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In order to strengthen the seismic design and diagnosis of glulam building structures, and improve the accuracy and reliability of building modal analysis, this paper uses the designed glulam frame structure as a research object to conduct experimental investigation on its dynamic properties. On the one hand, a computational modal analysis is carried out using ANSYS to determine the modal shapes and modal parameters of the glulam frame structure. On the other hand, transient excitation, steady-state contact excitation and steady-state non-contact excitation methods are used to test and analyze the experimental modalities of the field-built larch glulam frame structure. The research results show that the three experimental modal methods can all measure the biaxial(xy-) first-order bending, first-order torsion, and second-order bending modes of the glulam frame structure. The vibration shapes and modal frequencies are all consistent. The results of computational modal analysis and experimental modal analysis are combined in this article. Since the elastic constant input of components is measured by grading, the frequency values of the computational mode are larger. The error of the two analyses is about 15%. In the first-order bending mode in the x- and y-directions, both the computational and experimental modes show the characteristics of greater local stiffness in the gusset. In the uniaxial (x- or y-) torsional mode, the computational mode not only reflects the torsional characteristics of the upper beam region, but also shows first-order bending mode of the column, which is also consistent with the experimental mode.

In order to improve the sound absorption performance of the light-frame timber construction wall, this paper combined the aperture embedded wall unit structure with the actual building wall structure based on the Helmholtz resonance structure principle to design and fabricate two sets of wall structures: a new aperture embedded Helmholtz resonance structure (experimental group) and a conventional structure (control group). The sound absorption coefficients of the two wall structures were measured by the reverberation chamber test, and related analysis was carried out. The results showed that the aperture embedded Helmholtz resonance wall structure exhibited good sound absorption performance in the low frequency range; in particular, a perfect sound absorption effect was basically achieved at a frequency of 100 Hz. Compared with the conventional wall structure, the sound absorption performance of the aperture embedded Helmholtz resonance wall structure in the test frequency range was enhanced greatly. While the value of the sound absorption coefficient was increased in the low frequency range, the bandwidth of sound absorption frequency was expanded to a certain extent, and the average sound absorption coefficient and noise reduction coefficient were both improved. This paper explored the applicability of Helmholtz resonance structure in practical wall structure. The research results could provide reference for reducing indoor noise pollution and creating a better living environment.

Using the static analysis of ANSYS 19 longitudinal, radial, and transverse beam specimens of spruce, pine, and beech were subjected to stress and strain analysis under symmetrical four-point bending and asymmetrical four-point bending, respectively. The effects of wood grain on the surface of the specimen and its stress properties on the transverse and longitudinal strain at the center of the specimen surface were studied experimentally. The results show that the four-point bending beam method is suitable for testing the elastic modulus, Poisson's ratio and shear modulus of wood. The elastic modulus, Poisson's ratio and shear modulus of Larch chord and radial and Western Canadian spruce transverse specimens were tested by four point bending beam method. Their effectiveness was verified by axial tension method, square plate torsional strain method and free rod torsional vibration method. The four-point bending method of two groups of half bridge test has successfully improved the test accuracy of wood Poisson's ratio, and its effectiveness has been verified by axial tension method. The asymmetric four point bending method adopts the ±45°strain gauge full bridge measurement method, which is simple and effective to improve the measurement accuracy of wood shear modulus.

Wood–plastic composite (WPC) is a kind of composite material that is made of plastic and wood fiber or wood powder. Because it is mothproof, is resistant to corrosion, and has plasticity, among other advantages, it has been researched and used increasingly in building materials. The flexural property of WPC is an important subject in evaluating its mechanical properties. In this paper, wood–plastic raw materials and processing technology are introduced; the internal and external factors of WPC which affect the flexural properties are analyzed; the different ways of enhancing the bending capacity, including the surface pretreatment, addition of different modifiers (compatibility agent and coupling agent) etc. are summarized; and the methods of operation and strengthening effect are analyzed. This work provides a reference for further research in related fields.

This study investigated the hypothesis that supplementation of methionine (Met) to broiler diets increases muscle growth due to regulation of molecular pathways related to protein synthesis and degradation depending on the Met source. Day-old male Cobb-500 broilers (n = 240) were phase-fed three different wheat-soya bean meal-based basal diets during days 1-10, 11-21 and 22-35. Basal diets (Met- group, Met + Cys concentration 15% below NRC recommendations) were supplemented with 0.10% or 0.40% Met either as DL-Met (DLM) or DL-2-hydroxy-4-(methylthio) butanoic acid (DL-HMTBA) (equimolar comparison). Breast muscle weights were lower in the Met- group compared to all Met-supplemented groups and were lower in broilers supplemented with 0.10% of DL-HMTBA compared to the other groups fed Met-supplemented diets. However, the expression of genes or relative phosphorylation and thus activation state of proteins involved in the somatotropic axis, the mammalian target of rapamycin (mTOR) pathway of protein synthesis, the ubiquitin-proteasome pathway (UPP) and autophagy-lysosomal pathway of protein degradation, the GCN2/eIF2a pathway involved in the inhibition of protein synthesis and in the myostatin-Smad2/3 pathway involved in myogenesis were not affected by Met source. Feeding diets with suboptimum Met + Cys concentrations, however, decreased expression of GHR and IGF1 in liver and muscle and increased that of MURF1 involved in the UPP in the broiler's muscle at day 10 and 21, while that of FOXO and atrogin-1 and FOXO phosphorylation remained unaffected. Additionally, suboptimum dietary Met concentrations increased expression of the autophagy-related genes ATG5 and BECN1 at day 35. Met supplementation neither affected gene expression nor phosphorylation of proteins involved in the GNC2/eIF2a and mTOR pathways. These data indicate that protein synthesis was not affected on the molecular level, while protein degradation was marginally affected by dietary Met dosage.