Lightweight Wood Research Articles

Effect of incorporation of lignin as bio-polyol on the performance of rigid lightweight wood\u2013polyurethane composite foams

Density reduction has become a topical issue in wood composite materials for application in building and furniture. In this study, lightweight wood–polyurethane (W–PU) composite foams with the addition of 30 wt% wood particles were prepared. Industrial kraft lignin was used as bio-polyol to substitute partial petroleum-based diethylene glycol (DEG) to synthesize rigid W–PU foams. The effect of varying lignin contents (5, 10, 15 and 20 wt% based on DEG mass) on the reactivity, morphology, density, compressive properties, water absorption and thermal stability of the foams was evaluated. Fourier transform infrared (FTIR) analysis confirmed the formation of characteristic urethane linkages in all the foam samples. With the incorporation of lignin, the foam cellular shape became irregular with formation of large cells. W–PU foams exhibited poor cellular structures with a larger number of open cells. The density of W–PU foams increased from 47 to 96 kg/m3 as the lignin content increased from 0 to 20%. Although the foam reactivity was decreased by the incorporation of lignin, both the compressive strength and modulus were increased upon the incorporation of lignin. Furthermore, the specific compressive strength and modulus of W–PU foams increased by 55% and 48% with lignin content increasing from 0 to 20%, and the 20-day water absorption decreased by 38%. Thermal gravimetric analysis showed that the incorporation of lignin did not significantly affect the thermal degradation behaviour of foam, but it rather increased the mass of char residue. This study provides a promising method for value-added utilization of technical lignin in W–PU lightweight composites.

Artificial Neural Network to Predict the Compressive Strength of Semilightweight Concrete Containing Ultrafine GGBS

Abstract Design strength is usually determined after a 28-day curing period as per codal provisions. The prediction of compressive strength before curing reduces waiting time and expedites regular construction activity. The aim of this study is to develop a neural network model to predict the 28-day compressive strength of semilightweight concrete (sLWC) containing ultrafine ground granulated blast-furnace slag (UFGGBS). In this investigation, a novel lightweight coarse aggregate that is made up of wood ash was used to prepare sLWC. Six input parameters, such as cement, UFGGBS as cement replacement, lightweight wood ash pellets as coarse aggregate, fine aggregate, water content, and superplasticizer, were used to train the model. The 28-day compressive strength was taken as an output parameter. A total of 384 data was collected from 24 sLWC mixes, each containing 16 specimens, and trained in an artificial neural network (ANN) using a feedforward-backpropagation model. Trained data were validated with a set of tested data. The correlation coefficient R2 values for trained and tested data were 0.932 and 0.917, respectively, with least errors. The study concluded that ANN was a reliable and fast tool for predicting the compressive strength of sLWC. It also efficiently reduced cost and time.

Enhanced mechanical and thermal properties of hollow wood composites filled with phase-change material

To obtain lightweight wood building materials with good thermal insulation, energy-saving properties, and satisfying mechanical properties, low-density fiberboard and hollow wood composites (HWC) embedded polyvinyl chloride tubes were fabricated by hot-pressing. Polyethylene glycol was used as the phase-change material to fill polyvinyl chloride tubes and obtain phase-change hollow wood composite (PHWC). The physical and mechanical properties of HWC and PHWC were tested, and their thermal properties were analyzed and simulated. The results showed that the thermal conductivities of low-density fiberboard, HWC, and PHWC ranged from 0.06 to 0.07 W/(m·K), indicating they had sufficient physical and mechanical properties to be used as thermal insulation building materials. The combination of series and parallel models accurately predicted the thermal conductivity of HWC and PHWC, whose structures were similar to a series structure. The addition of polyethylene glycol into HWC allowed the PHWC to store latent heat and reduce indoor temperature fluctuations. Heat transfer simulations showed that when used as a non-structural building wall material, the PHWC wall had a better energy efficiency compared with a concrete wall. Thus, PHWC has potential applications as thermal insulation and phase-change building material.

