 0.043 0.056 0.175

t= td/T 0.034 0.036 0.048 0.148

Equivalent Static Presure Pse (Kpa) 2.199 1.098 1.006 0.805

For SDOF - Considering Fundamental Mode Equivalent Static Pressure =

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milliseconds

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milliseconds

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