of cement mortar about 2" tliick over the surface of the pile by means 

 of pneumatic equipment. This type of protection for timber piles has 

 been used irith success on several large navy piers. 



Figure it shovfs a concrete pile designed for longer life in the tide zone. 

 In t'-^e illustration^ it will be noted that a two inch minimum thickness 

 of concrete cover is provided over the steel for the lower portion of the 

 pile. Above this level, tlie longitudinal steel reinforcement in the pile 

 is bent so that the concrete cover is increased to a minimum thickness of 

 3 inches. Since square corners are more vulnerable to deterioration by 

 both chemical and physical processes, the corners are rounded to a mini- 

 mum radius of 2-| inches. 



Fi,gure $ illustrates a conventional concrete pier. Unless the deck is 

 located virell above high v.^ater, the lower surfaces of beams and girders 

 will be subject to the deteriorating effects of saltwater spray. The 

 many corners involved in tlus design tend to promote attack on the rein- 

 forcing steel. 



Figure 6 shows an ideal concrete pier design. The circular cylinders 

 have optimum shape for roslsting attack hy saltwater and for minimum force 

 from wave action. If the cylindrical shells are cast xvith the aid of smooth 

 metal form.s and adequate cover is maintained over the reinforcement, a long 

 life should result. The number and area of vertical supports is held to 

 a minimum. The flat slab construction has no deep transverse girders nor 

 longitudinal beams exposed to salt water spray. Untreated timber piles 

 may be safely used as supports beneath the cylinder bells. 



The conventional design of a steel pier is shown in Figure 7a. Lateral 

 stability is provided by batter piles in combination with a system of 

 cross bracing. Rapid deterioration of this bracing will occur even though 

 the usual protective coatings are applied. By vray of contrast, Figure 7b 

 shows a steel pier vdthout batter oiles or bracing. Lateral stability is 

 obtained by ri^id-frcime action. The tiirber-concrete composite deck gives 

 wide distribution of local lateral loads to several bents so that lateral 

 deflections are reduced. The vertical piles have concrete jacket protec- 

 tion in the tide zone for maximum longevity, vihere additional stability 

 is required, A-frames can be ad'jed beneath the center of the pier, 



A practical method for installing jackets on either timber or steel piles 

 is shovm in Fig-ore 8. It is equally a}.plicable to existing Diles or to 

 net; construction. The two halves of the form are separated by rubber gas- 

 kets which are compressed as the form is locked together, thus providing 

 for self- stripping when the pressure is released. ..'ith the form secured 

 in position around the pile at the desired elevation, coarse aggregate is 

 deposited to fill the form after which a special grout virith admixture is 

 introduced at the bottom of the form. As the grout rises to the top, the 

 vrater in the form escapes through a series of vent holes and a complete 

 filling of the voids with good grout is achieved. 



G - 8 



