iron supporting members, accounts for the disuse of an othemrise satis- 

 factory/ material. 



Following the rapid expansion of the steel industry from 1890 through 1912, 

 many steel pipe piles and cylinders were used to support waterfront struc- 

 tures. In the latter half of this era, steel deck framing was also used 

 quite extensively. The comparatively rapid deterioration of these struc- 

 tures by corrosion and the resulting maintenance or replacement costs soon 

 curtained this type of construction. .ith the introduction of steel sheet 

 piling and the expanding use of steel "H" piles, much experimental work 

 was done in an effort to develop a more corrosion-resistant steel. Copper 

 bearing steel was introduced both in Europe and the United States as being 

 at least a partial ansv/er to the problem. Records, however, indicate 

 that in many locations little increase in resistance was apparent. Modern 

 steel sections can be used to advanta e in many locations where timber or 

 concrete sections camot be used. The useful life of a steel structure 

 can be materially extended by the adoption of a simplified design and the 

 initial protection afforded by coatings or envelopes located in the zones 

 of critic ,1 corrosion. Cathodic orotection, which is now under test, 

 promises to retard corrosion in the tide zone on both old and new steel- 

 work, Hovrever, it is not effective in or above the splash zone. 



In order to illustrate better the design techniques which will aid in 

 solving deterioration problems a series of illustrations are given of both 

 pier and bulkhead constniction. 



In general, all open ty~oe marine structures, ^Tith free tidal movement 

 beneath, are subject to more severe exposure tho,n those of the closed 

 t^pe which are exposed only along the exterior faces of the structure. 

 Figure 1 illustrates two timber pier designs. Figure la is the conven- 

 tional design wherein the lov;er level of bracing is located just above 

 mean low water and is subject to maximum exposure in the tide range. 

 Figure lb shov/s an improved r^esign. Here the bracing system is raised 

 above high virater level and the connections for the batter piles are made 

 at the level of the main transverse timber caps. The life of the structure 

 v:ill thus be increased by removal of the bracing and fittings from the 

 zone of critical exposure. 



A timber pier with composite deck is shov.Ti in Figure 2, In this example, 

 there is no lateral bracing. Stability is provided by a system of A-frames, 

 Tnese ara formed by embedding the outer vertical pile and the batter pile, 

 in each transverse bent, in a concrete beam. The composite deck protects 

 the timber caps from exposure to weather and the only members exposed in 

 the tide zone are the round piles. 



Some piers require the use of very long piles. In this case, timber piles 

 with concrete jackets can bo used to advantage as illustrated in Figure 3. 

 The concrete jackets perform a dual function: First in providing a large 

 increase in pile stiffness, thus eliminating the need for bracing, and 

 second as armor, providing protection from marine borers. The jackets are 

 applied on untreated piles prior to drivin^^ by depositing an encasement 



G - U 



