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20 records – page 1 of 2.

Creep Behavior of Laminated Veneer Lumber from Poplar Under Cyclic Humidity Changes

https://research.thinkwood.com/en/permalink/catalogue2480
Year of Publication
2019
Topic
Mechanical Properties
Moisture
Material
LVL (Laminated Veneer Lumber)
Author
Li, Chao
Huang, Yuxiang
Publisher
North Carolina State University
Year of Publication
2019
Country of Publication
United States
Format
Journal Article
Material
LVL (Laminated Veneer Lumber)
Topic
Mechanical Properties
Moisture
Keywords
Mechanosorption Creep
Humidity
Four Point Bending Test
Adsorption
Language
English
Research Status
Complete
Series
BioResources
ISSN
1930-2126
Online Access
Free
Resource Link
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Dimensional Changes of Cross-Laminated Specimens Produced under Different Conditions due to Humidity Variation

https://research.thinkwood.com/en/permalink/catalogue2474
Year of Publication
2019
Topic
Moisture
Material
CLT (Cross-Laminated Timber)

Durability of Structural Lumber Products after Exposure at 82C and 80% Relative Humidity

https://research.thinkwood.com/en/permalink/catalogue784
Year of Publication
2005
Topic
Mechanical Properties
Moisture
Material
LSL (Laminated Strand Lumber)
LVL (Laminated Veneer Lumber)
Solid-sawn Heavy Timber
Author
Green, David
Evans, James
Hatfield, Cherilyn
Byrd, Pamela
Organization
Forest Products Laboratory
Year of Publication
2005
Country of Publication
United States
Format
Report
Material
LSL (Laminated Strand Lumber)
LVL (Laminated Veneer Lumber)
Solid-sawn Heavy Timber
Topic
Mechanical Properties
Moisture
Keywords
Aspen
Douglas-Fir
Modulus of Elasticity
Modulus of Rupture
Southern Pine
Poplar
Relative Humidity
SPF
Temperature
Flexural Properties
Language
English
Research Status
Complete
Summary
Solid-sawn lumber (Douglas-fir, southern pine, Spruce– Pine–Fir, and yellow-poplar), laminated veneer lumber (Douglas-fir, southern pine, and yellow-poplar), and laminated strand lumber (aspen and yellow-poplar) were heated continuously at 82°C (180°F) and 80% relative humidity (RH) for periods of up to 24 months. The lumber was then reconditioned to room temperature at 20% RH and tested in edgewise bending. Little reduction occurred in modulus of elasticity (MOE) of solid-sawn lumber, but MOE of composite lumber products was somewhat reduced. Modulus of rupture (MOR) of solid-sawn lumber was reduced by up to 50% after 24 months exposure. Reductions in MOR of up to 61% were found for laminated veneer lumber and laminated strand lumber after 12 months exposure. A limited scope study indicated that the results for laminated veneer lumber in edgewise bending are also applicable to flatwise bending. Comparison with previous results at 82°C (180°F)/25% RH and at 66°C (150°F)/20% RH indicate that differences in the permanent effect of temperature on MOR between species of solid-sawn lumber and between solid-sawn lumber and composite lumber products are greater at high humidity levels than at low humidity levels. This report also describes the experimental design of a program to evaluate the permanent effect of temperature on flexural properties of structural lumber, with reference to previous publications on the immediate effect of temperature and the effect of moisture content on lumber properties.
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Effect of Moisture Induced Stresses on the Mechanical Performance of Glulam Beams of Vihantasalmi Bridge

https://research.thinkwood.com/en/permalink/catalogue1609
Year of Publication
2016
Topic
Moisture
Serviceability
Material
Glulam (Glue-Laminated Timber)
Application
Bridges and Spans
Author
Hradil, Petr
Fortino, Stefania
Salokangas, Lauri
Musci, Alessandro
Metelli, Giovanni
Year of Publication
2016
Country of Publication
Austria
Format
Conference Paper
Material
Glulam (Glue-Laminated Timber)
Application
Bridges and Spans
Topic
Moisture
Serviceability
Keywords
Moisture Induced Stresses
Finland
Moisture Gradients
Moisture Content
Hygrothermal
Multi-Fickian Theory
Relative Humidity
Temperature
Eurocode 5
Language
English
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 2159-2167
Summary
The present paper deals with the effect of moisture induced stresses (MIS) on the mechanical performance of a glulam beam of Vihantasalmi Bridge in Finland. MIS caused by high moisture gradients in a cross section of the glulam beam are calculated by a hygro-thermal multi-Fickian model for evaluation of moisture content, relative humidity and temperature in wood that is sequentially coupled with an orthotropic-viscoelasticmechanosorptive model for calculation of wood stresses. Both models, already developed in Abaqus FEM code by some of the authors in their previous works, had to be modified for the Nordic climate. The obtained levels of MIS are then compared to the Eurocode 5 design resistances. The study aims at providing suggestions to future developments of Eurocode 5 for the correct evaluation of the influence of moisture content on service life in timber bridge elements.
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Free
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Effect of Reserve Air-Drying of Korean Pine Heavy Timbers on High-Temperature and Low-Humidity Drying Characteristics

