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Cement Hall, site of
Mythnquai, Zurich, Switzerland
Cement Hall, site of
associated engineer
Robert Maillart
Ingenieurbureau Maillart
date  1938 - 1939
era  Modern  |  category  Building  |  reference  Tf951708
photo  copyright ETH-Bibliothek Zürich, Bildarchiv
Swiss engineer Robert Maillart's last project is one of those structures that you wish still existed when you see historic photos of it. Together with architect Hans Leuzinger, he designed an extraordinary thin concrete shell as a demonstration project for the Swiss National Exhibition (Schweizerische Landesausstellung) of 1939, held on the shores of Lake Zürich (Zürichsee).
The idea of the temporary Cement Hall (Zementhalle) was to show how little concrete is required to form a robust structure. After the festival had closed, the shell was deliberately tested to destruction to increase the technical understanding of concrete’s behaviour under stress.
The National Exhibition, or "Landi" as it was called, opened on 6th May 1939 and closed on 29th October the same year. It occupied sites on both sides of the northern part of the lake, in the Enge and Reisbach districts, connected by a téléphérique (cable car). The expo attracted 10.5 million visitors — about 2.5 times the then population of Switzerland — and generated a profit of 6.4 million Swiss Francs.
Robert Maillart (1872-1940), whose engineering work embodied the potential of reinforced concrete as a construction medium, designed the shell for the Construction section of the exhibition on the west bank, in Enge. It was effectively built as a propaganda piece, intended to showcase the properties and versatility of Portland Cement.
The Cement Hall was 21.4m long, 27.1m wide and 15.25m high overall. Its open-ended oval half hoop shell had horizontal cantilevered flanges along each edge. The whole assembly was supported on four slender tapering columns 3.55m high on either side of an elevated central bridge that acted as a tie between the two sides. The columns were each founded on four timber posts capped with concrete pads, and the bridge was 2.98m wide with 2.5m wide arched openings through the shell walls.
Continuing the line of the columns, two ribs, 240mm wide and up to 940mm thick, encircled the shell roof and joined the metre high external parapets to the bridge walkways. The 230mm thick horizontal flanges were a minimum of 4.3m wide, and up to 6.8m wide at the rear. Each side had four circular cut-outs of 2.6m diameter. The outer edges of the flanges rested on vertical walls 200mm thick and the same height as the columns (3.55m), perforated with five large rectangular openings on each side for glazing. The walls were later incorporated into the adjacent constructions in the Landi.
The curved shell was a constant 11.7m high and 16.1m wide at the front (over a length of 12.2m), but tapered at the back to 9.1m high and 11.1m wide. However, the shell itself was an astonishingly slender 60mm thick.
The deceptively simple structure is based on a parabolic catenary cross-section, which mirrors the flow of forces within it. Maillart thought of the shell as two elements. The top part was a thin arch and the lower part (about 4m high) was a slanting L-shaped cantilever, which provided longitudinal rigidity. Most of the transverse roof stiffening came from the two central ribs.
Maillart took his ideas for thin arches to the limits of what was possible. Though the Cement Hall did not have to carry live loads — as his deck-stiffened arch bridges did, where he managed to reduce the arch thickness to 140mm (Töss Fussgängersteg, 1934) — it did have snow loading.
Steel reinforcement for the shell — a grid of 8mm diameter bars — was mounted on curved timber formwork and the concrete was sprayed over it, a technique known as gunite or shotcrete. The ribs were also constructed in gunite, while other concrete members were cast in situ.
In February 1940, Professor Mirko Ros (1879-1962) of the Eidgenössische Technische Hochschule (Federal Institute of Technology) in Zürich, a friend and colleague of Maillart, directed a programme of load tests on the Cement Hall. The tests provided real data, rather than theoretical concepts, about the structural behaviour of slender reinforced concrete structures under loading, especially its tensile strength.
An array of 30 gauges measuring deflection was mounted on the underside of the shell, in six rows (at the ends of the roof, at the ribs and at the quarter-points) of five gauges across the width. Point loads were imposed at various positions, in six rows between the gauges. The deflection measurement results enabled stress calculations to be completed for each loading condition.
The greatest deflection was 5.2mm, below a single 1 tonne load imposed at the apex of the roof’s front edge — the back of the roof lifted 2.3mm. When an array of 12 point loads of 2.3 tonnes (total 27.6 tonnes) was imposed on the left side of the roof, the maximum deflection was 4.06mm — the right side of the roof lifted 5.9mm.
Permanent deformations of the shell only resulted from increasing the point loads on one longitudinal half of the roof to a total of 30.6-41.4 tonnes, equivalent to a uniformly distributed load of 220-240 kg per sq m, or 1.6 times its self weight. Even then, the roof did not fail.
The Cement Hall proved so strong that the central footbridge had to be demolished first. The reinforcing steel in the arch ribs and columns on the left side had to be sawn through, and a tractor winch pulling at bridge level finally started the collapse. The shell dropped away from the buckled ribs, which twisted and fell.
The test results revealed the breaking load capacity to be unexpectedly high, the thin shell providing extremely effective resistance to deformation and torsion. The information was a step forward in the understanding of such structures.
Architect: Hans Leuzinger (Zürich building department)
Contractor: Prader & Cie, Zürich
Research: ECPK
bibliography
"The Introduction of Reinforced Concrete in Switzerland (1890-1914): Social and Cultural Aspects" by Hans-Ulrich Jost, in Proceedings of the second international congress on construction history: Queens' College, Cambridge University, 29th March-2nd April 2006, Vol.2, Construction History Society, 2006
"Robert Maillart: Builder, Designer, and Artist" by David P. Billington, Cambridge University Press, 1997
"Robert Maillart and the art of reinforced concrete" by David P. Billington, Architectural History Foundation, MIT Press, 1990
"Robert Maillart: Bridges and Constructions" by Max Bill, translated by W.P.M.K. Clay, Pall Mall Press, 3rd revised edition, November 1969
"Space, time and architecture: the growth of a new tradition" by Sigfried Giedion, Oxford University Press, London, 1949
"Ergebnisse der Belastungsversuche an der Zementhalle der LA 1939" by Carl Jegher and Mirko Roš, in Schweizerische Bauzeitung, Vol.120, pp.293-295, 12th December 1942 [in German]
www.expo-archive.ch
www.parlament.ch
Location

Cement Hall, site of