7-147 Section 713. Bridge Rehabilitation — Steel
713.01 Description
This work consists of repairing and replacing portions of structural steel bridges. The terms “beam ” and “girder ” are used interchangeably in this section.
713.02 Materials
Provide materials in accordance with the following sections : Steel Reinforcement ............................................................................. 905 Structural Steel ..................................................................................... 906 High Strength Bolts, Nuts and Washers ................................................ 906 Timber and Lum ber ............................................................................... 912
A.Steel for Temporary Supports . Provide temporary hanger rods that meet the requirements of ASTM A193/A193M Grade B7 (AISI 4140) . Provide rods with longitudinal Charpy V -notch impact values of 50 foot-pounds at 30°F . If necessary, heat treat steel to meet the Charpy V-notch impact requirements . The Engineer will reject rods with notches, nicks, or welds. The Engineer will base rod material acceptance on traceable MTRs . Provide heavy hex nuts for the tem porary hanger rods in accordance with ASTM A563 Grade DH or ASTM A194 /A194M Grade 2H and hardened circular washers in accordance with ASTM F436/F436M . Provide steel for temporary supports in accordance with ASTM A709/A709M Grade 36 and section 906 unless noted otherwise in the contract .
B.Sealant for Perimeter of Beam Plates. Select the sealant from the Qualified Pr oducts List . Provide sealant in caulking tubes.
C.Structural Steel for Retrofitting and Welded Repairs . Structural steel material used for retrofitting and welded repairs of bridge main members as defined in subsection 707.01. C must meet longitudinal Charpy V -notch impact test requirements.
D.Mat Material f or Temporary Supports . Provide structural -grade material with a minimum flexural strength of 1, 200 pounds per square foot and a minimum horizontal shear strength of 100 pounds per square inch. MDOT Standard Specifications for Construction Section 713 7-148 713.03. Construction
A.Providing and Fabricating Structural Steel . Provide and fabricate structural steel retrofits and replacements for existing structures and steel temporary support members in accordance with section 707. Submit shop drawings to the Engineer for approval before fabrication. Measure the pin dimensions of existing link plates from center -to-center . If pin dimensions differ by more than ⅛ inch from the dimensions shown on the plans, build replacement link plates to match existing dimensions instead of plan dimensions . The Engineer will direct changes to plan dimensions to fit existing dimensions. Submit a final hanger assembly report to the Engineer that lists the as-built dimensions of the proposed link plates and pins . Demonstrate that tolerances meet the requirements specified in subs ection 707.03.D .15. Install bushings in accordance with subsection 707.03. D.16. Assemble and ship pin and link plate pairs as a unit or match mark pairs.
B.Temporary Supports for Girder Ends . Fabricate and erect temporary supports as shown in the contract or propose an alternat ive design. Submit alternat ive design working drawings and calculations to the Engineer for approval a minimum of 14 calendar days prior to beginning work . Base alternat ive designs on loads and allowable soil pressures shown in the contract . Alternat ive designs must be in accordance with the AASHTO Standard Specifications for Highway Bridges , 17th edition. A Professional Engineer licensed in the State of Michigan must seal alternat ive designs. The Department reserves the right to verify the structural adequacy of the fabricated temporary support systems that are used. Verification may include visual inspection and NDT by Department personnel . The Department may require MTR submittals for material and shop drawings of original fabrication. Before using temporary supports, make corrections deemed necessary by the Department. Fabricate and weld temporary supports in accordance with the current AWS D1.1 . Welding personnel such as welders, welding operators, and tack welders must be qualified in accordance with AWS D1.1 . Testing must be in accordance with MDOT ’s Welder Certification Program . Welder performance endorsements from other agencies will not be accepted. The period of effectiveness for field welding personnel endorsed through MDOT ’s Welder Certification Program is 2 years unless welding personnel are not engaged in a welding process for at least 6 months or a specific reason exists to question the welder ’s ability . The Engineer may require a confirming performance test during the progress of the w ork. MDOT Standard Specifications for Construction Section 713 7-149 Do not w eld falsework, form support s, or accessories to structural steel . Provide hydraulic jacks with a stroke of at least 3 inches and pumps capable of extending jacks full stroke. Equip hydraulic systems with dial gauges that enable determination of the external loads . Provide hydraulic jacks with locking rings or other positive loc king devices to prevent settlement in case of hydraulic failure. Use locking devices during and after jacking cycles until placement of stable shims and removal of loads from jacks. Maintain temporary support s, including replacing supports in case of partial or complete failure. The Department reserves the right to provide labor, materials, and supervision to restore movement of traffic if the Contractor delays or makes inadequate progress in the repair or replacement of a temporary support, at no additiona l cost to the Department.
