/LOAD/PBLAST

Block Format Keyword Provides a fast way to simulate air blast pressure on a structure.

The Air Blast incident pressure is fitted from experimental data, then blast pressure is deduced from surface orientation to the detonation point. You must provide detonation point, detonation time and equivalent TNT mass.

This is a simplified loading method because the arrival time and incident pressure are not adjusted for obstacles. It also does not take into account confinement or ground effects.

Format

(1) (2) (3) (4) (5) (6) (7) (8) (9) (10)
/LOAD/PBLAST/load_ID/unit_ID
load_title
surf_ID Exp_data I_tshift Ndt IZ Iform       Node_ID
xdet Ydet Zdet Tdet WTNT
Pmin        
Ground_ID        

Definition

Field Contents SI Unit Example
load_title Load title.

(Character, maximum 10 digits)

 
surf_ID Surface identifier.

(Integer, maximum 10 digits)

 
Exp_data Experiment data flag.
1 (Default)
UFC-03-340-02 Free Air, Spherical charge of TNT.
2
UFC-03-340-02 Ground Reflection, Hemispherical charge of TNT.
3
UFC-03-340-02 Air Burst, Spherical Charge over the ground.

(Integer, maximum 10 digits)

 
I_tshift Time shift flag.
1 (Default)
No shift.
2
Shift time to skip computation time from 0 to t * = inf ( T a r r i v a l ) .

(Integer)

 
Ndt Number of intervals for minimal time step.

Δ t b l a s t = inf ( T 0 ) N d t

Where, T 0 is the duration of positive phase.

Default = 100 (Integer)

 
IZ Scaled Distance update with time.
=1
Scaled Distance is computed at initial time and does not change with time.
=2 (Default)
Scaled Distance is updated at each time step.

(Integer)

 
Iform Modeling flag.
= 1
Friedlander model.
= 2 (Default)
Modified Friedlander model.

(Integer)

 
Node_ID Node identifier defining detonation point.

If defined, the flags Xdet, Ydet and Zdet are ignored.

 
Xdet Detonation Point X-coordinate.

Ignored if Node_ID ≠ 0.

Default = 0.0 (Real)

[ m ]
Ydet Detonation Point Y-coordinate.

Ignored if Node_ID ≠ 0.

Default = 0.0 (Real)

[ m ]
Zdet Detonation Point Z-coordinate.

Ignored if Node_ID ≠ 0.

Default = 0.0 (Real)

[ m ]
Tdet Detonation time.

Default = 0.0 (Real)

[ s ]
WTNT Equivalent TNT mass.

(Real)

[ Kg ]
Pmin Minimum pressure.

Default = -1020 (Real)

[ Pa ]
Ground_ID Surface identifier for ground definition.

Ignored if Exp_data=1.

Surface type is /SURF/PLANE

Default: Origin =(0,0,0), normal=(0,0,H)

 

Comments

  1. Modeling situation is set with Exp_data flag. You provide explosion data (Xdet, Ydet, Zdet), explosion mass (WTNT) target surface (Surf_ID), and detonation time (Tdet). All other parameters and flags have default values.
    If Exp_data=3, explosive height must be defined.


