AASHTO Loading AASHTO Loading of either H-20 or HS-20 is based on an axle load of 32 kips. This load is divided into two tires; that is a load at each end of the axle. The tire area contact is defined in AASHTO 3.30 Tire Contact Area The tire contact area for HS 20-44 shall be assumed as a rectangle with a length in the direction of traffic of 10 inches, and a width of tire of 20 inches. Therefore, the pressure would appear to be equal to 16 kips / (10" x 20") = 80 psi or 11.5 ksf. In case you need to know, these two tires on the axle are spaced six feet apart (center-to- center) transverse to the direction of traffic and the successive axles of an HS truck are 14 feet apart along the direction of traffic. I believe impact factor is 30% max. It can be lower based on span length. The load factor rating impact factor (I) is added to all live loads to account for the speed, vibration, and momentum of vehicular traffic. The AASHTO specifications for bridge design define the impact factor as follows:
AASHTO LoadingAASHTO Loading of either H-20 or HS-20 is based on
an axle load of 32 kips.This load is divided into two tires; that
is a load at each end of the axle.The tire area contact is defined
in AASHTO 3.30 Tire Contact Area
The tire contact area for HS 20-44 shall be assumed as a
rectangle with a length in the direction of traffic of 10 inches,
and a width of tire of 20 inches.
Therefore, the pressure would appear to be equal to 16 kips /
(10" x 20") = 80 psi or 11.5 ksf.In case you need to know, these
two tires on the axle are spaced six feet apart (center-to-center)
transverse to the direction of traffic and the successive axles of
an HS truck are 14 feet apart along the direction of traffic.
I believe impact factor is 30% max. It can be lower based on
span length.The load factor rating impact factor (I) is added to
all live loads to account for the speed, vibration, and momentum of
vehicular traffic. The AASHTO specifications for bridge design
define the impact factor as follows:
![Fundamentals of Bridge Design - simnum.com · 14 4.1 Superstructure Loads36 4.2 Common Construction Materials Densities. [AASHTO,2012]37 4.3 HL-93 Design Truck Load. [AASHTO,2012]37](https://img.dokumen.tips/doc/110x75/5af4ee3d7f8b9a8d1c8ce60c/fundamentals-of-bridge-design-41-superstructure-loads36-42-common-construction.jpg)
