The behavior of interfaces between granular soils and structural construction materials has an important impact on the monotonic and cyclic response of many soil-structure interaction (SSI) systems. ...Understanding the mechanics and modeling of these interfaces is an important step towards a safe and effective design and analysis of SSI problems. An extensive literature search for a ‘one-stop shop’ providing a comprehensive exposition on the mechanical characteristics and numerical modeling approaches of granular soil-structure interfaces yielded less than encouraging results. This paper seeks to bridge this knowledge gap in as concise manner as possible. To this end, the effects of the essential elements of the SSI problem, including soil and structural features as well as loading conditions, on the deformation and stress transformation mechanism of the interface are critically examined. Simple and advanced interface constitutive modeling methods are discussed, and implementation techniques of interface elements in finite element codes are explained. Additionally, a method to incorporate the effect of particle breakage to improve the capabilities of an elasto-plastic constitutive simulation of the cyclic accumulative contraction in granular interface modeling is introduced.
Reinforced concrete and steel are the most commonly used materials in bridge applications in Quebec (Canada). The production of these materials has a significant environmental impact and contributes ...to the scarcity of non-renewable resources due to the numerous maintenance requirements during the life of the structure. Consequently, there are governmental initiatives and efforts in the province of Quebec to promote the use of aluminum and engineered wood in the construction and rehabilitation of roadway bridges. Those two materials are not widely used due to the short-term vision of decision makers and the lack of technical knowledge for structural uses in highway bridge structures. However, they can be competitive materials due to their local production, durability and recyclability. The life cycle assessment method allows for an analysis of the use of complementary materials, considering all the stages of the life cycle of a structure. The comparison of a roadway bridge made of an aluminum deck on glulam timber beams against a bridge made of an aluminum deck on steel girders shows that, due to the local production and low environmental impact of glulam timber, the aluminum-to-timber bridge is economically and environmentally more advantageous than the aluminum-to-steel bridge. Similarly, a comparison of this alternative aluminum/wood solution to the conventional concrete slab-on-steel girder bridge solution shows a decrease in overall cost by 86% and a decrease in environmental impacts by 88% due to the ease of prefabrication and the relatively low number of interventions over its lifetime.
•Extensive structural test program in both tension and compression designed.•Resistance of metallized faying surfaces used with slip-critical connections characterized.•Much greater slip resistance ...than typical uncoated blast-cleaned surface observed.•Results important for future code development and steel bridge fabrication.
Bolted connections are designed as slip-critical if they would be subjected to fatigue or significant load reversal, typical in steel girder bridges. In this type of connection, slip of any magnitude must be prevented to eliminate intolerable geometric changes and consequent stability problems. The surface condition of the connected steel components, also known as the faying surface, controls the level of the slip resistance. Design provisions for slip-critical bolted connections in contemporary standards, such as the Canadian Highway Bridge Design Code CAN/CSA S6-06 and the American Institute of Steel Construction (AISC) Specifications, specify desired conditions for faying surfaces and associated slip coefficients for design purposes. Currently, these standards do not address faying surface conditions that are metallized, although steel bridge elements are widely metallized to provide long-term protection against wear and corrosion. Steel bridge fabricators are thus compelled to mask off all faying surfaces before applying the protective coating on the structural elements. This practice is highly labor-intensive, costly and time consuming. In this paper, the resistance of slip-critical bolted joints with zinc-based metallized faying surfaces is characterized in the light of the North American design standards. The mean slip coefficients obtained from short-duration compression and tension test regimes for different connection parameters revealed much greater slip resistance than the typical uncoated blast-cleaned Class B faying surface.
Spermatozoa in animal species are usually highly elongated cells with a long motile tail attached to a head that contains the haploid genome in a compact and often elongated nucleus. In Drosophila ...melanogaster, the nucleus is compacted two hundred-fold in volume during spermiogenesis and re-modeled into a needle that is thirty-fold longer than its diameter. Nuclear elongation is preceded by a striking relocalization of nuclear pore complexes (NPCs). While NPCs are initially located throughout the nuclear envelope (NE) around the spherical nucleus of early round spermatids, they are later confined to one hemisphere. In the cytoplasm adjacent to this NPC-containing NE, the so-called dense complex with a strong bundle of microtubules is assembled. While this conspicuous proximity argued for functional significance of NPC-NE and microtubule bundle, experimental confirmation of their contributions to nuclear elongation has not yet been reported. Our functional characterization of the spermatid specific Mst27D protein now resolves this deficit. We demonstrate that Mst27D establishes physical linkage between NPC-NE and dense complex. The C-terminal region of Mst27D binds to the nuclear pore protein Nup358. The N-terminal CH domain of Mst27D, which is similar to that of EB1 family proteins, binds to microtubules. At high expression levels, Mst27D promotes bundling of microtubules in cultured cells. Microscopic analyses indicated co-localization of Mst27D with Nup358 and with the microtubule bundles of the dense complex. Time-lapse imaging revealed that nuclear elongation is accompanied by a progressive bundling of microtubules into a single elongated bundle. In Mst27D null mutants, this bundling process does not occur and nuclear elongation is abnormal. Thus, we propose that Mst27D permits normal nuclear elongation by promoting the attachment of the NPC-NE to the microtubules of the dense complex, as well as the progressive bundling of these microtubules.
