A regenerator core for use in a gas turbine regenerator has integral manifold openings formed in the tube plates used to make up the core and has special reinforcing elements which provide high pressure containment in critical portions of the plate-and-fin heat exchanger construction. The reinforcing elements include a series of hoops of U-shaped cross section which are used to bridge the juncture lines of the heat exchanger manifolds. An outer channel region of the hoops is provided with a reinforcing strip of gusset material. The hoops with their reinforcing strips provide structural reinforcement in the region between the manifolds and the conventional side bar reinforcing members in the central core section.