Corrugated bar matting interconnector strips for tunneling - with four out of element lengthways ribs replaced by tubes

The connection is for two building elements to be assembled together, each comprising concrete bars lying parallel to each other and interconnected by flat steel bars, which are welded onto them and adjoin each other so as to form a unified surface, while the bars of concrete protrude at each end for junction with similar neighbouring elements. Four out of eight ribs in such elements, in an irregular sequence, are replaced by tubes, which can be round, angled, slotted or perforated. Junction between such elements can be effected by insertion of the protruding bars on one into those on another. The tubular ribs can be up to twice as long at the ends. A statically unexceptionable overlapping joint is produced. The elements can be curved for use in tunnelling and similar work.