Lightweight, Anisotropic, Compressible, and Thermally-Insulating Wood Aerogels with Aligned Cellulose Fibers

The growing demand for lightweight, renewable, and excellent thermal insulation materials has fueled a search for high performance biomass materials with good mechanical compressibility and ultralow thermal conductivity. We propose a fabrication method for making a lightweight, anisotropic, and compressible wood aerogel with aligned cellulose fibers by a simple chemical treatment. The wood aerogel was mainly composed of highly aligned cellulose fibers with a relative crystallinity of 77.1%. The aerogel exhibits a low density of 32.18 mg/cm3 and a high specific surface area of 31.68 m2/g due to the removal of lignin and hemicellulose from the wood. Moreover, the multilayer structure of the aerogel was formed under the restriction of wood rays. Combined with a nanoscale pore, the aerogel presents good compressibility and an ultralow thermal conductivity of 0.033 W/mK. These results show that the wood aerogel is a high quality biomass material with a potential function of thermal insulation through optimizing structures.

Prediction evaluating of moisture problems in light-weight wood structure: Perspectives on regional climates and building materials

Most of the construction techniques and materials used in Korean wooden houses are based on those used in North America and Europe. In order to prevent moisture problems in wooden houses, it is necessary to evaluate the hygrothermal behavior of the building envelope. In this study, the hygrothermal performance of light-weight wood structures was analyzed using the WUFI simulation program in 20 regions of Korea. As the results, since there is a clear distinction between summer and winter in Korea, the location of the vapor resistance materials should be considered, and the 2 × 6 structure was found to be the most stable for installing the vapor retarder and the weather-resistive barrier on the inside and outside of a wall. In addition, the water stability of the light-weight wood structure was affected by the hygrothermal climatic conditions in each region. The OSB surface is influenced by the amount of driving rain, but the vapor-retarder layer is more significantly affected by summer heavy rain. Therefore, consideration of the regional climate conditions, the hygrothermal properties of building materials, and the location of building materials are needed to ensure the water stability of the walls in the light-weight wood structures.

SOPO BATAK TOBA RESILIENCE TECTONICS TOWARD EARTHQUAKE STUDY OBJECT: SOPO NAGARI SIHOTANG

Abstract- Sopo is a granary house in traditional Batak Toba architecture. Sopo is important for Batak Toba community because it serves as a place to store rice which is the source of life. Nowadays sopo is harder to find than ruma. Most of the sopo has transformed into Batak Toba house and uses as a residence. Sopo is located in Lake Toba, North Sumatra, which is prone to earthquakes. Sopo Nagari Sihotang was built in the 1920s and has experienced many earthquakes, now the sopo still survive without any structural damage. The resistance of the sopo over the years proves the sopo resilience to earthquakes. From the evidence of resilience to earthquake, its interesting to investigate the tectonics of this sopo. The purpose of the research is to understand the tectonic of Sopo Nagari Sihotang that resilience to earthquake and find local wisdom in facing earthquake disaster.The research used descriptive method with qualitative approach by describing the existing state of Sopo Nagari Sihotang and comparing it with tectonic theory and earthquake resistant structure. The sopo’s data were collected by field observation and literature study. The data are grouped into four parts, namely construction, detail, space, and ornaments that become points for analysis of tectonics. Tectonic analysis is associated with the theory of earthquake resistant structures to find out what makes tectonic of the sopo resilient to earthquakes.The result is the tectonic resilience of the Sopo Nagari Sihotang to earthquakes are found in the tectonics construction in the use of materials; tectonics detail on vertical structures and horizontal structures; and tectonics space at the story height – the activity, the spatial form – the building hape, the spatial form - the structure, and the activity - the structure. The tectonic resilience of Sopo Nagari Sihotang to earthquakes is not found in the tectonics construction and tectonics ornament. The local wisdom which are the main factors make the sopo resilience to earthquake are found on, the tectonics detail of the sopo post-batu ojahan can retain the sopo by relying on the frictional force resulting from self-weight of the sopo; the tectonics detail of the sopo post-ransang can bind every sopo posts; the use of lightweight wood materials thus reducing inertia forces. Key Words: resilience, tectonics, sopo, earthquake, Batak Toba

