1,721,015 research outputs found
"Long-term performance of LVL-concrete composite beams under service load"
No full textThe long-term behaviour of timber-concrete composite is characterized by the response of its three components (timber, concrete and connection) to load, moisture content, temperature and relative humidity of the
environment. This paper reports results of a 4-years long-term test on three 8m span laminated veneer lumber (LVL)-concrete composite floor beams under service load performed in an indoor, uncontrolled, and unheated environment at the University of Canterbury. The environmental conditions were characterized by either low temperature with high
relative humidity or high temperature with low relative humidity, conditions considered to be reasonably severe and presumably close to service class 3 according to Eurocode 5. The mid-span deflections were extrapolated to the end of service life (50 years) and compared to span/200 deflection limit, which was exceeded by all beams
"Experimental results of fracture energy and fracture toughness of radiata pine laminated veneer lumber (LVL) in mode I (opening)"
No full textPrediction of load-carrying capacity of notched timber beams can be performed using Linear Elastic Fracture Mechanics (LEFM). However, some material properties such as fracture toughness and energy are needed for the analysis. Unfortunately, due to the complexity of the wood at the micro and macroscopic level, little and sometimes unreliable data are available.
Due to the highly anisotropic nature, wood has different fracture properties in three directions. Fortunately, not all of these values are usually required in fracture analysis because the wood tends to crack mainly in grain directions due to the low tensile strength perpendicular to grain. This consideration allows a significant reduction in the number of experiments required for the fracture properties, with considerable saving of resources.
The paper presents the results of an experimental study aimed to investigate the fracture toughness of Radiata Pine Laminated Veneer Lumber (LVL) in mode I (opening). Results are presented for the fracture toughness properties in the grain direction, and include five percentile values and Coefficient of Variation (COV). The influence of the specimen size and moisture content on the fracture toughness is also presented. Numerical analyses by use of ABAQUS software were also carried out and compared with the experimental tests showing good agreement. Obtained experimental results are in the range of experimental values found in literature for wood
“Experimental behaviour of LVL-concrete composite floor beams at strength limit state.”
No full textThis paper reports the outcomes of short-term collapse tests performed on eleven laminated veneer lumber (LVL)–concrete composite floor T-beams. Different variables such as span length (8 and 10 m), connection and concrete types, and design level (well- and under-designed, in terms of connector numbers) were investigated. During 4-point bending tests, mid-span deflection, connection slips and strains were measured. Connection types investigated include triangular and rectangular (150 mm and 300 mm long) notches cut in the timber and reinforced with a coach screw, and modified toothed metal plates pressed on the edge of the LVL joists. All of the beam specimens were designed using the effective bending stiffness or γ -method, in accordance with Annex B of Eurocode 5. The same method was used for an analytical–experimental comparison of the beam’s performance at ultimate (ULS) and serviceability (SLS) limit state.
All well-designed beams provided more than 95% composite action even though there were relatively few connectors (e.g. six 300 mm long notches on the 8 m span beam). The ULS and SLS live load capacity of the beams was found to be approximately 90% of that of a fully composite beam. Correction factors providing a 15% increase for deflection and a 13% reduction of the effective bending stiffness are proposed for calculations using the transformed section method for all well-designed beams, i.e. beams designed using the γ -method according to Annex B of Eurocode 5. Although the γ -method was found to be significantly underestimate the ULS strength, it provided an accurate prediction of the short-term deflection. In terms of the connection type, the 300 mm rectangular notches provided the best performance, with high stiffness and strength beyond the ULS load level, and requiring fewer connectors along the beam. The triangular notch was found to be a viable alternative, with more connectors but was easier and faster to cut than a rectangular notch. Metal plate connectors provide a practical construction possibility, but the beam stiffness was found to rapidly deteriorate beyond the ULS load level
"Long-term performance of LVL-concrete composite beams under service load"
No full textThe long-term behaviour of timber-concrete composite is characterized by the response of its three components (timber, concrete and connection) to load, moisture content, temperature and relative humidity of the
environment. This paper reports results of a 4-years long-term test on three 8m span laminated veneer lumber (LVL)-concrete composite floor beams under service load performed in an indoor, uncontrolled, and unheated environment at the University of Canterbury. The environmental conditions were characterized by either low temperature with high
relative humidity or high temperature with low relative humidity, conditions considered to be reasonably severe and presumably close to service class 3 according to Eurocode 5. The mid-span deflections were extrapolated to the end of service life (50 years) and compared to span/200 deflection limit, which was exceeded by all beams
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