510(g) Steel grid flooring will be measured and paid for in accordance with Section 409.
h.The weight of steel or brass shims required shall be included. Fabrication of structural steel, when a pay item, shall include fabricating; cleaning and shop painting structural units; bolts; nuts; washers; and transporting and storing units at the designated location. Erection of structural steel, when a pay item, shall include equipment and incidentals required to transport units from their designated storage location to the erection site, unloading and storing, erecting, cleaning, and field painting. The cost of testing unit(s) required by the specifications shall be included in the price for the structural unit(s). Payment will be made under: ———————————————————————————————— Pay Item Pay Unit———————————————————————————————— Structural steel (Type) Lump sum or Pound Fabrication of structural steel (Type) Lump sum Erection of structural steel (Type) Lump sum———————————————————————————————— SECTION 408—BEARING DEVICES AND ANCHORS
408.01 Description
This work shall consist of furnishing and installing bearing plates, pads, rockers, expansion devices, anchors, or other devices used in conjunction with bearings or anchorages at superstructure supports in accordance with these specifications and in conformity with the plans or as established by the Engineer.
408.02 Materials and Fabrication
a.Bearing material and bearing pads shall conform to Section 237 and those specified herein.
b.Metal plates, shapes, bolts, and bars shall be of structural steel conforming to Section 226 and those specified herein.
c.Metal parts shall be fabricated in accordance with Section 407.
d.Painting shall conform to Section 411.
e.Galvanizing shall be performed in accordance with Section 233.
408.03 Procedures
a.High-Load Multi-Rotational Bearings: High-load multi-rotational bearings including sole and masonry plates shall be any type shown on the plans and shall be provided by only one manufacturer.407.07 511Other high-load multi-rotational bearing designs may be acceptable provided they are supported by engineering analysis, engineering calculations, data and evidence of acceptable service life for the proposed materials, tests, and proven experience for the proposed bearing designs acceptable to the Engineer for the loads, forces, movements, and service conditions specified. Engineering analysis shall be performed by a Professional Engineer holding a valid current license to practice engineer - ing in the Commonwealth of Virginia. Notations: All dimensions are in inches: C = Clearance between pot and surface immediately above or below it. Dp = Diameter of elastomeric disc, inside diameter of pot bearing. Ds = Projected diameter of loaded spherical segment. G = Depth of pot bearing cavity. k = Depth of chamfer on pot bearing piston. Fy = Yield strength of steel in ksi. Lh = Horizontal design load on bearing in kips. Lv = Vertical design load on bearing in kips. Θ = ArcTan (Lh/Lv min) Rb = Minimum design rotation requirement of bearing in radians. Rc = Maximum construction tolerance rotation in radians. Rs = Minimum design rotation requirement of structure in radians. Rmax = Maximum radius to prevent unseating of spherical surfaces. S = Side of a square pot bearing plate. t = Thickness of elastomeric disc. w = Piston face width, pot bearing. OD = Outside diameter of a round pot.
1.Design: High-load multi-rotational bearings shall be designed to accommodate the loads, forces, and movements specified in the bearing schedule. Particular care shall be taken to ensure that all components of the bearings provide adequate capacity for the horizontal loads and forces specified. Maximum design stresses for bearing components shall not exceed the allowable design stresses of the applicable issue of the AASHTO Standard Specifications for Highway Bridges and the applicable sections of these specifications. Minimum rotation capacity, Rb, shall be the sum of Rc + Rs. Rc equals 0.02 radians. Rs equals the larger of 0.01 radian or the actual design rotations. The minimum horizontal bearing design capacity for fixed and guided expansion bearing types shall be 10 percent of the vertical capacity or as specified in the plans. The minimum horizontal bearing design for non-guided expansion bearing types shall be equal to the frictional resis - tance of bearing slide surfaces or as specified in the plans. Expansion bearings shall be designed for additional total movement capacity in each direction specified under “Design Movement” in the “Bearing Schedule.” The additional total movement capacity shall be 10 percent of the design movement or 1 inch, whichever is greater. Spacing between the guides of the bearing does not require this additional movement capacity. Bearings shall be designed so that rotational and sliding elements can be replaced with a minimum of jacking movement not greater than 1 inch.408.03 512 2. Rotational elements—Pot bearings:
a.Pot: Pot inside diameter, Dp, shall be the same as that of the elastomeric disc. Depth of pot cavity, G, shall be equal to or greater than: [(DP/2) x (Rs + Rc)] + 0.1 inch + k + t + w where: k = 0 for flat sealing k = 1.7 x the ring cross-section diameter for round sealing rings where rings sit 100 percent in the chamfer k = 1.2 x the ring cross-section diameter for round sealing rings where rings sit half recessed in the elastomeric disc and half in the piston chamfer. The details for the k dimension are provided in the plans. Section thickness of the pot beneath the elastomer shall be a minimum of 3/4 inch or Dp x 0.06 for bearings directly on concrete and 1/2 inch or Dp x 0.045 for bearings directly on steel masonry plates. Minimum outer plan dimensions of pots shall be determined by analyzing horizontal loads, internal elastomer pressure, and piston force due to friction in shear, bending, and tension, but the wall thickness shall in no case be less than the greater of 3/4 inch, 1.02 x Lv / (Dp x Fy) or the square root of (40 x Lh x Rb/Fy).
