547SHEAR CONNECTORS

New Hampshire Department of Transportation Standard Specifications – 2016 Description

1.1This work shall consist of furnishing and welding steel shear connectors to structural steel for use in composite beam

construction as shown on the plans. All requirements of this section apply to studs except for structural shapes, as noted. Materials

2.1General Requirements for Studs.

2.1.1 Studs shall be of suitable design for arc welding to steel members with the use of automatically timed stud welding equipment. The dimensions for standard headed type round studs shall conform to Table 547-1.

Table 547-1 - Dimensions of Standard - Type Shear Connectors Standard dimensions, inches Shank diameter Head diameter Minimum head height 3/4” 1-1/4” 3/8” 7/8” 1-3/8” 3/8” 2.1.2 An arc shield (ferrule) of heat resistant ceramic or other suitable material shall be furnished with each stud. The material shall not be detrimental to the welds or cause excessive slag and shall have sufficient strength so as not to crumble or break due to thermal or structural shock before the weld is completed. 2.1.3 A suitable deoxidizing and arc stabilizing flux for welding shall be furnished with each stud, either attached to the end of the stud or combined with the arc shield, for automatic application in the welding operation. 2.1.4 Only studs with qualified stud bases shall be used. (The stud base is the stud tip at the welding end, including flux, and 1/8” of the body of the stud adjacent to the tip). A stud base, to be qualified, shall have passed the test prescribed in Annex VI, AASHTO/AWS D1.5. The arc shield used in production shall be the same as used in qualification tests or as recommended by the manufacturer. Qualification of stud bases in accordance with Annex VI, AASHTO/AWS D1.5, shall be at the manufacturer’s expense. 2.1.5 Finish shall be produced by heading, rolling, or machining. Finished studs shall be of uniform quality and condition, free of injurious laps, fins, seams, cracks, twists, bends, or other injurious discontinuities. Radial cracks or bursts in the head of a stud shall not be the cause for rejection, provided that the cracks or bursts do not extend more than half the distance from the head periphery to the shank, as determined by visual inspection.1 (Footnote 1. Heads of shear connectors or anchor studs are subject to cracks or bursts, which are names for the same thing. Cracks or bursts designate an abrupt interruption of the periphery of the stud head by radial separation of the metal. Such interruptions do not adversely affect the structural strength, corrosion resistance, or other functional requirements of headed studs.) 2.1.6 Only bases qualified under Annex VI, AASHTO/AWS D1.5, shall be used. When requested by the Engineer, the Contractor shall provide the following information:

2.2Mechanical Requirements for Studs.

2.2.1 Studs shall be made from cold drawn bar stock conforming to the requirements of AASHTO M 169 (ASTM A 108), Grades 1010 through 1020, inclusive, either semi-killed or killed deoxidation. 2.2.2 Studs shall conform to mechan ical property requirements of Table 547 -2. At the manufacturer’s option, mechanical properties of studs shall be determined by testing either: (1) the steel after cold finishing, or (2) the full diameter finished studs. Table 547-2 - Mechanical Property Requirements for Studs* Tensile strength 60,000 psi min. Yield strength (0.2% offset) 50,000 psi min. Elongation (% in 50,000 psi ) 20% min. Reduction of area 50% min. New Hampshire Department of Transportation Standard Specifications – 2016 *These are standard headed type studs in 3/4 and 7/8” diameter that are used as an essential component in composite beam design and construction. 2.2.3 Mechanical properties shall be determined in accordance with the applicable sections of ASTM A 370. A typical test fixture shall be used similar to that shown in Figure 7.2, AASHTO/AWS D1.5. 2.2.4 Upon request by the Engineer, the Contractor shall furnish:

and 2.2.

mechanical tests, required by 2.2 for each stock size delivered. The quality control test shall have been made within the six-month period before delivery of the studs. 2.2.5 When quality control tests are not available, the Contractor shall furnish mechanical test reports conforming to the requirements of 2.2. The mechanical tests shall be on finished studs provided by the manufacturer of the studs. The number of tests to be performed shall be specified by the Engineer. 2.2.6 The Engineer may select studs of each type and size used under the Contract as necessary for checking the requirements of 2.1 and 2.2. Furnishing these studs shall be at the Contractor’s expense. Testing shall be at the Department’s expense.

2.3Structural shapes shall conform to AASHTO M 183 (ASTM A 36).

