(b) For preliminary analyses, Table B-4

shows typical values for impact angles for

approach conditions to navigation lock walls.

Accurate determination of impact angles for

final design should be made using one of the

Usual

5 - 10

methods presented above.

Unusual

10 - 20

Extreme

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.

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.

impact:

(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.

B-13