Abstract: This paper introduces a simplified rock bridge failure model based on the Lajtai’s theory. The model can explain what has been observed in the tests. The shear strength of a rock bridge under various joint combinations can be readily determined using this model. In a simulated joint map, modern optimization methods are used to determine the comprehensive shear strength contributed by the rock bridge and joint combination that offers the least resistance along a specified direction of enforced shear. Shear strength parameters are subsequently summarized using this numerical modeling test by applying a number of normal force.It has been found that this approach is better than the conventional one that employs a single criterion of the joint persistence ratio to find the strength parameters.