The main culprit in the pathogenesis of ischemia/reperfusion (I/R) injury is the overproduction of reactive oxygen species (ROS). Hydrogen peroxide (H2O2), the most abundant form of ROS produced ...during I/R, causes inflammation, apoptosis and subsequent tissue damages. Here, we report H2O2-responsive antioxidant nanoparticles formulated from copolyoxalate containing vanillyl alcohol (VA) (PVAX) as a novel I/R-targeted nanotherapeutic agent. PVAX was designed to incorporate VA and H2O2-responsive peroxalate ester linkages covalently in its backbone. PVAX nanoparticles therefore degrade and release VA, which is able to reduce the generation of ROS, and exert anti-inflammatory and anti-apoptotic activity. In hind-limb I/R and liver I/R models in mice, PVAX nanoparticles specifically reacted with overproduced H2O2 and exerted highly potent anti-inflammatory and anti-apoptotic activities that reduced cellular damages. Therefore, PVAX nanoparticles have tremendous potential as nanotherapeutic agents for I/R injury and H2O2-associated diseases.
In this work, a new type of structural sandwich panels made with laminated oil palm wood core and rubberwood-based oriented strand board (OSB)/plywood faces were introduced for energy-efficient wall ...applications in Thailand. Effect of the manufacturing process and material parameters including adhesive content (250 g/m
2
and 500 g/m
2
), core configuration (cross or parallel laminated oil palm lumber) and density (low and medium) and face material type (rubberwood-based OSB/plywood) on panel’s properties were explored. The panels were produced using two-component polyurethane adhesive and a constant clamping pressure of 0.6 MPa. Adhesive content of 250 g/m
2
was found to be sufficient for gluing all layers, with wood failure percentage of more than 80% as required by the standard. In-plane dimensional stability of the panels was mainly affected by the core configuration; it was better for cross laminated oil palm wood core sandwich panel. Higher core density resulted in increased density, thermal conductivity and compressive strength in the major direction but lower thermal resistance of the panel. The plywood face sandwich panels provided slightly higher compressive strength than OSB face sandwich panel, and their failure mechanisms were also different. The heat loss of these panels was about one-third of concrete and brick walls, hence, they can provide better insulation for indoor space. Based on the measured thermal conductivity, it was expected that these panels would pass the energy criteria according to Building Energy Code of Thailand. Thus, from the energy saving and sustainability perspectives, these panels can potentially be used as energy efficient wall panels for buildings, not only for Thailand but also for other tropical countries, where the oil palm wood and rubberwood resource is available.
Wood is a preferred material for constructing staircases due to its appealing aesthetic features. The use of wood, especially hardwoods such as red oak (Quercus rubra), white oak (Quercus alba), ...yellow poplar (Liriodendron tulipifera), and hard maple (Acer saccharum), has been the main construction material for staircases over the years. Staircase designs have evolved because of the flexibility of wood and working with specialized manufacturing machinery. A stair guard system connection must be designed to resist rotational and translational movements whenever a force is applied to the handrail. The demand for structural design values in wooden stair guards has been steadily increasing, driven by the needs of engineers, designers, builders, and end-users alike. This paper presents experimental data for four stair guard connections (post-to-rail, infill-to-footing, infill-to-rail, and rail-to-rail) encountered in a hardwood stairway handrail guard system. The data generated from this research could be useful for modeling the structural behavior of the connections.
The feasibility of using β-cyclodextrin (βCD) as an eco-friendly carrier of boric acid for the protection of strand-based wood composites against decay fungi was evaluated. The formation of a ...βCD-boric acid (βCD-B) complex was confirmed by the appearance of the boron-oxygen bond by using attenuated total reflection-Fourier transform infrared spectroscopy. Chemical shifts of around 6.25 and 1.41 ppm were also observed in
H Nuclear Magnetic Resonance (NMR) and
B NMR spectra, respectively. The βCD-B preservatives at two levels (5 and 10 wt.%) were uniformly blended with southern pine strands that were subsequently sprayed with polymeric methylene diphenyl diisocyanate (pMDI) resin. The blended strands were formed into a loose mat by hand and consolidated into 25 × 254 × 12 mm oriented strand boards (OSB) using a hot-press. The OSB panels were cut to end-matched internal bonding (IB) strength and fungal decay resistance test specimens. The vertical density profiles (VDPs) of the IB specimens were measured using an X-ray based density profiler and the specimens with statistically similar VDPs were selected for the IB and decay tests. The IB strength of the treated specimens was lower than the control specimens but they were above the required IB strength of heavy-duty load-bearing boards for use in humid conditions, specified in the BS EN 300:2006 standard. The reduced IB of preservative-treated OSB boards could be explained by the destabilized resin upon the addition of the βCD-B complex, as indicated by the differential scanning calorimetry (DSC) results. The resistance of the OSB panels against two brown-rot fungi (i.e.,
or
) was evaluated before and after accelerated leaching cycles. The treated OSBs exposed to the fungi showed an average mass loss of lower than 3% before leaching, while the untreated OSBs had 49 and 35% mass losses due to decay by
or
, respectively. However, upon the leaching, the treatment provided protection only against
to a certain degree (average mass loss of 15%). The experimental results suggest that protection efficacy against decay fungi after leaching, as well as the adhesion of the OSB strands, can be improved by increasing the amount of pMDI resin.
