Physics and Mechanical Wood
Ebrahim Khosravi; Amir Lashgari; Mehran Roohnia; Ahmad Jahan latibari; Ajang Tajdini
Abstract
Background and objectives: From the limitations of detecting the amount of useful life remaining in the components of the structures in the conditions of use with acoustic methods is the impossibility of calculating the modulus of elasticity due to the impossibility of removing the part from the structure. ...
Read More
Background and objectives: From the limitations of detecting the amount of useful life remaining in the components of the structures in the conditions of use with acoustic methods is the impossibility of calculating the modulus of elasticity due to the impossibility of removing the part from the structure. Therefore, most of the classifications during use in the components of structures such as historical buildings are based on measuring the speed of sound. In this research, to calculate the local and global density with the method of pin penetration rate in wooden tie in order to calculate the amount of their remaining useful life by combining stress wave and free longitudinal vibration methods has been studied. There was no significant difference between the values of global sound velocity and global modulus of elasticity with the local results of these factors at the five tested points in each of the wooden tie.Methodology: The number of three saturated wooden tie from Iran Railway Company and with the dimensions of 15x25x260 cm, which are made of beech species (Fagus orientalis) and the density was measured by pin penetration method at 5 points of each wooden tie (50 cm distance between each point) and the average results of 5 points were compared with the results of ISO 13910 standard method. The stress wave test was carried out at the same 5 points of density determination by pin penetration rate method to determine the local modulus of elasticity and the results of each point were compared with the global modulus of elasticity of the beam. Longitudinal vibration test was also performed to calculate the damping factor values of the samples.Results: The results showed that there was no significant difference at the 95% level between the values calculated with both the ISO 13910 standard methods and the pin penetration rate method, and there was a favorable linear correlation between the results of the two methods. According to the results, there was no significant difference between the global sound speed of the beams and their local sound speed in any of the five measured points at the 95% level and there was a linear correlation between the values of the global sound speed and each of the five local points. There was no significant difference at the 95% level between the values of the global modulus of elasticity and the values of the local modulus of elasticity calculated in each of the five points. Also, there was a linear correlation between the values of the global modulus of elasticity and the results of the local modulus of elasticity in each of the five points. There was an exponential correlation between the values obtained from the global modulus of elasticity and the damping factor of each of the wooden tie.Conclusion: The equality of density according to the ISO 13910 standard method and the nail penetration method, as well as the equality of the modulus of elasticity calculated by the stress wave method and the free longitudinal vibration method, make it possible to obtain all the data required for calculations without removing the part from the structure. The remaining strength of wooden components should be provided according to EN338 standard.
Sana Lotfi; Mohammadali Saadatnia; Mohammad Hadi Moradian; ladan pour sartip
Abstract
Ensuring the quality and stability of trees as the most important components of the plant community has attracted the attention of foresters to identify and measure defects and ensure safety coefficients. Therefore, in the present study, the use of acoustic tomography to calculate the extent of decay, ...
Read More
Ensuring the quality and stability of trees as the most important components of the plant community has attracted the attention of foresters to identify and measure defects and ensure safety coefficients. Therefore, in the present study, the use of acoustic tomography to calculate the extent of decay, the area of the woody section and the safety factor of black pine was studied. Acoustic tomography was performed using 16 sensors at two heights of 147 and 200 cm above the ground and on 8 tree specimens in the Sopron region of Hungary. The results showed that the stress wave technique was an accurate method for determining safety coefficients and determining the amount of internal decay in the tree and also had the ability to identify compression areas in cross section. Resistography of the studied sections in different geographical directions assisted to locating the woody areas, which was compatible with the information of acoustic tomography. The findings of this study showed that the area of the canopy has a significant role in the safety of the tree and the possibility of tree fall, so that in some trees due to their condition, with doubling the area of the canopy, the torque increased from 80827 to 161655 N.m and the condition of the tree changed from low-risk to high-risk.
