The main task of light removable structures is to preserve life and health of people in case of an explosion within a premise, as well as to protect the building structures and equipment from destruction.
Construction norms govern mandatory usage of light removable structures in A and B explosion and fire hazard category premises. Most frequently these are oil and gas sites, metallurgy, chemical industry, power complex, flour mill, hospital, and other buildings.
The principle of light removable structures operation lies in quick reduction of the growing pressure in the premise in case of explosion, through depressurizing a part of the building envelope.
For certain categories of buildings, there exists the risk of the pressure exceeding 5 kPa in case of explosion. In this case, light removable structures are designed so as to depressurize a part of the facade or roof, if the design pressure of an explosion is reached.
To ensure stability of buildings in case of internal explosions, glazing or sandwich panels with mineral wool core can be used as light removable structures.
Light removable structures of Ruukki mineral wool panels meet the highest energy efficiency and fire protection standards and thus can be applied for all categories of premises. The specially developed fixing technology allows to exclude cold bridging and to obtain as energy-efficient building envelope as possible.
To ensure safety of people and material values both inside and outside the building, the following needs to be take account of in design of light removable structures from sandwich panels:
Ruukki sandwich panels can bear a local load of over 50 kN/m2 onto their surface, which normally satisfies the design loads in case of gas explosion inside a building.
Facade of a light removable structure with vertical sandwich panels
The area of light removable structures shall be determined through calculation or with the help of recommendations provided in industry norms and standards (DBN, DSTU, NAPB etc.). For instance, for grain storage and processing enterprises, buildings, and structures, DBN V.2.2-8.98 specifies that in case of absence of calculation, the area of light removable structures for external walls needs to be taken at least 0.03 m2 per 1 m3 of an explosion hazard premise.
Facade of a light removable structure with horizontal sandwich panels
The light removable structure of sandwich panels is fixed to the bearing frame of the building with the help of nails for concrete or metal screws with small diameter washers. In addition, steel ropes Ø8 mm, fixed to the external facing of panel with clips at 100 mm spacing, are hung along the lengthy side of light removable structure. The rope is fastened at the ends with the help of ring bolts fixed to columns or cross beams. When laying the rope, it is necessary to secure loops, which would prevent the structure from falling after an explosion. The whole system of fixing light removable structures is closed with a decorative batten, which allows ensuring architectural attractiveness of the facade and protecting the structure from atmospheric impact.
To determine the type and number of fixings for a light removable structure, Rauta specialists use the Traypan software. The calculation consists of determining the bearing capacity of fixing elements at the design wind pressure and at explosion with over 2 kPa internal pressure inside the building.
The example of calculation of fixings of light removable structures from Ruukki sandwich panels with size 18×8.8m and 6 m column spacing is shown below.
In case of wind load 0.28 kN/m2, the coefficient of usage of the fixings’ bearing capacity does not exceed 38.9%.
In case of emergence of explosion load of 5.28 kN/m2, the coefficient of usage of the fixings’ bearing capacity increases till 348.5%.
Calculations show, that usage of 4 SFS STD14-S19-5.5 self-tapping screws is sufficient for bearing wind loads, but in case of explosion, such fixing will fail and ensure correct operation of a light removable structure.