https://research.thinkwood.com/en/permalink/catalogue1506
Year of Publication
2014
Topic
Moisture
Material
Solid-sawn Heavy Timber
Author
Lee, Chang-Jin
Lee, Nam-Ho
Park, Moon-Jae
Park, Joo-Saeng
Eom, Chang-Deuk
Publisher
The Korean Society of Wood Science Technology
Year of Publication
2014
Country of Publication
Korea
Format
Journal Article
Material
Solid-sawn Heavy Timber
Topic
Moisture
Keywords
Moisture Content
Temperature
Humidity
Pine
Air Drying
Shrinkage
Internal Checks
Twist
Case Hardening
Language
Korean
Research Status
Complete
Series
Journal of the Korean Wood Science and Technology
Summary
The pre-air-drying of Korean pine before the high-temperature and low-humidity drying was shown to be effective in uniform moisture content distribution and prevention of surface check. Our results suggest that initial moisture content of the timber also plays important role in high-temperature and low-humidity drying method. The pre-air-drying also helps in the reduction of surface checks in Korean pine when compared to the Korean pine dried by only high-temperature and low-humidity. End-coating was not effective in the prevention of twist, shrinkage, case hardening and internal checks. The pre-air-drying reduces the internal tension stresses which occur during high-temperature and low-humidity drying thus decreasing case hardening and also preventing internal checks. The pre-air-drying decreases the moisture content and causes shrinkage which leads to increased twist in the Korean pine.
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Free
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Experimental Investigation on the Long-Term Behaviour of Prefabricated Timber-Concrete Composite Beams with Steel Plate Connections

https://research.thinkwood.com/en/permalink/catalogue2741
Year of Publication
2021
Topic
Connections
Serviceability
Material
Timber-Concrete Composite
Application
Beams
Author
Shi, Benkai
Liu, Weiqing
Yang, Huifeng
Publisher
ScienceDirect
Year of Publication
2021
Format
Journal Article
Material
Timber-Concrete Composite
Application
Beams
Topic
Connections
Serviceability
Keywords
TCC
Prefabrication
Steel Plate
Long-term Behaviour
Interface Slip
Loading
Shear Connections
Deflection
Temperature
Humidity
Language
English
Research Status
Complete
Series
Construction and Building Materials
Summary
This paper presents the results of long-term experiments performed on three timber-concrete composite (TCC) beams. An innovative fabricated steel plate connection system, which consists of screws and steel plates embedded in concrete slabs, was adopted in the TCC beam specimens. The adopted shear connection can provide dry-type connection for TCC beams. Steel plates were embedded in concrete slabs while the concrete slab was constructed in factories. The timber beam and concrete slab can be assembled together using screws at the construction site. In this experimental programme, the beam specimens were subjected to constant loading for 613 days in indoor uncontrolled environments. The influence of long-term loading levels and the number of shear connections on the long-term performance of TCC beams was investigated and discussed. The mid-span deflection, timber strain, and interface relative slip at the positions of both connections and beam-ends were recorded throughout the long-term tests. It was found the long-term deflection of the TCC beam increased by approximately 60% while the long-term loads were doubled. Under the influence of the variable temperature and humidity, the TCC specimens with 8 shear connections showed slighter fluctuations compared with the TCC beam with 6 shear connections. In the 613-day observation period, the maximum deflection increment recorded was 6.56 mm for the specimen with eight shear connections and 20% loading level. A rheological model consisting of two Kelvin bodies was employed to fit the curves of creep coefficients. The final deflections predicted of all specimens at the end of 50-year service life were 2.1~2.7 times the initial deflections caused by the applied loads. All beam specimens showed relative small increments in mid-span deflection, strain and relative slip over time without any degradations, demonstrating the excellent long-term performance of TCC beams using the innovative steel plate connection system, which is also easily fabricated.
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Free
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External Thermal Insulation Composite Systems in Solid Timber Construction