Influence of between-joists bridging elements on static and dynamic response of wood joisted floors

Excessive vertical vibration of lightweight floors caused by walking or similar activities can be annoying to building occupants. Previous studies have shown that the vibrational performance of floors having wood joists is enhanced by installing one or more lines of bridging elements that form transverse spines in the across-span direction. This paper presents an experimental study that defined relationships between the effective flexural rigidity of such spines and response characteristics of wood joisted floors. Behaviors of spines having both normal and special types of bridging elements were investigated, with the special types of elements able to create a broad range of spine flexural rigidities. It was found that all types of transverse bridging spines have a small influence on fundamental natural frequency but can increase higher order modal frequencies considerably. Relatively stiff types of transverse bridging spines reduced static deflections caused by concentrated gravity forces considerably. An experimental method is presented for quantifying effective flexural rigidities of transverse bridging spines. Suggestions are made concerning application of the research findings in vibration serviceability design of lightweight wood joisted floors.

RE-ESTABLISHING AMERICAN CHESTNUT ON MINED LANDS IN THE APPALACHIAN COALFIELDS

INTRODUCTION American chestnut (Castanea dentata) was formerly a major component of forests throughout the Appalachian coalfield and beyond. Chestnut's strong, lightweight wood was naturally rot-re...

Compression behaviors of wood-based lattice sandwich structures

To obtain a lightweight and high-strength wood sandwich structure, a wooden lattice sandwich cell element was designed in combination with a pyramid-type structure. After inserting glue to prepare the cell unit, the influence of panel thickness and core diameter on the unit cell force was analyzed and compared under the condition of flat pressure. Under the condition of flat pressure, the specific strength of the unit cell was higher than that of the specific strength of the composition material, and the unit cell may be regarded as a structure with high specific strength. Theoretical predictions, simulation analysis, and experimental tests demonstrated that the structure compressive capacity depended on the diameter of the core when the core length was set. The larger the diameter of the core is, the stronger the bearing capacity of the unit cell will be. When the diameter of the core is constant, the longer the core length is, the weaker the bearing capacity of the unit cell will be. The simulation analysis was in agreement with the experimental test results, indicating that the destruction of the structure was mainly caused by the failure of the core.

Moisture-related distortion and damage of lightweight wood panels—experimental and numerical study

This study was conducted to increase the knowledge of moisture-related distortion and damage in the field of wood-based lightweight panels. By increasing the possibilities of predicting moisture-re ...

Design of log house for agro-tourism from ain wood

The presence of log house in agro-tourism is one of type of attraction to the tourists to come for agro-tourism. The tourists come for tourism and they stay in log house. The main advantage of a log house is a healthy living environment. The log house is made up with the locally available wood or light weight wood. The demand for wooden products is continuously increasing day by day. Wood is exposed to both periodic water absorption and desorption process. Understanding water absorption and desorption in wood are of practical importance since they also affect the mechanical properties of the product. In residential building and in industrial application some of the components are often wood (Ostman, 1985). For the purpose of the study, Agro-tourism for farmers is considered as a range of activities, services and amenities provided by farmers and rural people to attract tourist to their area in order to generate extra income for their businesses. Agro-tourism for tourists is considered as anything that connects tourists with the heritage, natural resource or culinary experiences unique to the agricultural industry or a specific region of the country's rural areas. The designed log house was safe from different loads point of view.

