Stud Welding Applications. Concrete Connections

Transcription

1 Stud Welding Applications Concrete Connections

2 Our Company Nelson Stud Welding is the world s leading producer of stud welding fasteners and equipment. We invented the stud welding process and have spread its acceptance to a wide variety of end-users. Our customers include leading producers of automobiles, ships, railroad cars, high-rise buildings, bridges, boilers and construction machinery just to name a few of our markets. Fastening with the Nelson System is quick, reliable and economical. It is a proven and tested method that successfully meets stringent fastening, material and welding codes. It has received approvals from recognized design agencies, code bodies and industry standard organizations. Each year, Nelson s customer list grows. We are constantly researching new product applications to solve customer assembly and fastening needs. In the construction industry, Nelson pioneered the use of stud welded shear connectors and headed concrete and deformed bar anchors. This brochure is intended to give you a comprehensive understanding of Nelson s products, equipment and capabilities that are specifically designed for the concrete products industry. Nelson s field sales personnel and warehouses are conveniently located to serve you. We would be pleased to assist you in selecting the optimum stud welding system to meet your specific application requirements and hope you join the large number of satisfied Nelson Stud Welding customers. The Process Electric-Arc stud welding is the most common process and is utilized whenever metal is fabricated. It is used to best advantage when the base plate is heavy enough to support the full strength of the welded fasteners, but is sometimes used with lighter gauge material. The stud is held in the welding gun with the end of the stud placed against the work. The cycle is started by depressing the trigger button start switch. The fastener is then automatically retracted from the workpiece to establish an arc. The arc continues for a predetermined period of time until portions of the stud and the base plate have been melted. Then, the welding gun automatically plunges the fastener into the molten pool of metal and holds it there under spring pressure. At the same time, the welding current is stopped and, when the molten metal solidifies, the weld is completed and the welding gun is removed from the stud. The entire operation is carried out under carefully controlled welding conditions. The molten metal is held in place by a ceramic ferrule which also serves to shield the arc. The weld metal is deoxidized by a flux in the weld end of the fastener, or protected by a shielding gas as in the case with aluminum. This results in a dense, strong weld which will develop the full strength of the fastener and base plate. The weld cycle depends on the diameter of the fastener and materials being joined and varies in time from 1/10 to 1-1/2 seconds. Welding currents range from 250 to 3,000 amps. Nelson provides the complete system. Studs Guns and accessories Integrated power/control systems Regulated current control 2

3 All components are stocked for immediate availability. Power sources and control systems may be either purchased or rented. Nelson s field representatives are able to provide set-up and equipment service as well as train your operators. The Anchors Nelson stud welded concrete anchors are available in two basic types: headed anchors and deformed bar anchors. Headed anchors. Type H4L and S3L are headed studs made from ASTM A29 Grades 1010 through 1020 colddrawn, low-carbon steel. They range from 3/4" to 14-3/16" in length and 1/4" to 1" in diameter. They may be welded together or piggybacked to obtain longer lengths. Headed anchors are used in all types of connections and inserts for a multitude of concrete products. Because of the head, these studs are very efficient concrete anchors that develop their capacity with embedment lengths much shorter than those normally required for plain bar, deformed bar, hooks or straps. Headed anchors 3/8 and greater in diameter have a tensile strength of 65,000 psi and yield strength of 51,000 psi. Numerous tests have shown these anchors to be highly ductile in shear, tension and combined loading applications resulting in increased connection reliability. As with all Nelson products, the steel used in the manufacture of headed anchors is carefully controlled and certified as to chemical and physical properties. Deformed bar anchors. Type D2L are made from cold-rolled, deformed steel reinforcing bars in accordance with ASTM A496 specifications. They have a tensile strength of 80,000 psi with yield strength of 70,000 psi. They are welded to embedment plates and angles which are used to anchor shear keys, bearing plates, column base plates and other concrete connections. Nelson stocks them in lengths from 9-1/8" to 36-3/16" and diameters from 1/4" to 3/4". Length is their advantage over headed anchors. They are used to extend the connection deeply into the concrete member to reinforce areas of potential cracks and failure. Nelson also supplies D2L anchors bent to suit individual applications and customer requirements. Deformed bar anchors are superior to handwelded rebar because they are produced from steel of known chemical and physical properties. They can be bent before or after welding without fear of brittleness that occurs with hand-welded rebar. The 3/8"- and 1/2"-diameter anchors can also be welded at a 45 angle with full weld strength and ductility. The Benefits Lower costs. Savings from 20 to 30% over hand-welded anchors. Speed. Stud welding is 3 to 4 times faster than hand welding. High Productivity. Less operator fatigue, no anchor preparation, less clamping, grinding or weld cleaning and stud welding speed result in increased output. Consistency. Stud welding is consistent time after time. Inspection, touch-up and repair costs are minimized. Higher Quality. Nelson studs are made from high-quality steel with certified chemical and physical properties. They are manufactured to rigid quality control standards. This results in anchors with excellent weldability, strength, and ductility. Nelson studs will insure that your end products are of consistently higher quality and acceptability. 3

