Structural Steel Erection Reference Manual

The spacer will help support the side flashing and must sit in a position to allow this while at the same time nesting properly into the flats of the collector panel. Secure the spacer to the framing and through the panel on a low flat using the specified screws in the pattern required by the drawings. It may be necessary to roll up the ends of the solar panels enough to put in the screws, depending on the direction that the spacer faces to the frame. No fasteners will be put in at the top of the Z-bar at this time. The fasteners for the top will also hold the side flashing when installed. If not already done, the bottom perimeter flashing will be the first section to be put into place. This will close off the space between the collector framing top and the bottom piece. The simplest type of flashing to use would be a flat strip with hem edges that is measured to fit in the space. It is usually secured using #14 × 1\" self- drilling screws every 18\" on the top and bottom. Starting from one end, place two screws in line then set up a staggered pattern by setting one of the next screws at a distance of 9\". The sections will be overlapped by 2\" to 3\" and secured together. The ends of the flashing should hang over the ends of the wall by about 21⁄2\" and be folded against the sides. The bottom of the air heating cavity requires 1/16\" drainage holes for any water that infiltrates the cavity. These holes are usually drilled every 18\" along the bottom. Now the side perimeter flashing can be put on. Like the bottom flashing, the side flashing will close off the area that it is put over. The single piece side flashing will likely be one of two basic shapes, L-bar or J-bar. In either case, there is to be a bead of silicone caulking, or caulking tape, between the surfaces. The flashing at the upper edge of the collector, will overhang by 21⁄2\". This will be folded back. The same basic mounting steps will apply for installing the cap flashing as were used on the side flashing. Foam closures typically are installed between the top J-bar and behind the SolarWall® collector panels. Be sure to use the foam closure between the cap and the solar air heating panels. Silicone caulking will also likely be used to secure the foam to the panels. Note: Windows and doors are framed around in a manner similar to that used for the perimeter. The framing around these elements must be flashed using methods similar to the cap, bottom, and side flashing. Flashing for windows must include the appropriate drip edges. Follow the installation instructions to ensure that these areas are properly flashed and sealed. Unit 11 — Handling and Installing Sheeting 11.29 UNIT 11

Trim/Flashing Notes In summary, remember the following: 1. 2. Remove the clear plastic protection sheet from the front of the flashing flats. Side flashing: a. Horizontal panels: Starting from the bottom, put the side flashing into place and secure with the specified screws (usually one every high flat and two at the bottom and where pieces overlap). b. Vertical panels: Starting from the bottom, put the side flashing into place and secure with the designated screws through the spacer (usually placed every 18\" with two screws at the bottom and where pieces overlap). Overlap the sections and seal using the specified caulking between the overlapped sections and the edges. All corners should be sealed and airtight. The front of the top flashing should have a minimum 11⁄2\" lip extending downward with 30° drip edge. Secure top flashing to the sheets through foam closures 3. 4. 5. 6. Note: If required and provided, use 4' × 10' sheets of flashing mate- rial, cut and form to required shape. Always follow the recom- mended cutout pattern. Note: These instructions assume the panels will be installed with the ribs running vertically. This will be true in the majority of cases. However, in some systems the ribs run horizontally. In such instances, foam closures are required to seal the side perimeters instead of the top perimeter. 11.30 Structural Steel Erection UNIT 11

▶ INTRODUCTION TO STRUCTURAL STEEL ERECTION AND DETAIL DRAWINGS UNIT 12 ▶ OBJECTIVES After completion of this unit, you should be able to read structural steel drawings. This knowledge will be evidenced by correctly completing the assignment sheet and by scoring a minimum of 70% on the unit test. You should be able to: 1. Describe structural steel drawings and the Ironworker’s responsibilities in reading them 2. Identify the common types of views used in structural steel drawings 3. Interpret elevations on structural steel drawings 4. Identify drawing symbols and abbreviations 5. Read basic welding symbols 6. Identify and interpret piece marks 7. Recognize and read structural shape dimensions Each of these objectives is covered in the pages that follow. Unit 12 — Introduction to Structural Steel Erection and Detail Drawings 12.1 UNIT 12