1.Column -Type Supports . After erection of column-type supports , but before loading temporary supports, use a plumb line to determine the horizontal offset of the top of the column from the bot tom of the column. Determine the horizontal offset of the hydraulic jack from the column centerline. Measure the column and hydraulic jack offsets parallel and perpendicular to the column web . Place jacks and temporary supports at each location so individu al offsets and the sum, in each measured direction, do not exceed 1 inch. Consider jack offsets positive, regardless of column offset directions. If structure embankment , compacted in place, is not required by the contract, compact the natural ground 9 inches deep to at least 95% maximum unit weight before placing temporary supports. Place a leveling course of Class 21AA aggregate, asphaltic cold- patching material, or other material approved by the Engineer before placing temporary supports on paved shoulders or roadways . Compact leveling material to 95% maximum unit weight before placing temporary supports. The Engineer may direct bracing of temporary supports, based on the Contractor ’s methods for performing rehabilitation work. Leave jacks in place until installation and operation of link plates and pins. Lines and pumps may be disconnected provided the equipment remains on the project. During the first 4 hours after loading, check for settlement of temporary supports hourly . Make subsequent settlement checks daily . MDOT Standard Specifications for Construction Section 713 7-150 To prevent girder ends from subsiding more than 1⁄16 inch from the original position, correct by adding shims to temporary supports.
2.Suspension -Type Supports . After placing stable shims, the Engineer may approve removing jacks. Repair concrete removed for erecting temporary support or to gain access to the girder end in accordance with section 712 and as approved by the Engineer .
3.Diaphragm -Type Supports . Place temporary supports on substru cture units as shown on the plans . Equally load and simultaneously advance hydraulic jacks placed in pairs. Leave jacks in place until repair or replacement and operation of structural components . Lines and pumps may be disconnected provided the equipment remains on the project. Propose grouting material and placement procedures to the Engineer for approval . Place grout on substructure units to create a smooth and level bearing surface for temporary supports . Select an H -1 grout material in accordance with section 1005. Form the space for grouting and clean the surface. Mix, place, and cure grout material in accordance with the manufacturer ’s recommendations . After curing, remove forming material to allow the Engineer to inspect the grouted space. Do not apply load to grout before the grout attains a minimum compressive strength of 4, 000 psi.
4.Salvaging Existing Column Supports . Existing temporary column supports that are not installed as a part of the contract are the property of the Department . Salvage existi ng temporary support components as directed by the Engineer. Do not cut vertical steel column sections, steel plates, or the timbers during removal of the temporary column supports . Cutting the channel portions of the temporary supports to ai d in removal is allowed. Stack salvaged components, as directed by the Engineer, within the project limits for pickup by others. All existing supports that are not salvaged are the property of the Contractor.
C.Pin an d Hanger Replacement
1.Measurement of Existing Hanger Assemblies. Take field measurements of hanger assemblies requiring replacement and submit as -built dimensions and a drawing showing the measured span and girder end to the Engineer. MDOT Standard Specifications for Construction Section 713 7-151 Measure existing pin diameters, the distance between pins from center -to-center, and the length, width, and thickness of link plates. Check girder web alignment by laying a straightedge across pin plate gaps at the top and bottom of the girder . Measure and report girder offsets. Close lanes or shoulders, in accordance with the Michigan Manual of Uniform Traffic Control Devices and the contract , to allow field measurements . Obtain the Engineer ’s approval for lane and shoulder closures . Do not l eave lanes or shoulders closed overnight for field measurements . Do not alter or damage the structure while performing field measurements.
