Mission Bridge Reconstruction

Transcription

1 Mission Bridge Reconstruction R. Larry McKee, P.E. Canadian Pacific Railway 2755 Lougheed Hwy Suite 760 Port Coquitlam, BC V3B 5Y9 Canada (604) James Klett Canadian Pacific Railway th Avenue, SW Suite 600 Calgary, AB T2P 4Z4 Canada (403)

2 At approximately 0055k, 99/06/02 Mi-0.8 Mission Sub. Canadian Pacific s Coal Route, a swing span, part of a major bridge crossing the Fraser River was contacted, in the open position, by a large 4000T Chip Barge which was being towed by a local tug boat company. Wooden guide pier, during contact, allowed barge to be positioned under the upstream end of swing span resulting in 232, 363T span to be lifted off bearings and moving 12 down stream coming in contact with and lodging into downstream portion of guide pier. Swing span was in precarious position and required immediate securement by means of turnbuckles. Once secured operations commenced for rehabilitation and expeditious return to full service. As a consequence from the collision river traffic was prohibited through the area of construction. This caused great concerns from the Coast Guard and also from various local companies relying on the use of river navigation. In addition the river was rapidly rising due to run-off conditions. This imposed great forces on the damaged guide pier that presented a danger to construction personnel. By June 30 th, the swing span was in it s original position and operational. Work procedures, other challenges will be dealt with during the presentation

3 Vancouver is located on the west coast of British Columbia and is the western terminal of CP Rail System. (Figure 2) Approximately 80 million tons of freight per year is carried on our main line into Vancouver. The Mission bridge is located 40 miles east of Vancouver and carries coal and intermodal traffic over the Fraser River and down (Figure 3) to the deepwater port at Roberts Bank. (Figure 4) The bridge built in 1912, is 1563 long, single track, with a 10 mph speed limit. It is composed of 8 TT, 3 TPG s and TT swing span. In 1999, the bridge carried 33 million tons, but this year as a result in a change of operations with Canadian National, it will carry 56 million tons. (Figure 5) At 0055 on the morning of June 2 nd 1999, a loaded wood chip barge, weighing 4000 tons struck the swing span on the upstream end, while the span was in the open position. The swing span with rails and ties, weighed 363 tons. At the time of the collision the Fraser River water level was high and approaching a flood condition, the river was flowing at 10 mph. The author got out to the bridge at As with any situation involving a line outage, assessing the damage and determining the cause of the incident is the first priority. More so in this situation, as it was likely that this collision would result in an insurance claim and possible court action. In this case, the cause was simple, because the bridge tender was on the swing span at the time of collision and observed the entire incident. He was unhurt. (Figure 6) In normal operation, the barge is towed upstream from the mill, approximately.5 mile, lined up with the bridge and towed straight downstream and through the south channel. (Figure 7) However, this time the tugboat operator, came out at an angle directly at the swing

4 span, and behaved as if he never had control of the barge. The tug went down the south channel, but the barge hit the wooden protection pier on the upstream side and then the end of the swing span, pushing the span back 12, and sideways 10 (Figure 8). (Figure 9) The span was then canted over approximately 15 degrees, from the horizontal. Incidentally, while the bridge tender was unharmed, at the time he realized that the barge would hit the span, he ran back from the upstream end to the middle of the span. He was wearing his lifejacket, and considered jumping into the water, but the south channel was occupied by the tugboat and barge, and he was worried the bridge would fall into the North Channel, so he simply lay down on the deck until everything stopped moving. He was offered and did accept stress counseling. (Figure 10) This is not a picture an engineer likes to see, but insurance agents and our lawyers do like it. When asked the question, how do you know it was a loaded chip barge that hit the bridge, I just point to the wood chips. (Figures 11 & 12) These are two views of the downstream protection pier showing the span end resting on the edge of the pier. If the span had been pushed sideways another 4, then, it would have missed the protection pier and toppled into the North Channel. (Figure 12), shows the span was shifted backwards 12 off the ring area and roller bearings on the center pedestal. (Figure 14) Shows the timber protection pier on the upstream end, deflected into the North Channel. In Canada, as in the US, the regulatory agency for ship traffic and moveable bridges on waterways is the Coast Guard. While the authors concern was restoring the bridge for rail traffic, the various users of the waterway were pressuring the Coast Guard to force the railway to open the channels immediately for ship traffic. A number of boat operators and the Coast Guard came out

5 to the bridge on the morning of June 2 nd and commenced a dialogue that would continue until the span was back in operation. However, The author took the position that everyone s needs would be best met by ensuring that the swing span was back in operation as soon as possible. This meant we would be working 24 hours a day, seven days a week. (Figure 15) Shows damaged upstream end post on the swing span and bent floor beam. (Figures 16, 17, & 18) Shows damaged components on upstream and down stream ends of the swing span. Includes end floor beam assembly, lift drive and limit switch assemblies, wedge drive assembly. (Figure 19) From CP Rail s point of view, it was essential to get the swing span back in operation as soon as possible. Accordingly, Larry McKee contacted John Unsworth, System Manager of Structures, at 0400 and asked him Jim to come out to the bridge and help in the damage assessment development of repair work. By 0800, I had contacted two experienced contractors, on e specializing in river work, with tugs, barges, pile driving capability etc. and one who specialized in steel fabrication and installation. By all were on site and we made an initial assessment of the problem and commenced to develop solutions. As well, from CP Rail s point of view, we had to provide an estimate of time back in service 8 weeks and cost to repair $1.5 million plus. Our transportation people then looked at what traffic would be detoured on other railways.

6 (Figures 20/21) We determined that our first priority was to stabilize the structure, and prevent it from toppling into the river, while our second priority was to assess the damage and commence to fabricate the components from the original design. We attached cables from the ring gear to the span to give us some comfort in preventing the span from falling over and then drove support piling adjacent to the span (Figure 22). (Figures 23-27) These slides show the damage to the wheel rollers, wheel band assemblies, drum support beams, etc. (Figure 28 - Lifting and leveling structure) This shows the position of swing span following impact and our Plan A. Plan A was the usual napkin in the Coffee shop creation. 1. To drive piling to secure the swing span and 2. to use the piling as false work to move the span into place. If you ll recall the damaged end post displayed earlier, in addition to this damage the bottom chord of the truss was damaged for about 20. This would have been the area where we would be lifting the bridge. This would necessitate doing the repairs to this section before moving could commence. Time restraints did not allow this luxury and Plan A was aborted. For your information, approximately nine feet of the end post was removed, and sections were installed with full section slices. The complete bottom chord was replaced from end post to hanger. Plan B involved lifting the span at its center point.

7 (Figure 29) shows a pile vibrator. Back in the 1950 s this same Fraser River was running wild. Consequently, it resulted in a fixed 150 Truss Span, immediately south of the swing span, ending up in the river. To prevent any future recurrence the river bottom under the entire length of the bridge, 1563 was covered with concrete slabs, one and a half feet thick, secured by heavy chain. Our intent was to vibrate the piling through the seams of these slabs. The efforts failed and we went to the use of a 7000 lb. drop hammer with 40,000 lbs. of energy, and then were able to break through the concrete floor. (Figures 30 & 31) Shows the plan of lifting the swing span from the center pier area. As the river flow was 10 mph, it was difficult to position the piles for driving. Pile frames/guides were constructed on both sides of the wooden guide pier to position the piles for driving. (Figures 32 & 33) Show the constructed moving system, supported by 24 pile casings with ½ wall thickness. (Figure 34) Shows the jacks/lifting system. Jacks were 200T capacity, with two-foot lift. Four jacks required. Bridge was lifted with two, 1 3/8 tensile dywidag threadbars at each jack location. 90T capacity each bar. (Figure 35) Shows balance of lifting system with a lifting beam, two rods. Beam under floor beam and a short girder that was framed into floor beam.

8 (Figures 36-38) Show span being lifted. Figure 36 shows span being cut loose. Albeit it is not our policy to weld to older structures, in this case the post extended below the bottom of the floor beam. This section was where we welded the swing span to the pile false work for stability purposes. Piles were 12x74 HP, driven to 68kips bearing capacity. Please note the braced vertical column. This was a safety measure. As the swing span had been imbedded in the wooden guide pier on the downstream end, the possibility existed that the span could spring while it was being lifted. Bridge lifted level transversely but not longitudinally. Lifted longitudinally only to clear damaged machinery and other obstructions. (Figures 39-41) Bridge being repositioned. Figure 40 shows more clearly the lifting beams. (Figure 42) Shows moving device. Pull type system. Crossbeams were on rollers. Anchor positioned by threading bar. System had a 4 stroke, 15T capacity on each side. System repositioned three times for the move. (Figure 43) Span in final position, further damage assessment undertaken at end of the ring gear. Operation took 1 ½ hour to lift and level. At this point, the Fall Protection should be discussed. Notice that no one was tied off to a system. A collective decision was made that Fall Protection devices or systems could be more of a hazard or danger than a fall. Due to the instability of the span and also the guide pier, we did

9 not want anyone restricted in their movements. Full time life jacket use, strung rope, and buoys were insisted upon, as well as additional rescue boats. (Figure 43) As the river was rising it was exerting more pressure on the guide pier upstream. There was concern that it might break away under these forces. (Figures 44-47) Piling was driven and the guide pier was secured. Piling was positioned so that it could be used later in the rehabilitation of the guide pier. Runoff patterns were monitored. It was found that our location was greatly influenced by weather patterns to the North East. Rains, snowmelt of any consequences would appear at the location in three days. Work procedures were adjusted accordingly. The span is now in its proper position, but a lot of critical, time sensitive work remains to be done. It was getting close to the end of June, which brings us to the July 1 holiday. Crew had been working 24-hour days, seven-day weeks and the authors wanted the momentum to continue. The incentive was a pool! It was opened to everyone site workers, managers, headquarter personnel. Guess the day and time the bridge would be commissioned for railway operation. Larry McKee would be the Marshall. This idea kept everyone interested and committed for the last few days of repair and commissioning of the swing span operation. The span was opened at 1615 on June 30 th. Vice President of Engineering, Ernie Rewucki, won the pool!

