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Yong Wang - One of the best experts on this subject based on the ideXlab platform.
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New Mechanism of Load Introduction into Concrete-Filled Steel Tubular Columns
Journal of Structural Engineering, 2016Co-Authors: Mohammad Hassan Mollazadeh, Yong WangAbstract:AbstractThis paper presents the results of new Load-Introduction tests and numerical simulations to investigate the mechanism of Load Introduction from shear connections to concrete-filled steel tubular (CFST) columns, and the effectiveness of changing different construction details. The results of the tests have confirmed the authors’ recently proposed new Load-Introduction mechanism, obtained from an extensive numerical study. In the new Load-Introduction mechanism, the connection Load is introduced to the concrete core via the column length above and within the connection or the cap plate on top of the column. There is no limit to the Load-Introduction length above the connection. Below the connection, there is transfer of forces from the steel tube to the concrete core, but the total force in the column remains unchanged. This Load Introduction mechanism is different from that assumed in the various current design codes. This study has an important implication for CFST column design: using shear conne...
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Design implications of a new Load Introduction mechanism into concrete-filled steel tubular columns
Structures, 2016Co-Authors: Mohammad Hassan Mollazadeh, Yong WangAbstract:Abstract This paper presents the design implications of a new Load Introduction mechanism into concrete-filled steel tubular columns (CFST) proposed by the authors recently. According to the new Load Introduction mechanism, the beam-column connection Load is introduced into the composite column through the column length above and within the connection. Based on the new Load Introduction mechanism, for slender CFST column design, a “concrete strength reduction factor” should be used to account for incomplete Load Introduction, when calculating the CFST column cross-section flexural stiffness. For CFST columns under combined axial compression and bending, the concrete strength reduction factor should be used when calculating the compression resistance, but should be ignored when calculating the bending resistance because composite action is always guaranteed for bending of the CFST column. The most important implication of the new Load Introduction mechanism is that the concrete core above the connection should be designed to resist the additional compressive force introduced to the concrete core below the connection. A further implication is that for ambient temperature design, the steel contribution ratio (steel section plastic resistance/plastic resistance of the composite cross-section) of the top floor column should be at least 0.25. For fire resistance design, the steel contribution ratio of the top floor columns, those on the floor below the top floor, and those two floors below the top floor, should not be less than 0.5, 0.33, and 0.25 respectively.
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New insights into the mechanism of Load Introduction into concrete-filled steel tubular column through shear connection
Engineering Structures, 2014Co-Authors: Mohammad Hassan Mollazadeh, Yong WangAbstract:This paper presents the results of an extensive numerical and analytical study to re-investigate the mechanism of Load Introduction into concrete-filled tubular column through shear connection. The new mechanism of Load Introduction revealed from this research indicates that the shear Load from the connection is introduced through the column length above and within the connection. This is different from the currently assumed mechanism of Load Introduction from underneath the connection. In fact, a simple free-body diagram analysis would demonstrate that the currently assumed Load Introduction mechanism is not possible. The results of the numerical simulations also indicate that the Load Introduction length above the connection is unlimited and can be as long as the entire column height. Based on the new Load Introduction mechanism and the numerical simulation results, the maximum amount of Load introduced into the concrete core can be calculated as the bond strength multiplying the entire steel tube/concrete core contact surface area for the entire column length above and including the connection. Under the new Load Introduction mechanism and using representative values of column dimensions and concrete cylinder strength, it has been demonstrated that complete Load Introduction can be achieved in almost all practical arrangements of concrete filled tubular construction.
Mohammad Hassan Mollazadeh - One of the best experts on this subject based on the ideXlab platform.
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New Mechanism of Load Introduction into Concrete-Filled Steel Tubular Columns
Journal of Structural Engineering, 2016Co-Authors: Mohammad Hassan Mollazadeh, Yong WangAbstract:AbstractThis paper presents the results of new Load-Introduction tests and numerical simulations to investigate the mechanism of Load Introduction from shear connections to concrete-filled steel tubular (CFST) columns, and the effectiveness of changing different construction details. The results of the tests have confirmed the authors’ recently proposed new Load-Introduction mechanism, obtained from an extensive numerical study. In the new Load-Introduction mechanism, the connection Load is introduced to the concrete core via the column length above and within the connection or the cap plate on top of the column. There is no limit to the Load-Introduction length above the connection. Below the connection, there is transfer of forces from the steel tube to the concrete core, but the total force in the column remains unchanged. This Load Introduction mechanism is different from that assumed in the various current design codes. This study has an important implication for CFST column design: using shear conne...
