Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Determination of Bending Strength and Modulus of Elasticity in Wooden

Beams With Nondestructive Test Methods
In this study, non-destructive evaluation and classification methods’ suitability was examined in Black Pine (Pinus nigra ssp. pallasiana) lumbers which will be used as beams.
Samples were taken from about 200 lumbers in Istanbul University Forest Faculty Forest Industry Engineering Department. 53 lumbers were taken by using TS 1265 visually grading standard and lumbers were taken to be en equal amount of each class. After measuring densities and moistures, the samples were visually graded separately with using four standards (TS 1265, DIN 4074, BS 4978 and TS EN 14081). After this, they were evaluated and graded with using three different non-destructive methods (longitudinal vibration, stress wave and screw withdraw). After these experiments, these lumbers’ bending strength and modulus of elasticity were measured destructive methods in order to TS 5497 EN 408 standard. And then these broken lumbers were classified with using their elasticity of modulus and TS EN 338 standard. After destructive tests, five specimens from each lumbers’ which were near the lumbers’ broken area were taken for to measure bending strength-modulus of elasticity, compression strength and density from little and without defect specimens. At last, these specimens’ air dry densities and no-moisture densities were measured. For no-moisture density measurement, air dry specimens were dried until to have no moisture.
Non-destructive evaluations (and classifications) in structural dimensions were compared each other and were compared destructive evaluations (and classifications) in structural dimensions and in little and without defect dimensions. And they were compared and analyzed statistically.
In this study results showed that, two visually grading standards (BS 4978 and TS EN 14081) more predictable for mechanical evaluation. Although, instead of visual grades directly use, they were advised to be guide non-destructive and destructive tests. It’s said that, longitudinal vibration method which is used for non-destructive evaluations and classification, can be used with high accuracy in Black Pine (Pinus nigra ssp. pallasiana) structural lumbers. Although stress wave non-destructive method has no classification, this methods’ dynamic elasticity of modulus were changed to strength classes according to TS EN 338 standard with using formula which were seen in longitudinal vibration method. Although it has predictable results, more predictable evaluation and classification results can be obtained with measuring more tests in same lumber. Screw withdraw method is only predictable density results but if it used with non-destructive methods, it would be more predictable. These positive results indicate that, these methods can be used in wooden beams.