Acoustics Performance Research and Analysis of Light Timber Construction Wall Elements Based on Helmholtz Metasurface

Based on the efficient sound absorption characteristics of Helmholtz resonance structures in the range of medium and low frequency acoustic waves,this paper investigates an effective solution for light timber construction walls with acoustic problems.This study takes the light timber construction wall structure as the research object.Based on the Helmholtz resonance principle,the structure design of the wall unit,impedance tube experiment and COMSOL MULTIPHYSICS simulation calculation were carried out to obtain the change rule of acoustic performance of the Helmholtz resonance wall unit structure.The research results show that the overall stability of sound insulation of the structure is improved,and the frequency range with sound transmission loss more than 50 dB in the experimental group is 640–1600 Hz,while in the control group is 500–906 Hz and 1238–1600 Hz;the sound absorption performance of the structure is obviously better than that of the ordinary structure,especially in the low frequency acoustic wave range of 100–320 Hz,the sound absorption coefficient of the experimental group is more than 0.49,while the sound absorption coefficient of the control group is less than 0.1.It is expected that these results will contribute to the optimization of the acoustic performance of light timber construction walls and have high application and popularization value.

Load behaviors of a prefabricated wood framing house during lifting and transportation

Lifting for handling and flatbed truck transportation to the job site are important processes during manufacture of prefabricated wooden construction units like mini homes and building modules. Significant damage can occur to sections or components of units during these operations. Although damage usually will not impair its structural safety, it is costly to fix and causes the public to perceive prefabricated wooden buildings as low quality products. Field observations and preliminary numerical models for prefabricated units subject to lifting and transportation forces are summarized here. Once fully developed and verified, models will support the creation of damage mitigation strategies centered on structural details indicating how units are to be supported during lifting and transportation.

Urban design considerations in the environmental assessment of vernacular buildings with timber projections(sachnisi):The case of Nicosia's historic center

In this study,the environmental responsiveness of buUt heritage is closely connected with the aspects of building typology and urban canyon geometry.The focus of this study is on two-story adobe buildings with lightweight timber projections,locally called sachnisi,which are located on the first floor,above the pass-through space on the ground floor,locally known as portico.The field study reveals and maps a total of 246 sachnisi projections across the walled city of Nicosia,Cyprus,a typical Mediterranean area.This research is the first systematic attempt to integrate cultural,historical,and environmental factors and the urban-and building-scale environmental characteristics of vernacular heritage.The findings highlight thermal adaptive opportunities and passive cooling strategies,i.e.,natural ventilation,enhanced by aligning the portico axis with the prime wind direction and operating various openings of the sachnisis.The research also demonstrates that the building orientation and the proportions of sachnisis and porticos are insensitive to the street geometry.Thus,functional and morphological parameters(in addition to climatic parameters)are also significant in the configuration of these architectural elements.T he originality and academic contribution of this study lie within the systematic and comprehensive methodology followed,which can be applied to other urban heritage sites.The use of innovative,multidisciplinary methods and tools in heritage studies is also recommended.

Estimating Strength of Finger-jointed Dimension Lumber by Nondestructive Methods

Structural finger-jointed (FJ) lumber was used mainly in structural applications including glue-laminated beams and wooden I-joists and more recently in parallel chord wood trusses. The paper evaluated strength properties of structural FJ lumber by three nondestructive methods (edge-wise bending, longitudinal and transversal vibration) in order to find an alternative to traditional evaluation methods. Lumber was sawn from the logs following a pattern typically used in China to maximize the volume of recovered sawn timbers. After kiln-dried, these rough-sawed lumbers were planned to 4.5 cm thick, 9.0 cm wide and 100cm long. The lumber pieces were assigned to two groups (low-grade and high- grade groups) according to their dynamical modulus of elasticity. FJ lumber was produced by cutting a series of sloping fingers (finger length 20, 25 and 35 mm) on the end of the wood pieces to be joined and interlocking the two pieces. Each finger-jointed lumber with one same finger length had three types: L-L, L-H and H-H. The FJ lumber was nondestructively tested using edge-wise bending, longitudinal and transversal vibration methods. After three methods, tensile and bending strengths of FJ lumber were tested to build dynamical relationships between MOE and strengths. The results showed that dynamic MOEs were good indicators of the static MOE, but both dynamic MOE and static MOE had a bad correlation with tensile strength of finger jointed lumber.