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Design implications of a new Load Introduction mechanism into concrete-filled steel tubular columns
Structures, 2016Co-Authors: Mohammad Hassan Mollazadeh, Yong WangAbstract:Abstract This paper presents the design implications of a new Load Introduction mechanism into concrete-filled steel tubular columns (CFST) proposed by the authors recently. According to the new Load Introduction mechanism, the beam-column connection Load is introduced into the composite column through the column length above and within the connection. Based on the new Load Introduction mechanism, for slender CFST column design, a “concrete strength reduction factor” should be used to account for incomplete Load Introduction, when calculating the CFST column cross-section flexural stiffness. For CFST columns under combined axial compression and bending, the concrete strength reduction factor should be used when calculating the compression resistance, but should be ignored when calculating the bending resistance because composite action is always guaranteed for bending of the CFST column. The most important implication of the new Load Introduction mechanism is that the concrete core above the connection should be designed to resist the additional compressive force introduced to the concrete core below the connection. A further implication is that for ambient temperature design, the steel contribution ratio (steel section plastic resistance/plastic resistance of the composite cross-section) of the top floor column should be at least 0.25. For fire resistance design, the steel contribution ratio of the top floor columns, those on the floor below the top floor, and those two floors below the top floor, should not be less than 0.5, 0.33, and 0.25 respectively.
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Load Introduction into concrete-filled steel tubular columns
2015Co-Authors: Mohammad Hassan MollazadehAbstract:Concrete-Filled Steel Tubular (CFST) columns are increasingly being used because of their many advantages, including high strength, high ductility, and higher fire resistance than conventional steel or concrete columns of the same size. In order to maximise the advantages of CFST column, composite action of the column should be ensured. In realistic structures, the Load is not directly applied to the entire CFST column section and is introduced from the beam-column connection. Simple shear connections, which are usually preferred in constructions, are only connected to the external face of the steel tube and there is an issue about how this Load is introduced to the concrete core, through the bond at the steel/concrete interface. There are fundamental errors in the Load Introduction mechanism assumed in various current design methods. Furthermore, based on this erroneous Load Introduction mechanism, construction methods, such as placing shear connectors inside the steel tube or using through-column plates, are recommended to ensure complete Load Introduction. However, these methods are either impractical or uneconomical.The aim of this project, therefore, is to develop a thorough understanding of the Load Introduction mechanism and to use the new insights to assess design implications, for both ambient temperature and fire safety design. The research has been conducted through physical testing, extensive numerical modelling and detailed analytical derivations.A series of new Load Introduction tests, in which square CFST columns are Loaded through simple fin plate connections, are carried out. These tests are designed to investigate the effects of changing column lengths below and above the connection, the effectiveness of using shear connectors inside the steel tube below the connection (according to Eurocode 4) and using a cap plate on the column top for Load Introduction into the concrete core. The test results indicate that the connection Load is introduced to the concrete core through the column length above and within the connection or the cap plate on top of the column. This is different from the currently assumed mechanism of Load Introduction which assumes that Load Introduction occurs from underneath the connection. Below the connection, there is transfer of forces from the steel tube to the concrete core, but the total force in the column remains unchanged. Consequently, using shear connectors below the connection is ineffective in increasing CFST column strength, as has been demonstrated by the tests.The physical tests are supplemented by an extensive numerical parametric study to check whether the conclusions are applicable to different design conditions and to provide data for development of a new design method. The parameters include: section geometry (square, circular, and rectangular), position of Load application to CFST column, dimensions of the square column cross-section, steel tube thickness, connection length, column length above the connection, column length below the connection, and maximum bond stress at the steel-concrete interface. The numerical simulation results confirm the experimental observations. Furthermore, the numerical simulation results indicate that the entire column length and the entire perimeter of the steel-concrete interface above and within the connection are engaged in Load Introduction. Based on the experimental and numerical simulation results, a simple calculation method has been proposed to calculate the column cross-section resistance under compression. According to this equation, the concrete compression resistance to the composite column is the minimum of the plastic resistance or the bond strength within and above the connection. This gives rise to a ?concrete strength reduction factor? to account for incomplete Load Introduction, being the ratio of the Load introduced to the concrete core through the interface bond to the concrete plastic resistance. Based on the new Load Introduction calculation method and using representative values of column dimensions and concrete cylinder strength, it has been demonstrated that complete Load Introduction can be achieved in almost all practical arrangements of concrete-filled tubular construction. For slender CFST column design, this concrete strength reduction factor should also be used to calculate the CFST column cross-section flexural stiffness. For a CFST column under combined axial compression and bending, the concrete strength reduction factor should be used when calculating the compression force, but should be ignored when calculating the bending resistance because composite action is not necessary for bending of the CFST column. The new Load Introduction mechanism induces additional compression in the concrete core and possible tension in the steel tube above the connection. Therefore, the concrete core of the column above the connection in multi-storey construction should be designed to resist the additional compression force. For the steel tube, in ambient temperature design, the steel contribution ratio (steel section resistance/plastic resistance of composite cross-section) of the top floor column should be at least 0.25. For fire resistance design, the steel contribution ratio of the top floor columns, those on the floor below the top floor, and those two floors below the top floor, should not be less than 0.5, 0.33, and 0.25 respectively.
