Concrete breakout strength

Concrete Breakout Strength of a Group of Anchors in a Rectangular Pattern in Shear... 

In accordance with ACI 318 Appendix D, the concrete breakout strength of a group of anchors in a rectangular pattern in shear should be taken as the controlling value of the following ... 

The concrete breakout strength of the row of anchors farthest from the front edge perpendicular to the direction of force, if closed shear ties or other mechanisms are used to transfer the load from the row of anchors closest to the front edge to the row of anchors farthest from the front edge. (See Figure 3.12.)... 

The load transfer method outlined in this section is based on the requirements listed in ACI 318 Appendix D. In the petrochemical industry, the unreinforced concrete breakout strength in tension and shear is rarely sufficient to exceed the ultimate anchor strength. 

It is a construction preference to keep the anchors inside the pedestal and not extend them into the mat or footing. However, in some cases this may not be practical. If the anchor extends into the mat, the concrete breakout strength in the mat must be checked with the effective embedment depth measured from the top of the mat (Figure 3.4) assuming reinforcement is not adequately lapped to transfer the tension. 

Calculate the concrete breakout strength of the plate shear lug in shear. (The method shown in Example 3 is from ACI 349-06 Section D. 11. 

Note The stress area is calculated using 45 degrees as opposed to the approximate 35 degrees used for the concrete breakout strength of anchors.)... 

The tension and the shear forces in the anchors are transfered to the longitudinal rebars and shear reinforcement, respectively, which will be designed as anchor reinforcement. Therefore, the concrete breakout strength in tension and shear (D.5.2 and D.6.2) is not checked. The concrete pryout strength in shear (D.6.3) is assumed OK by inspection because it is usuaiiy criticai for short and stiff anchors. 

Check concrete breakout strength of the shear lug in shear. 

Wey, E., Hayes, T., Naqvi, D. (2010), Concrete Breakout Strength in Tension for Vertical Vessel Anchorage in Octagon Pedestals, Proceedings of the Structures Congress, American Society of Civil Engineers Reston, VA. 

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