The Design of Jetties

MUCH ado is made nowadays about the application of scientific method in the analyses of physical problems. It therefore appears incongruous that published matter in text-books, technical periodicals, and institutional papers, do not show that the basic principles of jetty design have been so treated. This is all the more surprising as jetty design has improved considerably in the last 25 years. It may be that this is due to a more complete investigation of the stresses in individual members consequent on the wide use of reinforced concrete, nevertheless many of the preliminary assumptions are not convincing, and are related to the “old rules of thumb.” It can be conceded that in dealing with hydraulic structures long experience is worth much more
than theory and if some part of that experience can be quantitatively established then a definite progressive treatment may be initiated. Of late years many researches have been carried out regarding the behaviour of materials, soils, water, etc., under stress, that a continued employment of unreasoned assumptions is indefensible, in fact the progressive nature of scientific knowledge makes it incumbent upon engineers to throw away old fashioned note-books of “thumb” data and to design structures to meet the ever-changing conditions of the present-day requirements, basing them on the latest public knowledge. Much of the science of engineering design is economic, and to that end, structures should be adequate for their function and not monuments for posterity. Because a jetty built some decades ago still remains in use is not necessarily a credit to the professional skill of the builder, and still less is it an adequate reason why its design and proportions should be duplicated or copied to-day. There may be points about it of interest and engineering skill but surely most of the good points of our predecessors have already been assimilated into current practice.

R.R. Minikin