b.Elastomeric disc: Thickness of elastomeric disc, t, shall be equal to or greater than Rb x Dp/0.3. Area of elastomeric disc shall be designed for an average stress of 3,500 pounds per square inch. When using flat sealing rings, the upper edge of the disc shall be recessed to receive the rings so that they sit flush with the upper surface of the elastomeric disc. The disc shall be lubricated with a silicone compound conforming to MIL-S-8660 (Military Specification) or other approved equal. Polytetrafluoroethylene (PTFE) “shear-reducer discs” shall not be used with flat rings.
c.Piston: Outside diameter of piston shall be Dp – 0.04 inch. Piston thickness shall be adequate to resist the loads imposed on it but shall not be less than 0.06 x Dp. Piston thickness shall be adequate to provide clearance, C, between the top of the pot and the surface immediately above it as follows:
1.C = Rb x (0.7 x S) + 0.12 inch for pots square in plan.
2.C = Rb x (OD / 2) + 0.12 inch for pots round in plan. Piston face width, w, is the part of the edge of the piston that contacts the pot wall. When designing pistons for horizontal forces, w shall not be less than the greater of 0.03 x Dp, 1/4 inch or 1.59 x Lh/(Dp x Fy). Pistons for round seals shall have the lower corner chamfered at 45 degrees for a depth equal to 1.7 times the diameter of the seal where the seal is wholly within the piston thickness and 1.2 times the diameter where it extends into the elastomer for half its diameter.408.03 513 d. Elastomer sealing rings: Flat sealing rings shall conform to the following:
1.Width shall be equal to or greater than the larger of 0.02 x Dp or 1/4 inch but shall not exceed 3/4 inch.
2.Minimum thickness of each sealing ring shall be equal to or greater than 0.2 times the width.
3.Three rings shall be used. Rings shall be a snug fit to the pot wall and have their ends cut at 45 degrees to the vertical and to the tangent of the circumference with a maximum gap of 0.050 inch when installed. Ring gaps shall be staggered equally around the circumference of pots. Rings shall be free of nicks, burrs, or sharp edges. Round sealing rings shall conform to the following:
1.Rings shall be rolled into a circle from rod and brazed or welded. They shall fit the pot snugly so that they are in full contact with the pot wall when installed.
2.Ring diameters shall be equal to or greater than the larger of 0.0175 x Dp or 5/32 inch.
3.Rotational elements—Spherical bearings with PTFE/stainless steel surfaces:
a.Rotational elements—Spherical concave surfaces—PTFE: The spherical radius shall be determined such that the resulting geometry of the bearing is capable of withstanding the greatest ratio of horizontal load to vertical load under all loading conditions to prevent unseating the concave element. If required during construction, mechanical safety restraints shall be incorporated to prevent overturning of the bearing. Unseating of the curved surfaces relative to each other shall be prevented by transferring horizontal forces through specifically designed restraints or by control of the radius. Acceptable radius control is given when Rmax = Ds/[2 x Sin( Θ + Rc + Rs)]. Calculations showing the determination of the radius shall be submitted to the Engineer for approval. The projected area of the PTFE shall be designed for the following maximum average working stress: Maximum Contact Stress for PTFE at the Service Limit State (ksi) Average Contact Stress Edge Contact Stress Material Permanent All Permanent All Loads Loads Loads Loads Unconfined PTFE: Unfilled Sheets 1.5 2.5 2.0 3.0 Filled Sheets with Maximum Filler Content 3.0 4.5 3.5 5.5 Confined Sheet PTFE 3.0 4.5 3.5 5.5 Woven PTFE Fiber over a Metallic Substrate 3.0 4.5 3.5 5.5 Reinforced Woven PTFE over a Metallic Substrate 4.0 5.5 4.5 7.0408.03 514The concave shall face down whenever possible. Thickness of PTFE fabric in the compressed state shall be a minimum of 1/16 inch when measured in accordance with ASTM D 1777. Recessed sheet PTFE shall be at least 3/16- inch thick when the maximum dimension of the PTFE is less than or equal to 24 inches and 1/4 inch when the maximum dimension of the PTFE is greater than 24 inches. Woven fabric PTFE that is mechanically interlocked over a metallic substrate shall have a minimum thickness of 1/16 inch and a maximum thickness of 1/8 inch over the highest point of the substrate. The minimum center thickness of the spherical surfaces shall be 3/4 inch. Vertical clearance between rotating and non-rotating bearing parts shall be no less than 1/8 inch at maximum rotation.