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New insights into the mechanism of Load Introduction into concrete-filled steel tubular column through shear connection
Engineering Structures, 2014Co-Authors: Mohammad Hassan Mollazadeh, Yong WangAbstract:This paper presents the results of an extensive numerical and analytical study to re-investigate the mechanism of Load Introduction into concrete-filled tubular column through shear connection. The new mechanism of Load Introduction revealed from this research indicates that the shear Load from the connection is introduced through the column length above and within the connection. This is different from the currently assumed mechanism of Load Introduction from underneath the connection. In fact, a simple free-body diagram analysis would demonstrate that the currently assumed Load Introduction mechanism is not possible. The results of the numerical simulations also indicate that the Load Introduction length above the connection is unlimited and can be as long as the entire column height. Based on the new Load Introduction mechanism and the numerical simulation results, the maximum amount of Load introduced into the concrete core can be calculated as the bond strength multiplying the entire steel tube/concrete core contact surface area for the entire column length above and including the connection. Under the new Load Introduction mechanism and using representative values of column dimensions and concrete cylinder strength, it has been demonstrated that complete Load Introduction can be achieved in almost all practical arrangements of concrete filled tubular construction.
Axel S. Herrmann - One of the best experts on this subject based on the ideXlab platform.
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Analysis of open-hole-tension plates made of short fibre thermoplastic and reinforced with continuous fibre tailored inserts:
Journal of Thermoplastic Composite Materials, 2020Co-Authors: Katharina Arnaut, M. Adli Dimassi, Bernd Romahn, Ufuk Atilla, Axel S. HerrmannAbstract:In the present paper, the influence of tailored Load Introduction inserts applied to a bolt-Loaded open-hole injection plate with different short glass fibre content is investigated. The tailored l...
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Tailored Inserts Based on Continuous Fibre for Local Bearing Reinforcement of Short Fibre Thermoplastic Components
Key Engineering Materials, 2017Co-Authors: Katharina Arnaut, Axel S. HerrmannAbstract:The injection molding process is an economical process for manufacturing of thermoplastic components. Complex geometries can be realized with high automation and short cycle times. However the mechanical properties of injection-molded parts are not suitable for mechanical demanding components even by adding short or long fibre. As bold connections are used frequently for Load transfer, the Load Introduction area particularly is limited by low bearing strength. The present paper shows the influence of tailored inserts based on continuous fibre on the bolt-Loaded hole of injected test specimen.
Werner Sobek - One of the best experts on this subject based on the ideXlab platform.
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Second-Generation Implants for Load Introduction into Thin-Walled CFRP-Reinforced UHPC Beams: Implant Optimisation and Investigations of Production Technologies
Materials (Basel Switzerland), 2019Co-Authors: Benjamin Kromoser, Oliver Gericke, Mathias Hammerl, Werner SobekAbstract:Combining two high-performance materials—ultra-high-performance concrete (UHPC) as the matrix and carbon-fibre-reinforced composites (CFRP) as the reinforcement—opens up new possibilities for achieving very lightweight thin-walled concrete elements. This strategy, however, leads to a higher degree of material utilisation, resulting in the generation of higher forces around Load Introduction points and supports. The authors present a solution for increasing the performance of supports of very slender CFRP-reinforced UHPC beams by using metal implants. Implants are used in place of concrete in regions of stress concentrations and significant deviation forces. These are able to transfer high stresses and forces efficiently due to their ability to sustain both tension and compression in equal measure. A key issue in their development is the interface between the reinforced concrete and metal implant. Building on previous research, this paper deals with the conceptual design of three types of implants manufactured from different metals and with three different types of automated production technologies (water-jet cutting, metal casting with a 3D-printed plastic formwork and binder jetting of steel components). For this paper, tests were carried out to determine the Load-bearing behaviour of beams with the three different types of support implants used for Load Introduction at the supports. A carbon rod served as bending reinforcement and a pre-formed textile reinforcement cage served as shear and constructive reinforcement.
