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Calcimator

Bridge Load Rating Calculator

Calculate bridge load rating factor using LRFR methodology. Determines if a bridge passes HL-93 design loading and whether posting is required.

Inputs

kip
kip
kip

Results

Rating Factor (RF)

1.34

Rating (Tons)

48.35 tons

≈ 8 elephants

Passes HL-93

1

Posting Required0
Operating Rating Factor1.74
Available Capacity312.5 kip
How to Use This Calculator
  1. Enter member capacity (C), dead load effect (D), live load effect (L), and dynamic load allowance.
  2. Set dead load factor and live load factor per AASHTO LRFD.
  3. Review the load rating factor — values ≥ 1.0 indicate the bridge passes for the design load.

How the result changes with Member Capacity (C)

Member Capacity (C)Rating Factor (RF)Rating (Tons)Passes HL-93
1,0093.53127.08 tons1
3,50714.26513.43 tons1
6,50427.14977 tons1
9,00137.871,363.21 tons1

What each input means

Member Capacity (C)
Nominal capacity of the controlling member (moment or shear) in kips.
Dead Load Effect (D)
Unfactored dead load effect on the controlling member from self-weight, wearing surface, and attachments.
Live Load Effect (L)
Unfactored live load effect from the rating vehicle (HL-93 or permit truck) on the controlling member.
Dynamic Load Allowance (1+IM)
Dynamic impact factor applied to live load. Standard HL-93 uses 1.33 (33% impact). Fatigue uses 1.15.
Dead Load Factor (γ_D)
LRFD dead load factor. Inventory level = 1.25; strength limit state default.
Live Load Factor (γ_L)
LRFD live load factor. Inventory level = 1.75; operating level = 1.35; permit = 1.15-1.30.

How this is calculated

Worked example, using the default values

  1. Identify Input Parameters
    4 parameters
    Member Capacity (C) = 500, Dead Load Effect (D) = 150, Live Load Effect (L) = 100, Dynamic Load Allowance (1+IM) = 1.33 = 6 input(s) provided
  2. Calculate Rating Factor
    Rating Factor
    1.343 = 1.343
  3. Calculate Rating
    Rating
    48.35 = 48.35
  4. Calculate Passes HL-93
    Passes HL-93
    1 = 1
  5. Calculate Posting Required
    Posting Required
    0 = 0
  6. Calculate Operating Rating Factor
    Operating Rating Factor
    1.74 = 1.74

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