Wood Members Research Articles

Numerical hygro-thermal analysis of coated wooden bridge members exposed to Northern European climates

This work presents a numerical model to analyse the hygro-thermal behaviour of wooden bridge members. A multi-Fickian hygro-thermal model, previously implemented by some of the authors, is extended ...

Experimental investigation of cross-laminated timber panels with realistic boundary conditions subjected to simulated blast loads

Recent research efforts have established key dynamic characteristics of cross-laminated timber (CLT) panels and developed parameters that are suitable for analysis and design. Despite such effort, no information is available on the critical role connections play in the behaviour of CLT when subjected to blast loads. The current study investigates a total of thirteen full-scale CLT wall panels with varying connection detailing by simulating the blast loading through a shock tube apparatus. The study found that typical connections with end grain screws into wall elements as well as angled double-threaded screws performed poorly and failed prematurely in tension perpendicular to grain. Reinforcing the connection with screws applied on the panel face did not mitigate the brittle failure. It was found that connection types where the wood is bearing on steel angles or directly on other wood members performed well even when under-designed according to the blast design standard. Whereas thin steel angles provided significant energy dissipation in bending of the angle resulting in reduced panel deflection and damage, thicker steel angles provided the energy dissipation through yielding in the screws as well rotational restraint of the panel ends. Using balloon type assemblies provided significant rotational restraint at the panel ends. The study also found that simplified models developed for idealized simply-supported conditions were not adequate to describe the behaviour of the system.

Application of Modern Wood Product Glulam in Timber Frame With Tenon-Mortise Joints and Its Structural Behavior

Tenon-mortise joint is widely used in traditional timber structures around the world. This paper summarizes the results of an experimental study of the structural behavior of tenon-mortise joints made with glulam and CNC technology instead of traditional material and manual work. 30 full-scale tenon-mortise joints were manufactured and tested under monotonic loading, and the effects of dimension, shape, processing error and adhesive were evaluated. It was found that the round rectangular shaped tenon-mortise joints were comparable with traditional joints in terms of structural performance, but were time and labor saving. The variability of the proposed tenon-mortise joints was lower, which would benefit the design value. Applying adhesive between tenon and mortise increased the average stiffness by 4.3 times and average moment capacity by 27.4%, respectively. The gaps between wood members had little effect on the capacity and stiffness in monotonic bending but may influence the energy dissipation ability in cyclic bending. This study showed the feasibility of combining the traditional joinery method with modern wood products and manufacturing technology, which may promote the application of tenon-mortise joints in modern timber structures.

Properties of magnesium oxide boards used as sheathing in exterior walls

Sheathing boards based on magnesium oxide (MgO) became very popular in the Danish market around the year 2010. However, it was realized a few years later that they condensed humidity from ambient air. The leakage from the boards led to severe problems with corrosion of metallic components and moisture uptake and degradation of wooden members. The boards have been banned from use in the Danish market since 2015, while damage cases valuing around 370 million EUR still need to be reconciled [1]. The binder in MgO board is formed by a chemical reaction between MgO and MgCl2. However, MgSO4 is a possible alternative to MgCl2, and such boards may have smaller moisture uptake, to reduce this issue. This paper gives an account of recent activities to compare properties of MgO boards, based on chlorides or sulphates. The investigations comprise: (1) Analysis of elemental composition and crystalline components, (2) Examination in optical microscope and scanning electron microscope, (3) Determination of moisture retention and water vapour permeability, (4) Analysis of chemical composition of leaked salt water from boards, and (5) Visual observation of decomposition and determination of dry mass change after exposure to high humidity.

The fire performance of Cross Laminated Timber beams

Abstract The use of timber as a structural material in multi-storey buildings is often limited due to its combustible nature. The fire performance of the wooden members can be determined through the standard fire tests or, more often, using the calculation procedures recommended by the design codes. The fire resistance of a timber beam can be calculated based on the residual section without taking into account the charred area and the zero strength layer. However, the zero strength layer (d0) it is assumed to be a key parameter of the fire design of timber members. Recent studies show that the utilisation of d0 may be non-conservative in some applications and the simplified design approach method may not properly describe the complex behaviour of the timber members exposed to fire. The paper presents an experimental research on a loaded glulam beam (GL24H) exposed to the standard fire on three faces. Heat transfer and mechanical behaviour of the beam is estimated by simplified reduced cross-section method according to Eurocode 1995-1-2. The experimental charring rates are compared with theoretical and notional values.

