A new type of exterior RCS connection, in which a steel prole totally embedded inside RC column is directly welded to the steel beam, is recently proposed within European RCFS project SMARTCOCO. This kind of joint detail is not covered by the existing design guidelines. Indeed, Eurocodes 2, 3 and 4 give some provisions that can partly be used for the design of such a joint. There remains however a real lack of knowledge relatively to the issue of the force transmission from the embedded steel prole to the surrounding concrete of the column. Questions that can rise when designing such a connection are about the optimal anchorage length to embed the steel prole or about the design of reinforcements in the connection zone of the RC column and in the transition zone at each end of the embedded steel prole. Based on Eurocodes and existing research works in the literature, a design method is proposed within European RCFS project SMARTCOCO. However, experimental tests and numerical simulations need to be conducted to valid this method. This paper deals with nonlinear nite element model for this type of exterior RCS beamcolumn connection. The material nonlinearities of concrete, steel beam, stud and rebar are included in the nite element model. Four RCS joints with dierent anchorage lengths and concrete classes are modeled. The failure modes and loads are analyzed and compared to the predicted ones of the design model.

1. Intro FE model Results Conclusions RCS Joint test
Finite Element analysis of a hybrid RCS
beam-column connection
Quang-Huy Nguyen*; Mohammed Hjiaj*; Xuan Huy
Nguyen**; Huy Cuong Nguyen**
* Structural Engineering Research Group, INSA de Rennes, France
** University of Transport and Communications, Vietnam
12 May 2015
1/24 International Conference CIGOS Paris, 11-12 May 2015

2. Intro FE model Results Conclusions RCS Joint test
Overview
1 Introduction
2 3D Finite Element model
3 Results and Discussions
4 Conclusions
5 RCS Joint tested at UTC of Vietnam
2/24 International Conference CIGOS Paris, 11-12 May 2015

3. Intro FE model Results Conclusions RCS Joint test
Introduction
Smart Composite Components
Concrete Structures Reinforced by Steel Profiles
“SmartCoCo” project
Grant Agreement RFSR-CT-2012-00031
Hervé DEGEE, Teodora BOGDAN, André PLUMIER Université de Liège, Coordinator
Nicoleta POPA, Louis-Guy CAJOT ArcelorMittal
Jean-Marie DE BEL, Pierre MENGEOT BESIX SA
Quang-Huy NGUYEN, Mohammed HJIAJ, Hugues SOMJA INSA Rennes
Ahmed ELGHAZOULI, Dan BOMPA Imperial College London
3/24 International Conference CIGOS Paris, 11-12 May 2015

4. Intro FE model Results Conclusions RCS Joint test
Introduction
Overview of the project
Develop design guidance for “hybrid” structural situations which are:
neither reinforced concrete Eurocode 2, ACI 318
nor composite steel-concrete Eurocode 4, AISC 2010
Practical situations analysed
• Composite column sections with more than one fully encased steel profile
Hong Kong International Finance Center: Hybrid column with 3 steel
section as reinforcement
4/24 International Conference CIGOS Paris, 11-12 May 2015

5. Intro FE model Results Conclusions RCS Joint test
Introduction
Practical situations analysed
• Composite elements used to transfer forces from composite beams to RC
columns or walls, namely “RCS joint ”
• Connections of RC flat slabs or beams to columns or walls
Hybrid joint
5/24 International Conference CIGOS Paris, 11-12 May 2015

6. Intro FE model Results Conclusions RCS Joint test
Introduction
RCS joint overview
• Design model proposed by Kanno and Deierlein (2002) for RCS joints;
• The model is the improvement of ASCE Guidelines RCS joints in buildings
located in low to moderate seismic risk zones.
6/24 International Conference CIGOS Paris, 11-12 May 2015

7. Intro FE model Results Conclusions RCS Joint test
Introduction
RCS overview
• Nishiyama et al. (2004): Guidelines for
Seismic Design of Steel-Concrete
Composite Structures;
• Design based the "strong column-weak
beam" philosophy;
• The joint failure modes are similar to the
design guidelines of the ASCE 1994, for
the shear failure and bearing failure
7/24 International Conference CIGOS Paris, 11-12 May 2015

8. Intro FE model Results Conclusions RCS Joint test
Introduction
Objective:
• Study a new type beam-column joint which is the connection of steel beam to
RC column: A steel profile is totally embedded into a RC column is used to
connect the beam through the steelwork part of composite section
• Particular attention will be paid to
The force transmission problem between the embedded steel profile and the
concrete of the column
The failure mode of this new type of connection
o Different anchorage lengths
o Different concrete classes
Studied hybrid joint
8/24 International Conference CIGOS Paris, 11-12 May 2015

9. Intro FE model Results Conclusions RCS Joint test
Introduction
Test Specimens
The four specimens were pre-designed based on the tentative design method
developed within Smartcoco project.
9/24 International Conference CIGOS Paris, 11-12 May 2015