https://research.thinkwood.com/en/permalink/catalogue1639
Year of Publication
2016
Topic
Serviceability
Moisture
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Günther, Simon
Ringhofer, Andreas
Schickhofer, Gerhard
Year of Publication
2016
Country of Publication
Austria
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Serviceability
Moisture
Keywords
External Thermal Insulation Composite Systems
Hygrothermal
Long-term
Monitoring
Temperature
Relative Humidity
Moisture Content
Language
English
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 3169-3178
Summary
External thermal insulation composite systems (ETICS) combined with cross laminated timber (CLT) reveal useful exterior wall constructions, which meet the requirements for sustainability, serviceability and durability of modern buildings efficiently. Associated thermal insulation and moisture protection requirements are essential design criteria to be considered in the planning process. In light of the European legal regulation concerning ETICS, our paper deals with the hygrothermal behavior of an existing exterior wall construction in solid timber construction with ETICS, experimentally determined by means of long-term monitoring situated in the residential project "_massive_living" (Graz, AT). Based on obtained data of temperature and rel. humidity for a period of two years, we not only evaluated building physics aspects concerning the suitability of the structure, but also derived the time depending course of the essential parameter "moisture content" for selected layers of the CLT element. In addition, corresponding data is compared with results gained from a hygrothermal simulation. Further investigation then was carried out determining the hygrical impact on the timber component by changing insulation material. Therefore, the hygrothermal behavior of commonly applied ETICS in combination with CLT as base material was simulated. Finally, resulting bandwidths of moisture content in dependence of the applied ETICS are shown and discussed.
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Free
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Field Measurement of Vertical Movement and Roof Moisture Performance of the Wood Innovation and Design Centre

https://research.thinkwood.com/en/permalink/catalogue1182
Year of Publication
2018
Topic
Serviceability
Moisture
Material
CLT (Cross-Laminated Timber)
Glulam (Glue-Laminated Timber)
PSL (Parallel Strand Lumber)
Application
Wood Building Systems
Roofs
Author
Wang, Jieying
Organization
FPInnovations
Year of Publication
2018
Country of Publication
Canada
Format
Report
Material
CLT (Cross-Laminated Timber)
Glulam (Glue-Laminated Timber)
PSL (Parallel Strand Lumber)
Application
Wood Building Systems
Roofs
Topic
Serviceability
Moisture
Keywords
Vertical Movement
Moisture Content
Temperature
Relative Humidity
Monitoring
Language
English
Research Status
Complete
Summary
Two of the major topics of interest to those designing taller and larger wood buildings are the susceptibility to differential movement and the likelihood of mass timber components drying too slowly after they become wet during construction. The Wood Innovation and Design Centre in Prince George, British Columbia provides a unique opportunity for non-destructive testing and monitoring to measure the ‘As Built’ performance of a relatively tall mass timber building. Field measurements also provide performance data to support regulatory and market acceptance of wood-based systems in tall and large buildings. This report covers vertical movement and roof moisture performance measured from this building for about three and a half years, with sensors installed during the construction. The report first describes instrumentation. The locations selected for installing displacement sensors for measuring vertical movement comprised of the following: glued-laminated timber (glulam) columns together with cross-laminated timber (CLT) floors on three lower floors; a glulam column together with a parallel strand lumber (PSL) transfer beam on the first floor; and a CLT shear wall of the core structure on each floor from the second up to the top floor. Sensors were also installed to measure environmental conditions (temperature and relative humidity) in the immediate vicinity of the components being monitored. In addition, six locations in the timber roof were selected and instrumented for measuring moisture changes in the wood as well as the local environmental conditions. Most sensors went into operation in the middle of March 2014, after the roof sheathing was installed.
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Free
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Field Measurement of Vertical Movement and Roof Moisture Performance of the Wood Innovation and Design Centre