    Figure 1.
    At a given point over the user surface, the corresponding radius R MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbwvMCKf MBHbqefqvATv2CG4uz3bIuV1wyUbqedmvETj2BSbqefm0B1jxALjhi ov2DaebbnrfifHhDYfgasaacH8srps0lbbf9q8WrFfeuY=Hhbbf9v8 qqaqFr0xc9pk0xbba9q8WqFfea0=yr0RYxir=Jbba9q8aq0=yq=He9 q8qqQ8frFve9Fve9Ff0dmeaacaGacmGadaWaaiqacaabaiaafaaake aacaWGxbaaaa@39B3@ and the explosive mass WTNT is used to determine characteristic values of the blast wave (arrival time t a MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqGqFfpeea0xe9vq=Jb9 vqpeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9q8qiLsFr0=vr 0=vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWG0bWaaS baaSqaaiaadggaaeqaaaaa@3973@ , maximum pressure Pmax, positive duration Δ t + MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqGqFfpeea0xe9vq=Jb9 vqpeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9q8qiLsFr0=vr 0=vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaacqqHuoarca WG0bWaaSbaaSqaaiabgUcaRaqabaaaaa@3AD5@ , impulse I + MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqGqFfpeea0xe9vq=Jb9 vqpeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9q8qiLsFr0=vr 0=vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGjbWaaS baaSqaaiabgUcaRaqabaaaaa@3943@ , ...) . Both incident wave and reflected wave are to follow Friedlander’s equation:
    • If Imodel = 1 (Friedlander model)(1)
      P F r i e d l a n d e r t = P max e t t a Δ t + 1 t t a Δ t + MathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqGqFfpeea0xe9vq=Jb9 vqpeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9q8qiLsFr0=vr 0=vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaaciGGqbWaaS baaSqaaiaadAeacaWGYbGaamyAaiaadwgacaWGKbGaamiBaiaadgga caWGUbGaamizaiaadwgacaWGYbaabeaakmaabmaabaGaamiDaaGaay jkaiaawMcaaiabg2da9iaadcfadaWgaaWcbaGaciyBaiaacggacaGG 4baabeaakiabgwSixlaadwgadaahaaWcbeqaamaalaaabaGaeyOeI0 YaaeWaaeaacaWG0bGaeyOeI0IaamiDamaaBaaameaacaWGHbaabeaa aSGaayjkaiaawMcaaaqaaiaabs5acaWG0bWaaSbaaWqaaiabgUcaRa qabaaaaaaakmaabmaabaGaaGymaiabgkHiTmaalaaabaGaamiDaiab gkHiTiaadshadaWgaaWcbaGaamyyaaqabaaakeaacaqGuoGaamiDam aaBaaaleaacqGHRaWkaeqaaaaaaOGaayjkaiaawMcaaaaa@6166@
    • If Imodel = 2 (modified Friedlander model)(2)
      P F r i e d l a n d e r ( t ) = P max e b ( t t a ) Δ t + ( 1 t t a Δ t + ) MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqGqFfpeea0xe9vq=Jb9 vqpeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9q8qiLsFr0=vr 0=vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaaciGGqbWaaS baaSqaaiaadAeacaWGYbGaamyAaiaadwgacaWGKbGaamiBaiaadgga caWGUbGaamizaiaadwgacaWGYbaabeaakmaabmaabaGaamiDaaGaay jkaiaawMcaaiabg2da9iaadcfadaWgaaWcbaGaciyBaiaacggacaGG 4baabeaakiabgwSixlaadwgadaahaaWcbeqaamaalaaabaGaeyOeI0 IaamOyaiaacIcacaWG0bGaeyOeI0IaamiDamaaBaaameaacaWGHbaa beaaliaacMcaaeaacqqHuoarcaWG0bWaaSbaaWqaaiabgUcaRaqaba aaaaaakmaabmaabaGaaGymaiabgkHiTmaalaaabaGaamiDaiabgkHi TiaadshadaWgaaWcbaGaamyyaaqabaaakeaacqqHuoarcaWG0bWaaS baaSqaaiabgUcaRaqabaaaaaGccaGLOaGaayzkaaaaaa@62B8@

    Where, P max , Δ t + , t a MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqGqFfpeea0xe9vq=Jb9 vqpeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9q8qiLsFr0=vr 0=vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGqbWaaS baaSqaaiGac2gacaGGHbGaaiiEaaqabaGccaGGSaGaaeiLdiaadsha daWgaaWcbaGaey4kaScabeaakiaacYcacaWG0bWaaSbaaSqaaiaadg gaaeqaaaaa@41DD@ are experimentally known at a given scaled distance R W 1 3 MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqGqFfpeea0xe9vq=Jb9 vqpeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9q8qiLsFr0=vr 0=vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaadaWcaaqaai aadkfaaeaacaWGxbWaaWbaaSqabeaadaWccaqaaiaaigdaaeaacaaI Zaaaaaaaaaaaaa@3AE2@ . 3

    With the modified Friedlander model (Iform=2), ‘b’ is a decay parameter introduced to fit the positive impulse.