10. Intro FE model Results Conclusions RCS Joint test
3D Finite Element model
Abaqus 3D model of a half
exterior RSC joint specimen
Interaction and constrain conditions:
• Embedded constraint can be used for the
interaction between rebars and concrete
surrounding;
• Hard contact with frictionless for surface to
surface contact between the profile and the
concrete.
Material models:
• For concrete: Damage Plasticity model (Lee and
Fenves 1998).
• For steel: Von Mises yield criterion with
isotropic hardening rule.
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11. Intro FE model Results Conclusions RCS Joint test
3D Finite Element model
Element type and meshing
C3D8R-element: 8-node linear brick element with reduced integration stiffness;
T3D2-element: 2-node linear 3-D truss element
HJS4 specimen:
• 32618 concrete elements
• 2976 steel elements
• 690 rebar elements
11/24 International Conference CIGOS Paris, 11-12 May 2015

12. Intro FE model Results Conclusions RCS Joint test
3D Finite Element model
Parameter set:
o Anchorage length Le:
o Concrete class
1 m 1,1 m 1,25 m 1,5 m
C30 C40 C50 C60
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13. Intro FE model Results Conclusions RCS Joint test
Results and Discussions
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
Displacement [mm]
Appliedload[kN]
Concrete C30
L
e
= 100 cm
Le
= 110 cm
Le
= 125 cm
L
e
= 150 cm
Comment: The behaviour of the hybrid joints is unchanged when the
anchorage length Le > 1
13/24 International Conference CIGOS Paris, 11-12 May 2015

14. Intro FE model Results Conclusions RCS Joint test
Results and Discussions
Comment: The behaviour of the hybrid joints is unchanged when the
anchorage length Le > 1
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
Displacement [mm]
Appliedload[kN]
Concrete C40
Le
= 100 cm
Le
= 110 cm
Le
= 125 cm
L
e
= 150 cm
14/24 International Conference CIGOS Paris, 11-12 May 2015

15. Intro FE model Results Conclusions RCS Joint test
Results and Discussions
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
Displacement [mm]
Appliedload[kN]
Concrete C50
Le
= 100 cm
Le
= 110 cm
Le
= 125 cm
Le
= 150 cm
Comment: The behaviour of the hybrid joints is unchanged when the
anchorage length Le > 1
15/24 International Conference CIGOS Paris, 11-12 May 2015

16. Intro FE model Results Conclusions RCS Joint test
Results and Discussions
0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150
0
100
200
300
400
500
600
700
800
900
1000
1100
1200
Displacement [mm]
Appliedload[kN]
Concrete C60
L
e
= 100 cm
Le
= 110 cm
Le
= 125 cm
Le
= 150 cm
Comment: The behaviour of the hybrid joints is unchanged when the
anchorage length Le > 1
16/24 International Conference CIGOS Paris, 11-12 May 2015

17. Intro FE model Results Conclusions RCS Joint test
Equivalent plastic strains (Le=1.1m and Concrete C40)
Plasticstrain17/24 International Conference CIGOS Paris, 11-12 May 2015

18. Intro FE model Results Conclusions RCS Joint test
Stresses (Le=1.1m and Concrete C40)
Stress18/24 International Conference CIGOS Paris, 11-12 May 2015

19. Intro FE model Results Conclusions RCS Joint test
Results and Discussions
• The first yielding observed numerically is about the encased steel web panel in
tension
19/24 International Conference CIGOS Paris, 11-12 May 2015

20. Intro FE model Results Conclusions RCS Joint test
Results and Discussions
• Some plasticized zones are observed in concrete before reaching the yielding of
web panel in tension;
• They are identified as "local" plasticization and not avoided in steel-concrete
structures.
20/24 International Conference CIGOS Paris, 11-12 May 2015

21. Intro FE model Results Conclusions RCS Joint test
Results and Discussions
• The second yielding observed numerically is at the stirrups;
• The yielding of the stirrups probably results from the transmission of the
vertical applied force to the concrete column occuring at the interface contact
between steel beam lower flange and the concrete below.
• It forms a "local strut and tie" mechanism in which two concrete struts start
from the lower flange to the longitudinal reinforcement and the stirrups play a
role of tie.
21/24 International Conference CIGOS Paris, 11-12 May 2015

22. Intro FE model Results Conclusions RCS Joint test
Conclusions
• A 3D finite element model has been developed to analyse the behaviour of new
type of exterior RCS joint subjected to static loading;
• Material nonlinearities, interaction and the contact between steel and concrete
are taken into account.
• The numerical results indicated if the encased steel profile is totally anchored
in RC column, the behaviour of the studied RSC joint is the one of steel joint (in
sense of Eurocode 3).
• The failure mode firstly reached is caused by the bending moment transmission
from steel beam to encased steel column. As a result the concrete does not
affect much on the load value corresponding to this "steel joint" yielding.
• The concrete contribution in the joint resistance starts to be activated when
"steel joint" yielding is reached and results in the hardening load-displacement
curves.
• The numerical observation needs to be confirmed by the experimental one.
22/24 International Conference CIGOS Paris, 11-12 May 2015

23. Intro FE model Results Conclusions RCS Joint test
RCS Joint tested at UTC of Vietnam
Cyclic test of RCS joint carried out at University of Transport and
Communications of Vietnam
December 2014
23/24 International Conference CIGOS Paris, 11-12 May 2015

24. Intro FE model Results Conclusions RCS Joint test
Thanks for your attention !
... any questions ?
24/24 International Conference CIGOS Paris, 11-12 May 2015