Structural Steel Erection Reference Manual

▶▶OBJECTIVE 2: CONNECTING BAR JOISTS Open web steel joists are normally welded (Figure 7.5) or bolted (Figure 7.6) to their supporting members. In instances where bar joists are utilized in steel framing, and columns are not framed with struc- tural steel members in at least two directions, a bar joist is field-bolted at columns to provide lateral stability during construction. This is dem- onstrated in Figure 7.7. Figure 7.5 Welded Joist Before an Ironworker goes out on a joist, the ends must be securely fastened. The ends of steel joists and steel joist girders (see Objective 3) should be attached to the support structure with the manufacturer’s recommended size and length of weld, or the appropriate size, length, and grade of bolt. Figure 7.6 Bolted Joist Figure 7.7 Field-Bolted Connection at Column Unit 7 — Installing Joists, Joist Girders, and Trusses 7.5 UNIT 7

If the bottom chord extension (depicted in both Figures 7.8 and 7.9) is to be bolted or welded, this will be noted on the structure’s drawings. Bar joists with extended top chords (Figure 7.10) or full-depth cantilever ends (Figure 7.11) can fail more easily than other types, and therefore require careful engineering. Figure 7.8 Ceiling Bottom Chord Extension Figure 7.9 Jack Joist/Joist Girder Bottom Chord Extension Figure 7.10 Top Chord Extension Figure 7.11 Square End Note: Configurations may vary from those shown in Figures 7.7– 7.11. 7.6 Structural Steel Erection UNIT 7

▶▶OBJECTIVE 3: JOIST GIRDERS AND JOIST GIRDER CONNECTIONS Joist girders are primary framing members used to support steel joists. They span columns and support roof or floor joists in the same manner that steel beams often do. In appearance, they look like a long span open web steel joist. Joist girders are typically used in single-story warehouse types of construction where the spans do not support more than the dead load of the roof (and where relevant, seasonal snow load). They are not generally used in multi-story construc- tion as the floor loads in these structures are much higher. Advantages of using joist girders instead of beam girders include a high strength to weight ratio, a more rigid structure because joists are placed at each column, the possibility of installing ducts and piping through the girder webbing, and the avail- ability of double- and single-pitched joist girders. Other advantages include larger bay sizes, resulting in fewer columns to erect, faster erection, and panel point arrangement. A panel point is the point at which bracing meets (usually referring to the top, not bottom, chord). Since a bar joist may only be placed at a panel point, when installing bar joist on a joist girder the need to measure each joist (as must be done when bar joist is erected on beam girders) is eliminated. Joist Girder Connections Most joists are connected to a girder by welding. An exception to this is the joist at or nearest to a column, which should be bolted. These connections typically use 3⁄4\" A325 bolts inserted into 13/16\" holes (4\" gauge) in girder bearings, the location where the joist girder bears on the column. If, however, a girder bearing is meant to transmit horizontal forces, it should be welded to a column. Figure 7.12 shows both bolted and welded joist girder connections. Figure 7.12 Joist Girder Details Unit 7 — Installing Joists, Joist Girders, and Trusses 7.7 UNIT 7

Stabilizer plates between bottom chord angles steady the bottom chord laterally and brace the joist girder against overturning dur- ing erection. Joist girder bottom chord struts should not be welded to the columns until the dead load is applied. At the designer’s option, a clip angle can be used in conjunction with the stabilizer plate when more weld is necessary to transmit horizontal forces (see Figure 7.13). Figure 7.13 Clip Angle with Stabilizer Plate Figures 7.14–7.17 show additional joist girder details. Square columns are configured similarly to the depiction of round columns in Figure 7.15. For Figure 7.16, note that bottom chord braces may be welded or bolted to a girder, but are always welded to a joist. Occasionally, due to the design of a structure, bar joists may not be present on both sides of the joist girder (e.g., the perimeter of a structure). When this occurs, it is typical that joists will extend past the centerline of the girder, as in Figure 7.17. Figure 7.14 Floor Joist Girder to Column Details Figure 7.15 Round Column to Joist Girder Details Figure 7.17 Joist Bearing on Only One Side of Girder Figure 7.16 Bottom Chord Brace Note: All of the joist girder dimensions shown in Figures 7.12–7.17 are subject to change as required by the physical size of large joist girders. Always check with a structure’s blueprints for actual size and dimension requirements. 7.8 Structural Steel Erection UNIT 7

▶▶OBJECTIVE 4: ERECTING JOISTS AND JOIST GIRDERS The first step in erecting joists and joist girders, as with beams and columns and other structural members, is to unload the materials (see Unit 5). Both time and trouble can be saved if joists and joist girders are unloaded at the job site according to a prearranged plan (see Unit 1, Objective 5). The planning and unloading for joists and joist girders is much the same as for any other structural member, except that because these pieces are comprised of materials that have been bent, formed, cut, assembled, and joined, they must be handled with caution and special care to prevent damage. Figure 7.18 shows a bundle of bar joists being unloaded at a job site. Erecting Joists Bundles of stacked bar joists can easily be set with one choker. The choker should be run through the center of the joists with both eyes placed on the hook. Bar joists are usually 1⁄2\" shorter than the span of the bay from the center of the first support beam to the center of the opposite support beam. The ends of the bar joists should be even before leaving the ground or it will be difficult to set them on the beams. In some instances only one joist can be set at a time. When this happens, an Ironworker may need to climb out on the joist to unhook it; however, some bar joists are very limber until the bridging is installed and will not support the weight of an Ironworker. One method to release a load without exposing an Ironworker to the potential fall hazard is to place a shackle on the load line above the ball with one end of the choker attached to it and to run the other end of the choker through the joist(s) at the center, placing the eye of the choker over the hook. This procedure allows the operator to unhook the joist without someone having to climb out on the joist; however, to accomplish this, the safety latch on the hook must be deactivated (tied or taped open). If a safety latch must be deactivated, ensure that all federal, state, provincial, and local standards and regulations are followed. Figure 7.18 Bundle of Bar Joists Being Lifted from a Truck Unit 7 — Installing Joists, Joist Girders, and Trusses 7.9 UNIT 7

Remember: Tying back the safety latch on a headache ball is gen- erally not allowed; however, when it is necessary to deactivate the safety latch, special precautions, procedures, and/or training may be required. Once the joist is in place and the operator raises the load, be certain that when the choker is pulled free of the joist, the choker does not get hung up and accidentally displace the bar joist. 7.10 Structural Steel Erection Figure 7.19 Landing Stacked Bar Joists When bar joists are set (or “landed”) on a struc- ture, as in Figure 7.19, communication between the Ironworkers who are setting the joists is nec- essary. A sufficient amount of bearing on each end is important to ensure that the joists will not fall. On long span joists, attach hoisting cables at a panel point approximately 1/5 of the span from each end. This method will minimize erection stress in the joist. When working with long span joists, too, ensure that the angle of the hoisting cables does not exceed 30 degrees from the verti- cal axis. If a joist has a span greater than 150 feet, two cranes should be used. Standards require that all joists 40 feet long and longer have a row of bolted bracing installed before the hoisting lines are slackened. Each joist should be adequately braced before any loads are applied, and bracing lines must be anchored to prevent lateral movement. Erecting Joists by Panelizing the Bar Joists One common method of erecting joists involves panelizing the bar joists. When used properly, this method reduces Ironworker exposure to fall hazards, and is very safe, effective, and efficient. The basic steps for panelizing bar joists are as follows: 1. 2. 3. Inspect the site to ensure adequate space and conditions exist to build and stockpile joist panels. Set up a template at the proper width and make certain that it is square, plumb, and laterally braced. Install the bar joists on the template at the proper spacing. UNIT 7

4. Install and fasten the bridging (see Objective 5 for details). 5. Remove the panel from the template and stage for erection. 6. Hoist the panel to the proper location (bay) and place, align, and position it correctly on the joist girders, beams, or other bearing surfaces. 7. Permanently fasten the joists. 8. Release the load. Erecting Joist Girders Joist girders are set between columns or between a column at one end and a (pre- cast concrete, block, or brick) wall at the other end. They are erected in the same manner as any other structural supporting member. Joist girders may have fall arrest equipment placed on them prior to hoisting and should be hoisted with two slings of adequate capacity and a set of spreaders. If conditions warrant, a tag line may be used to control the load until the connectors have control of the member. The top chord of joist girders should bear on the column caps and have two bolts per connection at each end of the joist girder. The lower chord is usually attached to the column in one of two ways: as a bolted seat connection or as a welded sta- bilizer plate. Once the deck and built-up roofing are installed (i.e., the dead load is applied), the bottom chord of the joist girder should be fully tensioned at the bot- tom chord shoe or fully welded at the stabilizer plate. Welding Requirements Since bar joists are made from lightweight materials, welding can damage them beyond repair. Always take special care when field welding joists and comply with all manufacturer recommendations and job specifications. Unit 7 — Installing Joists, Joist Girders, and Trusses 7.11 UNIT 7

