Presentation on theme: "Using VIRTIS for Permit Analysis By Terry D. Leatherwood, P.E."— Presentation transcript:
Using VIRTIS for Permit Analysis By Terry D. Leatherwood, P.E.
Dominion Virginia Power (Dominion), has submitted a USACE Joint Permit Application for Federal and state permits to build a hybrid clean coal power plant. The Virginia City site, consisting of reclaimed mined land, located near the City of St. Paul in Wise County, Virginia, was selected as the site for the new facility. As part of this project, a large generator needed to be moved to the St. Paul site. The load could not be moved to the site from Northern Virginia. The decision was made to bring it to Knoxville, Tennessee and move it into Virginia.
The generator was shipped by barge up the Tennessee River to Knoxville. The Barnhart Crane and Rigging Company would then move it from Knoxville to the Tennessee-Virginia State Line under a Permit issued by the Tennessee Department of Transportation. Barnhart would then complete the transfer by moving the generator from the Tennessee-Virginia State Line to the St. Paul site under a permit issued by Virginia.
ITEM WEIGHT: 795,869 LBS (361.76 Metric Tons) TOTAL WEIGHT: 1,404,869 LBS (638.6 Metric Tons) NO. OF AXLES: 72 (40 Axle Lines) TOTAL LENGTH: 365’ 5” (111.4 Meters) TOTAL WIDTH: 21’ 9 ½” (6.64 Meters) TOTAL HEIGHT: 17’ 3” (5.26 Meters)
LENGTH OF ROUTE (TN): 81 Miles (130 Km) LENGTH OF ROUTE (VA): 89 Miles (143 Km) TOTAL ROUTE ON LAND: 170 Miles (273 Km) NO. OF TN BRIDGES TO CROSS: 12 NO. OF TN CULVERTS TO CROSS: 40 NO. OF UNDERPASSES: 3
First Issue was the Vehicle Configuration. Barnhart wished to use a trailer with a minimum number of axles and only two (2) prime movers. One push and one pull truck. As a result, axle weights were over 20,000 lbs. This violates Tennessee Law (TCA 55-7-203). Barnhart asked for an exemption. However, because this provision is written directly into the Tennessee Code, it was determined that the Commissioner of Transportation does not have authority to grant an exemption.
Barnhart altered their vehicle. They added extra axles to the trailer to reduce the weight per axle to 19,640 lbs. They added two (2) extra prime movers. This allowed them to reduce the axle weight for the prime movers from 41,000 lbs per axle (worse case) to the legal limit of 20,000 lbs per axle. Total vehicle weight increased from 1.28 million lbs to 1.404 million lbs. However, the resulting vehicle configuration was in compliance with TCA code requirements.
Strawberry Plains Pike has an underpass under Interstate 40 on the East Side of Knoxville. The available vertical clearance was 16’-5”. The vertical clearance was insufficient for the 17’-3” tall vehicle.
The underpass is part of a diamond interchange with Interstate 40. A median cross-over was built. This allowed the vehicle to use the on and off ramps to bypass the clearance restriction and cross the Interstate at grade level.
US-11E Bridge over the Norfolk-Southern Railroad Calculations indicated that the main span girders and the central bent cap would be overstressed by the vehicle. The central bent straddles the railroad tracks which makes the installation of shoring impossible (at the bent) because it would interfere with railroad operations.
The spans were modeled in VIRTIS using the non-standard gage tools. The analysis indicated that the center three girders carried the majority of the load when a centerline path is taken. The exterior girders were not over-stressed. The model was used to test various shoring plans by introducing upward (pre-load) forces at various locations. This allowed development of a shoring plan which reduced the stresses in both the girders and the center bent cap to below operating levels.
Analysis indicated that the load would overstress the bridge over North Liberty Hill Street in the City of Morristown. The structure consists of a four (4) span, continuous concrete T-Beam bridge. The bridge was designed with very shallow girders so as to maximize the vertical clearance on the underpass route. The design resulted in a very low rating factor for this superload. Because of the underpass route, shoring the bridge would be very difficult.
The North Liberty Hill Street Bridge is located in an interchange. It was possible to use the interchange ramps to bypass this bridge. North Liberty Hill Street already had a median cross-over installed at the site to accommodate regular traffic. Therefore, no modification of the interchange was required to accommodate this superload.
The vehicle needed to move from US-11E to US-25E to go North from Morristown. The normal path would be to take the underpass under US- 25E and then turn onto the on-ramp to US-25E. However, underpass clearances were insufficient for the 17’- 3” tall load. In addition, it would be very difficult for the vehicle to make the sharp turn onto the ramp.
Instead of taking the normal on-ramp, traffic on US-25E was shut down. This allowed the vehicle to go up the normal off-ramp to gain access to US-25E. After traveling approximately 600 feet North on US-25E (on the wrong side), the vehicle could use a median cross-over (already in place) to move to the correct (Northbound) lanes.
The largest structure crossed in Tennessee by this vehicle was the US-25E bridge over Cherokee Lake. This bridge has six (6) steel girder spans. The maximum span length is 333 Ft (101.5 Meters) and the total bridge length is 1,714 Ft (522.4 Meters). Although this bridge was built to the specifications at the time of construction (Mid 1970’s), the girder ends were under-stiffened according to current specifications. An inspection also revealed slight bowing of the girder webs. The fear was that this superload would significantly bow the girder webs.
The decision was made to strengthen the girder webs at each abutment location. A plan to add web stiffeners was developed. The plans were checked and approved by TDOT. Barnhart hired a contractor to install the stiffeners which will be permanent additions to the bridge. The installation was monitored by TDOT inspectors.
A retaining wall, on the edge of US-25E, had failed causing failure of part of the roadway. Analysis indicated that the roadway should not be used for passage of the superload. Using 25E to re-configure the vehicle was not feasible. Using the overhead bridge to bypass the problem would take too much time due to the complexity of the required bridge analysis.
Barnhart developed a plan to stabilize the roadway shoulder. The solution did not offer a permanent fix to the problem, but it stabilized the area sufficiently to allow passage of the superload vehicle. Therefore, the original route to the on-ramp was used. With solutions available for all problems, a permit was issued to allow passage in Tennessee.
TDOT required Barnhart to post a $15 million dollar bond to cover any damages caused by passage of the vehicle. A detailed traffic control plans was developed. The project was coordinated with law enforcement for traffic control. Approval from officials in the various cities and localities was obtained.
TDOT inspected every bridge and culvert crossed by this superload in Tennessee. There were two inspections performed on each structure. One before the move and one after passage of the superload. The roadways were also inspected by TDOT before and after the move. As a favor to the National Park Service, TDOT also inspected a pedestrian tunnel in the Cumberland Gap Park.
The move started on Saturday, June 19 th in Knoxville, Tennessee. Day 1 was the only daylight move. After June 19 th, all other moves were made at night. During the early morning hours of June 24 th, the vehicle crossed over into Virginia. It reached the St. Paul, Virginia, site on July 7 th.
All costs were paid by Barnhart and their customer. This includes all costs for traffic control, bonds, engineering analysis, law enforcement, bridge and roadway strengthening. TDOT spent over 1,000 man-hours in support of this permit request. Tennessee law allows recovery of the “actual cost” for permits over 1 million lbs in weight. The TDOT fee for this permit was $300,000.
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