Precast Concrete Floors Details: To create in-situ concrete floors, instead of using in-situ cast frames, you can use structural steel frames with either planks tee beams, precast reinforced concrete flooring beams or beam and infill blocks that do not require much support and which have a structural or screed covering spread on.
The benefits of concrete is that it is robust, durable, fire resistant, has innate thermal properties, does not require much maintenance and is relatively easy to install.
Solid composite flooring are fixed on site and are able to bear larger loads as they not only have the benefits of standard units but also feature a structural concrete topping.
The design of hollow composite flooring means that hollow core units are used along with a structural topping thus allowing enhanced load bearing capacity.
When using either solid or hollow core flooring which rest on structural steelwork, a balance can be reached by introducing and designing the steel beam to work in harmony with the precast units.
This can be attached to the structure by welding shear studs into the upper flange of the beam and then reinforcing with in-situ concrete.
This addition enables a balance in load as it improves the load capacity of the united section and reduces the pressure places on the steel beam.
Most companies that deal with manufacturing precast concrete tend to operate according to LEAN principles which target waste reduction and maximising efficiencies consequently avoiding and rectifying problems which enables production of superior end products.
Precast concrete floors mixed with steelwork
The use of structural steelwork is something that is very high profile in countries like the UK, the US, Australia and Japan.
The reason for its success? This is due to the flexibility of the design, the procurement process and the construction.
Many of the factors for this success has been denied for the precast concrete industry, and this is why steel has succeeded in being a major building material in its own right.
When you mix precast concrete with the properties of structural steel, the benefits of this are clear in some cases, but in other cases this isn’t true.
The properties involved with these materials, including thermal, acoustic, maintenance, appearance and fire resistance are becoming increasingly common components in modern construction.
When considering the substitution of a precast element with a steelwork structure, you need to be careful in making the decision.
When working with precast concrete, this material is sometimes used in conjunction with structural steelwork.
If you’re planning on having long span precast concrete floors, then a good idea would be to use steel beams for support.
Precast beams can help support metal decking floors, and precast walls can be used as a way to brace steel frames.
There is also the ability to use precast frames in order to stabilize steel cross bracing, or to use precast columns to support lightly loaded roofs or roof frames.
When most engineers visualize a “mixed” prefabricated material in construction, they often picture precast concrete floors which are supported on steel beams.
This is taking advantage of composite action, and this can be achieved by utilizing a small number of shear studs, as well as small amounts of reinforced insitu infill, which will fill the ends of the slabs.
There is a huge market for precast concrete floors with steel frames, with about 15 million square meters of it being used in European construction alone.
The details for construction with these materials are very well established, despite the fact that they may not be actually the most economical or the most structurally efficient for building projects.
Construction project designers need to be aware and recognize that there are a full set of implications of bringing these two building elements together.
For example, the reduced shear capacity of a hollow core unit is supported using flexible steel beams.
This happens as a result of it bending the perpendicular span of the floor unit, which induces additional shear stress.
There is a design procedure that recognized and analyzes this problem to help address it.
The reduced shear capacity of the interface shear studs occurs when connecting the hollow core units to the steel beams.
This is due to a confined stress zone that occurs in the gap between the ends of hollow core units.
There is sometimes an issue when it comes to making a three edge slab with supports at the gable end beams.
All of the longitudinally supported edges may cause torsion in a unit, which may or may not actually reduce a shear capacity for a unit.
With hollow core unites that have a 6-12m span or a 150-300mm depth are used in most cases for steel frames.
If a construction projects floors are made to be structurally isolated from a steal beam with a horizontal diaphragm, then there needs to be steel cross bracing or in a reinforced structural top.
Note that the tie and its forces must in either case be continuous and connected to stabilize elements.
These are just a few of the elements and considerations that need to be made when using precast concrete and steel framework as building elements in a construction project.