Method of connecting pipe-in-pipe structures

A method of forming a structural member by connecting end-to-end a plurality of tubular structures, each tubular structure comprising an inner tubular member (1a, 1b, 1c) located within a co-extending outer tubular member (3a, 3b, 3c), the inner tubular member (1a, 1b, 1c) being longer than the outer tubular member (3a, 3b, 3c) so that at least a portion of one end of the inner tubular members (1a, 1b, 1c) projects from the corresponding end of the outer tubular member (3a, 3b, 3c), in which the inner and outer tubular members of the tubular structures are movable relative to each other in an axial direction, the method being characterized by the steps of joining together simultaneously abutting adjacent ends of outer tubular members (3a, 3b,) of one pair of adjacent tubular structures and abutting adjacent ends of the inner tubular members (1b, 1c) of another pair of adjacent tubular structures, displacing the outer tubular member (3c) of a tubular structure adjoining the one pair axially relative to its inner tubular member (1c) until it abuts against and is contiguous with the outer tubular member (3b) of the one pair of tubular structures, and at least partially overlies the inner tubular member (1b) of the one pair of tubular structures.