Civil Engineering Reference
In-Depth Information
(1939)
On August 31, 1939, during the construction of the reinforced concrete arch bridge
over the Angerman River between the villages of Sando and Lunde in Sweden, the
timber centering of the forms collapsed. The failure was a major disaster, costing the
lives of eighteen construction workers.
The bridge with its span of 264 m (866 ft) was to have become the reinforced
concrete arch with the longest span. The arch rib was designed as a three-cell hollow
rectangular section having a width of 9.4 m (31 ft) and a depth of 2.7 m (8.75 ft) at
the crown and 4.5 m (14.75 ft) at the abutment. The external walls of the hollow sec-
tion were 30 cm (11-7/8 in.) thick and the internal walls were 20 cm (7-7/8 in.) thick.
The construction schedule called for casting the bottom slab first, followed by
the walls and the top slab. The bottom slab was cast in sections and each section was
allowed to set before filling the sections in between. At the time of the accident parts
of the bottom slab had been completed and the workmen were cleaning the forms in
preparation of pouring the center section when the timber centering failed.
The report of the investigating committee appointed after the disaster states
that the failure of the timber was caused by the insufficient strength and stiffness of
the transverse bracing between the two flanges of the arch. However, later investi-
gations revealed that lateral instability of the arch was primarily responsible for the
failure. The Sando Arch was rebuilt and opened to traffic August 28, 1943.
Lessons Learned
Concrete structures often require complex formwork that must act as the primary
structure during construction. Proper design, construction, and removal of timber
formwork must be executed with the same care as the design of the permanent
structure and with full consideration of anticipated loads throughout the construction
process.
References
Die Sando-Strassenbrucke in Schweden, Schweizerische Bauzeitung (1943). 119,
July 16, 105.
ENR. (1939). "This Would Have Been World's Longest Concrete Arch,"
Engineering
News Record
, September 28, 34.
Granholm, H. (1961). "Sandobrons Bagstallining,"
Transactions of Chalmers
University of Technology
, Gothenburg, Sweden, No. 239.
Remarques sur la resistance des cintres en bois de grande ouverture, (1940).
L'effondrement du cintre du pont en beton arme sur le fleuve Angerman, en
Suede, le Genie Civil, April 27, 283.
Ros, M. (1940). "Zum Lehrgerust-Einsturz der Sando-Brucke Uber den Angermanalv
in Schweden,” Schweizerische sauzeitung, 115, January 20, 27-32.
