RTA Submission - DA APP B - Structural Observations of Mooring Pier.pdf

TROY LOCK AND DAM MOORING PIER

IN‐DEPTH STRUCTURAL INSPECTION REPORT

TROY, NY

USACE North Atlantic Division New York District

Engineering Division Design Branch

January, 2023

Troy Lock and Dam

Mooring Pier i

Table of Contents

Section 1. Introduction

Section 2. Purpose of the Site Visit

Section 3. History of Mooring Pier

Section 4. Observations

4.1. Steel Sheet Pile Cells

4.2. Fender Systems and Connections

4.3. Top of Pier Concrete Slab

4.4. Evaluation of Miscellaneous Pier Elements (Ladders, Grating, Channel Supports, etc.)

Section 5. Conclusion and Recommendations

5.1. Conclusion

5.2. Recommendations

Section 6. Appendices

Appendix A: Structural Inspection Notes, Photo Log, and Photos

Riverside of Mooring Pier Cell Structure

Appendix B: Structural Inspection Notes, Photo Log, and Photos

Landside of Mooring Pier Cell Structure

Appendix C: Structural Inspection Notes, Photo Log, and Photos

Top of Mooring Pier Cell Structure

Section 1. Introduction

A USACE team from New York District Engineering Division traveled to Troy, NY on November 8‐ 10th, 2022 to complete an in‐depth inspection of the Downstream Mooring Pier. This inspection is a follow‐up to the site visit by USACE in September 2022, which initially identified potential structural issues in several elements of the mooring pier. The mission of this in‐depth inspection was to confirm or re‐define conclusions and recommendations from the findings of the previous site visit held. The inspection team consisted of Christopher Hagerman, E.I.T., Daniel Kim, P.E., and Michael X. Chen, P.E., Structural Team Leader. They coordinated with Kristin Irwin, AIA, and the Albany Field Office Operations Team.

Section 2. Purpose of the Site Visit

The main purpose of this specific visit in Wednesday afternoon was to observe the mooring pier located downstream of Troy Lock on the Hudson River (shown in Fig. 1 and Fig. 2) and evaluate the pier’s existing structural conditions. This evaluation would provide guidance on what repairs need to be done to the pier for continued service. The mooring pier is currently used by public and private ships when preparing to enter and exit the lock and, therefore, serves an important function in the infrastructure. The quantities of structural mooring pier cell components that were inspected are tabulated in Table 1 in the next page.

Figure 1: North end of Mooring Pier Figure 2: South end of Mooring Pier

(looking downstream) (looking upstream) (Photo 1 in Appendix A) (Photo 2 in Appendix A)

Structural Component Quantity

Cell Steel Sheet‐Pile Walls 17

Top of Cell Concrete Deck 17

Steel Rubbing Strips 14

Timber Rubbing Strips 224

Bracing Straps 32

Steel Post 16

Steel Post Web Stiffeners (Above Low Water Elevation)

Steel Grating 16

Steel Angle (Connecting to Timber Strips) 672

Steel Angle (Connecting to Steel Strips) 112

Steel Channel (Connecting to Steel Post) 64

Steel Channel (Supporting Steel Grating) 32

Steel Ladder 8

Snubbing Post 9

Steel Bumper 9

Table 1: Quantities of Structural & Non‐Structural Components Inspected

Section 3. History of Mooring Pier

Prior to the construction of the existing mooring pier, the previous mooring piers consisted of 6 separate precast‐concrete piers supported on a timber frame with timber rubbing strips and a rubble core. In 1968, the concrete piers were removed and replaced with a diaphragm type cellular structure. It consists of seventeen steel sheet pile cells filled with crushed stone and covered by 12”‐ 24” concrete deck at top. The steel sheet pile (Size S‐32) nominal thickness is ½ inch. The mooring pier has a timber fender system consisting of seven rows of 10”x10” oak rubbing strips that are fastened along the riverside length of the pier. The mooring pier also has 7 rows of steel channel rubbing strips that are attached at the ends of the pier. There are nine cast iron snubbing posts and eight ladders for accessibility to the top of the structure. This mooring pier has been in service since it was constructed, but the poor conditions of the fender system indicates that the pier was not well‐maintained.

