Accepted Manuscript
Comparison of steel-concrete composite column and steel column
Piotr Lacki, Anna Derlatka, Przemysław Kasza
PII: S0263-8223(17)33195-1
DOI: https://doi.org/10.1016/j.compstruct.2017.11.055
Reference: COST 9121
To appear in: Composite Structures
Received Date: 27 September 2017
Revised Date: 13 November 2017
Accepted Date: 20 November 2017
Please cite this article as: Lacki, P., Derlatka, A., Kasza, P., Comparison of steel-concrete composite column and
steel column, Composite Structures (2017), doi: https://doi.org/10.1016/j.compstruct.2017.11.055
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Prof. Piotr Lacki, Ph.D. Anna Derlatka*, Ph.D. Przemysław Kasza
Czestochowa University of Technology
Dąbrowskiego 69, 42-201 Częstochowa
*aderlatka@bud.pcz.czest.pl
Comparison of steel-concrete composite column and steel column
Keywords: steel-concrete composite column; steel reinforced concrete column; steel; FEM
Abstract
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.
1. Introduction
Steel-concrete composite columns are new composite members. They are widely used due to
their high load-bearing capacity, full usage of materials, high stiffness and ductility and large
energy absorption capacity as pointed out by the authors of [1,2]. The steel reinforced
concrete (SRC) member (Fig. 1a), also known as the concrete encased composite member, is
the result of filling the empty space in a steel H-profile with concrete [3].
Combining reinforced concrete (RC) and structural steel sections provides several advantages
over traditional reinforced concrete and steel members. The concrete provides fire resistance
to the steel section and restrains the steel member from buckling [4,5]. Applying steel-
concrete composite columns has a beneficial impact on the course and values of concrete
strains in relation to reinforced concrete columns. However, SRC columns require
longitudinal and transverse reinforcement to prevent the concrete from spalling while being
subjected to axial load, fire, or an earthquake [6]. A well-confined concrete core is vital for
the column to develop a satisfactory plastic hinge rotation capacity. On the other hand,
the reinforcement cage in SRC columns creates difficulty in concrete casting of the beam-
column connections [7,8].
As presented in pracach [9–15], concrete-filled steel tube (CFST) columns (Fig. 1b) are also a
primary type of composite columns. They can reduce the time of construction by eliminating
formwork and reinforcement. CFST column-walls can be quite flexible in shapes, so that they
can be easily fit into all kinds of designs [16,17]. However, the local buckling is always a
major concern in the design of concrete-filled thin-walled steel tube columns.
As presented in papers [18,19], in order to increase the confinement of concrete and make
concrete casting easy in SRC columns, replacing the longitudinal and transverse
reinforcement by a thin-walled steel tube (tubed SRC) is proposed. The tube is placed at the
perimeter of the cross section and it terminate near the beam-column joint. In paper [20], two
types of tubed SRC column (c,d) are distinguished: circular tubed SRC (CTSRC) and square
tubed SRC (STSRC).
Fig. 1. Examples of composite columns sections: a) steel reinforced concrete (SRC), b)
Concrete Filled Steel Tube (CFST), c) square tubed SRC (STSRC), d) circular tubed SRC
(CTSRC)
To date only a few 3-D finite element models have been found in the literature highlighting
the behaviour of concrete encased steel composite columns. The authors of [21] investigated
the behaviour of pin-ended axially loaded concrete encased steel composite columns. A
nonlinear 3-D finite element model was developed to analyse the inelastic behaviour of steel,
concrete, longitudinal and transverse reinforcement bars as well as the effect of concrete
confinement. The main objective of study [22] was to present an efficient nonlinear 3-D finite
element model to analyse concrete encased steel composite columns at elevated temperatures.
Paper [23] presents the carrying capacity of the column in the form of a steel round tube filled
with concrete depending on the ways of loading. A small number of publications of composite
columns FEM models provide the basis for an analysing of such columns. In [24] a three
dimensional elasto-plastic finite element formulation was employed to investigate the strength
degradation of reinforced concrete piers wrapped with steel plates which corrode at the pier
base.
