Formwork for Concrete Structures by R.L.Peurifoy and G.D- By EasyEngineering.net

194 Chapter Seven
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FIGURE 7-3 Steel-pipe scaffolding fell while concrete was being placed at a
span over a canyon.
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steel beams and the falsework bents, which supported the forms, to
be removed. During the removal of one of the steel beams, something
slipped, and the other steel beams moved out of position, causing the
failure. Several persons were injured.
San Bruno Bridge: This failure occurred during the construction of
a concrete bridge over a railroad. The bridge was designed to use
prestressed concrete beams 95 ft long to span the railroad. The ends
of the beams were supported temporarily during erection by two
falsework bents, one on each side of the railroad. The permanent supports
for the beams were to be concrete girders cast later on top of
permanent bents and to enclose the ends of the precast beams in the
concrete for the girders. During the placing of the precast beams, they
rolled over on their sides and, because they were not designed to be
self-supporting in this position, they collapsed and fell onto the railroad
tracks. Because prestressed concrete beams are used extensively
in concrete structures, it is imperative that constructors use effective
procedures to prevent the beams from rolling over during erection.
Arroyo Seco Bridge: During the construction of this bridge, the 230-
ft-long center span was supported on demountable towers made of
steel pipe. Some of the main beams that rested on the towers and supported
the forms for the concrete structure were previously used steel
sections that may have been damaged and weakened prior to use on
this project. This failure resulted in six fatalities and several others
were injured. Figure 7-3 shows the project after the failure.
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