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

fb) Elastlc plastic behavior wath hwdcn~ng
lnltead of under~osng unllmlred deformatlan at ;r conslant rrress level. rhe rrrerser
lncrearc with lncrearlng stram Rate effects upon the yzcld surface are ~ntmduced.
for cramplc tn the form of rate hardenmg paramcrcrr.
(5) Endachmntc models
Modclr hared on cndachmn~c theory havr been devclopd for concrete and
re~nforctng steel. Onginally Ihe cndochronlc theory was bared on the vnscoplnruc
Leoq. supplemenled by a new lntemal vanable. the lnlnnrlc tlme. Although the
endoehmn~c theory war the subject of cantroverrul dnrcurnonr, a Eecms that some
phenomena. likc the influence of the loadnng hlrtory upon the stress-stram
relalonrhjp and the rmtn-rule depndancy. are very well represcntd. For relntorcing
rtel this model a adequate. but for concrete. the problem of dnlntancy a1 high nrun
IS not salved yet.
(6) Fneture mcchiln~cs models
Fmcare mechanics has to be ruM#v~ded tnto r lhnear and r nan-Itnear lhwry The
Itnear theory provlder a pod barns to predlet unstable or eatanmph~c propagatton.
Relauonr exla between frrctunng stress. crack length, md ~ lra~n ras. Lanew fmclure
mechanics doer not take any planlc dcformalon or mrm-cracklng ~n the regIan of
the cmck ep ~nro account. However. as concrete and ductile steel are concerned. thls
mu* be lncludcd because of the fact that the energy consumed m the plart~c or mtero-
cracked p mes zone IS more relevam than the elasttc pan.