Steel-concrete Composite Columns Research Articles

Investigation of Load Capacity of Steel Concrete Composite Columns Src Reinforced by IPE

In this study, a column with section IPE and different lengths, completely embedded in concrete, is modelled by finite element software ABAQUS. Columns under different bi-axial loading were used and graphs of axial force-axial deformation, interaction axial force, and bending moment and column curve were mapped. The results show that the load capacity of the column, with increasing length and also increasing eccentricity of the axial load, will be reduced. With increasing length, the effect of an increased eccentricity of the reduced load capacity was increased. Equations for the design of the column are also presented. The results of the presented equations were compared with the values obtained from finite element and building national institute 10<sup>th</sup> topic.

Numerical investigation of slender reinforced concrete and steel-concrete composite columns at normal and high temperatures using sectional analysis and moment-curvature approach

In the paper, a numerical procedure for investigation of slender reinforced concrete columns and steel-concrete composite columns at normal and high temperatures is presented. The procedure is based on sectional analysis and moment-curvature approach. Its applicability is illustrated on validation examples in which the results obtained by the simulations are compared with the test data given in literature. It is shown that the procedure provides sufficiently accurate results. The procedure was implemented in an in-house MATLAB code. The code is employed for the calculation of the examples presented in the paper. The code was also included in freely available scientific computer programs. The procedure is applicable for normal and high temperature conditions and for columns of symmetrical cross-sections of any type and shape. It is applicable in connection with any type of temperature-time curve, heat transfer model, and material models.

Characterisation of a new flat mechanical shear connection mean for steel-concrete composite columns

For buildings in steel-concrete composite structure, the current practice of the shear connection in fully embedded columns is the implementation of headed shear studs. This type of connector has been mainly developed for composite beams and some disadvantages have been identified for column application. For example, due to the shear stud geometry, the difficulty of the reinforcement application and more complicated handling of the column are recognised. Taking into account the additional high resistance, stiffness, ductility and production efficiency criteria, an innovative type of flat shear connection, with the potential for a fully automatic fabrication process has been developed. The proposed new type of shear connectors is made out of regular reinforcement bars welded to the flanges of steel profiles under a specific arrangement. The conducted investigation consisted of three different variants: transversal, longitudinal and angled (V-shaped) of connectors applied to the HEB120 steel profiles. In addition, tests without any mechanical connectors were conducted as reference tests. The specific load-bearing behaviour in terms of load-slip curves for each connector variant has been obtained and analysed. After the tests, the specimens were opened and the failure patterns were investigated. 3D non-linear numerical simulations in the FE code Abaqus® have supported the performed investigations. In the results, the load flux, the decisive force-transfer mechanisms and resistance limits have been identified.

Behavior of axially loaded circular stainless steel tube confined concrete stub columns

Stainless steel tube confined concrete (SSTCC) stub column is a new form of steel-concrete composite column in which the stainless steel tube is used to confine the core concrete without resistance to the axial load directly. It could take the advantages of both the stainless steel tube and the steel tube confined concrete columns. This paper presents the experimental investigation of circular SSTCC stub columns subjected to axial load. Meanwhile, comparative tests of the circular concrete-filled stainless steel tubes and circular hollow stainless steel tubes were also conducted. The experimental phenomena of specimens are introduced in detail and the experimental results are analyzed. Through the investigation of axial stress and hoop stress on the stainless steel tube, the interaction between stainless steel tube and core concrete is studied. The experimental results showed that the stainless steel tube provides confinement to the core concrete, increasing the compressive capacity of core concrete significantly. In addition, the confinement of stainless steel tube in SSTCC stub columns is larger than that in concrete-filled stainless steel tubes. Therefore, the load-carrying capacity of SSTCC columns is higher than that of concrete-filled stainless steel tubes. Besides, an equation was proposed to calculate the load-carrying capacities of SSTCC columns and concrete-filled stainless steel tube columns. The calculated results agree well with the experimental results.

Local and post-local buckling of normal/high strength steel sections with concrete infill

Steel sections in steel-concrete composite columns have been proofed to be less susceptible to local buckling and have higher capacity than bare steel columns, attributed to the internal restraints provided by the infilled concrete. This article presents a theoretical study concerning the local and post-local buckling of fabricated normal and high strength steel sections filled with concrete, including concrete filled steel tubular (CFST) sections and partially encased composite (PEC) sections. A nonlinear finite element (FE) model was established and validated to simulate the behavior of steel plates in contact with concrete, with both geometric imperfections and residual stresses explicitly incorporated. This model was subsequently applied in a parametric study to investigate the effects of several critical factors on the local buckling behavior of box and I steel sections. Based on the available test and FE results, new design formulas were proposed to predict the local buckling and post-buckling ultimate strengths of concrete-restrained steel box and I sections, taking into consideration high material strengths, residual stresses and geometric imperfections. The enhancement of strength due to the presence of concrete infill was confirmed through a comparison with the post-buckling strength of bare steel sections. Recommendations were also made for design purpose based on the formulas proposed.

