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Ben Young - One of the best experts on this subject based on the ideXlab platform.

  • Compressive strengths of concrete-filled double-skin (Circular Hollow Section outer and square Hollow Section inner) aluminium tubular Sections:
    Advances in Structural Engineering, 2019
    Co-Authors: Feng Zhou, Ben Young
    Abstract:

    Experimental and numerical investigations of concrete-filled double-skin aluminium stub column with a Circular Hollow Section as the outer skin and a square Hollow Section as the inner skin are pre...

  • Concrete-filled double-skin aluminum Circular Hollow Section stub columns
    Thin-walled Structures, 2018
    Co-Authors: Feng Zhou, Ben Young
    Abstract:

    Abstract This paper presents experimental and numerical investigations and design of concrete-filled double-skin aluminum stub columns with Circular Hollow Sections (CHS) as both outer and inner skins. A series of tests was carried out to investigate the effects of the geometric dimension of the aluminum CHS and concrete strength on the behaviour and strength of the composite columns. The CHS tubes were fabricated by extrusion using 6061-T6 heat-treated aluminum alloy having nominal 0.2% proof stress of 240 MPa. The structural performance of the composite columns was investigated using different nominal concrete cylinder strengths of 40, 70 and 100 MPa. A non-linear finite element model is developed and verified against the experimental results. The test results and the composite column strengths predicted from the finite element analysis (FEA) were compared with the design strengths to evaluate the reliability of the design rules in the current American specifications for aluminum and concrete structures. Furthermore, design equations were proposed to consider the benefits of the composite columns due to the composite action between the aluminum tubes and concrete. The proposed design equations accurately predicted the ultimate strengths of the concrete-filled double-skin aluminum CHS stub columns.

  • Design of cold-formed stainless steel Circular Hollow Section columns using direct strength method
    Engineering Structures, 2018
    Co-Authors: Yuner Huang, Ben Young
    Abstract:

    Abstract Cold-formed stainless steel Circular Hollow Section (CHS) columns have been increasingly used in construction, due to its aesthetic appearance, long life-span and good ductility. It is shown that direct strength method (DSM) is capable of predicting cold-formed steel column strengths accurately. However, the DSM is developed for cold-formed steel Sections with plate rather than curved elements, and thus its applicability for cold-formed stainless steel CHS is worth investigating. This paper presents a numerical investigation of cold-formed stainless steel CHS columns. A non-linear finite element model was developed and verified against column tests. Extensive parametric study of cold-formed duplex, lean duplex and ferritic stainless steel CHS columns has been performed to obtain column strengths. A total of 273 experimental and numerical cold-formed stainless steel CHS column strengths, which are obtained from previous researches and parametric study obtained from this study, are compared with the design strengths predicted by the current DSM. Reliability analysis was performed to evaluate the reliability of the design rules. It is shown that the current DSM provides unconservative and not reliable prediction for cold-formed stainless steel CHS columns. Therefore, modified DSM is proposed for cold-formed stainless steel CHS columns. It is shown that the modified design rule is more accurate than the current DSM, and the modified design rule is considered to be reliable.

  • Numerical analysis and design of concrete-filled aluminum Circular Hollow Section columns
    Thin-walled Structures, 2011
    Co-Authors: Feng Zhou, Ben Young
    Abstract:

    Abstract This paper presents numerical investigation and design of concrete-filled aluminum Circular Hollow Section (CHS) columns. A non-linear finite element model is developed and verified against experimental results. An extensive parametric study was carried out to study the effects of cross-Section geometries and material properties on the concrete-filled aluminum CHS column strengths. A total of 192 numerical data is presented in this study. The aluminum CHS tubes of normal strength material (T5) and high strength material (T6) using three different nominal concrete cylinder strengths of 40, 70 and 100 MPa were investigated. The nominal outer diameter-to-thickness ( D / t ) ratio of the Sections ranged from 10 to 160. The test and numerical results of the concrete-filled aluminum CHS columns were compared with the design strengths to evaluate the reliability of the design rules in the American and Australian/New Zealand specifications for aluminum and concrete structures. Furthermore, the composite column design equations are proposed in this study. The proposed design equations consider the benefits of composite action between the aluminum CHS tube and the concrete infill. It is shown that the proposed design equations accurately predicted the strengths of the concrete-filled aluminum CHS columns.