b.Rotational elements—Spherical concave surfaces—Bronze: The spherical radius shall be determined such that the resulting geometry of the bearing is capable of withstanding the greatest ratio of horizontal force to vertical load under all loading conditions to prevent unseating the concave element. If required, mechanical safety restraints shall be incorporated to prevent overturning of the bearing. Bearing rotation of Rs + Rc radians shall be considered in the bearing design to prevent overturning or uplift of the bearing. Calculations showing the determination of the radius shall be submitted for the Engineer’ s approval. The spherical element shall be made from the following or other approved bronze alloys:
1.Type 1: ASTM B 22, Alloy C90500
2.Type 2: ASTM B 22, Alloy C91100
3.Type 3: ASTM B 22, Alloy C86300 The maximum design compressive stress for the projected area shall be: • Type 1: 2,000 pounds per square inch. • Type 2: 2,500 pounds per square inch. • Type 3: 8,000 pounds per square inch. The bearing surfaces shall have lubricant recesses consisting of either concentric rings, with or without central circular recesses with a depth at least equal to the width of the rings, or recesses. The recesses or rings shall be arranged in a geometric pattern so that adjacent rows overlap in the direction of motion. The entire area of all bearing surfaces that have a provision for relative motion shall be lubricated by means of the lubricant-filled recesses. The lubricant-filled areas shall comprise not less than 25 percent of the total bearing surface. The lubricating compound shall be integrally molded at high pressure and compressed into the rings or recesses and project not less than 0.010 inch above the surrounding bronze plate.408.03 515The minimum center thickness of the spherical surface shall be 3/4 inch.
c.Rotational elements—Spherical convex surfaces: The convex element shall be designed for rotation, Rb = Rc + Rs. The edge thickness shall be a minimum of 3/4 inch for bearings directly on concrete or 1/2 inch for bearings directly on steel masonry plates. For PTFE/stainless and bronze/stainless rotational surfaces, the stainless surface shall conform to one of the following:
1.Cold-formed stainless steel sheet complying to ASTM A 167 or A 240, Type 304, 0.060- to 0.090-inch thick, with a finish equal to or less than 20 micro-inch rms, connected to a structural steel substate by a continuous weld.
2.Solid stainless steel conforming to ASTM A 240, Type 304 or 304L, with a finish equal to or less than a 20 micro-inch rms connected to a structural steel substate by a continuous weld.
3.Stainless steel weld overlay a minimum of 3/32 inch thick with a finish equal to or less than 20 micro-inch rms on a structural steel substrate. If sheet PTFE is used for guided surfaces, it shall be pigmented. For bronze/carbon steel sliding surfaces, the surface finish shall be not more than 125 micro-inches rms.
4.Rotational elements—Disc bearings: Thickness of the disc, t, shall be equal to or greater than the larger of ∆ + [(Rs + Rc) x Dd x 0.5]/ ε max or 3.33 x Dp x (Rs + Rc) where: ∆ = deflection due to total compressive load ε max = strain due to all effects except for long-term creep The instantaneous deflection of the disc under total load at the service limit state shall not exceed 10 percent of the thickness of the unstressed disc, and the additional deflection due to creep shall not exceed 8 percent of the thickness of the unstressed disc. Deflection caused by rotation shall not exceed the lesser of the instantaneous deflection under total load at the service limit state or 10 percent of the thickness of the unstressed disc. The disc shall be designed for an average stress of:
a.3,700 pounds per square inch for Polyether Urethane Compound A.
b.5,000 pounds per square inch for Polyether Urethane Compound B. The section thickness of the plate beneath the disc shall be a minimum of 3/4 inch or Dp x 0.06 for bearings on concrete and 1/2 inch or Dp x 0.045 for bearings directly on steel masonry plates.408.03 516Vertical clearance between rotating and non-rotating bearing parts shall be no less than 1/8 inch at maximum rotation. The urethane disc shall be held in place by a shear restriction mechanism that is designed to allow free rotation of the bearing. The mechanism shall be designed to withstand the design forces on the bearing without exceeding the allowable shear stress of 0.4 Fy, bending stress of 0.55 Fy, and bearing stress of 0.8 Fy, not including shear resistance of the disc. The mechanism shall be connected to the bearing plates by welding, bolting, or machining out of the solid.
5.Non-rotational bearing elements:
a.PTFE sliding surfaces: The PTFE surface shall be made from pure virgin PTFE resin conforming to ASTM D 4745. It shall be fabricated as unfilled sheet, filled sheet, or fabric woven from PTFE and other fibers. Unfilled sheets shall be made from PTFE resin alone. Filled sheets shall be made from PTFE resin uniformly blended with glass fibers or other chemically inert filler. The maximum filler content shall be 15 percent. Sheet PTFE shall be a minimum of 1/8 inch thick, epoxy-bonded into a square-edge recess 1/16 inch deep. Woven fiber PTFE shall be made from pure PTFE fibers. Reinforced woven fiber PTFE shall be made by interweaving high strength fibers, such as glass, with the PTFE in such a way that the reinforcing fibers do not appear on the sliding face of the finished fabric. Woven fiber PTFE in the free state shall be a minimum of 1/16 inch thick when measured in accordance with ASTM D 1777 and shall be epoxy-bonded and mechanically fastened to the substrate using a system that prevents migration of epoxy through the fabric. Edges, other than the selvage, shall be oversown or recessed so that no cut fabric edges are exposed. PTFE sliding surfaces shall be designed for the maximum stresses specified in (a) 3 a.
b.Stainless steel sliding surfaces: The stainless surface shall cover the mating surface in all operating positions plus 1 inch in each direction of movement. This is to conform to (a)1. herein. Sheet stainless steel shall be 16- to 13-gage thick and connected to the substrate by a continuous weld around the entire perimeter. The sheet shall be in full contact with the substrate. Stainless steel welded overlay shall be a minimum of 3/32-inch thick after welding, grinding and polishing and be produced using Type 309L electrodes. Stainless steel sliding surfaces shall, preferably, face downward.
