Sawn timber used in load-bearing building structures shall comply with the requirements given in harmonized European standard SIST EN 14081-1. Timber shall be either visually or machine graded. Machine grading is based on non-destructive testing (NDT) methods. Considering so called grade indicating properties measurements, timber pieces are graded into previously defined strength classes. Through visual grading each piece of timber is evaluated based on visual parameters. Visual grading rules consider the conformance of surface strength reducing, geometrical and biological characteristics to limitations established within each grade category. On that basis, so called visual strength grades (Sortierklassen) are assigned. Considering visual strength grades, species and sources of timber, strength classes can be assigned according to SIST EN 1912.
F.17 Transfer of existing technologies, know-how, methods and procedures into practice
COBISS.SI-ID: 1802633This paper discusses the importance in the Slovenian structural timber industry of establishing a system of internal production control and of acquiring the relevant certification. Producers of structural timber must mark their products with the CE mark, which is mandatory for all construction products in the European Union, and must have the aforementioned certification. The article also lists the technical specifications with which solid wood construction must comply.
F.17 Transfer of existing technologies, know-how, methods and procedures into practice
COBISS.SI-ID: 1769097The paper presents the standard for strength graded structural timber with rectangular cross section in details. Aspects of visual strength are specially exposed. Additional explanation of requirements for raw materials, factory production control and attestation of conformity is given. The paper was published in the main printed publication of Slovenian Institute for Standardization in order to present the standard requirements to all Slovenian sawmills.
F.31 Development of standards
COBISS.SI-ID: 1865319The report shows the information about the origin, quality and diameter of selected logs and method of production of sawn timber. It describes the method used for visual strength grading of sawn timber and method of determining the grade determining values by destructive tests. The results of visual grading and destructive tests were used to calculate the characteristic values of sorting grades of sawn timber made from Slovenian spruce and fir. These results are the basis for including Slovenia to the EN 1912 list, according to which the transformation of sorting to strength classes are made.
F.31 Development of standards
COBISS.SI-ID: 5349217Good knowledge of the characteristics of building material is of the utmost importance in static calculations in civil engineering. The characteristics of a piece of timber may vary depending on the growth area, log, and cutting. Therefore, each piece of timber should be examined separately. The examination is based on non-destructive testing, distinguishing – as in our case – between different strength grades. Eurocode 5 refers to the EN 14081 standard, which allows visual and machine grading. In order to identify the differences between the two, we carried out several measurements and compared them. We used several non-destructive methods (visual grading, longitudinal wave propagation, ultrasound, bending test and longitudinal frequency). Results of each non-destructive method were compared to the bending strength obtained with the destruction method. We made some correlations and evaluated them. The specimens were classified into optimal strength grades and the results compared with strength grades obtained by selected nondestructive methods. We also tested a prototype device developed during the project and compared it with other devices and visual standards. The device did well. Assuming that our sample is representative for Slovenia, we can conclude that the majority of Slovene timber can be classified into strength grade C30. Considering that in civil engineering the mark most widely used in practice is the old mark from the JUS Standard – class II or today's C24 –, structural design is on the safe side despite the lack of knowledge concerning the actual characteristics of wood. However, this is certainly not economical, since the timber is not used to its full potential. With the use of grading machines, most construction timber can be classified into strength grade C30 without major reject.
D.10 Educational activities
COBISS.SI-ID: 6059617