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Saturday, January 28, 2012

Formwork

Concrete formwork serves as a mold erected to produce concrete elements having a desired size and configuration. Two major categories of formwork are site made and prefabricated. It is usually removed after the concrete has cured to a satisfactory strength. In some cases, concrete forms may be left in place to become part of the permanent structure.

It has been established that for many concrete structures, the largest single component of the cost is the formwork. “Formwork costs can exceed 50% of the total cost of the concrete structure, and formwork cost savings should ideally begin with the architect and engineer” (Alexander, 2003).

To control this cost the designer of concrete formwork must choose appropriate materials and utilize them so that the goals of safety, economy, and quality are met. It should have sufficient strength and stability to safely carry all live and dead loads encountered before, during, and after the placing of the concrete. It should be sufficiently resistant to deformations such as sagging or bulging in order to produce concrete that satisfies requirements for straightness and flatness.

To produce concrete forms that meet all job requirements, the construction engineer must understand the characteristics, properties, and behaviors of the materials used and should be able to estimate the loads applied to the forms and be familiar with the advantages and shortcomings of various forming systems. Form economy is achieved by considering four important factors; cost of form materials, ease of form fabrication, efficient use of forms, planning for maximum reuse to lower per use cost.

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