The slip resistance of high strength bolted connections depends on the surface condition of the connected parts, also known as the faying surfaces. Metalizing and galvanizing are two commonly used ...corrosion protection solutions in steel bridge construction, providing physical barrier as well as sacrificial protection. Practical situations exist where galvanized secondary structural components are joined to primary elements that are metalized in a slip-critical connection. Contemporary bridge design standards, such as the Canadian Highway Bridge Design Code, CAN/CSA S6-06, and the American Institute of Steel Construction (AISC) specifications, ANSI-AISC 360-2010, however do not specify slip coefficient for slip-resistant connections with one faying surface metalized and the other face galvanized. Steel bridge fabricators are therefore compelled to mask off all connection faying surfaces before metalizing. This exercise is time-consuming, labor-intensive, and costly. In this investigation, the resistance of slip-critical joints having metalized–galvanized faying surfaces is characterized in view of the current North American design standards. The mean slip coefficient, determined from short-duration tension and compression test regimes, revealed slip resistance greater than the typical faying surface with roughened hot-dip galvanized finish, and in the majority of cases, greater than the typical uncoated blast-cleaned faying surfaces.
•Slip-critical connections with metalized-galvanized (M-G) faying surfaces characterized.•Extensive tests program in tension and compression designed.•Effect of different connection variables on the slip resistance investigated.•M-G faying surfaces developed greater slip resistance than the typical galvanized finish.•Results significant for steel bridge fabrication in North America.
Winning Trophies or Making Good Structural Engineers Annan, Charles-Darwin
Structural engineering international : journal of the International Association for Bridge and Structural Engineering (IABSE),
20/5/1/, Letnik:
27, Številka:
2
Journal Article
The antioxidant capacity of irradiated κ-, ι-, λ-carrageenans were investigated using the hydroxyl radical scavenging assay, reducing power assay and DPPH radical scavenging capacity assay. The ...degree of oxidative inhibition increased with increasing concentration and dose. The type of carrageenan had also an influence on its antioxidant activity which followed the order of lambda<iota<kappa. Increase in oxidative property with radiation dose can be attributed mainly to the depolymerization of the carrageenans with corresponding increase in reducing sugar. The antioxidant properties of these carrageenan oligomers were lower than that of ascorbic acid and galactose sugar.
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•The antioxidant capacity of gamma irradiated κ-, ι-, λ-carrageenans increased with increasing concentration and dose.•The type of carrageenan had an influence on its antioxidant activity which followed the order of lambda<iota<kappa.•Increase in oxidative property with radiation dose can be attributed mainly to the depolymerization of the carrageenans with corresponding increase in reducing sugar.
A unique, in-depth view of Victorian London during the record-breaking summer of 1858, when residents both famous and now-forgotten endured "The Great Stink" togetherWhile 1858 in London may have ...been noteworthy for its broiling summer months and the related stench of the sewage-filled Thames River, the year is otherwise little remembered. And yet, historian Rosemary Ashton reveals in this compelling microhistory, 1858 was marked by significant, if unrecognized, turning points. For ordinary people, and also for the rich, famous, and powerful, the months from May to August turned out to be a summer of consequence.Ashton mines Victorian letters and gossip, diaries, court records, newspapers, and other contemporary sources to uncover historically crucial moments in the lives of three protagonists-Charles Dickens, Charles Darwin, and Benjamin Disraeli. She also introduces others who gained renown in the headlines of the day, among them George Eliot, Karl Marx, William Thackeray, and Edward Bulwer Lytton. Ashton reveals invisible threads of connection among Londoners at every social level in 1858, bringing the celebrated city and its citizens vibrantly to life.
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