  • Concrete-filled aluminum Circular Hollow Section column tests
    Thin-walled Structures, 2009
    Co-Authors: Feng Zhou, Ben Young
    Abstract:

    An experimental investigation of concrete-filled aluminum Circular Hollow Section (CHS) stub columns is presented in this paper. A series of tests was conducted to investigate the effects of the geometric dimension of the aluminum CHS and concrete strength on the behavior and strength of concrete-filled aluminum CHS stub columns. The structural performance of the concrete-filled aluminum CHS stub columns was investigated using different concrete cylinder strengths of 40, 70 and 100 MPa. The CHS tubes were fabricated by extrusion using 6061-T6 heat-treated aluminum alloy having nominal 0.2% proof stress of 240 MPa. The diameter-to-thickness ratio of the CHS tubes ranged from 9.7 to 59.7. The column lengths were chosen so that the length-to-diameter ratio generally remained at a constant value of 3 to prevent overall column buckling. The concrete-filled aluminum CHS specimens were subjected to uniform axial compression. The column strengths, load-axial shortening relationship, load-axial strain relationship and failure modes of columns were presented. The test strengths were compared with the design strengths calculated using the American specifications and Australian/New Zealand standards for aluminum and concrete structures. It is shown that the design strengths are generally conservative for concrete-filled aluminum CHS stub columns.

Xiao Ling Zhao - One of the best experts on this subject based on the ideXlab platform.

  • Experimental and numerical investigation on behavior of CFRP-strengthened Circular Hollow Section gap K-joints
    Thin-walled Structures, 2016
    Co-Authors: Lewei Tong, Xiao Ling Zhao
    Abstract:

    Abstract An efficient technique of Carbon Fiber Reinforced Polymer (CFRP) application was proposed to promote joint capacity of general tubular K-joints fabricated from Circular Hollow Section (CHS) members. Using this technique, in order to understand the static performance of CFRP-strengthened CHS joints, a systematic investigation was carried out by means of both experiments and finite element method. Three CHS gap K-joints strengthened with CFRP sheets were tested under static axial force in braces, whilst one additional joint was served as reference joint without CFRP. The results of failure modes, deformation, Mises stress, strain intensity and load-bearing capacity of the joints were presented and compared. A series of finite element models were developed and validated for the joints with and without CFRP reinforcement. A parametric study was conducted to evaluate the effect of variables (length, layers and mechanical properties of CFRP) on load-bearing capacity. The research results revealed that the proposed technique of CFRP installation was efficient to promote performance of in-service CHS gap K-joints. Moreover, the layer of CFRP sheets has significant effect on load-bearing capacity, but the effect was negligible for either length or mechanical properties of CFRP sheets. Finally, formulas were proposed for calculating ultimate load-bearing capacity of CHS gap K-joints with CFRP composites, and their calculation results matched well with the experimental and numerical results respectively.

  • Stress-Concentration Factors in Circular Hollow Section and Square Hollow Section T-Connections: Experiments, Finite-Element Analysis, and Formulas
    Journal of Structural Engineering-asce, 2013
    Co-Authors: Lewei Tong, Fidelis Rutendo Mashiri, Hong-zhi Zheng, Xiao Ling Zhao
    Abstract:

    AbstractNodal T-connections made up of Circular Hollow Section (CHS) braces and square Hollow Section (SHS) chords (CHS-SHS T-connections) have the advantage that they do not require complex brace end preparation when compared with CHS-CHS T-connections. The stress-concentration factors (SCFs) in CHS-SHS T-connections have also been found to be lower than those in SHS-SHS T-connections by previous researchers. At present, no parametric equations have been developed for determination of SCFs for the design of CHS-SHS T-connections. In this investigation, eight CHS-SHS T-connections with unique nondimensional parameters were strain gauged for determination of strain-concentration factors (SNCFs) and therefore SCFs. A three-dimensional finite-element model was then developed using the ANSYS software to simulate the stress distribution at the brace-chord welded interface under axial force and in-plane bending in the brace. Validation of the model was carried out by comparing the SNCFs determined from the expe...