Behavior of an Innovative Square Composite Column Made of Four Steel Tubes at the Corners and Corrugated Steel Batten Plates on all Sides

Steel‐concrete composite (SCC) columns have widely been applied in modern construction industry owing to the composite action between the concrete and the steel. The benefits of SCC columns can be further achieved if the confinement effect of concrete is applied. Therefore, this paper presents an innovative square steel‐concrete composite (ISSCC) column made of four steel tubes at the corners and corrugated steel batten plates on all sides. Through the experimental and finite element (FE) numerical simulation calculations, the axial compression performance and seismic performance of the ISSCC column were discussed, and the FE model was verified through experimental results. The seismic performance of the ISSCC column was compared and analyzed with reinforced concrete column under different axial compression ratios. The research showed that FE models can accurately simulate the deformation, stress, and failure states of the ISSCC column under axial pressure and horizontal low cyclic load. Furthermore, the ISSCC column performed good ductility and energy dissipation capacity, and the seismic performance index was better than the reinforced concrete column and had better seismic performance. The results of this study can provide reference for the design and development of the new composite column.

Validation of a general design procedure for the transverse impact capacity of steel columns

There has been considerable interest over the past decade in the transverse impact response of steel columns and composite steel-concrete columns. While several researchers have developed analytical procedures for specific types of steel sections, a unified design approach has yet to be established. The present paper develops a generalised rigid-plastic procedure to calculate the design transverse impact capacity for a wide range of steel and composite column sections. The design procedure is specifically developed to align with current international hot-rolled steel design specifications, including those in Australia, North America, the European Union and China. A database of 320 impact experiments is collated from the literature, and used to validate the general design procedure. It is demonstrated that the procedure provides robust transverse impact capacity predictions for solid rectangular steel sections, steel I-sections, circular and rectangular steel hollow sections, concrete filled circular and rectangular steel hollow sections and concrete filled double skin steel hollow sections. In some cases stainless steel members were additionally included.

Thermo-Mechanical Behavior of Steel-Concrete Composite Columns under Natural Fire Including Heating and Cooling Phases

The fire behavior of concrete filled hollow steel sections has been studied extensively in various countries. Almost all essential parameters influencing their resistance have been identified: section shape and dimensions, concrete filling, reinforcement ratio, steel tube thickness, column slenderness, thermal and mechanical properties of steel and concrete, and even the contact problem at the steel-concrete interface. Most of these works were done under standard fire conditions (ISO), which are represented by a continuously increasing temperature over time. It is thus not really a curve reflecting a natural fire which includes not only a heating phase but also a cooling phase during which the temperature of the fire is decreasing back to ambient temperature.In this paper, the behavior of axially loaded concrete filled square hollow section columns subjected to natural fire conditions has been studied. The main objectives of this study are: first, to demonstrate the phenomenon of delayed collapse of this type of columns during or after the cooling phase of a fire, and then study the influence of certain determinant parameters, such as section size, tube thickness, reinforcement ratio, concrete cover and column length.The results show that delayed failures occur for massive sections, small values of the thickness of the steel tube and for the low-slendernes.

Study on seismic behavior of encased steel jacket-strengthened earthquake-damaged composite steel-concrete columns

In order to study the seismic behavior of earthquake-damaged composite steel-concrete columns strengthened by enveloped steel, based on current design codes, four composite steel-concrete column models were designed and manufactured. Destructive tests on the models under low-cyclic loading were then carried out. The feasibility and effectiveness of earthquake-damaged columns strengthened by enveloped steel and the reinforcement effect on different levels of seismic damage were studied. The results show that enveloped-steel-strengthened earthquake-damaged composite steel-concrete columns meet the strong column-weak beam requirement of seismic design, and the failure mode of all the columns was in bending. The performance of the rehabilitated columns can reach or even exceed the level of their original seismic performance before seismic damage. Composite steel-concrete frame columns strengthened by enveloped steel were also simulated using the finite element (FE) analysis software ABAQUS. The analytical study was conducted and compared with the experimental results, and it was basically consistent with the experimental data.

