INVESTIGATION OF DEFECTS AND DAMAGE IN TIMBER TRUSSES

Abstract

The identification of defects and their timely remediation in structures in service constitute a key factor in ensuring the durability and reliability of buildings and civil engineering structures. This study presents the results of investigations of timber trusses that have been in long-term service. The most common defects and damage affecting truss members during operation are analysed. The research is based on the examination of ten different structures incorporating timber trusses with various geometric configurations. A statistical analysis of the frequency of occurrence of the identified defects and damage was carried out. The detected defects were compared with the defect classifications specified in relevant regulatory documents. The results indicate that almost all defect types listed in the regulatory literature are observed in structures employing timber trusses. In addition to the defects identified in the standards, additional types of damage were detected, including contamination of timber structural elements with bird droppings. Furthermore, a significant deficiency of timber trusses in service is the lack of documentation and the absence of systematic application of protective treatments.
Of the defects identified, prolonged and repeated moisture exposure was found to have the most adverse impact on timber truss members, promoting fungal activity and subsequent wood decay. Decay of timber, especially in joint regions, results in a substantial reduction in the service life of timber trusses.
The results of the study indicate that the most prevalent defects in timber truss members are longitudinal cracking due to wood shrinkage and corrosion of metal components in joint connections. The next most prevalent defect observed in timber trusses is the lack of information regarding treatment with protective agents (antiseptics and fire retardants). Given the frequent occurrence of timber infestation by wood-boring insects, as well as the necessity to comply with fire safety requirements, maintaining systematic and documented treatment of timber elements with protective substances is of critical importance.