4 Precast/Prestressed Tees Nelson deformed bar anchors are quickly welded to plates for use as shear keys and bearing plates for erecting, connecting and aligning tee sections. Certain sizes of D2L anchors can be welded to the plates at a 45 angle, eliminating a secondary bending operation and speeding production. Column Base Plates Nelson D2L studs as dowels effectively tie main reinforcing bars to the base plate. This eliminates drilling holes through the base and welding the reinforcement extensively on both sides of the plate. The stud-welded dowels are easily and quickly welded in place when compared with the close quarter hand-welding required with other methods. Beam-to-Column Connections Among the many types of beam-to-column connections possible using stud-welded anchors, the two illustrations beside indicate the flexibility in design available to the users of Nelson anchors. 4

5 Beam-to-Column Connections (Continued) Other approaches to beam/column connections are readily possible with Nelson anchors. Concrete-to-concrete, steel-to-concrete or concrete-to-steel connections are all easily and quickly designed, fabricated and installed with the Nelson system. Composite Structures Precast concrete slabs are tied to steel framing with Nelson shear connectors for obtaining composite action in such structures as parking garages and commercial buildings. Similar connections are widely used with precast elements to speed bridge deck rehabilitation projects. Fastening Architectural Panels (Facia) Fig. 8 shows a typical thin panel secured to a concrete framed building. Note the use of deformed bar anchors (D2L) bent 90 for assuring structural integrity. Vertical alignment is as quickly and easily achieved in concrete frame construction as in steel. 5

6 Fastening Architectural Panels (Facia) (Continued) A typical connection for architectural panels used with steel frame, metal deck composite buildings. Nelson D2L anchors are embedded in the relatively thin floor slab and extend back for maximum resistance to over-turning forces. Note the application of Nelson products for bottom connections to allow panel adjustments. Also, note inserts used in panel-to-panel connection or for framing. When attaching precast panels to steel framed structures, the threaded studs can be used as either temporary or permanent anchorage. They facilitate panel erection, providing temporary support while panels are quickly erected and aligned (minimizing crane and erection crew cost). Field welding makes the connection permanent. Studs are used for anchoring precast panels to concrete structures having either precast or poured-in-place concrete members. These methods are very compatible with in-plant casting practice. Threaded inserts - also called weld nuts - are similar to those used in standard wiretype screw inserts. The threaded inserts are hand welded to the insert plate over suitably sized holes 6

7 Fastening Architectural Panels (Facia) (Continued) Increasing use is being made of very thin architectural precast panels for building facia in new construction and in retrofit of existing buildings. Nelson studs welded to the steel frame or to steel plates embedded in concrete structures provide a low-cost, flexible connection regardless of building height. Stainless studs and angles prevent rust bleed thorough. Slot systems may be cast into panels during production. Insert Plates for Attachments Insert plates or channel sections cast into concrete during production can later be utilized for holding miscellaneous attachments such as pipe hangers, duct hangers, ceiling grids and electrical supports. By using the flexibility of the stud welding process, owner benefits such as faster erection and earlier completion for occupancy are realized. Shelf Angles and Brackets Shelf angles and bracket plates are easily installed using Nelson anchor studs. Simple calculations based on Nelson data provide confident connections. Usually, the studs selected are of sufficient length to provide full tension development as well as meet the shear requirements. When large numbers of anchors are used, it is desirable to have some of the studs longer than others so that the possibility of a "tension plane" is avoided. 7