  • Fatigue Behavior of Welded T-Joints with a CHS Brace and CFCHS Chord under Axial Loading in the Brace
    Journal of Bridge Engineering, 2013
    Co-Authors: Ke Wang, Lewei Tong, Xiao Ling Zhao, Fidelis Rutendo Mashiri
    Abstract:

    AbstractThe welded truss composed of Circular Hollow Section (CHS) braces and concrete-filled Circular Hollow-Section (CFCHS) chords is a new kind of structural system that has been increasingly applied in large span arch bridges in China. It is necessary to have a good knowledge of fatigue strength of the welded CHS-to-CFCHS joints for the design of this kind of composite bridge. This paper reports on a series of tests on welded CHS-to-CFCHS T-joints subjected to axial cyclic fatigue loading in the brace. Eleven joints were designed to investigate various influence factors such as different nondimensional geometric parameters of Circular Hollow Sections and different concrete strength grades. The quality of welds connecting brace and chord members were examined using the magnetic particle and radiographic inspection methods. The conditions of hot spot stress at both the crown and saddle positions in brace and chord members were determined by means of linear and nonlinear extrapolation methods. During the...

  • concrete filled double skin steel tubular cfdst beam columns subjected to cyclic bending
    Engineering Structures, 2006
    Co-Authors: Hong Huang, Zhong Tao, Xiao Ling Zhao
    Abstract:

    Abstract In recent years, it was proposed by several researchers that concrete filled double skin steel tubes (CFDST) be studied for their strength as a column or a beam. Advantages of CFDST over fully concrete filled steel tubes (CFST) include: increase in Section modulus; enhancement in stability; lighter weight; better damping characteristics and better cyclic performance. It is thus expected that concrete filled double skin steel tubes (CFDST) have the potential of being used in building structures. This paper provides new test data pertaining to the seismic behavior of CFDST beam–columns. The test parameters included the Section types (Circular and square), the core concrete strength ( f cu ) , and the axial load level ( n ) . Twenty-eight CFDST column specimens, including 16 specimens with SHS (square Hollow Section) outer and CHS (Circular Hollow Section) inner, 12 specimens with CHS (Circular Hollow Section) outer and CHS (Circular Hollow Section) inner were tested under constant axial load and cyclically increasing flexural loading. The CFDST beam–columns were found to have significant increase in strength, ductility, and dissipated energy over the outer jackets. In general, the ductility and energy dissipation ability of specimens with Circular Sections are higher than those of the specimens with square Sections. The mechanics model which was developed by the authors for concrete filled steel tubular (CFST) beam–columns subjected to constant axial load and cyclically increasing flexural loading, is used to analyze the behavior of CFDST beam–columns. It is found that the predicted cyclic responses for the composite beam–columns are generally in reasonable agreement with test results. Finally, comparisons are made with predicted beam–column flexural stiffness using the existing codes.

  • thin Circular Hollow Section to plate t joints stress concentration factors and fatigue failure under in plane bending
    Thin-walled Structures, 2006
    Co-Authors: Fidelis Rutendo Mashiri, Xiao Ling Zhao
    Abstract:

    Welded thin-walled (t<4 mm) tube-to-plate T-joints made up of cold-formed Circular Hollow Sections welded onto a plate to form a moment resistant connection are used in the road transport and agricultural industry to manufacture equipment and other structural systems. Fatigue design of these joints is not available in current standards. An understanding of the stress concentrations and failure in these connections is therefore necessary as a step towards understanding the fatigue behaviour of these connections. Stress concentration factors (SCFs) of welded thin-walled (t<4 mm) Circular Hollow Section (CHS)-to-plate T-joints are determined at different locations along the weld toes on the tubular brace. The distribution of SCFs along the weld toes shows that the highest SCF occurs at the weld toes in the Circular brace at the 0° line. The ratio of the end of test fatigue life (N4) to the through-thickness fatigue life (N3) in the thin CHS-plate T-joints is found to fall within the range of N4/N3 found in previous research of both thick and thin-walled joints. Surface crack growth monitoring is used to obtain an approximation of the length of surface crack at the point of occurrence of a through-thickness crack. The relationship between surface crack length and the occurrence of a through-thickness crack is important in that it can be used as a measure of the criticality of a surface crack during structural health monitoring of equipment or structures.