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Implants for Load Introduction into thin-walled CFRP-reinforced UHPC beams
Composite Structures, 2018Co-Authors: Benjamin Kromoser, Oliver Gericke, Werner SobekAbstract:Abstract Combining two high-performance materials – viz. ultra-high performance concrete (UHPC) as the matrix, and carbon fibre reinforced polymers (CFRP) as the reinforcement – opens up new possibilities of achieving concrete elements with thin walls and minmial weight. This strategy, however, results in a higher degree of material utilisation, which impedes Load transfer from such thin-walled concrete elements to auxiliary constructions such as superordinate Load-bearing systems. The authors present a solution for the Load transfer from very slender CFRP-reinforced UHPC beams to its supports via steel implants (Sobek and Mittelstadt, 2012; Kobler, 2013; Mittelstadt, 2015). In this paper, the conceptual design of three different types of implants is presented. The geometry of the implant and especially the connection of the CFRP reinforcement to the steel implant are examined in detail. For this paper the authors tested beams with three different types of implants and three different configurations of the textile CFRP reinforcement serving as structural and shear reinforcement.
Leif A Carlsson - One of the best experts on this subject based on the ideXlab platform.
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evaluation of the plate twist test to characterize mode iii fracture of sandwich panels with a face core interface crack
Engineering Fracture Mechanics, 2013Co-Authors: Adrian Hernandezperez, F Aviles, Leif A CarlssonAbstract:Abstract Sandwich panels with a face/core interface edge crack Loaded in torsion have been analyzed using finite element analysis (FEA) and experimental testing to characterize mode III delamination propagation. Symmetric sandwich panels with steel face sheets bonded to a high density (H250) PVC foam core were considered. The test specimens were square plates of side length of 90 mm with 3 mm thick face sheets and core thicknesses of 3, 12 and 25.4 mm supported at two corners and Loaded in torsion by application of transverse Loads at two diagonally opposite corners. The energy release rate (G) was determined from stress intensity factors calculated from the crack flank displacements. The results show dominant mode III crack Loading. The mode III component of the energy release rate (GIII) was nearly uniform along the central region of the crack front and mode II contribution was only significant near the Load Introduction and support pins. The measured and calculated compliance for the sandwich panels examined agreed reasonable. The fracture toughness (Gc) determined from measured critical Loads and the compliance calibration method was 119 ± 27 J/m2.
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Flexural analysis of discontinuous tile core sandwich structure
Composite Structures, 2012Co-Authors: K.s. Alfredsson, Leif A Carlsson, Anis Gawandi, John W. Gillespie, Travis A. BogettiAbstract:Three-point flexure Loading of sandwich beams with a core consisting of discrete ceramic tiles (DTSS) is considered. The tile gaps may be bonded or unbonded (open gaps). The analysis utilizes a layer-wise beam theory approach. The general formulation for the displacements and stresses in the face sheets, face/core adhesive layer, and core is derived. Solutions for stresses and displacements of the beam constituents are obtained from finite element formulation based on analytical solution of the face sheet/tile unit cell. The approach is verified by comparison to stress results obtained from ordinary finite element analysis where each layer is modeled discretely. Effects of Load Introduction and support conditions on the effective flexural stiffness are examined. It is demonstrated that the face sheets experience substantial stress concentrations at the tile joint locations, especially if the gaps are unfilled. Analysis of beam compliance reveals sensitivity to details of Load Introduction and support conditions, especially when the span length becomes comparable to the tile length.
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Investigation of the Sandwich Plate Twist Test
Experimental Mechanics, 2008Co-Authors: F Aviles, Leif A Carlsson, G. Browning, K. MillayAbstract:Analysis and test results for the compliance of the sandwich plate twist test are presented. The analysis utilizes classical laminated plate theory (CLPT) and finite element analysis (FEA). It is shown that CLPT greatly underestimates the plate compliance, except when very stiff cores and compliant face sheets are used, as a result of transverse core shear deformation, not accounted for in this theory. Parametric studies are conducted using FEA to examine the influence of transverse shear moduli of the core and specimen dimensions on the plate compliance. The influences of indentation at Load Introduction and support locations, and overhang (oversized panel) are also examined. A test fixture is designed where two diagonally opposite corners of the panel are Loaded, while the other two corners are supported to provide twisting deformation of the panel. Tests were conducted on square sandwich panels consisting of aluminum face sheets over various PVC foam cores. CLPT was found to greatly underestimate the experimental plate compliance. Finite element predictions of the plate compliance were in much closer agreement with the experimental data.