8 Cantilever Beam Headed studs welded to 2" diameter coldrolled bars are the main reinforcing element in this cantilevered drop-in beam system. The use of studs eliminates an extensive, hand-fabricated rebar cage. The stud welded assembly can be easily inserted into forms for casting, allowing an additional 15% increase in form-use efficiency. Column-to-Column One method being used for a column-tocolumn connection employs sleeves cast in the beam. Main reinforcing bars are extended out of the top of the column and fit through the sleeves. On the top of each bar, a threaded stud is welded. Welding of the threaded stud is done under controlled conditions to assure full strength. The threaded studs extend through the upper column base plate and act both as a leveling device and full strength connection. Typical Stud Welding Applications Headed anchors and deformed bars welded in the fillet of an angle: Welding to heel of an angle: Welding to flat plate in: A. Plate vertical position B. Plate flat position C. Plate overhead position Deformed Bar Anchors welded at 45 angle: 8

9 Stud Welding Equipment and Power Stud welding equipment systems consist of an integrated Power/Control unit, a semi-automatic welding tool, and all of the necessary inter-connecting weld and ground cables with a C clamp. All systems are micro-processor controlled, measuring as many as 30 different weld parameters. These systems are closed loop and regulated to adjust automatically to conditions that affect power output, such as incoming power voltage and cable heating. Resettable weld counters are integral to measure production in any given period of time. Systems are available with one- or two-gun outputs, interlocked so that only one gun draws current at a single moment. Field diesel units are available to supply power where AC current is not available. Reference List Product and Embedment Data* Stud Welding References for Specifications, Testing, Quality, Properties and Welding Qualification Information* American Concrete Institute: ACI 318 Building Code Requirements for Structural Concrete, Appendix D., Anchorage to Concrete Prestressed Concrete Institute: PCI Design Handbook, Chapter 6., Design of Connections American Concrete Institute: ACI 349 Code Requirements for Nuclear Safety-Related Concrete Structures, Appendix B., Steel Embedments American Institute of Steel Construction: AISC Specifications for the Design, Fabrication and Erection of Structural Steel for Buildings Portland Cement Association: Strength Design of Anchorage to Concrete *Note: In all cases, the latest edition of these publications should be used for reference purposes. American Welding Society: ANSI/AWS D1.1 Structural Welding Code Steel, Clause 7, Stud Welding ANSI/AWS D1.6 Structural Welding Code Stainless Steel, Clause 7, Stud Welding AASHTO/AWS D1.5 Bridge Welding Code Steel, Clause 7, Stud Welding American Concrete Institute: ACI 355, Anchorage to Concrete, ACI 421, Guide to Shear Reinforcement for Slabs Eurocode 2, Part4, CEN/TS *Note: In all cases, the latest edition of these publications should be used for reference purposes. 9

10 Headed Anchors Stock Sizes D Stud Dia. 1/4 H4L 3/8 H4L 1/2 H4L 5/8 H4L 3/4 S3L 7/8 S3L 1 S3L L Length A H Part No. 3/ / / / /8 1 5/8 2 1/8 2 5/8 3 1/8 4 1/8 5 1/8 6 1/ /8 2 5/8 3 1/8 3 5/8 4 1/8 5 1/8 5 5/16 6 1/8 8 1/ / /16 3 3/16 4 3/16 5 3/16 6 3/16 6 9/16 8 3/ / /16 3 3/8 3 7/8 4 3/16 4 7/8 5 3/16 5 3/8 5 7/8 6 3/16 7 3/16 8 3/16 9 3/ / / /16 4 3/16 5 3/ /16 6 3/ /16 7 3/16 8 3/16 9 3/ / / / /4 6 1/4 8 1/

