The fixed-pier approaches and hinged gangways leading from the basin perimeter to a 

 floating dockage are designed to carry more live loading than the specified flotation loading. 

 This occurs from a concentration of loading in an area of the fixed part of the system or on 

 the gangways at one time without the knowledge of the persons causing the overloading. 

 Once on the floating system, however, the same persons will become aware of any 

 overloading because of the canting of a deck surface or the partial submergence of a float. 

 Then they will instinctively move back or spread out to regain a safe load situation. For this 

 same reason the deck system and all interfloat stringers should also be designed for fixed 

 system loading; this is usually 40 to 50 pounds per square foot, but it may be specified 

 otherwise by the controUing agency. A common additional specification for deck loading is 

 that a concentrated load (e.g., 500 pounds) can be placed anywhere on the deck surface 

 without stressing the framing members beyond their design capacity and without tilting the 

 deck more than about 6° from the horizontal. 



h. Lateral Loading. The maximum lateral loading of a fixed or floating system is usually 

 produced by strong winds blowing against the structure and berthed craft. Such loading 

 usually exceeds normal docking impact loads or current drag. The design lateral load is 

 normally specified in terms of a given wind speed acting on the above water profile of the 

 system and craft. This loading in pounds per square foot for wind speeds up to 120 miles 

 per hour is shown in Figure 80. This is for steady -state winds neglecting gusts. The higher 

 loads of gust winds are seldom transmitted to a dock because of the inertia of the boats and 

 the flexibiUty of the tielines and piling. Design winds are often specified by the local 

 building and safety agency; if not, they should be determined by analysis of local wind 

 records. 



In analyzing the system for lateral loading it is customary to check two directions: 

 parallel and perpendicular to the main walk. If the anchorage or lateral bracing system is 

 adequate for these directions, it will normally be adequate for all other directions. Some 

 agencies simplify the calculations by specifying that the average profile height for boats in 

 open berths be 15 percent of the slip length. This assumption is conservative, and if not 

 specified, a lower design profile height can be obtained from Figure 81, which shows actual 

 average profiles for most craft in marinas. In calculating the parallel windload on a line of 

 boats, all shielded boats may be assumed to experience only 20 percent of the windloading 

 that is applied to the first (unshielded) boat. In calculating the perpendicular windloading 

 on a system, the total projected area on which the wind acts is obtained by multiplying the 

 average craft profile height by the sUp width and that product by the total number of shps; 

 then, add to the result the above water areas of the finger pier ends exposed to the wind. 

 Where sUps are provided on both sides of the main walk, the area calculation should include 

 the side that berths the set of boats with the largest average profile height. This value should 

 then be multiphed by 115 percent to account for the wind force on the sheltered or leeward 

 boat row. A sample calculation for lateral loading on a typical open pier system is given in 

 Figure 82. 



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