ASCE 7 Flood Loads

[Gloeng]

Hi,

We have a concrete retaining (flood wall) that will be resisting flood loads. I have been using ASCE 7 and ASCE 24 in determining applied flood load.

I have a multi-part question

1. In ASCE 7-10 section 5.4.4.2 "Breaking Loads on Vertical Walls". It's unclear if I should use Pmax = Max. combined dynamic and static wave pressures and/or Ft = net breaking wave force. I used them together to find my forces on the wall. Is this over conservative? Should I only use one or the other? If I should only use one, how would you determine which one and why?

Pmax = Cp*Yw*ds + 1.2*Yw*ds [lb/ft^2]
Ft = 1.1*Cp*Yw*ds^2 + 2.4*Yw*ds^2 [lb/ft]

2. After finding my forces, i'm using load factored combinations. ACSE 7-10 uses 2*Fa for flood loads, ACI 318-14 uses 1.4*F. Since this is a concrete structure, I assumed ACI code would supercede ASCE. Would you use ACI or ASCE load combinations?

Many thanks.

 

[TXStructural]

Without answering your questions, two more things: 1) what kind of flooding? That is, if it is slow water, on a slow rise, you might have a significantly different loading scenario than for a surge load or fast moving water. and 2) design for saturated soils behind and under the wall. USACE has flood wall design requirements that address item 2.

As to question 2, I would use the ASCE 7 factoring for ASCE loads. The 2 Fa combination is for coastal hurricane and nor'easter floods. But I do not see a discrepancy.
ACI 318-11 says:
"9.2.6 — Flood and ice loads
If a structure is in a flood zone, or is subjected to
forces from atmospheric ice loads, the flood or ice
loads and the appropriate load combinations of ASCE/
SEI 7 shall be used."

ACI 318-14 says:
"5.3.9 If a structure is in a flood zone, the flood loads and
the appropriate load factors and combinations of ASCE/SEI
7 shall be used."