ABSTRACT
The reliability of existing bridge structures is significantly affected by many factors, from which the reinforcement and structural steel corrosion together with effect of traffic action are the most important. In the case of reinforced concrete (RC) structures, the most known degradation process is corrosion of reinforcement. RC bridge members have to fulfil the conditions given in Eurocodes STN EN 1992-1-1 (2006) and STN EN 1992-2 (2007). Horizontal bridge girders are mainly subjected to bending and shear. The paper deals with reinforcement corrosion of main reinforcement (longitudinal reinforcement for bending) and stirrups (shear reinforcement) and their influence on the bending and shear resistance of the existing bridge concrete structures. The parametric study was performed.
The resistance of the RC flanged beam MRd(t) changed in time subjected to bending is given in accordance with Eurocode STN EN 1992-1-1 (2006) by formula () M Rd ( t ) = F s ( t ) ⋅ z ( t ) = A s1 ( t ) ⋅ f yd ⋅ z ( t ) = A s1 ( t ) ⋅ f yd ⋅ ( [ h − c − ϕ ( t ) 2 ] − A s1 ( t ) ⋅ f yd 2 ⋅ b eff ⋅ f cd ) https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/eq156.tif"/>
As itwas presented in Koteš et al. (2015a) and Koteš et al. (2015b), it is possible to modify formula (1) into final form for moment resistance depending only on time () M Rd ( t ) = M Rd ( 0 ) + k 1 ⋅ ( t − t 0 ) + k 2 ⋅ ( t − t 0 ) 2 + k 3 ⋅ ( t − t 0 ) 3 + k 4 ⋅ ( t − t 0 ) 4 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/eq157.tif"/>
The resistance V Rd,s(t) of the reinforced concrete rectangular cross-section with shear reinforcement (stirrups) subjected to shear is given according to Eurocodes STN EN 1992-1-1 (2006) by formula () V Rd,s ( t ) = π 4 ⋅ n s ⋅ ϕ s 2 ( t ) ⋅ z s ⋅ f ywd ( cot θ + cot α ) sin α https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/eq158.tif"/> Time dependent resistance M<sub>Rd</sub>(t) and V<sub>Rd</sub>(t). https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig265_1.tif"/>
Also in this case, as it was presented in Koteš et al. (2015a) and Koteš et al. (2015b), it is possible to modify formula (3) into final form for shear resistance depending only on time () V Rd,s ( t ) = V Rd,s ( 0 ) + k s , 1 ⋅ ( t − t 0 , s ) + k s , 2 ⋅ ( t − t 0 , s ) 2 https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/eq159.tif"/>
The minimal resistance of the reinforced concrete rectangular cross-section is given by the force VRd,c(t), which is valid for member without shear reinforcement () V Rd,s ( t ) = π 4 ⋅ n s ⋅ ϕ s 2 ( t ) ⋅ z s ⋅ f ywd ( cot θ + cot α ) sin α https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/eq160.tif"/>
From the results of parametric study follows, that the reinforcement corrosion has significant influence on change of resistances in time. The results show that the bridge beam is more inclinable to change (decrease) of shear resistance than to moment resistance in time due to reinforcement corrosion. Because the failure in shear is more brittle in contrast to ductile (plastic) failure in bending, it is needed to pay higher attention to this problem.