11 Physical Properties of H4L and S3L Anchors A S f y Yield A S f s Tensile Lbs. (min.) Diameter A S Nominal Area Lbs. (min.) 1/ ,405 2,994 3/ ,632 7,179 1/ ,014 12,763 5/ ,647 19,942 3/ ,531 28,716 7/ ,667 39,086 f s - Ultimate strength (tensile) 65,000 psi min. (> 3/8 diam.) f y - Yield strength 51,000 psi min. (> 3/8 diam.) Elongation 20% min. (> 3/8 diam.) Reduction of area - 50% min. Cold-finished, low-carbon steel, ASTM A29: C 0.23 max. Mn 0.90 max. P max. S max. A s - Area of stud shank ,055 51,051 Tension Capacity The following data are presented as guidelines only and are based on embedded studs with adequate spacing for full capacity development. Appropriate safety factors should be applied based on actual use. For more information consult Nelson Construction - Design Data. Shear Capacity Headed anchors embedded in concrete with an embedment length more than four times their diameter are capable of developing full shear capacity. Spacing is not as sensitive in shear as it is in tension. Spacing four times diameter between studs in a plane perpendicular to the shear force and six times diameter in the direction of the shear force is generally adequate to develop full-stud capacity. Free edges in the direction of the shear force and some spacing restrictions along a free edge apply. Consult Nelson Construction - Design Data and use proper safety factors and edge reinforcement. An upper bound limit for headed studs is approached at 0.65 A s f s when concrete strength exceeds 5,000 psi. Headed studs used as inserts have different values than those employed in composite design. For shear capacity of studs in composite design with and without metal deck, see the AISC code and commentary dated June 2010 and ACI 318, Appendix D, Anchoring to Concrete. Short Form Specification To insure that certified Nelson products are used, the following specification is suggested: Headed anchors shall be Nelson type H4L or S3L, flux filled, welded to plates as shown on the drawings. Studs shall be made from cold-drawn steel Grades C-1010 through C per ASTM A108 and welded pursuant to the manufacturer s recommendations. H4L and S3L Tension Capacity in Concrete (5.) Factored Tension Capacity (φnb) kips (6.) (7.) (8.) (1.) Anchor Size (2.) A.W. Length Db Head Diameter Head Thickness (3.) Le (4.) Factored Ultimate Strength of Anchor (φns) - kips 'c = 3000 psi NWT 'c = 4000 psi NWT 'c = 5000 psi NWT 'c = 3000 psi SLWT 'c = 4000 psi SLWT 'c = 5000 psi SLWT 'c = 3000 psi ALWT 'c = 4000 psi ALWT 'c = 5000 psi ALWT 1/4 x 3/ /4 x 1 1/ /4 x 2 11/ /4 x 4 1/ /8 x 1 3/ /8 x 1 5/ /8 x 2 1/ /8 x 2 5/ /8 x 3 1/ /8 x 4 1/ /8 x 5 1/ /8 x 6 1/ /2 x 2 1/ /2 x 2 5/

