www.seismictest.itu.edu.tr/en/index.html Full-scale on site seismic tests by Istanbul Technical University (ITU). Project performed by Istanbul Technical University and supported by Istanbul Development Agency (Istanbul Kalkınma Ajansı ISTKA). Project Team: Alper Ilki (Project Leader) Cem Demir, Caglar Goksu Akkaya, Mustafa Comert, Ali Osman Ates, Pinar Inci, Ugur Demir, Erkan Tore, Ilyas Saribas, Ozgun Ozeren, Alvand Moshfeghi, Soheil Khoshkholghi, Ali Sanver, Ufuk Yazgan, Kutay Orakcal Short Summary: In scope of this project, static and dynamic tests were carried out on two full scale substandard reinforced concrete buildings (Building-1 and Building-2). The aim of the tests was to investigate the seismic performance and obtain the dynamic characteristics (modal frequencies, mode shapes, damping ratios) of these substandard buildings at different levels of seismic damage. Building-1 is an existing building more than 20-years-old, which was demolished partially to obtain the 3-story test structure. Since, in case of Building-1, axial load levels were quite low (around 10% of the axial load capacity of the columns), columns were slightly stronger than beams (strong column-weak beam), and the material characteristics were not homogeneous, Building-2 was constructed on the same site with smaller column cross-sections (strong beam-weak column) and higher column axial loads (approximately 25% of the axial load capacity of the columns). The buildings had concrete compressive strength of 13.5 MPa and 10 MPa, and were constructed with plain reinforcing bars. The reinforcement detailing (such as lap splices, stirrup spacing, hooks etc.) of both buildings was also representative of relatively older existing structure stock. In the quasi-static lateral loading part of the study, both buildings were subjected to lateral displacement cycles exerted by the hydraulic actuators positioned at the lower first and second story slab levels. A 50 cm thick reinforced concrete reaction wall, which allowed the testing of both buildings consecutively in a short period of time, was built for supporting the actuators. The reaction wall and the buildings were resting on a 60 cm thick mat foundation that restrained the rocking behavior. The vertical loads were maintained by utilizing the self-weight of the structures. Observations and measurements made during the tests addressed to different failure modes for each building which had different column axial load levels and column/beam bending capacity ratios. The observed failure mechanisms were also similar to ones observed in existing structures after major earthquakes. In addition to observations on evolution of damage, lateral load-story displacement curves, column and beam rotations were also obtained and compared with the nonlinear structural analysis results. In the dynamic testing, firstly, modal analyses of the building were performed so that the dynamic characteristics could be estimated. Then, forced and ambient vibration tests were carried out at the site for obtaining the dynamic characteristics of the buildings. The excitations were recorded using piezoelectric accelerometers. Dynamic tests were conducted before and after each quasi-static cyclic loading. The dynamic tests were performed at a set of damage levels, for observing the rate of changes of the dynamic characteristics with the increasing damage. For forced vibration tests, buildings were excited via eccentric mass shaker by applying a sinusoidal forcing in a frequency band of 1 Hz to 15 Hz. According to test results, it was observed that the modal frequencies tend to decrease while damping ratios for the different modes tend to increase with the increasing levels of damage. For more information: www.seismictest.itu.edu.tr/en/index.html

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