▶▶OBJECTIVE 5: BRIDGING Bracing for bar joists, often called “bridging,” is used in conjunction with the erec- tion of bar joists. The two common types of bridging are lateral bridging (Figure 7.20) and cross bridging (Figure 7.21). Lateral bridging is when angle iron is placed in a horizontal position as specified on a structure’s drawings and welded to the top and bottom chord of the joist. In cross bridging (or “X-bridging”), the angle iron is fastened to the top chord of one joist and the bottom chord of the adjacent joist. Bridging is threaded through the webs of the joists, and makes a joist rigid. This rigidity is, however, dependent on the joists’ positioning and orientation: before placing bundles of bridging on bar joists, properly space the joists and fasten both ends. Always make sure that joists are straight up and down and straight from one to the other before welding bridging. Bridging requirements (such as number of rows needed) are given in the joist plan of a structure’s erection drawings, and bridging should always be placed according to manufacturer specifications. Figure 7.20 Lateral Bridging Figure 7.21 Cross Bridging 7.12 Structural Steel Erection UNIT 7

Terminating Bridging The ends of all bridging lines that termi- nate at walls or beams should be welded or bolted (see Figure 7.22) as specified. Bridging is not, however, welded to joist web members. Figures 7.23–7.26 show methods of ter- minating bridging for horizontal and cross bridging. Figure 7.24 illustrates bridging being ter- minated using anchors to fasten an angle clip to a wall and welding to fasten the bridging to the terminus. Note that in this case horizontal bridging should be used in the space adjacent to the wall to allow for proper deflection of the joist nearest the wall. Full depth cantilever ends must have cross bridging at the support (Figure 7.25). Square ends must have cross bridg- ing at the end (Figure 7.26). Figure 7.22 Ironworker Installing Bolted Bridging Figure 7.23 Termination for Horizontal Bridging Figure 7.24 Bridging Anchors Figure 7.26 Square End Figure 7.25 Full Depth Cantilever End Unit 7 — Installing Joists, Joist Girders, and Trusses 7.13 UNIT 7

▶▶OBJECTIVE 6: TRUSSES Trusses are similar to girders in that they are generally very large pieces of struc- tural steel that carry the loads of other structural steel members to columns. Some trusses join main trusses together to add support to and prevent the failure of the main trusses. A truss usually resembles a bar joist in appearance. However, trusses are typically much heavier than bar joists and are fabricated almost entirely out of structural shapes (including wide-flange beams, channels, plates, angles, square tube, etc.). Trusses also differ from bar joists in that they can be fabricated to conform to the shape of almost any roof system. This makes them more versatile than bar joists. Small trusses are fabricated in a shop. When shipping constraints are not an issue, sections of larger trusses are also fabricated in a shop and then transported to the job site. However, when ship- ping a large structural mem- ber is a concern, trusses are fabricated in the field, usu- ally close to the area where they will be erected. The same procedures and tools used to erect girders and beams are used to erect trusses. Figures 7.27–7.30 depict a truss being fab- ricated on site, raised up, erected, and then installed. Figure 7.27 Truss Being Assembled on Ground 7.14 Structural Steel Erection Figure 7.28 Truss Being Tilted Up on Ground UNIT 7

Figure 7.29 Two Cranes Used to Install a Truss Figure 7.30 Final Installation of Truss Unit 7 — Installing Joists, Joist Girders, and Trusses 7.15 UNIT 7

7.16 Structural Steel Erection UNIT 7

▶ PLUMBING AND ALIGNING STRUCTURAL STEEL UNIT 8 ▶ OBJECTIVES After completion of this unit, you should be able describe the processes involved in plumbing and aligning structural steel. This knowledge will be evidenced by cor- rectly completing the assignment sheet, performing the skills in the performance exercise assessment, and by scoring a minimum of 70% on the unit test. Specifically, you should be able to: 1. Explain how to plumb and align structural steel 2. Explain how to plumb and space bays to take into account weld shrinkage 3. Describe structural steel detailing Each of these objectives is covered in the pages that follow. Unit 8 — Plumbing and Aligning Structural Steel 8.1 UNIT 8

▶▶OBJECTIVE 1: PLUMBING AND ALIGNING STRUCTURAL STEEL After structural members are raised and temporarily connected, and before con- nections are completed, the structure must be plumbed to bring all of its parts into their correct positions and alignment. If members have been accurately fabricated and time has been taken to properly check and align the anchor bolts and shim to elevation, little adjustment will be required. If these measures have not been followed, and a structure is not plumb, however, serious problems may arise. The finished exterior of the building will not line up if the steel has not been properly aligned, nor will other materials attached to the steel structure. For example, in a structure where there are elevators that must move vertically, the equipment will not operate properly if the steel is out of alignment. Plumbing can start as soon as the raising gang erects the first elevation of columns and beams or a tier of columns and beams (as illustrated in Figure 8.1). When the first bay of iron has been erected and the raising gang starts erecting the second bay, the plumbing gang can begin plumbing the first bay. Plumbing should not, however, interfere with the work of the raising gang. Figure 8.1 Method for Plumbing a Skeleton Frame 8.2 Structural Steel Erection UNIT 8

Checking if a Column is Plumb The plumbness of a column can usually be checked with a plumb bob (Figure 8.2). This is the simplest plumbing tool, consisting as it does of a line with a brass weight on it. Gravity keeps the line vertical, so it can be used to check how truly vertical a structural member is. A plumb bob is suspended from the top of a col- umn so that the bob itself reaches to the ground and so that its line is a few inches from one face of the column. If the distance from that face of the column to the bob is the same at the top of the column as well as at the bottom, the plane of that face is vertical. But if the distance from the line to the face at the bottom of the column is not the same as at the top, the column is tipped and requires plumbing. To check the plumbness of a column in windy conditions, immerse the bob at the bottom of the column in a pail of light oil or water. This will help to protect the bob from air currents and vibration that might cause it to swing (at the very least it will swing much less than if it was freely suspended in the air). Many Ironworkers prefer to use a plumb bob because a length of string and a bob can be taken anywhere on a structure to check any part or point; however, laser instruments can be used in place of plumb bobs. One advantage of laser instru- ments is that wind does not affect the beam of light produced by a laser. While plumb bobs can be used for both short and extremely long distances (simply by using a longer line), lasers generally cannot be used for long distances. This is because the further the beam of light gets from the source of the laser, the larger and fainter the laser dot of light becomes. A transit or theodolite may also be used to check column alignment either with or without the use of offset targets (shiny reflective surfaces or bulls-eyes at which the lens is aimed). If targets are used, they can be clamped to the columns, magneti- cally attached to the columns, or held against the columns by hand. If targets are not used, check plumbness by first focusing the transit or theodolite eyepiece on the bottom portion of the column, then locking the base of the transit, and then swinging the eyepiece up to focus on the top of the column. Column alignment can also be checked by using a preset or imaginary offset build- ing line. This is accomplished by setting up the transit or theodolite along a column line, sighting both the first and farthest columns in the same line, and establishing the offset line. Lock the base of the instrument, allowing the vertical line on the Figure 8.2 Plumb Bob in Use Unit 8 — Plumbing and Aligning Structural Steel 8.3 UNIT 8

eyepiece to act as both the plumb bob and the offset building line. Take care to ensure that the columns at the first and last sighted points are on grid and that the offset at each is equal. The offset building line is transferred to more convenient upper levels as a job pro- gresses. Once a predetermined level of a structure has been erected, the offset building line is raised from the ground and re-established at the pre-determined level by weld- ing stub rods to the corner columns (as these new reference points are established, a plumb bob can be dropped from the rods to ensure that plumbness is maintained). Making a Column Plumb with Plumbing Cables Generally speaking, for the first twenty stories of a structure, the centerline of any exterior column can be displaced from the established column line no more than 1 inch toward (or 2 inches away from) the building line. These limits may be increased by 1/16\" for each additional story above the initial twenty, but may not exceed a total displacement of 2\" toward (or 3\" away from) the building line. This is known as the AISC L/500 rule. For more information, refer to the standard for plumbness of a structure set by the American Institute of Steel Construction, Inc. (AISC). Note: The above figures regarding displacement may vary depending on the job. If a column is found to be out of plumb, tensioning or loosening plumbing cables (guy cables) can be used to make it plumb. The following is a step-by-step guide to making a column plumb using plumbing cables: 1. 2. Make an eye in one end of the wire rope, if one is not already present. Place the wire rope around a column at the end of a line of columns, under the beam at the top of the tier to be plumbed. This is shown in Figure 8.3, detail A. The cable must be under the beam so that it will not interfere with the bolting and the impacting of the beam. 8.4 Structural Steel Erection Figure 8.3 Plumbing Cables Installed on a Structure UNIT 8

