外文翻譯--帶肋鋼筋與混凝土之間的粘結(jié)第二部分腐蝕的效應(yīng)（英文）

1、Bond between ribbed bars and concrete. Part 2: The effect of corrosion K. Lundgren Published in Magazine of Concrete Research, see journal homepage http://www.icevirtuallibrary.com/content/journals “Permission is grant

2、ed by ICE Publishing to print one copy for personal use. Any other use of these PDF files is subject to reprint fees.” Delivered by ICEVirtualLibrary.com to:IP: 129.16.183.37On: Mon, 30 Aug 2010 14:47:28models of how

3、fast the carbon dioxide or the chloride penetrates through the concrete cover, the initiation period can be determined. By estimating the corrosion rate and the maximum allowable corrosion, the propa- gation time can be

4、determined, and thereby the service life of the concrete structure. This paper will concen- trate on models that are needed when the maximum allowable corrosion is to be determined. Then the effect of corrosion on the lo

5、ad-bearing resistance of the struc- ture needs to be determined. Corrosion of the reinforcement in concrete structures causes two effects: (1) the cross-sectional area of the reinforcement decreases. The effect of this o

6、n the load- bearing resistance is rather easy to take into account: in principle the same models as for undamaged concrete structures can be used, only with a reduced area for the reinforcement. (2) The corrosion product

7、s occupy a larger volume than the steel it was formed of. This leads to splitting stresses acting on the concrete, which might cause spalling of the cover. The latter affects the structure in several ways. On the compres

8、sed side of a structure, spalling of the cover will lead to a decrease of the internal lever arm, which in turn decreases the bending moment capacity. Furthermore, the interaction between the reinforcement and the concre

9、te is influ- enced. This interaction is commonly called the bond mechanism. Due to the effect on the bond mechanism, the deformations increase, and if the corrosion takes place in certain parts of the structure, such as

10、at sup- ports and at splices, the load-bearing resistance will be influenced. The effect of the volume increase is not so easy to take into account when calculating the load-bearing resistance of corroded reinforced conc

11、rete structures. A model of the corrosion together with a model of the bond mechanism was developed by the author in earlier work.1 The bond model, however, was shown to gener- ate energy for some special loading–unloadi

12、ng se- quences (Gustafsson P . J., pers. Comm., 2002). To avoid this undesirable effect, the formulation of the bond model was modified; see the companion paper.2In this paper, the calibration of the corrosion model is f

13、urther investigated. Moreover, the corrosion model is used together with the bond model for analyses of several tests found in the literature. Finally, the models are utilised in analyses to provide background for de- si

14、gn recommendations.Modelling of corrosion and bondThe modelling method used is specially suited for detailed three-dimensional finite element analyses, where both the concrete and the reinforcement are modelled with soli

15、d elements. Special interface ele- ments were used at the surface between the reinforce- ment bars and the concrete to describe a relation between the traction t and the relative displacement uin the interface. The physi

16、cal interpretations of the variables are as followst ¼ tn tt? ?¼ normal stress bond stress? ?u ¼ un ut? ?¼ relative normal displacement slip? ?The corrosion model and the bond model can be viewed as t

17、wo separate layers around a reinforcement bar. However, to reduce the number of nodes required to model a structure, they are integrated in one inter- face element. Due to equilibrium between the two layers, the traction

18、 t is the same in the bond and in the corrosion layer. The deformations are related asun ¼ uncor þ unbond (1)ut ¼ utbond, utcor ¼ 0 (2)where the index ‘cor’ refers to the corrosion layer, and the inde

19、x ‘bond’ refers to the bond layer. The bond model used is presented in the companion paper.Corrosion modelThe volume increase of the corrosion products com- pared to the virgin steel was modelled in a corrosion layer, as

20、 described in Lundgren.1 The volume of the rust relative to the uncorroded steel, and the corrosion penetration as a function of the time, were given as input. The corrosion was then modelled by taking time steps. The ph

21、ysical interpretation of the variables in the corrosion model is shown in Fig. 1. The free increase of the radius, namely how much the radius would in- crease if the normal stresses were zero, is calculated froma ¼

22、?r þ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi r2 þ (? ? 1) ? (2rx ? x2) p (3)where ? is the volume of the

23、rust relative to the un- corroded steel, which was assumed to be 2.0. The real increase of the radius is uncor, corresponding to a strain in the rust?cor ¼ uncor ? ax þ a (4)????????????????????????? ??????????

24、?????????????? ??????????????????????????? ?????????????????????????????? ????????????????????????????????????????????????? ????????????Fig. 1. Physical interpretation of the variables in the corro- sion modelLundgren384