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# LOAD RATING BY MANUAL CALCULATIONS

## Presentation on theme: "LOAD RATING BY MANUAL CALCULATIONS"— Presentation transcript:

LOAD RATING BY MANUAL CALCULATIONS
RC_ SLAB BRIDGE RATING Amjad Waheed, PE Ohio Department of Transportation Load Rating

Agenda – Day 1 8:00 am – 8:15 am Introductions and House Keeping
8:15 am – 8:45 am Session 1: Load Rating Basics 8:45 am – 9:30 am Session 2: Basic Load Rating Calculations 9:30 am – 9:45 am Break 9:45 am – 11:45 am Session 3: Example – Load Rating Concrete Slab Bridge 11:45 am – 12:00 pm Questions 12:00 pm – 1:00 pm Lunch 1:00 pm – 2:30 pm Session 4: Example – Load Rating Steel Beam Bridges 2:30 pm – 2:45 pm Break 2:45 pm – 3:45 pm Session 4: Example – Load Rating Steel Beam Bridges (Con’t) 3:45 pm – 4:00 pm Questions Load Rating Seminar

What is Load Rating? RF = RF =
The safe live load carrying capacity of a highway structure is called its load rating. How to calculate the rating factor (RF) A1 = Factor for dead loads A2 = Factor for live load C = Capacity of the bridge D = Dead loads I = Impact loads L = Live loads Capacity for (L+I) RF = Actual (L + I) C – A1 * D RF = A2 * (L + I) Load Rating

Factors for LFR Load Rating
Rating Type A1 = Factor for dead loads A2 = Factor for live load Inventory * Design level 1.3 2.17 Operating Ref: AASHTO Manual for Condition Evaluation of Bridges 1994 Load Rating

Rating Factor Equation
Inventory Rating C – A1 * D R.F. = A1 = 1.3 A2 = = 1.3 * 1.67 A2 * (L + I) C – 1.3 * D R.F. = 1.3 * 1.67 * (L + I) C/1.3 – D R.F. = 1.67 * (L + I) Load Rating Seminar

Rating Factor Equation
Operating Rating C – A1 * D R.F. = A1 = 1.3 A2 = 1.3 A2 * (L + I) C – 1.3 * D R.F. = 1.3 * (L + I) C/1.3 – D R.F. = (L + I) Load Rating Seminar

Single-span slab bridge
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Live Load Distribution Factor
AASHTO Standard Specification for Highway Bridges CASE B – Main Reinforcement Parallel to Traffic For wheel loads, the distribution width E = *S  7’ S = Effective Span length in feet 3.24.1 E = *13 = 4.78’ S = 13’ Load Rating

Load Rating Seminar

Impact Load (Impact Factor)
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 / ( ) = 0.362 Use I = 0.3 Load Rating

Load Rating Seminar

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Summary of Rating Results
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 40 108.00 POSTING NOT REQUIRED Load Rating Seminar

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Material Strengths BMD - Figure 904 Load Rating Seminar

Material Strengths BMD - Figure 905 Load Rating Seminar

Learning Curve Load Rating

ODOT Rating Contact Information Amjad Waheed, PE Shelton A. Howard, PE Richard C. Irwin, PE Cindy Wang, PE Load Rating

That’s all folks Load Rating

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