Anchor Reinforcement Design

When the concrete has insufficient strength to resist tension and shear loads, reinforcing steel must be designed to transfer the loads into the base concrete. 

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. 

Previous editions of ACI 318 recognized the beneficial effects of supplementary reinforcement across the potential concrete breakout cone when evaluating the strength of an anchor. In order to reduce some confusion about this reinforcement, ACI 318 now defines two types of reinforcement that can be used across a potential breakout cone supplementary reinforcement and anchor reinforcement. 

Anchor reinforcement is designed and detailed specifically to transfer the full design load from the anchors into the structural member. An explicit design and full 

The concrete reinforcement needed to develop anchor loads shall be designed in accordance with ACI 318 and the following  

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ACI 318 Sections RD.5.2.9 and RD.6.2.9 state that in sizing the anchor reinforcement, the use of strength reduction factor (j) = 0.75 is recommended as is used for the strut-and-tie models (ACI 318 Section 9.3.2.6), implying that the use of the STM design approach in designing anchor reinforcement is an acceptable design approach. 

If, as in the case of a column pedestal, there is insufficient concrete to resist the tension or shear, reinforcing steel can be designed as anchor reinforcement. (See 3.5.) This can be considered a ductile design since both the anchor and the reinforcing steel are ductile. 

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. 

A free standing configuration for the Reactor Pool, resting on a common foundation mat, but structurally decoupled from the RB, designed for a RG. 1.60 Safety Shutdown Earthquake excitation anchored to 0.3 g, presents reasonable wall thicknesses and reinforcing bar densities. 

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