c.Guide bars and central guide keys: Central guide keys may be made integral by machining from the solid. Where a separate key or guide bar is used, it shall be fitted in a keyway slot machined to give a press fit and bolted or welded to resist overturning. Guide bars may be made integral by machining from the solid or fabricated from bars welded, bolted, and/or recessed at the manufacturer’ s option. Guide bars and central guide keys shall be designed for the horizontal force from applicable strength load and extreme event limit state load combinations, but not for less than 15 percent of the total vertical force from applicable service load combinations on the bearing. Bolted connections shall be designed in accordance with the applicable AASHTO Specifi - cations. Frictional resistance of bearing slide surfaces shall be neglected when calculating horizontal load resistance.408.03 517The total clearance between the key/guide bars and guided members (both sides) shall be 1/16 inch maximum. Guided members must have their contact area within the guide bars in all operating positions. Guiding off the fixed base or any extensions of it where transverse rotation is anticipated shall be avoided.
d.Sole and masonry plates: For masonry plates, the concrete nominal bearing stress on the loaded area shall not exceed 0.85 f’c. When the supporting surface is wider on all sides than the loaded area, the allowable bearing stress on the loaded area may be increased by the square root of (A2/A1), but not by more than 2. When the supporting surface is sloped or stepped, A2 may be taken as the area of the lower base of the largest frustrum of the right pyramid or cone contained wholly within the support and having for its upper base the loaded area A1 and having side slopes of 1 vertical to 2 horizontal. Sole and masonry plates shall be designed for applicable service, strength and extreme event limit state loadings. The minimum thickness of sole and masonry plates shall be 3/4 inch. When designing recesses in masonry plates for horizontal forces, the depth of the recess shall be designed assuming the contact area as one-third of the circumference. Minimum recess depth shall be 3/16 inch.
6.PTFE on guiding surfaces: PTFE on guiding surfaces, when they are used, shall be designed for stresses given in (a) 3.a. herein: PTFE, when used on guiding surfaces, shall be bonded to and recessed in their substrate. In addition, PTFE shall be at least 3/16 inch thick and mechanically fastened by a minimum of two screws to the substrate. The centerline of the screws shall be located a distance equal to twice the nominal screw diameter from the end of the PTFE strip. The top of the screws shall be recessed a minimum of 50 percent of the amount of protrusion of the PTFE above the guiding surface. Unfilled sheet PTFE used on guide bars shall contain an ultraviolet (U.V .) inhibitor/screen.
7.Materials: Steel, except stainless steel, steel for guide bars, and shear-restriction pins and sleeves, shall conform to ASTM A 709, with a minimum yield stress of 36 ksi. Exposed steel surfaces shall be painted. Guide bars and shear-restriction devices shall be as specified by the manufacturer. Elastomeric disc for pot bearings shall be a Shore A 50 durometer hardness and the base polymer shall be either 100 percent virgin natural polyisoprene (natural rubber) or 100 percent virgin chloroprene (neoprene) having the following physical properties as determined by the applicable ASTM tests:408.03 518Property Test Procedures Natural Rubber Neoprene Tensile Strength, psi, min. ASTM D 412 2250 2250 Elongation at Break, %, min. ASTM D 412 450 400 Hardness, Durometer A ASTM D 2240 50 ± 5 50 ± 5 Oven Aging, 70 hr/158°F for natural rubber, 70 hr/212°F for neoprene Tensile Strength, change, max. % ASTM D 573 –25 –15 Elongation, change, max. % –25 –40 Hardness, points change, max. +10 +15 Compression Set, 22 hr/158°F for natural rubber, 22 hr/212°F ASTM D 395 for neoprene, max. % Method B 25 35 Ozone Resistance, 20% strain 100°F ± 2°F , Mounting Procedure D 518, Method B 48 hr @ 25 pphm ozone by vol. ASTM D 1149 No Cracks 100 hr @100 pphm ozone by vol. ASTM D 1149 – No Cracks Low-Temperature Test ASTM D 2137 No No Brittleness @ –40°F Procedue B Failure Failure PTFE sliding surfaces shall be virgin PTFE resin-filled or unfilled PTFE sheets or PTFE fabric, all made from virgin PTFE resin. PTFE resin shall be virgin material, not reprocessed, conforming to ASTM D 4894 and D 4895. Specific Gravity shall be 2.13 to 2.19. Melting point shall be 327 degrees C ± 10 degrees
C.Filler material, when used, shall be milled glass fibers, carbon, or other inert filler materials. Adhesive material shall be an epoxy resin conforming to FS MMM-A-134, PEP film or equal, as approved by the Engineer. Unfilled PTFE sheet shall be made of virgin PTFE resin and shall conform to the following:
1.Tensile strength, 2,800 pounds per square inch minimum, ASTM D 4894.
