Masonry Magazine December 2000 Page. 31
ANCHOR BOLTS in MASONRY
Are you specifying or using the best bolts and correct placement procedures?
By Philip Sarabifizet & Richard E. Klingner
Not all anchor bolts are created equal - not even close. Surprisingly enough, common practice within the masonry industry has been to use weaker anchor bolts, when stronger anchors would cost about the same and could give much better performance. Are you using the strongest anchor bolts? Are you installing your anchor bolts properly? Read on to see how you may be able to achieve better performance with no increase in material or construction costs.
TYPES OF ANCHOR BOLTS
Three main types of anchor bolts are permitted by the Masonry Standards Joint Committee's (MSJC) Building Code Requirements for Masonry Structures (ACI 530/ASCE 5/TMS 402) (referred to from now on as the "MSJC Code") - headed anchor bolts, bent-bar anchor bolts (L- and J- shaped anchors) and plate anchors (Figure 1). Of these, plate anchors are seldom used, and bent-bar anchor bolts are most frequently used. Other types of anchor bolts are permitted, but allowable loads for them must be determined using test data from ASTM E 488.
Figure 1 Types of anchors
headed anchor
bent-bar anchor
plate anchor
The companion specification to the MSJC Code (the Specification for Masonry Structures - ACI 530.1/ASCE 6/TMS 602), requires that plate and bent-bar anchors comply with ASTM A 36/A 36M, and that other anchor bolts comply with ASTM A 307, Grade A. Although the steels prescribed by these specifications can be quite similar chemically, their mechanical characteristics can differ. In particular, the bent region of bent-bar anchors can be brittle. This means that under load, the leg of a bent-bar anchor
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MASONRY-NOVEMBER/DECEMBER, 2000 31