Erdal ŞAFAK
Abstract
Rapid developments in monitoring hardware and communication technologies in recent years have accelerated the installation of Structural Health Monitoring (SHM) systems in structures. The main reasons we monitor structures include the following: determine in-situ dynamic characteristics, check the design and analysis methods used, improve structural design codes, develop new retrofit and strengthening techniques, predict behavior for future extreme loads, detect and locate damage after an extreme event, and develop instantaneous damage distribution and loss maps. Consequently, a large number of structures are now being instrumented, and data sets from instrumented structures, particularly from multi-story buildings, are now available for researchers. Analyses of SHM data are providing more insight into the dynamic behavior of structures, as well as showing the need for new monitoring hardware and analysis tools. On ground motion, analyses of monitoring data have shown the importance of surface waves for long-period structures, and the effects of rotational component of ground accelerations in tall buildings. Related to structural response, the data have shown the contributions of floor rotations to story forces and inter-story drifts, the effect of building weight on horizontal forces and displacements, particularly in tall buildings and buildings with soft first stories, the common presence of bi-axial coupled modes, and low and non-proportional damping in high-rise buildings. Related to hardware, the monitoring has revealed the need for rotational sensors, especially in upper floors of tall buildings, and the advantages of using laser-based displacement sensors and GPS sensors. In terms of data analysis, it is found that the classical spectral analysis tools may not be sufficient to extract frequencies in noisy ambient vibration records, and more advanced tools are needed based on simple statistical techniques. Several examples are presented to support above statement by using real data from instrumented structures.
Keywords
Monitoring hardware,
Structural health monitoring (SHM) systems,
Multi-story buildings,
Building weight,
Frequencies.
