The vibration monitoring in buildings is very important in order to control the structure integrity, to increase the human safety and to evaluate the human disturbance. It is fundamental in case of new construction located in high seismic zones.
The vibration monitoring can give important information about risk assessment of a building, both in direct terms (acceleration/velocity) and indirect terms (frequency, post-processing analyses).
The most important applications are:
Strong motion monitoring
It is dedicated to buildings in high seismic zones, as defined by local or national geophysical institutes. The standard configuration includes three to four triaxial accelerometers. One in the free field, when it is possible, to properly record the earthquake input motion and three inside the buildings located typically at the foundation, middle and top floors. The units are typically placed on the ground floor mount or vertically wall mounted, on the load-bearing walls of the structure.
The analyses according to the structural damage norms are needed for buildings around a construction site. The typical configuration is with 3 tri-axial sensors (accelerometers or geophones) inside the building, close to the load-bearing walls. The most important features are the velocity peaks and maximum frequencies, calculated according to the main international standards, such as DIN 4150-3 and SN 640312.
The analyses related to the human comfort evaluation are usually connected to structural damage measurements or noise measurements. Typically, a tri-axial sensor (accelerometer or geophone) is placed inside the building, in a place particularly sensitive for the people disturbance, like the bedroom for example. The most important standards are DIN 4150-2 and ISO 2631.
The modal analysis is a collection of algorithms and techniques for the characterization of the structures, by obtaining natural frequencies, damping factors and mode shapes. It is mainly required for the design and testing of newly built structures to prevent resonance conditions. Depending on the structure, the number and the typology of the accelerometers could be very different. In case of unknown excitation input, the procedure is called Operational Modal Analysis (OMA).