Question

Earthquake resistant building construction

Answer 1

According to the Uniform Building Code (UBC), which has been adopted widely by inspection authorities throughout the country as a standard for all new construction, wood-frame structures with concrete or reinforced masonry foundations must be affixed to their bases by a specific method: First, anchor bolts of at least 1/2" in diameter (most builders use hardware that's 5/8" in diameter by 10" long) are embedded vertically 7" or more into the foundation — all along the perimeter, at intervals of no more than 6' — with a portion of each bolt projecting above the mortar or concrete. Then the building's sill plates (the bottommost, horizontal wooden members of a frame structure) are drilled so they'll slip down over the protruding anchor bolts, and once the plates are set in place — flush against the foundation — nuts are tightened down onto the wood.


This method of anchoring sill plates does keep the boards attached to the foundation during an earthquake, but it fails to help the structure as a whole absorb and withstand the forces of seismic shock. However, my technique — a simple variation of the standard procedure — allows a building to move with its foundation during the course of a quake, and also provides a bit of flexibility and cushioning between the base and the sill . . . thus offsetting at least some of an upheaval's shearing effect.