1. 15.017
3/24/15
CDR
Unrestrained Conrete Retaining Wall (RETAINED HEIGHT = 1'-6") (cont)
Determine Resisting Moments (For a 1 ft thick strip of wall)
To resist the overturning moment, resisting moments caused by the dead loads in the system are
considered. These dead loads are calculated as un-reduced loads which are then compared with
the allowable factor of safety of 1.5 Per 2013 CBC 1807.2.3.
Element Weight Resisting Moment
Wall ≔WW =⋅⋅⋅γc 1 ⎛⎝ +Hr Le⎞⎠ Tw 0.25 ≔MRW =⋅WW ⎛⎝Lt⎞⎠ 0.333 ⋅
Footing ≔WF =⋅⋅⋅γc 1 ⎛⎝ +Lh Lt⎞⎠ Tf 0.313 ≔MRF =⋅WF ⎛⎝ ⋅0.5 ⎛⎝ +Lt Lh⎞⎠⎞⎠ 0.39 ⋅
Soil Abv Heal ≔WH =⋅⋅γs 1 ⎛⎝ +Hr Le⎞⎠ ⎛⎝ −Lh ⋅.5 Tw⎞⎠ 0.23 ≔MRH =⋅WH ⎛⎝ +Lt ⋅Lh .5⎞⎠ 0 ⋅
Soil Abv Toe ≔WT =⋅⋅γs 1 ⎛⎝Le⎞⎠ ⎛⎝ −Lt ⋅.5 Tw⎞⎠ 0.11 ≔εMR =++MRW MRF MRH 1 ⋅
Total ≔εW =+++WW WF WH WT 0.902
=――
εMR
M0
2.513 Factor of Safety > 1.5 OK∴
Check Maximum Soil Pressure
≔Ltotal =+Lh Lt 2.5 Total Footing Length
1) Determine the location at which
the combined dead loads act
≔L =――
εMR
εW
1.29
2) Determine where resultant soil force acts:
≔e =――
M0
εW
0.513
≔a =−L e 0.777
=――
Ltotal
3
0.833 Free Body Diagram at Retaining Wall
3) The Soil Resultant Force acts in the
outer 1/3 of the foundation, so
≔Pmax =―――
⋅2 εW
⋅⋅3 a 1
774.032 Maximum Soil Pressure
< 1.5 ksf OK∴
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