§ 4-39. Structural requirements for major structures.

(a)

Foundations. All major structures shall be anchored to their foundations in such a manner as to prevent flotation, collapse, or lateral displacement.

Foundation design and construction shall consider all anticipated loads resulting from design storm conditions, including wave, hydrodynamic, hydrostatic, and wind loads acting simultaneously with dead loads. Erosion computations for foundation design shall account for all vertical and lateral erosion and scour-producing forces, including localized scour due to the presence of structural components.

(1)

Pile foundations shall be required for buildings located in Federal Emergency Management Agency Flood Insurance Rate Map "V" "velocity" zones or where impacted by wave action.

a.

Pile dimensions, spacing and embedment shall be designed consistent with the requirements of the site, taking into account all vertical, lateral, erosion and scour-producing forces.

b.

Piles shall be driven to a penetration which achieves adequate bearing capacity taking into consideration the anticipated loss of soil above the design grade.

c.

In addition to the normal foundation analysis, the pile foundation analysis shall consider piles in column action, where appropriate, from the bottom of the support structure to the design grade.

d.

Consideration shall also be given to the degree of exposure to wave attach and the resulting impact loads on lateral or diagonal bracing between piles.

(2)

Monolithic foundations may be permitted in Federal Emergency Management Agency Flood Insurance Rate Map "A" or "B" zones or in locations not impacted by wave action.

a.

Monolithic foundations may be used if soil conditions permit and if located at an elevation which minimizes their effect on the beach and adjacent properties. Due consideration shall be given to their vulnerability to erosion under design storm conditions.

b.

In the event that a monolithic foundation is used, the maximum elevation of the top of the slab is to be below the design scour depth (see Chapter 5.28, Shore Protection Manual, U.S. Army Corps of Engineers, 4th edition, 1984) unless positive methods are provided to prevent scour.

c.

Other types of spread footings such as running footers or pads may be permitted when positive methods are provided to prevent scour.

(b)

Understructures. No substantial walls or partitions shall be constructed below the level of the first finished floor. This does not preclude the construction of:

(1)

Stairways;

(2)

Shearwalls essentially perpendicular to breaking waves;

(3)

Shearwalls essentially parallel to breaking waves which do not exceed a maximum of twenty (20) percent of the building length;

(4)

Wind or sand screens constructed of fabric or wire mesh;

(5)

Light open lattice partitions with individual wooden lattice strips no greater than three-fourths (¾) inch thick or three (3) feet wide;

(6)

Elevator shafts;

(7)

Breakaway or frangible walls; or

(8)

Substantial walls constructed above the wave action and storm surge expected under design storm conditions.

(c)

Building and floor elevations. The minimum elevation for the underside of the building support structure (excluding foundation) shall be above the elevation of the design breaking wave crests or wave uprush superimposed on the storm surge with dynamic wave set-up expected under the design storm conditions. The elevation of the storm surge with dynamic wave setup shall be either the elevation established by the Florida Department of Natural Resources Coastal Construction Control Line Study or the base flood elevation for the specific area established by the Federal Emergency Management Agency as determined by the design engineer.

(d)

Erosion and design grade. The elevation of the soil surface to be used in the design of foundations, calculation of pile reactions and bearing capacities shall not be greater than that which would result from the erosion reasonably anticipated as a result of design storm conditions. Calculation of the design grade shall take into account localized scour due to the presence of structural components. Erosion computations for foundation design shall consider all vertical and lateral erosion and scour-producing forces.

(e)

Wave force design.

(1)

Calculations for wave forces resulting from design storm conditions on building foundations and superstructures may be based upon the minimum criteria and methods prescribed in the Naval Facilities Engineering Command Design Manual, NACFAC DM-26, U.S. Department of Navy; Shore Protection Manual, U.S. Department of the Army Corps of Engineers; U.S. Department of the Army Coastal Engineering Research Center Technical Papers and Reports; the Technical and Design Memoranda of the Division of Beaches and Shores, Florida Department of Natural Resources; or other professionally recognized methodologies which produce equivalent design criteria.

(2)

Breaking, broken, and nonbreaking waves shall be considered as applicable. Design wave loading analysis shall consider vertical uplift pressures and all lateral pressures to include impact as well as dynamic loading and the harmonic intensification resulting from repetition waves.

(f)

Hydrostatic loads. Calculations for hydrostatic loads shall consider the maximum water pressure resulting from a fully peaked, breaking wave superimposed upon the design storm surge with dynamic wave set-up. Both free and hydrostatic loads shall be considered. Hydrostatic loads which are confined shall be determined using the maximum elevation to which the confined water would freely rise if unconfined. Vertical hydrostatic loads shall be considered both vertically downward and upward on horizontal or inclined surfaces of major structures (e.g. floors, slabs, roofs, walls). Lateral hydrostatic loads shall be considered as forces acting horizontally above and below grade on vertical or inclined surfaces. Hydrostatic loads on irregular or curved geometric surfaces shall be determined by considering the separate vertical and horizontal components acting simultaneously under the distribution of the hydrostatic pressures.

(g)

Hydrodynamic loads. Hydrodynamic loads shall consider the maximum water pressures resulting from the motion of the water mass associated with the design storm. Full intensity loading shall be applied on all structural surfaces above the design grade which would affect the flow velocities.

(h)

General design conditions.

(1)

Foundations for all major structures shall be designed for the horizontal and vertical pressures generated by wave forces between the elevation of the design breaking wave crests or wave uprush superimposed upon the storm surge and the stable soil elevations of the site.

(2)

All major structures, except mobile homes, shall at a minimum be designed and constructed in accordance with Chapter 16 of the current Florida Building Code for Coastal Construction.

(3)

Appropriate shape factors shall be applied for resistance against overturning and uplift as required elsewhere in this code. Internal pressures of internal walls, ceilings and floors resulting from damaged windows or doors shall also be considered in the design unless the specified windows and doors have been tested by an approved testing agency and have been shown to be capable of withstanding the design pressures required therein.

(4)

Mobile homes shall conform to the Federal Mobile Home Construction and Safety Standards of the Uniform Standards Code ANSI Book A-119, pursuant to Section 320.823, Florida Statutes, in addition to the other requirements contained in this article.

(Ord. No. 124-86-2, § 1(108.2), 4-7-86; Ord. No. 125-86-3, § 3, 12-1-86; Ord. No. 207-118-73, § 8, 1-7-02)