Experimental and Theoretical Study on the Behavior of Cold-formed Stainless Steel Stub Columns

Gan-Ping Shu,Baofeng Zheng,Xiaoming Shen 한국강구조학회 2013 International Journal of Steel Structures Vol.13 No.1

This paper presents an experimental investigation on the behavior of cold-formed stainless steel stub columns under axial compression. Nineteen hollow section specimens of seven section types were tested. Geometric imperfections, material properties and full-range load-displacement curves were obtained. The test strengths were compared with the four design strengths, which are respectively calculated by using the American specification, the European specification, the design method proposed by Rasmussen in 2004, and the design method proposed by Gardner in 2008. The American specification, the European specification, and the design method proposed by Rasmussen are generally conservative. While the design method proposed by Gardner is relatively accurate. Based on the comparisons, modifications to Winter equation were derived to involve both the factors of the corner enhancement of the cold-formed members and the nonlinear property of stainless steel. The modified Winter equation can predict the strengths with low scatter.

Buckling analysis of elastically-restrained steel plates under eccentric compression

Ying Qin,Gan-Ping Shu,Er-Feng Du,Rui-Hua Lu 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.29 No.3

In this research, the explicit closed-form local buckling solution of steel plates in contact with concrete, with both loaded and unloaded edges elastically restrained against rotation and subjected to eccentric compression is presented. The Rayleigh-Rize approach is applied to establish the eigenvalue problem for the local buckling performance. Buckling shape which combines trigonometric and biquadratic functions is introduced according to that used by Qin <i>et al</i>. (2017) on steel plate buckling under uniform compression. Explicit solutions for predicting the local buckling stress of steel plate are obtained in terms of the rotational stiffness. Based on different boundary conditions, simply yet explicit local buckling solutions are discussed in details. The proposed formulas are validated against previous research and finite element results. The influences of the loading stress gradient parameter, the aspect ratio, and the rotational stiffness on the local buckling stress resultants of steel plates with different boundary conditions were evaluated. This work can be considered as an alternative to apply a different buckling shape function to study the buckling problem of steel plate under eccentric compression comparing to the work by Qin <i>et al</i>. (2018), and the results are found to be in consistent with those in Qin <i>et al</i>. (2018).

Parameters Effect on Predicting Fire Resistance of Ultra-high Strength Concrete Filled Protected Square Steel Tubular Columns

Xiao Lyu,Gan-Ping Shu,Er-Feng Du 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.5

Ultra-high strength concrete (UHSC) with compressive strength greater than 100 MPa at room temperature has been developed for concrete fi lled square steel tubular column for use in high-rise buildings. The fi re resistance of UHSC fi lled protected square steel tubular columns exposed to the standard ISO fi re is investigated in this paper. For this purpose, numerical heat transfer analysis and nonlinear thermal stress analysis were conducted by taking into account the existing material properties, such as the thermal and mechanical properties of UHSC and high strength steel. The numerical analyses were carried out and the results were validated against the test results in terms of heat distribution and mechanical behavior. Comparison with the test results showed a reasonable agreement with fi nite element results in terms of temperature fi eld prediction and load displacement behavior during the fi re. Finally, based on the validated fi nite element model, the eff ects of fi re protection thickness, load ratio, the strengths of concrete and steel, steel contribution ratio, and relative slenderness ratio on the fi re resistance of UHSC fi lled square steel tubular columns were carried out and discussed.

Strength of Double Skin Steel-Concrete Composite Walls

Ying Qin,Gan-Ping Shu,Shenggang Fan,JinYu Lu,Shi Cao,Jian-Hong Han 한국강구조학회 2017 International Journal of Steel Structures Vol.17 No.2

Double skin steel-concrete composite walls have been increasingly used in civil engineering applications. However, the advantages of these walls have not been fully recognized due to the lack of appropriate technical guidelines for capacity design. In this paper, the local buckling strength of steel plate were firstly reviewed in terms of specifications incorporated in several modern codes. A methodology to predict the strength of steel plate with restraint of both concrete and shear studs was proposed based on the explicit solution for local buckling of steel plate in composite shear walls subjected to uniform axial compression and with elastically rotational restraint at loaded and unloaded edges. The results were compared with various previous experimental data and good agreement was observed. Furthermore, the load carrying capacity of composite walls was derived from the superposition of the contribution of steel plate and concrete. The predicted values from the proposed equations, together with the resulted determined from modern codes, were compared with the experimental results. It was found that both the proposed method and JEAG 4618 offer reasonable predictions while AISC 360 and KEPIC-SNG always underestimate the actual values.