Figure 3: Mooring Pier Elevation View

Figure 4: Mooring Pier Plan View with Cell Numbers

Figure 5: Fender and Ladder Connection Detail Figure 6: Fender Section View

2 3 4 5 6 7 8 1 9 10 11 12 13 14 15 16 17

Section 4. Observations

Section 4.1. Steel Sheet Pile Cells

The USACE team noticed the sheet pile cells are in fair condition. On a majority of the sheet piling, there are signs of peeling paint and light rusting. However, in the areas where the rubbing strip support angles are welded to the sheet piling, there is significant rusting. See Figure 7.

To measure the steel thickness, the inspection team first grinded off paint and sediment in several locations along the pier (for locations, see Appendices C & D), and then they used an ultrasonic thickness gauge on the cleaned spot. The readings showed that section loss was limited to 10% on average at most locations. However, in the locations listed below, the average thickness was measured to be less than 90% of the design thickness of ½”.

Cell 10, Riverside, halfway above the bottom fender at the 5th sheet pile section upstream of the ladder. The average steel thickness was measured at 0.433 inches.

Cell 1, Landside, Approximately 86” from top of sheet pile, in the first sheet pile from the downstream riveted plate connection. The average steel thickness was measured at 0.427 inches.

Cell 3, Landside, Approximately 104” from top of sheet pile, in the 3rd sheet pile from the upstream riveted plate connection. The measured steel thickness was 0.444 inches.

Cell 14, Landside, Approximately 90” from top of sheet pile, in the 3rd sheet pile from the downstream riveted plate connection. The average measured steel thickness was 0.448

Cell 14, Landside, Approximately 134” from top of sheet pile, in the 5th sheet pile from the downstream riveted plate connection. The average measured steel thickness was 0.442

Cell 17, Landside, Approximately 79” from top of the sheet pile, in the 8th sheet pile from the upstream riveted plate connection. The average measured steel thickness was 0.396 inches.

This indicates that the sheet piling section loss can go as high as 20%. Most of these occurred near the high‐water elevation or above in the splash zone. As a result, the USACE team will analyze the loads of the sheet piling to see if the hydraulic structure can still withstand design loads with this level of section loss.

Furthermore, the downstream cell (#17) shows leaking at several points on the riverside of the structure. The steel seems to have cracked and exhibited excess section loss in these regions and will need to be repaired. See Figures 8 & 9.

Figure 7: Front View of Cell‐Wall Looking Upstream showing Rusting of Sheet Piles and Deteriorated

Fender System (Photo 3 in Appendix A)

Figure 8: Leaking Present at Joint Figure 9: Leaking Present at Joint between Plates in Cell 17 between Plates in Cell 17 (Photo 8 in Appendix A) (Photo 9 in Appendix A)

Section 4.2. Fender Systems and Connections

The fender system and its supports have shown significant deterioration as listed below:

180 of 224 the timber rubbing strips are missing, damaged, or decaying. At the locations of the deteriorated timber rubbing strips, a majority of the bolts connecting the rubbing strips to the support angles are either missing entirely, missing a nut, or bent. And all 32 bracing straps for the timber rubbing strips are either irreparably damaged or missing.

All 14 of the steel rubbing strips show minimal rusting (See Figure 17).

All 112 of the support angles and the welded connections are showing rusting. In the areas surrounding the welds of the angles, the sheet piling is showing significant rust and paint peeling. The welded connections of most of the angles show rusting. 3 angles showed poor welds or welds with cracking (See Figure 18).

8 of the 112 steel rubbing strip support angles have a set of unused bolt holes which gather debris and water, making the angle connections susceptible to excessive deterioration (See Figure 16).

338 of the 672 timber rubbing strip support angles have either had existing bolt holes expanded or had a third set of bolt holes installed in the field through plasma cutting methods or an equivalent method (See Figure 11). 30 of these angles have additional plates attached to the ends with butt welds to install these extra set of holes (See Figure 12). This has seemingly been done to accommodate the geometry of the rubbing strips after the angles have been welded to the sheet piling and the posts. All bolt holes show significant rusting. The bolt holes of two angles exhibit significant corrosion. As a result of these deficiencies, the USACE structural team will analyze the strength of these angle connections with reduced bolt spacing and increased bolt holes to see if it can resist the design loads.

Of the remaining timber rubbing strip support angles, the existing holes of 88 angles show significant rusting.

31 of timber rubbing strip support angles have been significantly bent (See Figure 10).

All 16 steel posts are showing rusting. The steel posts in two locations show signs of local buckling of the flanges. The steel post in one location shows about a 15% section loss in the flange (See Figure 13).

