ABSTRACT Background: In timber structures, connections are the most important and critical section which supply the strength of each structural element. The aim of this study was evaluation the behavior of epoxy resin reinforced by nanoclay (at three levels) on the pull-out strength of glued-in GFRP rods in glulam. For this purpose, two rods with three lengths (50, 150 and 250 mm) and diameters (6.4, 12.7 and 19.1 mm) were inserted at two opposite sides of glulam blocks (with dimension of 8.89 x 8.89 x 29.94 cm) which were glued by epoxy resin. Samples underwent tensile testing and their tensile strength and shear strength were measured. The obtained data were analyzed statistically and the effects of studied factors on bond strength were evaluated. Results: The results showed that the strength of bonding increased with the addition of a low amount of nanoclay, and the length of the rod had a greater effect than its diameter. Furthermore, the amount of nanoclay, rod length and diameter could not significantly affect simultaneously, the performance and strength of glued-in GFRP rods. Conclusion: Nanoclay particle can be considered as a reinforcement for epoxy resin in glued-in GFRP rods and its effect may cause a considerable increase in the mechanical strengths of joints.

ABSTRACT Background: Many historical buildings in Iran need to be protected. In many of these buildings, wood is used as a structural element in features such as beam, pile, roof and floor systems. For this purpose, the architectural features of a historical building located in Gorgan (Northern part of Iran) and characterisation of faults, in addition to identification of wood species were conducted. Stress wave non-destructive testing (NDT) was used and wave speed (WS) was measured in tested members to evaluate the decay situation of major wooden beams of building frames and roof truss. After obtaining data related to WS, time of wave transition (TWT) was calculated and compared with control time. Structural elements were characterized in comparison with control time and classified according to decay severity. Results: The results showed that local hardwood species were used for construction of this building. Furthermore, in some parts of the building, there were severely defected structures, thus highlighting the importance of safety. Moreover, WS strongly depended on the types of faults. Conclusion: Due to high relative humidity of climate, wood structures are exposed to faults in the northern region of Iran. However, their general appearance is adequate and acceptable. For better decision making, the TWT should be accompanied by more investigation into the types of defects.

Abstract: Vibrational spectroscopy approaches like FT-IR and FT-Raman, as analytical method, can be used to assess chemical changes in historical wood structures. In this study, wood samples of three historical buildings, in Gorgan, Iran, namely Tekie Estebar, Molla Esmaiel Mosque, and the Esmaieli Buildings were selected. Wood species was determined by their macroscopic characteristics which were hornbeam (Carpinus betulus), oak (Quercus castaneifolia), beech (Fagus orientalis), and elm (Ulmus glabra), as hardwood species, and yew (Taxus baccata) as a softwood species. Also, some samples of oak were collected from northern and southern sides of the Esmaieli Building in order to compare deterioration environmental factors.. The approximate assignment of the experimental bands was completed by comparing. For this purpose, the experimental bands with the calculated band frequencies of cellulose, hemicellulose and lignin. In addition, the reported assignment for softwood and hardwood was used to confirm the vibrational assignments. The results of spectroscopy revealed that biodegradation had occurred in all species. Comparison between the most important vibrational band frequencies related to carbohydrates and lignin in hardwood species suggested that degradation of carbohydrates was greater than lignin, which could be attributed to brown rot and hydrolysis. Reduction of chemical compounds in south oak samples was higher and could be associated with prevailing wind and UV ray in this side. In the only softwood species (yew), because of its highest exposure to frequent raining, deterioration was observed in both carbohydrates and lignin.

Abstract: This paper aims to introduce a relationship between the dynamic modulus of elasticity in healthy standing trees of Paulownia fortune (planted in Iran) and the static modulus of elasticity in sawn wood. For this reason, a stress-wave non-destructive testing technique was carried out in longitudinal and transverse directions in 14 trees into two diameter classes (25-31 cm and 32-38 cm) at breast height and in logs at different height of stem to measure the stress wave speed and consequently, dynamic modulus of elasticity. Then, static modulus of elasticity of samples was calculated using 3-point bending tests in the sawn wood. The results revealed that the stress-wave speed and dynamic modulus of elasticity in logs of Paulownia are more than those of standing trees in longitudinal direction. Also, the diameter of the tree can significantly affect the stress wave velocity in standing trees and logs of Paulownia. Finally, a high correlation coefficient exists between static modulus of elasticity and dynamic modulus of elasticity (r= 0,68) in this tree.