Research On The Control Of The Torsional Effect Of Irregular Structure

With constant development of construction technology, construction shapes and functions are becoming increasingly diversified, and buildings of irregular shapes and uneven rigidity are growing increasingly. Since there exists certain eccentricity in irregular building, namely the mass center is offset from the rigidity center, it will cause severe torsion damage under earthquake. The application of foundation isolation technology can effectively reduce earthquake effects on upper structures. For buildings more eccentric to upper structure, control on position of mass center and rigidity center of isolation layer through rational layout of isolation support can effectively reduce torsion damage for buildings.In the thesis, the author applies SAP2000 software to establish an irregular frame structure model and selects four structure models. Firstly, traditional anti-seismic (non-isolation) structure model. Secondly, it adopts isolation structure model with lead-core rubber bearing. Thirdly, combined isolation structure model with larger eccentric distance (which consists of rubber bearing and sliding bearing, the rigidity center of isolation layer is offset from the mass center of upper structure). Fourthly, combined isolation structure model with extremely small eccentric distance (which consists of rubber bearing and sliding bearing, and the rigidity center of isolation layer is basically coincided to each other). Input seismic oscillation to analyze nonlinear time-history of earthquake response and study building isolation effect.The results of the research show that:1.Compared with traditional anti-seismic structures, both all-rubber bearing isolation system and combined isolation system can reduce earthquake response and reduce acceleration and interlaminar shear on floors of upper structure, thus reducing torsion effect, interlaminar torsion angle and interlaminar torque of irregular buildings.2. On the premise of not changing number of bearings on isolation layer, combined isolation system can absorb more seismic oscillation energy than full-rubber isolation system, and reduce the maximum interlaminar shear and maximum interlaminar torsion angle of upper structures.3. In case of types and quantities of bearings on isolation layer being the same, compared with combined isolation system with larger eccentric distance, the combined isolation system with smaller eccentric distance, acceleration on floors of upper structure is basically the same as the maximum interlaminar shear. However the interlaminar torsion angle of the former are reduced obviously, able to well inhibit torsion effect of upper structure of irregular buildings.