Height-thickness ratio on axial behavior of composite wall with truss connector

Ying Qin,Gan-Ping Shu,Xiong-Liang Zhou,Jian-Hong Han,Yun-Fei He 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.30 No.4

Double skin composite walls offer structural and economic merits over conventional reinforced concrete counterparts in terms of higher capacity, greater stiffness, and better ductility. This paper investigated the axial behavior of double skin composite walls with steel truss connectors. Full-scaled tests were conducted on three specimens with different height-to-thickness ratios. Test results were evaluated in terms of failure mode, load-axial displacement response, buckling loading, axial stiffness, ductility, strength index, load-lateral deflection, and strain distribution. The test data were compared with AISC 360 and Eurocode 4 and it was found that both codes provided conservative predictions on the safe side.

Study on Residual Stress Distributions in Press-Braked Stainless Steel Sections

Baofeng Zheng,Gan-Ping Shu,Qinglin Jiang 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.5

The distribution of residual stresses is one of the substantial issues in determining mechanical behaviors of stainless steel structural members. Proper residual stress distribution models are necessary to include the residual stress infl uence in the analysis and design. Currently, the existing residual stress distribution model for press-braked stainless steel sections is either relatively complicated for the application, or only focuses on the longitudinal residual stress. In this study, a simplifi ed residual stress distribution model was proposed based on the analysis of the key mechanisms in the press-braking process that was assumed as two-stage (bending and rebounding) plane strain pure bending process. The stress–strain relationship was represented as a simplifi ed three–stage material model, and all the minor eff ects like the coiling and uncoiling, the material anisotropy, and the shift of neutral axis, etc. were neglected. Compared with test data, the predicted results by the proposed simplifi ed model indicate good agreement for specimens within the commonly used ratio of internal corner radius over the thickness ( r i / t ). Finite element models for the press-braking process were then developed in ABAQUS and validated using the available data from literature. A series of models with varied ratios of r i / t were analyzed. Simulation results indicate that the center of the corner region in the press-braked sections has the largest equivalent plastic strain and residual stresses. From the center to the edge, the equivalent plastic strain and residual stresses declined signifi cantly. As the ratios of r i / t become smaller and smaller, the neutral axis moves towards to the compression side and the proposed simplifi ed model gradually loses its prediction accuracy. Based on the theoretical and fi nite element analysis, the proposed simplifi ed model is applicable for press-braked stainless steel sections with r i / t ratios higher than 2.0.

Material Enhancement Model for Austenitic Stainless Steel Sheets Subjected to Pre-stretching

Baofeng Zheng,Gan-Ping Shu,Rui-Hua Lu,Qinglin Jiang 한국강구조학회 2019 International Journal of Steel Structures Vol.19 No.5

Austenitic stainless steel has considerable strain hardening property, which can be utilized in the design of cold-formed stainless steel structures to eff ectively reduce project costs. Pre-stretching is a simple and fundamental cold-forming process. Material enhancement model developed for pre-stretching lays a basis for characterizing material properties in more complicated cold-forming process(e.g. cold-rolling and press-braking). In this study, a series of material tensile tests were performed to develop material enhancement models for austenitic stainless steel sheets subjected to pre-stretching. Austenitic stainless steel sheets were tensioned in six diff erent levels to introduce cold working into the sheets. Material properties of the sheets in two directions (i.e. along and perpendicular to the pre-stretching direction) were obtained through coupon tensile tests. To facilitate the development of the material enhancement models, a simplifi ed three-stage material model with six independent parameters was proposed. Enhancement model for each material parameter was developed with the plastic strain experienced in the pre-stretching process as a key factor. Key material parameters and full-range stress–strain curves at diff erent levels of pre-stretching were generated based on the proposed and the available predictive models in literatures. Comparisons of the generated material parameters and the stress–strain curves with the test ones show good agreement.

