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Bending properties of Turkish red pine (Pinus brutia Ten.) lumber pieces were predicted using the stress wave method. The lumber samples were taken from 30-to 80-year-old red pine trees harvested from a southwest site in Turkey. MTG timber grader was utilized to predict modulus of elasticity (MOE) and modulus of rupture (MOR) values of lumbers with 40 mm x 90 mm in cross section and 3 meters in length. Static MOE and MOR values of the lumber pieces were determined using a three-point bending test. The coefficient of determination between measured and predicted MOEs was 0.84 and that between dynamic MOE and bending strength was 0.69. However, the coefficient of determination between bending MOE and strength was only 0.45. It seems that dynamic MOE has better prediction capability for bending strength than static MOE. Effects of some variables such as log and visual grades on dynamic MOE values were also determined statistically. Natural frequency of the lumbers showed far more significant effects than other variables. It is apparent that the stress wave method has the potential to predict the bending properties of Turkish red pine lumber.

In this study, the influence of moisture content on some orthotropic mechanical properties of sessile oak which is one of the most important wood species grown in Turkey and common in the furniture industry have been investigated. The properties studied include Young's modulus, Poisson's ratios and compression strength of oak wood in three anatomical directions. These properties are important input parameters for three dimensional modeling of mechanical behavior in advanced computer programs such as finite elements. The samples which were approximately 20 x 20 x 60 mm in dimensions were conditioned at 20 °C and 50, 65, 85, 95 % relative humidity conditions for 6-8 weeks and subjected to compression tests in order to determine elastic and strength properties. Results indicate that properties investigated significantly differ among all anatomical directions. Young's modulus ranged from 10305 to 6984 N/mm 2 in L direction, from 2032 to 1132 N/mm 2 in R direction and from 1208 to 715 in T direction. Compression strength varied between 48.5 and 25.5 N/mm 2 in L direction, 16.45 and 9.60 MPa in R direction, and 10.2 and 7.1 in T direction. Poisson's ratios are found to be in between 0.061 and 0.7. Results indicated that all properties of the samples tested were strongly affected by moisture content.

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Compression properties in three orthotropic directions for some important Turkish wood species, including Calabrian pine (Pinus brutia Ten.), Taurus cedar (Cedrus libani), Oriental beech (Fagus orientalis), and sessile oak (Quercus petraea), were studied using non-destructive and destructive techniques. The materials used in the study consisted of 720 small clear specimens of nominal dimensions of 20 x 20 x 60 mm. The influence of equilibrium moisture content (EMC) was studied over four batches of 15 specimens each, conditioned for six to eight weeks before testing at a temperature of 20 ± 2 °C and at four different relative humidity conditions (50%, 65%, 85%, and 95%). Time of flight values were measured with a commercial ultrasonic tester. Using the time results from the ultrasound device, the wave velocities (length/time) and Edyn values were calculated. Samples were also tested in uniaxial compression to determine the Young's modulus and compression strength values in three orthotropic directions. The Edyn correlated well with the Young's modulus and compression strength of the specimens; coefficients of determination ranged between 0.75 and 0.96. Moisture content seems to have more influence than density on sound velocities. Results showed that there is a weak and mostly negative correlation between the density of the specimens and the sound velocity values.

In this study; bending properties of beech wood (Fagus orientalis) were predicted using stresswave method and compared with static bending tests. First, lumbers which were different in length and cross section were weighed and dimensions were measured. Then, moisture contents were obtained via moisture meter. By using the density, moisture, and dimensions of the samples in MTG Timber Grader device, dynamic modulus of elasticity values were determined. And then, samples were subjected to 3 point bending test. Modulus of elasticity and bending strengths were calculated using load -deformation curves. Regression models were developed to interpret relationships between dynamic modulus elasticity and bending properties. Results showed that there is a high regression coefficient (0,86) between dynamic modulus of elasticity and static modulus of elasticity. Regression coefficient between dynamic modulus of elasticity and static bending strength was measured as (0,72) and regression coefficient between static modulus of elasticity and static bending strength was measured as (0,74). Results indicate that bending properties of beech wood lumber can be predicted using stress wave method.

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ÖzetBu çalışmada kızılçam kullanılarak üretilmiş ve cam lifi ve çelik plaka ile güçlendirilmiş tabakalı kerestelerin eğilmedeki performans özellikleri araştırılmıştır. Tabakalı kerestede eğilme özelliklerini iyileştirmek için lokal güçlendirme yapılmıştır. Çalışmada kızılçam kerestesi kullanılarak 15 adet 10 x 200 x 3000 mm ölçülerinde tabakalı kereste örnekleri üretilmiştir. Bütün örneklerin en alt katmanı parmak dişle birleştirilmiş iki keresteden; üstündeki katman tek parça keresteden; orta ve üstü katman parmak dişle birleştirilmiş altı elemandan ve en üst katman ise tek elemandan oluşmaktadır. Dolayısıyla kontrol örneklerinde kırılmaların en alt tabakada parmak dişli birleştirmede olması planlanmıştır. Güçlendirme işlemi cam lifi ve çelik plaka kullanılarak gerçekleştirilmiştir. Tabakalı kereste örneklerinin üç nokta eğilme testi ile performans özellikleri belirlenmiştir. Çalışma sonuçlarına göre kızılçam kullanılarak üretilmiş tabakalı kerestelerde elastikiyet modülü cam lifi ile % 14, çelik plaka ile % 24 artmıştır. Cam lifi maksimum yük taşıma kapasitesini% 27, çelik plaka ise % 36 arttırmıştır. Güçlendirme tabakalı kirişlerde kırılma modunu da değiştirmiştir.Anahtar kelimeler: Kızılçam, Tabakalı kereste, Güçlendirme, Cam lifi, Çelik plaka Effects of Fiberglass and Steel Sheet Reinforcement on the Bending Performance of Glulam Beams Constructed with Turkish Red Pine (Pinus brutia Ten.) AbstractA study was conducted to investigate the bending performance of glulam beams constructed of Red pine reinforced by fiberglass and steel plates. Local reinforcement is proposed in order to improve the flexural strength and stiffness of glulam beams. For the study, 15 full size glulam beams constructed of Turkish red pine lumber were produced. All beams had similar 5 layers consisting of two finger-jointedmembers at the bottom, a single member at the fourth, six finger-jointed-members at the third and second layer and another single member at the top. Glulam beams were tested using three-point bending test to determine their load-deformation behavior. According to test results, elasticity of the glulam beams can be improved 14% and 24% using fiber glass and steel plates. Similarly, maximum load carrying capacity of glulam beams constructed of Turkish red pine lumbers may be improved 27 % and 36 % by using fiberglass and steel reinforcements, respectively. Reinforcement also changed the failure mode of glulam beams tested.