Behaviour of grout-filled double-skin tubular steel stub-columns: Numerical modelling and design considerations (original) (raw)
Related papers
Journal of Constructional Steel Research, 2004
A series of tests on concrete filled double skin steel tubular (CFDST) stub columns and beam-columns (12) were carried out. Both outer and inner tubes were circular hollow sections (CHS). The main experimental parameters for stub columns were the diameter-tothickness ratio and hollow section ratio, while those for beam-columns were slenderness ratio and load eccentricity. A theoretical model is developed in this paper for CFDST stub columns and beam-columns. A unified theory is described where a confinement factor (n) is introduced to describe the composite action between the outer steel tube and the sandwiched concrete. The predicted load versus deformation relationships are in good agreement with stub column and beam-column test results. Simplified models are derived to predict the loadcarrying capacities of the composite members. #
Experimental Investigation and Numerical Modelling on the Axial Loading of Jet Grouting Columns
Architecture Civil Engineering Environment, 2010
Jet grouting columns are frequently adopted in foundation engineering as an alternative to piles with the aim of strengthening weak subsoil and transferring loads to deeper and more competent strata. In some cases treatments are spanned very close to each other, in order to form a unique massive body made of overlapped columns [8], particularly effective where the required performance consists in a strong reduction of settlements and in improving the resistance to horizontal loads. The second most frequently adopted solution consists of regularly spaced arrays of isolated columns, forming a support system similar in principle to a piled foundation. In both cases steel bars, casing or H piles can be inserted in fresh or hardened
Effect of grout properties on shear strength of column base connections: FEA and analytical approach
Engineering Structures
Concrete grout is used in most column base connections to facilitate the construction process and to ensure that full contact is achieved between the steel plate and the concrete pedestal. However, insignificant attention has been given to its use and performance while there is a lack of clear understanding towards its contribution to the shear strength of column base connections. A comprehensive finite element (FE) study is presented herein investigating the shear capacity of the column base connection on the grout thickness and strength. 3D FE models incorporate important behavioural aspects including the surface interaction and multiaxial constitutive models of the assemblages. The results of the investigation indicated that the introduction of grout improves the behaviour and strength of the column base connections significantly by developing a different load path system consisted of the grout strut, the friction between the base plate and grout, and the tension in the anchor rod due to second order effects. It is found that the current design codes of practice do not consider the positive influence of grout and lead to very conservative shear strengths. Furthermore, the paper proposes a mathematical equation to account for the lateral displacement which is overlooked in the current international regulations.
Behavior of octagonal concrete-filled double-skin steel tube stub columns under axial compression
Journal of Constructional Steel Research, 2020
This paper presents an experimental investigation on the behavior of stiffened octagonal concrete-filled doubleskin tube (CFDST) stub columns subjected to axial compression. A total of eight specimens were prepared and tested under axial compression aiming to study the effects of longitudinal stiffeners and hollow ratio on the elastic-plastic local buckling and ultimate load-carrying capacity of the test columns. The specimens consist of two control specimens without stiffeners (unstiffened columns) and two specimens stiffened with outer-inner tubes welded stiffeners (O\ \I stiffeners) in four sides of the octagonal steel section. In addition, four specimens were stiffened with two types of stiffeners: O\ \I stiffeners and outer tube welded stiffeners (O stiffeners) in eight sides of the outer steel tube section. Furthermore, two hollow ratios were employed. Based on the test results, the ultimate load-carrying capacity, load-displacement curves, load-strain response, ductility, and failure modes were discussed and clarified. The test results indicated that the strength and ductility of the specimens were improved greatly by the presence of the stiffeners. The stiffeners significantly enhanced the confinement and prevented the occurrence of elastic-plastic local buckling of the outer tube. Besides, current design equations were used to predict the ultimate load-carrying capacity of octagonal CFDST stub columns. The test results were then compared with the predicted ultimate capacities of existing design equations. These predictions showed good agreement with the test results.
