Higher
frequency modes and vertical component: Two uncounted causes for failure
of stone and adobe masonry?
Traditionally, the high frequency components of earthquake loading
are disregarded as a source of structural damage because of their small
energy content. This argument is correct only if we consider macroscopic
out-of-plane bending failures and in-plane shear failures, which indeed
require a large energy input from earthquakes. In common cases where the
wall is made up of two external masonry skins, or wythes, containing a
loose rubble infill, I argue that the higher frequency waves travelling
through stiff masonry structures can cause two types of failure mechanisms
that have not yet been taken into account. First, the high frequencies
can cause small vertical inter-stone vibrations that result in irreversible
relative displacements of the stones. A second failure mechanism, which
is also as yet unaccounted for, is associated with the outward thrust
from the compaction of the loose inner core of the wall. In masonry walls
the inner core is mostly made up of loose sand and gravel that has the
tendency to compact when experiencing high-frequency vibrations. The lateral
thrust caused by compaction of loose soils can be as high as the weight
of the compacted soil column, and this thrust will push the unstable masonry
units outward causing the collapse of the exterior masonry skins. This
failure mechanism will compound the effect of the inter-stone displacement
elicited by the high frequency motion components.
Building Technology & CEE
Sponsors
Tom
Kachoris Jr.
"Spaulding
Brick Co."
Howard Bourdelais
Modern Continental
ADOBE
(Click to see details)
Burlap
Reinforcement for Improved Toughness Of Low-Cost
Adobe Residential
Structures
Adobe
brick wall construction is commonly used for low-cost dwellings in developing
nations. This system, being extremely brittle, performs poorly during
earthquakes. The
use of burlap layers as a low-tech, low-cost solution to the problem of
brittle fracture in adobe brick- wall systems will be investigated.
Improvement in both strength and toughness will be shown by comparison
with a similar un-reinforced specimen.
The diagonal compression test will simulate the stresses induced
under earthquake conditions.
Download in PDF format
BHUNGA
(Click to see details)
Bhunga: Cylindrical Structure
Subassembly Test
"Bhungas"
are cylindrical mud huts
that have been traditionally built for thousands of years. Their particularity
is that they perform exceptionally well under seismic loads. Their performance
during the recent Gujarat (India) earthquake only confirmed that simple,
low-cost housing can be safe, even under extreme conditions.
Download in PDF format
Related
links:
http://www.vskgujarat.com/like_minded_organization/seva_bharti_bhunga.htm
General description of the Bhunga type of house
http://www.hindu.com/thehindu/2001/02/26/stories/0226000g.htm
Article in "The Hindu" newspaper: 'Bhunga':
Kutch's engineering wonder
http://www.makingindiagreen.org/ludiya.htm
"An Effort in Redevelopment with Community Participation". How
a community can get
involved in rebuilding a village destroyed by an earthquake
http://www.undpquakerehab.org/innovativetechno.htm
How to build a Bhunga with "Compressed Earth Blocks" (CEBs)
http://www.earth-auroville.com
Everything on how to make CEBs and build with them
http://www.ntnu.no/~rohit/Rohit%20Dr.ing%20final1.pdf
"Disaster Vulnerability Through Local Knowledge and Capacity"
This dissertation investigates the past and the present status of local
knowledge, skills and capacity of rural communities in India and Nepal
for reducing their vulnerability to earthquakes.
