PROFIS ENGINEERING
OVERVIEW
This design guide provides information on PROFIS Engineering functionality and design assumptions when performing shear concrete breakout calculations. The design guide explains how PROFIS Engineering extrapolates ACI 318 anchoring-to-concrete provisions to consider shear concrete breakout for anchorages consisting of multiple anchor rows / columns having multiple anchors in each row / column. It references the shear concrete breakout provisions in ACI 318-19 Chapter 17, Section 17.7.2. Other ACI 318 code versions have similar provisions; however, reference should be made to the code version being used to determine the relevance of the information given in this design guide with that code.
In this design guide, an anchor“ row” is defined as a set of anchors oriented in the x direction, loaded by a common plate or fixture, having the same edge distance in the direction of the applied shear load( c a1, row n). An anchor“ column” is defined as a set of anchors oriented in the y direction, loaded by a common plate or fixture, having the same edge distance in the direction of the applied shear load( c a1, col n). Reference Figure 1 [ 2 ] below.
Figure 1.
Formation of a shear concrete breakout failure surface depends on which anchors are resisting shear load. Anchors resist shear load via contact with the plate or fixture being attached. Shear load can be redistributed from one row / column to another row / column if the spacing in the direction of the load is sufficient to permit formation of a complete failure surface from each row / column being considered. Rigidly attaching( e. g. welding) anchors to the plate / fixture permits shear load redistribution to the anchor row / column farthest from the fixed edge being considered regardless of the spacing( s) in the direction of the applied shear load. Anchors not rigidly attached to a plate or fixture have an annular space between the anchor and plate / fixture. Shear load can be redistributed from one anchor row / column to an adjacent row / column only if the spacing in the direction of the load is sufficient to permit formation of a complete failure surface from each row / column being considered. In the PROFIS Engineering anchor portfolio, AWS D1.1 headed studs are an example of rigidly attached anchors, while ASTM F1554 headed bolts and Hilti post-installed anchors are examples of anchors that have an annular space between the anchor and plate / fixture.
ACI 318-19 provisions defined as“ Case 1”,“ Case 2” and“ Case 3” permit consideration of shear concrete breakout for multiple anchor rows / columns. All three cases may be relevant for anchors not rigidly attached. Case 2, or possibly Case 3, are relevant for anchors rigidly attached.
ACI 318 Provisions for Shear Acting on Multiple Rows or Columns
ACI 318-19 anchoring-to-concrete provisions for considering shear concrete breakout failure require calculation of a nominal concrete breakout strength in shear( V cb( g)), which is multiplied by a strength reduction factor( ϕ-factor) to give a design concrete breakout strength in shear( ϕV cb( g)). This design strength is checked against a factored shear load( V ua): check ϕV cb( g) ≥ V ua. The ACI 318-19 equations for calculating nominal concrete breakout strength in shear are as follows:
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