Elastic stability of pile-supported wharves and piers

• Stability of idealized pile-supported piers/wharves can be described by three parameters.
• Piles in marginal wharves are essentially braced even for soft soils.
• Piles in finger piers are nearly braced even for soft soils.

Elastic stability equations for idealized pile-supported waterfront structures were implemented in a parametric study that accounts for coupling between lateral stiffness of the supporting soil, pile flexural stiffness, and factored gravity loads. Results are summarized as design aids that could enable engineers to obtain estimates of the second-order lateral stiffness and lowest buckling axial load of each pile by using simple arithmetic calculations. Through these, an expedite tool is provided to classify each pile of a two-dimensional pier/wharf frame as fully braced or partially braced and further allow estimating the effective length factor, K, once an equivalent column length is established. Three application examples are presented to demonstrate the versatility of the method and to compare the results with those from commercially-available finite element software. For the case of a marginal wharf, the buckling axial load of the slender waterside piles was found to be smaller than that of the short landside piles; however the difference between the two became less significant when the soil was soft. It was also determined that for the level of factored axial loads found in practice, plumb piles supporting finger piers and wharves could commonly be considered as braced even if the supporting soil is relatively soft.