Comparison of a structural behaviour between composite single-I encased steel beam and a double-I encased steel composite beam

This paper shows the results of modeling two cases of the steel-concrete composite beam: one with single-I steel and another with double-I steel. Both cases have the same steel area. Abaqus software was used to simulate and compare the results between 2 cases in terms of bearing capacity, displacement, stress/force and failure mode.

COMPARISON OF A STRUCTURAL BEHAVIOUR BETWEEN COMPOSITE SINGLE-I ENCASED STEEL BEAM AND A DOUBLE-I ENCASED STEEL COMPOSITE BEAM

Nghiem Tien Dung1, Vu Thi Thu Thuy2

1

School of International Education, Thuyloi University, email: dungnt5nk1@wru.vn

2

Civil Engineering faculty, Thuyloi University

1 INTRODUCTION

Nowadays, the steel-concrete composite is

an advantageous solution that has been

widely used in many countries in the world

for multi-storied buildings There have been

many studies on this subject throughout the

world Books of Nethercot, 2003; Johnson,

2004; Pham, 2006; or the standards Eurocode

4 and AISC 2010, 2016 had published design

instructions for composite structures with

single encased steel profile However, there

are no design standard guidelines for

steel-concrete composite with multiple encased

steel profiles Meanwhile, several

international and domestic researchers have

published on steel-concrete composite

structures with multiple encased steel profiles

using physical and numerical models Zhou

et al., 2010 presented experimental and

numerical studies of the composite shear wall

with multi-embedded steel sections They

indicated that composite shear walls with

multi-embedded steel sections have better

energy dissipation capacity than that with a

single one The presence of multi embedded

steel sections did not affect the final failure

mode of the composite shear w alls, but they

would restrain the development of cracks and

prevent the concrete from severe spalling

Tran, 2015 performed his experimental

results on the behavior of composite concrete

beams with 3 H-steel profiles He also

provided some suggestions on model design

for this type of beam based on the results

Tran and Vu, 2016 used Abaqus software to model the steel-concrete composite beams with 3 H-encased steel profiles and compare the numerical results with Tran’s experimental results However, until now there has been no study on the comparison of behavior between composite beams with single encased steel versus multiple I-encased steel

This paper shows the results of modeling two cases of the steel-concrete composite beam: one with single-I steel and another with double-I steel Both cases have the same steel area Abaqus software was used to simulate and compare the results between 2 cases in terms of bearing capacity, displacement, stress/force and failure mode

2 ABAQUS AND SET UP MODEL

Abaqus is one of the popular softw are for structural analysis based on the finite element method Abaqus offers a wide range of options for describing element types separately, then assemble them to a 3D completed object Particularly, different material models with many stages can be described in detail using Abaqus Also, the appropriate results between the numerical model and experiments of Tran and Vu, 2016 show that Abaqus is a useful tool to model 2 cases of this research

Simply supported beam under bending is selected for this research as Figure 1

Figure 1 Structural sketch of research

steel-concrete composite beams

The calculated length of the composite

beams is Lo=10m Beam’s true length

L=11m Center of supports is 0.5m away

from the beam’s edges Cross section

dimension is chosen as b=35cm and h=55cm,

with the ratio Lo/h=18 and h/b=1.57

Tw o cases for modeling and comparison

are shown in Figure 2

Figure 2 Cross sections of two cases

Both cases have a similar total area of I

encased steel of 33.3 cm2 The shape and

dimension of the ‘I’ encased steel is applied

according to the European standards Other

reinforced steels that are chosen for both

cases: stirrup 12 (1.13 cm2) and 4

longitudinal steel bars 20 (3.14cm2) at the 4

corners of the stirrup (Figure 2) with a 5cm

protection concrete layer The second c ase

was chosen based on the results of Vu’s

research It shows that with the same area of I

steel, the composite beam with 2 encased I in

horizontal position; the smaller one in

compression zone and the bigger one in

tension zone has the largest bearing capacity

Selected materials are as follows: C30 for

the concrete according to Eurocode 2 with

characteristic compressive cylinder strength

of concrete at 28 days fck=30MPa, mean

value of axial tensile strength of concrete

fctm=2.9MPa, material models used in Abaqus

are nonlinear The parameters of I-encased

steel S355, longitudinal steel bars, and stirrup

are presented in Table 1 In w hich fy is yield strength, fu is ultimate strength, and Es is the modulus of elasticity of reinforcing steel Solid element type (C3D8R) w ith 8 nodes were selected for concrete beam and encased steel sections, the overall size of 50mm T3D2 truss type elements with 2 nodes were used for reinforcement bars 12 and 20 because they only have axial forces, size of 25mm The connection between bars 20,