There are 8 out of 320 steel stiffeners observed with corroded welds (See Figure 14). The steel stiffeners below the low water elevation were not visible, and were not inspected.

In the steel post between Pier Cells #10 & #11, there is a hole in the landside flange (See Figure 15).

Figure 10: Bent Angle with Damaged Bolts (Photo 16 in Appendix A)

Figure 11: Angle with Third Set of Bolt Holes Installed in Field with Plasma Cutting. Rusting present around bolt holes (Photo 19 in Appendix A)

Figure 12: Plate welded to End of Angle (Photo 23 in Appendix A)

Figure 13: Flange of Steel Post with about 15% Section Loss (Photo 24 in Appendix A)

Figure 14: Corroded Stiffener Welded Connection (at Post Between Pier Cells #7 & #8)

(Photo 27 in Appendix A)

Figure 15: Hole found in Leftside Flange of Post Between Pier Cells #10 & #11

(Photo 28 in Appendix A)

Figure 16: Welded Angle Connection with Unused Bolt Holes (Photo 30 in Appendix A)

Figure 17: Steel‐Channel Rubbing Strips (Photo 31 in Appendix A)

Figure 18: Poor Weld on Angle Connection (Photo 32 in Appendix A)

Section 4.3. Top of Pier Concrete Slab

While on the mooring pier, the team noticed differential settlement (up‐to 9 ½”) in the concrete slabs across the top of the cells. The settlement in the slabs have caused cracking and spalled concrete, especially near the sheet pile borders between adjacent cells. The total cracking and spalling were approximately 70 SF. The cells with ladders also exhibited a crack that ran east‐west from the ladder landing to the land side of the slab (See Figures 19‐24).

Vegetation is growing through the interface between the concrete deck and the sheet piling where adjacent cells meet (See Figure 19). In most of the cells, there are large patches of vegetation and soil that have grown through spalled and cracked concrete (See Figure 21). There are also tree branches extending from the riverside over the pier at the joint between cells 13 & 14 and at the joint between cells 10 & 11. In 2 ladder landings at cells 12 & 16, there is significant vegetation and tree growth blocking the path to and from the ladder. The excess vegetation and tree branches are a safety hazard when moving along the top of the pier.

Figure 19: Vegetation at Border of Cells (Photo 39 in Appendix A)

Figure 20: Maximum Settlement of 9.50” of a Concrete Deck on near the ladder Pier Cell #2 (Photo

40 in Appendix A)

Figure 21: Spalled Concrete with Exposed Rebar (Photo 41 in Appendix A)

Figure 22: Spalled and Delaminated Concrete (Photo 42 in Appendix A)

Figure 23: Crack Running East‐West Typical All Concrete Decks in Ladder Cells

(Photo 43 in Appendix A)

Figure 24: Scaling Concrete (Photo 44 in Appendix A)

Section 4.4. Evaluation of Miscellaneous Pier Elements (Ladders, Grating, Channel Supports, etc.)

All the ladders were bent either due to impact loading from passing ships, debris, or ice. The ladder plates at cells 2 & 4 are no longer connected to the concrete deck at the top of the cell. For all other ladders, the excessive deformation has caused the ladders to rotate significantly at the connections (See Figures 29‐32).

The grating on the southern side of cell 8 has been significantly bent, leading to significant warping of the support channel on the southern end of the grate. The top flange welded connection of warped southern‐end support channel to the sheet pile has also corroded significantly for the full length of the connection. The top flange welded connection of both intermediary channels to the steel post is also significantly corroded. This corrosion as likely made worse as a result of the warped grating (See Figure 26).

The grating on the southern end of cell 4 is slightly warped. The bottom‐flange connection of the southern‐intermediary channel to the steel post is also missing (See Figure 28).

The river side of the grating south of cell 11 is warped downwards. The northern‐end support channel shows significant corrosion full‐section and appears to have been relocated and reconnected to the sheet pile at some point due to a channel‐shaped rusted area adjacent to the channel. The bottom flange welded connection of the southern‐intermediary channel to the post has corroded with section loss in the bottom flange. The bottom flange welded connection of the southern‐end channel to the sheet piling shows corrosion for ¼” of length (See Figure 27).

In addition to damage to the support channels caused by the grating deformation, several other welded connections between the channel and the structural elements have corroded significantly, requiring repairs or a full channel replacement (See Figure 27). In 9 locations, there was no web weld on one or both sides of the channel web connection to the posts and the sheet piling (See Figure 25).

