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What is a
Seismic Vulnerability Assessment?
A Seismic
Vulnerability Assessment is a comprehensive Engineering Study to evaluate susceptibility of
structural systems to potential damage from seismic shaking based on the Performance
Objectives established by the Client, and using methods, which generally follow guidelines
presented in FEMA 356 Seismic Rehabilitation of Buildings. The extent of the investigation is
based on the size and value of the Building.
Results: The
Seismic Vulnerability Assessment will give you the information you need to decide whether it is
cost effective to make a seismic retrofit or demolish and construct a new building.
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What kind of
damage or existing conditions would indicate vulnerability to seismic shaking?
In buildings using
tilt-up concrete or masonry Tall-walls which were constructed before circa 1973 there are known
deficiencies in the structural connections that resulted in the collapse or severe damage to the
structure.
These deficiencies
were identified following the aftermath of the 1971 San Fernando, California, Earthquake.
Thereafter, Building Code provisions were strengthened with respect to these connections.
The following pictures
show examples of existing deficient connections and typical repairs we can design to
strengthen those connections and improve the Performance Level of the structure to meet your
renovation objectives (see diagram below).
Source: "Earthquakes,
Volcanoes, & Tsunamis; An Anatomy of Hazards," by Karl V. Steinbrugge, published by Scandia
America Group, 1982.
Example #1:
The absence of adequate continuity tie connection at Main Cross-Tie members in the roof
diaphragm.
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Typical
connection made in older buildings before 1973.
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Typical
Repairs connection required by the current Building Code.
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Example #2:
The absence of adequate anchorage connection between roof framing members and the tilt-up
or masonry Tall-walls.
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Typical
connection made in older building before 1973 used a bolted ledger without
anchorage which can fail in cross-grain bending.
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Typical
Repair connection required by the current Building Code.
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How will the SVA
be conducted?
Evaluation of the
structure condition will be based on investigations at the site and will generally follow the
Operations Plan for a SCA except that the Assessment will likely also entail the following based
on Client's Scope and Budget:
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Comprehensive inspections
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Field locate reinforcement in masonry or reinforced concrete walls using subsurface exploration
with G.P.R., Ground Penetrating Radar
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Testing of material samples, i.e. steel coupons
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Field Measurement, document search, and
analysis to develop As-built drawings
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Computer model in SAP 2000
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