Elastic flexural rigidity of steel-concrete composite columns

The use of elastic analysis is prevalent in the design of building structures even under loading conditions where inelasticity would be expected. Accordingly, geometric and material properties used in the elastic analyses must be carefully selected to maintain accuracy. Steel-concrete composite columns experience different forms of inelasticity. Concrete cracking is the source of much of the inelasticity and occurs at relatively low levels of load, but partial yielding of the steel, slip between concrete and steel, and concrete crushing also contribute to losses in stiffness. In this paper, the behavior of composite columns is characterized at the cross section and member levels through comparisons between inelastic and elastic analyses. Then, through a broad parametric study, specific practical design recommendations are developed for the elastic flexural rigidity of composite columns for the determination of lateral drifts under service loads. The recommendations in this paper provide simple and robust values for the stiffness of composite columns to be used for drift computations involving lateral loads.

Seismic behavior of tall buildings using steel–concrete composite columns and shear walls

SummaryFor the seismic design of tall building structures, the behavior under severe earthquakes should be carefully considered and the upper limit of inter‐story deformations are often defined by the design codes. To improve the performance of structures under severe earthquakes, composite structural members, including steel reinforced column and steel plate reinforced shear wall, are often adopted. In the present work, the seismic behavior of tall buildings using steel–concrete composite columns and shear walls is investigated numerically. Fiber beam–column element models and multilayer shell models are adopted to establish the finite element model of structure, and the material nonlinearities are described by the plasticity and damage models. The accuracy of the developed models is verified by the experimental results of a single shear wall. Systematic numerical simulations are performed for the tall building structures subjected to different earthquakes. The comparative study indicates that the nonlinear redistribution of internal forces plays a very important role for the performance of tall buildings under severe earthquakes.

Structural behaviour of concrete filled hollow steel sections exposed to parametric fire

This article analyzes steel-concrete composite columns subjected to natural fire scenarios in order to verify that the possibility of structural collapse during or after the cooling phase is real. The main objectives of this study are: first, to highlight the phenomenon of delayed collapse of this type of columns during or after the cooling phase of a fire, and then analyze the influence of some determinant parameters, such as section size, tube thickness, reinforcement (ratio), concrete cover and column length. The results show that critical conditions with respect to delayed failure arise for massive sections, small values of the steel tube thickness and for columns with massive section.

Comparison of steel-concrete composite column and steel column

The aim of the work was numerical analyses of a steel-concrete composite column and a steel column. An internal column 3.60 m in length was considered. The column was on the second storey of a six-storey building designed for retail and services. The column was subjected to compression and uniaxial bending. The existing steel column was made from a welded H-profile. In the first stage of the work, the composite column was designed as an alternative to the existing steel column using the analytical method. A steel reinforced concrete column with a steel H-profile was selected. The second part of the work consisted in modelling the steel and composite columns. The geometries, loads and boundary conditions used in simulations of the columns were the same as in the analytical calculations. Numerical analysis was carried out using the ADINA System based on the finite element method. In the steel column, the stresses and displacements were considered. In the composite column, the stresses in the steel and concrete elements, the stresses distributions in the reinforcement bars and displacements of the whole column were evaluated.

Analysis of Stress in Steel and Concrete in Cfst Push-Out Test Samples

The paper presents the analysis of stress in steel and concrete in CFST composite elements subjected to push-out tests. Two analytical models of stress distribution are presented. The bond at the interface between steel and concrete in the initial phase of the push-out test is provided by the adhesion. Until the force reach a certain value, the slip between both materials does not occur or it is negligibly small, what ensures full composite action of the specimen. In the first analytical model the full bond between both materials was assumed. This model allows to estimate value of the force for which the local loss of adhesion in given cross section begins. In the second model it was assumed that the bond stress distribution is constant along the shear transfer length of the specimen. Based on that the formulas for triangle distribution of stress in steel and concrete for the maximum push-out force were derived and compared with the experimental results. Both models can be used to better understand the mechanisms of interaction between steel and concrete in composite steel-concrete columns.

Flexural stiffness of the composite steel and fibre-reinforced concrete circular hollow section column

The recent development in technology of production and transportation of steel fibre-reinforced concrete enables its utilization in composite steel-concrete structures. This work is a part of a project which focuses on development of mechanical behaviour of circular hollow section (CHS) composite steel and fibre-concrete (SFRC) columns at elevate temperature. Research includes two levels of accuracy/complexity, allowing simplified or advanced approach for design that follows upcoming changes in European standard for composite member design in fire EN1994-1-2 [1].One part is dedicated to determination and description of flexural stiffness of the SFRC CHS columns. To determinate flexural stiffness were prepared series of pure bending tests at elevated and ambient temperature. Presented paper focuses on the results of the tests and determination of flexural stiffness at ambient temperature. Obtained outputs were compared to data of existing studies about concrete-filled tube members with plain concrete and values analytically calculated according to the existing European standard EN1994-1-1 [2].

