Obround, elongated hexagonal, and elongated octagonal piers have long been used at river crossings for hydraulic purposes. Now such shapes are increasingly being chosen over circular or rectangular columns simply for the aesthetic effect. To form these pier shafts, contractors must choose from a wide variety of systems after carefully evaluating such criteria as bridge design, jobsite conditions, existing supply and expected reuse of formwork, and availability of lifting equipment. Among the most common choices are job-built wood systems, manufactured steel systems, and combinations of the two.
Many concrete contractors find job-built wood forms economical and easy to use, especially when very few bridge piers need to be built, when manufactured modular formwork is impractical, or where the use of heavy lifting equipment is unfeasible. Contractors can usually expect to reuse job-built forms at least three or four times, while steel forming systems, if properly cleaned and oiled, can be reused indefinitely. But the high initial purchase price of steel forms is impractical for contractors who don't expect the job to last at least 10 to 12 months.
Job-built forms give contractors the flexibility to tailor the forms for a specific job and allow them to make panels of a size that can be handled by available lifting equipment. When working with manufactured modular forms, a crane is required for both erecting and stripping them. This possible disadvantage is offset by the relatively speedy assembly of tremendous square footage of steel formwork and the ease of stripping it. The single biggest obstacle to removing the formwork is the capacity of the crane being used.