Structures and structural members shall be designed to have design strengths at all sections at least equal to the required strengths calculated for the loads and forces in such combinations as stipulated in AREMA Chapter 8 Part 2 Article 2.2.4b, which represents various combinations of loads and forces to which a structure may be subjected. Each part of the structure shall be proportioned for the group loads that are applicable, and the maximum design required shall be used.
a. Calculated depth of embedment is the embedment depth required to maintain static equilibrium.
b. Minimum depth of embedment is the total depth of embedment required to provide static equilibrium plus additional embedment due to the minimum factor of safety.
1. Embedment depth factor of safety for well-defined loading conditions and thoroughly determined soil parameters is generally 1.3 for most temporary shoring systems. (See AREMA 18.104.22.168.c)
2. All anchored shoring systems require a minimum embedment depth of 1.5 times the calculated depth of embedment. Shallow penetration into strong soil layers is not acceptable. (See AREMA 22.214.171.124)
The allowable stresses based on AREMA requirements are as follows:
Structural Steel: 0.55Fy for Compression in extreme fiber. (AREMA Ch.15 Table 1-11)
Structural Steel: 0.35Fy for Shear. (AREMA Ch.15 Table 1-11)
Sheet Pile Sections: 2/3 of yield strength for steel. (AREMA 126.96.36.199)
Concrete: 1/3 of Compressive strength. (AREMA 188.8.131.52)
Anchor Rods: 1/2 of yield strength for steel. (AREMA 184.108.40.206)
AISC allowances for increasing allowable stress due to temporary loading conditions are not acceptable.
Gravity type temporary shoring systems must also be analyzed for overturning, sliding and global stability.
The contractor is responsible for providing an approved test method to verify the capacity of anchored or tieback systems. The manufacturers recommendations for testing must be satisfied. Systems which support the Railroad embankment will be considered high risk in determining the percentage of elements to be proof tested.\
Calculated deflections of temporary shoring system and top of rail elevation shall not exceed the criteria outlined in Table 1 Deflection Criteria.