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FE validation of the equivalent diameter calculation model for grouped headed studs
Milan Spremic,Marko Pavlovic,Zlatko Markovic,Milan Veljkovic,Dragan Budjevac 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.26 No.3
Existing design codes for steel-concrete composite structures give only general information about the shear connection provided by headed studs in group arrangement. Grouting of the openings in prefabricated concrete slabs, where the grouped headed studs are placed in the deck pockets is alternative to cast-in-place decks to accomplish fast execution of composite structures. This paper considers the possibility to reduce the distance between the studs within the group, bellow the Eurocode limitations. This may lead to increased competitiveness of the prefabricated construction because more studs are placed in the group if negative effectives of smaller distances between studs are limited. The main purpose of this work is to investigate these limits and propose an analytical calculation model for prediction of the shear resistance of grouped stud arrangements in the deck pockets. An advanced FEA model, validated by results of push-out experiments, is used to analyze the shear behavior of the grouped stud with smaller distance between them than recommended by EN 1994-1. Calculation model for shear resistance, which is consistent with the existing Eurocode rules, is proposed based on a newly introduced equivalent diameter of the stud group, <i>d</i><sub>G</sub>. The new calculation model is validated by comparison to the results of FE parametric study. The distance between the studs in the longitudinal direction and the number of stud rows and columns in the group are considered as the main variables.
Milica Veljkovic,Relja Stepanovic,Katarina Banjanac,Marija Ćorović,Ana Milivojevic,Milica Simović,Milan Milivojević,Dejan Bezbradica 한국공업화학회 2023 Journal of Industrial and Engineering Chemistry Vol.117 No.-
Within this study, the investigation of potential selective immobilization of fructosyltransferase (FTase) derived from Aspergillus aculeatus (from commercial enzyme preparation Pectinex® Ultra SP-L) onto the polystyrenic macroporous resin Purolite® A109 and its further utilization for the synthesis of a highly valuable group of prebiotic compounds named fructo-oligosaccharides (FOS), was performed. The obtained results suggest that partial purification of fructosyltransferase from complex enzyme mixture with predominant pectinase activity (ratio of activity immobilization yields around 20.0) occurred by performing a simple immobilization protocol, provided that immobilization lasted for 5 h using an enzyme concentration of 50 mg g−1 of support under slightly acidic conditions (pH 6.0). Immobilized preparation was thereafter successfully utilized for FOS synthesis (56–59 % FOS of total sugars) in both a batch and air-lift reactor system. Operational stability study proved the exceptionally high potential of immobilized preparation for reproducible and cost-effective application, since 90 % of initial activity was preserved after ten consecutive reaction cycles. Thereafter, a prospectus for continuous production of FOS in the air-lift reactor was assayed. Achieved yields, 53 % FOS of total sugars for at least 9 h, indicated the great suitability of the obtained immobilized preparation for application in large-scale systems.
Florentia Kavoura,Angeliki Christoforidou,Marko Pavlovic,Milan Veljkovic 국제구조공학회 2022 Steel and Composite Structures, An International J Vol.43 No.4
In response to the sustainability requirements set in the EU Commission´s “Green Deal” towards reduction of the greenhouse gas emissions, it is estimated that the structural design for deconstruction is going to contribute considerably to the sustainable development of the built environment. The demountability of multi-material structural systems basically depends on the shear connectors used in the structural system. This paper focuses on a type of demountable injected shear connector with an injected steel-reinforced resin (iSRR) which consists of spherical steel particles embedded in a resin. Its application to steel-toconcrete and steel-to-Fiber Reinforced Polymer (FRP) decks is presented along with its benefits. In parallel, an overview of the experimental and numerical research on the evaluation of the mechanical properties of the demountable bolted connectors with iSRR is discussed. Last, detailed finite element (FE) models and a parametric study are performed to quantify the confinement level of the SRR material influenced by the oversized hole diameter.
Experimental Behaviour of the Reverse Channel Joint Component at Elevated and Ambient Temperatures
Fernanda Lopes,Aldina Santiago,Luís Simões da Silva,Tim Heistermann,Milan Veljkovic,José Guilherme da Silva 한국강구조학회 2013 International Journal of Steel Structures Vol.13 No.3
The reverse channel connection appears to have the best combination of desirable features under fire loading: moderate construction cost, ability to develop catenary action and extremely high ductility through deformation of the web channel (Ding and Wang, 2007). This paper presents the results of an experimental investigation of a reverse channel component conducted at the University of Coimbra as part of the European RFCS COMPFIRE Project, the main focus of which is to characterise the behaviour of steel joints that connect steel beams to concrete-filled tubular columns under natural fire loading. A series of tensile and compressive tests at ambient and elevated temperatures was conducted. The purposes of the experimental tests were to characterise the strength, stiffness and ductility of this joint component and to establish a relationship between force,displacement and temperature.