Assessment of Highway Bridges

Francesco Incelli – Bridge Engineer, Midas UK

Assessment of Highway Bridges

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Assessment of Highway Bridges

Content

Introduction to BD21

Modelling using Midas Civil Steel Composite Wizard

BD21 Loading Definition (HA only, HA+HB)

Automatic and User define Combinations for live loading to BD21

Identification of worst load patterns using Moving Load Tracer

Extraction and cross checking of results and methods to separate the effect of HA and HB

loading

BD21 Loading

BD21 cl. 5.18 Loaded length up to 50m

BD21 cl. 5.18/ BD50 cl.2.3 Loaded length up to 1600m

BD21 cl. 5.18 Knife Edge Loading or KEL

BD21 cl. 5.20 to 5.22 Reduction Factors for UDL and KEL

BD21 cl. 5.23 Adjustment Factor

BD21 cl. 5.28 Recently Assessed Bridges

BD21 cl. 5.24 Lane Factors

BD21 Loading

BD37 cl. 6.3

BD21 Loading

BD37 cl. 6.3 BD21 cl. 5.35 & 5.36

Reduction factor K (BD21 cl.5.20, figure 5.2 to 5.7)

Hp Mp Lp Hg Mg Lp

H= High Traffic

M= Medium Traffic

L=Low Traffic

p= Poor Surface

g= Good Surface

K = function(L, Hp, Mp, Lp, Hg, Mg, Lg, Load Level)

BD21 Factors

BD21 Factors

Adjustment factor AF (BD21 cl.5.23)

AF = function(L, aL)

BD21 Factors

Lane Factors (BD21 cl.5.24)

BD21 Combined Factor

Adjusted Loading (BD21 cl.5.25 Bridge Specific Live Loading)

Adjusted Loading = (UDL or KEL)x (K/AF)xLf

Combined Lane Factor

BD21 Loaded Length and Influence Line

Loaded Length and Influence Line

LMy=Loaded length for My-

LFz=Loaded length for Fz+

Considerations: Forces and Moments

• 1 Influence Line = 1 Loaded Length (L).

• 1 Location = 6 Influence Lines (Fx,y,z &

Mx,y,z)

So for one location there are:

• 6 Loaded Lengths

• 6 K Factors

• 6 AF Factors

What if the sections are 10 or 20?

BD21 Verifications

Verification of Structural Adequacy (BD21 cl.3.20)

Note

• The standard value of gf3 shall be taken as 1.1

• gf3, gfl, gm may vary for different structures and material

BD21 HA+HB (BD37)

Combined HA+HB loading

BD21 Assessment Summary

Assessment Summary Table (BD86 cl 3.51 & 3.52)

Assessment

Resistance

Effect

ConsideredUnits

30 Units HB

Assessment

Load Effects

Assessment

Dead & SD Load

Effects

HA+HB EffectHA Assessment

Load EffectsReserve Factor HB Rating

Reserve factor w/o HA

Loading

HB Rating

w/o HA

Element No Element description

RA* - - S* SD

* SHA+HB* SHA

* 30xYSV 30xY*SV

361 Main Girder-Sagging 8400 My kNm 3895.02 3346.22 5156.74 1261.72 0.97 29.20699 1.30 39

410 Main Girder-Hogging -10000 My kNm -3603.4 -4594.72 -5522.59 -1919.19 0.97 29.02334 1.50 45

390 Main Girder-Shear -1500 Fz kN -702.8 -664.04 -1043.56 -340.76 0.70 21.1383 1.19 36

BD21 Assessment Flowchart

Identify location

Decide load level

Calculate influence line for desired effect

Determine loaded length

Calculate UDL/K/AF

Manually create Static Load case for specific

location and effect

Apply lane factor

Check structural adequacy

Determine the rating

Repeat for next location or effect

BD21 Assessment Flowchart

Lodcase name Element no Effect Considered Loaded LengthUDL KEL K AF (K/AF) Adjusted UDL Adjusted KEL

