Calibration of three-strut macro model for solid masonry infill walls in reinforced concrete frames

This study presents a sensitivity analysis and calibration of solid infill walls, without openings, embedded in reinforced concrete frames, aiming to propose a simplified force–deformation model with a code-relevant three-strut macro modeling approach that reflects the best combination of its controlling parameters at inelastic drift levels. The sensitivity analysis considers the range of infill wall material properties as well as the lateral force–drift relationship parameters for the three-strut model. Experimental results obtained from available investigations are used to validate the numerical modeling and calibrate the parameters. The results demonstrate that the post-yield stiffness in the tri-linear material model and the tensile strength of the infill wall along the diagonal direction are the parameters governing the nonlinear response of infilled reinforced concrete frames. To better describe the behavior of infill walls without openings using the three-strut model, we propose a validated set of equations and calibrated parameters. The proposed modeling methodology provides a good match with experimental results and with the equivalent strut width formulas specified as in ASCE 41-23 FEMA273 and FEMA 356, but only when consistent lateral force–drift relationship parameters are applied.