What are the Lateral Loads Considered in Raft Foundation Design?

In this post we will highlight ACI committee 336 recommendation for considering loads for combined or raft foundation - for these post lateral loads. At first we will know what vertical effects of horizontal loads are. These are:

a. Vertical effects from lateral loads F_vh

b. Vertical effects from wind loads, W

c. Vertical effects from earthquake loads that are found by simulating earthquake, E

Of them vertical effects from lateral load F_vh can consists of:

1. Water pressure

2. Earth pressure

3. Load like surcharge pressure, fill pressure

4. Differential settlement, differential creep, differential temperature and shrinkage effects of concrete.

Now we will know about overturning moment. They are of following form:

a. The moment that try to overturn the foundation due to simulated earthquake forces, ME.

b. The moment that try to overturn the foundation due to vertical effect lateral loads(Fvh) and termed as MF

c. The moment that try to overturn the foundation due to explosion, wind or similar forms of lateral loads, termed as MW.

d. The moment that try to overturn the foundation due to dead load of foundation with superstructure, D0. These loads may include buoyancy effects, if any, that are resulted from submerged portion or that portion supposed to be have future submergence.

e. The moment that try to overturn the foundation due to loads from unsymmetrical fill M₀

f. The moment that try to overturn the foundation due to resultant of vertical load as a whole and termed as R_Vmin