▶▶OBJECTIVE 1: STRUCTURAL STEEL ERECTION AND DETAIL DRAWINGS Without the ability to read and interpret blueprints (often called drawings), an Ironworker could not hope to understand the plans and specifications that dictate the construction of a job. For this reason, all foremen and superin- tendents must know how to read drawings (Figure 12.1 shows a foreman reviewing plans and spec- ifications before the erection of a structure), and the ability to do so is often a determining factor when a company selects a new foreman or superintendent. However, to be able to communicate effectively about a job or task, and to recog- nize and resolve concerns before they become problems, every Ironworker should know how to read blueprints, not just foremen and superintendents. Knowing how to read blue- prints also makes an Ironworker more marketable and better at the craft. Drawings are a means through which designers, architects, and engineers com- municate their ideas to construction workers. If these ideas are to be conveyed successfully, it is necessary that the person who prepares the drawings and the workers who read and follow them all understand and use the same general draft- ing standards and techniques. This unit presents the basics of these standards and techniques as they relate to the erection of structural steel. Reading Blueprints Exercise extreme caution at all times while reading and interpreting blueprints, and take nothing for granted. Make sure you study a drawing thoroughly and are cor- rect in interpreting it before proceeding with a task. Even an experienced engineer would not just glance at a drawing and immediately start to work from it. Figure 12.1 Ironworker Foreman Familiarizing Himself with Plans and Specs Prior to Erection 12.2 Structural Steel Erection UNIT 12

Always pay thorough attention to the notes to a set of drawings. These are often as important as a drawing itself: much valuable information is found in notes. Always read all notes before working from any drawing. Remember, too, that the simpler a job is, the more likely you are to make an error. This is because a more complicated or detailed drawing will force you to take more notice of what is required than a less elaborate drawing will. Project drawings are constantly revised as a structure progresses. Always ensure you have – and are using – the latest revision of a set of drawings. Do not, however, discard old or outdated drawings after receiving new updates. You will frequently find that to interpret a new drawing correctly you will need to reference an older version of it, so keep all older versions for reference. To help keep track of which set of drawings is the most recent, add the date on which a new drawing or set of drawings was received to older drawings before filing them. Structural Steel Drawings All drawings used by structural steel Ironworkers begin as design drawings. These include architectural drawings created by the architect and structural drawings created by the structural engineer. They are the master plans of a structure, and show its entire construction. Once design drawings have been created, they are given to a fabricator who hires a detailing company to create Erection (“E”) drawings from them. E drawings show the location of anchor bolts in column footings, the location of each structural steel member in its proper place in the structure, piece marks (see Objective 6), and other needed information. A complete list of anchor bolts, field bolts, and loose lintels is often also included in E drawings, and, in the case of welded work, the total lengths of different welds in lineal inches are given. E drawings are necessary to properly erect the steelwork of a building. Although they provide much of the information needed to construct a structure, they may not give complete information concerning the field connections for the various mem- bers used in the structure. This information is shown on detail (or shop) drawings, which are also prepared by the fabricator/detailer. Sheets 1–13 of the 2040 drawings offer examples of detail drawings. Unit 12 — Introduction to Structural Steel Erection and Detail Drawings 12.3 UNIT 12

▶▶OBJECTIVE 2: COMMON VIEWS USED IN STRUCTURAL STEEL DRAWINGS The most important part of blueprint reading is to visualize the object shown on the drawing. To “visualize” the object is to formulate a complete mental picture of the object: what it is, how it goes together, and all the details connected with it. Architects, engineers, and others help Ironworkers and other blueprint readers visualize their ideas by using perspective, isometric, oblique, and/or orthographic views in drawings. Perspective views depict an object as the eyes see it, or as it would appear in a photograph. Objects farther away from a viewer appear smaller, and horizontal lines recede in space to vanishing points on the horizon. Figure 12.2 shows a perspective view. Note: The term “drawings” is often used interchangeably with “views.” For example, an isometric view may be referred to as an isometric drawing. Figure 12.2 Perspective View An isometric view (see Figure 12.3) shows an object revolved forward so the top can be viewed at a 30° angle. In isometric views circles do not appear round, but as ellipses. 12.4 Figure 12.3 Isometric View Structural Steel Erection UNIT 12