Ran Feng - One of the best experts on this subject based on the ideXlab platform.

  • Behaviour of Concrete-Filled Double-Skin Circular Hollow Section Cross Joints Under Axial Compression
    International Journal of Steel Structures, 2018
    Co-Authors: Yu Chen, Ran Feng
    Abstract:

    This paper presents an experimental investigation on concrete-filled double-skin Circular Hollow Section (CHS) cross joints under axial compression. A total of twenty-two right-angled CHS cross joints with different brace to chord diameter ratio (β), inner tube to outer tube thickness ratio of chord (ω) and Hollow ratio of chord (χ) were tested, in which eighteen concrete-filled double-skin CHS cross joints were studied for different shapes of inner tube of chord, two traditional empty CHS cross joints and two traditional concrete-filled CHS cross joints were tested for comparison. The joint strengths, failure modes, load-deformation curves and strain distribution curves of all specimens are reported. The effects of brace to chord diameter ratio (β), inner tube to outer tube thickness ratio of chord (ω), Hollow ratio of chord (χ), shape of inner tube of chord and concrete strength on the behaviour of concrete-filled double-skin CHS cross joints under axial compression were evaluated. It is shown from the comparison that the ultimate load and initial stiffness of CHS cross joints are significantly enhanced by strengthening the chord member with inner tube and concrete infill. Furthermore, the ultimate strengths are increased with the increase of the β ratio, whereas the ultimate strengths are decreased with the increase of the χ ratio for all types of concrete-filled double-skin CHS cross joints. On the other hand, the ultimate strengths are enhanced with the increase of the ω ratio and concrete strength for all types of concrete-filled double-skin CHS cross joints, but the enhancement is insignificant. The corresponding finite element analysis was also performed and calibrated against the test results. The design equations are proposed based on the test and finite element analysis results for concrete-filled double-skin CHS cross joints, which are verified to be more accurate.

  • Flexural behavior of concrete-filled aluminum alloy Circular Hollow Section tubes
    Construction and Building Materials, 2018
    Co-Authors: Yu Chen, Ran Feng, Wenzhi Gong
    Abstract:

    Abstract This paper presents an experimental investigation on flexural behavior of concrete-filled aluminum alloy Circular Hollow Section (CHS) tubes under pure in-plane bending. A total of 28 Circular concrete-filled aluminum alloy tubes (CFAT) with nominal concrete cube strengths of 30 MPa and 50 MPa were tested. The flexural strengths, failure modes, flexural stiffness, ductility, bending moment versus mid-span deflection curves, overall vertical deflection curves, bending moment versus longitudinal strain curves and longitudinal strain distribution curves of Circular CFAT beams are reported. It is demonstrated that the comparatively large wall thickness of aluminum alloy CHS tube enhanced the bearing capacity, the bending deformation capacity and the ductility of Circular CFAT beams. Whereas, the concrete strength generally has insignificant influence on the flexural strength, flexural stiffness and ductility of Circular CFAT beams. The current design specifications for the CFST are generally inappropriate for Circular CFAT beams under pure in-plane bending with high scatter of predictions. Further research is still required to propose accurate design rules for Circular CFAT beams.

  • Tests of concrete-filled Circular Hollow Section X-joints with curved chord under in-plane bending:
    Advances in Structural Engineering, 2017
    Co-Authors: Yu Chen, Ran Feng
    Abstract:

    This article presents the static tests on bare and concrete-filled Circular Hollow Section X-joints with curved chord under in-plane bending. A total of 16 specimens were fabricated by hot-rolled b...