LC-250Mymax-28.75 250 Mymax 28.8 m 35.40 120 0.91 1.26 0.72 25.59 86.75

LC-35Mymin-39 35 Mymin 39.0 m 28.86 120 0.91 1.02 0.89 25.67 106.74

LC-68Fzmax-34 68 Fzmax 34.0 m 31.64 120 0.91 1.14 0.80 25.30 95.96

LC-156Fzmin-26 156 Fzmin 26.0 m 37.87 120 0.91 1.32 0.69 26.07 82.60

LC-95Mymax-21 95 Mymax 21.0 m 43.70 120 0.91 1.44 0.63 27.67 75.99

LC-344Mymin-20.5 344 Mymin 20.5 m 44.41 120 0.91 1.45 0.63 27.90 75.39

LC-410Fzmax-39 410 Fzmax 39.0 m 28.86 120 0.91 1.02 0.89 25.67 106.74

LC-253Fzmin-37 253 Fzmin 37.0 m 29.90 120 0.91 1.07 0.85 25.45 102.15

LC-249Mymax-36.5 249 Mymax 36.5 m 30.17 120 0.91 1.08 0.84 25.41 101.06

LC-10Mymin-37.8 10 Mymin 37.8 m 29.47 120 0.91 1.05 0.87 25.53 103.94

LC-1Fzmax-27.6 1 Fzmax 27.6 m 36.39 120 0.91 1.29 0.71 25.76 84.97

LC-9Fzmin-39.5 9 Fzmin 39.5 m 28.62 120 0.91 1.01 0.90 25.75 107.96

LC-251Mymax-11.25 251 Mymax 11.3 m 66.38 120 0.91 1.46 0.62 41.38 74.79

LC-36Mymin-5 36 Mymin 5.0 m 114.30 120 0.91 1.46 0.62 71.24 74.79

LC-69Fzmax-3.4 69 Fzmax 3.4 m 148.00 120 0.91 1.46 0.62 92.24 74.79

LC-157Fzmin-3 157 Fzmin 3.0 m 160.94 120 0.91 1.46 0.62 100.31 74.79

LC-96Mymax-12.3 96 Mymax 12.3 m 62.53 120 0.91 1.46 0.62 38.98 74.79

LC-345Mymin-18 345 Mymin 18.0 m 48.45 120 0.91 1.46 0.62 30.20 74.79

LC-411Fzmax-5.9 411 Fzmax 5.9 m 102.30 120 0.91 1.46 0.62 63.76 74.79

LC-254Fzmin-8 254 Fzmin 8.0 m 83.42 120 0.91 1.46 0.62 51.99 74.79

LC-250Mymax-9 250 Mymax 9.0 m 77.09 120 0.91 1.46 0.62 48.05 74.79

LC-11Mymin-19 11 Mymin 19.0 m 46.73 120 0.91 1.46 0.62 29.12 74.79

LC-2Fzmax-19.5 2 Fzmax 19.5 m 45.92 120 0.91 1.46 0.62 28.62 74.79

LC-10Fzmin-17 10 Fzmin 17.0 m 50.34 120 0.91 1.46 0.62 31.38 74.79

LC-252Mymax-60 252 Mymax 60.0 m 23.90 120 0.91 1.00 0.91 21.75 109.20

LC-37Mymin-40 37 Mymin 40.0 m 28.38 120 0.91 1.00 0.91 25.82 109.20

LC-70Fzmax-55 70 Fzmax 55.0 m 24.11 120 0.91 1.00 0.91 21.94 109.20

LC-158Fzmin-42 158 Fzmin 42.0 m 27.46 120 0.91 1.00 0.91 24.99 109.20

LC-97Mymax-41 97 Mymax 41.0 m 27.91 120 0.91 1.00 0.91 25.40 109.20

LC-346Mymin-45 346 Mymin 45.0 m 26.22 120 0.91 1.00 0.91 23.86 109.20

LC-412Fzmax-55 412 Fzmax 55.0 m 24.11 120 0.91 1.00 0.91 21.94 109.20

LC-255Fzmin-51 255 Fzmin 51.0 m 24.30 120 0.91 1.00 0.91 22.11 109.20

LC-251Mymax-53 251 Mymax 53.0 m 24.20 120 0.91 1.00 0.91 22.03 109.20

LC-12Mymin-68 12 Mymin 68.0 m 23.61 120 0.91 1.00 0.91 21.48 109.20

LC-3Fzmax-49 3 Fzmax 49.0 m 24.77 120 0.91 1.00 0.91 22.54 109.20

LC-11Fzmin-57 11 Fzmin 57.0 m 24.03 120 0.91 1.00 0.91 21.87 109.20

Midas Civil BD21

How can Midas Civil help our workflow?

BD21 Assessment Flowchart

Define Parameters

•Decide Load level

• Identify Structure Category

Create Moving Load Cases

•Define vehicle and Loadcases

Check structural adequacy

• Identify Location

• Calculate Influence line for desired effect

• Determine Loaded length

• Calculate UDL/K/AF

• Apply lane factor

Complete Assessment Summary

•Determine the rating

Midas Civil BD21

Conclusions

• Reduced number of load case to cover all possible live traffic scenarios

• Enhanced identification of loading patterns with Moving Load Tracer

• Easy and reliable separate calculation of HA and HB effects for a given loading pattern

• Results can be always checked and verified to confirm reliability of Adjusted Loading calculated by the software

Thank You!

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uksupport@midasuser.com

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Assessment of Highway Bridges