2.Removal of Existing Hanger Assemblies. Remove existing hanger assemblies as shown on the plans and in accordance with subsection 204.03.A.5 and this subsection. If removing and replacing link plates and pins from more than one girder at a time, do not work on the same end of adjacent girders . Suspenders must remain operational on the girder end opposite removed link plates or pins. Support girder ends on stable shims, without using hydraulics, before removing components . Remove two pins and two link plates in each assembly . Cut the link plates and pins for removal in accordance with the following:
a.Cut link plates into two pieces with a sloping transverse cut that coincides with the joint opening between girder ends . If cutting link plates at the pin, position a sheet metal shield behind link plates to protect the girder.
b.Place a metal heat shield around pin holes before flame cutting pins. The Contractor may trim pin ends to within no less than 1 inch of girder pin plates . The Contractor may burn a hole through the center of pins to ease removal . If damage to the girder pin plate occurs during removal of the pin and hanger ass embly, submit a corrective action plan to the Engineer for review and approval prior to beginning repairs . Repairs must be designed by a Professional Engineer licensed in the State of Michigan. Perform the repairs at no additional cost to the Department.
3.Installation and Coating of New Hanger Assemblies. If end diaphragms prevent installation of new pins, flame cut an oblong hole in the web of one end diaphragm using a steel hole template at least MDOT Standard Specifications for Construction Section 713 7-152 ⅛-inch thick clamped to the channel section. After flame cutting, grind hole edges to a surface roughness no greater than 125 micro -inches per inch root mean square (rms) . Clean and coat holes and leave in the finished structure. Do not loosen or remov e end diaphragms. After removing pins, grind notches an d deep pits in the girder pin plate around the periphery of the hole to a surface roughness no greater than 125 micro -inches per inch rms . Before installing new hanger assemblies, clean and coat girder ends within 3 feet of each side of the centerline of pin holes . Clean and coat in accordance with section 715. Assemble new hanger assemblies before removing falsework shims.
D.Bearing Stiffeners at Temporary Supports . Erect bearing stiffeners at temporary supports in accordance with section 707. Achieve bearing fit at top and bottom flange by means of grinding or milling. Leave stiffeners in place as a permanent part of the structure. Field drill bolt holes in existing girders . Do not flame cut or air arc gouge existing girders or proposed attachments . Complete field drilling before cleaning and prime coating faying surfaces. Before erecting bearing stiffeners, clean and coat faying surfaces and other contact surfaces . Faying surfaces consist of surfaces int ernal to a connection that bear on an adjacent surface. Clean and coat faying surfaces and other contact surfaces in accordance with section 715. After bolting bearing stiffeners in place, clean and coat exposed areas in accordance with section 715. Clean and coat immediately after erection or during cleaning and coating of the remainder of the girder.
E.Retrofit Structural Steel . Erect retrofit structural steel in accordance with subsection 707.03. E. Leave retrofit structural steel in place as a permanent part of the structure. Field drill bolt holes in existing steel . Do not flame cut or air arc gouge the existing steel or attachments . Complete field drilling before cleaning and prime coating faying surfaces. Before erecting retrofit structural steel, clean and coat faying surfaces and other contact surfaces . Clean and coat retrofit structural steel in accordance with section 715. After bolting structural steel in place, clean and coat the exposed areas in accordance with section 715. Clean and coat immediately after erection or during cleaning and coating the remainder of the girder.
