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

(71 Damage meehanncr models
Models based on damaxe theory are relrtzvelv recent. erpec~ally on concrete The
method 8s based on the ldsa (ha damage occurs u an ~mvcn~ble dcgmdelon uf thc
mnlenal under deformanon. A damage pameter as rnuoduccd as ;l scalar or vcctonsl
funcr~on of thus degndatlon process. The degadauon pmesr IS a contlnuaur and
:lobs1 pracenr and doer not constdcr only degmdatrcn wlthln n dehult l~kr the
fmaurc mechanics concept
(81 Staehastlc models
The frdcture pmcrs withon the malnr of concrete IS formulated urmg rrochast!~
farmul~ulon Concrete 8s modelled u a group of cauplsd elements wllh two or three
different phases. A lopnthm~c relalan between rhe reststance of concrete and rtrerr
or rtraln nle can be formulated.
23.2. Strain Rate For Various T yp alLoading
In men1 years. mspccmble atlentlon has been glven to the influence of rtmln rate or
stress nte an the msshvn~cal pmpnlcr of concrete. relnforclng $reel. and pre-nrernng
steel. Steel and concrctc wdl be tw~tcd 8" two rubwquent recuonr. The prerentsrlon or
the data will be such [ha a deslgn engtneer ern use such panmeters m sample hand
cnlculrnons and m n llmttcd manner also 8" advanced computer codcs. The propcnlcs
will be gwen ~n graphs and or m fununnlonal farm with rerpea to stnm or stress nte.
Table 2.1 gwes some global est~mares of rrraln nter whlch acur dunng vanaur
types of loalng. As reponed ~n CEB (1988) repon No. 187, lhev values are not expen
entlmater and have lo be delermmned more exactly for rplfic structures and load~ng