| The main contribution of this investigation is the development of a two-dimensional computational model for infill walls. Two basic equations are used to prescribe the behavior of an infill wall; the first defines the strength envelope, and the second the hysteretic loops. The infill is idealized with six compression-only, inclined struts which follow the behavior defined by the strength envelope and hysteretic loop equations. Three parallel struts are used in each direction, and the off-diagonal struts are located to represent the interaction between the infill and confining steel frame at locations along the beam-column spans where plastic hinges have been observed to form.; The advantages of the analytical model which is implemented in an interactive-graphics computer program are the following: (a) both strength and stiffness degradation of infill walls are modelled; (b) the parameters of the model have physical meaning and can be readily adapted to fit experimental data; (c) the off-diagonal struts allow modelling of the interaction between the infill and the bounding frame, such as the formation of hinges along frame members; (d) local behavior, such as the effects of openings, lack of fit, and interface conditions, can be modelled; (e) the strength envelope and hysteretic-loop equations provide smooth continuous curves; and (f) both material and geometric nonlinearities of the frame members are modelled.; Three structures are analyzed each with and without infill walls: a one-story one-bay, a two-story three-bay and a ten-story three-bay. The conclusions of the study are the following: (a) The axial forces in the members of the bounding frame are significantly affected by the presence of infill walls, (b) infill walls reduce the bending moments and shear forces of infilled structures, (c) walls at the lower floors are damaged more extensively than the ones at the upper floors, (d) the location of the damaged walls determines which members of the frame undergo plastic deformations, and (e) infill walls reduce considerably the number of members that undergo plastification and the number of loading and unloading cycles of these plastic hinges. |
