W91278-17-R-0052_Stennis_Spillway_Gate_Inspection_Report.pdf

STRUCTURAL TRIP REPORT

1. SUBJECT: Stennis Spillway Gate #3 Impact Damage Assessment

2. LOCATION: Columbus, MS

3. PURPOSE: Impact Damage Assessment

4. DATE: 1 June 2016

5. ATTENDEES:

MOBILE DISTRICT ENGINEERING DIVISION

Allen Davis

OPERATIONS DIVISION

Allan Brewer

R&D

Joel Smith

6. NARRATIVE: This report covers the structural findings during the visual inspection performed on 1 June 2016 at Stennis Lock and dam.

7. STRUCTURAL OBSERVATIONS:

The spillway gate is approximately 60 wide and 27 feet tall weighing about 170,000 #’s.

The barge impact occurred about 12 feet to the east of the gate centerline. The upper portion of the gate was the most severely damaged, significant damage extended all the way to the bottom horizontal girder.

The upper portion of the gate had about a 20 foot wide section severely damaged, the damage included; skin plate buckling, vertical rib buckling, buckling of the top horizontal girder compression flange, crimpling of the girder web and stiffeners. The same elements had similar damage extending on down the gate where the width of damaged area was about 4 to 8 feet.

The strut arms and trunnion girders were inspected and no damage was observed. The skin plate and vertical ribs are bolted on. A floating plant crane and basket was used to perform the inspection, allowing good access to all gate components.

Non-impact damage observed deficiencies;

1. Replace bottom seal

2. Replace cathodic protection anodes

3. Repair old welds and remove weld spatter etc.

4. Clean and coat areas or corrosion

5. Break edges for proper coating adhesion

8. STRUCTURAL RECOMMENDATIONS:

Buckling and displacement of compression elements of the gate during the impact have significantly weakened the gate, estimated at 20 to 30% reduction in capacity. The gate is in need of repair due to its weakened condition. The two options are to repair in place or remove the gate and have a fabrication shop make the repairs. With the amount of gate deformation, it is likely when the trunnion pins are removed that the strut arms will show displacement.

The preferred option would be to have the repairs done in a shop;

1. Much better environmental control which would help in controlling overall dimensions during repair, better welding conditions, proper blast cleaning and coating application and curing.

2. More resources to perform the work and handle any problems that may be encountered.

3. Protection of personnel and equipment in performing the work, due to possible flood conditions, high heat, etc.

4. Gate removal and transport may be difficult or require more crane support.

The second option would be to repair in place.

1. A great deal of rigging and temporary supports would be needed to support the gate when portions are removed to maintain and re-establish proper alignment and overall dimensions.

2. The weather will affect the work and quality a great deal

3. There are inherently more dangers in this type of field work than in performing the work in an enclosed shop.

4. Transport for medical reasons is more difficult and time consuming

5. A combination of direct sun and shade would make maintaining accurate dimensions very difficult, which may result in significant problems in reconnecting trunnions and seals.

A sketch and brief scope of work for repair options is provided separately. Weld joint details, welding procedures, gate handling, dimensional tolerance, QA and QC procedures etc. will need to be developed.

Allen Davis

Structural Engineer

US Army Corps of Engineers

Mobile Disrict

Office: 251-694-3446