A new design model for anchorages with flexible elastic base plate for concrete breakout failure under tension loads

Abstract The current codes and standards for the design of anchorages against concrete cone breakout failure require the base plate to be rigid such that each anchor is subjected to almost equal load under concentric tension, and there is a linear distribution of anchor forces for groups under eccentric tension or bending. These are the basic requirements for the application of concrete capacity design (CCD) method, but in many cases, satisfying these requirements may need a rather thick base plate, which gets impractical. Using the CCD method for design of anchorages with flexible base plates (resulting in nonlinear distribution of anchor forces) can lead to rather unsafe designs. In this article, a new method for design of anchor groups with flexible base plate is proposed that modifies the resistance obtained by the CCD method based on the anchor force distribution to obtain the resistance valid for the anchorages with flexible base plate. First, the analytical method is conceptualized for its validity on simple cases and then it is extended for its application to more complicated cases. The results of the calculation method are compared and validated by the results of few available tests and further on several cases analyzed using the nonlinear spring model. The comparison of results show that the proposed method is suitable for the design of anchor groups with any given base plate thickness that results in a linear or nonlinear anchor force distribution.