Emergency Staircase Palazzo della Ragione, Milan, Italy

Helzel, Martina

Emergency Staircase Palazzo della Ragione, Milan, Italy

EMERGENCY STAIRCASE, PALAZZO DELLA RAGIONE, MILAN, ITALY
It was important that the staircase should be light and transparent in design, and visually distinct from the historic setting.
Following restoration work on the Palazzo dela Ragione on Piazza Mercanti in the 1980s, the former ‘Salon’ which is nowadays used for exhibitions, was extended and the old entrance on the Piazza Duomo side re-opened. In view of the increased number of visitors to the building, fire regulations dictated the construction of an emergency staircase. Work on this fire escape was finished in 2002. The key qualities required of the design for the staircase were maximum visual transparency and an extremely lightweight construction. It should also have a distinct and separate identity within the historic setting.

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EMERGENCY S T AIRCAS E, P ALAZZ O DELLA RAGIONE, MILAN, IT AL Y
The main column in the support structure for the staircase comprises two sections of folded stainless steel plate tapering upwards towards the top, where they join. These supports are further connected to each other through a complex system of ties and bars that take buckling loads. The column axis is tilted at an angle of 12.7% from the apex, and in the vertical, twisted at
All the components in the support structure were prefabricated and then welded or bolted together on site.

an angle of 25° to the building façade. It thus follows the raking line of the steps in relation to the street. The base point of the column is anchored to the foundations via a floor slab; at the top, to prevent tipping, the stair structure is tied into the wall of the building. At the junction of the main column, 11.50 metres above the ground, the structure divides into three ‘fingers’. Stainless steel rods, 24 mm in diameter, span from the tips of these fingers down to the floor slab, thus giving stability to the whole structure. The support frame for the steps is also sus¬pended from these rods.
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EMERGENCY STAIRCASE, PALAZZO DELLA RAGIONE, MILAN, ITALY

The column divides at the junction into three
Column details,
‘fingers’ from which the
Plans • Elevations
support frame for the
scale 1:20
stepsissuspended.
Section of 8 mm folded stainless steel
6 mm stainless steel connection plates
40 mm stainless steel crosspiece 4 Diagonals 16 mm dia., 20 mm dia. 5 Floor slab 16 mm stainless steel

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EMERGENCY STAIRCASE, PALAZZO DELLA RAGIONE, MILAN, ITALY
At the bottom the stairs end at the level of the arcades at a height of +1.06 m above the street. From here the staircase bridges a height difference of 8.22 metres, with an axial length of 26.50 m and a total of 49 steps. All the steps cantilever out from a single, continuous, welded stainless steel section. In order to take the torsional loads, this sup¬port was designed as a box girder with walls 15 mm thick in the curved parts, and 20 mm thick on the flanges.
Each step is made up of 116 glass panels, tied together by three pretensioned stainless steel rods. On site, the prefabrica¬ted steps are mounted onto the support frame.

Plan • Section scale 1:20
Box girder 240 x 250 mm 15 mm bent stainless steel 20 mm flange plate
10 mm profiled glass panel with three drilled holes, 21 mm dia.
End/tensioning plate 8 mm stainless steel 4Tensioning rods 19 mm dia. stainless steel
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EMERGENCY STAIRCASE, PALAZZO DELLA RAGIONE, MILAN, ITALY
The dead weight of around 430 kg/m and live loads are transmitted into the column via the landings and the suspension rods. The fixed bearing points at the start and end of the staircase also play a role in load transmission. Each step is made up of 116 shaped panels of 10 mm thick glass, threaded onto three pretensioned stainless steel rods to create a monolithic structure.
The 26.5 m long flight of steps is connected to the support frame at just three suspension points – one at each of the three landings.


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Client: City of Milan/City Administration Architect: Marco Dezzi Bardeschi, Milan, Italy Assistant architect: Laura Gioeni Structural engineer: Alessandro Melani, Agliana, Italy Layout and text: Martina Helzel, circa drei, Munich, Germany Translation: Ingrid Taylor, Munich, Germany Photos: Laura Gioeni, Milan, Italy (Title, pp. 2, 4), Andrea Többen, Munich, Germany (pp. 1, 3, 5)
By supporting the staircase on just a single forked column, the street below was kept largelyfree of fixed obstacles.
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