AbstractThis paper presents an explicit finite-element (FE) model formulated using the continuum shell element to examine the behavior of unreinforced and externally strengthened masonry walls. Masonry is modeled as a homogenized material capable of producing elastic and inelastic behavior with distinct directional properties. The macroscopic properties of masonry are defined using a Hill-type and a Rankine-type yield surface to model its behavior under compression and tension, respectively, which are embedded in a VUMAT user material subroutine developed using the ABAQUS Explicit algorithm. Alongside the mechanical properties of masonry, the thickness direction properties of the continuum shell element are defined through the input file to ensure compatibility between the algorithm used in the VUMAT and the continuum shell formulation. The parameters of the FE model have been validated with the test data sets of a total of six out-of-plane and in-plane loaded masonry walls taken from three separate experimental programs reported in the literature. A close match between the experimental and FE model failure mode and load–displacement relation was observed. The model is extended to predict the behavior of externally strengthened walls, which experienced the debonding of the carbon fiber-reinforced polymer (CFRP) layers from the masonry substrate. A significant increase in the in-plane capacity of the strengthened walls was observed.