PROBLEM TO BE SOLVED: To install a steel structure inexpensively on a sea bottom, whereas, in order to install a steel structure such as a steel fish bank on the sea bottom, a barge with a large-sized crane becomes necessary, to thereby require high expense for installation.SOLUTION: Welded four arms of a structure in which a four-armed crossed steel bars formed by welding two horizontal-direction short steel bars near the center is welded to one steel bar (vertical shaft) in the vertical direction from the cross intersection, are bonded to long steel bars (4) arranged in a checkerboard pattern on the sea bottom with U-shaped bolts (5), and the vertical shaft is utilized as a strut for a three-dimensional structure.SELECTED DRAWING: Figure 5