12 H4L and S3L Tension Capacity in Concrete (Cont d) (5.) Factored Tension Capacity (φnb) kips (6.) (7.) (8.) (1.) Anchor Size (2.) A.W. Length Db Head Diameter Head Thickness (3.) Le (4.) Factored Ultimate Strength of Anchor (φns) - kips 'c = 3000 psi NWT 'c = 4000 psi NWT 'c = 5000 psi NWT 'c = 3000 psi SLWT 'c = 4000 psi SLWT 'c = 5000 psi SLWT 'c = 3000 psi ALWT 'c = 4000 psi ALWT 'c = 5000 psi ALWT 1/2 x 3 1/ /2 x 3 5/ /2 x 4 1/ /2 x 5 1/ /2 x 5 5/ /2 x 6 1/ /2 x 8 1/ /8 x 2 11/ /8 x 4 3/ /8 x 6 9/ /8 x 8 3/ /8 x 10 3/ /4 x 2 3/ /4 x 3 3/ /4 x 3 3/ /4 x 3 7/ /4 x 4 3/ /4 x 4 3/ /4 x 4 7/ /4 x 5 3/ /4 x 5 3/ /4 x 5 7/ /4 x 6 3/ /4 x 7 3/ /4 x 8 3/ /4 x 9 3/ /4 x 10 3/ /4 x 12 3/ /8 x 3 11/ /8 x 4 3/ /8 x 5 3/ /8 x 5 11/ /8 x 6 3/ /8 x 6 11/ /8 x 7 3/ /8 x 8 3/ /8 x 9 3/ /8 x 10 1/ /8 x 12 3/ /8 x 14 3/ x 4 1/ x 6 1/ x 8 1/ Notes: (1.) Stock anchor size. (2.) A.W. = Length overall after welding. (3.) Le = Length of embedment under head of anchor. Ignores thickness of an embedment plate which will increase Le. (4.) φns = 0.75Asfs (5.) φnb = 0.70xλx24 (ƒ'c)leexp1.5, where φnb>φns, φns governs as φnn. Assumes no supplemental reinforcement. Pullout and side-face blowout strengths not considered. (6.) NWT = normal- weight concrete (λ = 1.0). (7.) SLWT = sand lightweight concrete (λ = 0.85). (8.) ALWT = All lightweight concrete (λ = 0.75). 12

13 H4L and S3L Shear Capacity in Concrete (1.) Anchor Size (2.) A.W. Length I/Ds (No. of Diam.) (3.) Factored Steel Shear Strength (φvs) - kips 'c = 3000 psi NWT (4.)(5.) Factored Shear Breakout Capacity (φvb) - kips Notes: (6.) (7.) (8.) (1.) Stock anchor size. 'c = 4000 psi NWT 1/4 x 3/ /4 x 1 1/ /4 x 2 11/ /4 x 4 1/ /8 x 1 3/ /8 x 1 5/ /8 x 2 1/ /8 x 2 5/ /8 x 3 1/ /8 x 4 1/ /8 x 5 1/ /8 x 6 1/ /2 x 2 1/ /2 x 2 5/ /2 x 3 1/ /2 x 3 5/ /2 x 4 1/ /2 x 5 1/ /2 x 5 5/ /2 x 6 1/ /2 x 8 1/ /8 x 2 11/ /8 x 4 3/ /8 x 6 9/ /8 x 8 3/ /8 x 10 3/ /4 x 2 3/ /4 x 3 3/ /4 x 3 3/ /4 x 3 7/ /4 x 4 3/ /4 x 4 3/ /4 x 4 7/ /4 x 5 3/ /4 x 5 3/ /4 x 5 7/ /4 x 6 3/ /4 x 7 3/ /4 x 8 3/ /4 x 9 3/ /4 x 10 3/ /4 x 12 3/ /8 x 3 11/ /8 x 4 3/ /8 x 5 3/ /8 x 6 3/ /8 x 7 3/ /8 x 8 3/ x 4 1/ x 6 1/ x 8 1/ 'c = 5000 psi NWT 'c = 3000 psi SLWT 'c = 4000 psi SLWT 'c = 5000 psi SLWT 'c = 3000 psi ALWT 'c = 4000 psi ALWT 'c = 5000 psi ALWT (2.) A.W. = Length overall after welding. (3.) φvs = 0.65Asfs (4.) φvb = 0.70xλx7*(Le/Da)- exp0.2* (Da)* (ƒ'c)*(edge distance-exp1.5), where Le/Da<8, alternately (if less) φvb = 0.70xλx9 (ƒ'c)*(edge distance-exp1.5). Where φvb>φvs, φvs governs as φvn. Assumes no supplemental reinforcement. Pryout strength not considered. (5.) A six-inches edge distance perpendicular to load is assumed. (6.) NWT = normal- weight concrete (λ = 1.0). (7.) SLWT = sand lightweight concrete (λ = 0.85). (8.) ALWT = All lightweight concrete (λ = 0.75). 13