F.Sealing the Perimeter of Beam Plates. Before applying sealant, clean and dry surfaces between repair plates or angles and beams and other surfaces requiring sealant . Apply sealant along the perimeter of bolted or MDOT Standard Specifications for Construction Section 713 7-153 riveted plates or angles on steel beams, as directed by the Engineer . Apply sealant over the intermediate coat when dry to the touch. Apply sealant when air and surface temperatures are above 40°F . Immediately af ter applying sealant, tool to form a 5⁄16-inch fillet and force it against contact surfaces . Completely fill pits and depressions in steel beams at the seam line with sealant, regardless of width and depth. Apply a top coat over sealant after the intermedi ate coat cures.
G.Heat Straightening Damaged Bridge Steel . Select an MDOT -approved heat straighten ing contractor from MDOT’s Special Provision for Heat Straightening Damaged Bridge Steel . Submit MDOT Form 0388 Heat Straightening Plan for review and approval by the Engineer prior to heat straightening. Do not start heat straightening before the Engineer approves the heat straightening plan. Notify the Engineer at least 48 hours before beginning the heat straightening work . Ensure that the final straightened members retain as little residual stress as possible. If an area is exposed to precipitation, do not perform heat straightening unless the area is enclosed as approved by the Engineer . Apply heat at a temperature no greater than 1200°F and monitor w ith contact thermometers, pyrometric sticks, or other heat -indicating devices approved by the Engineer . Supply heat -indicating devices and make available to the inspector . Provide torch tips with a diameter ¾ to 1 inch. Heat only plastic yield zones . Use line, strip, spot, and “V” triangular heats . Do not use a “V” angle greater than 20 degrees . Limit the base of the “V” heat to 6 inches . Heat the “V” from the apex in a serpentine pattern to the base so only the area directly under the torch shows color . After each heat -straightening cycle, allow steel to cool to below 250°F before beginning the next heating cycle. Do not force cool. Calibrate temperature-sensing devices and jacking equipment . Submit a calibration certificate no greater than 12 months old to the Engineer prior to heat straightening and whenever there is reason to question accuracy . Provide jacking equipment with gauges. Straighten with as little mechanical force as possible. Use constraints that do not resist contraction during the cool ing phase and that do not produce local buckling of compression elements during the heating phase. Eliminate bends, creases, folds, and dents in web plates, flange plates, angles, stiffeners, channels, gusset plates, and torn areas. Straighten the flange plates and angles from the web to within ¼ inch of the tilt rotation at the edges with ½ inch of sweep over 20 feet, ¾ inch at the point of impact . Straighten the web to less than ½ inch out of plumb. MDOT Standard Specifications for Construction Section 713 7-154 Reduce localized deflections in the web to no greater than ½ inch vertically and horizontally measured with a straightedge. Straighten webs to the required tolerances before attaching cross frames or other lateral restraint devices . Do not f orce beams and girders into position and attach to cross fram es to hold in position. Do not f lame cut existing structural steel, except as shown on the plans or approved by the Engineer . Grind burrs, nicks, gouges, and scrapes to 125 micro -inches per inch rms and taper to the original surface using a 1:10 slope. Provide surface quality in accordance with ASTM A6/A6M . Report cracks or tears in beams and girders, or in other structural steel members not shown on the plans , to the Engineer . The Engineer will direct the repair methods. Prior to heat straightening, perfor m VT on the entire damage areas specified on the plans by an AWS CWI . All weldments located in or adjacent to damage areas and all weldments connecting components (clip plates, connection plates, intermediate stiffeners, etc.) that connect the damaged beam /girder to other beam/girder lines as determined by the Engineer must be completely VT by a CWI and completely MT by an American Society for Nondestructive Testing (ASNT ) Level II Technician. The testing must be performed in accordance with the current AWS D1.5 except as modified herein. Perform MT in accordance with ASTM E709 with dry powder using the yoke method. After heat straightening, perform VT on the entire heat -straightened areas . All weldments located in or adjacent to damage areas and all weldments connecting components (clip plates, connection plates, intermediate stiffeners, etc.) that connect the damaged beam/girder to other beam/girder lines as determined by the Engineer must be completely VT and MT as specified above. Complete and submit MDOT Form 0395 AASHTO/AWS D1.5 - Field Welding Plan to the Engineer for review and approval before performing field welding. Provide adequate notice to allow the Engineer to witness the crack repair work. Perform inspection and testing at no additional cost to the Department.
