Insufficient ductility and lack of integrity have caused extensive damages and undesirable responses in masonry buildings in past earthquakes. These types of structures are distributed all over Iran and the vulnerability assessment of such structure is one of the main concerns between structural engineers. Developing an advance finite element model to simulate the behaviour of a masonry structure is a very complicated procedure which may not be practical and applicable in most cases, so many attempts have been performed to find simple methods for analysing these structures. The Equivalent Frame Method is one of the well-known methods which is rather simple and could be used for vulnerability assessment of some historical structures like Iranian caravanserais. The architectural configurations of Iranian caravanserais were regular and symmetric. When the arrangement of walls and openings are modular it is convenient to model the piers and spandrels as a frame type columns and beams. The simplicity of the conventional Equivalent Frame Method sometime leads to an inaccuracy of the assessment, therefore some modification for the upgrading of this method has been proposed. Using the shell elements beside the frame elements in a modelling procedure may eliminate some disadvantages of the conventional Equivalent Frame Method. In this study a modification has been proposed to improve the upgraded Equivalent Frame Method ability in predicting the failure modes of the masonry walls such as, toe crashing. The proposed modification has been used in the static nonlinear analysing of a masonry structure by the Equivalent Frame Method. The given results have acceptable reconciliation with practical reality and it seems to be useful, especially in a rapid assessments.