Conference Paper

Bending properties of Innovative Multi-Layer Composite Laminated Panels

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Abstract

An innovative multi-layer (3 and 5) composite laminated panel (CLP) with various layups were developed using sawn lumber and structural composite lumber (SCL) to address the rolling shear and gap issues of cross laminated timber (CLT). The bending properties including apparent and effective bending stiffness, shear stiffness, moment capacities and failure modes of CLPs were evaluated by a combination of modal tests and third-point bending tests of beam specimens cut from the panels. The static bending test results showed that the apparent bending stiffness values of 3-layer and 5-layer CLPs were up to 20% and 43% higher than the corresponding values of 3-layer and 5-layer generic CLT, respectively. The bending moment capacity values of 3-layer and 5-layer CLPs were up to 37% and 87% higher than the corresponding values of 3-layer and 5-layer generic CLT, respectively. The use of SCL in transverse layers eliminated the potential rolling shear failure in CLT and increased the stiffness properties. The apparent and effective bending stiffness predicted by shear analogy method had a good agreement with corresponding values measured by bending tests and/or modal tests. The prediction of bending moment capacity using shear analogy method cannot be validated due to the rolling shear failure and tension failure modes observed in certain groups.

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... The Foschi and Yao model has been used successfully to study the influence of the DOL effect on the strength characteristics of dimension lumber, CLT, and other engineered wood products [5,[12][13][14]. To improve CLT's mechanical properties and expand its raw material sourcing, hybrid CLT (HCLT), which is fabricated from various kinds of solid wood laminates and structural composite lumber and bamboo-such as laminated veneer lumber, oriented strand board (OSB), laminated strand lumber (LSL), and bamboo scrimber-has been developed recently [16][17][18][19][20][21][22][23][24][25]. The production efficiency, fire resistance, and mechanical properties of HCLT were improvements on those of regular CLT [20]. ...
... Davids et al. [17] evaluated the bending and shear properties of HCLT specimens made from lumber and LSL, and found that incorporating LSL into the core layer of CLT increased the average bending stress at failure by 23%. Researchers at the Wood Science and Technology Center at the University of New Brunswick, Canada, also conducted a series of studies on the mechanical performance of HCLT and found that the bending and shear capacities of HCLT were significantly improved from those of regular CLT [21][22][23]. ...
Article
Given the nature of cross-laminated timber (CLT), with an orthogonal arrangement and rolling shear characteristics of transverse layers, it has a more complex duration-of-load (DOL) effect than other engineered wood products, such as glued-laminated timber. Developing hybrid CLT (HCLT) with structural composite lumber, which can improve the mechanical properties and material sources of CLT, is gaining increasing interest. Construction oriented strand board (COSB) and spruce-pine-fir (SPF) dimension lumber were used to fabricate HCLT specimens for this study. The regular SPF CLT and HCLT specimens having different lay-ups and numbers of layers were subjected to low-cycle fatigue bending and shear loading tests. The Foschi and Yao damage accumulation model was calibrated using the test results. The DOL factors for the CLT and HCLT specimens were calculated using the stress ratio evaluation method. Results showed that the primary failure modes for the fatigue test specimens were the same as those observed in previous short-term ramp loading tests, and a good fit was observed between the model's predictions and the test data. The DOL factor corresponding to a load duration of 50 years, for a three-layer shear CLT specimen, was determined to be 0.53, which was lower than that recommended in CSA O86-19. The fatigue life and long-term performance of CLT were improved by using COSB panels as CLT layers. The HCLT specimens that used COSB only as the transverse layer showed advantages in fatigue life, long-term performance, and practical applications.
... A new type of MTP, named cross laminated panel (CLP), consisting of sawn lumber pieces and SCL panels has been developed in the past years in Canada. The development and evaluation of mechanical properties of CLPs were presented in [1][2]. The results showed that the CLPs provided increased stiffness properties and overcame the rolling shear issue of CLT. ...
... The shear analogy method is adopted for the structural analysis of CLT including stiffness, stress and strain calculations in North America [3]. It has been verified that shear analogy method can be used for the calculation of stiffness properties of CLP [1][2]. However, the strain distribution cannot be easily obtained through traditional experimental test methods. ...
Conference Paper
The strain distributions of 5-layer composite laminated panels (CLP) made of lumber and laminated strand lumber (LSL) and of cross laminated timber (CLT) were investigated by both experimental and analytical methods. The failure modes and loads of beam specimens cut from the panels were recorded and analysed for short span shear test and third-point bending test. Digital imaging correlation (DIC) technique was used to measure the shear and normal strain of area of interests during the tests. The shear analogy method was used to calculate the theoretical strain distributions of the different build-ups with the materials properties obtained from component tests. Results showed that the DIC strain distributions agreed well with the ones calculated by shear analogy method in terms of general shape and magnitude. However, the DIC strain distribution showed scattered peaks, which were high or low strain spots in the DIC strain contours caused by the variation of local materials properties, gluelines, gaps and initial micro cracks.
