Dynamic Identification and Structural Behavior of an Irregular School Building

In recent years the detection of environmental vibration represents an effective and accurate technique to characterize the dynamic response of buildings to seismic excitation. In this work, a dynamic monitoring of a case-study was performed based on measurements of environmental vibrations. The case-study consists of a 3-storey masonry school building, which was subjected to a structural and functional recovery intervention about twenty years ago. It has a rectangular plan, but it evidences an irregular distribution of stiffness, mostly due to the recovery intervention, which introduced resistant elements irregularly spread in the plan. The dynamic response was monitored with two seismic stations positioned at each floor of the building; frequency values and modal forms were evaluated by analyzing data in the frequency domain. The first two side modes, as well as a torsional mode, have been detected. The dynamic information provided by the experimental analysis was compared with that found by the analytical modal analysis, performed through an Equivalent Frame Modelling (EFM) software. Finally, the dynamic response of the building has been checked with regards to the current Italian code, evidencing the effects of the irregular distribution of the new elements on the structural response of the system.