Module 6 : Design of Retaining Structures
Lecture 28 : Anchored sheet pile walls [ Section 28.5 : Moment reduction for anchored wall ]
   
  Moment reduction for anchored wall
 

Rowe (1952) demonstrated that the Free Earth method overestimates the maximum bending moment in anchored walls with horizontal tie rods. The sheet piles are relatively flexible and these deflect considerably. Their flexibility causes a redistribution of the lateral earth pressure. The net effect is that the maximum bending moment is considerably reduced below the value obtained for the free earth supports. It is used to take into consideration the flexibility of the pile and its effect on relieving the actual bending moment the wall experiences. The reduced bending moment for design ( ) is given by

=

where

= maximum bending moment predicted by the Free Earth method,

= reduction factor depending on wall geometry, wall flexibility, and foundation soil characteristics.

Moment reduction factor for granular foundation soils. When the soil below the dredge line is granular, the magnitude of the reduction factor is a function of a flexibility number given by
 
 

where, H = total length of the sheet piling (ft),

E = modulus of elasticity of the pile material (psi),

I = moment of inertia (in 4 ) per foot of wall.

Curves of are given in fig. for "loose" and "dense" foundation material and several system geometries.

 
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