A challenge in the numerical calculations is to take into account material cracking. In this
paper, the fracture model described in [25] was applied. Literature gives different ways to
take into account the material's fracture. One of the noteworthy comments of crack analysis is
presented in [26], in which a homogeneous elastic, orthotropic solid containing three equal
collinear cracks, loaded in tension by symmetrically distributed normal stresses were
considered. Authors of [27] determined the fundamental solutions for an unbounded,
homogeneous, orthotropic elastic body containing an elliptical hole subjected to uniform
remote loads. The aim of the study [28] is elaboration of a new testing method and estimation
of the fracture toughness in Mode III of concretes with F fly-ash (FA) additive.
2. Goal and scope of work
The aim of the work was to perform numerical analysis of a steel column and a steel
reinforced concrete column. The 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
forces distributions in the reinforcement bars and displacements of the whole column were
evaluated.
In the first stage of the work, the composite column was designed as an alternative to the
existing steel column using an analytical method. The existing steel column in the building
was made from a welded, steel S235 H-profile (Fig. 3a).
The internal column of the length 3.60 m was considered. The column was on the second
storey of a six-storey building designed for retail and services (Fig. 2). The column was
subjected to compression and uniaxial bending. Based on the load combination, the axial
force was NEd = 2045.1 kN, while the bending moment was MEd = 180.27 kNm.
Fig. 2. Internal forces in analysed column
The choice of composite column construction was contributed to the fact that several years
ago a tram line was built near the renovated building. Tramway traffic causes additional
vibration in the construction of buildings. Composite columns have a higher energy
absorption capacity than steel columns.
Based on the analytical calculations according to [29], a steel reinforced concrete column with
the following cross-section was obtained (Fig. 3):
− HEB 260 steel profile made from steel S235
− 4 reinforcement bars 12 mm in diameter made from A-IIIN RB500W steel
− C30/37 concrete material
Fig. 3. Cross-section of: a) steel column, b) steel reinforced concrete column
The resistance in compression calculated analytically amounted 90%, whereas the resistance
in combined compression and uniaxial bending was 50%.
The analytical calculations according to standard PN-EN 1994-1-1 [29] do not take into
account stretching of the concrete or stress distribution in the reinforcement. Additionally,
standard [29] does not explicitly define any method of calculating the displacement of the
composite column. Column displacement can only be determined by the numerical model
using the finite element method.
3. Numerical model
The second part of the work consists in modelling the steel and composite columns. The
geometries, loads and boundary conditions of the columns were used as in the analytical
calculations.
3D-solid, 27-node finite elements were used for the steel profiles in both columns and
concrete. Truss, 3-node finite elements were used for the reinforcement bars. The model was
loaded with axial force NEd = 2045.1 kN and a pressure of 0.464 MPa (Fig. 4) acting on the
lateral surface of the column. The pressure was intended to reflect bending moment MEd =
180.27 kNm acting on the supports.
The steel column model has 4104 3-D solid elements. The composite column model has
23292 3-D solid elements and 2112 truss elements. The calculations are performed in 10 time
steps.
Fig. 4. Column models with load and boundary conditions: a) steel column, b) steel reinforced
concrete column
A plastic isotropic material model with the following parameters:
– Density ρ = 7850 kg/m3
– Poisson’s ratio ν = 0,3
– Modulus of elasticity Ea = 210 GPa
– Yield strength fy = 235 MPa
– Ultimate tensile strength fu = 360 MPa
– Elongation A5 = 25%
was used for the steel profiles made from S235 structural steel.
A plastic isotropic material model with the following parameters:
– Density ρ = 7850 kg/m3
– Poisson’s ratio ν =0.3
– Modulus of elasticity Es = 205 GPa
– Yield strength fsk = 500 MPa
– Ultimate tensile strength fu = 550 MPa
– Elongation A5 = 10%
was used for the reinforcement bars made from A-IIIN RB500W steel.
A model with the following parameters:
– Density ρ = 2500 kg/m3
– Tangent modulus at zero strain Ecm = 32 GPa
– Uniaxial cut-off tensile stress fctm = 2.9 MPa
– Uniaxial maximum compressive stress (SIGMAC) fcm = 38 MPa
– Uniaxial compressive strain at SIGMAC εc1 = 2.2‰
– Uniaxial ulitimate compressive stress fck = 30 MPa
– Uniaxial ulitimate compressive strain εcu2 = 3.5‰
was used for the C30/37 concrete material.