12 and the surrounding concrete is perfect, hence “embedded” was used Bonding between encased steel surfaces and surrounding concrete is not perfect Thus, the surface-to-surface interaction model was used

Table 1 Steel parameters Steel type fy (MPa) fu (MPa) Es (GPa)

To efficiently control the failure of composite beam, the applied load acting on the beam was replaced with the displacement

of up to 100mm downwards, at point A (see Figure 1) Each case is carried out in 300 steps of displacement increasing

3 RESULTS AND COMPARISON

Figure 3 shows the relationship between applied load F and vertical displacement at point A of both cases It clearly shows 3 stages of the loading process

Figure 3 The relation between applied load

F and displacement at point A (F~U A )

2) 1)

220

120

160

- Stage 1: applied load F 150kN and

displacement at A UA  27mm, both cases

work similarly with 2 lines coincide with

each other

- Stage 2: 150kN  F  215kN and 27mm

 UA  53mm, the double I beam works

better a little bit compared to the single I

beam During these above 2 stages, the

development of Von Mises stress in concrete

compression zone and I steel tension zone of

both cases are the same as shown in Figure 4

and Figure 5

- Stage 3: F> 215kN, the single I beam

performs better bearing capacity

corresponding to above dash line and reaches

the limit stage lately around 235kN with a

displacement of UA beyond 60-70mm (

Figure 3) Whereas, the double I beam

reaches the limit stage earlier at 215kN and

stable at that value during the displacement at

A is rising During this stage, both concrete’s

compression zone and I steel’s tension zone

reach their strength at the same displacement

of 50mm corresponding to compressive

strength of 30MPa (Figure 4) and yield

strength of 355MPa relatively (Figure 5)

Figure 4 The relation between Mises stress

of concrete’s compression zone and U A

Figure 5 The relation between Mises stress

of I steel’s tension zone and U A

Figure 6 shows the images of tensile

failure of half beam for both cases under the

same load F=215kN As can be seen, the

double I beam has a severe failure than the

single I beam in the middle zone and the 2 supported area corresponding more red dots

Figure 6 Images of tensile f ailure of both cases under the same load F=215kN

4 CONCLUSION

Results of modeling by Abaqus and comparison between two composite beams indicate that at the limit stage, the composite beam with single-I performs larger bearing capacity and less failure compared to the beam with double-I In this situation, the longitudinal steel bars 20 reinforced for both cases seem to be large so that they can bear a compressive load together with a compressive zone of concrete Therefore the bearing capability of upper I steel in double-I beam has

not yet completely made use There would be more tests to be done for a general conclusion

5 REFERENCE [1] Eurocode 4, 2005: Design of composite

steel and concrete structures Part 1.1:

General rules and rules for buildings

[2] Pham V Hoi, 2006 Kết cấu liên hợp thép bêtông dùng strong nhà cao tầng NXB Khoa học kỹ thuật, Hà Nội

[3] Tran V Toan, 2015 Experimental and numerical study of composite steel-concrete walls with several fully encas ed steel profiles Ph.D Thesis, France

[4] Tran V Toan and Vu T T Thuy, 2016 Nghiên cứu dự làm việc của dầm bê tông cốt thép cứng khi không có kết nối giữa bề mặt thép hình và bê tông chịu uốn đơn bằng

mô hình số Tạp chí Tài nguyên nước - Hội

Thủy lợi Việt Nam, vol 03

[5] Y Zhou, X Lu, Y Dong, the Seismic behaviour of composite shear walls with multi embedded steel sections Part I: experiment, Struct Design Tall Spec Build 19 (6) (2010) 618–636