Note: Because all of the columns in any line are tied together by connecting beams, when the columns at the ends of the line are plumb, the intermediate columns in the line should also be plumb. However, any interior columns that must be absolutely vertical can be adjusted separately. 3. Take an extra round turn (i.e., an extra wrap around the column) to keep the plumb cable from sliding down the column. If the cable keeps trying to slide down the column, a piece of tie wire may be used to tie the cable up under the beam (as pressure is later applied to the cable, the tie wire will pull loose). 4. Attach the eye on the end of the cable to the running end by means of a shackle. 5. Work the cable back through the shackle until the cable becomes secure around the column. The top end of the plumb cable should now be secured. 6. Place a choker around the base of an adjacent column, taking a round turn (extra wrap around) before running one eye through the other as shown in Figure 8.3, D. 7. Once the choker is “choked” around the base of the second column, connect the turnbuckle to the choker by placing a shackle through the eye of the turnbuckle. If the turnbuckle has hooks instead of eyes, it may be hooked directly into the eye of the choker (a shackle isn’t needed), as shown in Figure 8.4. 8. Take the end of the plumbing cable leading to the top of the first column and run it through the remaining eye of the turnbuckle that is opposite the choker. Figure 8.4 Hooked Turnbuckle Used to Secure Plumbing Cables 9. Pull the dead end (the end running through the turnbuckle) back along the running end of the cable until all slack is removed from the cable. 10. Apply as much pull as possible and secure the cable together with cable clamps. This plumbing cable should now be secured. Unit 8 — Plumbing and Aligning Structural Steel 8.5 UNIT 8

11. Install a second plumbing cable by repeating steps 1–10 on the second column. This should form a cross (“X”) that will plumb, and maintain the plumb of, both columns. 12. Once the second line has been installed, tighten the turnbuckles to plumb both columns. 13. Leave the plumbing cables in place, and use new plumbing cables to repeat steps 1–12 on each parallel row of columns in succession. 14. After the columns are made plumb in each parallel row, repeat steps 1–12 for the columns in the perpendicular direction. In many cases, columns must be guyed two ways, especially at each corner, so that the structure can be pulled in either direction. When it has been determined how much the steel must be moved to make the structure plumb, the turnbuckles are tightened or loosened as needed. As one end of the turnbuckle is tightened or loos- ened by one Ironworker, the other end is kept from turning by another Ironworker (as in Figure 8.5). If bolts are used for the permanent connections, it will be necessary to place and tighten the bolts in all of the connections throughout the structure while the plumbing cables are still in position. Figure 8.5 Two Ironworkers Tightening a Plumb Cable 8.6 Structural Steel Erection UNIT 8

For welded structures, care must be taken when tightening plumbing cables to ensure approximately equal tension in both directions. If this care is not taken, the structure will tend to move towards the tightest cables during welding and the frame will be out of alignment. When plumbing structures in general, cable tension can be equalized by pulling the frame about 1⁄4\" past the proper alignment point in one direction and tightening the opposing cables just enough to pull the structure back in line. Figure 8.6 shows plumbing procedures used on a tier building. Figure 8.6 Plumbing Procedures Used on a Tier Building Caution! Follow these safety rules when plumbing structural steel: • Make sure plumbing cables are properly secured and that turnbuckles will not unwind while under stress. • Position plumbing cables so that other workers can safely access connection points. • Never remove plumbing cables without authorization. Unit 8 — Plumbing and Aligning Structural Steel 8.7 UNIT 8

▶▶OBJECTIVE 2: PLUMBING AND SPACING WELDED STRUCTURES While plumbing and spacing individual bays and overall dimensions of a structural steel frame to be welded, allowances must be made for shrinkage at the welded joint. Such allowances will vary depending on the size of the member being welded, the type of groove, the welding procedure, and the type of welding employed. Compensation for weld shrinkage can readily be accomplished as shown in Figure 8.7, B. The erector spaces (or “spreads”) each connection by an estimated average of 1/16\" for light framing pieces (heavier pieces require larger esti- mates). The shear welds are completed first, followed by the flange welds. If all is done accurately, the fin- ished frame will be square and dimensionally correct as shown in Figure 8.7, D. Figure 8.7 Compensation for Welding The method of spreading structural joints (Figure 8.8) is simple. Figure 8.8 Method of Spreading or Spacing Structural Joints – Column Spacing 8.8 Structural Steel Erection UNIT 8

The bay spacing needed is computed (before welding) by adding the shrinkage of the two connections to the desired finished spacing. Connections are then spaced by driving a tempered steel wedge into the top flange gap of the beam/girder between the column and beam/girder. When the desired spacing is obtained, the web of the beam/girder is tack welded, the wedges are removed, and the spacing crew moves onto the next bay. As a general rule, spacing begins with the center unit of the column line and pro- gresses outward towards the exterior columns. After spacing, but before welding, the center column should be plumb while all other columns may lean slightly away from the center column where the spacing was started. The sequence of welding the complete joints progresses in the same fashion – from the center joint towards the exterior columns – with the exterior bays being welded last. This allows for any additional variation in spacing needed to ensure close adherence to the structure’s overall required dimensions and to ensure minimum plumb error in the exterior columns. As an example, for the one-story warehouse-type structure depicted in Figure 8.9, the steel would be erected and then the spacing crew would start spacing the center column bays as shown in details D and E. Working out toward the exterior columns, spacing would be completed in bays “D,” “C,” and “B,” and then in bays “E,” “F,” and “G”. Exterior bays “A” and “H” would be left until all of the interior bays have been welded and measured to ensure that the estimated amount of shrinkage had taken place and that appropriate allowances had been made. If needed, minor variations in the estimated amount of shrinkage are corrected in the spacing of the end bays. Figure 8.9 One-Story Erection Unit 8 — Plumbing and Aligning Structural Steel 8.9 UNIT 8

▶▶OBJECTIVE 3: DETAILING STRUCTURAL STEEL Before, during, or after plumbing, structural steel is detailed. Detailing of structural steel should begin once enough steel has been erected and bolted up so that the work performed by the detailing crew does not interfere with the work being performed by any other gang. That being said, there may be instances where the detailing process may need to begin sooner, even if it cannot be completed, so that the erection of the building is not slowed due to an error or revision. Detailing involves, but is not necessarily limited to, the following: • • • • • • Rechecking of all drawings for revisions, mistakes, and items omitted Obtaining the correct spacing between columns where there is no beam Installing perimeter angles and also skylights or other roof openings Double checking bolted connections for proper tension, missing bolts, bolts of incorrect size, and any other deviations from the specifications Correcting deficiencies or punch list items noted by the controlling contractor Removing plumb lines and related hardware, and gathering materials to be returned to the steel erection contractor 8.10 Structural Steel Erection UNIT 8

▶ BOLTING UP OF STRUCTURAL STEEL UNIT 9 ▶ OBJECTIVES After completion of this unit, you should know how to bolt up structural steel. This knowledge will be evidenced by correctly completing the assignment sheet, performing the skills in the performance exercise assessments, and by scoring a minimum of 70% on the unit test. Specifically, you should be able to: 1. Identify the main types of bolts and accessories used in bolting up 2. Determine lengths of high-strength structural bolts 3. Define tension and torque 4. Describe the basic procedures for installing bolts 5. Describe the four methods used to tension bolts 6. Describe preinstallation verification testing procedures 7. Describe the four methods of inspecting bolts Each of these objectives is covered in the pages that follow. Unit 9 — Bolting Up of Structural Steel 9.1 UNIT 9

▶▶OBJECTIVE 1: BOLTS AND ACCESSORIES Bolting (or bolting up) has become the primary means of connecting steel struc- tures. Bolting includes all of the activities surrounding the receiving of bolts, nuts, flat washers, and direct tension indicating washers on the job site, as well as storing them, retrieving them for installation, and installing them in iron. Figure 9.1 depicts the basic parts of a bolt and the basic bolt accesso- ries that make up a bolt assembly. To conduct bolting up success- fully, Ironworkers must know how to recognize different types of bolts and different types of accessories, including erection bolts, high-strength bolts, TC bolts, galvanized bolts, self-locking nuts, DTI washers, and bevel washers. Erection Bolts Machine bolts, or erection bolts (Figure 9.2), used to be used to temporarily con- nect structural members. Later, the bolting up crew would replace them with rivets or high-strength bolts. This is now considered a safety hazard and is not allowed. Today connectors are required to use the bolts called for in the erection drawings. Erection bolts are often used in shop environments to ship multiple assemblies to a site; in this case, they are also replaced once the assembly is placed in a structure. Figure 9.2 Machine Bolts Figure 9.1 Basic Parts of a Bolt and Basic Accessories 9.2 Structural Steel Erection UNIT 9