•Cross-laminated timber (CLT) can be manufactured with preservative treated wood.•Lumber treated with Micronized Copper Azole-Type C (MCA-C) was used as CLT lamstock.•Bonding performance of CLT made ...using three adhesive systems were evaluated.•Polyurethane adhesive appeared to be suitable for cross-laminating MCA-C treated lumber.
The feasibility of manufacturing cross-laminated timber (CLT) from southern yellow pine (United States grown) treated with micronized copper azole type C (MCA-C) preservative was evaluated. Lumber (2x6 visually graded no. 2 boards) was treated to two retention levels (1.0 and 2.4 kg/m3), planed to a thickness of 35 mm, and assembled along with an untreated control group using three adhesive systems following product specifications: melamine formaldehyde (MF), resorcinol formaldehyde (RF), and one-component polyurethane (PUR). Block shear and delamination tests were conducted to examine the bonding performance in accordance with ASTM D905 and ASTM D2559 Standards, respectively. One-way analysis of variance and Kruskal-Wallis H test were conducted to evaluate the effects of preservative retention and adhesive type on block shear strength (BSS) and wood failure percentage (WFP). Regardless of adhesive type, the 1.0 kg/m3 retention treatment significantly lowered BSS compared to the untreated control. CLT composed of the laminations treated at 2.4 kg/m3 maintained BSS when PUR and RF were used but not MF. The average WFP of each CLT configuration ranged from 89% to 99%. The untreated CLT specimens did not experience any delamination under accelerated weathering cycles. The delamination rates of the treated specimens assembled using MF and RF increased with the preservative retention level, while PUR provided delamination rates less than 1% to the laminations treated at both levels. These combined data suggest that, under the conditions tested, PUR provided overall better bonding performance than MF and RF for MCA-C treated wood.
•Effects of preservative on rolling shear properties of Cross-laminated timber (CLT) were studied.•Four-point bending tests were conducted to evaluate rolling shear strength and modulus of CLT.•A ...simplified method for rolling shear strength estimation was validated against the Shear analogy.
The effect of micronized copper azole type C (MCA-C) treatment on rolling shear (RS) strength and RS modulus of cross-laminated timber (CLT) was evaluated. The CLT test specimens were either constructed with untreated 2 × 6 (38 mm × 140 mm) No. 2. southern yellow pine (the United States grown) laminations or MCA-C treated laminations. The shear-free modulus of elasticity (Esf) and longitudinal-radial shear modulus (GLR) of the laminations were non-destructively measured prior to CLT manufacturing. The average Esf and GLR of the untreated lumber were 11.08GPa and 231.42 MPa, respectively, while those of the treated lumber were 9.60GPa and 236.01 MPa, respectively. Four-point bending test described in EN 16,351 standard along with the Shear analogy method was adopted to measure the RS properties. The preservative treatment decreased the mean RS strength, while it increased the mean RS modulus. However, the differences in the means were not significant based on one-way analysis of variance and Kruskal-Wallis H test, respectively. The experimentally obtained bending stiffness of the CLT test specimens and the RS strength estimated using the simplified method described in the CLT Handbook were compared against the values obtained based on the Shear analogy. The agreement between these two approaches indicates that the short-span test setup implemented in this study and the simplified method can be used for measuring bending stiffness and estimating RS strength of 3-ply CLT.
