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POL Government Elected Officials Auditor Griffin-Valade Charter, Code & Policies City Code & Charter Online Code & Charter Title 28 Floating Structu Chapter 28.06  New Construction
28.06.040 Engineered Construction.

 

(Amended by Ordinance No. 181437, effective December 21, 2007.)

 

A.  General.  The minimum structural design of floating structures and moorages, except those structures conforming to the conventional construction methods and materials as listed above, shall be in conformity with all applicable sections of the State Structural Specialty Code and the requirements of this section.  The piling, mooring connectors, the gangway, and floatation system for all floating structures shall have an engineer of record who is registered in Oregon. 

The Engineer of Record shall be responsible for establishing the design criteria and completing the design of the complete project.  The Engineer of Record shall prepare and certify complete construction drawings and calculations for structural strength and floatation.  The design criteria shall be substantiated by the Engineer of Record and noted on the first sheet of the construction drawings.

If an engineer or architect other than the Engineer of Record has been engaged to design an element of the project such as but not limited to piles or gangways, the Engineer of Record must:

1.  Verify that the other engineer or architect has provided drawings and calculations certified by an Oregon engineer or architect.

 

2.  Verify that the other engineer or architect has used design criteria that have been established by the Engineer of Record.

 

3.   Verify the compatibility of the element's design with the design of the complete project.

 

4.  Verify that the designs of structural connections between the elements of the project designed by other engineers and those elements designed by the Engineer of Record have been accomplished by an engineer or architect registered in Oregon.

 

5.  Place review approval stamp on all drawings and calculations prepared by the other engineers showing that 1. through 4. have been accomplished.

B.  Loading.  All floating structures, piling, mooring devices and gangways shall be designed and constructed to sustain, within the stress limitations specified in the Structural Specialty Code, all applicable loads specified in the State Structural Specialty Code and this Title.

1.  Current loads shall be calculated on the basis of a minimum current speed of 1.5 knots unless the designer can provide documentation that the maximum current speed that can be anticipated at the location of the structure is less than 1.5 knots.  If anticipated minimum current speeds of greater than 1.5 knots can be expected at the location of the structure the higher current speed shall be used for calculation of current loads.

 

2.   Wave and wake loads shall be calculated on the basis of the maximum possible wave and/or wake that can be expected at the location of the structure.

 

3.  Impact loads from boats, debris and other objects shall be considered with a minimum velocity as determined using a minimum current speed of 1.5 knots.  If anticipated current speeds of greater than 1.5 knots can be expected at the location of the structure the higher current speed shall be used for calculation of impact loads.

 

4.  Earthquake loads shall be considered based on values specified in the State Structural Specialty Code.

 

5.  Gangways not more than 6 feet wide shall be designed to sustain a live load of 50 PSF unless they serve structures which contain an occupancy where more than 50 people may occupy a room at one time such as some dining establishments or meeting rooms.  Gangways more than 6 feet wide and all those serving occupancies with a calculated occupant load of 50 or more shall be designed to sustain a live load of 100 PSF.

EXCEPTION: Gangways not more than 6 feet wide serving public recreational boat launching and transient tie-up facilities may be designed to sustain a live load of 40 PSF.

 

6.  All floating structures, piling, mooring connectors, gangways and ramps shall be designed and constructed to resist lateral forces produced by the reasonable combination of expected wind, current, wave, wake, earthquake and impact loads at the location.

C.  Mooring connectors.

1.  Every floating structure shall be moored with connectors having the capacity to hold the structure in place under reasonably expected conditions.  For engineered structures the number and locations for mooring connectors shall be as specified by the design engineer.

 

2.  Whatever structure the mooring connectors are attached to shall be designed to withstand the loads from the mooring connectors.  The engineer of record's design criteria for the project shall include the maximum dimensions of the floating structure(s) as these determine the loads on the mooring connectors and their supports.