H.Rocker Realignment . Realign tilted rockers as shown on the plans and specified in this subsection. Coordinate the rocker realignment sequencing with proposed bridge repairs as shown on the plans and approved by the Engineer. If realigning rockers of more than one girder at a time, do not work on the same ends of adjacent girders . Do not work on both ends of the same girder. MDOT Standard Specifications for Construction Section 713 7-155 Do not j ack existing girder ends more than ⅛ inch above final rocker position. Before removing rockers from girders, support girder ends on stable shims without using hydraulics. Remove existing sole plate welds by grinding. Do not f lame cut or air arc gouge existing welds , except as shown on the plans and approved by the Engineer. Before welding sole plates in final position, clean and prime coat faying surfaces and other contact surfaces . Clean and coat faying surfaces and other contact surfaces in accordance with section 715. Position sole plates with rockers to provide the correct rocker tilt using rocker til t tables shown on the plans and approved by the Engineer. Field weld existing sole plates to girder flanges in accordance with subsection 707.03. E.7. Inspect and test field welds in accordance with subsection 707.03. E.7.e .
I.Cutting Simple Span Beam Ends . Coordinate sequencing of beam end cutting with proposed bridge repairs as shown on the plans and approved by the Engineer. Use a plasma cutting torch to cut no greater than ½ inch off each beam end to provide vertical beam ends 1 inch apart . Use a straightedge or guide to provide horizontal and vertical control while cutting beam flanges and webs . Mark cut lines on existing beams to verify that cutting operations do not damage existing sole plates and bearing stiffener welds. Do not damag e or remov e existing welds on sole plates or bearing stiffeners . Replace damaged welds at no additional cost to the Department . Field weld in accordance with subsection 707.03. E.7. Inspect and test field welds in accordance with subsection 707.03. E.7.e. Grind burrs, nicks, gouges, and scrapes to 125 micro -inches per inch rms on cut edges. After cutting beam ends and completing field welding, clean and prime coat exposed areas in accordance with section 715.
J.Structural Steel Welded Repair . Erect structural steel compon ents in accordance with subsection 707.03. E. Remove damaged or deteriorated structural components and replace with proposed structural components as shown on the plans and specified in section 204. Remove structural steel using mechanical methods, plasma c utting, or air-arc gouging. Do not f lame cut existing structural steel , except as shown on the plans. MDOT Standard Specifications for Construction Section 713 7-156 Prepare existing structural steel to accept proposed structural components and for field welding. Preparation may include field drilling coping holes and grinding, as shown on the plans. Field weld in accordance with subsection 707.03. E.7. Inspect and test field welds in accordance with subsection 707.03. E.7.e. After welding structural steel in place, clean and prime coat exposed areas in accordance wi th section 715. Clean and coat immediately after erection of structural steel components or during cleaning and coating of the remainder of the girder.
