11/12/2022 0 Comments Design of headed anchor bolts pdf![]() ![]() As embedment depth increases further, a headed anchor will eventually fail by yield and fracture of the anchor steel. In contrast, the capacity of headed anchors is controlled by breakout, is significantly higher, and increases with embedment depth. The capacity of bent-bar anchors is always controlled by pullout, and is quite low. Pullout capacity is calculated assuming that no special measures are taken to remove oil from the anchor shank. The pullout failure mode applies to bent-bar anchors only. For example, the draft MSJC strength design provisions include different formulas for calculating tensile anchor capacity as governed by yield and fracture of the anchor shank, by tensile breakout, and by pullout. ![]() Research studies show that headed anchors in masonry, loaded in tension, fail either by yield and fracture of the anchor shank, or more typically by breaking out a piece of masonry.ĭifferences in performance between headed and bent-bar anchors are recognized in other design provisions. Because the Code allowable loads are intended to be safe for all types of anchors, they are very conservative for headed anchors. The equations are based on research results for all types of anchor bolts. It does not distinguish among plate, bent-bar and headed anchors. What the MSJC Code Requires and What the Test Results ShowThe current MSJC Code contains a single set of equations for calculating the allowable capacities of anchor bolts. This does not happen with headed anchors. This means that under load, the leg of a bent-bar anchor can suddenly fail, causing the anchor to pull out of the masonry. ![]() In particular, the bent region of bent-bar anchors can be brittle. Although the steels prescribed by these specifications can be quite similar chemically, their mechanical characteristics can differ. 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. Other types of anchor bolts are permitted, but allowable loads for them must be determined using test data from ASTM E 488. Of these, plate anchors are seldom used, and bent-bar anchor bolts are most frequently used. Types of Anchor BoltsThree 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. ![]()
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