Standard erection bolts are black or plated with American Standard threads and American Standard heads and nuts; black erection bolts are the most commonly used erection bolts on structural job sites. These bolts usually have a fully threaded shank and are available in various diameters and lengths. Erection bolts are often called soft bolts because they are “softer” than (i.e., not as strong as) the high-strength fasteners used to complete the bolting process in steel erection. They will not withstand the same torsional or tensile (see Objective 2) loads that high-strength bolts will endure without failure. Erection bolts also have different head and nut sizes than high-strength bolts of the same diameter have. For example, a 3⁄4\" erection bolt has a nut and bolt head size of 11/8\" while a 3⁄4\" hard (or high-strength) bolt has a nut and bolt head size of 11⁄4\". This allows an experienced journeyman Ironworker to distinguish easily between a “hard” or “soft” nut or bolt without having to look at the individual head or nut markings. High-Strength Bolts The two basic types of high-strength bolts are those specified under ASTM designa- tions A325 and A490. Both A325 and A490 fasteners are heavy hex structural bolts, used with heavy hex nuts. The threaded sections of the shanks of these types of bolts are standard for a given diameter (e.g., 3⁄4\" diameter bolts have a threaded section 13/8\" long). This allows an experienced Ironworker to gauge the length of the bolt by sight as the unthreaded shank lengths increase as the bolt lengths increase. The two basic types of high-strength bolts, their common dimensions, and their accessories are illustrated in Figure 9.3 and Table 9.1. This information was taken from specifications determined by the Research Council on Structural Connections. Note: Since erection nuts and bolt heads are smaller than their high- strength counterparts, a “hard” spud wrench will not fully engage them. Unit 9 — Bolting Up of Structural Steel 9.3 UNIT 9

Figure 9.3 Identification and Designation of High-Strength Bolts and Washers Nominal Bolt Size, D Bolt Dimensions, in Inches Nut Dimensions, in Inches Heavy Hex Structural Bolts Heavy Hex Bolts Width Across Flats F Height, H Thread Length Width Across Flats W Height, H 1⁄2 7⁄8 5/16 11⁄4 7⁄8 31/64 5/8 11/16 25/64 13/8 11/16 39/64 3⁄4 11⁄4 15/32 11⁄2 11⁄4 47/64 7⁄8 17/16 35/64 13⁄4 17/16 55/64 1 15/8 39/64 2 15/8 63/64 11/8 113/16 11/16 2 113/16 17/64 11⁄4 2 25/32 21⁄4 2 17/32 13/8 23/16 27/32 21⁄4 23/16 111/32 11⁄2 23/8 15/16 11⁄4 23/8 115/32 Table 9.1 High-Strength Bolt Dimensions All high-strength bolts are heat-treated by quenching and tempering. Type 1 A325 bolts are produced from medium-carbon steel, while Type 3 A325 bolts are pro- duced from steel with weathering characteristics. Weathering bolts are used in applications where weathering steel is the primary structural makeup (e.g., tub girders on bridges). These steel structures and bolts are designed to be installed and left unpainted. Over time, the steel and bolts “weather” or oxidize to produce a protective finish that looks much the same as a rusty coating. 9.4 Structural Steel Erection 5 2 5 2 3 5 3 A A 2 3 A 0 4 9 A UNIT 9

As Figure 9.3 illustrates, high-strength bolts, nuts, and washers are marked to iden- tify the grade of steel used to create them. Type 1 A325 bolts are marked on the top of the head with “A325,” the manufacturer’s mark, and (at the manufacturer’s option) three radial lines 120° apart. Type 3 A325 bolts have markings that include “A325” underlined, the manufacturer’s mark, and (at the manufacturer’s option) a weathering symbol. A490 bolts have “A490” and the manufacturer’s mark on the head; a weathering symbol may also be included for Type 3 A490 bolts. Type 1 A325 heavy hex nuts are distinguished by three circumferential marks, and by alternate nut markings of “D” or “DH” or the manufacturer’s symbol together with either “2” or “2H.” Heavy hex nuts for Type 3 A325 bolts are marked on one face with the number 3, three circumferential lines, and at the manufacturer’s option, a weathering symbol. A490 nuts are marked with “DH,” or with the manu- facturer’s symbol and “2H.” Washers are identified by similar stamped markings. The main difference between A325 and A490 bolts is the amount of tensile strength they can withstand prior to failure. Tensile strength will be discussed more thor- oughly in Objective 2, but the different tensile strengths of ASTM A325 and A490 bolts are listed in Table 9.2. Bolt A325 A490 A325M (Metric) A490M (Metric) Maximum tensile strength based on bolt size 1⁄2\" to 1\" (inclusive) = 120,000 psi 1⁄2\" to 1 1⁄2\" = 150,000 psi min- imum/ 173,000 psi max- imum M12 to M36 = 830 MPa M12 to M36 = 1040 MPa minimum/1210 MPa maximum Note: For instances where a direct conversion of metric tensile strengths for imperial bolts is needed, 1 MPa =145 psi = 10.2 kg/cm2. The metric versions of the ASTM standards are not exact equivalents of the imperial versions, however; the diameters do not correspond exactly and the tensile strengths are rounded to the nearest 10 MPa. Over 1\" = 105,000 psi Table 9.2 Maximum Tensile Strengths of ASTM A325 and A490 Bolts Although it is not recommended, A325 and A490 fastener assembly mixes can sub- stitute for assemblies that are made completely of A325 components. Such mixes cannot, however, be used in places that call for A490 assemblies. Unit 9 — Bolting Up of Structural Steel 9.5 UNIT 9

F1852 Twist-Off Tension Control (TC) Bolts Twist-off tension control bolts (see Figure 9.4) are commonly called “TC bolts,” and are widely used to connect steel. Most manufacturers produce a rivet (or button-type) head for TC bolts, and the shank of the bolt differs from standard A325 and A490 bolts in that it has a splined section on the end. This splined section reduces the diameter of the shank, and is manufactured to shear (or twist) off when the bolt has been tightened properly. This means that an Ironworker can tighten the bolt without having to hold its head to prevent it from “rolling” (i.e., turning unintentionally). TC bolt head markings are similar to those on A325 and A490 bolts. Advantages of TC bolts include automatic torque control, one-sided and one- person installation, easy visual inspection, and no tool calibration or air compressor needs. A disadvantage of TC bolts, however, is that the spline can shear off prematurely. This usually happens for one of three reasons: 1. rust (likely due to improper bolt storage) or lack of lubrication 2. damaged threads 3. poor fit up and trying to use a TC bolt to draw up a connection It is also possible that a bolt spline will shear off and the bolt will become loose after the other bolts in the connection are tensioned (tightened). This can occur in any connection with a large quantity of bolts, but it is a particular problem with TC bolts because once a TC bolt’s spline is sheared off, the bolt cannot be tightened fur- ther. To prevent this problem, an Ironworker should use a TC gun to snug tighten (make so that all plies of steel in a connection have been drawn together) all bolts before tensioning any bolts in a connection. TC bolts come from the manufacturer fully assembled and lubricated. Since a TC bolt’s spline twists off at a specific torque value, re-lubrication of dry bolts is not allowed. If lack of lubrication is a problem, the bolts must be returned to the manu- facturer. Figure 9.4 TC Bolt 9.6 Structural Steel Erection UNIT 9

If bolts are rusty or have damaged threads, they must be replaced. If poor fit up is a concern, use regular hex head fasteners to draw up a connection and then replace the hex head fasteners with the required TC fasteners. Galvanized Bolts Both regular hex-head bolts and (less commonly) TC bolts can be galvanized; if the structural steel to be used on a job site is galvanized, the bolts used should be gal- vanized, too. If a structure is to be placed in or near conditions that are corrosive or that might accelerate oxidation, the steel used for the structure may be galvanized. There are two methods of galvanizing bolts: hot-dipped galvanizing (HDG) and mechanical galvanizing (MG). HDG bolts and nuts are made by over-tapping or over-cutting bolts and nuts (i.e., making their threads deeper). These components are then “dipped” and “soaked” in a galvanizing coating until the coat achieves proper thickness. HDG bolts, nuts, and washers are easily identified by their dull finish and somewhat “rough” texture. MG fastener components have a thinner galvanizing coating applied by mechanical methods, so they are not over-tapped or over-cut. They can be identified by their luster; they are usually somewhat “shiny” in appearance. Some manufacturers help identify between HDG and MG fasteners by adding dye to the lubricant; when this happens, the galvanized nuts appear to be colored. One manufacturer may dye HDG nuts blue and MG nuts green or pink. Another manu- facturer may use a different color combination (dyeing, for example, HDG nuts green and MG nuts blue). The mixing of HDG and MG nuts and bolts (using an MG bolt with an HDG nut, for example) typically causes the nuts to “seize,” to become bound up and incapable of being tightened or loosened. Mixing galvanized fasteners can also cause thread galling (damage due to torsion or friction). Since seizing almost always occurs with the mixing of different types of galvanized fastener assemblies, the Research Council on Structural Connections prohibits such mixing. Both the mixing of plain (uncoated) and galvanized fastener components and the mixing of HDG and MG bolts and nuts are prohibited. Always check packing slips, bills of lading, and material test reports (MTRs) that accompany fastener assem- blies to ensure that assembly components do not get mixed or mismatched. All galvanized A325 bolts and accessories must be shipped and stored in the same container, and all galvanized A325 bolts require an assembly test. Unit 9 — Bolting Up of Structural Steel 9.7 UNIT 9