The basic concrete material model characteristics are [25]:
− Tensile cracking failure at a maximum, relatively small principal tensile stress
− Compression crushing failure at high compression
− Strain softening from compression crushing failure to an ultimate strain, at which the
material totally fails
4. Results
Results for the steel and composite columns are presented in
Table 1.
Table 1. Results for steel and composite columns
Principal stress,
X-displacement,
Y-displacement,
Z-displacement,
Stress XX, MPa
Stress YY, MPa
Stress ZZ, MPa
Time step
Column
MPa
mm
mm
mm
1 Steel -0.3 -0.00 -0.2 -33.9 -11.1; -10.2; -37.4;
8.8 2.4 10.5
Composite, steel part -0.1 -0.00 -0.1 -179.1; -7.6; -23.2; -33.4;
54.7 5.2 11.2 24.0
Composite, concrete part -15.34; -5.0; -3.6; -5.2;
0.7 0.7 2.4 3.0
2 Steel -0.6 -0.01 -0.4 -67.0 -21.9; -20.1; -68.9;
17.4 4;8 18.0
Composite, steel part -0.2 -0.00 -0.2 -34.9; -16.7; -52.3; -72.1;
8.4 12.2 27.8 54.0
Composite, concrete part -31.6; -10.3; -7.4; -10.1;
1.6 1.4 2.6 2.7
3 Steel -0.8 -0.02 -0.6 -100.1 -32.7; -30.0; -102.9;
26.1 7.1 27.0
Composite, steel part -0.4 -0.01 -0.3 -53.9; -26.4; -82.3; -111.8;
12.9 19.3 44.2 75.0
Composite, concrete part -48.1; -15.7; -11.1; -14.74;
2.4 2.2 2.6 2.5
4 Steel -1.1 -0.03 -0.8 -133.3 -43.5; -39.9; -137.0;
34.7 9.5 37.5
Composite, steel part -0.5 -0.01 -0.5 -72.6; -36.2; -111.6; -151.2;
17.4 25.8 59.5 105.0
Composite, concrete part -64.1; -21.3; -14.4; -18.63;
3.0 2.9 2.6 3.0
5 Steel -1.4 -0.03 -1.0 -166.4 -54.4; -49.8; -171.1;
43.4 11.8 45.0
Composite, steel part -0.6 -0.01 -0.6 -91.3; -46.1; -140.0; -190.2;
21.7 32.1 74.4 150.0
Composite, concrete part -82.5; -26.9; -17.4; -22.4;
3.7 2.8 2.5 3.5
6 Steel -1.7 -0.04 -1.2 -199.6 -65.2; -59.7; -205.1;
52.1 14.2 52.5
Composite, steel part -0.7 -0.02 -0.7 -109.5; -55.6; -166.8; -228.2;
26.0 38.3 89.4 180.0
Composite, concrete part -100.4; -32.7; -19.8; -25.7;
4.3 2.8 2.3 4.0
7 Steel -1.9 -0.05 -1.4 -232.8 -76.0; -69.7; -239.2;
60.8 16.5 60.0
Composite, steel part -0.9 -0.02 -0.8 -127.0; -64.3; -190.3; -263.9;
30.0 44.4 104.4 180.0
Composite, concrete part -118.6; -38.6; -21.8; -28.5;
5.3 2.7 3.6 5.0
8 Steel -2.2 -0.06 -1.6 -266.0 -86.9; -79.6; -273.3;
69.5 18.9 75.0
Composite, steel part -1.0 -0.02 -1.0 -144.9; -74.7; -216.9; -297.2;
34.1 50.7 120.0 210.0
Composite, concrete part -137.3; -44.7; -23.8; -32.1;
6.3 3.2 2.9 5.0
9 Steel -2.5 -0.06 -1.8 -299.4 -97.6; -89.6; -307.7;
78.2 21.3 90.0
Composite, steel part -1.1 -0.02 -1.1 -161.7; -90.4; -233.0; -313.8;
43.3 58.0 136.9 280.0
Composite, concrete part -156.4; -50.9; -26.3; -35.0;
7.4 3.6 3.8 6.0
10 Steel -2.8 -0.07 -2.0 -325.0 -106.0; -103.4; -367.5;
86.9 24.6 105.0
Composite, steel part -1.2 -0.03 -1.2 -179.1; -107.3; -248.1; -331.4;
54.7 65.0 152.0 240.0
Composite, concrete part -175.9; -57.2; -28.3; -37.0;
8.6 4.5 3.3 6.0
The principal stresses distribution (Fig. 5) shows that compression stresses prevail in the steel
column. The maximum compression stress is 321 MPa. It is located at the head of the column,
on the outer surface of the flange, which is not loaded by pressure. The tensile stresses are on
the outer surface of the flange on which the transverse load of the column is acting. The
maximum tensile stress of 90 MPa is on this flange.
