Country and hazard overview
CASE STUDY
Rapid visual assessment for
retrofitting
Country: El Salvador
Organisation: UNESCO, University of El
Salvador, University of Udine, Italy
Hazards: Earthquakes
Keywords: VISUS, rapid visual assessment,
information communication technology,
government, retrofit, triage, training
Summary: Before school retrofitting or
SECTION III: PLANNING
reconstruction programs can begin, weak
buildings need to be identified and prioritised,
and retrofit or replacement designs calculated.
Rapid visual assessment is typically the first
step in this process. In El Salvador, UNESCO
and two universities piloted a tablet-based rapid
visual assessment tool. The project assessed
100 school buildings in 10 days and built the
capacity of government officials, profe ssionals
and engineering and architecture students along
the way. For many, the pilot was their introduction
to building assessments and the fundamental
principles of seismic-resistant design.
GUATEMALA
Ahuachapan
Santa Ana
Sonsonate
HONDURAS
Chalatenango
San Salvador
Nueva San Salvador
Sensuntepeque
EL SALVADOR
San Miguel
Usulutan
PACIFIC OCEAN
59
El Salvador is both populous and seismically active. In 2001,
two earthquakes struck, causing landslides and damaging
1,700 schools – more than one in three in the country. Ten
years later, many school buildings remain in disrepair, in
sites that leave them vulnerable to earthquakes and other
natural hazards, or they do not comply with seismic building
codes.
School buildings in El Salvador are mostly one story of
confined or reinforced masonry. Although some buildings
were traditionally constructed from adobe (mud brick), it has
not been used for schools after many children and a teacher
died during an earthquake in 2001.
When existing school facilities have not been built
to withstand hazards, they need to be identified and
strengthened. In contexts like El Salvador, where resources
are insufficient for a full detailed assessment of every school,
a rapid visual assessment can quickly collect proxy data
from a brief site visit. From these assessments, the MoE
can develop school retrofitting programs based on a triage
action plan that prioritises the weakest buildings and those
with the most students first. Detailed assessments can then
determine whether school facilities should be retrofitted or
replaced.
Using rapid visual assessment
Rapid visual assessment approaches have been
developed in many countries. These assessments do
not empirically determine the structural integrity of a
building. Instead they rely on proxy data to determine
fragility.
Originally, the proxy data was collected by engineers
after earthquakes or other hazards. Noting the intensity
of the hazard, they recorded the damage to buildings
and organised the results by the building typology and
other defining characteristics. Over time, enough data
was collected to be able to predict damage based on
a visual assessment of a building’s characteristics and
the expected strength of the hazard.
Rapid visual assessment only provides a general
prediction of damage. After the rapid visual
assessment is conducted, engineers still need to
perform in-depth assessments to develop appropriate
retrofit designs, but only for those identified during the
rapid assessment for an in-depth analysis. This strategy
reduces the cost of doing in-depth assessments for
every school.