Description of Concrete Durability Damage Process

Vol.11 No.3 2006 653 -656WUJNSWuhan University Journat of Natural SciencesArticle ID; 1007 :1202(2006)03-0653-04Description of Concrete DurabilityDamage Process0 Introduction口CHEN Yueshun, WEI Junt , .ZHAO Xiaolongn city infrastructures reconstruction, the concrete struc-School of Civil Engineering and Mechanics， Huazhongtures are common. So it is necessary to carry out the re-University of Science and Technology, Wuhan 430074,Hubei, Chinasearch on the concrete structure health monitoring, structuraldiagnosis and life span evaluation'lJ .The current health monitoring and structural diagnosisAbstract: Based on the dammage mechanics, the concretedamage grade o[ relalive stable environment in tneasurablemethod of concrete structures primarily contain two majortypes, one is to supervise and control them timely at service,ewolving model and corresponding failure rule is constructedthen pass the collection of the structural dynamic displace-based on tbe damage grade fore defined. Tberefore, the con-ments, velocity and acceleration, via numerical analysis to thecrete health slatus and the residual life span can be esessedaccording lo the measured damage grade. It is propitious t0monitor and evaluate continuously the health progress of thedrive the devcloprment of concrete durability assesment andstructure[2-5]; another is to peridically or aperidically checklife span forecast. Its fensibility o[ concrcle damage processdescription and health assment is validated with the exam-and measure the structure non-destructively, and to analyzeple in this paper, in which the damage stale is described withthe examination data 10 assess the structure progressive-the ultrasound velocity attenuation, and the freeze thawly6-10]. Each of them has its superiority and Cdrawbacksprocess is regarded as the concrete durability degradation in-fluencing factor to reflext the concrete durability degradationwhich should be considcred in the further research and devel-process,opment-1.121.Key words : concretc; durability danage; life span assess-Excepl the paroxysmal process, the breakage of concretement; health monitoring; ultrasonic velocitystructure is a gradual procs-1] , and the structural health de-CLC number: TU 317*.5terioration should be closely linked with this process. The :concrete structural gradual failure exhibits mainly its durabilityfailre[13]. Concretely, it includes the concrete material dura-bility deterioration, reinforcement steel material durabilty deterioration, and the bond strength between concrete and rein-Received date; 2005 10-11Foundation item: Supportod by the National Ntural Science Foun-forcement lost gradually. The latter two factors are interrelat-dation of China(50278039), the Natural Scicnce Foundation of Hubeied closcly with the concrete material durability deterioration.Provience of China ( 2004ABA062) and Chenguang Program ofNo matterete material durabilityWuhan Crty(2005003059 29)Biography: CHEN Yueshun(1975-). male, Ph, D. candidate. re-deteriorati中国煤化工t exhibits as the inter-search direction; the durability of concrete. E-mail:chyushli@ pubic.wh. hb. ennal structYHC N M H Gon, cracks propaga-t To whom correspondence should be ndressed E-mail;junewei@ion-14,15].public. wh. hb. cn653random tiny cracks.1 Concrete Damage StateTaking the tiny unit in the concrete construction asthe research object, at the initial moment, the damageDetecting and catching the concrete damagc, condelects on the tiny unit are8()= > 8i(o)，and thestructing the concrete damage evolving model, then theexternal stress on the unit is o (t). At arbitrary momentdurabllity deterioration of concrete structure can be moni-8(1) = > δ(t)，the darmage defects in the tiny unittored, and the assessment on the remaining lifc span ofconcrete structures will be realized.areo (t), and the outside stress on the unit is shown inSuppose concrete be an isotropic system includingFig. 1.↑↑↑↑↑↑↑↑↑↑8(1)↑↑↑↑↑↑↑↑↑↑F8{() _σ()(2)Fg. 1 Concrete durability breakage unit model(a) The damage at the initial moment; (b) The damagc at momentFor the concrete gradual breakage are the results ofunstable crack propagation of the defects δ% (t) in the unit2 The ConcreteDamage Evolvingwhich arise from the influence of various factors, we reEquation and Damage Failure Criteriongard the dispersive defects as a uniform field, and evalu-ate whole the effects of all defects. So the material dam-The material damage evolving equation rlflected pri-age grade can be defined asmarily the damage grade change with the time. Using theZ8(t)damage grade defined in the Eq. (1) and the damage me-D= D(8,1) =(1)chanics principle, the concrete damage evolving equation1- 28"(o)can be established,f= f(Do,D,D,t)(3)where, t is the time parameter,Z8 (1) describes thewhere, D。,D is the damage grade al the initial momentinner resisting state of the concrete at arbitrary moment,and arbitrary moment t respectively, D is the change rate28(n) is the damage state of the concrete umnit at theof damage grade.initial moment. Obviously, the structural damage gradeAlong with the developing of the damage, the deg-D reaches: 0300_ q H40自1=46.3.4,=0.001 8.N=150 。40ge 60E 30|20100 150 200 250 300100 150 200 25 ) 300NF'g. 4 Damage evolving rule of freeze-thaw(a) D60,H60; (b) D40.H40D: Damage grade, N: Freeze thaw cycle numbersthe concrete by the method in the text. For the interac-(1):147-158.tion of multifactors the evaluation of damage grade still6] Petrou M F,Perdikaris P C,Duan M. 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