Design of envelopes for timber buildings in terms of sustainable development in the low-energy construction

The paper focuses on theoretical analysis of physical determinants affecting construction of envelopes for wood-based structures in the intentions of sustainable development under the current and expected legislation in Slovakia after 2020. It deals with the optimization of model building envelopes in terms of heat loss according to the requirements of the Europe 2020 Strategy and consequently calculates the values of the fire resistance considering Eurocode 5. It assesses the application and fire safety of analysed envelopes in construction of buildings with a combustible construction system, i.e. wood-based buildings intended for housing and accommodation, in accordance with the Slovak legislation. The paper also concentrates on the optimisation of built-in thermo-insulating and facing materials of wooden load-bearing members in the model building envelopes in terms of the environmental burden throughout their life cycle and the impact on the resulting fire resistance. It assesses the possibilities of using building components made from recycled materials in the construction of timber buildings as a full-valued replacement of standard building materials from non-renewable sources.

결로 발생 확률 평가를 통한 현대 신한옥 단열성능 향상 방안 연구

Purpose: In order to supply modern new han-oks having excellent thermal performance, careful review in the process of initial architectural planning step is required. The purpose of this study is to verify design guidelines that can maintain and improve environmental performance though analysis of estimation of condensation probability affected by initial design planning Method: To achieve this goal, measurements were carried out 6 Han-oks situated in OJUK han-ok village which were demonstrated to Gang-neung by taking a infra-red thermography using thermal video system. All evaluation targets are new han-oks style which the same structure and materials are applied. Following are analysis items; the exposure or not of wooden members, the difference according to the space usage, layout of the stationary closet facing directly on the outdoor air or not, influence of distributed arrangement of space using water, planning around the house door facing directly on the outdoor air and so on. Result: It was analyzed that the probability of condensation in case of the exposure of wooden members is higher than that of non exposed installation. Also, it was analyzed that the house door space facing directly the outside air needs introduction of entrance concept space which can minimize the heat loss. In stationary closet planning, it is necessary to consider the position of closet and the range of heating. And, it is judged that a separation planning between the space using water and the unused area is necessary.

Influence of hydrophobation and deliberate thermal bridge on hygrothermal conditions of internally insulated historic solid masonry walls with built-in wood

A large share of the Danish building stock contains historic multi-storey buildings. A considerable energy saving potential exists, achievable through thermal insulation of the façades. Previous research has elucidated problems regarding poor hygrothermal conditions when interior thermal insulation is applied to the façade, but examples exist with positive results.Eight 1 × 2 m solid masonry test walls with wooden members were installed in an insulated container. The hygrothermal implication of applying 100 mm AAC as interior thermal insulation system was investigated with variations including use of hydrophobation and substitution of insulating material with a deliberate thermal bridge.Relative humidity and temperature were monitored in the walls over 2 years in 10 measurement points. The amount of wind driven rain was monitored with rain gauges and calculated from climate station data. The indoor excess of humidity by volume corresponded to the highest indoor climate class for dwellings.Damage models indicated risk of mould growth in the insulation/masonry interface, and risk of wooden decay in the wall plate for the reference and insulated case. Hydrophobation of the exterior surface in tempered cold climate reduced the overall relative humidity, although it increased during winter due to a reduced dry-out potential towards the outside.

Three-Dimensional Combined Elastic-Plastic and Damage Model for Nonlinear Analysis of Wood

AbstractThis paper presents a three-dimensional combined elastic-plastic and damage model for nonlinear analysis of wood members and connections. A strain-driven implicit algorithm was developed ba...

