domingo, 13 de setembro de 2009


This report examines reinforced concrete buildings that use moment-resisting frames without ductile detailing to resist seismic loads.

While this building type is predominantly used for office buildings and hotels, it is also used in urban areas for multi-family dwellings (condominiums) and university dormitories.

It can be found in most urban areas across the country, though it is of particular concern in areas of high seismic hazard like California, Alaska, Washington, and Oregon.

Building codes did not include requirements for special seismic detailing of reinforced concrete structures until the 1970's when several earthquakes demonstrated the need for more ductile design.

These buildings are vulnerable to numerous failure modes including: failure of column lap splices; strong beam/weak column failures; captive column failure; punching shear failures in flat plate slabs; and shear and axial load failure of columns with wide transverse reinforcement spacing.

A discontinuity in stiffness and strength at the bottom story, due to a soft story, often results in a concentration of earthquake damage at the building base. Several examples of past earthquake behavior are given in this report as well as discussion of various retrofit options.

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