2.Elongation, 200 percent minimum, ASTM D 4894. Filled PTFE sheet shall be made from virgin PTFE resin uniformly blended with inert filler material and shall conform to the following: Property Test 15% Glass 25% Procedures Fibers Carbon Tensile Strength, psi, min. ASTM D 4894 and D 4985 2000 1300 Elongation, min. % ASTM D 4894 and D 4985 150 75 Specific Gravity, min. ASTM D 792 2.2 2.1 Melting Point ASTM D 4894 and D 4985 327°C ±10°C408.03 519Fabric PTFE shall be made from virgin PTFE oriented multifilament and other fibers. The minimum thickness under the application of vertical load shall be:
a.1/16 inch up to 3,500 pounds per square inch load
b.3/64 inch from 3,500 pounds per square inch to 6,000 pounds per square inch load. Where the PTFE is to be epoxy bonded, it shall be etched by the sodium naphthalene or sodium ammonia etching process by an approved manufacturer. Stainless steel sliding surfaces shall conform to ASTM A 167 or A 240, Type 304, with a surface finish 20 micro-inches rms or less. Welded stainless steel overlay shall be produced using Type 309L electrodes. Sealing rings may be made only of metal and shall conform to the following: • Flat brass rings, ASTM B 36, half hard. • Round cross-section rings, FS QQB626, composition 22, half hard. Bronze elements shall conform to the following: • Type 1, ASTM B 22, Alloy C90500. • Type 2, ASTM B 22, Alloy C91100. • Type 3, ASTM B 22, Alloy C86300. Solid lubricant shall consist of a combination of solids having nondeteriorating characteristics, as well as lubricating qualities, and shall be capable of withstanding long-term atmospheric exposure, de-icing materials, and water. Molybdenum disulfide and other ingredients that may promote electrolytic or chemical action between the bearing elements shall not be used. Shellac, tars and asphalts, and petroleum solvents shall not be used as binders. Socket head cap screws shall conform to ASTM A 574, High Strength, 1960 Series. Adhesive material for bonding PTFE to steel shall be an epoxy resin conforming FS MMA- A-134, FEP film or approval equal.
8.Construction:
a.Flatness of bearings: The flatness of bearings after welding and fabrication shall be determined by the following method: A precision straightedge longer than the nominal dimension to be measured shall be placed in contact with the surface to be measured or as parallel to it as possible. An attempt shall be made to insert a feeler gage having a tolerance of plus or minus 0.001 inch under the straightedge. Since layering of feeler gages tends to degrade accuracy, the least number of blades shall be used. Flatness is acceptable if the feeler does not pass under the straightedge. Flatness tolerances are arranged in the following classes:408.03 520(1) Class A, 0.0005 inch x nominal dimension.
2.Class B, 0.00l inch x nominal dimension.
3.Class C, 0.002 inch, x nominal dimension. Nominal dimension shall be interpreted as the actual dimension of the plate, in inches, under the straightedge. In determining flatness, the straightedge may be located in any position on the surface to be evaluated, not necessarily at 90 degrees to the edges.
b.Rotational elements—Pot bearings: Pot bearings may, preferably, be made from a solid plate by machining or fabricated by welding a flame cut shape to a plate. Fabricated pots shall be manufactured in conformance with the AASHTO/AWS D1.5 Bridge Welding Code. The outside diameter of pots fitting into a machined recess shall be ±0.015 inch. For pots not so recessed, the tolerance on plan dimensions shall be +1/8 inch, –0 inch. The inside diameter of pots shall be machined to a tolerance of ±0.005 inch up to and including 20 inches and ±0.007 inch over 20 inches The tolerance on the depth of the pot cavity shall be +0.01 inch, –0 inch. The underside of pots shall be machined parallel to the inside to a Class A tolerance. Machined surfaces in contact with elastomer shall have a finish of 63 rms or better. Other machined surfaces shall have a finish of 125 rms or better. Elastomeric disc tolerance shall be:
1.Diameters greater than 20 inches, ±3/32 inch.
2.Diameters less than or equal to 20 inches, ±1/16 inch.
3.Discs may be made from up to three pieces, but the thinnest piece shall not be less than 1/2 inch.
4.Total thickness of all pieces shall be –0 inch +1/8 inch. Piston tolerances shall be:
1.Diameter greater than 20 inches, ±0.007 inch.
2.Diameter less than 20 inches, ±0.005 inch.
3.Sliding side, Class A tolerance.
4.Elastomer side, Class B tolerance.
5.Piston flange thickness, +1/8 inch, –1/32 inch.
6.Piston flange diameter, +1/8 inch, –1/32 inch.
c.Rotational elements—Spherical bearings: Spherical bearing machined diameters shall be ±0.015 inch. Convex radius dimensions shall be +0.000 inch –0.010 inch. Concave radius dimensions shall be +0.010 inch, –0.000 inch. Mating surfaces shall be as in Design section; external edges may be as cast or flame-cut. Lower surface of convex element shall be Class C tolerance. The tolerance on the overall thickness of concave or convex plates shall be ±0.03 inch. 408.03 521 d. Non-rotational elements—All bearings: Masonry and distribution plate tolerances shall be:
1.Plan dimensions less than or equal to 30 inches, -0 inch +3/16 inch.
2.Plan dimensions over 30 inches, –0 inch +1/4 inch.
