Supposed we have 2 same anchors ¾” – 6 ¾” emb. with 3 ¾” edge distance, the first one will be installed on the uncracked concrete foundation (f’c=30Mpa), while the second one will be installed on the cracked concrete foundation (f’c=30Mpa)
1. The first anchor will have the maximum tension Tr=17.97 kips x 0.3 (load adjustment factor) = 5.4 kips
2. The second anchor will have the maximum tension Tr=12.575 kips x 0.54 (load adjustment factor) = 6.8 kips
the results tell us the anchors will have the larger resistance if the foundation is cracked or in bad condition.
Hi Ying,
This difference is due to the assumptions of minimum concrete thickness with 6,000 psi concrete compressive strength in the simplified tables for the tension reduction factors. These assumptions for uncracked concrete increase the calculation for critical edge distance, cac, which then reduces the value of the ycp,N factor in uncracked concrete which results in this case the uncracked value to be less than the cracked value. We have the simplified tables setup in this manner to avoid adding additional factors for tension concrete thickness which would lead the reduction factor tables to become very complicated. The simplified method tables aim is speed calculations. When optimized design is required, we recommend the use of Profis Engineering Suite, please see page 20 of the Anchor Fastening Technical guide for more information.