Fracture behavior of wood-steel dowel joints under quasi-static loading

This study analyses a common L-shape configuration formed by wood members and a thick metal plate, duly fastened with steel dowels. Four connecting arrangements were experimentally tested, considering different values of space between dowels and distance to the boundary edge, which allowed measuring the initial stiffness and moment-carrying capacity. A three-dimensional finite element model, including a trapezoidal bilinear cohesive law, was developed to reproduce mixed-mode loading through cohesive zone modelling. Very satisfactory agreements between numerical predictions and experimental results were registered, regarding the full-extension of the load-displacement curves and damage profiles of the joints. In light of these, the model was applied in a larger range of possible combinations of distances to get global trends of the initial stiffness and moment-carrying capacity of these joints.

보물 제 308호 전주 풍남문 주요 부재의 수종 연구

This study is for species identification for each structure member such as Pillar, Bo, Changbang, Dori, Jangyeo, Judu, Donjaju, Chunyeo, Guitle, and Jongdae, of Pungnammun Gate (Treasure 308). Jeonju is the birthplace of Joseon Dynasty and Pungnammun Gate was the southern gate of old Jeonjueupseong which was walled town. Provincial Governor of Koryeo Dynasty, Yu Gyeong Choi built Jeonjubuseong and four gates at all cardinal points in 1388. And the gate was burnt down by Jeongyujaeran (war with Japan in 1597). It was rebuilt by King Yeongjo (Joseon Dynasty) in 1734 and renamed ‘Pungnammun’ after 34 years. It was designated for Treasure 308 for its unique style of architecture and historic values in 1963. In this study, all of wooden structure members were Pinus spp.. This result was matched for the result of major species for wooden building of late Joseon Dynasty. It can be used to complete database for architecture of Castle’s Gate and help for restoration of cultural heritage in the future.

Fungal–copper interactions in wood examined with large field of view synchrotron-based X-ray fluorescence microscopy

ABSTRACTThe goal of this study was to demonstrate how synchrotron-based X-ray fluorescence microscopy (XFM) can be used to better understand the mechanisms of copper tolerance in wood decay fungi. Copper is a major component in commercial wood preservatives as it is toxic to many wood decay fungi. However, certain fungi are copper tolerant and can attack preservative-treated wood, resulting in structural damage to treated wood members. Here we used large-field XFM to visualize six different elements (K, Ca, Mn, Fe, Cu, and Zn) in the mycelia and wood inoculated with four different species of brown rot wood decay fungi. Wood blocks were partially dipped into a solution of copper sulfate, exposed to fungi in malt extract agar petri dish assays for nine weeks, and then imaged and compared to blocks that were partially dipped in water. The blocks were imaged immediately adjacent to an end-matched control that was placed in malt extract agar petri dish assays for 9 weeks, but not exposed to the fungi so that the differences in the elemental distributions could be directly compared. The colonized wood and mycelia were rich in K, Ca, Mn, and Fe; however, the elements and the spatial distribution in the mycelia and wood differed across fungal species. The most interesting results were the maps showing the copper distribution. While three of the four fungi grew on the copper-rich region of the wood, only one species, Fibroporia radiculosa, dramatically reduced the copper concentration in the region of fungal growth.

Dynamic performance of a multi-story traditional timber pagoda

This paper presents a study on the dynamic performance of a multi-story traditional timber pagoda. A shaking table test was conducted with a 1:5 scaled pagoda model and various excitation intensities. Both artificial and recorded earthquake waves were considered. Ambient excitation test before seismic excitations and white noise excitation tests during the intervals of increasing seismic excitations were conducted to detect the fundamental frequencies and damping ratios of the model pagoda. Equivalent story stiffness was evaluated from the measured inter-story load-displacement hysteretic curves and a lumped mass model was established to determine the dynamic properties of the pagoda during strong excitations. It was found that the pagoda model survived all the input earthquake excitations (up to 0.44g in PGA) with only minor damages. The model frequencies detected after increasing earthquake excitations decreased only by 16% while the damping ratio increased from 1.24% to more than 10%, indicating a good seismic resilience of the pagoda. It was also found that the detected frequencies highly relied on the intensity of the excitations (up to 59% in difference), possibly due to the transition between static and sliding frictions amongst wood members and the recoverable looseness of the mortise-tenon joints.

