INTERVENTION OF RESTORATION OF THE DAMAGE CAUSED TO STRUCTURAL STEEL COLUMN INSIDE THE EXHIBITION HALL N.29 OF BOLOGNA FAIRGROUNDS

CLIENT: 4 Elle Service S.r.l.
SERVICES RENDERED: feasibility, preliminary, definitive, executive, structural design, DL.
BEGINNING/END OF WORKS: 2015

PROJECT DESCRIPTION

The intervention concerned the accident caused by the violent impact of a mechanical operator against a tubular steel column with circular section, about 8.0 m high, supporting the roof of the pavilion.
The column was out of place by about 60 cm, at the base and in the major component, with the 4 anchor bolts of the base plate sheared off.
anchorage of the base plate sheared off. At the top the column is bolted to a continuous steel beam with double T section, which connects the central pillar supporting the roof.
The column element did not show any direct damage to the section (dents or injuries) and thanks to the low stiffness of the head constraint that allowed it to rotate, as the impact occurred with a greater component in the direction perpendicular to the beam supporting the roof, it was positioned in the current configuration with an axis substantially straight, not vertical, with out of plumb at the base of about 60 cm in the direction perpendicular to the roof beam and about 20 cm in the other direction.
The top of the column, the roof support beam, and the bolted beam-to-column connection were undamaged. The roofing beam was straight, but with a double T section with a not perfectly vertical axis around the column due to the torsion induced by the rotation of the column.

Temporary safety intervention
Before the installation of the temporary structure, the company 4 Elle Service S.r.l. blocked the base plate of the column through the installation of two threaded bars diam. 20 mm using chemical resin, after making holes in the reinforced concrete.

Final restoration intervention
The final restoration intervention has foreseen the positioning of the column and the creation of the new fixing through the laying of new anchor bolts, after checking the geometry of the foundation. This operation was carried out by lifting, as much as necessary, the roof beam in order to be able to reposition the column vertically. It was necessary to replace the bolts both of fixing the column with the
beam and the bolts of the beam joint had to be replaced. Careful preventive inspections were carried out on the column and the beam in order to verify their actual suitability.
The lifting phases of the cover and the repositioning of the column included:

• positioning of the jacks with load cells capable of measuring the force applied, with appropriate extension rods to reach the intrados of the IPE 400;
• slinging of the column to be repositioned with bands and chain connected to existing pillars to operate the horizontal pulls necessary for repositioning;
• cutting of the temporary anchor bolts;
• activation of the jacks for lifting;
• putting the column in vertical position with control of the beam return.