 Recuperator
Design Assessment
A recuperator can increase the efficiency of a gas-turbine
propulsion engine by more than 20% through recovery
of the thermal energy from the engine exhaust. Exponent,
with its multidisciplinary expertise in mechanical
design, fracture mechanics, materials, joining,
and testing, assisted Northrop Grumman Marine Systems
(formerly Westinghouse-Marine) in refining its WR-21
ICR gas turbine ship propulsion system recuperator
design and construction for improved structural
reliability. |
 Stress
Analysis of Seismic-Resistant Structures
The Northridge, California earthquake on January
17, 1994 caused an estimated $15 billion damage
to homes, highways, and businesses in the greater
Los Angeles area. Although California leads the
world in seismic-resistant structural design, civil
engineering technology is tested and advanced with
each successive large earthquake. During the Northridge
earthquake, many welded steel special moment-resisting
frame (SMRF) connections in multistory buildings
fractured in a largely brittle manner, with little
obvious plastic deformation. The SMRF connection,
developed for use in seismically active areas, was
designed to absorb energy during an earthquake through
large-scale plastic deformations. Exponent assembled
a team of civil, mechanical, and metallurgical engineers
to determine the root cause of SMRF connection failures
discovered in a five-story medical office building
in Santa Monica. The analysis involved modeling
of structural response to ground motion and nonlinear
joint behavior under seismic loads, as well as detailed
metal-lurgical evaluation of fracture surfaces.
Exponent engineers identified a ductile crack initiation
mechanism resulting from certain design details,
a finding that is helping to improve SMRF design
reliability. |
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