Experimental study on RC T-section beams with an FRP-strengthened web opening

The strong column-weak beam hierarchy, which is now widely accepted in the design of reinforced concrete (RC) frames to achieve good seismic performance, is violated in many existing RC frames designed according to inadequate design codes (generally previous codes). Against this background, a novel seismic retrofit method based on the flexural weakening-shear strengthening (FWSS) technique was proposed by the authors' group to achieve the strong column-weak beam hierarchy in such frames. This technique involves the creation of an opening in the web of a T-section beam (or an alternative feature with a similar effect) for a reduction in the flexural capacity of the beam and the use of local FRP strengthening to avoid shear failure of the post-weakening beam to ensure a ductile failure process. To confirm/demonstrate the effectiveness of the FWSS technique, an experimental study consisting of a total of 8 full-scale RC beams was carried out. Test results presented in this paper show that a sizable web opening can effectively reduce the flexural capacity of a T-section beam and the FRP strengthening system is needed to avoid shear failure of the beam and confine the web chord created by the opening to ensure a ductile response.