Construction Requirements

3.1Workmanship.

3.1.1 Stud shear connectors shall be welded to structural steel in the field, unless directed otherwise. If studs are shop welded, suitable staging shall be installed at the erected structure to permit the Engineer to safely take the necessary grade elevations. 3.1.2 At the time of welding, the studs shall be free from rust, rust pits, scale, oil, moisture, or other deleterious matter that would adversely affect the welding operation. 3.1.3 The stud base shall not be painted, galvanized, or cadmium-plated prior to welding. 3.1.4 The areas to which the studs are to be welded shall be free of scale, rust, moisture, paint, or other injurious material to the extent necessary to obtain satisfactory welds. These areas shall be cleaned by grinding to bare metal. 3.1.5 The arc shields or ferrules shall be kept dry. Any arc shields which show signs of surface moisture from dew or rain shall be oven dried at 250 °F for two hours before use. 3.1.6 Longitudinal and lateral spacings of stud shear connectors with respect to each other and to edges of beam or girder flanges shall not vary more than 1/2” from the location shown on the plans, except that a variation of 1” will be permitted, where required, to avoid obstruction with other attachments on the beam or where a new stud is being welded to replace a defective one. The minimum distance from the edge of a stud base to the edge of a flange shall be 1 ”, but preferably not less than 1 -1/2”. The minimum spacing between adjacent studs shall be 3” center to center for 3/4” studs and 3-1/2” for 7/8” studs. 3.1.7 After welding, arc shields shall be broken free from studs. 3.1.8 The studs, after welding, shall be free of any discontinuities or substances that would interfere with their intended function. However, nonfusion on the legs of the flash and small shrink fissures are acceptable.2,3 (Footnote 2. The fillet weld profiles shown in Figure 3.3 AASHTO/AWS D1.5 do not apply to the flash of automatically timed stud welds.) (Footnote 3. The expelled metal around the base of the stud is designated as flash in accordance with the definition of flash in Annex V of AASHTO/AWS D1.5. It is not a fillet weld such as those formed by conventional arc welding. The expelled metal, which is excess to the weld required for strength, is not detrimental but, on the contrary, is essential to provide a good weld. The containment of this excess molten metal aro und a welded stud by the ferrule (arc shield) assists in securing sound fusion of the entire cross section of the stud base. The stud weld flash may have nonfusion in its vertical leg and overlap on its horizontal leg; and it may contain occasional small shrink fissures or other discontinuities that usually form at the top of the weld flash with essentially radial or longitudinal orientation, or both, to the axis of the stud. Such nonfusion on the vertical leg of the flash and small shrink fissures are acceptable.)

3.2Technique.

3.2.1 Studs shall be welded with automatically timed stud welding equipment connected to a suitable source of direct current straight polarity power. Welding voltage, current, time, and gun settings for lift and plunge should be set at optimum settings,

New Hampshire Department of Transportation Standard Specifications – 2016 based on past practice, recommendations of stud and equipment manufacturer, or both. AWS C5.4, Recommended Practices for Stud Welding, should also be used for technique guidance. 3.2.2 If two or more stud welding guns are to be operated from the same power source, they shall be interlocked so that only one gun can operate at a time, and so that the power source has fully recovered from making one weld before another weld is started. 3.2.3 While in operation, the welding gun shall be held in position without movement until the weld metal has solidified. 3.2.4 Stud welding shall not be done when the base metal temperature is below 32°F or when the surface is wet or exposed to falling rain or snow. 3.2.5 Fillet weld option. At the option of the Contractor, studs may be fillet welded by the shielded metal arc process, provided the following requirements are met: 3.2.5.1 Welding is performed by a qualified welder, as per 550.3.16. 3.2.5.2 The minimum fillet size to be used shall be 5/16” for 3/4 and 7/8” diameter studs. 3.2.5.3 Welding shall be done with low hydrogen electrodes (E7018), 5/32 or 3/16” in diameter. 3.2.5.4 The stud base shall be prepared so that the base of the stud fits against the base metal. 3.2.5.5 All rust and mill scale at the location of the stud shall be removed from the base metal by grinding. The end of the stud shall also be clean. 3.2.5.6 The base metal to which studs are welded shall be preheated to 150 °F minimum. 3.2.5.7 Fillet welded studs shall be visually inspected as per AASHTO/AWS D1.5, 6.6.2.

