FLOOD03449

• County: Statewide
• Community: State of Colorado
• Stream Name: All
• Basin: Statewide
• Title: Colorado Flood Proofing Manual
• Date: 10/1/1983
• Prepared For: State of Colorado
• Prepared By: CWCB
• Floodplain - Doc Type: Educational/Technical/Reference Information

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11.3 Design Procedure

The design procedure presented in this chapter follows a logical sequence of steps resulting
in the final selection of a wall and slab design. The various steps involved are:

1. Assumptions

Step one involves making assumptions pertaining to water surface elevation in relation
to the basement floor, surcharge condition (i.e., depth of water above soil), wall and
slab support conditions and design control parameter(s).

2. Computation of loadings

Step two is simply applying the methodology presented in Chapter VI to compute the
lateral and uplift (bouyant) forces acting on the basement.

3. Wall design

The third step is design of the basement wall. The wall design is determined by the
bending moment created by the soil/water loading. The soil/water loading is determined
by the calculation of Yeq' Thus, the resulting wall design or bending moment equation
is set up in terms of Yeq allowable.

4. Compare allowable Yeq

Step four is comparison of the actual computed Yeq with Yeq allowable. Yeq allow-
able is equal to the working load Yw dett;rmined from the design curves.

5. Slab design

Based on a completed wall design the depth of water above the basement floor is
known. From the known water depth, the slab design is selected.

6. Typical section illustration

As a final step in the design procedure typical section detail illustrations are given in
Figures 11.20 through 11.23.

11.4 Assumptions

11.4.1 Water Surface Elevation

The first assumption to make is the water surface elevation in relation to the basement
floor. When basements are being considered within the flood plain, the BFE must be sited
one foot below the first floor. Thus, in relation to an eight-foot basement the maximum
depth of water above the basement floor will be seven feet. This condition is illustrated in
Figure 11.1.

11.4.2 Surcharge Condition

Surcharge condition refers to the depth of water above ground. As discussed in Section
6.2.3, three surcharge conditions were identified for determination of the equivalent fluid
weight. The surcharge condition is determined by determining what percent of the total load-
ing depth is the surcharge depth. In Figure 6.3, a is the height of soil loading above the
basement floor, h is the height of water above the ground (surcharge) and H is the total
loading height or a plus h. The percent of the total loading height (H) made up by the sur-
charge (h) is simply:

11 x 1 00 ~ percent of surcharge