Disaster of an industrial hall caused by an explosion of wood dust and fire

• A case of a disaster of a roofing structure made of prestressed girders is presented.
• The cause of the damage was an explosion triggered by the self-ignition of wood dust.
• The resultant flame caused a secondary explosion of the dust accumulated in the hall.
• Gradual loss of the prestressing force could have resulted in the girders’ collapse.
• Instead of the demolished prestressed girders, steel truss girders were used.

This article scrutinises a disaster affecting an industrial hall built of prefabricated reinforced concrete. As a result of an explosion of technological equipment used in the woodworking process, the entire pretensioned prestressed concrete girder structure, as well as the roof slabs, was badly damaged. Additional damage was caused by the high temperature generated by the resultant fire, as well as rapid cooling due to fire-fighting activities. Increased air pressure and the ensuing shock wave caused extensive damage to the brick walls in the neighbouring technology rooms. The explosion caused deformations of a brick chimney located more than 100 m from the blast zone. Subsequent investigations showed that a lack of adhesion of the tension members in the contact zone with an incoherent concrete structure could have led to a complete destruction of the covering structure. In the degraded girders located directly above the explosion area, a gradual loss of the prestressing force was observed. To prevent spreading of the disaster, ad hoc operations to protect both the structure of the building and the remaining technological equipment were developed. The girders located directly in the explosion zone were temporarily propped up and prepared for immediate removal. The article also presents an account of the reconstruction of the damaged building. In place of the removed prestressed girders, a light cover supported on truss steel girders was designed. The investigations that followed confirmed that an immediate cause of the hall’s damage was destructive processes triggered by the self-ignition of a mixture of wood dust in the improperly ventilated wood processing machinery. The resultant flame brought about a secondary explosion of the dust accumulated in the hall. The lack of proper human supervision of the industry control systems additionally increased the extent of the damage and financial losses.

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