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**LOAD RATING BY MANUAL CALCULATIONS**

RC_ SLAB BRIDGE RATING Amjad Waheed, PE Ohio Department of Transportation Load Rating

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**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

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**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

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**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

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**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

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**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

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**Single-span slab bridge**

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Load Rating Seminar

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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

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Load Rating Seminar

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**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

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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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Load Rating

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Material Strengths BMD - Figure 904 Load Rating Seminar

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Material Strengths BMD - Figure 905 Load Rating Seminar

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Learning Curve Load Rating

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

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That’s all folks Load Rating

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