Note: Neither a bolt’s proof load nor its tensile strength is affected by the galvanizing process; however, bolt tension relaxation for galvanized connections is related to the thickness of the galvanized coating, and is generally about twice that of non-galvanized bolts and connections. Self-Locking Nuts Self-locking nuts (Figure 9.5) are approved for use with high-strength bolts. They provide simple, quick, and positive locking action for any applica- tion where shock or vibration is a problem. They are also ideal for applications where power tools cannot be used efficiently (such as towers), or in locations where adequate bolt tension cannot be obtained. Self-locking nuts have a steel locking pin set in the nut that acts as a ratchet, sliding along the thread as the nut is tightened. The point on the pin in contact with the bolt thread prevents the nut from loosen- ing under shock or vibration. The direction of the pin can be reversed with a hand wrench, allowing for easy removal and potential reuse of the nut and/ or bolt. Direct-Tension Indicating (DTI) Washers Figure 9.5 ANCO Self- Locking Nut A Direct-Tension Indicating Washer (DTI), sometimes called a Load Indicating Washer (LIW), is a hardened round washer that has a group of protrusions pressed out of its flat surface (Figure 9.6). A DTI is placed on a bolt with the protrusions against either the bolt head or nut; if, however, the DTI is placed under the turned element (the nut, for example), a regular washer must be placed between the turned element and the DTI. As the bolt is tightened, the bolt clamping forces cause the DTI’s protrusions to partially flatten, closing the gap between the DTI and the bolt. The number and size of the protrusions determine load capacity, and are varied based on the diameter and grade of the bolt intended for the washer. The type of bolt for which a DTI should be used (whether A325 or A490, for example) should be clearly marked on the DTI. 9.8 Structural Steel Erection Figure 9.6 DTI UNIT 9

Some DTI protrusions are filled with epoxy. When a bolt is tightened and the protrusions flatten, this epoxy seeps out and is apparent through a visual check, as can be seen in Figure 9.7. This type of DTI is commonly referred to as a “squirter DTI.” Squirter DTIs make a feeler gauge check (see Objective 5) unnecessary. Figure 9.7 Installed Squirter DTIs After Tensioning Bevel Washers Used in High Strength-Bolting Bevel washers provide a “square” seat for the bolt head or the nut when a bolt passes through a beam or channel flange that has a sloping inner face. When used, bevel washers replace the round washers ordinarily used in high- strength bolting. Bevel washers must be used with American standard beams and channels with a 1-in-6 (16 2/3%) flange slope, as illustrated in Figure 9.8. For installations where clearances are less than standard, some companies furnish clipped round washers and bevel washers clipped on the thin side of the bevel. Storage, Re-lubrication, and Reuse Bolt storage conditions must be controlled to keep the hardware as close to new and as unweathered as possible. Tests have shown that once removed from “protected storage” (i.e., from their sealed kegs and Connex storage container), bolts can dry out in as little as a few days to the point where it takes 1,000 ft./lb. of effort to install them rather than the 500 ft./lb. of effort required when they were manufactured. Figure 9.9 shows an Ironworker and an apprentice removing bolts for a day’s use. At the end of each day, bolts should be returned to their respective kegs and placed back into the Connex storage container. Figure 9.8 American Standard Beam or Channel with 162⁄3 Percent Slope Figure 9.9 An Ironworker and an Apprentice Removing Bolts for the Day Unit 9 — Bolting Up of Structural Steel 9.9 UNIT 9

Always try to use dry Connex storage containers to store all bolt hardware. Do not use a tarp to cover unsealed kegs; condensation under the tarp may rust bolts in just a few days. Salty air, desert heat, blowing dust, rain, and moisture can also accelerate bolt rusting. If re-lubrication of bolts is necessary, follow the manufacturer’s specifications, keep- ing in mind that over-lubricating with superlubricants, such as molysidulphide, can cause inadvertent thread stripping and that re-lubrication is not permitted for F1852 TC bolts (they must be returned to the manufacturer if re-lubrication is necessary). Re-lubrication does not have an adverse effect on most installations, including turn-of-the nut and DTI installation (see Objective 5), but preinstallation verifica- tion testing (see Objective 6) must be re-done for calibrated wrench installation to establish the necessary torque involved in properly tensioning an entire set of re-lubricated assemblies. This must be done each time re-lubrication takes place. A490 and galvanized bolts should never be reused. Ungalvanized A325 bolts, how- ever, may be reused if no permanent elongation of threads has occurred. If, after assembling a nut on a bolt, the nut runs freely the full length of the threads, an ungalvanized A325 bolt can be reused. Tip: Lids can get mixed up easily, so ensure that each bolt container’s label is on the side of the container and not on the lid. 9.10 Structural Steel Erection UNIT 9

▶▶OBJECTIVE 2: BOLT LENGTHS A bolt list specifying type and length of bolts needed to complete a structure should be supplied for each project; occasionally, however, errors arise in this list. In order to catch and prevent bolt installation errors, an Ironworker should know how to tell what bolt lengths are needed. A needed bolt length can be calculated by using this formula: Length of Bolt = Thickness of Metal (grip) + Bolt Diameter + 1⁄4\" + Thickness of Washer (if used) Minimum grip length can be determined by calculating the distance from the underside of the bolt head or the washer(s) at the end to a point 1/16\" on the nut side of the bolt thread run out (the portion of the bolt that has no threads). Following this calculation assures that the nut will not enter the thread run out, even if the washer or washers at the nut end are omitted. When a single bevel washer is substituted for the single flat washer in the length of bolt calculation formula, 1/8\" must be added to the grip length. When more than one flat washer is used, add 3/16\" to the grip length for each additional washer. When a bevel washer is used with a flat washer, add 5/16\" to the grip length. For quick reference, bolt lengths based on this formula and the use of regular washers are provided in Tables 9.3–9.5, which start on the next page. Table 9.6 provides another means of calculating bolt length. All of these tables are based on information provided in the Steel Structures Technology Center’s Structural Bolting Handbook (2006). Caution! When calculating bolt length, remember that the threads of a bolt must be excluded from the shear plane of any connection. Unit 9 — Bolting Up of Structural Steel 9.11 UNIT 9

Suggested Bolt Lengths for 3⁄4” Diameter A325, F1852, A490, and F2280 Bolts Grip No Washer One Washer Two Washers 0 11⁄2* 11⁄2* 11⁄2 1/16 11⁄2* 11⁄2* 11⁄2 1/8 11⁄2* 11⁄2* 11⁄2 3/16 11⁄2* 11⁄2 11⁄2 1⁄4 11⁄2* 11⁄2 13⁄4 5/16 11⁄2 11⁄2 13⁄4 3/8 11⁄2 11⁄2 13⁄4 7/16 11⁄2 13⁄4 13⁄4 1⁄2 11⁄2 13⁄4 2 9/16 13⁄4 13⁄4 2 5/8 13⁄4 13⁄4 2 11/16 13⁄4 2 2 3⁄4 13⁄4 2 21⁄4 13/16 2 2 21⁄4 7⁄8 2 2 21⁄4 15/16 2 21⁄4 21⁄4 1 2 21⁄4 21⁄2 11/16 21⁄4 21⁄4 21⁄2 11/8 21⁄4 21⁄4 21⁄2 13/16 21⁄4 21⁄2 21⁄2 11⁄4 21⁄4 21⁄2 23⁄4 15/16 21⁄2 21⁄2 23⁄4 13/8 21⁄2 21⁄2 23⁄4 17/16 21⁄2 23⁄4 23⁄4 11⁄2 21⁄2 23⁄4 3 19/16 23⁄4 23⁄4 3 15/8 23⁄4 23⁄4 3 111/16 23⁄4 3 31⁄4 13⁄4 23⁄4 3 31⁄4 113/16 3 3 31⁄4 17⁄8 3 31⁄4 31⁄4 115/16 3 31⁄4 31⁄2 2 3 31⁄4 31⁄2 21/16 31⁄4 31⁄4 31⁄2 Table 9.3 Suggested Bolt Lengths – 3⁄4\" Diameter Bolts 9.12 Structural Steel Erection UNIT 9

