Study On Degradation Of Bond Properties Of Corroded Reinforced Concrete And Its Influence To The Flexural Stiffness Of Beam

The well bond characteristic is the important basic of the teamwork between steeland concrete, and the durability about bond is more focused with the occurring ofdurability problem in practical engineering. Many studies show that steel-bar corrosionis one of the most important factors affecting concrete durability and deteriorating thebond characteristic as well. However, it’s necessary to continue making more studieson this topic because of its complex mechanism, numerous influencing factors anduncompleted theoretical system.By using the quick steel-bar corrosion principle, this paper first obtains twogroups corroded specimens with different diameters (d=12and d=18) and differentcorrosion percentage. Then the distribution and width of the corrosion expansivecracks is inspected by using the non-destructive Industrial Computed Tomography(ICT).At last, bond-slip characteristic is investigated through pullout experiment.By using ICT, the distribution and extension situation of the corrosive expandingcrack was observed: the width of cracks becomes narrower from the inside to theoutside on the condition that the cracks have not penetrated the specimen surface,otherwise, the width become wider.The influence of corrosion to bond characteristic is studied according the pull-outtest. The results show that all specimens fail in a split way. The change feature of theultimate loads is: when the corrosion rate is lower than a critical value, the ultimateloads become larger with growth of the corrosion, but it begins to reduce when thecorrosion is higher than the critical value. At the same time, by combining theexperiment results of this paper and those existing values at home and abroad, amulti-parameter calculate model of corrosion reinforced concrete ultimate bond stressis put forward.By pasting the strain gauge in the reinforced bars, the strains of the reinforcedbars in the pull-out tests are collected. And through analyzing those data, the bond-slipconstitutive relation is got.At the last, by analyzing the influence mechanism of the bond characteristicdegradation to the flexural stiffness of beam, the inharmonious coefficient of steel barsstrain m, the revised asymmetrical coefficient of steel bars between cracks ψ’and thereduction coefficient of effective height γ are taken into account to calculate the flexural stiffness of a corrosion beam.