Recently, there has been a growing interest in using Cross-Laminated Timber (CLT) in the construction industry, particularly as slabs and walls. This heightened interest is attributed to CLT’s ...favorable mechanical properties, ease of prefabrication, and environmental advantages. Consequently, CLT-Concrete Composite (CCC) floor systems have gained more attention for their application in mid- and high-rise buildings. These CCC systems offer substantial advantages over standalone CLT slabs, including enhanced bending stiffness, increased load-bearing capacity, and improved dynamic performance. However, a notable research gap exists when it comes to the deconstruction of CCC slabs, a crucial aspect for enhancing sustainability and reducing the environmental impacts of these structural elements. This study investigates innovative demountable shear connections designed for a reusable prefabricated CCC floor system. A series of push-out tests were conducted on six different shear connectors to obtain the shear properties of the connection. The demountable shear connections exhibited a load-bearing capacity similar to conventional permanent connections. Moreover, these connections demonstrated a significantly higher stiffness than existing options. One specimen was examined in a reuse scenario test to evaluate its reusability, which revealed a notable increase in stiffness during its second use. A three-dimensional finite element model of the push-out test was validated and calibrated with the experimental results. This model was utilized to study the load-bearing behavior of the notched connections.
•Six CLT-concrete composite deconstructable notched shear connections were tested.•Proposed connections exhibit stiffness up to seven times higher than existing ones.•The strength of the proposed connections surpasses existing demountable ones.•The shear connections remain demountable even loaded up to 60% of their strength.•Inclined-notched connections have more ductility than perpendicular-notched ones.
The quality of network clustering is often measured in terms of a commonly used metric known as "modularity". Modularity compares the clusters found in a network to those present in a random graph (a ..."null model"). Unfortunately, modularity is somewhat ill suited for studying spatially embedded networks, since a random graph contains no basic geometrical notions. Regardless of their distance, the null model assigns a nonzero probability for an edge to appear between any pair of nodes. Here, we propose a variant of modularity that does not rely on the use of a null model. To demonstrate the essentials of our method, we analyze networks generated from granular ensemble. We show that our method performs better than the most commonly used Newman-Girvan (NG) modularity in detecting the best (physically transparent) partitions in those systems. Our measure further properly detects hierarchical structures, whenever these are present.
Design of nanocellulose-based composite materials suitable for selective disintegration, recovery and recycling of individual components is of great scientific and technical interest. Cellulose ...nanofiber/epoxy (CNF/EP) composites are candidate bio-based substitutes for petroleum-based materials. However, chemical recovery of such intimately mixed nanocomposites has not been addressed, due to the limited chemical stability of nanocellulose and due to the covalently crosslinked epoxy network. In this work we develop CNF/EP composites designed for selective disintegration. Deconstruction is achieved by including two types of labile linkages to the polymer network; acetals and esters. Besides enabling recycling of the CNF reinforcement, the thermoset constituents were further depolymerized into valuable monomeric units in 63-95% yield. In addition, the preparation of both; epoxy monomers and final composite materials is performed using solely bio-derived materials and solvents.
Design of nanocellulose-based composite materials suitable for selective disintegration, recovery and recycling of individual components is of great scientific and technical interest.
Here, CelA is the most abundant enzyme secreted by Caldicellulosiruptor bescii and has been shown to outperform mixtures of commercially available exo- and endoglucanases in vitro. CelA contains both ...a glycoside hydrolase family 9 endoglucanase and a glycoside hydrolase family 48 exoglucanase known to be synergistic in their activity, connected by three cellulose-binding domains via linker peptides. Here, repeated aspartate residues were introduced into the N-terminal ends of CelA GH9 and GH48 domains to improve secretion efficiency and/or catalytic efficiency of CelA. Among several constructs, the highest activity on carboxymethylcellulose (CMC), 0.81 ± 0.03 mg/mL was observed for the C. bescii strain containing CelA with 5-aspartate tag at the N-terminal end of GH9 domain – an 82% increase over wild type CelA. In addition, Expression of CelA with N-terminal repeated aspartate residues in C. bescii results in a dramatic increase in its ability to grow on Avicel.
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