Download - Make design load model
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Development of Live Load Model
for Road Bridges
Korean Expressway Corporation
Choi Hyeok-jin [HOOK]
(Structure Engineer, PE)
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CON-TENTS
1. Truck Load of Countries
2. Governing Factors
3. Specification Develop-
ment
Development
of Live Load Model
For Road Bridges
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1.1 Standard Truck Load of Various Countries
1.2 Live Load Effects of Various Countries
1. Truck Load of Countries
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Standard Truck Load of Various
Countries
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Korea
National
USA
USA
Canada
Canada
EurocodeUSK
Germany
Japen
CodeTotal
Weight
MaxAxle load
1st 2nd 3rd 4th 5th
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Live Load Effects of Various Coun-
tries
(Simple Span, Moment)
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Span Length(m)
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Span Length(m)
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2.1 Goal of Live Load Model Development
2.2 Principal Factors of Live Load
2.3 Procedure for Development of a Design Live
Load Model
2. Governing Factors
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Korean Expressway Corporation
A constant safety rate across all span lengths
Goal of Load Model Development
Development of economically feasible safe load that befits bridge life cycle.
Load patterns that are easy to use in design process, and are familiar to designers.
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Korean Expressway Corporation
Principal Factors of Live Load
Distance between vehicles (= 1.2m)
Load distribution of axle load
Vehicle type [passenger car, truck]
Vehicle weight [vehicle + load weight]
Compounding affect of vehicles in tandem
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Korean Expressway Corporation
Passenger car Truck
Principal Factor of Live Load
Type/Weight of Vehicle
Compounding affects of vehicles in tandem
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Korean Expressway Corporation
Survey of vehicle loads and driving patterns
Determine the trend line by Probability Chart
Estimate maximum load effects by span length
Determine design live loadDetermine design live load
Procedure for Development
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Korean Expressway Corporation
3.1 driving patterns
3.2 Maximum load effect
3.3 Live load model
3.4 economical benefits
3. Specification Development
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Korean Expressway Corporation
• WIM ; Weigh-In-Motion
- Loop Sensor : measures
axle lengths
- Piezo Sensor : measures
vehicle speed, weight , and
number of axles.
Loop Sen-sor
Piezo Sen-sor
Data
Locker
WIM System
Survey of Vehicle Loads
※ WIM system allows a more ac-curate weight for smaller ve-hicles.
• BWIM ; Weigh-In-Motion - Use the Displacement of Bridge by Passing Car
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Korean Expressway Corporation
Driving Pattern Survey
Mixture rate Tandem rate
Survey of Driving Patterns
※We must discover the passenger car/truck mixture when
travelling in tandem.
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Korean Expressway Corporation
• using top 10%, 20% values
from weight survey data • using the Gumbel Probability
Chart - an equation can convert
probability distribution to a one-
dimensional linear formula
• Trend Line(y=a+bx) y=Gumbel probability
x=weight
Trend Line Sample Chart
Estimating Max Load Effects (1)
Maximum Load Effects by Largest single vehicle
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Korean Expressway Corporation
Groups of vehicles running in tandem
- different types running in tandem
– same types of vehicles running in tandem
P
P
T
T
18,185 1,301
1,301 193
0.84120 0.06018
0.06018 0.00893
Using a Marcov Chain
Estimating Max Load Effects (2)
Maximum Load Effects by Vehicles in tandem
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Korean Expressway Corporation
Largest single vehi-cle
Calculating load effects at variable span lengths (posi-tive moment, shear, and negative moment)
Estimating Max Load Effects (3)
Vehicles in tandem
Vehicles in tandem
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Korean Expressway Corporation
Bias factor of positive mo-ment
In order to ensure a constant safety rate over variable span
lengths we use a Bias factor calculation(M75/MDESIGN)
Con-stant safety rate
Bias Factor
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Korean Expressway Corporation
• uniformly distributed load + concentrated load.
※ span length 10m : 12ton vehicle allowable
※ span length 30m : 15ton vehicle allowable
Design Live Load
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Korean Expressway Corporation
Estimating maximum load effects for both categories, great-
est load and groups of vehicles running in tandem, using
span lengths to 200 meters.
Summary
The proposed design load includes two components :
(1) a uniformly distributed load, and (2) a concentrated load.