Fig. 5. Distribution of principal stresses in steel column, MPa
As shown in Fig. 6, the largest displacements with respect the X and Z axes of the steel
column are ∆lx = 2.1 mm and ∆lz = 2.8 mm. The locations of the largest displacements are
presented in Fig. 6.
Fig. 6. Steel column displacements with respect X and Z axes, mm
The principal stresses distribution in the concrete material (Fig. 7) shows that the principal
compressive stresses are on most of the column surface. The maximum compression stress is
24 MPa. The maximum value is located at the base of the column, on the opposite side of the
applied pressure. The tensile stresses in the concrete element are at the ends of the columns,
on the applied pressure side. The maximum tensile stress is 4 MPa.
Fig. 7. Distribution of principal stresses in concrete of composite column, MPa
Compressive stresses prevail in the HEB profile (Fig. 8). The maximum compressive stress
(201 MPa) is at the column head, on the outer surface of the flange, which is not loaded by
pressure. The maximum tensile stress (201 MPa) is in the corner between the flange and the
web.
Fig. 8. Distribution of principal stresses in HEB profile of composite column, MPa
The distribution of axial stresses in the reinforcement (Fig. 9) shows that the reinforcement
bars are compressed, which is due to the nature of the work of the column. In contrast, the
binders are stretched because during compression of the column, the column strives to
increase the cross-section, which in consequence leads to stretching of the extreme fibres.
Fig. 9. Distribution of axial stresses in reinforcement of composite column, MPa
The displacement of the composite column can only be determined by the numerical model,
since the PN 1994-1-1 standard [29] does not define the method of calculation. The maximum
displacements with respect to the X and Z axes of the analysed column are ∆lx = 1.2 mm i ∆lz
= 1.3 mm.
Fig. 10. Composite column displacements with respect X and Z axes, mm
5. Discussion
After loading the existing steel column, the compressive stress of 321 MPa exceeds the steel
yield strength of 235 MPa. Therefore, changing the structure of the column is suggested.
In the designed composite column, the maximum compressive stress of 25 MPa in the
concrete material is less than the compressive strength of the concrete. In analytical
calculations, the stretching of concrete is omitted. By contrast, the numerical model provides
real stress. The maximum stretching value of 4 MPa exceeds the tensile strength of 2.9 MPa.
Exceeding the tensile strength will result in scratches when the maximum load is reached.
The maximum compressive and tensile stresses in the steel section of the composite column
are 201 MPa, which is 86% of the yield strength. This proves compatibility with the analytical
calculations of the load carrying capacity.
One of the advantages of steel-concrete composite columns is the small displacement
compared to a steel column. The displacement of the steel column relative to the Z axis was
2.1 mm, while the displacement of the column to the Z axis was 1.3 mm. The difference is
due to the fact that in the composite column the displacement of the buckling steel is limited
by the steel profile.
6. Conclusions
− Due to the boundary conditions and way of loading, the concentration of stresses in
the steel and composite columns is at the base and the head of the column.
− Changing the structure of the steel column is suggested because after loading this
column, the stresses of 321 MPa will exceed the yield strength of 235 MPa.
− The load carrying capacity analytically calculated for the steel reinforced concrete
column amounted 90%.
− Based on numerical analysis, the stresses in the steel section of the composite column
were 201 MPa, which corresponded to 86% of the yield strength.
− The numerical model takes into account stretching of the concrete. The tensile stresses
in the concrete in the base and the head of the column exceed the tensile strength
resulting in the appearance of scratches.
− The steel reinforced concrete column is stiffer than the steel one and undergoes less
displacement (∆lx = 1.2 mm, ∆lz = 1.3 mm).
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