Implementation of the Results of Experimental Studies with the Use of the Sclerometric Method of Plane Elements in Wooden Buildings

Abstract

Wood is one of the basic building materials. It is a completely biodegradable raw industrial commodity, the resources of which, with proper forest management, are virtually inexhaustible. Additionally, its acquisition and processing does not require large inputs of fossil fuels. At the same time, forest areas which we obtain wood from neutralize the negative effects of producing and acquiring other raw materials, as one hectare of pine forest (the most popular in Poland) can absorb approx. 20–30 tons of CO2. Wood is characterised by low thermal and electrical conductivity, having simultaneously high sound insulation, which perfectly meets the requirements of the present market and its regulations. This study aimed at verifying the technical parameters of wood, i.e., its bending strength, with the use of an innovative method of the correlation between the bending strength measured along and across wood fibres. The procedure was envisaged as effective for testing the strength of beams in historic buildings, in which—due to their valuable structure—only a limited number of sample holes can be made. The aim of this experiment was to create tables and diagrams, from which, based on the correlation between the side and the head of the beam, using in situ tests and the sclerometric method, it will be possible to derive the bending strength of existing wooden beams. In the study of spruce and pine wood, a correlation between the recess from the side and the recess from the head was found, ranging from 0.64 to 0.76, with an average of 0.72 for spruce elements, and 0.66–0.84, with an average of 0.70 for pine elements. This means that when testing an element fixed in a building, measuring the parameters from the head of the beam with a Schmidt hammer (often such elements are more easily accessible, i.e., on the building facade), the obtained values should be multiplied by 0.72 for spruce elements and by 0.70 for pine elements to obtain the strength of the beam. The authors of this article indicate that the confirmation of this observation requires conducting further research on various types of wood. It should also be noted that the material collected from one batch of sawn timber had a different structure, which was proved by analysing it using SEM imaging. Modeling wood numerically is, to some extent, a simplified issue that assumes wood to be an orthotropic, homogeneous (homogeneous) material. In fact, wood is an anisotropic, very heterogeneous material. The analysis of wood (on the technical scale, construction wood) as an anisotropic material is practically impossible. Adopting wood as an isotropic material is too simplistic. Therefore, the most appropriate methods of strength testing are destructive methods, as all non-destructive methods should not be used without verifying the results with other methods. The results obtained by non-destructive testing pose great difficulties in their interpretation. Obtaining reliable results of experiments entails collecting a large number of research samples. The method described in this paper will allow for obtaining the necessary data for effective expertise assessment regarding the safety level of structural elements in historic wooden load-bearing structures, which is crucial for making conservation decisions.

Analysis of the Impact of Moisture and Biodeterioration On the Assessment of the Technical Condition Of Historical Buildings

“…In the case of wooden constructions, the examination of mycological changes includes the analysis of the state of fungus infestation with household fungi, mould, bacteria and also the occurrence of insects -technical wood pests [10,16,22,29].…”

Assessment of the Technical Condition of Timber Structural Elements Using Sclerometric Tests

“…Destructive tests provide the most reliable results but must be limited, particularly in heritage buildings, due to their destructive nature. Within the semi-destructive testing realm, scraping resistance tests [ 9 ], tear tests [ 10 ], and hardness tests [ 11 ] are noted. In recent years, a significant increase in the use of scraping resistance tests and hardness tests has been observed, correlated with the increased availability of the necessary testing equipment.…”

Restrictions and New Possibilities of Technical and Conservation Diagnostics of Wood in Heritage Buildings

“…The renovation of historic wooden structures is conditioned by knowledge of the mechanical capabilities of the preserved elements [1,2]. All research, carried out on the historic structure's tissue, in addition to the application of normative guidelines, is connected with additional obligations related to the compliance with conservation requirements [3][4][5][6]. In situ testing methods conducted in historic structures have many restrictions and eliminate the use of destructive testing.…”