  • Bond-slip behaviour of concrete-filled stainless steel Circular Hollow Section tubes
    Journal of Constructional Steel Research, 2017
    Co-Authors: Yu Chen, Ran Feng, Yongbo Shao, Xiaotian Zhang
    Abstract:

    This paper presents the repeated push-out tests on concrete-filled stainless steel Circular Hollow Section (CHS) tubes with different values of height-to-diameter ratio, diameter-to-thickness ratio and concrete strengths. The bond-slip behaviour of all specimens and the strain distribution on the exterior of stainless steel tubes along the longitudinal height direction were carefully investigated. It was found that the shear failure loads of bonding slip decreased successively with more loading cycles of the repeated push-out test employed in the same direction. Hence, the mechanical interlock force and friction force of the interface elements gradually decreased. Furthermore, the bond-slip failure of the interface elements between the inner concrete and outer stainless steel tube of the specimens consists of the adhesive stage, the sliding stage and the friction resistant stage. It can be generally concluded that 70% of the shear resistance of the bonding strength is taken by the interface friction force, while the remaining 30% of the shear resistance of the bonding strength is sustained by the chemical adhesive force and the mechanical interlock force. On the other hand, it was demonstrated that the height-to-diameter ratio (H/D) and the diameter-to-thickness ratio (D/t) of the stainless steel tube as well as the concrete strength (C) have insignificant influence on the shear resistance of the bonding strength of the interface elements. It was also shown from the comparison that the current design rules of concrete-filled carbon steel CHS tubes are inapplicable to the shear resistance of the bonding strength of concrete-filled stainless steel CHS tubes.

  • Experimental study of concrete-filled multiplanar Circular Hollow Section tubular trusses
    Thin-walled Structures, 2015
    Co-Authors: Yu Chen, Ran Feng
    Abstract:

    Abstract This paper presents an experimental study on concrete-filled multiplanar tubular trusses made of Circular Hollow Section (CHS) members. A total of four types of concrete-filled multiplanar tubular trusses including Triangular truss (TT), Inverse-Triangular truss (IT), Square truss (ST) and Trapezoid truss (TZ) were tested under static loading. The failure mode, load carrying capacity, overall deflection and strain intensity of all specimens are reported. The effects of top and bottom chord members, straight and diagonal brace members and lateral bracings on the load carrying capacity, flexural rigidity and ductility of all specimens were also investigated. The typical failure modes observed from the tests include the local buckling of straight brace members, the surface plasticity and shear failure of the bottom chord members, the weld fracture around tubular joints at the bottom chord members, and the end support failure of the top chord member. The load carrying capacity, flexural rigidity and ductility of different types of multiplanar tubular trusses made of identical CHS members are quite different due to the remarkable changes of the mechanical behaviour of CHS members. On the other hand, the lateral bracings play different roles under different load levels in enhancing the load carrying capacity of different types of multiplanar tubular trusses. It is demonstrated from the comparison that the Inverse-Triangular truss (IT) has optimum flexural rigidity, ductility and efficiency in practice.

Kohoutková Alena - One of the best experts on this subject based on the ideXlab platform.

  • To shear failure of steel and fibre-reinforced concrete Circular Hollow Section composite column at elevated temperature
    'Universitat Politecnica de Valencia', 2018
    Co-Authors: Arha Tesfamariam, Křístek Vladimir, Tretyakov Alexey, Blesak Lukas, Tkalenko Illia, Wald Frantisek, Stefan Radek, Novak Josef, Kohoutková Alena
    Abstract:

    [EN] This study predicts the shear strength of steel fibre reinforced concrete (SFRC) members at elevated temperature using numerical modelling. The authors derived the stress-strain relation in the pure shear mode at ambient temperature based on a damage model calibrated at ambient and elevated temperatures. The model was validated on the special experimental arrangement for the pure shear mode of the SFRC in torsion. These results enables to determine the stress-strain diagram at elevated temperature. The shear strength of SFRC is compared with the compressive and tensile strength and used to observe reasons for experimentally observed failure model. The work is a part of comprehensive project focused on development of design models for the steel and SFRC composite columns with Circular Hollow Section (CHS) at elevated temperature. Research includes two levels accuracy/complexity, allowing simplified or advanced approach to design following the coming changes in European standard for composite member design in fire, EN1994-1-2:2021. Experimental studies of the project include mechanical material tests of heated fibre-concrete samples in tension and compression, thermal uniform and non-uniform tests of insulated fragments of CHS and tests of full scale SFRC CHS columns in steady-state and transient-state regimes. Developing advanced FEM simulation of global mechanical behaviour of SFRC CHS columns is a multi-levelled composite mechanical and thermo-model and provide numerous numerical experiments. Together with steel material model in fire, validated FEM model of mechanical behaviour of fibre-reinforce concrete at elevated temperature is performed. Validated simplified and advanced thermal model of SFRC in CHS at elevated temperature gives temperature fields and moisture distribution inside Section which depends on direction, heat flux, sizes and gives possibility to model different fire cases of full-scale columns in bending, shear, and buckling at elevated temperature. Proposed analytical and simplified FEM mechanical model of column is taking into account degradation of mechanical properties, analytical models of transfer of heat inside the column Section and provides simple solutions for designers.This publication was supported by grant of Grant Agency Czech Republic, No. 15-19073S, Models of steel and fibre concrete composite columns exposed to fire.Arha, T.; Křístek, V.; Tretyakov, A.; Blesak, L.; Tkalenko, I.; Wald, F.; Stefan, R.... (2018). To shear failure of steel and fibre-reinforced concrete Circular Hollow Section composite column at elevated temperature. En Proceedings of the 12th International Conference on Advances in Steel-Concrete Composite Structures. ASCCS 2018. Editorial Universitat Politècnica de València. 863-869. https://doi.org/10.4995/ASCCS2018.2018.7201OCS86386

  • 10.19: The steel and fibre‐reinforced concrete Circular Hollow Section composite column exposed to fire
    ce papers, 2017
    Co-Authors: Tkalenko Illia, Tretyakov Alexey, Wald Frantisek, Stefan Radek, Novak Josef, Kohoutková Alena
    Abstract:

    The recent development in technology of production and transport of the steel fibre-reinforced concrete enables its utilization in composite steel-concrete structures. This work is focused on development of mechanical behaviour and design model of Circular Hollow Section (CHS) composite steel and fibre-concrete (SFRC) column at elevated temperature. Research includes two levels accuracy/complexity, allowing simplified or advanced approach to design following the coming changes in European standard for composite member design in fire (EN1994-1-2:2005) [1]. Experimental studies of the project include mechanical tests of heated fibre-concrete samples in tension and compression, thermal behaviour under uniform and non-uniform loading of stubs of CHS and tests of full scale SFRC CHS columns in steady-state and transient-state regimes. Developing advanced finite element method (FEM) simulation of global mechanical behaviour of SFRC CHS columns is a multi-levelled composite mechanical and thermo-model and provide numerous numerical experiments. Together with standard steel material model in fire, FEM model of mechanical behaviour of fibre-reinforce concrete at elevated temperature is prepared. Validated simplified and advanced thermal model of SFRC CHS at elevated temperature gives temperature fields and moisture distribution inside Section which depends on direction, heat flux, sizes and gives possibility to model different fire cases of full-scale columns in bending and buckling at elevated temperature. Prepared analytical and simplified FEM mechanical model of column is taking in account degradation of mechanical properties, analytical models of transfer of heat inside column Section and provides simplified solutions for designers.

  • 10 19 the steel and fibre reinforced concrete Circular Hollow Section composite column exposed to fire
    ce papers, 2017
    Co-Authors: Tkalenko Illia, Tretyakov Alexey, Wald Frantisek, Stefan Radek, Novak Josef, Kohoutková Alena
    Abstract:

    The recent development in technology of production and transport of the steel fibre-reinforced concrete enables its utilization in composite steel-concrete structures. This work is focused on development of mechanical behaviour and design model of Circular Hollow Section (CHS) composite steel and fibre-concrete (SFRC) column at elevated temperature. Research includes two levels accuracy/complexity, allowing simplified or advanced approach to design following the coming changes in European standard for composite member design in fire (EN1994-1-2:2005) [1]. Experimental studies of the project include mechanical tests of heated fibre-concrete samples in tension and compression, thermal behaviour under uniform and non-uniform loading of stubs of CHS and tests of full scale SFRC CHS columns in steady-state and transient-state regimes. Developing advanced finite element method (FEM) simulation of global mechanical behaviour of SFRC CHS columns is a multi-levelled composite mechanical and thermo-model and provide numerous numerical experiments. Together with standard steel material model in fire, FEM model of mechanical behaviour of fibre-reinforce concrete at elevated temperature is prepared. Validated simplified and advanced thermal model of SFRC CHS at elevated temperature gives temperature fields and moisture distribution inside Section which depends on direction, heat flux, sizes and gives possibility to model different fire cases of full-scale columns in bending and buckling at elevated temperature. Prepared analytical and simplified FEM mechanical model of column is taking in account degradation of mechanical properties, analytical models of transfer of heat inside column Section and provides simplified solutions for designers.

Yongbo Shao - One of the best experts on this subject based on the ideXlab platform.

  • Plastic collapse load prediction of cracked Circular Hollow Section T/Y-joints under in-plane and out-of-plane bending
    Ocean Engineering, 2018
    Co-Authors: Seng Tjhen Lie, Yongbo Shao
    Abstract:

    Abstract The plastic collapse loads of cracked Circular Hollow Section (CHS) T/Y-joints under in-plane and out-of-plane bending are investigated using finite element (FE) analyses. An in-house 3D FE mesh generator is specifically developed to create the mesh models of the cracked joints containing a semi-elliptical surface crack located at the weld toe of the chord. Mesh convergence tests are then carried out to check the accuracy of the generated mesh models. The in-plane and out-of-plane plastic collapse moments of uncracked CHS T/Y-joints are calculated and compared with results obtained from three codes and experimental data. The comparison shows that the plastic collapse moments of uncracked CHS T/Y-joints obtained in this study are accurate and reliable. Subsequently, an extensive parametric study is carried out to investigate the plastic collapse moments of cracked CHS T/Y-joints under in-plane and out-of-plane bending. It is found that the in-plane and out-of-plane plastic collapse moments may decrease by up to 35.1% and 33.6% respectively when the crack area A nc reaches 25% of the interSectional area, t 0 * l w . Finally, two lower bound strength reduction factor F AR equations for cracked CHS T/Y-joints under in-plane and out-of-plane bending are proposed.

  • Bond-slip behaviour of concrete-filled stainless steel Circular Hollow Section tubes
    Journal of Constructional Steel Research, 2017
    Co-Authors: Yu Chen, Ran Feng, Yongbo Shao, Xiaotian Zhang
    Abstract:

    This paper presents the repeated push-out tests on concrete-filled stainless steel Circular Hollow Section (CHS) tubes with different values of height-to-diameter ratio, diameter-to-thickness ratio and concrete strengths. The bond-slip behaviour of all specimens and the strain distribution on the exterior of stainless steel tubes along the longitudinal height direction were carefully investigated. It was found that the shear failure loads of bonding slip decreased successively with more loading cycles of the repeated push-out test employed in the same direction. Hence, the mechanical interlock force and friction force of the interface elements gradually decreased. Furthermore, the bond-slip failure of the interface elements between the inner concrete and outer stainless steel tube of the specimens consists of the adhesive stage, the sliding stage and the friction resistant stage. It can be generally concluded that 70% of the shear resistance of the bonding strength is taken by the interface friction force, while the remaining 30% of the shear resistance of the bonding strength is sustained by the chemical adhesive force and the mechanical interlock force. On the other hand, it was demonstrated that the height-to-diameter ratio (H/D) and the diameter-to-thickness ratio (D/t) of the stainless steel tube as well as the concrete strength (C) have insignificant influence on the shear resistance of the bonding strength of the interface elements. It was also shown from the comparison that the current design rules of concrete-filled carbon steel CHS tubes are inapplicable to the shear resistance of the bonding strength of concrete-filled stainless steel CHS tubes.