3.Thickness tolerance shall be -0.030 inch +0.060 inch. Masonry plates used with pot or spherical bearings shall be Class C for the underside and Class A for the upperside tolerance. PTFE sheet sliding surfaces shall be bonded by the bearing manufacturer under controlled conditions and in accordance with the manufacturer of the approved adhesive system. After completion of bonding, the PTFE surface shall be smooth and free from bubbles. Filled PTFE surfaces shall be polished after bonding until smooth. PTFE fabric sliding surfaces shall be mechanically attached to a rigid substrate. The fabric shall be capable of carrying loads of 10,000 pounds per square inch without cold-flow. Tolerances of PTFE surfaces shall be:
1.Plan dimensions total design area, +5 percent –0 percent.
2.Substrate flatness, Class A. Stainless steel sheets shall be seal-welded around the entire perimeter using techniques that ensure it remains in contact with the backing plate. Finish shall be at least 20 micro- inches rms. Flatness shall be to Class A tolerance. Sole plates shall conform to:
1.Plan dimensions less than or equal to 30 inches, –0 inch +3/16 inch.
2.Plan dimensions over 30 inches, –0 inch +1/4 inch.
3.Centerline thickness, –1/32 inch +1/8 inch.
4.Flatness of surface in contract with steel beams, Class B:, in contact with poured in place concrete, none, in contact with stainless steel sliding surface, Class A: in contact with another steel plate, Class B.
5.No part shall be thinner than 3/4 inch.
6.Bevels shall be machined to an angular tolerance of ±0.002 radian.
7.Flatness of bevelled surfaces shall be Class A. Guide bars shall conform to:408.03 522(1) Length, unless integral with plate, ±l/8 inch.
2.Section dimensions, ±1/16 inch.
3.Flatness where it bears on another plate, Class A.
4.Bar-to-bar, nominal dimensions, ±1/32 inch.
5.Not more than 1/32 inch out of parallel. The overall bearing height shall not be more than 1/8 inch or less than 1/16 inch under nominal dimensions. Edges shall be broken and not sharp.
9.Testing:
a.General: Testing shall be performed on test bearings as specified herein to ensure compliance with the specification. As soon as all bearings have been manufactured for the project, the Contractor shall notify the Engineer, who will select test bearing(s) at random from the lot. Manufacturer’ s certification of conformance with applicable requirements for the steel, elastomeric pads, preformed fabric pads, PTFE and other materials used in the construction of the bearings shall be furnished along with notification of fabrication completion. Testing shall be performed at the manufacturer’ s plant. Bearing capacities that exceed the manufacturer’ s testing capacity shall be tested at an approved testing lab - oratory. If suitable test equipment is not available in the United States, alternative testing/ inspection shall be agreed upon between the Engineer and the manufacturer. The Engineer may witness the testing..
b.Sampling: Tests shall be performed on randomly selected samples from the production bearings. One bearing per lot shall be tested. A lot shall be defined as the smallest number of bearings as determined by the following criteria:
1.One lot shall not exceed a single contract or project quantity.
2.One lot shall not exceed 25 bearings. A lot shall consist of those bearings of the same type within a load category. Bearing types shall be fixed type bearings or expansion type bearings. Guided and non-guided expansion bearings will be considered a single type. One load category shall consist of bearings of differing vertical load capacity within a load range as follows: • Bearings less than or equal to 1000 kips, the load category shall be based on a range of capacity of 500 kips. • Bearings greater than 1000 kips capacity but less than or equal to 3000 kips capacity, the load category shall be based on a range of 1000 kips. • Bearings in excess of 3000 kips capacity, the load category shall be based on a range of 2000 kips. 408.03 523 c. Friction test: A sample from each lot of expansion bearings shall be tested. Specially made bearings shall not be used; only actual bearings to be used in the project shall be tested. The test method and equipment shall be approved by the Engineer and include the following:
1.The test shall be arranged so that the coefficient of friction on the first movement of the manufactured bearing can be determined.
2.The bearing surface shall be cleaned prior to testing.
3.The test shall be conducted at the maximum working stress for the PTFE surface with the test load applied for 12 hours prior to measuring the friction.
4.The first movement static and dynamic coefficients of friction shall be determined at a sliding speed of 1 inch per minute or less and shall not exceed the following: Bearings Pressure (psi) Materials 500 2000 3500 Unfilled PTFE, Fabric containing PTFE Fibers, 0.08 0.06 0.04 PTFE-Perforated Metal Composite Filled PTFE 0.12 0.10 0.08 Interlocked Bronze and Filled PTFE Structures 0.10 0.07 0.05 The bearing specimen shall be subjected to a minimum of 100 movements of at least 1 inch of relative movement and if the facility permits, the full design movement, at a speed of less than 12 inches per minute. After cycling, the static and dynamic coefficients of friction shall be determined again at a speed of less than 1 inch per minute and shall not exceed the specified coefficient of friction. The bearing shall show no appreciable sign of bond failure or other defects.
d.Proof load test: One bearing shall be tested from each production lot of fixed and expansion bearings. Load shall be applied to the test bearings equal to 150 percent of the rated design capacity of the bearing and simultaneously rotated 0.02 radians or the design rotation, whichever is greater, for 1 hour. During test or subsequently upon disassembly, the bearing shall show no sign of deformation or extrusion of elastomer or PTFE.
e.PTFE bond test: Bearings with sheet PTFE primary surfaces: At the option of the Engineer, one bearing from each production lot shall have a 180-degree peel test performed on the primary PTFE sliding surface in accordance with ASTM D 903. The minimum peel strength shall be 20 pounds per inch. Bearings with fabric PTFE primary sliding surfaces: One bearing from each production lot shall have the primary PTFE tested in shear as follows: The component carrying the fabric PTFE (or complete bearing at the option of the manufacturer) shall be subjected to the maximum vertical service limit state design load of the bearing and simultaneously, but transversely, a load equal to 13 percent of the vertical service limit state design load for a period of 1 minute. Slip or creep shall not exceed 1/8 inch during the test.408.03 524 f. Bearings represented by test specimens complying with these requirements: Such bearings will be approved for use in the structure.
