Civil Engineering Reference
In-Depth Information
Q
5
'
a
c
4
'
b
8
'
FIGURE E4.12
These forces are checked against the usual allowable stresses increased
by 50%.
4.4.5.2
Other Loads for Overall Lateral Stability
The overall stability of the superstructure against wind, nosing, and centrifugal forces
must also be ensured. The stability of spans and towers should be calculated using a
live load, without impact, of 1200 lb/ft.
∗
On multiple track bridges this live should be
placed on the most leeward track on the bridge. A 50% increase in allowable stress is
permissible when determining stresses anchor rods or other members resisting overall
instability of the span.
4.4.6 P
EDESTRIAN
L
OADS
Typical walkways for steel railway bridges consist of a steel grating or other system
with nonslip surfaces. The walkway components are designed for a load of 85 psf and
maximum deflection of 1/160 of the walkway span length. Guardrails for pedestrian
walkways are typically designed for railing and postloads of 200 lb applied laterally
or vertically at the location of maximum effect.
4.4.7 L
OAD AND
F
ORCE
C
OMBINATIONS FOR
D
ESIGN OF
S
TEEL
R
AILWAY
S
UPERSTRUCTURES
AREMA does not provide explicit load combinations but incorporates combinations
in various design recommendations (Sorgenfrei and Marianos, 2000).
Table 4.5
out-
lines load combinations that apply to steel superstructure design found in various
recommendations of AREMA.
∗
This represents a uniform load of empty rail cars.