New residential construction building and composite post and beam structure toward global warming mitigation

The construction industry has become one of the major sources of global greenhouse gas (GHG) emissions. Therefore, low carbon buildings have been assigned for reduction of human impact on the environment. The aim of this research is to decrease the CO2 effect from the building sector by eventually proposing a new structure for Malaysian construction with regard to the needs of this industry. Life cycle assessment (LCA) has been performed to analyze the CO2 emission for the Malaysian residential single family house. Seven different materials or structures have been assessed and the result shows that timber prefabricated post and beam is the best choice due to releasing less CO2 emissions to the atmosphere. However, timber has become almost forgotten as building material for house builders in Malaysia in the last four decades. The alternative building scheme has been made by reinforced steel plate into wooden beam and column and timber wall (S8) to improve the building structure deficiency and load bearing while releasing less CO2 emissions in comparison to other buildings. New structure has been designed by steel plate sandwiched between wood members and held together with bolts in beam and post toward decreasing the percentage of improper design and to improve accuracy in the execution of timber structure. Thus, new scheme (S8) could be advised to house maker and government as a new policy to promote the sustainability in construction sector. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 1394–1402, 2018

Moisture conditions of rain-exposed glue-laminated timber members: the effect of different detailing

ABSTRACTIn performance-based durability design, relating the in-use conditions of wooden members to their moisture content is an important step. In the present study, the effects of detail design on the wood moisture content of glulam members are investigated experimentally. The moisture content of glulam members, designed with various connection details and structural protection, was monitored at 18 different measuring points (n = 3) by use of resistance-type moisture sensors for a period of a year. The effects of detail design are studied by comparing the moisture content of various details to that of a freely exposed beam. As expected, the design of the details was clearly reflected by their moisture content. Efforts to protect the wood were favourable in most cases, although only complete shelter kept the moisture content consistently below the level critical for the occurrence of decay. In order to relate the effects of moisture traps to the climate, a three-parameter empirical model was constructed and fitted to the experimental results. The model was able to capture the main features of the measurements and was used in order to characterize the performance of details in terms of their response to weather.

Moisture damage with magnesium oxide boards in Danish facade structures

Magnesium oxide boards have been widely used on facades in Denmark during 2010-2015. However, the magnesium salts absorb humidity from the ambient, and they begin to leak salty water, which is highly corrosive, and leads to moisture and mould problems in wooden members of the structures. MgO-boards were not tested for their hygrothermal function before being used on exterior wall structures, which has had detrimental consequences, such as an expected cost of repair of around 2 billion DKK. Properties for moisture transport and retention properties have been determined and will be shown together with some examples of damaged structures.

A Study on the Compressive Capacity of Wooden Member According to the Reinforcement Ratio of Synthetic Resin

A Study on the Compressive Capacity of Wooden Member According to the Reinforcement Ratio of Synthetic Resin

A Study on the Flexural Capacity of Wooden Member According to the Reinforcement Ratio of Synthetic Resin

A Study on the Flexural Capacity of Wooden Member According to the Reinforcement Ratio of Synthetic Resin

Экспериментальные исследования систем перекрестных балок из деревянных элементов на квадратном плане при изменении динамических и статических нагрузок

Экспериментальные исследования систем перекрестных балок из деревянных элементов на квадратном плане при изменении динамических и статических нагрузок

A theoretical model developed for predicting nail withdrawal load from wood by mechanics

Assembling wood structure involves fastenings in jointing wood members. The strength and stability of wood structure strongly depend on these fastenings that hold wood members together. Nails are one of the most common mechanical fastenings used in wood construction. Wood is a cellular and orthotropic bio-material. For utmost rigidity, strength, and service of wood-nailed joint, the nail requires joint designs adapted to the maximum strength properties of wood along and across the grain. The traditional model for prediction of withdrawal load of nails driven into side grain of wood was purely empirical, which was built on a statistical approach. A model based on the Coulomb’s friction law, the contact pressure of interference fit, Hankinson’s off-axis baring strength, and assumed honeycomb microstructure of wood cell was proposed and validated. When compared with experimental data of nail withdrawal load, this model not only showed better prediction of nail withdrawal load than the traditional model but also bears a physical meaning.