10.Shipping and packing: Bearing assemblies including sole and masonry plates shall be securely fixed together as units so that they may be shipped to the jobsite and stored without relative movement of the bearing parts or disassembly at any time. Bearings shall be wrapped in moisture-resistant and dust-resistant material to protect against shipping and jobsite conditions. Care shall be taken to ensure that bearings at the jobsite are stored in a dry sheltered area free from dirt or dust until installation. Each completed bearing shall have its components clearly identified and marked on its top as to location in each structure in the project in conformity with the plans. When bearings are to be inspected on site, they shall be inspected within 1 week of arrival and may not be disassembled except under the supervision of the manufacturer. Following inspec - tion, the protective wrapping shall be reapplied and the bearings kept clean until installation. Removal of sole and top plates of bearings for separate attachment to the structure is not permitted except under the direct supervision of the manufacturer and with the permission of the Engineer.
11.Installation: Bearings shall be evenly supported over their upper and lower surfaces under all erection and service conditions. Bearings shall be lifted by their undersides only or by specially designed lifting lugs. When installing bearings, care shall be taken to avoid damage to and contamination of bearing surfaces. The centerlines of the bearing assembly shall be aligned with those of the substructure and superstructure. On guided bearings, special care must be taken to align the guiding mechanism properly with the designated expansion direction of the structure. Bearing straps or retaining clamps shall be left in place as long as possible to ensure that the parts of bearings are not inadvertently displaced relative to each other. Care shall be taken to remove straps or clamps before normal structural movement takes place, such as post- tensioning. The upper part of expansion and guided expansion bearings shall be located relative to the base of the bearing to compensate for deviations from normal atmospheric temperature. When bearings will sit directly on concrete with only an elastomeric, preformed fabric or lead sheet beneath the bearing, concrete bearing seats shall be prepared at the correct elevation and bush-hammered or dressed to the following flatness tolerance:
a.Bearing seats less than or equal to 30 inches long, 1/16 inch.
b.Bearing seats over 30 inches but less than or equal to 45 inches long, 3/32 inch.
c.Bearing seats over 45 inches in length, 1/8 inch.
d.There shall be no projecting irregularities exceeding 1/32 inch.
e.Bearing seats shall be level within 1:200 slope.408.03 525Where grouted bearing seats are used, the grout shall be the non-shrink type and of the strength specified on the contract drawings but not less than the concrete strength in the main support. Grout shall be placed at even density beneath the entire bearing surface without any voids or hard spots. Grout shall be allowed to reach optimum strength before placing any load on the bearing. The mating surface of the superstructure shall be level within a slope of 1:200. There shall be no local projecting irregularities exceeding 1/32 inch. The Contractor shall repair any damage to bearing finishes following installation. Welding procedures shall be established by the Contractor to restrict the maximum temperature reached by the bonded PTFE surfaces to a maximum of 300 degrees F and to restrict the maximum temperature reached by the elastomer (neoprene or natural rubber) to 250 degrees F . Temperatures shall be determined by temperature-indicating wax pencils or other suitable means. No load shall be transmitted to the bearings until erection of structural steel for spans contiguous to the bearing is substantially complete. Field welding of bearing plates shall be accomplished under the no load condition. Particular care shall be exercised to mask and protect the PTFE and polished stainless steel surfaces to protect them from blast abrasives and paint application during construction.
12.Shop drawings: Shop drawings shall be submitted to the Engineer for review in accordance with Section 105.10. These drawings shall include, but not be limited to, the following:
a.Plan and elevation view and section elevation of the bearing.
b.Complete details of all components and sections showing all materials incorporated into the bearing.
c.The maximum design coefficient of friction as noted in the Contract.
d.All ASTM or other material designations.
e.Vertical and horizontal load capacity.
f.Rotation and movement capacity.
g.Compression stress on all sliding surfaces, and elastomeric surfaces, at maximum and minimum design loads.
h.Complete design calculations.
i.Shop paint or coating requirements.
b.Steel Plates, Shapes, and Bars: Unless galvanizing is specified, items shall be painted in accordance with the plans.
c.Bronze Plates: Sliding surfaces of bronze plates shall be polished.
