Computation of Applied Forces
- Railroad live load and lateral forces.
a. For specific applications of the Coopers E80 live load refer to Figure 2 which illustrates Plan Number 710001 “LIVE LOAD PRESSURE DUE TO COOPER E80”. Supplemental information and sample calculations are provided in the Appendix pages A-1 through A-4.
- Dead load.
a. Spoil pile: must be included assuming a minimum height of two feet of soil adjacent to the excavation.
b. Track: use 200 lbs/linear ft for rails, inside guardrails and fasteners.
c. Roadbed: ballast, including track ties, use 120 lb per cubic foot.
- Active earth pressure.
a. The active earth pressure due to the soil may be computed by the Coulomb Theory or other approved method.
b. The active earth pressure at depth “za” is:
PA = KA za , where KA = tan2(45 - )
za = depth of soil influencing the active pressure.
- Active earth pressure due to unbalanced water pressure.
a. When bulkheads are used for waterfront construction, the bulkhead is subjected to a maximum earth pressure at the low water stage. During a rainstorm or a rapidly receding high water, the water level behind the bulkhead may be several feet higher than in front of the bulkhead.
b. Drained conditions in backfill apply when clean sand or clean sand and gravel are used and adequate permanent drainage outlets are provided. Where drained conditions exist, the design water level may be assumed at the drainage outlet elevation.
- Active earth pressure due to surcharge load.
The active earth pressure due to surcharge load q’:
PU = KAq’, where KA = tan2(45 - )
- Passive earth pressure.
The passive earth pressure, Pp, in front of the bulkhead may also be computed by the Coulomb Theory.
Pp = Kp zp, where KP = tan2(45 + )
zp = vertical distance beginning one foot below dredge line but not to exceed embedment depth
- Pressure due to embankment surcharges.
Conventional analysis (Rankine, Coulomb, or Log-Spiral) should be used to determine the additional surcharge from embankment slopes.
- Additional analysis for centrifugal force calculations as described in AREMA Chapter 15, Part 1, Section 1.3, Article 1.3.6 Centrifugal Loads are required where track curvature exceeds three degrees.
- Include and compute all other loads that are impacting the shoring system such as a typical Railroad service vehicle (HS-20 truck).