Bollards; Not So Simple

Marine Bollards can be deceiving, as they may initially appear as simple and easily overlooked metal blocks on a dock. However, upon closer examination, bollards present unique design considerations and challenges.

Conventional structural codes and standards are typically based on predefined structural members used in situations where their length often significantly exceeds their section depth and width.  However, bollards deviate from this norm.  Most marine bollards are custom steel or iron casting, with short and compact bodies, highly concentrated loads, and varying crosssections.  Additionally, varying stress concentration, non-uniform bolt patterns, and an extensive range of vertical and horizontal mooring line pull angles further complicate the hand calculation process.

At Simplicit, we strive to validate our engineering calculations and assumptions using various design approaches.  For bollards, this usually entails a combination of hand calculations and a series of finite element analyses. In our experience, hand calculations are helpful but almost always produce significantly higher factors of safety than those shown using Linear Finite Element Analysis. In short, even if you include an exhaustive amount of stress concentration factors in your hand calculations, bollards are often just so non-typical and non-standard that the hand calculation doesn't catch everything. 

When evaluating Marine Bollards or any other non-regular, highly loaded casting, Simplicit advises against relying solely on hand calculations.  Instead, it is recommended to consider more comprehensive computational methods.

It is important to note that the subject discussed here is significantly more complex than presented.  If you would like to delve deeper, please don't hesitate to contact Simplicit, and we would be delighted to assist you.