d.Copper-Alloy Plates: Finishing of rolled copper-alloy plates will not be required provided their surfaces are plane, true, and smooth.408.03 526(e) Self-Lubricating Plates: Plates shall be fabricated from cast bronze or rolled copper alloy. Sliding surfaces of plates shall be provided with annular grooves or cylindrical recesses or a com - bination thereof, which shall be filled with a lubricating compound. The lubricating compound shall be compressed into recesses under sufficient pressure to form a nonplastic lubricating inset. The inset shall comprise at least 25 percent of the total area of the plate. The frictional coefficient shall be not more than 0.10. The compound shall be free from material that will cause abrasive or corrosive action on metal surfaces and able to withstand extremely high pressures and atmospheric elements over long periods of time. Items shall be the standard products of the manufacturer of such materials for the application. Prior to assembly, the steel surface that will bear on the self-lubricating bearing plate shall be thoroughly lubricated with additional antioxidant lubricant furnished by the manufacturer. Coatings shall be removed before application of antioxidant lubricant.
f.Elastomeric Pads: Care shall be taken in fabricating pads and related metal parts so that effects detrimental to their proper performance, such as uneven bearing and excessive bulging, will not occur.
g.Placement: Bearing plates or pads shall have a uniform bearing over the entire area. Provision shall be made to keep plates or pads in the correct position during erection of beams or placement of concrete. Elastomeric pads and other flexible bearing materials shall be placed directly on masonry surfaces that have been finished to a roughness equivalent of a No. 36 to No. 46 grit. Pads, bearing areas, or bridge seats and metal bearing plates shall be thoroughly cleaned and free from oil, grease, and other foreign materials. Metal bearing plates or bottoms of prefabricated beams that are to bear on elastomeric pads shall be coated with epoxy, Type EP-4 or EP-5, conforming to Section 243 and then surfaced with a No. 36 to No. 46 silicon carbide or aluminum oxide grit. Bearing areas shall be finished to an equivalent roughness. Metal bearing plates shall be bedded on bridge seats as follows: The bridge seat bearing area shall be thoroughly swabbed with No. 1 paint, and three layers of duck, 12 to 15 ounces per square yard, shall be placed on it, each layer being thoroughly swabbed with paint on its top surface. Superstructure shoes or pedestals shall be placed in position while paint is plastic. As an alternate to duck and paint, sheet lead of at least 0.1 inch in thickness or preformed fabric bedding material at least 1/8 inch in thickness may be used when called for on the plans or approved in writing by the Engineer. Expansion devices shall be centered and aligned so that the vertical axis will be vertical at 60 degrees F .
h.Anchors: Anchors shall be designed for loads at the strength limit state and for the maximum loads at the extreme event limit state. Anchor bolts, nuts, and washers shall be painted or galvanized on superstructures having steel beams or girders. When superstructure units are concrete, anchor bolts, nuts, and washers, including bearing assemblies and insert plates, shall be galvanized. Shop paint shall cover the threaded end to 1 inch below the surface of masonry. Anchors shall be positioned to provide the required fit with bearing plates. Anchors shall be cast into the masonry and positioned by means of templates or other methods that will hold them securely in the correct 408.03 527position until concrete has set. The method of setting shall allow for proper finishing of concrete bearing areas. When permitted by the Contract or approved by the Engineer, anchor bolts may be placed in galvanized steel sleeves. Diameter and length of sleeves shall be as specified by contact documents or the Engineer but in no case shall diameter be greater than 4 times the diameter of the anchor bolt nor less than 2 times the diameter of the anchor bolt. Length of sleeves shall extend at least 2 inches below the plan elevation of the bottom of the anchor bolt. Sleeves shall be centered at the plan location of the anchor bolts. Top of sleeves shall be set at least 1/4 inch below the bridge seat elevation so as to prevent contact between the sleeves and the bearing assembly. Each sleeve shall include a 1 inch vent to permit air to escape from the tube during grouting. Vent tube shall connect to bottom of sleeve no more than 2 inches from the bottom of the sleeve. After girder and deck placement, the sleeves shall be filled with a non-shrink, high strength grout in accordance with Section 218. After the grout has set, the top surface of the grout shall be waterproofed with epoxy in accordance with Section 416. Anchors that are not designed to project through bearing plates shall be checked for proper projection above the masonry bearing area immediately prior to placement of bearing plates and beams. Nuts on anchor bolts at expansion ends shall be adjusted to permit free movement of the span. Angles for anchor assemblies to be attached to sides of concrete beams shall not be installed until beams have received their full dead load and supporting falsework has been removed.
408.04 Measurement and Payment
Metal bearing and expansion plates and anchors will be measured by shop scales in pounds of actual material placed in accordance with the plans. When not a separate pay item the Department will include the weight of plates and anchors in the weight of structural steel or reinforcing steel for payment. When a pay item, bearing plates will be paid for at the contract unit price per pound and shall include elastomeric and other flexible bearing pads. The cost of bedding and preparation for metal bearing plates shall be included in the prices for superstructure items. This price shall include furnishing all materials, galvanizing, painting, lubricating, and testing. Payment will be made under: ———————————————Pay Item Pay Unit———————————————Bearing device Pound——————————————— SECTION 409—STEEL GRID FLOORS
409.01 Description
This work shall consist of constructing a steel grid floor as shown on the Plans or elsewhere in the Contract in accordance with these Specifications or as directed by the Engineer.
409.02 Materials
Materials shall conform to Section 227.409.02
Source: Virginia Road and Bridge Specifications, 2020 Edition. Pages 538–554 of 1,065.