Modal Identification Results of Quasi-statically Tested RC Frames at Different Damage Levels

Abstract

This paper presents modal parameter identification results of two half scale reinforced concrete (RC) portal frames experimentally tested under quasi-static cyclic loading. One of the RC frames is without infill and the other one is with hollow-fired clay brick infill. The frames are progressively damaged in in-plane direction by applying increasing drifts by a displacement controlled actuator at the floor level. At each pre-determined damage states (levels), the actuator is detached from the specimen, and dynamic tests are performed. In-plane dynamic excitation used for modal identification is applied by an electro-dynamic shaker placed on the slab level. Besides, impact hammer and ambient vibration tests are also used. NExT-ERA, EFDD, and SSI-Data are the modal identification techniques used for modal parameter estimations. The purpose of the paper is multi-fold: (i) identify modal parameters of code conforming RC frames with and without infill walls at different damage levels, (ii) follow the evolution of damage level vs. associated damping ratio estimations which can potentially be used for reference-free damage level detection, and (iii) quantify the effect of broadband excitation provided by an offline shaker tuning technique on modal identification results.