Lateral Loading Performance of Lightweight Glubam Shear Walls

A new type of lightweight shear walls made with a laminated bamboo (glubam) stud frame and ply-bamboo sheathing panels is introduced in this paper. The lateral loading experiments of such shear walls and corresponding similar lightweight wood shear walls with three different panel-frame nailing connections and two thicknesses of sheathing panels were performed, in accordance with international standards. Test results demonstrate that the lightweight glubam shear walls have similar performance as conventional lightweight wood-frame shear walls, with higher initial stiffness and peak load, but less ductility. An increase in nail diameter can improve the load-bearing capacity of the shear walls until the failure mode of panel-frame connection changes from yielding of the nails to pull-through of nails from the ply-bamboo panels. Increased panel thickness can increase the bearing capacity and deformability of the shear walls when the failure pattern of panel-frame connection changes from panel failure to nail yielding. A new uplift hold-down device and improved design of edge studs were used to increase the ductile performance of glubam shear walls.

Evaluation of Out-of-Plane Wall Anchorage Force Provisions in Buildings with Rigid Walls and Flexible Roof Diaphragms

Heavy concrete and masonry walled buildings with lightweight steel or wood flexible roof diaphragms are a common type of construction in North America. Failures of the out-of-plane wall anchorage to these roof systems and the resulting partial roof collapses during past earthquakes have led to repeated revisions to the seismic design provisions in the U.S. model building codes. However, the force levels considered in the current design provisions have remained largely unchanged since their introduction in the 1997 Uniform Building Code, and these provisions have not been fully tested by strong ground motions in the field. Using a two dimensional numerical framework, a series of nonlinear time history dynamic analyses on various building archetypes were conducted to evaluate the validity of the current wall anchorage design force levels. The results of this study reveal that the current wall anchorage design forces are generally appropriate, but with some very significant exceptions.

국내 목조주택 표준모델의 난방에너지성능 분석 - 농어촌 표준주택과 저에너지 표준주택을 대상으로 -

국내 목조주택 표준모델의 난방에너지성능 분석 - 농어촌 표준주택과 저에너지 표준주택을 대상으로 -

Control of Low-Cost Customizable Robot Arm Actuated by Elastic Tendons

[abstFig src='/00280004/09.jpg' width='300' text='Elastic tendon driven robot arm' ] This paper presents a low-cost, lightweight robot arm with very low stiffness actuated by elastic tendons. To simplify the string tension control, a new winding device was developed. Small pulleys were incorporated into the winding drum to reduce friction between the tendon and the drum. A marionette-style two-link robot arm with compliant joints was prototyped. Because the arm and winding devices were separate from each other, the cost and weight of the robot were reduced. The links are made with lightweight wood connected by simple shaft joints. The robot design can be easily modified by the user because the mechanical parts do not require high machining accuracy. This robot is intended for implementation in tasks that do not require high positioning accuracy using a simple force control under environmental constraints. Because of its low stiffness, simple and sensor-less force control can be easily implemented based on the relationship between forces under static conditions. The proposed simple control method was evaluated experimentally by conducting position, static force, and hybrid position/force control tasks and was shown to perform well. The results also demonstrate that employing additional sensors, such as a camera, improves the accuracy of the controller.

실측데이터를 이용한 에너지제로주택의 연간 에너지성능평가

Purpose: In this study, we evaluate the annual energy performance of the detached house which was designed with the aim of zero energy. Method: The experimental house which was constructed in Gonju Chungnam in 2013, is the single family detached house of light weight wood frame with <TEX>$100m^2$</TEX> of heating area. Thermal transmittance of roof (by ISO 10211) and building external walls are designed as <TEX>$0.10W/m^2K$</TEX> and <TEX>$0.14W/m^2$</TEX> respectively and low-e coating vacuum window glazing with PVC frame was installed. Also grid connected PV system and natural-circulation solar water heater was applied and 6kWp capacity of photovoltaic module was installed in pitched roof and <TEX>$5m^2$</TEX> of solar collector in vertical wall facing the south. We analyzed the 2014 annual data of the detached house in which residents were actually living, measured though web-based remote monitoring system. Result: First, as a result, total annual energy consumption and energy production (PV generation and solar hot water) are 7,919kWh and 7,689kWh respectively and the rate of energy independence is 97.1% which is almost close to the zero energy. Second, plug load and hot water of energy consumption by category showed the highest numbers each with 33% and 31%, with following space heating 24%, electric cooker 8%, lighting 3% in order. Hot water supply is relatively higher than space heating because high insulation makes it decreased.