  • Fatigue and fracture strength of a multi-planar Circular Hollow Section TT-joint
    Journal of Constructional Steel Research, 2017
    Co-Authors: Seng Tjhen Lie, Yongbo Shao
    Abstract:

    Abstract A multi-planar Circular Hollow Section (CHS) TT-joint with one brace subjected to axial tensile load and the other brace pinned is tested up to failure. The objectives include verifying the accuracy of S-N curves approach for predicting the fatigue life of the uncracked multi-planar CHS TT-joint and calculating the bearing capacity of the cracked multi-planar CHS TT-joint. The stress distributions along the weld toes at the two chord-brace interSection zones are measured first by carrying out a static test. It is found that the hot spot stress is located at one crown position of the chord. Subsequently, fatigue test using the alternating current potential drop (ACPD) technique is conducted to record the crack initiation and propagation through the chord thickness. It is found that crack initiates at the hot spot stress location, and the crack length versus the depth resembles a semi-ellipse in shape. The fatigue life of the TT-joint can be safely predicted using S-N curves incorporated in the CIDECT code. Finally, axial tensile load in displacement control mode is applied incrementally to the loaded brace end until the final failure occurs. Load displacement curve of the cracked TT-joint is recorded during the test. In conjunction with the finite element analysis results, it is found that the bearing capacity of the cracked TT-joint decreases about 28.1% as compared to the corresponding uncracked joint, and it is smaller than the value of 34.5% predicted by using the strength reduction factor F AR recommended in BS7910:2013 + A1:2015 code of practice.

  • plastic collapse load prediction of cracked Circular Hollow Section gap k joints under in plane bending
    Marine Structures, 2016
    Co-Authors: T Li, Yongbo Shao, S P Vipin
    Abstract:

    Abstract This paper reports the in-plane plastic collapse moment of cracked Circular Hollow Section (CHS) gap K-joints containing a semi-elliptical surface crack located at the crown position. An in-house 3D finite element (FE) mesh generator is developed to create all the mesh models automatically. Firstly, in-plane plastic collapse moment applied to the uncracked CHS gap K-joints are investigated. Both Lu’s deformation limit and twice elastic compliance are used to determine the in-plane plastic collapse moment. Consequently, an extensive parametric study is carried out to investigate the in-plane plastic collapse moment of the cracked joints. It is found that the crack has a significant influence on the in-plane plastic collapse moment. The decrease of the in-plane plastic collapse moment is up to 30.4% when the crack area A nc reaches up to 25%. The strength reduction factors of all the analyzed cracked CHS gap K-joints are calculated. Finally, a lower bound reduction factor F AR equation is proposed based on the FE results.

  • Study on fire resistance of Circular Hollow Section (CHS) T-joint stiffened with internal rings
    Thin-walled Structures, 2015
    Co-Authors: Cheng Chen, Yongbo Shao, Jie Yang
    Abstract:

    This paper aims to study the fire resistant performance of Circular Hollow Section (CHS) T-joint stiffened with internal rings under axial compression at elevated temperatures. Experimental study and finite element analysis are combined to carry out the investigation. Two full-scale tubular joints, one is un-stiffened and the other is stiffened with ring-stiffeners, are designed and tested. A constant axial loading is applied at brace end of the joints firstly, and then the joints are heated in accordance with ISO 834 standard heating curve uniformly in an electric heating furnace until failure. It is found that the internal rings enhance the fire resistant performance of CHS T-joint by decreasing the temperature of chord efficiently and prolonging the fire-resistant time. Sequentially, the corresponding finite element models of the two joints are built on basis of the experiments by employing sequentially coupled thermal-stress method. By comparing with the experimental data including temperatures of chord and brace and displacements of crown, saddle and brace end, the finite element models are verified to be accurate and reliable. And then numerical analysis is conducted to investigate the reinforcing efficiency of ring-stiffeners and impact of geometrical parameters (β and γ) on the fire resistant performance of the stiffened joints by adopting the verified modeling method. It is summarized that the failure mode converts with geometrical dimensions of ring-stiffener and geometrical parameters of tubular joint changing.