Simi Valley Municipal Code Art. 7 Loading

All structures covered by this chapter shall be capable of resisting all loads required by the building code and the loads prescribed in this chapter without exceeding allowable stresses. "Water loads" are loads or pressures on surfaces of structures caused and induced by the presence of flood waters. They are hydrostatic, hydrodynamic or impact loads.

(§ 1 (Exh. A), Ord. No. 1268, eff. April 20, 2017)

(a) Hydrostatic loads are those caused by water above or below surface, free or confined, which is either stagnant or moves at low velocities less than five (5) feet per second.

The pressure at any point is equal to the unit weight of water (62.4 pounds per cubic foot) multiplied by the height of water above the point to which confined water would rise if free to do so.

Hydrostatic loads consist of vertical loads, lateral loads, and uplift.

(1) Vertical loads. These are loads acting vertically downward on horizontal or inclined surfaces of buildings or structures, such as roofs, decks or floors, and walls, caused by the weight of flood waters above them.

(2) Lateral loads. Lateral hydrostatic loads are those which act in a horizontal direction, against vertical or inclined surfaces, both above and below the ground surface and tend to cause lateral displacement overturning of the building, structure, or parts thereof.

(3) Uplift. Uplift loads are those which act in a vertically upward direction on the underside of horizontal or sloping surfaces of buildings or structures, such as basement slabs, footings, floors, decks, roofs and overhangs. Hydrostatic loads acting on inclined, rounded or irregular surfaces may be resolved into vertical or uplift loads and lateral loads based on the geometry of the surfaces and the distribution of hydrostatic pressures.

(§ 1 (Exh. A), Ord. No. 1268, eff. April 20, 2017)

Hydrodynamic loads, the purpose of these regulations, are those induced on structures the flow of flood water moving at moderate to high velocity around the structures or parts thereof, above ground level. Such loads may occur below the ground level when openings or conduits exist which allow free flow of flood waters. Hydrodynamic loads are basically of the lateral type and relate to direct impact loads by the moving mass of water, and to drag forces as the water flows around the obstruction.

Conversion to equivalent hydrostatic loads. For the purpose of these regulations, and for cases when water velocities do not exceed ten (10) feet per second, dynamic effects of the moving water may be converted into equivalent hydrostatic loads by increasing the depth of water by an amount dh, on the upstream side and above the ground level only, equal to:

[Figure]

"V" is the average velocity of the water in feet per second;

"g" is the acceleration of gravity, 32.2 feet per second per second; and

"a" is the coefficient of drag or shape factor. (The value of "a", unless otherwise evaluated, shall not be less than 1.25).

The equivalent surcharge depth "dh" shall be added to the depth measured between the design level and the regulatory flood and the resultant pressures applied to, and uniformly distributed across, the vertical projected area of the building or structure which is perpendicular to the flow. Surfaces parallel to the flow or surfaces facing downstream shall be considered subject to hydrostatic pressures for depths to the regulatory flood only.

(§ 1 (Exh. A), Ord. No. 1268, eff. April 20, 2017)

(a) Types. For the purposes of these regulations, impact loads are those which result from floating debris and floatable objects or masses carried by flood waters striking against structures or parts thereof. These loads are of two (2) basic types: normal and special.

(1) Normal impact loads. Normal impact loads are those which relate to isolated occurrences of logs or floatable objects of normally encountered sizes striking buildings or parts thereof.

(2) Special impact loads. Special impact loads are those which relate to large conglomerates of floatable objects, such as an accumulation of floating debris, either striking or resting against a building or parts thereof.

(b) Applicability. Impact loads shall be considered in the design of structures and parts thereof as stipulated below:

(1) Normal impact loads. A concentrated load acting horizontally at the regulatory flood level or at any point below it, equal to the impact force, produced by a 1,000 pound mass traveling at the velocity of the flood water and acting on a one square foot surface of the structure.

(i) Deceleration of the mass shall occur over 0.5 seconds;

(ii) This load shall be applied to the structure in such a manner that stresses are maximized.

(2) Special impact loads. Special impact loads shall be considered in the design of buildings, structures, or parts thereof. Unless a rational and detailed analysis is made and submitted for approval by the Director of Public Works, the intensity of load shall be taken as 100 pounds per foot acting horizontally over a one foot wide horizontal strip at the regulatory flood level or at any level below it. Where natural or artificial barriers exist which would effectively prevent these special impact loads from occurring, the loads may be ignored in the design.

(§ 1 (Exh. A), Ord. No. 1268, eff. April 20, 2017)

All new construction and substantial improvements that fully enclose areas below the lowest floor and that are subject to flooding shall be designed to automatically equalize hydrostatic flood forces on exterior walls by allowing for the entry and exit of floodwaters. Designs for meeting this requirement must either be certified by a registered professional engineer or architect to meet or exceed the following minimum criteria: A minimum of two (2) openings having a total net area of not less than one square inch for every square foot of enclosed area subject to flooding shall be provided. The bottom of all openings shall be no higher than one (1) foot above grade. Openings may be equipped with screens, louvers, valves, or other coverings or devices provided that they permit the automatic entry and exit of floodwaters. See Section 7-5.603(e)(5).

Pressure equalization shall be appropriate for unfinished or flood-resistant enclosures either unused or solely used for parking of vehicles, building access or storage in areas other than basements. All other structures shall be elevated or floodproofed pursuant to the terms of this chapter.

(§ 1 (Exh. A), Ord. No. 1268, eff. April 20, 2017)