In an oblique view (see Figure 12.4), an object is illustrated with complete forward tilt so that the front view depicted is a “true” view. Circles in the front view, for example, will be true circles, not ellipses. However, in an oblique view the side views recede at 30° or 45° angles, so circles in the side and top views would appear as ellipses. Figure 12.4 Oblique View Orthographic views are perhaps the most familiar of all views on drawings. Erection drawings, shop drawings, and other blueprints all make use of orthographic views, which differ from other views in that only two dimensions are shown: height and width. Orthographic projection (projecting at 90° angles), however, enables three- dimensional objects to be represented on two-dimensional planes in orthographic views. Figure 12.5 depicts an orthographic view typical on detail drawings. Figure 12.5 Example of an Orthographic View Unit 12 — Introduction to Structural Steel Erection and Detail Drawings 12.5 UNIT 12

▶▶OBJECTIVE 3: ELEVATIONS An elevation is a height derived from an established reference point (this may also be called a datum point) such as sea level or the ground. The elevation at the reference point is zero unless indicated otherwise by the plans and/or specifications. Any elevation above the reference point is given a positive value; any elevation below the reference point is given a negative value. For example, if a given elevation reference point is sea level, and a structure is to be built on a location that is 140'0\" above sea level, the elevation of the top of the ground will be 140'0\". Provided that the grade (the degree of incline, or the slope of the reference point) is to remain the same (140'0\") and that the first floor of the building is to be 2'0\" above the grade, the first floor elevation will be 142'0\" (140'0\" + 2'0\"=142'0\"). Similarly, if the basement floor is to be 10'0\" below the first floor, the basement elevation will be 132'0\" (142'0\" – 10'0\" = 132'0\"). Figure 12.6 illustrates these elevations. As in Figure 12.6, the height of any point in relation to another is shown in drawings sim- ply by marking it with a number showing its elevation. The most common of these sorts of elevations found in structural steel erection is finished floor eleva- tion (the height of a building’s finished floor in relation to the refer- ence point). Elevation “Views” Figure 12.6 Elevations When reading structural steel drawings it is important to keep in mind that there is another “elevation” which is completely different from that described above. This “elevation” is more accurately referred to as an “elevation view” and has noth- ing to do with the height of an object. These elevations are sometimes indicated simply by direction: north elevation (looking south), west elevation (looking east), etc. At other times, a grid system is used wherein column lines, sometimes called baylines or gridlines, are numbered in one direction and lettered in the other. In 12.6 Structural Steel Erection UNIT 12

Figure 12.7, the vertical baylines are numbered while the horizon- tal baylines, given at right angles to the numbered baylines, are let- tered. Sometimes elevation views are given with a label, title, or nota- tion telling the reader the loca- tion and direction of the view, such as “Elevation Line A, look- ing North.” In E4 of the 2040 drawings, for example, such a notation appears in this form: Figure 12.7 Grid System with Baylines This notation indicates that the view of the structure the reader is looking at is what the reader would see if the reader were standing to the south of line A on the refer- enced drawing or image (in this case the roof framing plan and second floor framing plan located on E3) and looking north. A cutting plane line (a line drawn with attached arrows) may be drawn on a plan view (a two-dimensional top view) of a structure to indicate the point from which a side or end elevation view or a section view is taken. A section view (some- times called a “section,” or a “cut” or “detail” view) is similar to an elevation view in that it presents its view as if the blueprint reader were standing at the cutting plane line shown on the plan view look- ing in the direction of the cutting plane arrows. While elevations are used to present an overall view of a structure, however, sections are generally used to show details not visible in a plan view. Figure 12.7 is a plan view with a cutting plane line. This cutting plane line calls attention to detail “A,” a section view shown in Figure 12.8. Figure 12.8 Detail “A,” A Section View Unit 12 — Introduction to Structural Steel Erection and Detail Drawings 12.7 UNIT 12

▶▶OBJECTIVE 4: SYMBOLS AND ABBREVIATIONS Drawings have limited space and must convey a great deal of information. To help convey all of the information needed, symbols and abbreviations are used on draw- ings instead of complete words or phrases. If an Ironworker is to accurately inter- pret drawings, then, he or she must recognize these symbols and abbreviations and understand their significance to the total erection process. Table 12.1 lists symbols and abbreviations commonly used in structural steel erec- tion. Remember, however, that symbols and abbreviations may vary. You may encounter abbreviations and symbols that differ from those given below. Commonly Used Symbols and Abbreviations in Steel Erection $ Field Splice Mark • Open Holes Shop Bolt Degree of Finish (larger the number, rougher the finish) Pitch ± Plus or Minus Signs for Clearance ' Feet or Minutes \" Inches or Seconds @ At Square Bar , &, or & And ∙ Parallel AB or A/b Anchor Bolt ABT About ABUT. Abutment AD or A.D. As Drawn ADJ. Adjacent to 12.8 Table 12.1 Steel Erection Drawing Symbols and Abbreviations Structural Steel Erection UNIT 12