AbstractRolling shear (RS) strength may govern load-carrying capacity of cross-laminated timber (CLT) subjected to high out-of-plane loading because high RS stresses may be induced in cross layers ...and wood typically has low RS strength. This study investigates RS strength properties of non-edge-glued CLT via experimental testing (short-span bending tests and modified planar shear tests) and numerical modeling. CLT specimens with different manufacturing parameters including two timber species (New Zealand–grown Douglas fir and Radiata pine), three lamination thicknesses (20, 35, and 45 mm), and various lamination aspect ratios (4.1–9.8) were studied. The lamination aspect ratio was found to have a substantial impact on RS strength of CLT. Higher aspect ratios led to a significant increase of RS strength, and an approximately linear relationship could be established. With similar lamination aspect ratios, the Radiata pine CLT had higher RS strength than the Douglas fir CLT. The two different test methods, however, yielded comparable RS strength assessments. Numerical models were further developed to study the influence of the test configurations and gaps in the cross layers on stress distributions in the cross layers. It was also found that the compressive stresses perpendicular to the grain in cross layers had negligible influence on the RS strength evaluations.
•Knots would not decrease rolling shear strength of cross laminated timber.•Knot presence affects rolling shear failure mechanisms.•Two-plate shear test can be used to evaluate effects of ...laminations’ heterogeneity.•Short-span bending test is more conservative than two-plate shear test.
The study experimentally and analytically investigated the effect of knots on the rolling shear (RS) strength of 3-ply southern yellow pine cross-laminated timber (CLT). Center-point bending tests and two-plate shear tests were conducted on six CLT configurations composed of different types of cross layer laminations based on knots conditions (No Knots, Sound Knots, and Decayed Knots) and pith conditions (Pith, No Pith). The shear analogy method was implemented to evaluate the RS strength values from the bending test results, which were compared against the results from the two-plate shear tests. The cross-layer laminations with either sound knots or decayed knots improved the RS strength of CLT. In general, the RS predicted by the shear analogy method was conservative.
Coupled cross-laminated timber (CLT) walls with steel link beams are a type of high-capacity lateral load resisting system for multistory buildings. In this study, a 6.6 m tall coupled CLT wall ...specimen with three steel link beams and mixed-angle screwed hold-downs was tested to ±4.5% drift to evaluate its cyclic performance. The system achieved peak strengths of +590 and −592 kN, while also exhibiting relatively high displacement ductility factors of 7.6 and 6.9 in the positive and negative directions, respectively. Failure of the system was characterized by combined bending and withdrawal of the mixed-angle screws in the hold-downs, yielding and eventual inelastic buckling of the steel link beams, CLT toe crushing, and local CLT delamination. In comparison with similar cantilever CLT shear walls, the coupled wall system exhibited 45% greater peak strength, dissipated approximately 50% more energy, and experienced less degradation of its energy dissipation capacity on repeated load cycles (when subjected to the same loading protocol). Following the initial test, the steel link beams, screw hold-downs, and damaged CLT regions were repaired, then the wall specimen was retested with the same loading protocol. The repaired wall behaved similarly to the original test and exhibited slightly higher energy dissipation and peak strength but more rapid strength deterioration under cyclic loading. The retesting provided evidence that it may be feasible to repair the coupled wall system after an earthquake because the damage was localized, and the main CLT wall elements were effectively protected from damage.
•Thirty high-capacity mixed angle screw hold-down connections were tested.•Mixed angle screws can provide a strong, stiff, and ductile hold-down connection.•Current design methods provide a ...conservative prediction for strength.
This paper experimentally examines structural performance of novel cross laminated timber (CLT) hold-down connections consisting of customised steel brackets and self-tapping screws installed with mixed angles relative to loading. The installation of screws at mixed angles combines the high strength and stiffness of inclined screws with the high ductility of 90° screws creating a strong, stiff, and ductile connection. A total of 30 high capacity connection specimens comprising two timber species and five connection configurations are tested under monotonic and cyclic loading. The ratios between inclined screws and 90° screws are investigated in order to optimise the connection seismic performance. Connections consisting of 12× Ø12 mm inclined screws and 12 to 24× Ø12mm / 10 mm 90° screws were found to demonstrate high ultimate strength (470–593 kN), high initial stiffness (212–269 kN/mm) and high ductility (µ=10–20) under cyclic loading. Current strength calculation methods for the connection design are compared to the experimental results and are shown to provide conservative design predictions.
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