D.  Piling. 

1.  Floating structures shall be directly or indirectly attached to piling which is adequate to resist lateral forces produced by any normally expected combination of wind, current, wave, wake, earthquake and impact.  The minimum height of the top of the piling shall be a minimum of two feet above the point of connection of the floating structure to the piling when the water rises to the l00 year flood elevation as shown on the Federal Insurance Rate Maps published by the Federal Emergency Management Agency.  Batter piles shall not interfere with the ability of a floating structure to rise to an elevation at least two (2) feet above the level of the 100 year flood elevation that is used to determine the minimum height of piling.

E.   Floatation. 

1.  Floating structures shall be constructed and maintained to provide a floatation system that complies with the requirements of this chapter.  The floatation devices shall be structurally sound and securely attached to the framing for the superstructure, except that foam floatation blocks may be held in place by friction only. 

The floatation systems shall provide support adequate to provide a level and safe walking surface under all reasonable load conditions.  The following minimum standards apply to all floating structures.

 

2.   Clearance Above Water.  The minimum clearance above water as measured from the water line to the top of the lowest point on the floor or deck under usual dead load conditions, shall not be less than one foot zero inches  (1'-0") from water line to the top of the walking surface for walkways and walks, and not less than one foot eight inches (1'-8") from the water line to the finished floor level of the lowest occupied floor for all other floating structures.

EXCEPTION:  Boathouses and the portion of combo-structures that house a personal watercraft need only have adequate floatation to maintain clearance above water under all applicable conditions. 

 

3.  Live Loads.  In addition to dead loads, the floatation system shall be adequate to support the maximum condition of the following minimum live loads.  Higher loads may be more appropriate if the design engineer determines the need for a higher load based on the intended use conditions.

a.  25 PSF applied to the gross area; or,

 

b.  A concentrated load of 600 lbs.; or,

 

c.  25 PSF applied to the gross, main floor area plus 10 PSF on each upper floor or loft; or,

 

d.   For floating structures that are occupied as other than a one or two family residence, the live load required by the State Structural Specialty Code for the specific occupancy shall apply.

 

e.  Pedestrian walkways or ramps serving an occupant load of 10 or more; 40 PSF; all others 25 PSF.

 

f.  Pedestrian walkways or structures serving boat launching or transient tie-up facilities only; 25 PSF.

 

g.  At locations where live loads are transmitted from gangways to floating structures, the live load may be reduced fifty percent (50%) on the gangway for purposes of calculating the reaction only.  Additional floatation may have to be provided to compensate for this reaction on the floating system to maintain the prescribed clearance above water.

4. Stability with short term, off-center loading or wind loading.  The floating structure when subjected to either short-term off-center loading or wind loading shall not exceed the following limitations:

a.  The maximum angle of list shall not exceed 4.0 degrees, or the clearance above water when measured from the water line to the top of the first floor or deck shall not be less than 1/3 of the normal clearance above water, whichever is the more restrictive.

 

b.  The ratio of resisting moment (Mr) to applied moment (Ma) shall be equal or greater than unity:

Mr > 1      

Ma        

 

The resisting moment due to buoyancy (Mr) shall be computed about a longitudinal axis passing through the center of gravity at a list angle of not more than 4.0 degrees.

 

c.   The minimum off-center loading shall be considered as applicable to the completed structure and shall be considered in addition to all dead loads.  It shall consist of a minimum live load of 100 pounds per lineal foot of floor length at the first floor and 50 pounds per lineal foot of floor length at each additional floor or loft.  If the width of the floor or loft exceeds 20 feet then the load shall consist of 5 pounds times the width of the floor per lineal foot of floor length at the first floor and 2.5 pounds times the width of the floor per lineal foot of floor length at each additional floor or loft.  These uniform live loads are to be applied halfway between the center of gravity and the outside edges of the floors.  The overturning moments resulting from the off-center loadings (Ma) shall be computed about both sides of the center axis of gravity.

 

d.  Other appropriate eccentric or off-center loading due to wind, snow, live loads or combinations of these or other similar loads as may be determined to apply by the engineer of record, shall also be considered.