Crack Paths 2012

cracks reach half the girder height, the maximumdegradation rate is still less than 20 % as

these cracks nearly penetrate the girder. On the other hand, the reduction effects of shear

cracks on the strength of the girder can be serious. As illustrated in Fig. 8, as the shear

cracks reach a size that is 2/5 of the girder height, the reduction rate can be as great as 20 %,

beyond which structural failure can occur as the required load rating factor of Eq. (2)

(where the minimumvalue of ΦC = 0.85 is adopted) is no longer satisfied. As studies on the

effects of boundary conditions and on how crack analysis can help determine the condition

factor ΦC in Eqs. (1) and (2) are still preliminary, further discussions on these topics are

omitted.

C O N C L U S I O N S

The following conclusions are drawn from the study:

(1) An analytical approach for assessing the structural integrity of aging R Cbridges using

the load rating factor of A A S H T hOas been proposed. Based on numerical studies, it is

considered that the method may provide an effective way of assessing an aging R Cbridge

based on the crack conditions in concrete and the corrosion of steel reinforcement, as well

as other structural features including the support conditions.

(2) The presence of central cracks in the R Cgirder studied has no significant effect on its

general structural behavior, but the existence of shear cracks in the girder can have a serious

effect. Whenthese shear cracks are small, the R Cgirder typically fails in a flexural failure

mode, but as the cracks become larger the beamthen fails in a shear modewith very limited

deformation, implying brittle failure.

(3) Under the simple support condition, the degradation of girder strength caused by the

existence of central cracks is rather small and can be ignored in most cases. On the other

hand, shear cracks can greatly reduce the strength of the girder. Even small shear cracks can

significantly reduce the strength of the girder, while large shear cracks may trigger brittle

structural failure, seriously endangering the structural safety of the girder.

R E F E R E N C E S

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Constructed Facilities, Vol. 20, No. 1, 14–20.

2. Tapan, M., Aboutaha, R. S. (2008). J. of Bridge Engineering, Vol. 13, No. 3,226–236.

3. Shi, Z. (2009). Crack Analysis in Structural Concrete: Theory and Applications,

Elsevier.

4. A A S H T (O2012). AASHTOLRFDBridge Design Specifications, 6th Ed., Washington,

DC.

5. JRA(2002). Specifications for Highway Bridges, Part III Concrete Bridge, Japan Road

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with Material Deterioration. Japan Society of Civil Engineers, Tokyo.

7. DIANA(2010).DIANA(FEA) User's Manual Release 9.4.2. , T N OD I A N ABV.

8. A A S H T(O2011). Manual for Bridge Evaluation, 2nd Ed., Washington, DC.

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