The snubbing posts exhibited peeling paint and minimal rusting at the base (See Figure 33). Two of the bumper pipes in front of the snubbing posts show significant deformation. All of the bumper pipes also show significant rusting. There are also rusted and deteriorated brackets present in some cells (See Figure 34).

Figure 25: Web Weld Missing (Photo 45 in Appendix A)

Figure 26: Cracked Top Flange Weld (Photo 46 in Appendix A)

Figure 27: Corrosion in Section and Corrosion in Weld (Photo 47 in Appendix A)

Figure 28: Bottom Flange Welded Connection Meeting (Photo 48 in Appendix A)

Figure 29: Warped Channel and Grating (Photo 34 in Appendix A)

Figure 30: Ladder Rung and Plates Bent (Photo 35 in Appendix A)

Figure 31: Bent Ladder Handle Plates Detached from Concrete (Photo 49 in Appendix A)

Figure 32: Deformed Ladder Top Plates (Photo 36 in Appendix A)

Figure 33: Typical Snubbing Post with paint peeling and rusting (Photo 50 in Appendix A)

Figure 34: Corroded Bracket Connected to Concrete Slab (Photo 51 in Appendix A)

Section 5. Conclusion and Recommendations:

Section 5.1. Conclusion

The observations and measurements collected during the in‐depth inspection provided more information to the team to finalize the preliminary conclusions made in the September, 2022 Site Visit Memorandum Report. The team confirmed that the current mooring pier cellular structures are in a stable condition that will not require replacement at this time. The previously discussed upgrades to consider were also reevaluated and have been updated below:

i) The majority of the timber rubbing fenders have failed, gone missing, or are in an advanced stage of decay.

ii) The majority of the supports and tie plates of the timber fender system are either damaged, corroded, or at higher risk to failure due to field alterations. Due to field alterations, the bolt hole spacing has been significantly reduced, reducing the structural capacity of these supports against design impact loads.

iii) Eight of the seventeen concrete slabs at the top of the cells have differential settlement, specifically at the slabs without the snubbing posts. It could be a product of construction or possibly long‐term consolidation of the crushed stone backfill under the deck. However, it is not an issue to the stability of the cell‐structure, but the settled deck and excess vegetation may cause maintenance issues in the future as well as exposing workers to hazards.

iv) Miscellaneous Damages: There are four damaged/deflected ladders; three twisted metal gratings between cell walls, grating supports are damaged or corroded, some steel support posts show signs of buckling and section loss, and at least six minor leaks observed along the cell walls.

Section 5.2. Recommendations

The following recommendations are listed by priority of structural concern:

The timber rubbing fenders should be 100% replaced with a longer‐lasting composite material.

While the majority of the fender system connections (support angle plates, ties) are damaged, not all may need to be replaced. The strength of the angles in their existing condition will need to be further analyzed in the retrofit design phase to determine which angles require a full replacement. All bolts and nuts will need replacement.

All posts should be inspected for signs of section loss and buckling when the area is dewatered for repainting. The posts should be repaired according to the deficiency found in the field.

The damaged ladders and grating should be restored, and the ladders should be reattached to the concrete slab after the settlement is repaired. Any channel supports for the grating will need to be re‐welded or replaced depending on the condition found in the field.

Vegetation should be cleared from the top of the cells and the concrete decks should be leveled with light weight concrete or asphalt to improve the safety at the top of the pier. The gaps between the sheet piling and the concrete decks should also be resealed so that vegetation will not continue to grow in the future.

Remove the corrosion and repaint the surface of the sheet pile cells. Because signs of paint peeling and rust were found at all heights along the pier, the area shall be dewatered so that the entire cell structure shall be cleaned and repainted. Repair the joints where leaking occurs in the downstream cell.

Clean and Repaint the Bumper Pipe and Snubbing Posts. Fix bent bumper pipes wherever they are found.

The report was prepared by Daniel Kim & Christopher Hagerman, and reviewed by Michael X. Chen, Structural Team Leader.

Section 6. Appendices:

Appendix A: Structural Inspection Notes, Photo Log, and Photos Riverside of Mooring Pier Cell Structure

Appendix B: Structural Inspection Notes, Photo Log, and Photos Landside of Mooring Pier Cell Structure

Appendix C: Structural Inspection Notes, Photo Log, and Photos Top of Mooring Pier Cell Structure