https://research.thinkwood.com/en/permalink/catalogue1638
Year of Publication
2016
Topic
Moisture
Serviceability
Material
CLT (Cross-Laminated Timber)
Glulam (Glue-Laminated Timber)
PSL (Parallel Strand Lumber)
Application
Roofs
Wood Building Systems
Author
Wang, Jieying
Karsh, Eric
Finch, Graham
Chen, Mingyuk
Year of Publication
2016
Country of Publication
Austria
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Glulam (Glue-Laminated Timber)
PSL (Parallel Strand Lumber)
Application
Roofs
Wood Building Systems
Topic
Moisture
Serviceability
Keywords
Moisture Content
Vertical Movement
Temperature
Relative Humidity
Monitoring
Language
English
Conference
World Conference on Timber Engineering
Research Status
Complete
Notes
August 22-25, 2016, Vienna, Austria p. 3152-3160
Summary
The Wood Innovation and Design Centre (WIDC) in Prince George, British Columbia, with 6 tall storeys and a total height of 29.5 m, provided a unique opportunity for non-destructive testing and monitoring to measure the ‘As Built’ performance of a relatively tall mass timber building. The mass timber structural system consists of glulam columns and beams with cross laminated timber (CLT) floor plates and shear walls. Vertical movement of selected glulam columns and CLT walls and the moisture content of the innovative mass timber roof were monitored as these components are unique to mass timber buildings. Indoor temperature and relative humidity conditions were also measured. The mass timber CLT and glulam elements are susceptible to longer-term differential movement as they slowly dry after manufacturing and construction. The paper describes instrumentation and discusses the measurement results for two years following the topping out of the structure. The monitoring indicated that the wood inside the building could reach a moisture content (MC) close to 4% in the winter in this cold climate, from an initial MC of around 13% during construction. Glulam columns were dimensionally stable in the longitudinal direction given the MC changes and loading conditions. With a height of over 5 m and 6 m, respectively, two glulam columns directly measured by sensors each showed vertical movement below 3 mm (i.e., 0.04%). The cumulative shortening of the six glulam columns along the height of the columns (24.5 m) is expected to be approximately 11 mm. This did not take into consideration any potential settlement or deformation at connections between glulam columns, or effects of reduced loads on the top two unoccupied floors. The CLT wall panels were also dimensionally stable along the height of the building, with cumulative vertical shrinkage of about 19 mm (i.e., 0.07%) from Level 1 to Level 6. In contrast, the 5-ply CLT floor slabs made up of wood in radial and tangential grain shrank in thickness by about 5 mm (3.0%) on average. With regards to the performance of the mass timber roof, the CLT roof panels started out dry and remained dry due to the robust assembly design and the dry indoor conditions. In one area the plywood roof sheathing was initially wetted by the application of a concrete topping below a piece of mechanical equipment, it was able to dry to the interior within a few months. Overall the monitoring study showed that the differential movement occurring among the glulam columns and the CLT wall was small and the mass timber roof design had good drying performance.
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Free
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Hygrothermal Conditions in Cross Laminated Timber (CLT) Dwellings

https://research.thinkwood.com/en/permalink/catalogue2705
Year of Publication
2020
Topic
Moisture
Energy Performance
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Author
Tingstveit, Merethe
Nielsen, Henrik
Risholt, Birgit
Year of Publication
2020
Format
Conference Paper
Material
CLT (Cross-Laminated Timber)
Application
Wood Building Systems
Topic
Moisture
Energy Performance
Keywords
Hygrothermal
Low-Rise
Residential
Moisture Content
Relative Humidity
Indoor Air Temperature
Language
English
Conference
Nordic Symposium on Building Physics
Research Status
Complete
Summary
The use of CLT has been increasing the last decade, and a subsequently focus on documentation of the accompanying indoor climate and exposed wooden surfaces on human well-being. This study presents the results of a measurement campaign conducted over one year of a CLT apartment building in Grimstad, Norway. The apartment building consists of three floors with 35 apartments and comply with the Norwegian passive house standard and energy grade A. Measurements of the relative humidity (RH), indoor air temperature and wood moisture content (MC) were performed in the exposed CLT spruce panels in three apartments in two different floors. The results from the three apartments show a relatively small variation in the MC values regardless the residents behavior measured as RH variation through a complete year. Selected periods from a cold period (winter) and a warm period (summer) show the variation in relative humidity (RH) and moisture content in the CLT element. However, results from control measurements showed higher MC values. The gap between the measurements and methods are discussed.
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Free
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20 records – page 1 of 2.