Eleventh U.S. National Conference on Earthquake Engineering Integrating Science, Engineering & Policy June 25-29, 2018 Los Angeles, California APPLICATION OF ROTATION RATE SENSORS TO MONITORING OF STRAIN IN CIVIL ENGINEERING STRUCTURES Z. Zembaty 1 P. Bońkowski 2 , P. Bobra 2 , S. Kokot 3 and J. Kuś 3 ABSTRACT Vibration-based damage estimation of many civil engineering structures, particularly reinforced concrete (RC) or masonry, is a challenging task because these types of structures are cracked even at moderate loads. Numerous, non-destructive damage evaluation (NDE) methods have emerged to monitor the state of such civil engineering structures. Most of them use optical fibres or sensors embedded inside of the concrete. This paper proposes an alternative and much simpler approach. By putting rotation rate sensors in selected places, one may indirectly measure strain during strong seismic vibrations. Furthermore, by attaching two rotation rate sensors to a structural joint, one can also monitor on-line plastic hinge development in a RC frame or steel structure under strong seismic excitations. To check the potential of this new Structural Health Monitoring (SHM) technique, an experiment at laboratory scale was carried out in which rotation rate sensors were put in the middle of a model, cantilever plexiglass beam, together with a system of strain gages. The sensors were of the “horizon” type, used in aviation. The beam underwent kinematic excitations during which the rotations and strains were simultaneously observed. The experiments demonstrated very good strain sensing from measurements of the beam axis rotations, good sensitivity to localize stiffness drops and even positive results of vibration-based stiffness “reconstruction”. The latter may serve in post-earthquake damage assessment for low level, diagnostic harmonic excitations. With the further development of rotational sensors to increase their accuracy, they could extend the inventory of NDE for civil engineering structures. 1 Professor, Faculty of Civil Engineering and Architecture, Opole University of Technology, 45-758 Opole, ul. Proszkowska 76, Poland (email: z.zembaty@po.opole.pl) 2 Graduate Student Researcher, Faculty of Civil Engineering and Architecture, Opole University of Technology, 45- 758 Opole, ul. Proszkowska 76, Poland 3 Assistant professor, Faculty of Civil Engineering and Architecture, Opole University of Technology, 45-758 Opole, ul. Proszkowska 76, Poland