Keywords: reinforced concrete, beam-column joints, fiber reinforced polymer composites, stiffness, load carrying capacity, finite element.

The use of fibre reinforced polymer (FRP) composites in strengthening reinforced concrete structures has been of great interest for civil engineers in recent years. Less attention has been paid to FRP strengthening of reinforced concrete joints. It is a challenging task to investigate complex components such as beam-column joints numerically as well as experimentally. Parvin & Granata [1] and Mostofinejad & Talaeitaba [2] conducted numerical studies on the subject of strengthening reinforced concrete (RC) connections with FRP laminates. The main objective of their studies focoused on the finite element modeling of exterior RC beam-column connections strengthened with FRP laminates.

The major goal of this study has been focused on the finite element modeling of the interior beam-column joints reinforced with CFRP laminates using the available software. Effects of column forces on the behaviour of concrete joints reinforced with CFRP laminates as well as improvement of structural behaviour of joints strengthened with CFRP laminates, are discussed in the current investigation.

Nonlinear finite element analysis is performed using the ANSYS program. SOLID65, LINK8 and SOLID45 elements represent concrete, discrete reinforcing steel bars, and FRP laminates, respectively [3].

As a case study on an RC interior joint strengthened with FRP laminates, a base joint with two strengthening designs was analysed. In this investigation, the columns were subjected to two levels of axial forces, and lateral loads were applied to the FE joint models at top of the columns up to failure of joints model. FRP L-shaped laminates were placed to improve the diffusion of stresses between members. In order to ensure a proper anchorage, FRP laminates were installed on joints on each side of the column and the latter on both sides of the beam. Then, in order to provide the concrete of column with a higher compressive deformation capacity, FRP laminates were wrapped around column in direction parallel to internal hoops. Beam wrapping was done to ensure a good anchorage for the joint laminates.

The following conclusions can be drawn from numerical studies on concrete interior beam column connections with and without FRP reinforcement:

1. An increase in the load carrying capacity, stiffness and ultimate displacement was observed when the joints were reinforced with FRP laminates and were compared to the Base specimen.
2. The amounts of column axial forces affected the structural behaviour of the joints such as load carrying capacity, stiffness and deflection, under lateral loads applied to the models.

1

Parvin, A. and Granata, P., "Investigation on the effects of fiber composites at concrete joints", Composites: Part B, No. 31, 499-509, 2000 doi:10.1016/S1359-8368(99)00046-3

2

D. Mostofinejad and S.B. Talaeitaba, "Finite element modelling of RC connections Strengthene with FRP laminates", Iranian Journal of Science & Technology, Transaction B, Engineering, Vol. 30, No. B1, 2006.

3

ANSYS User's Manual, 9th ed., SAS IP, Inc., 1996.

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