713.04 Measurement and Payment
Pay Item Pay Unit Structural Steel, Furn and Fab, Pin and Hanger ..................................... Pound Hanger Assembly, Field Measurement ..................................................... Each Hanger Assembly, Rem and Erect ............................................................ Each Heat Straightening Steel (Structure Identification) ........................... Lump Sum Stiffeners, Furn, Fab, and Erect .............................................................. Pound Structural St eel, Retrofit, Furn, Fab, and Erect ....................................... Pound Support, Column, Temp ............................................................................ Each Support, Suspension, Temp ...................................................................... Each Support, Diaphragm, Temp ....................................................................... Each Beam Plate, Seal Perimeter ...................................................................... Foot Rocker, Realign ........................................................................................ Each Cutting Beam Ends, Simple Span ............................................................. Each Structural Steel , Welded Repr, Furn, Fab, and Erect .............................. Pound Salv Support, Column, Temp .................................................................... Each
A.Hanger Assembly . The unit price for Hanger Assembly, Field Measurement includes t he cost of taking and recording measurements, maintaining traffic during measuring, and providing the Engineer with a location drawing showing the span and girder end where measurements were taken. The unit price for Hanger Assembly, Rem and Erect includes the cost of the following:
1.Removing two pins, two link plates, and shear locks;
2.Cleaning and applying and curing coating within 3 feet each side of the centerline of pin holes ;
3.Installing two new link plates and two new pins;
4.Protecting completed joint areas with enclosures, if required; and MDOT Standard Specifications for Construction Section 713 7-157 5. Protecting newly painted areas adjacent to joint areas. The unit price for Structural Steel, Furn and Fab , Pin and Hanger includes the cost of structural steel required for pins and link plates in rehabilitation work . The Engineer will measure steel as specified in subsection 707.04 for structural steel, furnish and fabricate pay items. The Engineer will measure, and the Department will pay for structural steel required for pins and plates in new const ruction as specified in subsection 707.04 for structural steel, furnish and fabricate pay items. The Engineer will measure, and the Department will pay for , Bushing as specified in subsection 707.04.
B.Heat Straightening Steel . The unit price for Heat Straig htening Steel includes the cost of attaining the required structural steel position, field welding, and NDT in accordance with subsection 707.03. E.7. The Department will pay for crack repair not shown on the plans as extra work.
C.Stiffeners, Furnish, Fabric ate, and Erect . The unit price for Stiffeners, Furn, Fab, and Erect includes the cost of field drilling, installing bearing stiffeners on existing steel, and cleaning and prime coating faying and other contact surfaces. The Engineer will measure structural steel for stiffeners as specified in subsection 707.04 for structural steel, furnish and fabricate pay items.
D.Structural Steel, Retrofit, Furnish, Fabricate, and Erect . The unit price for Structural Steel, Retrofit, Furn, Fab, and Erect includes the cost of field drilling, installing new structural steel on existing steel, and cleaning and prime coating faying and other contact surfaces. The Engineer will measure structural steel required for retrofit as specified in subsection 707.04 for structural steel, furnish and fabricate pay items.
E.Support, Temporary . The unit price for Support, __, Temp of the type required includes the cost of providing, placing, maintaining, and removing materials and equipment and removing and replacing concrete to access temporary supports. The unit price for Support, __, Temp of the type required includes the cost of lateral bracing as detailed in the contract . The quantity of Support, __, Temp of the type required indicates the number of girder ends requiring support , not the number of temporary support devices required.
F.Rocker, Realignment . The unit price for Rocker, Realign includes the cost of removing existing welds, determining correct rocker tilt, field welding, inspecting and performing NDT in accordance with subsection
707.03 E.7, and cleaning contact surfaces.
MDOT Standard Specifications for Construction Section 713 7-158 G. Cutting Beam Ends, Simple Span . The unit price f or Cutting Beam Ends, Simple Span includes the cost of cutting existing beam ends, field welding, and performing NDT in accordance with subsection 707.03. E.7, cleaning and prime coating exposed steel, and completing the work required to cut two simple span beam ends at one location.
H.Structural Steel , Welded Repair, Furnish, Fabricate, and Erect . The unit price for Structural Steel , Welded Repr, Furn, Fab, and Erect includes the cost of removing, disposing, and replacing damaged or deteriorated structural st eel components as shown on the plans, field drilling, field welding, NDT in accordance with subsection 707.03. E.7, and cleaning and prime coating structural steel components. The Engineer will measure structural steel required for welded repair as specified in subsection 707.04 for structural steel, furnish and fabricate pay items.
I.Salvage Support, Column, Temp . The unit price for Salv Support, Column, Temp includes the cost of removing and stockpiling temporary column supports, steel base plates, and timbers.
Source: Michigan Standard Specifications for Construction, 2020 Edition. Pages 511–522 of 1,146.