3.3Stud application qualification requirements. Studs which are shop or field applied in the flat (down-hand) position to a

planar and horizontal surface are deemed prequalified by virtue of the manufacturer’s stud base qualification tests (Annex VI, AASHTO/AWS D1.5), and no further application testing is required. The limit of flat position is defined as 0-15 degree slope on the surface to which the stud is applied.

3.4Stud Production Control.

3.4.1 Pre-Production Testing. 3.4.1.1 Before production welding with a particular set -up4 and with a given size and type of stud, and at the beginning of each day’s or shift’s production, testing shall be performed on the first two st uds that are welded. The stud technique may be developed on a piece of material similar to the production member in thickness and properties. If actual production thickness is not available, the thickness may vary plus or minus 25%. All test studs shall be welded in the same general position as required on the production member (flat). (Footnote 4. Set-up includes stud gun, power source, stud diameter, gun lift and plunge, total welding lead length, or changes greater than ± 5% in current (amperage) and time.) 3.4.1.2 Instead of being welded to separate material, the test studs may be welded on the production member, except when separate plates are required by 3.4.1.5. 3.4.1.3 The test studs shall be visually examined. They shall exhibit full 360 degree flash. 3.4.1.4 In addition to visual examination, the test shall consist of bending the studs, after they are allowed to cool, to an angle of approximately 30 degrees from their original axes by either striking the studs on the head with a hammer or placing a pipe or other suitable hollow device over the stud and manually or mechanically bending the stud. At temperatures below 50 °F, bending shall preferably be done by continuous slow application of load. 3.4.1.5 If on visual examination the test studs do not exhibit 360 degree flash, or if on testing failure occurs in the weld zone of either stud, the procedure shall be corrected, and two more studs shall be welded to separate material or on the production member and tested in accordance with the provisi ons of 3.4.1.3 and 3.4.1.4. If either of the second two studs fails, additional welding shall be continued on separate plates until two consecutive studs are tested and found to be satisfactory before any more production studs are welded to the member. 3.4.1.6 Production welding. Once production welding has begun, any changes made to the welding set -up as determined in 3.4.1 shall require that the testing in 3.4.1.3 and 3.4.1.4 be performed prior to resuming production welding. New Hampshire Department of Transportation Standard Specifications – 2016 3.4.1.7 In production, studs on which a full 360 degree flash is not obtained may, at the option of the Contractor, be repaired by adding the minimum fillet weld as required by 3.2.5 in place of the missing flash. The repair weld shall extend at least 3/8 ” beyond each end of the discontinuity being repaired. 3.4.2 Operator qualification. The pre -production test required by 3.4.1, if successful, shall also serve to qualify the stud welding operator. Before any production studs are welded by an operator not involved in the pre-production set-up of 3.4.1, the operator shall have the first two studs welded by him tested in accordance with the provisions of 3.4.1.3 and 3.4.1.4. When the two welded studs have been tested and found satisfactory, the operator may then weld production studs. 3.4.3 Repairs. 3.4.3.1 If an unacceptable stud has been removed from a component subjected to tensile stresses, the area from which the stud was removed shall be ground smooth and flush. Where in such areas the base metal has been pulled out in the course of stud removal, shielded metal arc welding with low hydrogen electrodes in accordance with the requirements of 3.2.5 shall be used t o fill the pockets and the weld surface shall be flush. 3.4.3.2 In compression areas of members, if stud failures are confined to shanks or fusion zones of studs, a new stud may be welded adjacent to each unacceptable area in lieu of repair and replacement on the existing weld area (See 3.1.6). If base metal is pulled out during stud removal, the repair provisions shall b e the same as for tension areas except that when the depth of discontinuity is the lesser of 1/8” or 7% of the base metal thickness the discontinuity may be blended smoothly by grinding in lieu of filling with weld metal. Where a replacement stud is to be provided, the base metal repair shall be made prior to welding the replacement stud. Replacement studs shall be tested by bending to an angle of approximately 15 degrees from their original axes. The areas of components exposed to view in completed structures shall be made smooth and flush where a stud has been removed.

3.5Fabrication and Verification Inspection Requirements for Studs.