14 Deformed Bar Anchors D Stud Dia. L Length Part No. 1/4 12 1/ /8 9 1/ /8 10 1/ /8 12 1/ /8 18 1/ /8 24 1/ /2 5 1/ /2 12 1/ /2 18 1/ /2 24 1/ /2 30 1/ /2 36 1/ /8 18 3/ /8 24 3/ /8 30 3/ /8 36 3/ /4 18 3/ /4 24 3/ /4 30 3/ /4 36 3/ Stock Sizes Physical Properties of D2L Anchors Dia. A S Nominal Area ASTM Designation A S f y Yield Lbs. (min.) A S f s Ultimate Lbs. (min.) 1/ D-5 3,500 4,000 3/ D-11 7,700 8,800 1/ D-19 13,300 15,200 5/ D-29 20,300 23,200 ¼ 0.41 D-41 29,000 33,200 f s - Ultimate strength (tensile) 80,000 psi min. f y - Yield strength (tensile) 70,000 psi min. A S - Area of stud shank Cold-finished, low-carbon steel, ASTM A29: C 0.23 max Mn 0.90 max P max S max Short Form Specification To insure that certified Nelson products are used, the following specification is suggested: "Concrete anchors shall be Nelson, flux-filled deformed bar anchors, type D2L, welded to plates as shown on the drawings. Studs shall be made from cold-worked, deformed wire per ASTM A496 and welded pursuant to the manufacturer s recommendations. 14

15 Minimum Embedment Length for D2L Anchors in Tension (normal wt. concrete) Normal-Weight Concrete Compressive Strength, f c (psi) Minimum Embedment Length for Full Anchor Capacity Development, After Welding (inches) Bar Diameter, d b 3/8 inch 1/2 inch 5/8 inch 3/4 inch 2, , , , For SI: 1 psi = kpa, 1 inch = 25.4 mm. Installation Parameters Parameter Tension Loads Shear Loads 1 d b = bar diameter Critical Edge Distance 10d b 1 Critical Spacing 7.5 d b 1 15 d b 1 20 d b 1 Minimum Cover at Anchor Base Section of IBC Section of IBC Allowable Tension Capacity for Nelson D2L Deformed Bar Anchors with Minimum Embedment Lengths Bar Diameter Stress Area, A 1 (inch 2 ) Allowable Tension Capacity 1 (lbs) Based on Steel Yield Strength Based on Steel Ultimate Strength 3/ ,925 2,200 1/ ,325 3,800 5/ ,075 5,800 3/ ,175 8,200 1 Here, Ω = 4. For SI: 1 inch = 25.4 mm, 1 inch 2 = mm 2, 1 lbf = N. D2L Shear Capacity in Concrete Deformed bar anchors embedded in concrete have shear capacities which may be conservatively calculated according to the formula used for headed anchors. An upper bound to shear capacity of 0.65 A s f s occurs as concrete strength exceeds 5,000 psi. Following are embedment length requirements and shear capacities for normal weight concrete. Appropriate spacing with regard to free edges and adequate distance between anchors should be maintained to reach full capacity. Good engineering practice dictates that safety factors appropriate to the connection usage should always be used. 1 Shear Capacity (normal wt. concrete) Nominal Bar Allowable Shear Capacity 1 Normal Weight Concrete 2 Diameter (inch) Area (inch 2 ) 2,500 psi 3,000 psi 3,500 psi 4,000 psi 3/ ,400 1,600 1,700 1,800 1/ ,900 3,100 3,200 5/ ,300 4,500 4,700 1 Minimum embedment length of 15d b (bar diameters). Here, Ω = 4. 2 Capacity Reduction Factors: Sand Lightweight Concrete = 0.85 All Lightweight Concrete = 0.75 For SI: 1 psi = kpa, 1 inch = 25.4 m, 1 inch 2 = 645 mm 2. 3/ ,300 5,900 6,500 15

16 USA 7900 West Ridge Road, Elyria, OH Telephone: Fax: Canada & Mexico Telephone: England Telephone: France Telephone: Germany Telephone: Italy Telephone: NELSON STUD WELDING is certified to the ISO TS International Quality System Standard, and is also certified to the ISO International Environmental Standard. 16