Reliability of partially encased steel-concrete composite columns under eccentric loading

Abstract The Brazilian design code for composite buildings (NBR8800) has never been subject to a reliability-based calibration of the partial factors used in design. As a consequence, the level of structural safety achieved by using these factors is, in general, unknown. This paper presents a study of the reliability of partially encased steel-concrete composite columns, subject to compression and bending. Literature statistics are used to quantify uncertainty in strength of structural materials and in loads. Reliability indexes are evaluated, via FORM, for two ratios between dead and live loads, and for some values of load eccentricity. It was found that larger load eccentricity leads to a reduction in reliability indexes. These values are larger than minimum values recommended in international design codes; hence one concludes that design of such columns using NBR8800 leads to acceptable safety levels.

Ductility assessment of two-chord composite steel-concrete battened columns

The ductility of a column is one of the most important characteristics of a structure subjected to unexpected overloads, load reversals, blast loads or dynamic impacts. Structural ductile members are capable of dissipating large amounts of energy by undergoing large deformations before failure, hence providing early warning to the occupants of the building. Previous analyses conducted by the authors suggest that, in addition to the type of column (steel, reinforced concrete and composite steel–concrete), the applied measure of ductility as well as other factors (the materials used and the loading and boundary conditions) have a significant influence on a column’s ductility. This paper proposes a new approach to the analysis of the ductility of columns. This approach distinguishes between the column’s pre-peak, post-peak and total ductility, and develops ductility parameters based on the displacement and energy for each of these ductility types. Based on experimental and numerical research on two-chord composite steel–concrete columns subjected to vertical monotonic loads, the influence of concrete strength and batten plate spacing on the columns’ vertical ductility is evaluated. It is concluded that designing two-chord composite steel–concrete columns to have small batten plate spacing and a relatively low concrete strength class can maximise the vertical ductility.

Steel to Concrete Bond Transferring in CFST Columns Connected to Beams through the Concrete

An important innovation in structural design in the last thirty years has been the use of steel-concrete composite columns, with particular diffusion of tubular profiles. These elements are known in the technical Literature as concrete filled steel tube (CFST) and the metal profiles that characterize the external jacket are usually circular, square or rectangular.A relevant issue that must be considered is the transfer of shear stresses by adhesion between steel and concrete in composite columns. The problem of adhesion, and thus its formulation, depends primarily on the type of technology used to connect beams to columns. In particular, two different models can be produced: the first case where the beams are connected only to the metal external jacket of the pillar (i.e. steel beams connected with bolted flanges to the column), and the second where beams and columns are connected also in the concrete matrix (i.e. the case of beams in steel-concrete technology, or traditional reinforced concrete beams).International Standards, regarding the problem of adhesion in jacketed columns, only referee to the first connection type, giving a constant value for adhesion coefficient along the transferring length, with no dependence to the size of the section, and indicate transferring lengths independently from the type of beam-to-column connection and the shape of the section. In the Paper are hence proposed expressions that quantify the fundamental values that govern the action transfer mechanism by adhesion in CFST, such as the transfer length, the perimeter of the active transfer and the shear stress distribution, as a function of the slenderness ratio and of the type of connection adopted. All this has been carried in order to produce a model for the estimation of bond stresses for the second of the two construction system mentioned above.

Protected steel columns vs partially encased columns: Fire resistance and economic considerations

As is commonly known, resistant properties of steel columns decrease quickly with an increase in temperature. Thus, steel columns are usually surrounded with low thermal conductivity materials that protect them at high temperatures. Another interesting alternative is the use of partially encased columns, a sort of steel-concrete composite column. Focused on fire performance and economic cost of a standard column, this paper presents a comparison study between partially encased composite columns and I-shaped steel columns with and without protection. A range of geometric cross-sections and material properties have been tested and the Pareto frontier has been used to show the cheapest columns with the best performance. The study is carried out assuming geometrical and material restrictions accepted by the European codes and imposing a constant axial load. Results show that most of studied protected columns resist around 120min before collapsing in fire conditions. The structural response of partially encased composite (PEC) columns under simulated fire conditions is good and it can be seen from this study that significant savings can be obtained with a good design of PEC column, savings around 50%. The relative costs of the three design options studied are quantified. Considerations about the geometry and materials criteria are provided. All steel sections described in this study are commercial ones, which includes European, British, American, Japanese and Russian standard steel sections.

Composite C-C Columns by Utilizing of UHPFRC

Main advantage of composite concrete columns, in comparison with traditional reinforced concrete columns, is its increased load-bearing capacity by using of solid steel reinforcing core. Ordinary type of such a steel-concrete (S-C) composite column consists of normal concrete and different type of solid steel core. In last decades high quality concrete is more and more used for load-bearing structural members exposed compression like columns. Present knowledge level in the area of ultra-high quality of concrete open a new chance for utilization of this progressive structural material in concrete building industry. This paper presents some new information and laboratory test results of concrete-concrete (C-C) composite columns by utilizing of UHPFRC.