» t ‘ \ - 2 oar Ra Urs "length ef the positive phat oo. effect with lead te a murned aiinval ce ci ptek po@amares ard the wus. 3 tw rase in pressure, anateat of tne ideal er ances here. AY wilt reau.t oF siightiy greater distames, the tarma’ effe Sehe rise socw ly compiet@ a “han a "partial shock" rather further, the shock front will be sharp as sncvr Ap.t- he fet 7 distances the negative phase increases ans eventually the pe 22 ite and negative imputse urder the bias. was Poocme equa’ In trensiating these curies to hffernnt yholis, beth the distance and tim boat be drrced @ wo 3, helidng preseurce constant. In many cases, the sritecicr. for structure: damage is net simply peak preasure, but the produit cf the alr density and the square of the material velovity 4 ut, ti13 blast wind resulta in a dynamic presswe on structures; the time vardaticn of this dynamic pressuse may be teks: as appreximaely simihar te tne preosure-time curece shewn here, 2.2.4 Tira ef Arrival Figure 1 gives the time of arrisal of the shoek wars as a function of distance. Thes2 curs a>? based on calsularion: from peak pressures observed on tower shots, bul e€ in good agreemen. with the time-of-arrival curve as predistiad from the IBM cuz using thic yield, Urdike peak preaturtss, the observed time of avrival should be independent of the typs of surfaces. 2.2.5 Positive Duration Figure & shows the duration of the positive phass ev toe blast wave as a functicn of distante from the bomb. The upwea swing of this curve at shert distances is aasetiaved with the hack of a negative phase at this pcint. where a*curate encinanes of the pressure decay is required 2* clese-in distan<s, tha precsy a -lm curves may be fitted by a powrr law a seni-ieparithmic pict. Fee example, the curve showr for 1,005 pai can ta fitted initaiv by Pap 4°55 and later by Pow ifee® os & wee Be BT 2.2.6 Positive Impulse vs Distance Figure 9 shows the positive impulse, cr I t af & function of distance. If further information is desived, such as the magative imulse, these values can be devived upon request. 2.3 Protestion frem Blast 2odok Gereral Rules As pointed out earlier, every reasonable precaution must be taken against the blast effects and every method which ingenuity suggest should ba used, but no prohibitive problems ave presanted by blast. It is impossible te point out here the criterion fer all types of structures, but the following discussicn shows tne general character of the clenclusions which may be expected It is cuggested that test personnel consider their individual) structwes on the basia of the field wariables given in Figs. i thre 10.