    'b’ is solved such as:(3)
    t a t a + Δ t + P F r i e d l a n d e r ( t ) d t = I + MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqGqFfpeea0xe9vq=Jb9 vqpeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9q8qiLsFr0=vr 0=vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaadaWdXbqaai GaccfadaWgaaWcbaGaamOraiaadkhacaWGPbGaamyzaiaadsgacaWG SbGaamyyaiaad6gacaWGKbGaamyzaiaadkhaaeqaaOWaaeWaaeaaca WG0baacaGLOaGaayzkaaGaamizaiaadshacqGH9aqpcaWGjbWaaSba aSqaaiabgUcaRaqabaaabaGaiaiDdshadGaG0TbaaWqaiaiDcGaG0n yyaaqajaiDaaWcbaGaamiDamaaBaaameaacaWGHbaabeaaliabgUca Riabfs5aejaadshadaWgaaadbaGaey4kaScabeaaa0Gaey4kIipaaa a@5998@


    Figure 2. Blast profile from Friedlander equation
  2. The fitted time history function P i n c i d e n t ( t ) and P r e f l e c t e d ( t ) are also used to compute blast loading P B L A S T ( t ) at a given face centroid Z’ (Figure 3). 2(4)
    P B L A S T ( t ) = { cos 2 θ P r e f l e c t e d ( t ) + ( 1 + cos 2 θ 2 cos θ ) P i n c i d e n t ( t )       if  cos θ > 0                                           P i n c i d e n t ( t )                                if  cos θ 0 MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqGqFfpeea0xe9vq=Jb9 vqpeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9q8qiLsFr0=vr 0=vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaaciGGqbWaaS baaSqaaiaadkeacaWGmbGaamyqaiaadofacaWGubaabeaakmaabmaa baGaamiDaaGaayjkaiaawMcaaiabg2da9maaceaabaqbaeqabiqaaa qaaiGacogacaGGVbGaai4CamaaCaaaleqabaGaaGOmaaaakiabeI7a XjabgwSixlGaccfadaWgaaWcbaGaamOCaiaadwgacaWGMbGaamiBai aadwgacaWGJbGaamiDaiaadwgacaWGKbaabeaakmaabmaabaGaamiD aaGaayjkaiaawMcaaiabgUcaRmaabmaabaGaaGymaiabgUcaRiGaco gacaGGVbGaai4CamaaCaaaleqabaGaaGOmaaaakiabeI7aXjabgkHi TiaaikdaciGGJbGaai4BaiaacohacqaH4oqCaiaawIcacaGLPaaacq GHflY1ciGGqbWaaSbaaSqaaiaadMgacaWGUbGaam4yaiaadMgacaWG KbGaamyzaiaad6gacaWG0baabeaakmaabmaabaGaamiDaaGaayjkai aawMcaaiaabccacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabMga caqGMbGaaeiiaiGacogacaGGVbGaai4CaiabeI7aXjabg6da+iaaic dacaqGGaaabaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqGGaGa aeiiaiaabccacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabccaca qGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaa bccacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqGGaGaae iiaiaabccacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqG GaGaciiuamaaBaaaleaacaWGPbGaamOBaiaadogacaWGPbGaamizai aadwgacaWGUbGaamiDaaqabaGcdaqadaqaaiaadshaaiaawIcacaGL PaaacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqGGaGaae iiaiaabccacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqG GaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabc cacaqGGaGaaeiiaiaabccacaqGGaGaaeiiaiaabccacaqGGaGaaeyA aiaabAgacaqGGaGaci4yaiaac+gacaGGZbGaeqiUdeNaeyizImQaaG imaaaaaiaawUhaaaaa@C023@


    Figure 3. Blast pressure applied on a face centroid Z’ . depends on face orientation

    Where, θ is the angle between the surface segment (centroid Z’) and the direction to detonation point.

    This means that blast pressure is equal to reflected pressure if segment is directly facing the detonation point, and equal to incident pressure if segment is not facing the detonation point. This modeling is simple because arrival time and incident pressure are not adjusted with shadowing of the related structure. It also does not into account confinement and tunnel effect.

    This also requires the surface to have outward normal vector.