Suggested Bolt Lengths for 3⁄4” Diameter A325, F1852, A490, and F2280 Bolts Grip No Washer One Washer Two Washers 21/8 31⁄4 31⁄4 31⁄2 23/16 31⁄4 31⁄2 31⁄2 21⁄4 31⁄4 31⁄2 33⁄4 25/16 31⁄2 31⁄2 33⁄4 23/8 31⁄2 31⁄2 33⁄4 27/16 31⁄2 33⁄4 33⁄4 21⁄2 31⁄2 33⁄4 4 29/16 33⁄4 33⁄4 4 25/8 33⁄4 33⁄4 4 211/16 33⁄4 4 4 23⁄4 33⁄4 4 41⁄4 213/16 4 4 41⁄4 27⁄8 4 41⁄4 41⁄4 215/16 4 41⁄4 41⁄4 3 41⁄4 41⁄4 41⁄2 31/16 41⁄4 41⁄4 41⁄2 31/8 41⁄4 41⁄4 41⁄2 33/16 41⁄4 41⁄2 41⁄2 31⁄4 41⁄4 41⁄2 43⁄4 35/16 41⁄2 41⁄2 43⁄4 33/8 41⁄2 41⁄2 43⁄4 37/16 41⁄2 43⁄4 43⁄4 31⁄2 41⁄2 43⁄4 5 39/16 43⁄4 43⁄4 5 35/8 43⁄4 43⁄4 5 311/16 43⁄4 5 5 33⁄4 43⁄4 5 51⁄2* 313/16 5 5 51⁄2* 37⁄8 5 5 51⁄2* 315/16 5 51⁄2* 51⁄2 4 5 51⁄2* 51⁄2 41/16 51⁄2* 51⁄2 51⁄2 41/8 51⁄2* 51⁄2 51⁄2 43/16 51⁄2 51⁄2 51⁄2 Table 9.3 (cont.) Suggested Bolt Lengths – 3⁄4\" Diameter Bolts Unit 9 — Bolting Up of Structural Steel 9.13 UNIT 9

Suggested Bolt Lengths for 3⁄4” Diameter A325, F1852, A490, and F2280 Bolts Grip No Washer One Washer Two Washers 41⁄4 51⁄2 51⁄2 6* 45/16 51⁄2 51⁄2 6* 43/8 51⁄2 51⁄2 6* 47/16 51⁄2 6* 6 41⁄2 51⁄2 6* 6 49/16 6* 6 6 45/8 6* 6 6 411/16 6 6 6 43⁄4 6 6 61⁄2* 413/16 6 6 61⁄2* 47⁄8 6 6 61⁄2* 415/16 6 61⁄2* 61⁄2 5 6 61⁄2* 61⁄2 51/16 61⁄2* 61⁄2 61⁄2 51/8 61⁄2* 61⁄2 61⁄2 53/16 61⁄2 61⁄2 61⁄2 51⁄4 61⁄2 61⁄2 7* 55/16 61⁄2 61⁄2 7* 53/8 61⁄2 61⁄2 7* 57/16 61⁄2 7* 7 51⁄2 61⁄2 7* 7 59/16 7* 7 7 55/8 7* 7 7 511/16 7 7 7 53⁄4 7 7 71⁄2* 513/16 7 7 71⁄2* 57⁄8 7 7 71⁄2* 515/16 7 71⁄2* 71⁄2 For grips of 6\" and over, use bolt length pattern similar to 5\" pattern *Additional F436 washers may be required Table 9.3 (cont.) Suggested Bolt Lengths – 3⁄4\" Diameter Bolts 9.14 Structural Steel Erection UNIT 9

Suggested Bolt Lengths for 7/8\" Diameter A325, F1852, A490, and F2280 Bolts Grip No Washer One Washer Two Washers 0 13⁄4* 13⁄4* 13⁄4* 1/16 13⁄4* 13⁄4* 13⁄4* 1/8 13⁄4* 13⁄4* 13⁄4 3/16 13⁄4* 13⁄4* 13⁄4 1⁄4 13⁄4* 13⁄4* 13⁄4 5/16 13⁄4* 13⁄4 13⁄4 3/8 13⁄4* 13⁄4 2 7/16 13⁄4 13⁄4 2 1⁄2 13⁄4 13⁄4 2 9/16 13⁄4 2 2 5/8 13⁄4 2 21⁄4 11/16 2 2 21⁄4 3⁄4 2 2 21⁄4 13/16 2 21⁄4 21⁄4 7⁄8 2 21⁄4 21⁄2 15/16 21⁄4 21⁄4 21⁄2 1 21⁄4 21⁄4 21⁄2 11/16 21⁄4 21⁄2 21⁄2 11/8 21⁄4 21⁄2 23⁄4 13/16 21⁄2 21⁄2 23⁄4 11⁄4 21⁄2 21⁄2 23⁄4 15/16 21⁄2 23⁄4 23⁄4 13/8 21⁄2 23⁄4 3 17/16 23⁄4 23⁄4 3 11⁄2 23⁄4 23⁄4 3 19/16 23⁄4 3 3 15/8 23⁄4 3 31⁄4 111/16 3 3 31⁄4 13⁄4 3 3 31⁄4 113/16 3 31⁄4 31⁄4 17⁄8 3 31⁄4 31⁄2 115/16 31⁄4 31⁄4 31⁄2 2 31⁄4 31⁄4 31⁄2 21/16 31⁄4 31⁄2 31⁄2 Table 9.4 Suggested Bolt Lengths – 7⁄8\" Diameter Bolts Unit 9 — Bolting Up of Structural Steel 9.15 UNIT 9

Suggested Bolt Lengths for 7/8\" Diameter A325, F1852, A490, and F2280 Bolts Grip No Washer One Washer Two Washers 21/8 31⁄4 31⁄2 33⁄4 23/16 31⁄2 31⁄2 33⁄4 21⁄4 31⁄2 31⁄2 33⁄4 25/16 31⁄2 33⁄4 33⁄4 23/8 31⁄2 33⁄4 4 27/16 33⁄4 33⁄4 4 21⁄2 33⁄4 33⁄4 4 29/16 33⁄4 4 4 25/8 33⁄4 4 41⁄4 211/16 4 4 41⁄4 23⁄4 4 4 41⁄4 213/16 4 41⁄4 41⁄4 27⁄8 4 41⁄4 41⁄2 215/16 41⁄4 41⁄4 41⁄2 3 41⁄4 41⁄4 41⁄2 31/16 41⁄4 41⁄2 41⁄2 31/8 41⁄4 41⁄2 43⁄4 33/16 41⁄2 41⁄2 43⁄4 31⁄4 41⁄2 41⁄2 43⁄4 35/16 41⁄2 43⁄4 43⁄4 33/8 41⁄2 43⁄4 5 37/16 43⁄4 43⁄4 5 31⁄2 43⁄4 43⁄4 5 39/16 43⁄4 5 5 35/8 43⁄4 5 51⁄2* 311/16 5 5 51⁄2* 33⁄4 5 5 51⁄2* 313/16 5 51⁄2* 51⁄2 37⁄8 5 51⁄2* 51⁄2 315/16 51⁄2* 51⁄2 51⁄2 4 51⁄2* 51⁄2 51⁄2 41/16 51⁄2 51⁄2 51⁄2 41/8 51⁄2 51⁄2 6* 43/16 51⁄2 51⁄2 6* Table 9.4 (cont.) Suggested Bolt Lengths – 7⁄8\" Diameter Bolts 9.16 Structural Steel Erection UNIT 9

Suggested Bolt Lengths for 7/8\" Diameter A325, F1852, A490, and F2280 Bolts Grip No Washer One Washer Two Washers 41⁄4 51⁄2 51⁄2 6* 45/16 51⁄2 6* 6 43/8 51⁄2 6* 6 47/16 6* 6 6 41⁄2 6* 6 6 49/16 6 6 6 45/8 6 6 61⁄2* 411/16 6 6 61⁄2* 43⁄4 6 6 61⁄2* 413/16 6 61⁄2* 61⁄2 47⁄8 6 61⁄2* 61⁄2 415/16 61⁄2* 61⁄2* 61⁄2 5 61⁄2* 61⁄2 61⁄2 51/16 61⁄2 61⁄2 61⁄2 51/8 61⁄2 61⁄2 7* 53/16 61⁄2 61⁄2 7* 51⁄4 61⁄2 61⁄2 7* 55/16 61⁄2 7* 7 53/8 61⁄2 7* 7 57/16 7* 7 7 51⁄2 7* 7 7 59/16 7 7 7 55/8 7 7 71⁄2* 511/16 7 7 71⁄2* 53⁄4 7 7 71⁄2* 513/16 7 71⁄2* 71⁄2 57⁄8 7 71⁄2* 71⁄2 515/16 71⁄2* 71⁄2 71⁄2 For grips of 6\" and over, use bolt length pattern similar to 5\" pattern *Additional F436 washers may be required Table 9.4 (cont.) Suggested Bolt Lengths – 7⁄8\" Diameter Bolts Unit 9 — Bolting Up of Structural Steel 9.17 UNIT 9

