42 



and 39 are in first class condition and indicate the possibilities of this 

 type of support when properly designed and when construction condi- 

 tions are favorable. 



Reinforced Concrete Piles 



The square reinforced concrete pile with chamfered corners des- 

 cribed in detail in the 1921 report has become a standardized construc- 

 tion type for the San Francisco Bay region (Plate 8, Fig. 2; Plate 9, 

 Fig. 1). Of the numerous installations made during the past ten years, 

 no defects have been noted in the portion of the piling below high 

 water. In the older structures, however, cracks due to the rusting of 

 embedded steel are beginning to appear between the high water line 

 and the deck. In this portion of the pile they are easily observed and 

 readily repaired as contrasted to deterioration below the low water 

 line which cannot be observed. The real concern of engineers experi- 

 enced with this type of construction is not so much with the pile as with 

 the concrete decks which usually accompany concrete pile construc- 

 tion. The Board of State Harbor Commissioners is keeping a careful 

 record of such deterioration, a portion of which relating to piles is re- 

 corded as a service record. As a result of experiments and observa- 

 tions, the engineers of the Board are confident that in all future 

 construction, deterioration due to rusting of embedded steel can be 

 retarded if not prevented by several simple expedients, such as the 

 use of galvanized steel, and periodic coating of the concrete surfaces 

 with asphalt, paraffin or other waterproofing coatings. 



With reference to both reinforced concrete cylinder and reinforced 

 concrete pile construction, many engineers are of the opinion that the 

 increased cost of this construction is not justified by the degree of per- 

 manence so far exhibited. The principal factor which has influenced 

 the early development of this construction in this locality has been the 

 demand for fireproofing in waterfront structures where cargoes are con- 

 centrated aggregating in value many times the cost of the structures. 

 As frequently happens, the pioneer has paid heavily for the experience 

 of blazing the way. All the early structures were built before the 

 modern scientific studies of concrete construction were disseminated, 

 at a time when the danger of excessive water and sand contents were 

 not merely unknown but were even thought beneficial and when con- 

 crete of any thickness was considered an efficient protection from the 

 corrosion of steel. 



Notwithstanding defects which will admittedly lessen the durabil- 

 ity of these structures, their value has been enhanced by the progres- 

 sive rise in construction costs, a tendency which is seldom taken into 

 account by advocates of more temporary construction. In general it 

 may be stated that high class reinforced concrete cylinder and rein- 

 forced concrete pile construction on San Francisco Bay gives promise 



