ensure that the tasks involved in creating a
FEM don't outweigh its benefits. The
inspection of the drydock during which
plates and members throughout the struc-
ture are gauged must be thorough yet lim-
ited, since such a process can easily
become all-consuming. The key to the
gauging inspection is to define an appro-
priate and rational measurement matrix
prior to the inspection. The plan will focus
the survey effort on the areas of the struc-
ture that are most critical, rather than tak-
ing a blanket or random testing approach.
The ultrasonic testing matrix for a dry-
dock would specify gauging at more fre-
quent intervals of members primarily con-
tributing to the primary strength and
members that are directly in the path of
the docking loads. Typically this would
include bottom shell and deck plate, gird-
ers, web frames, bulkheads, and stan-
chions near the centerline. Areas of less
importance to the global strength of a
dock will be gauged at fewer locations.
These areas may include stiffeners, frame
flanges, trusses off centerline, and
sideshell, depending on the drydock
design. The sheer volume of data collect-
ed and input into the modeling program
must be identified and managed before
the structural evaluation begins. Comput-
er memory requirements are proportional
to the database size, which in turn is
dependent on the number of elements and
the size of the element properties library.
Additionally, file save, display regenera-
tion, and solution times grow exponential-
ly with increases in database size, so it is
preferable to keep the database size to a
minimum without compromising the
accuracy of the results.
Future Uses
Creation of a finite element model to
address corrosion in drydocks is useful
not only for immediate repair needs, but
also for addressing future maintenance
issues and corrosion control criteria. The
repair matrix provides the owner's mainte-
nance group with an invaluable record for
future reference. The maintenance group
can refer to the repair matrix before carry-
ing future thickness gauging measure-
ments to determine which areas require
more attention. After future thickness
gauging measurements are carried out, it
is relatively easy to incorporate the results
into the existing FEM and determine if
further repairs are necessary.
At EBDG we have found that when
properly executed, emerging FEA tech-
nology can be used to manage the mainte-
nance of the drydock to optimize repair
effort and minimize costs.
26 • MarineNews • August, 2005
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SNAME Introduces
Innovation Sessions
In response to feedback from exhibitors, SNAME will introduce Innovation Ses-
sions during the SMTC&E and SPS, scheduled to be held in Houston on October
20-21, 2005. Exhibitors who have new products or technologies can use these ses-
sions to make presentations to SMTC&E and SPS conference attendees in a special
lecture-style area of the Expo Hall with seating for up to 30.
Details:
20-minute segments, with 10 minutes for Q&A, for a total of 30 minutes
maximum per session.
Time slots available are:
Thursday, October 20 - 12:30 pm - 2:00 pm and 4:00 pm - 4:30 pm
Friday, October 21 - 8:30 am - 9:30 am and 12:30 pm - 3:30 pm
Although these presentations will not be formally reviewed, SNAME must
reserve the right to refuse any that do not seem appropriate, and will rely on the
exhibitor's and presenter's own standards of professional behavior to make close
supervision unnecessary.
Brief abstracts must be submitted to SNAME HQ to enowak@sname.org.
As there are only twelve slots available, they will be on a first come, first
served basis. You will receive a confirmation after your abstract has been received.
Two additional presentations will be selected as standbys.
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