ASSESSMENT OF DAMAGE AT THE LOCAL SCALE OF REINFORCED CONCRETE GATES BY DYNAMIC MEASURES

Abstract

The applications of dynamic measurements on the struc-tures of existing buildings are numerous: the verification ofthe seismic vulnerability of structures, the auscultation ofthe structure’s capacities in post-earthquake situations orafter changes in the vicinity, etc. At present, this type ofmeasurement enables the diagnosis of a structure on aglobal scale (the whole structure), while the identificationand location of local damage (each element of the struc-ture) remains to be explored. Diagnosis at the local scalewas studied in the laboratory on an instrumented structureconsisting of two columns and one beam (H form). It wasloaded in the central part of the beam in several stagesuntil it broke. Displacements were measured simultane-ously using displacement sensors and image correlation.After each load/unload cycle, dynamic measurements weretaken using accelerometers. In the first part of this paper, the observations from theexperiment are presented, with the appearance of damageand the decrease in natural frequencies that occurredsimultaneously with stiffness. Thereafter, the techniquecharacterizing damage that was developed taking intoaccount the semi-rigid connections of the frame is pre-sented. The stiffness of the connections was identified bycalibrating the dynamic responses of the structure withrespect to a model. The fixity factors were used to assessthe loss of stiffness in the semi-rigid connections. Thevalidity of the fixity factors identified was evaluated usingthe static experimental results.This study shows that dynamic measurement coupled withfinite element analysis can provide a fast and effectivemethod to assess the quality of connections of reinforcedconcrete structures.