Assessment of Timber Roof Structures before and after Earthquakes

The global objective of sustainable development has been greatly directed toward the preservation of existing structures. Therefore, condition assessment and reconstruction of existing timber structures have been gaining importance in recent times. This is particularly evident on timber roofs whose elements are exposed to degradation, either because of rheological effects or due to the direct influence of moisture and biological factors. In case of accidental events, such as an earthquake, the question of the structure’s condition is essential for the condition of the entire building. In order to prove the load-bearing capacity and serviceability of existing structures, as well as to check the need for reconstruction, it is necessary to define crucial parameters that are influencing the condition of materials, elements, and systems. Although there are many non destructive testing methods, the frequency and scope of their use, as well as the decision-making approach, have not been defined. In the paper, non-destructive and semi-destructive methods frequently used for timber structures are explained. A systematic review of criteria to be used in the assessment of load-bearing timber structures in a seismic active area was the main objective of this paper as well as the illustration of non-destructive and semi-destructive test methods through a case study involving roof construction of a hundred-year-old building in Zagreb, Croatia. Pre- and post-earthquake inspection was made. The overall condition of the roof structure after two significant earthquakes can be assessed as satisfactory given that the observed system is a large-span and massive roof structure. The presented results and identification of typical damages after the earthquake are presented in order to facilitate policy makers and for the future implementation of development strategies in the renovation of the city.

A preventive conservation approach for historical timber roof structures

PurposeThe purpose of this paper is to illustrate the assets of a preventive conservation approach for historical timber roof structures, as a means to improve the quality and durability of maintenance and repair interventions.Design/methodology/approachThe advantages of a preventive approach for historical structures were identified based on two analyses: a study of the structures’ behaviour and an investigation of existing approaches in current practice. The two main identified advantages of the approach, the cyclic process-approach and the potential of knowledge enhancement, were hereafter conceptually implemented in existing approaches.FindingsCurrent practices focus on single curative interventions, and monitoring is often considered redundant. The importance of monitoring and knowledge enhancement is demonstrated based on the theory of complex adaptive systems (CAS). A preventive conservation approach for historic timber roof structures allows integrating these insights.Research limitations/implicationsThe analysis of current practice is a sample survey, and the proposed preventive conservation approach is presented at a conceptual level. Future research foresees a more elaborated study of current practice and detailed validation of the developed approach.Originality/valueThree new contributions to the existing research on preventive conservation are: arguments for the implementation of a preventive approach, based on an analysis of the structures’ behaviour; the identification of limitations of current approaches that can be tackled in a preventive conservation approach; and the integration of the existing international guidelines and the principles of preventive conservation into a conceptual approach for the monitoring and management of these structures. Furthermore, the research paper demonstrates how timber structures can be understood as CAS, which is a novel viewpoint.