30 Sep 04
(b) For preliminary analyses, Table B-4
shows typical values for impact angles for
Typical Ranges for Impact Angles Used in
approach conditions to navigation lock walls.
Accurate determination of impact angles for
Approach Angle, deg
final design should be made using one of the
5 - 10
methods presented above.
10 - 20
20 - 35
(c) The distributions for impact angle and
velocity can be based on data from either geometric constraint, scale model testing, or time-lapse video.
From the results of previous PBIA, the distribution for velocities and angles are lognormally distributed.
This is a reasonable observation since most of the angles and velocities that occur in the field are
generally skewed to the left of the average value. These distributions may be truncated depending upon
certain physical limitations that exist at a navigation site.
(d) The trend from previous PBIA, as shown in Appendix C, indicates that the average range for the
mean normal impact velocity falls within the 0.3- to 0.5-m/sec (0.75- to 1.5-ft/sec) range and average
angles tend to be around 4 to 8 degrees. This will, however, vary greatly depending upon the site-specific
conditions that are being analyzed in the PBIA. Another item to include in the PBIA is the correlation
between the mass, velocity, and angle. From previous PBIA, a direct correlation between mass, velocity
and angle has been observed. For example, a large barge train (15 barges) will generally approach a lock
wall with a slower velocity than a smaller barge train (2 barges). These correlations should be investi-
gated and accounted for in any PBIA.
B-5. Barge Impact Analysis for Rigid Walls
a. Barge impact is an important load case in defining the wall dimensions in either preliminary or
advanced designs. The method presented in this ETL is based on the direct results from the full-scale
experiments as discussed in Appendix F. The empirical equation developed to estimate the impact load
normal to the structure is implemented as part of this ETL for rigid walls.
b. There are other considerations that can also be factored into the design of rigid walls for barge
(1) For preliminary designs of lower approach walls, the loads can be presumed to be one-half those
loads for the upper approach walls. During advanced design phases, additional scale modeling or time-
lapse video should be utilized to confirm that this presumption is correct.
(2) Since most barge impact analyses focus on the loads for the approach walls, a presumed value of
445-667 kN (100-150 kips) may be applied as the minimum impact forces for preliminary design on
chamber walls. Additional hydraulic modeling should be considered for small barge trains impacting
chamber walls at greater angles.
(3) The forces from head-on impacts into bull noses, protection cells, and lock walls are a difficult
problem to solve. This is due primarily to the complexity of the interactions between the breaking of the
lashings and the crushing of the rake of the barge during the impact. This interaction can be modeled
using either empirical equations from mechanical models or complex finite element modeling of the barge
system. Based on current research efforts, other design methods that are available, and the use of expert
judgment within the USACE, a value of 8,896 kN (2,000 kips) is recommended to be used for the pre-
liminary design of rigid walls subjected to head-on collisions. For final design values for head-on
impacts, consultation with CE-CW is recommended until additional research is conducted on this issue
and additional guidance will be provided.