Vehicle and Traffic Consideration CEE 320 Steve Muench 5/9/ Highways Airports

Load Quantification For Highways Equivalent Single Axle Load (ESAL) Converts wheel loads of various magnitudes and repetitions ("mixed traffic") to an equivalent number of "standard" or "equivalent" loads Based on the amount of damage they do to the pavement Commonly used standard load is the 18,000 lb. equivalent single axle load Load Equivalency Generalized fourth power approximation will give ESAL Factors

5/9/ Wheel Configuration (Trucks)

Typical Load Equivalent Factor LEFs Notice that cars are insignificant and thus usually ignored in pavement design. 5/9/2015 4

Load Quantification For Airports Equivalent Single Wheel Load (ESWL) Converts wheel loads of various magnitudes Configurations, and repetitions (“Different Gears") to an equivalent number of "standard" or "equivalent" loads Based on the amount of damage they do to the pavement

Mixed Highway Traffic Analysis

Equivalent Axle Load Computation

Example LEF (ESAL) Example Assume a logging truck has three axles: Truck tractor Steering axle (single axle) = 14,000 lb (62.2 kN) Drive axle (tandem axle) = 34,000 lb (151.1 kN) Trailer Pole trailer axle (tandem axle) = 30,000 lb (133.3 kN) The total equivalent damage by this truck (pt = 3.0, SN = 3): is Steering 14,000 lb=0.47 ESAL, Drive 34,000 lb=1.15 ESAL, Pole 30,000 lb=0.79 ESALTotal=2.41 ESAL

Highway Axle Configuration

Sample Conversion

Traffic Growth

Equivalent single wheel load for Dual Tire (Metric) Where: P is the wheel load Kg, S is the center to center distance between the two wheels in cm, d is the clear distance between two wheels in cm, and z is the desired depth in cm.

Equivalent single wheel load for Dual Tire Example: Find ESWL at depths of 5cm, 20cm and 40cm for a dual wheel carrying 2044 kg each. The center to center tire spacing is 20cm and distance between the walls of the two tires is 10cm. P P d s d/2 2S

Equivalent single wheel load for Dual Tire Solution: For desired depth z=40cm, which is twice the tire spacing, ESWL = 2P=2*2044 = 4088 kg. For z=5cm, which is half the distance between the walls of the tire, ESWL = P = 2044kg. For z=20cm, Therefore, ESWL = antilog(3.511)= kg

Equivalent single wheel load for Dual Tire (Pound) P d /2 d sdsd d/2 h =30 in Where: P d is the dual wheel load lb, S d is the center to center distance between the two wheels in inches, d is the clear distance between two wheels in inches, and z is the desired depth in inches. A0

Equivalent single wheel load for Dual Tire (Pound)

Equivalent single wheel load (CBR) Procedure Tail Nose Axis of Fuselage 6’ 3’’ 46’’ 64’’ 6’ 3’’ 18’ 2’’ 9’ 9’’ Boeing 747

CBR vs Thickness Pavement Thickness Inches CBR %

ESAL Tables See Handouts