198
CHAPTER 5. COASTAL STRUCTURE MODELS
Jensen (1984) stated that each testing step should last the
model equivalent of between 3 and 10 prototype hours (typical of storm duration), and Owen and Allsop (1983) suggested run lengths between 1000 and 5000 waves. Model
waves can either be run as a continuous time series or
in short bursts to minimize reflections. In general, tests
done with regular (monochromatic) waves are run in short
bursts because of wave reflections reaching the wave board
and being re-reflected, resulting in nonregular wave forms.
Tests with irregular waves usually are run for longer duration because the re-reflected waves are treated as part
of the incident wave spectrum. Duration of irregular wave
bursts varies between laboratories and facilities but 10 minutes is not uncommon.
2. Tests of Design Condition. This is a test conducted
using a single design condition. Jensen (1984) stated that
this type of test is used to examine some singular aspect of
the structure, such as a concrete block cap or the lee-side
slope, under conditions where the remainder of the slope
is known to be stable.
3. Tests Reproducing Individual Storms. If accurate
historical records exist or reliable wave hindcasts are available, the structure’s response to extreme events can be
examined. This is the method used for model verification when an attempt is made to reproduce known prototype damage. Lillevang, et al. (1984) simulated prototype
waves using short bursts (9 waves) of uniform waves separated by sufficient time to allow the test basin to settle out.
Waves were generated with a cnoidal shape to minimize
parasitic waves, and a novel method of wave board control
was used to stop generation of abnormally large waves at
the end of the train. Lillevang, et al. also conducted simulations using irregular waves fitting the prototype deep
water measured spectrum.
4. Long Duration Tests. The purpose of long-duration
tests is to determine if initial damage to a structure continues until total destruction, or if the structure stabilizes
in a partially damaged condition. These tests represent
the impacts of long-duration storms, such as nor’easters
on the east coast of the United States.
CHAPTER 5. COASTAL STRUCTURE MODELS
Jensen (1984) stated that each testing step should last the
model equivalent of between 3 and 10 prototype hours (typical of storm duration), and Owen and Allsop (1983) suggested run lengths between 1000 and 5000 waves. Model
waves can either be run as a continuous time series or
in short bursts to minimize reflections. In general, tests
done with regular (monochromatic) waves are run in short
bursts because of wave reflections reaching the wave board
and being re-reflected, resulting in nonregular wave forms.
Tests with irregular waves usually are run for longer duration because the re-reflected waves are treated as part
of the incident wave spectrum. Duration of irregular wave
bursts varies between laboratories and facilities but 10 minutes is not uncommon.
2. Tests of Design Condition. This is a test conducted
using a single design condition. Jensen (1984) stated that
this type of test is used to examine some singular aspect of
the structure, such as a concrete block cap or the lee-side
slope, under conditions where the remainder of the slope
is known to be stable.
3. Tests Reproducing Individual Storms. If accurate
historical records exist or reliable wave hindcasts are available, the structure’s response to extreme events can be
examined. This is the method used for model verification when an attempt is made to reproduce known prototype damage. Lillevang, et al. (1984) simulated prototype
waves using short bursts (9 waves) of uniform waves separated by sufficient time to allow the test basin to settle out.
Waves were generated with a cnoidal shape to minimize
parasitic waves, and a novel method of wave board control
was used to stop generation of abnormally large waves at
the end of the train. Lillevang, et al. also conducted simulations using irregular waves fitting the prototype deep
water measured spectrum.
4. Long Duration Tests. The purpose of long-duration
tests is to determine if initial damage to a structure continues until total destruction, or if the structure stabilizes
in a partially damaged condition. These tests represent
the impacts of long-duration storms, such as nor’easters
on the east coast of the United States.