Suggested Bolt Lengths for 1\" Diameter A325, F1852, A490, and F2280 Bolts Grip No Washer One Washer Two Washers 0 13⁄4* 13⁄4 13⁄4 1/16 13⁄4* 13⁄4 13⁄4 1/8 13⁄4 13⁄4 13⁄4 3/16 13⁄4 13⁄4 13⁄4 1⁄4 13⁄4 13⁄4 2 5/16 13⁄4 13⁄4 2 3/8 13⁄4 13⁄4 2 7/16 13⁄4 2 2 1⁄2 13⁄4 2 21⁄4 9/16 2 2 21⁄4 5/8 2 2 21⁄4 11/16 2 21⁄4 21⁄4 3⁄4 2 21⁄4 21⁄2 13/16 21⁄4 21⁄4 21⁄2 7⁄8 21⁄4 21⁄4 21⁄2 15/16 21⁄4 21⁄2 21⁄2 1 21⁄4 21⁄2 23⁄4 11/16 21⁄2 21⁄2 23⁄4 11/8 21⁄2 21⁄2 23⁄4 13/16 21⁄2 23⁄4 23⁄4 11⁄4 21⁄2 23⁄4 3 15/16 23⁄4 23⁄4 3 13/8 23⁄4 23⁄4 3 17/16 23⁄4 3 3 11⁄2 23⁄4 3 31⁄4 19/16 3 3 31⁄4 15/8 3 3 31⁄4 111/16 3 31⁄4 31⁄4 13⁄4 3 31⁄4 31⁄2 113/16 31⁄4 31⁄4 31⁄2 17⁄8 31⁄4 31⁄4 31⁄2 115/16 31⁄4 31⁄2 31⁄2 2 31⁄4 31⁄2 33⁄4 21/16 31⁄2 31⁄2 33⁄4 Table 9.5 Suggested Bolt Lengths – 1\" Diameter Bolts 9.18 Structural Steel Erection UNIT 9

Suggested Bolt Lengths for 1\" Diameter A325, F1852, A490, and F2280 Bolts Grip No Washer One Washer Two Washers 21/8 31⁄2 31⁄2 33⁄4 23/16 31⁄2 33⁄4 33⁄4 21⁄4 31⁄2 33⁄4 4 25/16 33⁄4 33⁄4 4 23/8 33⁄4 33⁄4 4 27/16 33⁄4 4 4 21⁄2 33⁄4 4 41⁄4 29/16 4 4 41⁄4 25/8 4 4 41⁄4 211/16 4 41⁄4 41⁄4 23⁄4 4 41⁄4 41⁄2 213/16 41⁄4 41⁄4 41⁄2 27⁄8 41⁄4 41⁄4 41⁄2 215/16 41⁄4 41⁄2 41⁄2 3 41⁄4 41⁄2 43⁄4 31/16 41⁄2 41⁄2 43⁄4 31/8 41⁄2 41⁄2 43⁄4 33/16 41⁄2 43⁄4 43⁄4 31⁄4 41⁄2 43⁄4 5 35/16 43⁄4 43⁄4 5 33/8 43⁄4 43⁄4 5 37/16 43⁄4 5 5 31⁄2 43⁄4 5 51⁄2* 39/16 5 5 51⁄2 35/8 5 5 51⁄2 311/16 5 51⁄2 51⁄2 33⁄4 5 51⁄2 51⁄2 313/16 51⁄2 51⁄2 51⁄2 37⁄8 51⁄2 51⁄2 51⁄2 315/16 51⁄2 51⁄2 51⁄2 4 51⁄2 51⁄2 6* 41/16 51⁄2 51⁄2 6 41/8 51⁄2 51⁄2 6 43/16 51⁄2 6 6 Table 9.5 (cont.) Suggested Bolt Lengths – 1\" Diameter Bolts Unit 9 — Bolting Up of Structural Steel 9.19 UNIT 9

Suggested Bolt Lengths for 1\" Diameter A325, F1852, A490, and F2280 Bolts Grip No Washer One Washer Two Washers 41⁄4 51⁄2 6 6 45/16 6 6 6 43/8 6 6 6 47/16 6 6 6 41⁄2 6 6 61⁄2* 49/16 6 6 61⁄2 45/8 6 6 61⁄2 411/16 6 61⁄2 61⁄2 43⁄4 6 61⁄2 61⁄2 413/16 61⁄2 61⁄2 61⁄2 47⁄8 61⁄2 61⁄2 61⁄2 415/16 61⁄2 61⁄2 61⁄2 5 61⁄2 61⁄2 7* 51/16 61⁄2 61⁄2 7 51/8 61⁄2 61⁄2 7 53/16 61⁄2 7 7 51⁄4 61⁄2 7 7 55/16 7 7 7 53/8 7 7 7 57/16 7 7 7 51⁄2 7 7 71⁄2* 59/16 7 7 71⁄2 55/8 7 7 71⁄2 511/16 7 71⁄2 71⁄2 53⁄4 7 71⁄2 71⁄2 513/16 71⁄2 71⁄2 71⁄2 57⁄8 71⁄2 71⁄2 71⁄2 515/16 71⁄2 71⁄2 71⁄2 For grips of 6\" and over, use bolt length pattern similar to 5\" pattern *Additional F436 washers may be required Table 9.5 (cont.) Suggested Bolt Lengths – 1\" Diameter Bolts 9.20 Structural Steel Erection UNIT 9

Estimating Bolt Lengths (for A325, F1852, A490, and F2280 Bolts) If the bolt diam- eter is this in inches . . . Add this amount to the grip (round up to the next bolt length) for no washers Add this amount to the grip (round up to the next bolt length) for one washer Add this amount to the grip (round up to the next bolt length) for two washers 1⁄2 11/16 27/32 1 5/8 7⁄8 11/32 13/16 3⁄4 1 15/32 15/16 7⁄8 11/8 19/32 17/16 1 11⁄4 113/32 19/16 11/8 11⁄2 121/32 113/16 11⁄4 15/8 125/32 115/16 13/8 13⁄4 129/32 21/16 11⁄2 17⁄8 21/32 23/16 Table 9.6 Estimating Bolt Lengths In general, the use of longer-than-needed bolts should be avoided. Longer bolts tend to be more expensive than shorter bolts, and using bolts of the proper length initially also prevents having to replace bolts later (such replacement can be both time-consuming and costly). Although it is commonly considered acceptable for two or three threads (or 1⁄4\") of a bolt to stick out of a connection, as long as a fully tensioned bolt has a nut with full thread engagement, the bolt will perform as required. Note: The amount of bolt that sticks out (or projects) from a con- nection is generally a cosmetic choice; however, maintaining a consistent level of projection throughout a connection is considered good craftsmanship. Unit 9 — Bolting Up of Structural Steel 9.21 UNIT 9

▶▶OBJECTIVE 3: TENSION AND TORQUE Structurally, a bolt serves one of two purposes: 1. It can act as a pin to keep two or more plies of a steel joint from slipping relative to each other. If a slip occurs, the plies put the bolt in shear, a force that tends to cut the bolt in two like a pair of scissors. 2. It can act as a heavy spring to clamp the plies of steel together. If this is done correctly, slip of the plies is prevented. In the vast majority of applications, a bolt is used as a clamp. When we tighten a bolt – usually by turning the nut or occasionally by turning the head – we stretch the bolt just a little bit. This stretch is the result of a stress called tension, a force which pulls materials apart. It is also what mobilizes the clamping force that holds the plies together. If there is no stretch, there is no clamping force. Tension is in opposition to, and equal in load to, compression, a force that pulls, or squeezes, materials together. The stretch of the bolt is resisted by compressive strain in the connected plies of steel. The action of tightening a bolt also causes a twist in the bolt, referred to as torsion, and it is this torsional stress, which if large enough, can reduce the capacity of the bolt to be stretched. In other words, a bolt can be broken before it is fully tensioned because it breaks as a result of “twist,” or torsion. Torque and Tensile Strength Torque is the force used to turn a nut to spin it up a bolt’s threads. Although tighten- ing a bolt can be called either “torqueing up” or “tensioning” the bolt, tension is the primary factor in bolt installation as it is the force that a bolt exerts upon a connec- tion (as a clamp) once a nut has been spun up the bolt’s threads. The most tension a bolt can take without failing is called tensile strength; it is the variation in bolt size and in material used to create bolts that gives a bolt a greater or lesser amount of tensile strength. The larger the diameter and the higher the alloy content of the fastener, the higher the amount of the fastener’s tensile strength. A bolt is tensioned below its ultimate tensile strength, but is tensioned to a value high enough to produce “compressive frictional adhesion.” This means that the steel is squeezed together tightly enough that the friction between the pieces prevents any movement. 9.22 Structural Steel Erection UNIT 9

