CRESTED SHEAR CONNECTORS APPLICATION TO COMBINE REINFORCED CONCRETE SLAB AND PLANK-NAILED STRUCTURE OF BRIDGE SPAN

Introduction. The construction of bridges using timber materials is experiencing a real boom throughout the world .The USA is considered to be a leader, where 80% of the bridges are made of timber or materials based on it. In Russia timber bridge construction has been stagnating for the last 50 years, although there is a need for these bridges. Timber structures could solve many problems with Russian roads, especially in remote areas. Timber structures are widely considered to be outdated, so they cannot meet current requirements of load capacity and durability, also they are vulnerable to atmospheric influences, etc. But foreign experience proves the contrary. The article is devoted to the implementation of new plank-nailed spans that meet current requirements of load capacity, reliability and durability.Materials and methods. The authors suggest and describe a new span structure. The span consists of planktimber- nailed-dowel blocks and a reinforced concrete slab generating a composite action. Some special crested shear connectors are suggested as combining elements. The top part works as flexible shear connectors in a reinforced concrete slab. The bottom part works as dowels with steel joints and timbers structures. The investigation of the stress-strain state of the structure has been completed within “compound beam” theory.Results. The application of the cast-in-place reinforced concrete slab allows to protect supporting timber structures against atmospheric influences, dirt, cracking from the sun rays, radiation and provides at least 50-year durability. The timber preservation provides a specified service life. The application of suggested connection with composite action between a reinforced concrete slab and supporting timber structures increases effectiveness of the composite timber concrete structure compared to steel and reinforced concrete structures. Trans-Baikal territory, Irkutsk and Arkhangelsk Regions, Khabarovsk Territory, the Republics of Sakha (Yakutia), Buriatia, Karelia are in the greatest need of the timber concrete composite spans, because they have a lot of forest resources and old timber bridges that are still in service

Chitosan Sponges for Efficient Accumulation and Controlled Release of C-Phycocyanin

The paper proposed a new porous material for wound healing based on chitosan and C-phycocyanin (C-PC). In this work, C-PC was extracted from the cyanobacteria Arthrospira platensis biomass and purified through ammonium sulfate precipitation. The obtained C-PC with a purity index (PI) of 3.36 ± 0.24 was loaded into a chitosan sponge from aqueous solutions of various concentrations (250, 500, and 1000 mg/L). According to the FTIR study, chitosan did not form new bonds with C-PC, but acted as a carrier. The encapsulation efficiency value exceeded 90%, and the maximum loading capacity was 172.67 ± 0.47 mg/g. The release of C-PC from the polymer matrix into the saline medium was estimated, and it was found 50% of C-PC was released in the first hour and the maximum concentration was reached in 5–7 h after the sponge immersion. The PI of the released C-PC was 3.79 and 4.43 depending on the concentration of the initial solution

Bio-inspired materials for nutrient biocapture from wastewater: Microalgal cells immobilized on chitosan-based carriers

The successful application of the cross-linked chitosan-based polymers for microalgae immobilization and biocapture of nutrients is reported for the first time. Highly porous, hydrophilic polymers were obtained by cross-linking of 250 kDa or 600 kDa chitosan with glutaraldehyde. Both cross-linked chitosan polymers were characterized by high microalgae immobilization efficiency and supported the prolonged cultivation of immobilized Lobosphaera sp. IPPAS 2047 cells without impairing their growth and photosynthetic activity. The 600 kDA chitosan-based polymers demonstrated higher mechanical and biological stability during 7 d incubation than those based on the 250 kDa chitosan. The nutrient removal capacity of the chitosan-immobilized Lobosphaera cells was significantly higher as compared to that of the suspended cells. The specific removal rates of inorganic phosphate and nitrate by the suspended microalgae cells cultivated without cross-linked chitosan polymers comprised 0.36 and 0.50 mg mg−1 Chl d−1, while the chitosan-immobilized Lobosphaera cells consumed phosphate and nitrate at rates 6.01 and 0.65 mg mg−1 Chl d−1, respectively. Collectively, the cross-linked chitosan-based polymers were shown to be environment-friendly materials providing the enhancement of nutrients bioremoval from wastewater by immobilized microalgae cells. The nutrient-enriched microalgae biomass immobilized on the biodegradable and non-toxic chitosan carriers can be applied as slow-releasing biofertilizer. © 2020 Elsevier Lt