The structural identification of the infill walls contribution in the dynamic response of framed buildings

Reinforced concrete (RC) frame buildings containing unreinforced masonry infill walls are commonly used in structural systems around the world. The performance of this type of building can be significantly affected by the presence of infill walls according to their type and distribution in the plane and along the height as revealed by earthquakes. This paper presents data collection, system identification, and finite element modeling of an existing RC framed building designed for gravity loads and containing unreinforced masonry infill walls. Based on a previously carried out ambient vibration test, a three-dimensional finite element model, comprising infill walls and partitions, was successfully updated on the basis of the global modes identified by the in situ test, pointing out the important role of the nonstructural components for this type of building. The influence of the infill walls and partitions on the vibration period was examined, introducing a comparison with simple formulations for the period calculation suggested by codes or available in the literature. The updated model has been further used to assess an approach for an approximate estimation of the story and global stiffness of the building considering the effect of the secondary elements. The dynamic test with the model updating results an efficient procedure for a complete identification of the elastic behavior of the structure.