The clamping force between connected plies and the tensile force in a bolt is referred to as preload. Correctly preloaded bolts will not be affected very much by externally applied forces such as wind, earthquakes, snow, and live loads (e.g., people, vehicles). Inadequately preloaded bolts, however, will be affected by these forces and may fail. The Torque-Tension Relationship The relationship between torque and tension for fasteners varies greatly from one fastener to another. Bolt length, steel grade, thread fit and condition, coating type, lubrication amount, nut hardness, and the use of flat washers are all variables in the torque-tension relationship. Since 100% of torque does not equal 100% of tension, these factors can influence the torque required to properly tension a fastener by up to 40% (100% of torque can equal 120% or 80% of tension, a difference of 40%). About 50% of applied torque is needed to overcome the friction under a nut as it is turned, and about 40% of applied torque is needed to overcome the friction between the nut threads and the bolt threads, leaving only about 10% of the turning effort, or torque, to stretch (or tension) a bolt. Note: Extensive testing and use in the field has confirmed great vari- ability in, and the erratic nature of, the torque-tension relationship. Extreme variation of 30% from the mean tension was found in bolts from the same lot, with an average variation of about 10%. Because of this, the Research Council on Structural Connections has not allowed the use of torque-tension tables since 1954 and has deleted torque-tension tables from its own specifications. Over-Tightening When you stop tightening a bolt, the torsional component of the stress in the bolt largely relaxes due to the embedment of the threads of the nut in the threads of the bolt and due to the embedment of the nut and bolt head into the steel plies being clamped together. If a bolt is tightened too much, it will break; however, just because a bolt is tightened more than the minimum amount necessary does not mean that it is “over-tightened” or that it needs to be replaced. As long as the bolt has not frac- tured or broken, it will still perform to specification because of the relaxation of the torsional stress. What this essentially means is that you cannot over-tighten a bolt. It should be noted, however, that excessive loosening and retightening of a nut on a bolt is not desirable because the rotational capacity and clamping force of the bolt will be decreased. Unit 9 — Bolting Up of Structural Steel 9.23 UNIT 9

▶▶OBJECTIVE 4: INSTALLATION OF BOLTS There are three types of connections in which bolts are installed: 1. 2. Snug-Tightened (designated on drawings as “ST”). In these connections, plies are compacted, but bolts are not tensioned to a particular value. Instead, they are tightened to “snug-tight” with the plies drawn firmly together, the bolts more than hand-tight, and all washers in place as required. Pretensioned (designated on drawings as “PT”). In these connections, plies are compacted and bolts tensioned by one of the four approved methods described in Objective 5. Pretensioned connections are required for the following: • • • • • • • • • • • • Bridges or other dynamically-loaded structures, such as crane support steel Slip-critical connections, or where faying surfaces are coated Oversized or slotted holes Connections supporting moving machinery Connections governed by seismic loads Connections between members of a wind-resisting system Moment connections (see Unit 10) Connections in steel that share load with concrete members In-roof truss splices, in-roof truss bracing, and roof truss connections to columns Pre-engineered end plate connections, or where the fit between members is (or is suspected to be) poor Structures significantly taller than they are wide Where a prying load on bolts is high or indeterminate 9.24 Structural Steel Erection UNIT 9

3. Slip-Critical (designated on drawings as “SC”). In this method, plies are compacted and bolts tensioned by one of the four approved methods described in Objective 5, but the steel surfaces being bolted together (known as the faying surfaces) have been specially cleaned and painted. These connections are designed to stay in exact alignment, and should not slip into shear. Note: Oversize and short slotted holes decrease slip resistance by 15%. For 1\" diameter bolts in friction-type joints where washers are used under both nut and head, holes can be as much as a 1⁄4\" larger than bolt diameter without adversely affecting slip behavior or causing undesirable bolt tension loss. For 7⁄8\" bolts, this hole size allowance is 3/16\", and for 11/8\" and greater bolts it is 5/16\". Long slotted holes decrease slip resistance by about 30%, so when they are present in friction-type joints, bolts 1/3\" or larger must be used. The direction of slots is not generally a concern for friction-type joints, but slots must be perpendicular to the direction of loading in bearing-type connections. Under no circumstance should an Ironworker use a torch on a bolt hole. The type of connection into which bolts are to be installed should be indicated on a project’s drawings, or identified through the Engineer of Record (EOR). Bolt Installation Follow these steps to bolt up snug-tightened, pretensioned, and slip-critical con- nections: 1. Ensure that the connections are lined up properly so that the bull, drift, or barrel pins used can be placed correctly in the connections’ holes. 2. To minimize the number of times the same connection must be pinned, place the pin in the most difficult connection to be held together first. This tends to be the hole with the least amount of daylight showing through. Caution! Although a pin must be forced into a hole, never force a bolt into a hole: doing so will damage the bolt’s threads. Unit 9 — Bolting Up of Structural Steel 9.25 UNIT 9

3. 4. Insert the pin through the lug, ensuring that the pin goes through the connecting piece that moves into the member that is stationary. The taper of the pin will align the holes much more efficiently if done this way than if you were to insert the pin through the stationary part of the point. Keep in mind that sometimes, and especially with heavier connections, more than one pin will be required to bring a connection into alignment as more of the load must be shared between each pin. Once you have pinned the connection into alignment, check the orientation of the bolts in the next completed connection of the line, and fill all of the holes in the connection you are working on with the appropriate size, length, and grade of bolt in the same orientation as the bolts in the rest of the line. Place nuts on the lug side of the connection and washers between the nuts and the steel, making sure that both washers and nuts are placed with the grade side facing out for inspection purposes. If you need to impact the head of a bolt, a washer must be placed under the head and not under the nut. In all cases, washers should be placed under the turned element of the fastener assembly. Note: Neither the bolt nor the connection is affected adversely by bolts being installed alternately, but it is a part of proper craftsman- ship to make connections look good by installing all of them in the same fashion. 5. 6. Tighten up all bolts in the connection, proceeding from the fixed to the free edge of the connection. In other words, start tensioning from the point that is closest to the intersection of the two pieces and move away from that point. Keep in mind that if a connection is not tight enough, it will slip and the remaining holes will not be able to be bolted up without further use of pin and hammer. Bolts may need to be snug tightened with a couple of short bursts of an impact gun/ wrench (see Figure 9.10) to keep the connection from slipping while the pins are being removed. 9.26 Structural Steel Erection Figure 9.10 Nut Being Turned to Snug-Tightness with an Impact Wrench UNIT 9

7. Remove the pin or pins, and replace them with the appropriate bolts. 8. Snug tighten these bolts. 9. If needed, tension the entire connection. Slip-critical joints are bolted using barrel pins replaced by fasteners, which are then tensioned to the minimum preload while maintaining the alignment of the con- nection. In such cases, a sufficient number of bolts should be inserted to hold the plys together. Bolts are then placed, snugged, and tensioned as described above; however, to complete the joint, the pins are replaced with tensioned bolts no more than two at a time. This ensures that the force on the joint will be transferred from pins to bolts without slippage. For large connections, such as the one shown in Figure 9.11, you may have to fol- low a tensioning (or tightening) sequence. If needed, this sequence will typically be given in the structure’s drawings or specifications. Mark the number of the sequence on the connection with soapstone and tension the joint as stipulated by the job specifications. Figure 9.11 Large Connection Requiring a Tensioning Sequence Unit 9 — Bolting Up of Structural Steel 9.27 UNIT 9

▶▶OBJECTIVE 5: METHODS USED TO TENSION BOLTS Except when a note on a drawing indicates that bolts are to be installed “snug tight” (i.e., and then not tensioned) all bolts are intended to be tightened by one of the approved methods listed below. All of these methods are accomplished by first bringing a fastener to snug tight (which may be called the snug position) and then rotating the nut a required fraction of a turn to fully tension it. The four methods used to tension bolts within a connection are as follows: 1. Turn-of-nut tightening 2. Calibrated wrench tightening 3. Tightening by use of a DTI 4. TC bolt tightening Turn-of-Nut Method The turn-of-nut method involves achieving proper tension in a bolt by turning its nut a prescribed, proven amount from the starting snug position. The amount of turn beyond the snug position required varies from a 1/3 turn to a 2/3 turn based on a ratio of bolt diameter to bolt length. Table 9.7 lists turn-of-nut rotations required for various bolt lengths. The effectiveness of the turn-of-nut method depends on the uniformity of the snug position; however, since snug-tightening a nut can be done by hand, variations in turns and amount of tension are to be expected: lubrication, the presence or absence of dirt, and using a nut with different threads per inch (tpi) than the bolt can also lead to such variations. To account for potential variations, application tolerances are used, as is shown in Table 9.7. These tolerances are usually ± 1/12 of a turn. Marks on a wrench socket also help keep track of turns, and enable consis- tency in turn-making. While tensioning, be sure to hold the bolt head with a spud wrench so that the bolt will not move in the tightening direction. When using the turn-of-nut method during bolting up, follow the procedures out- lined in Objective 3, being certain to follow a tightening sequence or pattern and tightening bolts and nuts progressively, either away from the fixed or rigid points to the free edges (from the inside to the outside) or, if preferred, from bottom to top as well as top to bottom. Once all pins have been removed and the holes filled 9.28 Structural Steel Erection UNIT 9