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Sihlholzli Sports Centre and bandstand
Manessestrasse 1, Wiedikon, Zurich, Switzerland
Sihlholzli Sports Centre and bandstand
associated engineer
Robert Maillart
Ingenieurbureau Maillart
date  1929 - 1932
era  Modern  |  category  Building  |  reference  Tf942726
photo  copyright Heimat und Ortmuseum
The Sihlhölzli sports complex is located in central Zürich. Inside its gymnasium, the Turnhalle, is a roof structure that caused bitter controversy between designer and client, as a result of a draughting error. It is now a listed building, and remains in continual use, accommodating facilities for sports such as boxing and martial arts.
The Sihlhölzli area has been used for recreation and sports since at least 1820, when the Zürich Gymnastics Club met here. By 1874, it was a venue for the Swiss Wrestling and Alpine Festival.
In 1918-20, the River Sihl was re-aligned with a shallower channel over a distance of 900m just south of Sihlhölzli, to accommodate the construction of a deep tunnel carrying the mainline railway from the Zürich terminus south to Wollishofen Station. Further tunnelling, completed in 1927, used cut and cover techniques to build a rail tunnel north-west to south-east through Sihlhölzli, from Wiedikon to Enge. Material excavated from the tunnel was deposited in the original river bed of the Sihl.
The modern-day complex, the Sportanlage Sihlhölzli, occupies a plot of about 54,000 sq m on the western river bank. Its other border is a loop of road. A public park lies at the south-west end. The Wiedikon-Enge underground rail tunnel crosses the site some 7m north of the Turnhalle.
The project was planned by Zürich’s city architect Hermann Herter (1877-1945) and design work begun by engineer Dr Ernst Suter (c.1884-1929). In 1929, after Suter’s death, reinforced concrete pioneer Robert Maillart (1872-1940) was appointed design engineer — apparently Maillart’s scheme saved the city 40,000-50,000 Swiss Francs over the original structural design.
The Turnhalle is 96.5m long and 20.5m wide, and positioned perpendicularly to the river. The outdoor area of the complex has a 400m running track, a paved forecourt for ball games and group exercises, a children’s playground and a Musikpavillon (bandstand).
As part of the building is constructed on reclaimed ground, where the river had been backfilled, Maillart had to allow for differential settlement. He chose to compact the soil with rollers, and opted for lightweight construction.
A further complication is the sewer culvert that passes beneath the central portion of the building. Maillart designed bridging foundations here, so that the loads could be transferred to the ground on either side of the sewer.
The interior of the building is divided into 25 bays by its concrete frame, with a central section of seven bays flanked by wings of nine bays each. The principle elements that make up the building’s skeleton are its series of cranked 'A' frames, the their triangular tops forming the roof framing, sloping at 1 in 2. The vertical legs of the frames form perimeter columns, infilled with a lightweight combination of brick, rubble and reinforced concrete, with extensive areas of glazing. The frame sections thicken at the junctions with the roof beams, and the frames are connected longitudinally at this point.
In the roof, the sloping beams and horizontal bars of the frame are connected by five vertical hangers (in compression) and two small diagonal struts. The frames are also connected longitudinally by reinforced concrete rafters at the top of the hangers. Timber lining boards overlay the concrete members.
The basement of the building accommodates two sports halls (C and D), a power gym, a massage room and locker rooms. Hall C, 33m long and 18m wide, has one central row of Maillart’s famous ‘mushroom’ headed concrete columns along its length to support the ground floor slab. On the river side of the building, Hall D, 19m square, has two rows of mushroom columns — presumably because it lies within the area of made ground.
The ground floor consists of two equal-size sports halls (A and B), also 33m long and 18m wide, double-height and column-free. The second floor slab is supported on concrete frames at 3.8m centres spanning the full width of the building. Between the halls, are two floors of meeting rooms, offices and spectator galleries. The second floor has dormer rooms and attics in the wing sections.
On 4th March 1933, Schweizerische Bauzeitung published Maillart’s article "Die Zürcher Sport-und Grünanlagen im neuen Sihlhölzli: Konstruktives" (Zürich’s sports and green spaces in the new Sihlhölzli: construction drawings).
Soon afterwards, assistant city engineer Josef (or Joseph) Killer (1900-93) discovered an error in the drawing of the roof truss. The quantities of reinforcing steel in the central hanger (below the ridge) and the adjacent hangers had been reversed, with the unfortunate result that the central hanger had four bars of 16mm diameter — only 38% of what was required by the 1933 Swiss steel code. As Maillart had signed the drawings, he was deemed responsible.
On 26th April 1933, Maillart produced a five page report in which he assessed the roof design: "Turnhallen Sihlhölzli: Statische Untersuchung der Dachbinder" (Sihlhölzli gymnasiums: static analysis of trusses). He concluded that the draughting mistake did not jeopardise the roof’s structural safety, and though the steel stress had increased, it was still below the limits of the steel code.
