An analytical macromodel based on an equivalent strut approach integra
ted with a smooth hysteretic model is proposed for representing masonr
y infill panels in nonlinear analysis of frame structures. The hystere
sis model uses degrading control parameters for stiffness and strength
degradation and slip ''pinching'' that can be implemented to replicat
e a wide range of hysteretic force-displacement behavior resulting fro
m different design and geometry. The paper presents the development of
the hysteretic model and the definitions of the control parameters, w
hich can be determined using any suitable theoretical model for masonr
y infills. An available theoretical model for simplified engineering e
valuation of masonry infilled frames was explored for estimating the c
ontrol parameters of the proposed macromodel. The macromodel was incor
porated in a nonlinear structural analysis program, IDARC2D Version 4.
0, for quasi-static cyclic and dynamic analysis of masonry infilled fr
ames. Simulations of experimental force-deformation behavior of protot
ype infill frame subassemblies are performed to validate the proposed
model. A lightly reinforced concrete frame structure is analyzed for s
trong ground motions to evaluate the influence of masonry infill panel
s on the dynamic response.