seismic-eng Engineering

The intent is to push plastic hinges into beam ends and keep them out of columns, so the frame dissipates energy through a ductile beam-hinge mechanism instead of collapsing. Columns are the sole gravity-load path; hinges at both ends of one story's columns form a dangerous soft-story mechanism that can drop that story and trigger progressive collapse. Hinges distributed over many beam ends rotate harmlessly while the story keeps carrying load. Codes therefore require the sum of column flexural capacities at a joint, times an amplification factor, to exceed the sum of beam capacities, with stricter rules for corner columns.

Rubber bearings between building and ground lengthen the natural period away from the quake's dominant frequency, greatly reducing motion, like floating the structure on a soft layer.

A lead rubber bearing stacks rubber layers bonded to thin steel shims around a central lead core. The flexible rubber lengthens the building's fundamental period from about 0.5–1 s to over 3 s, away from the band where earthquake energy concentrates, so the acceleration reaching the superstructure falls sharply. The lead core yields in shear, dissipating energy and capping displacement, yet stays stiff under wind and minor tremors, letting the building sway almost rigidly instead of deforming storey by storey.