He proposed a load test to prove his assertions but this was refused, following intervention by Professor Max Ritter (1884-1946) of the Eidgenössischen Technischen Hochschule (Swiss Federal Institute of Technology) in Zürich.
Ritter and Maillart had disagreed previously on the content of a new code for reinforced concrete. However, on 10th June 1933, the Schweizerische Ingenieur- und Architektenverein (Swiss Society of Engineers & Architects) approved the code prepared at Ritter’s direction. It was published in May 1935.
On 25th September 1933, the city authorities decided to engage Ritter to check the roof design and gave Maillart the opportunity to use his own independent expert. But Maillart believed that he was the only person who could understand the way his structure worked. He suggested that Ritter consult for both sides. Maillart also proposed that he too would determine whether the structure was safe, and pay for any repairs that were found to be necessary.
On 12th February 1934, Ritter delivered his nine page report and more than 100 pages of calculations proving that the roof structure did not satisfy the new concrete code. Since Ritter had exerted control over the code, his verdict wasn’t too surprising, if galling for Maillart.
On 2nd March, Maillart agreed to strengthen the roof but refused to accept the blame for a drawing error that had not been identified. In August 1934, after much controversy, with Herter as Maillart’s only supporter, the city authorities accepted Maillart’s scheme, but they expected him to pay Ritter’s consultancy fee as well as the repair bill.
Maillart’s solution was to install 16 horizontal struts, each spanning the tops of the middle vertical hanger to one each side. The struts were cast in situ, and were prestressed by a jig fixed to the three hangers connected by the strut. The jig consisted of two sloping beams, dipping in the centre, and each day the centre was raised incrementally. Each strut was prestressed over the course of about 44 hours. The work was carried out over three weeks in September by three workmen with Maillart supervising. The sports halls remained in use throughout.
On 27th December 1934, the authorities lodged an official claim against Maillart for payment of Ritter’s 2,850 Swiis Francs fee. Eventually, on 15th February 1935, they reached an agreement — each would pay half.
On 6th March 1935, Maillart’s article "Verstärkung einer Eisenbetonkonstruktion" (Strengthening of a reinforced concrete structure) was published in Schweizerische Bauzeitung. In it, he considered the roof truss structure holistically. His analysis showed that, without aid from the hangers, the eave beams would take 45% of the permanent load. To add a new central hanger would have been difficult, adding a horizontal strut to bridge between compression posts was simpler to construct and, in his eyes, more elegant.
In May 1935, Zürich’s building department objected to Maillart’s article in a letter to the editor and publisher, Carl Jegher (1874-1945). Maillart defended himself robustly in a written reply, which Jegher advised the authorities would be published, along with their letter. Eventually the building department withdrew their letter, and neither was published.
Herter and Maillart also designed the reinforced concrete Musikpavillon (bandstand) on the north side of the site, which cost 83,000 Swiss Francs to construct. Its curved shell looks a little like a helmet with a projecting brim at the front. This appearance seems to have met with varying responses, being described in 1939 by the Wiediker Post as a "splendid pageantry shell" and a "sparrows’ aviary".
In 2004, an arson attack on the bandstand prompted the authorities enclose its front entrance with metal fencing, which remains in place. The structure was saved from demolition in 2006, when the proposed line for widening Manessestrasse was altered, and it is now a listed building.
The Turnhalle is still used intensively and can be seen in many kick-boxing videos available online. The original main entrance doors and windows in Halls A an B have been replaced. In 1985, the floors of Halls A, B and C were resurfaced with plastic. Hall D retains its parquet floor.
During 2001-2, the Sihlhölzli facilities were augmented by three new equipment stores and a tower, constructed using rammed earth walls and reinforced concrete floors and roofs.
Architect: Hermann Herter
Architect (2001-2): Roger Boltshauser
Consulting engineer (2001-2): BKM Ingenieurbüro
Contractor: Heinrich Hatt-Haller (Zurich)
Contractor (2001-2): Lehm Ton Erde Baukunst GmbH
Research: ECPK
"StrucTuricum: 51 bemerkenswerte Bauwerke in Zürich" by Thomas Vogel, Patrick Fehlmann, Thomas Wolf and Emil Honegger, vdf Hochschulverlag AG, Zurich, 2012 [in German]
"Stadt lässt Baudenkmal vergammeln" by Martin Huber, in Tages-Anzeiger, Wednesday 3rd November 2010 [in German]
"Robert Maillart: Builder, Designer, and Artist" by David P. Billington, Cambridge University Press, 1997
"Verstärkung einer Eisenbetonkonstruktion" by Robert Maillart, in Schweizerische Bauzeitung, Vol.105, No.11, pp.130-132, March 1935 [in German]

Sihlholzli Sports Centre and bandstand