| Extreme Masonry: Earthquakes
Masonry Home >
Products and Properties > Extreme Masonry:
Earthquakes
Earthquakes Prompt Masonry
Code Changes
Earthquakes are dramatic events. Sometimes, they occur unexpectedly
or with very little warning. They are frequently short-lived and
can pack strong forces into a short period of time. Earthquakes
also place great accelerations onto structures. Their short durations
notwithstanding, earthquakes can do extensive damage.
 |
| Typical force-displacement response of a masonry wall |
Building codes are designed to provide protection of human lives
and physical property. As codes have been shifting to consider longer
periods of time over which events occur, there has been an increase
in the magnitude of earthquakes being designed for, even though
the likelihood of such an event occurring is decreased.
Various groups, such as The Masonry Society, have members who study
building behavior during past earthquakes to learn as much as possible
about structural performance of masonry subjected to seismic forces.
They use that information to modify design criteria and building
codes, making buildings safer.
| Six major events in the response of a masonry
shear wall: |
 |
 |
The footprint of seismic zones is increasing and building requirements
are changing. As a result, all buildings are expected to resist
greater demands from potential seismic events. Existing masonry
structures provide an opportunity to verify designers’ assumptions
regarding structural response to seismic forces. Buildings that
perform well demonstrate the effectiveness of a design methodology;
buildings that perform less well make it possible to locate deficiencies
and revise design approaches to improve structural behavior.
 There
are two general classes of masonry structures: reinforced and unreinforced.
Unreinforced masonry (URM) is less ductile than reinforced masonry,
and ductile structures typically perform better in earthquake events.
Surprisingly, however, studies of URM structures subjected to earthquakes
have at times shown better performance than expected. Certainly,
floor, roof and intersecting walls function as diaphragms, creating
a more stable structure, like a box or cube. Studying URM buildings
also provides clues as to how to best retrofit structures for improved
future performance.
Because of the reasons noted above, a larger number of contemporary
masonry structures will be designed and built as reinforced structures.
From a structural standpoint, taller, thinner walls are more efficient,
but have to be appropriately reinforced to resist seismic loadings
without damage. Reinforcement and good roof and floor connections
help withstand large forces developed during earthquakes.
The following articles and reports provide helpful information
about the past performance of masonry structures subjected to earthquakes,
seismic-related code and design issues, and ongoing research to
improve structural performance related to seismic activity.
Articles and Reports
|