... The hybrid CLT products could reduce the production cost because of the reduced efforts to layup of individual lumber pieces and the possible elimination of the need to press the panel on all four sides simultaneously, improve the rolling shear strength and stiffness properties of generic CLT since SCL has relatively high shear strength and rigidity, and improve the fire resistance of CLT due to the elimination of gaps present in generic CLT made with non-edge-glued dimension lumber. The research on three-and five-layer hybrid CLT, recently conducted in the Wood Science and Technology Centre, the University of New Brunswick, Canada, showed that the bending stiffness, moment capacity, and shear capacity of hybrid CLT were increased to a large degree in comparison to generic one [22][23][24]. ...
Chapter
Full-text available
This chapter provides information related to commonly used wood construction methods (i.e. light frame, post-and-beam, and mass timber) and mass timber products. It briefly discusses the manufacturing of four major lumber-based mass timber products (i.e. glue laminated timber, nail laminated timber, dowel laminated timber, and cross laminated timber), and their available dimensions and typical applications. Discussion also addresses primary lumber products, such as dimension lumber, machine stress rated lumber, and finger joined lumber, which are the building blocks from which mass timber products are manufactured. Advantages of using wood in construction are largely illustrated by examples from North American practices. The life cycle assessment concept is also introduced.
Article
Full-text available
Hybrid cross laminated timber (HCLT) was fabricated using lumber and/or laminated strand lumber (LSL), the mechanical performances of which were evaluated. To reach this goal, the mechanical properties of LSL and the bending properties of CLT and HCLT were measured in this study. The properties of LSL measured included the tension strength (only in the major direction), shear strength, shear modulus, and modulus of elasticity (MOE) and modulus of rupture (MOR). The failure mode of each kind of specimens was visually examined and recorded. Four types of CLT panels, one generic CLT (used as control) and three types HCLT were fabricated. The properties measured included the bending properties (in the major direction) and planar shear properties (in both major and minor directions). It was found that the HCLT had better bending and planar shear properties than that of generic CLT. The MOE and MOR of HCLT having LSL as the outer layers were 19% and 36% higher than those of generic one, respectively. The MOE and MOR of HCLT having LSL as core layer (replacing the cross lumber layer) were 13% and 24% higher than that of generic CLT, respectively. The failure modes of four types of CLT observed included the planar shear failure of cross lumber layer, tension failure of bottom LSL, and tension failure of bottom lumber, especially tension failure of lumber originated at a knot(s).
Article
Full-text available
Non-destructive evaluation (NDE) methods are common for grading structural lumber with static bending as the traditional NDE method for strength. More recently, longitudinal and transverse vibration techniques have also been proposed for grading lumber. In this study, unjointed and finger-jointed sawn lumber has been evaluated by these traditional and relatively new NDE methods. In total, 188 pieces of 38 mm×89 mm black spruce lumber were tested. Of these, 40 were unjointed, 47 had 2–3 finger joints, and 101 had 5–7 finger joints. The main objective was to evaluate the reliability of the various NDE techniques in predicting the bending stiffness and tensile strength of finger-jointed lumber with different number of finger joints. Results show that all NDE methods provide stiffness values of unjointed and finger-jointed lumber that correlate well with laboratory measured static bending stiffness with R2 values ranging from 0.76 to 0.97. Moreover, lumber with finger joints has lower bending stiffness than unjointed lumber. Based on the correlation coefficients, there is no evidence that finger joints affect the precision of the strength prediction by NDE methods.
Conference Paper
The strain distributions of 5-layer composite laminated panels (CLP) made of lumber and laminated strand lumber (LSL) and of cross laminated timber (CLT) were investigated by both experimental and analytical methods. The failure modes and loads of beam specimens cut from the panels were recorded and analysed for short span shear test and third-point bending test. Digital imaging correlation (DIC) technique was used to measure the shear and normal strain of area of interests during the tests. The shear analogy method was used to calculate the theoretical strain distributions of the different build-ups with the materials properties obtained from component tests. Results showed that the DIC strain distributions agreed well with the ones calculated by shear analogy method in terms of general shape and magnitude. However, the DIC strain distribution showed scattered peaks, which were high or low strain spots in the DIC strain contours caused by the variation of local materials properties, gluelines, gaps and initial micro cracks.
Article
This paper presents a method of simultaneous evaluation of bending and shear moduli of wooden beams. The method, which is based upon the measurement of two natural frequencies of a beam, is simple to perform. Existing techniques for determining shear moduli of wood based materials are either too cumbersome to carry out or prone to measurement errors. Using this method tests were conducted on matched groups of clear and knotty specimens. It was found that for clear specimens a value of 20 can be assumed for the E to G ratio. For specimens which contain knots the variation was so large that no corresponding figure can be suggested with confidence. But the ratio for knotty materials is though to be higher than 20.
Methodenvergleich approximativer Nachweisverfahren für Brettsperrholz
  • T Bogensperger
  • G Silly
  • G Schickhofer
Bogensperger, T., Silly, G., & Schickhofer, G.: Methodenvergleich approximativer Nachweisverfahren für Brettsperrholz. Report #: MMSM 2.2.3 sfem_mat, holz.bau forschungs GmbH, Institut für Holzbau und Holztechnologie, Technische Universität Graz, Graz, Austria, 2012.