Classification of Formwork
Formwork can be classified according to a variety of categories, relating to the differences in sizes, the location of use, construction materials, nature of operation, or simply by the brand name of the products. However, the huge amount of tropical wood being consumed each year for formwork has resulted in criticism from environmentalists, as well as the continual escalation of timber prices. As a result, there has been a strong tendency to use other formwork materials or systems to replace timber. The different categories in which formwork can be classified are:
a) According to size.
b) According to location of use.
c) According to materials of construction.
d) According to nature of operation.
e) According to brand name of the product.
Classification according to size
Classification according to the size of formwork can be very straightforward. In practice, there are only two sizes for formwork; small-sized and large-sized. Any size which is designed for operation by workers manually is small-sized. Very often, the erection process is preferably handled by a single worker, with site work best done independently to avoid possible waiting times. Due to reasons of size and weight, the materials and construction of small-sized formwork are thus limited. At present, the most common systems are made of timber and aluminium, and are usually in the form of small panels. There is seldom medium-sized formwork. In cases in which large-sized formwork is used, the size of the form can be designed as large as practicable to reduce the amount of jointing and to minimize the amount of lift. The stiffness required by large-sized formwork can be dealt with by the introduction of more stiffening components such as studs and soldiers. The increase in the weight of the formwork panels is insignificant as a crane will be used in most cases.
Classification according to the location of use
There are not many effective formwork systems for stairs and staircases. The complicated three-dimensional nature of an element involving suspended panels and riser boards, as well as the need to cope with very different spatial and dimensional variances as required by individual design situations, cannot be achieved by a universally adaptable formwork system.
Classification according to materials of construction
Materials used for formwork are traditionally quite limited due to finding the difficult balance between cost and performance. Timber in general is still the most popular formwork material for its relative low initial cost and adaptability Steel, in the form of either hot-rolled or cold-formed sections and in combination with other sheeting materials, is another popular choice for formwork
materials. In the past two to three years, full aluminium formwork systems have been used in some cases but the performance is still being questioned by many users, especially in concern to cost and labor control
Classification according to nature of operation
Formwork can be operated manually or by other power-lifted methods. Some systems are equipped with a certain degree of mobility to ease the erection and striking processes, or to allow horizontal moment using rollers, rails or tracks.
Timber and aluminium forms are the only manually-operable types of formwork. They are designed and constructed in ways that they can be completely handled independently without the aid of any lifting appliances. On the other end of the scale, such systems are used in very large-sized and horizontally-spread buildings with complicated layout designs which require the systems' flexibility.
Figures below show the formwork system allowing the incorporation of pre-cast elements and self climbing form with hydraulic jack devices respectively.
Classification according to brand name of the product
Several patented or branded formwork systems have successfully entered the local construction market in the past decade. These include products from brands SGB, RMD, VSL, MIVAN, Thyssen and Cantilever. Each of these firms offers its own specialised products, while some can even provide a very wide range of services including design support or tender estimating advice. As the use of innovative building methods is gaining more attention from various sectors in the community, advanced formwork systems are obviously a promising solution. The input through research and development by the
well-established formwork manufacturers is of no doubt contributing to efforts
in these areas.
VSL FORMWORK (Source Raymond, 2001)
Loads acting on Formwork