Experimental and numerical studies of external steel plate strengthened reinforced concrete coupling beams

This paper aims to develop a new method for strengthening reinforced concrete (RC) coupling beams. Experiments were conducted to test three full-scale RC coupling beams, of which two were strengthened by bolted external steel plates on the side faces of the beams and the other one acted as a control specimen without strengthening. The improvements to strength, deformation and energy dissipation of the external plate strengthened RC coupling beams were observed from the experimental results. Nonlinear finite element analysis was carried out to model the strengthened and non-strengthened coupling beams. The material properties used for concrete and reinforcement in the numerical analysis were validated by the laboratory tests. As the experimental study showed that there was a small slip between the bolted connection and the concrete wall pier, a bilinear model was used to simulate the load–slip behaviour of the bolt connections. The model was calibrated by the experimental results from the plate strengthened coupling beams. A numerical parametric study found that the small slip (>3 mm) between the bolt connection and the concrete wall could significantly affect the load-carrying capacity of the bolt connections as well as the structural performance of the strengthened coupling beams. The numerical model developed is very useful for investigating strengthened beams with other configurations and other reinforcement details.