a[mm]/l - Memorial University of Newfoundland DAI

the acceleml~on by about 40% I" the case of somply-supported and lncrravd about 30%
~n the case of fired support. In addltion. as the rlul remforcemcnr ntlo ~ncre;csd by
about 0 5%. the aeeelenttan lncread by about 10%.
The cntlcal vcloc8ty of pcrfonr~on aceord~ng to CEB (1988) were very close lo
the test re~ults for hlgh-strenpth ConerCle plates. both tn the case of fired and nmply-
supported However. br normal-strength concrete. the cnucal velmlaer were different.
Under fired condlnon, the ten results of normal-strength concrete plam were much
hlgher by about 308 than the code predicttan. On [he other hand. for ~nmply-supported
plses. the test mulls were rl~ghtlv lower by about 4% than the CEB (19881 predict8an.
In concluaon. the predietxon of cntlcal vcloctty bared on the CEB 11988) Equvtlon (5.9)
8s adequate md ern bs used to erttrnate the cnt~cal vclaclty of hlgh-strength concrete
plates rublecred lo tmpact loading accurately.
5.6. Fracture Mechanics Analysis of Impact Load
The strength of mtcnals depends on how rapndly the stress a applncd Thus. the rare of
lodlng effect 13 crtrrmcly Impman,. smec It sets a lhmtr on the allowable slresrcs ~n
structures based on the expled ttme under load. One of the mntn objective Is to use
fncture mcchantcr to pmvlde a more detvtled estamatc of the nte of loading effects on
the behanor of the concrete plats under Impact.
The fmture mshanlcs appmach to the nte of loading effect I" bnttle matmrlr 8s
bawd on he classical Griffith (1925) theory. The fracture 1% governed by equatnon: