«3.0 TEMPORARY DETOUR BRIDGES Table of Contents 3.1 General 3.2 STORAGE SITES: 3.3 BID ITEMS: 3.4 INDEX OF PLAN SHEETS with H-Pile: 3.5 INVENTORY ...»
Eighteen units are required per span, nine on each side of the bridge. Four end units are required per bridge. The plan details show a left-handed end unit. (When viewing the front or roadway side of the unit, the bolt holes for the guard fence attachment are at the left end of the unit). Every detour bridge requires two left-handed end units and two right-handed end units. It is the Engineer's responsibility to see that one extra of each end unit and a minimum of two extra interior units are stored at the construction site at all times for immediate replacement of damaged units.
These extra units are not included in Columns 2 through 4. If there are not enough units at the stockpile site, the Contractor is required to fabricate and supply the additional units.
9. Anchor Plates:
Anchor plates are located at the bottom of the deck panels and used as washer plates for the 17" bolts that hold the barrier units in place. Two anchor plates are required for each barrier unit.
(See Detail No. 6).
10. Steel Grid Deck Panels:
KDOT owns two different panel types, the "K" panel and the "N" panel as mentioned above. The "K" panel was the first type used by KDOT and therefore, the "K" stands for Kansas. Due to inherent construction problems, the "N" panels were added to our inventory. They are a copy of a design used by Nebraska.
Each panel has a nominal width of 7'-8" and a length of 30'-6". Nine panels are required per bridge span with the length (30'-6") being placed perpendicular to the roadway centerline. See the Panel Layout detail in the plans. "N" panels can be easily identified from "K" panels when they are stockpiled at a storage site. Note No. 6 on the Inventory sheet states that "All 'N' type deck panels are identified by the painted RED end of a bearing bar. 'K' type deck panels do not have painted bearing bar ends." The location of the painted bearing bar end is in the middle of the short side of the panel. Another way of identifying the panels is to look at the bolt plates that are welded into the bottom of the panel grids. The "K" panel bolt plates are welded to and sit on top of the bottom flanges of the bearing bars. When these panels are in final position, the bolt plates are not in contact with the top flange of the rolled beams. (See Detail No. 7).
The welded "N" panel bolt plates are flush with the bottom of the bearing bars. When these panels are in final position, the bolt plates are in contact with the top flange of the rolled beams.
(See Detail No. 8)
Panel identification by bolt plates is slightly complicated in that "N" panels have both "N" and "K" bolt plates. For the first "N" panels ordered, the "K" bolt plates were intended to be a backup system if the "N-Connectors" slipped under traffic loads. The inherent problems of "K" panels are as follows.
a. The "K" panels bolt directly to the top flange of the rolled beams. Therefore, the bolt holes in the panel bolt plates must align directly above the bolt holes in the beam flanges. Due to warpage of the panels caused by weld shrinkage during fabrication, many holes do not properly align. The Contractor is then required to force the panels into alignment.
b. As stated above, the bolt plates are not in contact with the flanges when the panels are in their final position. Therefore, the high strength bolts cannot be tightened to their full capacity without bending the bolt plates. Service live load vibrations tend to loosen these bolted connections. The Maintenance Note of the General Notes sheet states that the Contractor is responsible for periodic inspection to assure that the bolted connections remain tight. The Contractor may elect to use self-locking nuts, double nuts or burr the threads to prevent the nuts from becoming loose. Inspection is required regardless of the nut type used.
11. N-Connector Plates:
"N" Panels are held in place by frictional clamping forces. These frictional forces are produced from the clamping effect of the panel bolt plates and the N-Connector plates on the top flange of the rolled beams. These clamping plates are staggered on both sides of the flanges. The high strength bolts are tightened by the turn-of-the-nut method in accordance with KDOT Specifications to develop the required clamping forces. (See Detail No. 9 and No. 10).
12. Steel Spacer Plates:
These plates are used in the wingwalls between the timber backwall and the steel H-pile. Four plates are required per abutment. Nominal 2x10 timbers may be substituted.
13. Steel Girders for "K" Panels:
The steel girders are W30x173 rolled beams. There are six beams per span and their alignment and spacing is shown in the Framing Plan. The top flanges have 1" diameter bolt holes spaced the length of the beams. These bolt holes are located on only one side of the web and are used to attach the "K" panels. Position the beams are to be positioned such that the bolt hole lines are furthest away from the centerline of the bridge. (See Detail No. 11).
14. Steel Girders for "N" Panels:
These girders are the same size and have the same framing plan as the girders for the "K" panels.
"N" panels do not require girders with the 1" diameter bolt holes in the top flange since they are attached by clamping plates, not direct bolting. However, eighteen girders (three spans) supplied for "N" panels were fabricated with these bolt holes so that they would be interchangeable with "K" panels. Twelve beams (two spans) supplied for "N" panels were fabricated with these bolt holes only at the ends of the beams. There are enough bolt holes at each end to bolt a panel directly to the beams. It was not intended that these end panels are to be directly bolted with KConnections. It was not known how well panels would remain in position under clamping friction only, so this provision was made for the end panels.
15. Bent Plate Diaphragms:
There are twenty bent plate diaphragms per span. See the Framing Plan in the Detour Bridge Plans for their locations. They bolt to the girder's intermediate and bearing stiffener plates.
The only bolts that are to be saved and stored at a stockpile site are the 17" long bolts, nuts and washers which attach the concrete barrier units to the deck panels and the drill and tap bolts used to attach the rocker plate to the beam flange. The drill and tap bolts do not require separate storage since the rocker plates are not to be removed from the flanges at the end of a job. 17" long bolts, nuts and washers are to be stored in open containers that have holes in the bottom to provide drainage. The tops of the containers are to be left open to eliminate the formation of condensation. All other bolts and lag screws will remain the property of the Contractor and are to be removed from the site.
EXAMPLE - Construction of a Temporary Detour Bridge:
SLIDE #1 * Looking along the centerline of a single span detour bridge.
* All detour bridges have been placed on tangent at 0.0 profile grade.
* Guard fence had not yet been attached when this picture was taken.
SLIDE #4 * Abutment wingwall with 2 H-pile. Currently, only the outermost pile is used.
* Steel channel caps bolted to the H-pile.
* Timber Backwall consists of two horizontal 4"x6" timber and vertical 3"x12" planks.
* Note the 1 1/2" steel spacer plates between the H-pile and the 4"x6" timber.
SLIDE #5 * Installing 3"x12" timber planks with 1/2" diameter lag screws.
The lag screws screw into 4"x4" and 4"x6" horizontal timber.
* Note the wingwall H-pile on the left side of the picture.
* Note the abutment channel caps bolted to the wingwall pile.
* Note the exterior girder end with the bearing stiffener.
* Note the horizontal timber members bolted to the bearing stiffener.
SLIDE #7 *Exterior girder and bearing rocker plate at the abutment.
*The wingwall is located to the left of the girder.
*The lower 4"x6" timber requires 2 notches at the exterior beam.
* All girders are interchangeable. If this girder was an interior girder, the bolt holes in the bearing stiffener plate would be used for attachment of a diaphragm.
* Note rocker plate and rocker plate bolt (1 1/4" Anchor Stud).
The nut should have a 1/4" gap to the top of rocker to allow the rocker to move under beam live load deflections.
* Note the bolt heads at the top of the beam flange. These are the drill and tap bolts that are not to be removed.
SLIDE #8 * Another look at an exterior girder at the abutment.
* Note the bolts attaching the bearing plate to the top flanges of the channel caps.
* All bearing plates are interchangeable - they must be used at piers or abutments.
Note the 1 1/4" anchor stud. This stud would hold a second rocker plate if this bearing plate was used at a pier.
* Note the bolts attaching the channel cap to the pile.
SLIDE #9 * Bearing plates attached to channel caps at the abutment.
* Note the bolts attaching the channel cap to the pile.
* Note the 1 1/4" anchor stud on the first interior bearing plate.
SLIDE #10 * A look at the abutment in an interior bay prior to construction of the earth berm.
* Note the timber backwall on the opposite side of the channels.
* Note the H-pile and the channel bolted to the pile.
* Girders are spaced at 5 foot centers.
SLIDE #11 * Typical pier construction.
* Note the diagonal bracing.
* Typical detour bridge layout attempts to avoid placing a pier in the flowline of a stream channel.
SLIDE #14 * Looking through a steel grid deck panel at the bolt holes in the bolt plates for a K-Connection.
* Note the top flange of the girder.
SLIDE #15 * Typical method of tightening the bolts from above.