Compressive Behaviour of Circular, Square, and Rectangular Concrete-Filled Steel Tube Stub Columns
Civil Engineering and Architecture, 2020
In this paper, the compressive behaviour of circular, square, and rectangular concrete-filled steel tube stub (CFSTS) columns is assessed. Nonlinear three-dimensional finite element models for simulating the behaviour of the columns are developed with the aid of the finite element analysis package ABAQUS. Modelling result is compared with the experimental test result to validate the modelling. It is found that the obtained load-axial strain curves of the columns from the finite element analysis and experimental test are notably close to each other and the modelling is finally validated. Then, the analyses of the developed models of the columns are done in accordance with the validated method. Various parameters are adopted in the analyses including the load eccentricity, cross-sectional shape, and steel tube thickness. It is concluded that as the load eccentricity of the columns is increased, their ultimate load-carrying capacity, energy absorption capacity, and stiffness are decreased. Also, the circular columns have generally better performance than their rectangular and square counterparts. The hierarchy of the cross-sectional shapes of the columns from the ultimate load-carrying capacity and energy absorption capacity viewpoints is the circular, rectangular, and square shapes. Although the initial stiffness and slope of the stiffness curves of the rectangular and square columns are slightly higher than those of the circular columns, their stiffness distribution is non-uniform. Furthermore, thicker steel tube leads to greater ultimate load-carrying capacity, energy absorption capacity, and stiffness. Failure modes of the columns are achieved and discussed as well.
Experimental investigation on concrete-filled stainless steel stiffened tubular stub columns
Engineering Structures, 2009
This paper presents an experimental investigation on concrete-filled normal-strength stainless steel stiffened tubular stub columns using the austenitic stainless steel grade EN 1.4301 (304). The stiffened stainless steel tubes were fabricated by welding four lipped angles or two lipped channels at the lips. Therefore, the stiffeners were formed at the mid-depth of the sections. In total, five hollow columns and ten concrete-filled columns were tested. The longitudinal stiffener of the column plate was formed to avoid shrinkage of the concrete and to behave as a continuous connector between the concrete core and the stainless steel tube. The behavior of the columns was investigated using two different nominal concrete cubic strengths of 30 and 60 MPa. A series of tests was performed to investigate the effects of cross-section shape and concrete strength on the behavior and strength of concrete-filled stainless steel stiffened tubular stub columns. The measured average overall depth-to-width ratios (aspect ratio) varied from 1.0 to 1.8. The depth-to-plate thickness ratio of the tube sections varied from 60 to 90. Different lengths of columns were selected to fix the length-to-depth ratio to a constant value of 3. The concrete-filled stiffened stainless steel tubular columns were subjected to uniform axial compression over the concrete core and the stainless steel tube to force the entire section to undergo the same deformations by blocking action. The column strengths, load-axial strain relationships and failure modes of the columns are presented. Several comparisons were made to evaluate the test results. The results of the experimental study showed that the design rules, as specified in the European specifications and the ASCE, are highly conservative for square and rectangular cold-formed concrete-filled normal-strength stainless steel stiffened stub columns.
Behaviour of concrete-filled double skin rectangular steel tubular beam–columns
Journal of Constructional Steel Research, 2006
Double skin composite columns are formed from two steel skins filled with concrete in between. This new form of hybrid column has the potential to be used in many domains such as high-rise bridge piers and large diameter columns in high-rise buildings, etc. This paper describes a series of tests carried out on concrete-filled double skin steel tubular (CFDST) stub columns, beams and beam-columns. Both outer and inner tubes are cold-formed rectangular hollow sections (RHS). The failure modes, and load-deformation behaviour of CFDST specimens are compared with those of conventional concrete-filled steel tubular members and empty double skin tubular members. A theoretical model is developed in this paper for the CFDST stub columns, beams and beam-columns. Reasonably good agreement is observed between the predicted and tested curves. Simplified models are derived to predict the load-carrying capacities of the composite members.
J. Struct. Eng, 2021
The existing theoretical models for the analysis of concrete-filled steel tube (CFST) columns are mainly limited to circular specimens. This paper is aimed at developing a unified theoretical model which is applicable to CFST columns with different cross-sectional shapes, including circular, square, rectangular and round-ended specimens. CFST columns with different shapes (original columns) were replaced with equivalent circular columns by assuming that they have the same sectional areas of core concrete and steel tube. The difference in the behavior between the original and equivalent CFST columns is attributed to the shape effect, which is indicated and modelled by a confinement effectiveness factor. Then, a unified theoretical model for axially loaded CFST columns with different cross-sectional shapes was developed based on an equivalent circular column with the shape effect considered. A total of 982 CFST columns, including 550 circular columns, 396 rectangular (and square) columns, and 36 round-ended columns, were collected to assess the proposed model. Results suggest that the proposed model is capable of accurately predicting the load-carrying capacity and load-deflection curves of CFST columns with different cross-sectional shapes. Finally, the proposed theoretical model was adopted to develop a unified design model of axial load-carrying capacity.