The bearing load and cross bracing requirements for most fixed open pier systems will 

 normally result in adequate structural stability to resist design windloading; but, if there is 

 any doubt, the system should be analyzed. However, floating systems must always be 

 analyzed to determine the number of guide piles required, or with a cable-moored system, 

 to determine the adequacy of the lines and anchors. Any covered system must be analyzed 

 for windloading against the building itself and not the berthed boats. This results in 

 exceptionally high lateral loading in most areas, often requiring dolphins or subsurface 

 cables and anchors rather than an array of single guide piles. 



Guide piles are usually the least costly anchorage system. A typical 14-inch diameter 

 prestressed concrete pile with anaylsis for design moment calculation is shown in Figure 83. 

 A sample analysis of the lateral load resistance of the same pile in a typical bottom 

 formation with the load applied at a given distance above the bottom is shown in Figure 84. 

 Where guide piles of other types and materials are used, the allowable bending moment must 

 be computed in accordance with standard structural design procedures. The pile length and 

 resistance to lateral loading may be computed by the method shown for the typical case. 

 This requires an analysis of soil samples taken from the basin substructure to determine the 

 slide angle, the dry density Wj, and the saturated moisture content V. If strata of 

 different properties are penetrated by the piles, a more complicated calculation wiU be 

 required and the services of a soil-mechanics speciahst should be obtained. 



The spacing of guide piles in a floating pier system is largely a matter of judgment. It 

 must be assumed that a floating main walk with 40 or 50 feet between adjacent pUes is 

 fairly rigid in a horizontal plane and will take bending loads due to wind stresses, exhibiting 

 almost no flexure. Most guide piles wiU flex in cantilever bending from the bottom allowing 

 windloads to be distributed evenly throughout the pile system, provided the guides do not 

 have more than 3 or 4 inches of play, and the center of resistance is fairly concentric with 

 the center of loading. Each pile guide should be designed to resist the design load of the pile 

 in any direction and to transmit load safety to the structural members of the main walk, 

 either directly, or through fingers. Several commonly used types of pile guides are shown in 

 Figure 85. Guides that do not completely surround the pile may fail to transmit the load in 

 certain directions and thus throw inordinately high loads on other piles. 



In marina sites subjected to frequent or prevailing moderate to strong winds or currents, 

 certain guides of a guide-pile system take all the lateral load most of the time and therefore 

 wear out quickly. Some guides have lateral adjustment devices that permit adjustment of the 

 driven pile and will distribute the load equally to all piles in the system. This is seldom the 

 case, however, and it is important that the harder working guides be made easily replaceable 

 or strongly wear-resistant. This may be done by fitting the guide with easily replaceable 

 hardwood blocks or with heavy-duty rollers (Fig. 86). 



187 