3.5.1 If a visual inspection reveals any stud that does not show a full 360 degree flash or any stud that has been rep aired by welding, such stud shall be bent to an angle of approximately 15 degrees from its original axis. The method of bending shall be in accordance with 3.4.1.4. The direction of bending for studs with less than a 360 degree flash shall be opposite to the missing portion of the flash. 3.5.2 The Engineer shall select a reasonable number of studs to be subjected to the tests specified in 3.5.1. 3.5.3 The bent stud shear connectors and other studs to be embedded in concrete that show no sign of failure shall be acceptable for use and left in the bent position. All bending and straightening when required shall be done without heating, before completion of the production stud welding operation, except as otherwise provided in the Contract. 3.5.4 If, in the judgment of the Engineer, studs welded during the progress of the work are not in accordance with the provisions of this specification, as indicated by inspection and testing, corrective action shall be required of the Contractor. At his own expense, the Contractor shall make the set -up changes necessary to ensure that studs subsequently welded will meet specification requirements. 3.5.5 At the option and the expense of the Department, the Contractor may be required, at any time, to submit studs of the types used under the Contract for a qualification check in accordance with the procedures of Annex VI, AASHTO/AWS D1.5.

3.6Welding Structural Shapes.

3.6.1 Structural shapes shall be fastened to the girders by shop or field welding, as shown on the plans. 3.6.2 Welding shall be performed in accordance with the requirements of 3.2.5. Method of Measurement

4.1Shear connectors will not be measured, but shall be the each final pay quantities in accordance with 109.11 for connectors

required as shown on the plans. Basis of Payment

5.1Shear connectors are a final pay quantity item and will be paid for at the Contract unit price per each complete in place in

accordance with 109.11. Pay item and unit: 547. Shear Connectors (F) Each

New Hampshire Department of Transportation Standard Specifications – 2016

Description

This work shall consist of furnishing and placing elastomeric bearing pads for structural members. The pads shall be

fabricated in conformity with the dimensions shown on the plans.

1.2This work shall consist of furnishing and placing elastomeric bearing assemblies for structural members. Assemblies shall

include elastomeric bearing pads, masonry and sole plates, connection bolts, anchor bolts, nuts and washers, shim plates and fabric bearing pads. The assemblies shall be fabricated in conformity with the dimensions shown on the plans. Materials

Elastomeric bearing pads shall be furnished according to the Plans and as specified herein.

Elastomeric compound shall be 100 percent virgin natural rubber meeting or exceeding the requirements of AASHTO LRFD

Bridge Construction Specifications, Section 18.2 – Elastomeric Bearings.

Internal steel plates shall conform to AASHTO M 270 (ASTM A709/), Grade 36 or 50 (or ASTM A36, A572).

2.4External load bearing plates shall conform to AASHTO M 270 (ASTM A709/A 709M), Grade 50W (345W).

2.5Preformed fabric bearing pads for external bearing plates shall conform to 550.2.6, Type 1.

2.6Anchor bolts shall conform to 550.2.5.

2.7The surface finish of bearing surfaces shall conform to AASHTO LRFD Bridge Construction Specifications, Section 11.4.6.

2.8Quality Assurance.

2.8.1 The Contractor shall furnish certified test results indicating compliance with each physical and chemical property specified. Construction Requirements

The fabrication, testing and installation shall be performed in accordance with the requirements of the Plans, AASHTO LRFD

Bridge Construction Specifications, Section 14, and Section 18.

The Contractor shall submit all shop fabrication drawings for approval in accordance with 105.02.

3.2.1 Fabrication shall not begin until written approval of the submitted shop fabrication drawings has been received from the Department.

The elastomeric bearing pads and assemblies shall be set on a carefully prepared surface as required by the applicable

provisions of 550.3.15.5.

The anchor bolts shall be installed as required by the applicable provisions of 550.3.15.4.

Elastomeric bearings. Following the manufacture of these bearings and verification of the int ernal steel laminates, the pin

groove openings shall be coated with an approved asphaltic sealer and the space filled with silicone caulking. Method of Measurement

Elastomeric bearing pads or elastomeric bearing assemblies will not be measured, but shall be the Each final pay quantities

in accordance with 109.11 for bearings required as shown on the plans. When more than one structure is included in the Contract, separate item numbers will be used for each separate and complete structure. Basis of Payment

Elastomeric bearing pads or elastomeric bearing assemblies are final pay quantity items and will be paid for at the Contract

unit price per each complete in place in accordance with 109.11. Pay items and units: 548.1X Elastomeric Bearing Pads (F) Each 548.2X Elastomeric Bearing Assemblies (F) Each