Compliant antivibration bar for a steam generator

A steam generator for a nuclear power plant is described comprising a shell, flow tubes having an approximate U-shaped configuration within the shell and arranged in successive columns and rows so as to form an array having a square pattern with spaces therebetween, and compliant antivibration bars fitting between each successive column of tubes and comprising a pair of parallel arranged flexible strips having a space therebetween and supported along the length thereof by spaced ribs. The spacing of the ribs is at least as long as the spacing of four tubes in a single column of tubes, with each successive and parallel antivibration bar being positioned such that its ribs are staggered relative to the position of the ribs of the preceding and parallel antivibration bar