  3. If Iz =1, R is constant and computed during Starter at time=0.00. When Iz =2, R = R ( t ) MathType@MTEF@5@5@+= feaagKart1ev2aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqipu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq=Jc9 vqaqpepm0xbba9pwe9Q8fs0=yqaqpepae9pg0FirpepeKkFr0xfr=x fr=xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaamOuaiabg2 da9iaadkfacaGGOaGaamiDaiaacMcaaaa@3ADC@ is updated for each cycle during Engine computation.
  4. If WTNT is not set, the mass is zero and no pressure will be loaded on the related surface.
  5. If modeled explosive is not TNT, an equivalent TNT mass must be provided.
  6. The experimental data uses the unit system {cm, g, μ s MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqGqFfpeea0xe9vq=Jb9 vqpeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9q8qiLsFr0=vr 0=vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaacqaH8oqBca WGZbaaaa@3A16@ }. The units defined in /BEGIN will be used to convert the experimental data units to the model units. Therefore, the units defined in /BEGIN must correctly match the units used in the model.
  7. It is possible to skip computation time from T = 0 to t * = inf ( T a r r i v a l ) . The shift value is automatically computed during Starter execution. To disable a computation up to t * MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqGqFfpeea0xe9vq=Jb9 vqpeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9q8qiLsFr0=vr 0=vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWG0bWaaW baaSqabeaacaGGQaaaaaaa@393C@ , the I_tShift value must be equal to 2.


    Figure 4. I_tShift enables to skip computation time up to first wave arrival time
  8. The N d t MathType@MTEF@5@5@+= feaagKart1ev2aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqGqFfpeea0xe9vq=Jb9 vqpeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9q8qiLsFr0=vr 0=vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGobWaaS baaSqaaiaadsgacaWG0baabeaaaaa@3A49@ parameter can impose a minimum time step, if structural one is not large enough. Imposing Δ t b l a s t = inf ( T 0 ) N d t ensures that there are sufficient time steps during positive phase, that is, during the exponential, decrease of the blast wave. By default, N d t = 100 .


    Figure 5.
  9. Parameter P min MathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqGqFfpeea0xe9vq=Jb9 vqpeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9q8qiLsFr0=vr 0=vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGqbWaaS baaSqaaiGac2gacaGGPbGaaiOBaaqabaaaaa@3B38@ was introduced to keep positive part of Friedlander blast model.(5)
    P t = max ( P B L A S T ( t ) , P min ) MathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqGqFfpeea0xe9vq=Jb9 vqpeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9q8qiLsFr0=vr 0=vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaaciGGqbWaaS baaSqaaaqabaGcdaqadaqaaiaadshaaiaawIcacaGLPaaacqGH9aqp ciGGTbGaaiyyaiaacIhacaGGOaGaamiuamaaBaaaleaacaWGcbGaam itaiaadgeacaWGtbGaamivaaqabaGccaGGOaGaamiDaiaacMcacaGG SaGaamiuamaaBaaaleaaciGGTbGaaiyAaiaac6gaaeqaaOGaaiykaa aa@4C1F@
    Figure 6. Parameter P min MathType@MTEF@5@5@+= feaahqart1ev3aqatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqGqFfpeea0xe9vq=Jb9 vqpeea0xd9q8qiYRWxGi6xij=hbba9q8aq0=yq=He9q8qiLsFr0=vr 0=vr0db8meaabaqaciGacaGaaeqabaWaaeaaeaaakeaacaWGqbWaaS baaSqaaiGac2gacaGGPbGaaiOBaaqabaaaaa@3B38@ used to keep only overpressure (positive part of the loading)
1 Structures to resist the effects of accidental explosions. Departments of the Army, Navy, and Air Force, TM 5-1300/NAVFAC P-397/AFR 88-22, November 1990.
2 Randers-Pehrson, Glenn, and Kenneth A. Bannister. Airblast Loading Model for DYNA2D and DYNA3D. No. ARL-TR-1310. Army Research Lab Aberdeen Proving Ground MD, 1997.
3 Structures to resist the effects of accidental explosions, Unified Facilities Criteria (UFC), UFC 3-340-02, 5 December 2008