10 (Figure 48) In total, the bridge was down 27 days, 15 hours and 20 minutes, with a repair cost to the bridge of $2.6 million and rerouting traffic costs of $3.1 million. The question that was asked at the end was not about money, but how the team was able to open the bridge in 27 days as opposed to the original 8-week estimate. Upon reflection of this, there were two aspects to the shortened time frame. One was the immediate call on experienced contractors and commencing to work on the structure the day of the collision. The second aspect was that all the response in terms of design, engineering review, and 3 employees handled execution of work: Jim Klett, Larry McKee and John Unsworth. We were able to resolve all issues that arose with agreement amongst the authors and they had the authority to make all decisions that needed to be made. It can only be suggested that if you find yourself or your organization in this type of crisis, then if you do have two or three experienced people, then you concentrate the response in their hands and let them get the job done.

11 Mission Bridge Reconstruction CP Rail Figure 1 Overview: CP Rail Network 2 Figure 2 Overview: Mission Bridge Vancouver Lower Mainland Figure 3 3

12 Overview: l Built in 1912 l Length l Single Track l Speed Limit 10 mph l 8 -Through Trusses l 3 -Through Plate Girders l One TT Swing Span Mission Bridge Span Figure 4 l Million Tons l Million Tons 4 Overview: Loaded Weight 4000 tons Loaded Chip Barge Figure 5 5 Correct path of barge movement Figure 6 6

13 Figure 7 Collision path of barge 7 Figure 8 Flow Impact point of barge 8 Figure 9 Upstream view of damaged bridge Canted 15 degrees from horizontal 9

14 Figure 10 Upstream end showing wood chip evidence. 10 Figure 11 Protection pier preventing structure from tipping into water. View 1 11 Figure 12 Protection pier preventing structure from tipping into water. View 2 12

15 Figure 13 Structure shifted 12 feet on center pedestal. 13 Figure 14 Upstream protection pier deflected into channel. 14 Figure 15 End post and floor beam. 15

16 Figure 16 Damaged components 16 Figure 17 Damaged components 17 Figure 18 Damaged components downstream end 18

17 Figure 19 Action Steps: Day Contacted Manager Structures Design in Calgary to help assess structural damage and determine corrective action Engaged the services of an experienced Steel Fabricator and River Contractor to be on site by 1000 for initial assessment Provided estimate of down time and cost to head office. 19 Figure 20 Attach cables from ring gear on pedestal to span. View 1 20 Figure 21 Attach cables from ring gear on pedestal to span. View 2 21

18 Figure 22 Support piling. 22 Figure 23 Damaged wheel rollers and wheel band assemblies. 23 Figure 24 Damaged Steel beams. 24

19 Figure 25 Damaged Steel beams. 25 Figure 26 Damaged drive assembly 26 Figure 27 Ring gear 27

20 Figure 28 Actual pile location Proposed pile location 28 Figure 29 Pile vibrator 29 Figure 30 Pile frames and guides constructed to position the piles for driving. View 1 30

21 Figure 31 Pile frames and guides constructed to position the piles for driving. View 2 31 Figure 32 Constructed moving system View 1 32 Figure 33 Constructed moving system 24 pile casings with 1/2 thick walls View 2 33

22 Figure 34 Lifting System Four jacks each with 200 ton capacity and a two foot lift. 34 Figure 35 Lifting system showing lifting beam and two rods. 35 Figure 36 Lifting span Step 1 36

23 Figure 37 Lifting span Step 2 37 Figure 38 Lifting span Step 3 38 Figure 39 Repositioning span. Step 1 39

24 Figure 40 Repositioning span. Step 2 40 Figure 41 Repositioning span. Step 3 41 Figure 42 Moving device. Pull type system. 42

25 Figure 43 In final position two feet above ring gear. 43 Figure 44 Rebuilding protection pier Damaged upstream protection pier showing high water level. 44 Figure 45 Rebuilding protection pier Pulled into alignment. 45

26 Figure 46 Rebuilding protection pier Completion of piling for pier 46 Figure 47 Rebuilding protection pier Completion of piling for pier 47 Figure 48 Summary: (1) Downtime.. 27 days 15hrs 20 min (2) Repair Cost... $2.6 million (3) Cost of Rerouting traffic..... $3.1 million ($115,000/day) (4) Quick response by experienced core group of CP Rail Staff minimized downtime of structure. All aspects of the response in terms of design, engineering review, and execution of remedial work were handled by 3 employees resulting in speedy resolution of issues and decision making. 48