Crack Paths 2012

Load-Carrying Capacity

Rating factors representing the load-carrying capacity of the girder are computed using the

nominal rating factors obtained numerically as the ratio of the maximumlive load to the

design live load, assuming various sizes for the existing cracks. Figures 7 and 8 summarize

the relationship between the rating factor and the depth of existing cracks. Analytical results

obtained by the L R F Dmethod of Eq. (2) are also plotted in these figures. As shown in the

figures, the effects of the existing cracks on the load-carrying capacity depend not only on

the type of cracks, but also on the support conditions.

Under the simple support condition (HFM), the strength degradation of the girder due to

the existence of central cracks is generally quite limited, as clearly shown in Fig. 7. While

the degradation effects on the girder strength can be completely ignored before the central

6.0 Non 1/5H 2/5H 3/5H 4/5H 1H F E _ H F M FE_HFF Depth ofcentral cracks (H = height of girder) γd=11..037

0.0

Eq.1(Φc=1.00) .1 =0 85 γd=1.7 γd = .0

γd

01.468024

2345.0

γd=1.0

(γd= 1.0)

=1.3

(a)

(b)

γd=1.7

d = 1 . 3

F E _ H F M

(γd = 1.3)

(γd=1.7)

01.0

0.2

1.68 Non 1/5H 2/5H 3/5H 4/5H 1H

Depth of central cracks (H = height of girder)

Fig. 7 Relationship of rating factor and size of central cracks [(a) FE analysis results and

(b) comparison between FE analysis (HFM)and L R F Dresults]

Non 1/5H 2/5H 3/5H 4/5H 1H F E _ F M FE_HFF Depth ofshear cracks (H = height ofgirder) γd=1.307 a)

(b)

γd=1.0

γd

3456.0

γd=1.7

=1.0

Eq.1(Φc ==01.8005)

γd =1.3

γ

=1.7

d

γd=1.3

-21012.0

F E _ H F M F Depth of shear cracks (H = height of girder) (γd =11..307)

-21012.050505050 Non 1/5H 2/5H 3/5H 4/5H 1H

Fig. 8 Relationship of rating factor and size of shear cracks [(a) FE analysis results and

(b) comparison between FE analysis and L R F Dresults]

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