Experimental Study on the Motion Process of Radial Retractable Roof Structures

JinYu Lu,Jie Liao,Gan-Ping Shu,Tao Zhang 한국강구조학회 2016 International Journal of Steel Structures Vol.16 No.4

In recent years, the use of retractable roofs is increasing to meet the demand of holding big-scale events. This article introduces a class of radial retractable roofs based on the foldable bar structure (FBS) mechanism. A radial retractable roof structure whose moveable section consisted of 6 segments and 6 rigid linkages was designed with appropriate parameters. An experimental study of a radial retractable roof was carried out. A scale model with a 3 metre diameter was constructed to study the roof deflection and vibration during the deployment process under four different load cases. Furthermore, based on the multi-flexible body dynamics theory, an ADAMS-ANSYS co-simulation was applied to simulate the motion process of the radial retractable roof structure. The experimental results were consistent with the numerical simulations. This indicates that the dynamic and fluctuation phenomena of structural behaviour are universal. The structural vibration was increased with the increase of external loads, and the vibration amplitude increased significantly when the roof was starting and braking. With the closing of the movable roof, the deflection of the fixed roof increased significantly. In the motion process, the bending moment of the fixed roof gradually increases, while that of the moving roof varies little. Vertical vibration is significant in the motion process by reason of the complex wheel-rail contact.

Analytical Behavior of Eccentrically Loaded Concrete Encased Steel Columns Subjected to Standard Fire including Cooling Phase

Er-Feng Du,Gan-Ping Shu,Xiao-Yong Mao 한국강구조학회 2013 International Journal of Steel Structures Vol.13 No.1

A nonlinear 3-D finite element analysis (FEA) model was developed to predict the behavior of eccentrically loaded concrete encased steel (CES) columns subjected to ISO-834 standard fire including heating and cooling phases. The finite element model has been validated against published tests conducted at elevated temperatures. Comparisons between the predicted results and the test results show that this model can accurately predict the behavior of CES columns under fire. The FEA model was then used to investigate the typical temperature-time curve and mid-height lateral deformation-time curve of eccentric compression CES columns in a complete loading history including initial loading, heating and cooling. It is shown that the temperature delay is obvious at the inner layers of concrete. The fire resistance of a CES column should be checked for the full process of fire exposure until temperatures everywhere in the column start to decrease. The lateral deformation of the column still gradually increases during the cooling phase and the column may fail during that phase. There is a large residual deformation after the fire exposure. Furthermore, the variables that influence the behavior of the CES columns under fire were investigated in parametric studies. It is found that the main parameters which influence the lateral deformation-time curve of the column during the full process of fire exposure are load ratio, slenderness ratio, duration time, depth to width ratio and steel ratio, and the main parameters which influence the residual deformation ratio of the column after fire are load ratio, duration time, cross-sectional depth and steel ratio.

Post-fire Study on Mechanical Properties of Damaged Ultra-high Strength Concrete

Xiao Lyu,Guang-Hao Jia,Gan-Ping Shu,Xin Zhang,Er-Feng Du,Wen-Ming Wang 한국강구조학회 2022 International Journal of Steel Structures Vol.22 No.6

In order to study the eff ect of steel tube, pre-load and temperature on residual performance of heated ultra-high strength concrete (UHSC), an experimental program was carried out to investigate the physical and mechanical properties of UHSC post-fi re in room temperature. With total of 54 standard cylindrical concrete specimens subjected to various temperatures ranging from 62 °C to 496 °C, their residual compressive strength, elastic modulus, peak strain was measured after natural cooling down. By comparing the test results of standard cylindrical concrete specimens with the results of the bare specimens in and after fi re, it is known that the residual compressive strength of standard cylindrical concrete specimens decayed more serious after exposing to same temperature. Seen from the results, the temperature which the specimens suff ered was found to be responsibility to the reduction of the compressive strength, elastic modulus, peak strain. As the temperature up to 300 °C, the strength reduction coeffi cient of UHSC was 0.67 ~ 0.68 and the elastic modulus reduction coeffi cient of UHSC was 0.41 ~ 0.51 with peak strain coeffi cient ε cr ( T ) /ε 0 1.57 ~ 1.67. Finally, based on the analysis of test results, simple formulae were proposed to describe the eff ect of temperature on residual performance of heated UHSC which infi lled the steel tube.