Consequences of an incorrect assessment of a structure damaged by explosion

• Published in: Engineering failure analysis 2019-07, Vol.101, p.135-144
• Main Authors: Krentowski, Janusz, Ziminski, Kamil
• Format: Article
• Language: English
• Subjects: Biogas explosion; Concept of strengthening; Durability; Failure condition; RC fermentation chamber
• ISSN: 1350-6307; 1873-1961
• DOI: 10.1016/j.engfailanal.2019.03.009

The authors indicate the consequences of an incorrect assessment of the condition of a structure that has been damaged as a result of a disaster or failure. The presented thesis is illustrated by progressive degradation processes of fermentation chambers in a digestive sewage tank. The degradation originated from biogas explosion, which in turn, led to unidentified damage to the reinforced concrete structure, thus the tank was not excluded from further service. The justification for allowing the faulty structure to be put into operation were errors in the assessment of the stress function resulting from using inadequate data concerning the cross-section of the concrete reinforcement and concrete strength undertaken by the user. The changes in the tank's static structure as a consequence of the biogas explosion were not taken into account. As a result, the leaks were observed immediately after beginning of the water test. Consequently, the state of the effort of the tank's structure both at its design stage and during its instantaneous pressure load caused by explosion had to be analyzed again. The impact of the cracks found in the tank's reinforced concrete walls on the safe operation of the facility for collecting liquid medium has been also considered. It was shown that the tank's walls in their central part failed to meet the conditions of ultimate limit state and serviceability of the reinforced concrete ring cross-section subjected to an exceptional load. Conditions for safe operation of the repaired facility, taking into account the change of the static scheme of the structure have been reconsidered. The paper is concluded with a presentation of the concept of restoring the correct durability of the structure to ensure safe resumption of the technological process. Additionally, recommendations were made concerning assessments of structures damaged as a result of a breakdown or building disaster. [Display omitted] •Results of biogas explosion in the digester of the sewage treatment plant are presented.•Consequences of an incorrect assessment of the condition of a damaged structure are described.•State of effort of the tank elements both in operation and after the explosion has been verified.•A concept of repairing cracked walls and covering the digester has been proposed.•Guidelines for the use of facilities reconstructed after a disaster or breakdown are formulated.