Assessment of the technical condition of the connections between panels of prefabricated large-panel dwelling buildings

The structural stability and durability of prefabricated large-panel residential buildings depend significantly on the condition of the connections between the load-bearing panels. These connections ensure the structural integrity of the building and enable it to safely resist the design loads. This study aims to assess the current structural condition of the connections between the load-bearing panels of existing prefabricated large-panel residential buildings in Bulgaria. Both non-destructive and destructive testing methods were employed. The non-destructive methods included visual inspection of the panel connections and estimation of the concrete compressive strength based on the rebound number. The destructive methods included determining the depth of concrete carbonation, assessing the presence of corrosion in the reinforcement, measuring the lengths of welds between reinforcing bars, and conducting other localized investigations. The obtained results indicate that, in general, the measured weld lengths meet the required criteria with respect to the reinforcing bar diameters. Although considerable concrete carbonation was observed, no significant signs of advanced reinforcement corrosion were found in most of the investigated connections. Furthermore, the estimated concrete compressive strength meets the general requirements for this type of prefabricated large-panel residential building. Overall, the investigated panel connections were found to be in satisfactory technical condition. A higher degree of reinforcement corrosion may occur in connections located in areas with elevated humidity, such as bathrooms and other sanitary facilities, particularly where maintenance has been inadequate. However, the number of investigated connections is not sufficient to draw definitive conclusions regarding the overall condition of all buildings of this type. Nevertheless, the findings provide no evidence of widespread structural deficiencies, particularly in the load-bearing panel connections, within the investigated buildings.