• Structural Engineering and Mechanics
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• v.34 no.1
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• pp.61-84
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• 2010

Presented in this paper is the behaviour of asymmetric building isolated by the double variable frequency pendulum isolator (DVFPI). The DVFPI is an adoption of single variable frequency pendulum isolator (VFPI). The geometry and coefficient of friction of top and bottom sliding surfaces can be unequal. The governing equations of motion of the building-isolation system are derived and solved in incremental form. The analysis duly considers the interaction of frictional forces in the two principal directions developed at each sliding surface of the DVFPI. In order to investigate the behaviour of the base isolation using the DVFPI, the coupled lateral-torsional response is obtained under different parametric variations for a set of six far-fault earthquake ground motions and criterion to optimize its performance is proposed. Further, influences of the initial time period, coefficient of friction and frequency variation factors at the two sliding surfaces are investigated. The numerical results of the extensive parametric study help in understanding the torsional behaviour of the structure isolated with the double sliding surfaces as in the DVFPI. It is found that the performance of the DVFPI can be optimized by designing the top sliding surface initially softer and smoother relative to the bottom one.

• Structural Engineering and Mechanics
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• v.81 no.5
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• pp.633-645
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• 2022

The active tuned mass damper (ATMD) is an efficient and reliable structural control system for mitigating the dynamic response of structures. The inertial force that an ATMD exerts on a structure to attenuate its otherwise large kinetic energy and undesirable vibrations and displacements is proportional to its excursion. Achieving a balance between the inertial force and excursion requires a control law or feedback mechanism. This study presents a technique for the optimum design of a sliding mode controller (SMC) as the control law for ATMD-equipped structures subjected to earthquakes. The technique includes optimizing an SMC under an artificial earthquake followed by testing its performance under real earthquakes. The SMC of a real 11-story shear building is optimized to demonstrate the technique, and its performance in mitigating the displacements of the building under benchmark near- and far-fault earthquakes is compared against that of a few other techniques (proportional-integral-derivative [PID], linear-quadratic regulator [LQR], and fuzzy logic control [FLC]). Results indicate that the optimum SMC outperforms PID and LQR and exhibits performance comparable to that of FLC in reducing displacements.

• Geomechanics and Engineering
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• v.36 no.5
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• pp.455-464
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• 2024

Seismic movements have varying effects on structures based on characteristics of local site. During an earthquake, weak soils are susceptible to damage due to amplified wave amplitudes. Soil-structure interaction issue has garnered increased attention in Türkiye, after devastating earthquakes in Kocaeli Gölcük (1999), Izmir (2020), Kahramanmaraş Pazarcık and Elbistan (2023). Consequently, liquefaction potential has been investigated in detail for different regions of Türkiye, mainly with available field test results. Çankırı, a city located close to North Anatolian Fault, is mainly built on alluvium, which is prone to liquefaction. However, no study on liquefaction hazard has been conducted thus far. In this study, groundwater level map, SPT map, and liquefaction risk map have been generated using Geographical Information System (GIS) for the Buğday Pazarı District of Çankırı province. Site investigations studies previously performed for 47 parcels (76 boreholes) were used within the scope of this study. The liquefaction assessment was conducted using Seed and Idriss's (1971) simplified method and the visualization of areas susceptible to liquefaction risk has been accomplished. The results of this study have been compared with the City Council's precautionary map which is currently in use. As a result of this study, it is recommended that minimum depth of boreholes in the region should be at least 30m and adequate number of laboratory tests particularly in liquefiable areas should be performed. Another important recommendation for the region is that detailed investigation should be performed by local authorities since findings of this study differ from currently used precautionary map.