A DUPLEX ARCH FOR THE NEW MALIZIA

BRIDGE IN SIENA

(Un arco duplex per il nuovo ponte di Malizia, a

Siena)

The project for the reconstruction of the Malizia bridge

arose both from the need to improve the flow of traffic and

that of inserting an element into the landscape which was

architecturally qualifying for the town of Siena (Fig. 1).

A functional and technologically innovative solution for a

bridge which will cross over the vast railway seat below was

found in the construction of a large arch, positioned between

the two previously built carriageways (Fig. 2).

Uranus 35N duplex stainless steel was chosen for the

construction of the arch, made up of 5 segments of welded

tube, with an external diameter of 820 mm, obtained from

plates with a thickness of 35 mm and width of 2,480 mm,

supplied simply pickled.

The segment tubes of the arch, each 10,700 mm long, were

brake formed and joined longitudinally by submerged arc

welding. A second brake forming process gave the elements

their correct curvature. Lastly, the connections for the

hangers were then inserted and welded (Fig. 3).

The external surface was shot-blasted using grit and

protected by means of adhesive plastic.

The five elements were pre-assembled (with welding) on

site and subsequently hoisted onto a temporary pier (Fig. 4).

After the geometry of the structure had been checked, the

final welds were carried out.

The joints made on site were obtained by means of electrode

welding (Fig. 5).

Once assembly was complete, any damaged or welded parts

were repaired on site, again using shot-blasting.

The arch and the deck were finally connected by means of

hangers.

I Client: Comune di Siena

I Final project and RUP: Ing. Raffaello Fontani, Comune di

Siena

I Architectural project: Arch. Paola D’Orsi, Comune di

Siena

I Executive project and management of works: Ing.

Pierangelo Pistoletti – Seteco Ingegneria Srl - Corso A. Saffi

1/C int. 15 – I-16128 Genova, phone +39 010 585838, fax

+39 010 585904, ufficiotecnico@setecoge.it

I Production and installation: Costruzioni Cimolai Armando

S.p.A. – Via Ungaresca 38 – I-33170 Pordenone, phone +39

0434 5581, fax +39 0434 361401, info@cimolai.com, www.

cimolai.com

I Duplex plates supplied by: Industeel Italia Srl – Gruppo

Arcelor – Piazza Sant’Ambrogio 8/A – I-20123 Milano,

phone +39 02 72000544, fax 02 72022380, industeelitalia@

liber