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T-12-T
1.3
Design and Safety Factors
The safety factor is a ratio between the design stress imposed by the load sitting
static on the trailer and the minimum yield stress of the steel used in construction of
that trailer structure. For example, if the structure is built using 50,000 psi minimum
yield strength steel and the load sitting on it causes a stress level of 25,000 psi then a
2:1 safety factor would exist. THIS SAFETY FACTOR DOES NOT MEAN THAT THE
STRUCTURE CAN THEN BE USED TO CARRY TWICE THE RATED LOAD. Under
dynamic conditions, or as the trailer moves and encounters shocks, vibrations, twists
and other conditions that exist during transport, stress levels are elevated far beyond
those in the static situation.
Distributed Load is when a load is distributed evenly over the length of the trailer
deck. This would be considered as the ideal load scenario when fully loaded to rated
capacity.
Concentrated Load is one that is localized over a shorter than normal distance and
imposes greater stress in the concentrated load areas. Under these conditions, it is not
recommended to carry the full rated capacity of the trailer. Extreme concentrated appli-
cations may require additional support for the load.
1.4
Vehicle Load and Handling Limits
Vehicle handling limits can be greatly affected by the weight of a load, its place-
ment, the amount of weight distributed over the axles and whether or not the load is
secured properly.
Tow vehicle and trailer combinations are designed to provide maximum directional
control and roll stability within the constraints of highway size and weight limits. Any
combination can be rolled over by driving too fast around a curve, making too abrupt a
maneuver, or by leaving the roadway. Locking up the wheels on an axle can result in a
jackknife or trailer swing out.
One of the major contributing factors to vehicle rollover is high center of gravity on
tall loads. Extreme caution should be used in maneuvering a vehicle and trailer combi-
nation, or any unit that has a tall load. Positioning the load in a central side to side
location will enhance directional control, roll stability and braking.
You should be aware that trailers with a shorter wheel base are more prone to roll
during an abrupt lane change or quick reactions at the wheel. This tendency can be
made dramatically worse with a tall, high center of gravity load.
Operation
