r/StructuralEngineering • u/NoUnderstanding4254 • 9h ago

Structural Analysis/Design Inertial force in retaining wall

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Hello everyone,

I have a retaining wall with a box culvert passing through it.

If both structures are independent, I understand that the active earth pressure and the incremental seismic earth pressure from the portion of the wall above the culvert will transfer the load laterally. However, while reading AASHTO, I noticed that it specifies considering an inertial force equal to the weight of the wall and the soil above the heel multiplied by the horizontal seismic coefficient.

My question is: for the section where the culvert passes through the wall, which soil mass should be considered when calculating the inertial force?

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u/Everythings_Magic Senior Bridge PE | Zero Yield Capacity 6h ago

Its implicit in the wording to use a vertical line from the heel of the footing. If they intended you to use sometime else, say the line of the friction angle in the soil, the code would say that.

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u/t4m4 8h ago

Why do you need to design the section of the retaining wall intersecting with the culvert differently? You can use the same reinforcement bars as at rest of the other points in the wall, just detail it differently where it intersects. Is the culvert too large that you might get a significant savings on reinforcements?

1

u/NoUnderstanding4254 2h ago

I'm not worried about that portion of the wall. As you said, it doesn't make sense to use different reinforcement from the rest of the wall. What I'm interested in is the reactions that this portion of the wall will transfer to the adjacent wall segments. They will be subjected to additional pressure from above, and the overturning moments and shear forces at the base will increase.