Optically Transparent Wood from a Nanoporous Cellulosic Template: Combining Functional and Structural Performance.

Optically transparent wood (TW) with transmittance as high as 85% and haze of 71% was obtained using a delignified nanoporous wood template. The template was prepared by removing the light-absorbing lignin component, creating nanoporosity in the wood cell wall. Transparent wood was prepared by successful impregnation of lumen and the nanoscale cellulose fiber network in the cell wall with refractive-index-matched prepolymerized methyl methacrylate (MMA). During the process, the hierarchical wood structure was preserved. Optical properties of TW are tunable by changing the cellulose volume fraction. The synergy between wood and PMMA was observed for mechanical properties. Lightweight and strong transparent wood is a potential candidate for lightweight low-cost, light-transmitting buildings and transparent solar cell windows.

Comparisons of impact and airborne sound isolation among cross laminated timber, heavy-timber mill buildings, concrete, and light weight wood frame floor/ceiling assemblies

While laboratory measurements of the Impact Sound Pressure Level (ISPL) and Transmission Loss (TL) of concrete and lightweight wood-frame constructions are well understood, not much laboratory research has been conducted into the acoustical performance of CLT and heavy-timber mill buildings. Recent work on the performance of these wood based floor/ceilings has been presented at other conferences. This paper will review that previously published research for both the bare assemblies and assemblies that include resilient elements. These resilient elements include recycled rubber floor underlayment and sound isolation clip systems. This paper will then compare the performance of these assemblies to each other and to more common concrete and lightweight wood frame floor/ceiling assemblies. The analysis will also include the comparable strengths and weaknesses of each structural system along with the effectiveness of the various acoustical isolation techniques and their effectiveness on each of various floor ceiling assembly. It will be shown that the acoustical isolation techniques will perform differently on the various floor/ceiling assemblies.

Fire Resistance of Wood Truss Floor Assemblies

This paper discusses the factors that affect the fire resistance performance of lightweight wood frame unrestrained floor assemblies protected with Type X gypsum board ceiling finishes. Twenty-two fire resistance experiments were conducted on full-scale load-bearing wood joist floor assemblies using the ULC standard fire exposure time–temperature curve that is similar to ASTM E119 standard. Parameters investigated in this study include the effects of gypsum board screws spacing from board edges, insulation installation, insulation type, joist spacing for assemblies with gypsum board attached to resilient channels, joist depth, resilient channel installation, resilient channel spacing, sub-floor topping, number of sub-floor layers, and load magnitude. The impact of these parameters on the fire resistance of wood joist frame floor assemblies is discussed. The fire resistance of wood frame floors appears essentially to be governed by the gypsum board screw spacing from the board edges and the type of insulation in assemblies with one layer of gypsum board and by the resilient channel spacing and the gypsum board screw spacing from the board edges in assemblies with two layers of gypsum board. The effects of other parameters in assemblies with two layers of gypsum board such as the joist spacing where the gypsum boards are attached to resilient channels, installation of resilient channels, insulation installation, insulation type, adding gyp-crete topping above the sub-floor and number of sub-floor layers on fire resistance are relatively insignificant.

Dynamic Behavior of Sandwich Beams with Different Cores

The nonlinear dynamic behaviour of sandwich beams with different cores under transverse cycling loads is investigated in this paper. Based on Euler-Bernoulli beam theory, the second-order nonlinear ordinary differential equation of the sandwich beams with different cores is established by applying Hamilton’s principle and Galerkin method. The effects of the cores of metal foam and lightweight wood and porous metal fiber as well as pyramid lattice structure on the dynamic behaviour are studied through numerical simulations. It is shown that the dynamic behaviour of sandwich beams is not solely determined by and