Load Rating 1

LOAD RATING BY MANUAL LOAD RATING BY MANUAL CALCULATIONSCALCULATIONS

RC_ SLAB BRIDGE RATING

Amjad Waheed, PE

Ohio Department of Transportation

Load Rating Seminar 2

Agenda – Day 1Agenda – Day 18:00 am – 8:15 am Introductions and House Keeping8:15 am – 8:45 am Session 1: Load Rating Basics8:45 am – 9:30 am Session 2: Basic Load Rating

Calculations9:30 am – 9:45 am Break9:45 am – 11:45 am Session 3: Example – Load Rating

Concrete Slab Bridge 11:45 am – 12:00 pm Questions12:00 pm – 1:00 pm Lunch1:00 pm – 2:30 pm Session 4: Example – Load Rating Steel

Beam Bridges2:30 pm – 2:45 pm Break2:45 pm – 3:45 pm Session 4: Example – Load Rating Steel

Beam Bridges (Con’t)3:45 pm – 4:00 pm Questions

Load Rating 3

What is Load Rating?What is Load Rating?The safe live load carrying capacity of a highway structure is called its load rating.

RF = C – A1 * D

A2 * (L + I)

A1 = Factor for dead loads

A2 = Factor for live load

C = Capacity of the bridge

D = Dead loads

I = Impact loads

L = Live loads

How to calculate the rating factor (RF)

RF = Capacity for (L+I)

Actual (L + I)

Load Rating 4

Factors for LFR Load RatingFactors for LFR Load Rating

Rating TypeRating Type AA11 = Factor for = Factor for

dead loadsdead loadsAA22 = Factor for = Factor for

live loadlive load

InventoryInventory

* Design level* Design level

1.3 2.17

OperatingOperating 1.3 1.3

Ref: AASHTO Manual for Condition Evaluation of Bridges 1994

Rating Factor EquationRating Factor Equation

Load Rating Seminar 5

R.F. = C – A1 * D

A2 * (L + I)

Inventory Rating

R.F. = C – 1.3 * D

1.3 * 1.67 * (L + I)

R.F. = C/1.3 – D

1.67 * (L + I)

A1 = 1.3A2 = 2.167 = 1.3 * 1.67

Rating Factor EquationRating Factor Equation

Load Rating Seminar 6

R.F. = C – A1 * D

A2 * (L + I)

Operating Rating

R.F. = C – 1.3 * D

1.3 * (L + I)

R.F. = C/1.3 – D

(L + I)

A1 = 1.3A2 = 1.3

Load Rating 7

Single-span slab bridgeSingle-span slab bridge

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AASHTO Standard Specification for Highway Bridges

3.24.3.2 CASE B – Main Reinforcement Parallel to Traffic

For wheel loads, the distribution width

E = 4 + 0.06*S 7’

S = Effective Span length in feet

3.24.1

E = 4 + 0.06*13 = 4.78’ S = 13’

Live Load Distribution Factor

Load Rating Seminar 22

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AASHTO Standard Specification for Highway Bridges

3.8.2 Impact Formula

The amount of impact allowance, I, as a fraction of the live load

I = 50 / (L + 125) 0.3

L = Effective Span length in feet

I = 50 / (13 + 125) = 0.362 Use I = 0.3

Impact Load (Impact Factor)

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Summary of Rating ResultsSummary of Rating Results

Load Rating Seminar 31

Load Weight (GVW) Tons

M L+I

ft. k/ft

R.F. = (28.09/

M L+I)

Safe Load Tons

% Ohio Legal

HS 20 36 14.1 1.992 71.20 -----2F1 15 8.8 3.192 47.90 319%3F1 23 10.4 2.700 62.10 270%4F1 27 10.9 2.577 69.60 258%5C1 40 10.4 2.700 108.00 270%

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Material StrengthsMaterial Strengths

Load Rating Seminar 37

BMD - Figure 904

Material StrengthsMaterial Strengths

Load Rating Seminar 38

BMD - Figure 905

Load Rating 39

Learning CurveLearning Curve

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ODOT Rating Contact InformationODOT Rating Contact Information

Amjad Waheed, PE614.752.9972 (awaheed@dot.state.oh.us)

Shelton A. Howard, PE614.752.9975 (showard@dot.state.oh.us)

Richard C. Irwin, PE614.752.9977 (richard.irwin@dot.state.oh.us)

Cindy Wang, PE614.466.1973 (cindy.wang@dot.state.oh.us)

Load Rating 41

That’s all folks