Replacement of old Truss spans with new TPG s at La Crosse, WI. Description of bridges between and La Crosse, WI and La Crescent, MN

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1 Replacement of old Truss spans with new TPG s at La Crosse, WI By Stephen J. Hill, P.E., Manager Projects US, Canadian Pacific Railway During 2000 and 2001, Canadian Pacific Railway replaced four, 1905 vintage, pin connected trusses with new Through Plate Girder spans. This was part of an overall scheme of replacement of similar trusses in this area that we have committed to doing. Description of bridges between and La Crosse, WI and La Crescent, MN La Crosse is a strategic point for CP on our principle main line from Chicago to Vancouver. We run about trains per day plus two Amtrak passenger trains for a total of about 40 MGT per year through here. Track speeds are limited to 25 MPH for passenger and 10 MPH for freights due primarily to the age and design of the trusses in the various bridges. However, due to curvature at the west end of the main channel bridge, we will probably never be able to run faster than 25 MPH with freights. Normal speeds on the territories approaching La Crosse are up to 79 MPH for passenger and 50 MPH for freights. We cross four bodies of water to get from Wisconsin to Minnesota. The first, from east to west, is the Black River (TOMA ), that we cross with a bridge consisting of 9-64 deck girder spans and a 310, 1905 vintage pin connected truss swing span. We have just begun a project to replace this swing span with a single leaf Bascule. Estimate for this work is on the order of $15,000,000. Plan is to do construction during 2002 and 2003 with the change out in early The next bridge crosses the French Slough (TOMA ) with deck girders and 2-82 through plates. The TPG s were installed in 1999 to replace a 164, 1905 vintage pin connected truss. Next comes the East Channel of the Mississippi River (TOMA ) with 1-25 and 1-40 deck girder, 4-148, 1905 vintage pin connected trusses and TPG. The TPG was installed 1995 to replace another pin connected truss. The replacement of these four trusses is the subject of this report, which was completed in the fall of Last is the main channel of the Mississippi River (TOMA ) with 1-40 and 1-75 deck girders, 1-161, and 1-247, 1905 vintage pin connected trusses and 1-357, 1905 vintage pin connected truss swing span. We have received an Order to Alter from the Coast Guard for this swing span that places it in line for Truman-Hobbs Act funding for replacement. This typically works out to about 95% of the funds

2 being provided by the federal government and the balance from the bridge owner. The Coast Guard s initial estimate for replacement of this swing span with a lift span is on the order of $25,000,000. Depending on the final arrangement proposed by the Coast Guard, we may replace one or more of the remaining fixed trusses prior to the replacement of the swing span. We have nothing definite from the Coast Guard as to when this funding may be available, but there are at least two other bridges over the Mississippi in line and farther along in the process than ours. That is 3555 of bridge, including two moveable spans, in 7115 of track. All of these bridges are single track, open deck structures. Replacement of trusses on the French Slough and East Channel of the Mississippi River The initial work here actually started in 1994 with acoustical emission testing of the then five trusses here, and the trusses at the other bridges over the Mississippi and French Slough. From this testing, it was confirmed that we were beginning to experience significant movement in several of the pins, especially on the west most truss on the East Channel. Our design office, in Montreal at that time, developed a replacement layout for this span, a 148 open deck TPG. The span was fabricated by Dominion Bridge of Winnipeg. This span was installed on with a cut out/roll in procedure. Lunda Construction was the contractor who handled the project, working in conjunction with our B&B forces. The actual change out took just over 15 hours from the last train to clear to the first train over the new span. We had to detour one Amtrak train, #8, over the BNSF from St. Paul to Chicago to allow us to have an uninterrupted work block. Amtrak #7 was the first train over the new span. Cost for this project was about $900,000. When the old span was cut up, we carefully dismantled the pin connections to visually inspect the conditions and to verify the acoustical testing indications. Pin conditions correlated well with the testing predictions, which gave us a good level of confidence that we could afford to take a reasonable amount of time to develop replacement schemes for the remaining trusses in the area. 6 Diameter pin from connection

3 The truss on the French Slough Bridge was replaced on with 2-82 open deck TPG s. This was to be the basic design style used for the East Channel trusses. Our design office in Calgary handled all of the design tasks for the French Slough. The spans were fabricated at Supreme Steel of Edmonton. A new pier was required and the existing truss piers were jacketed with concrete. Many of the piers of the bridges in the area actually date from the first bridges built here around 1876 and are masonry block on timber mats set on timber piling. A few have had concrete jackets applied over the years, but none of the ones at the French Slough or the East Channel had been done. Lunda was again the contractor for the French Slough work. They used a float out/float in method this time. As before, CP s B&B crews worked closely with the contractor through all phases of the construction. J.F. Brennan provided the barge and pumping equipment for the change out. Pumps were used to raise the truss by taking water out of the lift barge for the float out and to fill the lowering barges after floating in the new TPG s. This change out took just under 15 hours also, from last train to first train. Amtrak #8 was detoured over the BNSF here also and the new spans were in place in time to run a couple freight trains before Amtrak #7 was due. Cost for this project was about $1,200,000. Change out of the four remaining trusses on the East Channel of the Mississippi River During 1999, CP engaged in an evaluation process to select a Preferred Service Provider for bridge construction on our St. Paul and Chicago Service Areas. The desire was to have to go through a bid for a contractor only once for all of the upcoming work. After advertising our proposal, taking bids, evaluations and negotiations, Ed Kraemer & Sons of Plain, WI was selected. The premise of the relationship is that on each project, the railroad s forces and the contractor s would work interchangeably on all aspects of construction. The contractor would have the principle responsibility to provide the appropriate equipment and the railroad would provide skilled labor and experience in a live track construction environment. Kraemer s and CP s forces are now into their third year of this relationship and things have been working very smoothly on the several projects we have worked on together over the previous years. The railroad benefits from this by exposure of our people to current modern construction techniques and equipment and a steady work flow and work force requirement. This steady work stream contributes significantly to safe work since the work force is continually employed and working with the same group of people as opposed to lay offs and a high turnover in the crews. With the completion of the change out at the French Slough it was decided that we should move forward with replacing the four remaining trusses on the East Channel. Designs were prepared in Calgary to replace each truss with two 74 TPG s and construct four new piers, using the same basic designs developed for the French Slough replacement. As with all of the previous work, an extensive period was needed to obtain the necessary permits from the various agencies with interest and authority in the area. These included the United States Coast Guard, US Army Corps of Engineers, US Fish and Wildlife Service, Wisconsin DNR, Minnesota DNR (because the west truss sits astride the state line, we had to satisfy both states) and the Wisconsin State Historical Preservation Office. After several discussions with these organizations, we ended up having to alter the design layout. We were required to provide slightly larger openings towards the east end where the deeper channel is for recreational craft. Consequently, the replacement spans for the eastern two trusses became 1-74 and TPG s instead of 4-74 TPG s. This required one less new pier and the removal of one original pier after all the change outs were done. The new piers were constructed using pipe pile driven inside a caisson that was set outside the envelope of the truss so that work could proceed without interfering with train traffic. A caisson was set on either side of the truss and the piling driven to bedrock, about 130 down. The new piers under the longer spans had 14 pile, open ended 16 diameter with ½ walls, in each 12 diameter caisson. The new piers under the shorter spans required only 10 pile in each caisson. The piling were filled with concrete, rebar were extended above

4 the caisson for forming of the pier and a cap was poured to the top of the caisson, which sets about two feet above the normal pool elevation of the river. Above the caissons, the pier was formed and poured between each pair of caissons under the truss. This design allowed us to work on piling without interfering with the passage of trains and allowed the driving work to continue except while the engines passed the hammer. Each new pier contains a little over 200 cu yds of concrete and 30,000 lb. of rebar. The existing piers were encased with concrete to a thickness of up to about 16 and were stitched with dowels through the masonry with a series of rebar to make a solid structure. Additional rebar was used to stitch together any masonry blocks that were severely cracked. Encasement reinforcing for pier This pier work was done during the 2000 construction season, at least as much as weather would let us do since we got a slightly late start due to the permitting negotiations and limitations on when we could drive piling given the proximity of a nesting pair of bald eagles. Kraemer set up a staging area and temporary dock just above the Black River Bridge to facilitate movement of material and equipment to the site by barge, about 2 ½ miles away by water but only about ¾ of a mile by rail. We were able to establish a loading area on a spur track about ½ mile away from the bridge to haul concrete out to the site on rail using 6 lay down buckets on a flat car that we handled with a car mover. This allowed us to make very good use of time between trains to shuttle concrete out to the bridge for pours. The span design was done by our design group in Calgary and fabrication was by Acier Canam/Structal in Montreal, Quebec. Severe winter weather settled in the area in early December and we had to stop work earlier than hoped for. The winter weather seemed to change straight into early spring flooding. We experienced the third highest flood levels on record along the Mississippi River all the way from St. Paul to La Crosse and beyond. The floods crested in mid to late April and did not recede enough for work to resume at La Crosse until late May. There was work left to complete on the piers while false work was being prepared for erection of the new spans. Because of the spacing of the new and old piers, it was decided that the most effective replacement

5 scheme would be to float the old trusses out and roll the new spans in. The only variation was that the truss on the east end had to be rolled out because there was not enough room to fit barges with proper spacing to be able to float it out. The method used to lift the trusses was developed by Kraemer s engineers and had been used on some of their previous jobs. It was basically a pair of hydraulic tower jacks set at each end of the span and resting on barges. A beam ran between each pair of jacks and under the first panel point at each end of the truss. The towers could then be raised in a coordinated effort to gradually pick the truss up off of the pier. 100 Ton jacks were used on each tower to raise the truss. The jacks were raised about 6 at a time, bringing the beam up under the truss. Nuts were then tightened on the lifting bars, the jacks lowered and reset for another lift. A total lift of about 18 had to be made to gain sufficient clearance on the pier since the barges sank about a foot with the load imposed from the truss. The old trusses weighed about 375,000 lb. each. The two barges were tied together by the effective weight of the truss and were moved by two tugs. Once the spans had been moved clear, the process would be reversed and the truss lowered to the floor of the barge for cut up into large pieces that could be moved back to the dock area for final scrapping. It typically took about one hour to raise the truss clear of the piers and five minutes to float it out of the way. The new spans arrived by rail and were unloaded from the cars and placed on barges at Kraemer s dock on the Black River. The components were floated out to the site and erected on the prepared false work on the upstream side of the track. The roll in system was also developed by Kraemer s engineers and was an improvement over the common method using hydraulic jacks or winches. They had the new spans set on their bearings on Hillman Rollers that were guided in a channels set on the false work and piers Ton hydraulic rams were used to move the spans. They had a 3 stroke and could then be unpinned at the base, retracted to pull the base in and re-pinned for another move. Another set of jacks was pre-hung on the underside of the end floor beams to be in place for lowering the spans onto the pier. The 74 spans weighed about 125,000 lb. with the timber deck and walkway already on them for roll in. The 111 spans weighed about 230,000 lb. with deck and walkway. The same system was used to roll out the east truss onto false work. Preparing for roll out and roll in

6 Roll in took about forty-five minutes for each span to get to centerline and then about another forty-five minutes to lower into place on the pier. Once the old truss was out of the way, the top of the pier could be worked on to prepare a smooth surface for the new spans. Typically this required some grinding of the old bearing area and filling of minor depressions with an epoxy grout. The guide channel was laid out in the portions where the old bearings were in the way and then the roll in could start. Careful attention had to be paid to shimming the guide track to have even support across the top of the pier so the rollers moved easily. Once the span was in and over the centerline mark, the span was lowered using the jacks pre-hung on the floor beams. The span was lifted slightly to remove the rollers and channel, the new bearing pad placed and the span lowered into proper position. As the spans were set down, the deck could be cleared of the hydraulic pumps and other equipment and the track work started. Plates and tie pads were set in approximate location and rail laid in them and connected. A transit was used to align one rail from end to end of bridge and then the other was gauged to it. The rest of the spikes were driven and anchors applied and the track was ready to run trains. Total cost for this two year project was about $4,400,000. The actual change outs went extremely well thanks is great part to the planning done by Dennis Maney, Project Engineer for Kraemer and Bill Hager, Construction Supervisor for CP. We learned something each time to make the next one better. The first change out of the west truss was done on It was perhaps the hottest day of the year. Official high temperature at La Crosse was 97 with a heat index of 110 (like wind chill, but the other end of the scale). At 1800, the thermometer on the operator s house on swing span over the Mississippi River, which sits in the sun, read 115. Total time 13 hours 20 min out of a planned 14 hour track block The next morning we did a debrief with Kraemer and our people. We came up with several ideas about how to make things better for the next one, chief among them being cooler weather. Kraemer had some minor issues with the pumps used for the jacking. There were leaks in the new hoses they used which caused some minor delays to the jacking process. Cutting gas supply will be checked to ensure all are full tanks for change out day. Had one Oxygen tank run out in the morning. During the three weeks between change outs, the next spans were assembled, the old truss was lowered to the deck of the barge and cut into pieces to be hauled back to the dock area for final scrapping and the barges were repositioned for the next float out. The change out of the next truss going east was done on The temperatures when we started were around 65 degrees and got only as high as 85. Total time 10 hours 45 min out of a planned 14 hour track block We were also able to complete a lot of work that was done the following day last time. This included lowering the truss on the towers, installing the stub stringers, applying anchors, placing walkway pieces at end of spans, etc. Major contributors to improved time to do the work were the weather, experience with the procedures, improvements made from last time. Looking ahead to the next planned change out, there had been much discussion about the concern raised with potential instability of Pier 2 when we place a short, light jump span on one side after changing out the eastern truss, which was the next panned operation. To avoid this issue, we considered changing out both remaining trusses and install the three remaining new spans in a single-track window. We had gained a lot of experience and confidence in the procedures required after these two previous change outs and felt sure we can do those operations in a timely manner. It required additional rams and rollers to be able to do all of this at one time.

7 The last change out of the remaining two trusses was done on , but only after a long analysis of the stability question on existing pier 2. We completed the over turning analysis and determined we were unlikely to have a problem. This last change out was done with a longer track window and detouring both Amtrak trains for that day. Ready for roll in, looking west Total time 12 hours 30 min out of a planned 17 hour track block At the debrief the next morning we discussed the issue of the roll out of the truss. Due to its much higher weight (about 375,000 lbs. vs. 230,000 lbs. for the longer TPG) extra care was needed to ensure the channel for the Hillman rollers was continuously supported across the top of the pier. We had noticed some rippling of the channel as the truss moved in areas where we did not have sufficient shims. Over all, everyone was very pleased with the entire project. The detailed planning of each change out paid off handsomely in how well we were able to accomplish the work well within the planned track windows. Even when we did have some minor problems, because of the good planning, we were able to address the issue calmly, determine a proper solution and implement it with minimal disruption to the progress of the work. This is primarily due to the care taken up front in the planning of the work, the combined talents of Kraemer and our people working side by side, the experience of everyone involved and their ability to foresee potential problems and work out solutions in advance and the overall level of importance everyone felt about wanting to do this job right and safely the first time.

8 Completed job, looking east