505 Precast Concrete Cover Slab to Circular Shaft
The cover slab for a storage shaft was designed as an interlocking arrangement of seven precast concrete slabs with half joints between the individual units. When the slabs arrived on site they were lifted into place but approximately 10 minutes after the last slab had been placed, five of them collapsed into the shaft.
499 Failure of high strength studs
A reporter’s firm specified the use of M12 grade 8.8 threaded studs that were to be located in a tapped web of a parallel flange channel. The installation proceeded normally and the nuts were not over tightened. The firm then received reports that many of the studs were snapping overnight with the outer nuts falling onto the floor.
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