The Study Of Structures With Dissipation Devices For End Offsets Using Force Analogy Method

Structures with dissipation device have clear mechanism and outstanding effect of reducing structural responses, which leads to a wide use in structure design and strengthening. But usually, structures with dissipation devices perform inelastic under severe earthquakes. Among numerical methods of inelastic analysis, force analogy method is an effective way which changes displacement rather than stiffness. Nowadays, in the inelastic analysis of moment-resisting frames using force analogy method, plastic hinges are assumed to be occurred at the end of beams, which leads to drawbacks of inductility and disagreement with seismic hazards. In Earthquake Resistant Design Code, plastic hinges are supposed to offset from the end of beams. Therefore, end offsets have great practical significance and need to be researched. Based on these, works have been done on these aspects:1) In the analysis of one-story one-bay moment-resisting frame, end offsets in beams and columns are considered, and structure with viscous damper is studied specifically. Based on beam element with end offsets, stiffness matrix is deduced. On the basis fundamental theory of force analogy method, displacement is considered as a variable. With the partition of stiffness matrix and static condensation, DOFs caused by end offsets and rotational DOFs are condensed out, which leads to the improvement of force analogy method and foundation of structure with dissipation device with end offsets. For working conditions with and without end offsets, numerical analysis is carried through. Results show that with end offsets, story drift changes little while acceleration and restoring forces of dissipation device differs a lot, which offers preliminary conclusion for structure engineering.2) Base on force analogy method, energy equation is founded with end offsets. By numerical analysis, energy of different types and distribution are obtained, with the plastic energy analysis of possible plastic hinge locations. With end offsets, scale of different energy by structural energy dissipation is affected greatly.3) In the analysis of MDOF system, considering about end offsets in beams, structural responses and energy are researched by changing sections in bottom columns and parameters of end offsets. Structural responses in floors and plastic hinges distribution are studied with and without end offsets, with displacement, acceleration, restoring forces and hysteresis loops of dissipation devices, plastic rotations, and energy curves obtained. It is concluded that end offsets effect a lot in these responses. On the basis of force analogy modal of structures with dissipation devices with end offsets, plastic hinge locations are specified either, which provide foundations in completing force analogy method.