Expansion Anchor Performance in Cracked Concrete


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Title: Expansion Anchor Performance in Cracked Concrete

Author(s): R. W. Cannon

Publication: Journal Proceedings

Volume: 78

Issue: 6

Appears on pages(s): 471-479

Keywords: anchorage (structural); anchors (fasteners); beams (supports);bolted connections; control joints; cracking (fracturing); cyclic loads; deflection;expansion; load factors; loads (forces); reinforced concrete; safety factor;stresses;structural design;tests.

Date: 11/1/1981

This report covers the cyclic testing of self-drilling expansion anchors in the cracked portions of reinforced concrete beams. A number of parameters were considered for the three beams tested: anchor type and number, steel ratio and beam capacity, flexibility of attachment, loading frequency and magnitude, and coincidence of beam cracking with anchor location. Cracking of the beams at factored loading occurred at 50 percent or more of the anchors. The principal factor affecting anchor performance appeared to be the rigidity, or flexibility, of the connecting plate or attachment. For rigid attachments, expansion anchors generally became unstable at less than 200 cycles of factored loading, whereas flexible attachments generally maintained stability for upward of loo0 cycles. It then appears that if the attachment is flexible, expansion anchors are fully capable of withstanding safe shutdown earthquakes with design safety factors as low as three for maximum loading conditions. For rigid attachments, a higher safety factor should be imposed.