Curtain wall is defined as a thin wall made generally using aluminum frame. This frame is fitted with metal panels, thin stones or glass. This framing does not carry any building load and is attached with the building structure. The wind load on the
curtain walling and its weight is generally transferred to building structure generally at the floor level. The use of curtain wailing technique in building construction started in the 30's. After the end of World War II, it became more popular because of easier availability of aluminum for civilian use.
Curtain walls are generally made as manufacture's standard catalog item or it could be custom built. Curtain walls are generally economic compared with standard system used earlier because it provides more wall area.
Curtain walls may be classified into two types by the method of their manufacture. They are:
" Stick system
" Unitized or Modular system
In the Stick system, the curtain wall frame and the panels to be fixed on this frame are installed and put together piece by piece.
In case of Unitized system, the curtain wall is made up of large units which are assembled and glazed in a factory and then transported to the site in the assembled condition. Vertical and horizontal frame of each module are fixed together with the adjacent module. Generally, these modules are constructed one story tall and about five or six feet wide.
These curtain walls could also be classified, according to water protection given, as water managed or pressure-equalized. Face-sealed types are also there, but they are not very popular.
These curtain walls could be designed with either external or internal glazed systems. In the interior system, panel s could be installed into curtain wall frames from inside of a building. For low rise buildings, external glazing system is generally specified because of easy access from outside. The panels for these curtain walls are installed from outside and they require scaffolding to do so. Glazing of some curtain walls could be done both from inside as well as from outside.
The rainscreen principle used in curtain wall design is based on the principle that air pressure outside and inside of rainscreen should be equilibrated to prevent water to get in. Typically, glass panels are fixed between inner and outer gasket in a space called glazing rebate. Glazing rebate is ventilated to the outside, so that air pressure inside and outside of the gasket get equalized. Because of this water does not get in.
Curtain wall transfers all loads coming on it to the building structure through the anchors attached to the frames of the curtain walls. The building design must consider all the loads coming on the curtain wall.
Some these load factors could be:
" Dead load
" Wind load
" Seismic Load
" Snow Load
" Thermal Load
" Blast Load
Dead load is considered to be the load produced by the weight of all structural elements and other permanent elements of the structure. Wind load is because of wind blowing on the building. Seismic Load is to be decided according to the seismicity of the place. Because of terrorist activities going on nowadays, blast load is also considered in the design.