Commonly Used Symbols and Abbreviations in Steel Erection ADN. Addition AFF Above Finished Floor AIA American Institute of Architects A.I.S.C. American Institute of Steel Construction AISI or A.I.S.I. American Iron & Steel Institute AL. Aluminum ALT or ALTN Alternate ALY Alloy ALY STL Alloy Steel AMER. NATL. STD. American National Standard AMT Amount ANSI American National Standards Institute APP. Approved APPROX. Approximate ARCH or ARCH. Architect or Architectural A.S. As Shown A.S.C.E. American Society of Civil Engineers ASD Allowable Strength Design ASSEM. Assemble ASSOC. Associates ASSY. Assembly A.S.T.M. American Society of Testing Materials ASWG American Steel Wire Gauge AUX. Auxiliary A.W.S. American Welding Society B to B Back to Back B/E Both Ends BEV. Bevel BF. Braced Frame B.G. Back Gouge BKG Backing B.L. Base Line/Building Line BLDG. Building BLKG Blocking BLW Below BM. Beam Table 12.1 (cont.) Steel Erection Drawing Symbols and Abbreviations Unit 12 — Introduction to Structural Steel Erection and Detail Drawings 12.9 UNIT 12

Commonly Used Symbols and Abbreviations in Steel Erection B.M. Bench Mark B/M or B.O.M. Bill of Material BO Block Out B.O.S. Bottom of Steel BOTT. Bottom B.P. or B.PL. Base Plate B/P. Blueprint BRKT Bracket BS Both Sides B.U.B Backup bar C, , or Channel or American Standard Channel CAV Cavity C.C. or C/C Conveyor to Conveyor CG Center of Gravity CI Cast Iron CIP Cast Iron Pipe CIRC. Or CRCMF. Circumference C.I.S.C. Canadian Institute of Steel Construction CJ. or CLJ. Control Joint/Construction Joint CJP Complete Joint Penetration CK. PL Checkered (Floor) Plate CL. Clearance C/L. (CL) Center Line CLR Clear CM. Centimeter CMU Concrete Masonry Unit COL. Column COL B Collar Beam COM Common COMB. Combination CONC Concrete CONN. Connection CONST. Construction CONT Continuous CONTR Contractor Table 12.1 (cont.) Steel Erection Drawing Symbols and Abbreviations 12.10 Structural Steel Erection UNIT 12

Commonly Used Symbols and Abbreviations in Steel Erection C.R. Cold Rolled CS or C.S. Cast Steel C.S.A. Canadian Standards Association CSK. Countersink Countersink, Near Side Countersink, Far Side CSTG Casting CTL Central CTR. Center CU. Cubic CVNTL Conventional C.W.B. Canadian Welding Bureau CYL. Cylinder DAT Datum DEG or ° Degree DET. Detail DIA. Diameter DIAG. Diagonal DIAPH. Diaphragm DIM. Dimension DIR or Direction DISC. Disconnect DL or D.L. Developed Length DO. Ditto (same) DP Depth D.T.I. Direct Tension Indicator DUP. Duplicate DWG. Drawing E. East EA. Each EBF Excentric Braced Frame E to E or E/E End to End E.F. Each Face EIPS Extra Improved Plow Steel Table 12.1 (cont.) Steel Erection Drawing Symbols and Abbreviations Unit 12 — Introduction to Structural Steel Erection and Detail Drawings 12.11 UNIT 12

Commonly Used Symbols and Abbreviations in Steel Erection EL. Or ELEV. Elevation ELEC Electric EM Expanded Metal ENGR Engineer E.O.R. Engineer of Record EQ. or = Equal EQUIP. Equipment EQUIV Equivalent ESP JT Expansion Joint EST. Estimated EX Example EXP. Expansion EXST. or = Existing EXT. Exterior FAB. Fabricate F.B. Flat Bar FDN Foundation F.F., F/F, or F to F Finished Floor/Far Face FG Finish Grade FIN Finished FL. or FLR Floor FLG. Flange FND or FDN Foundation F.O.B. Freight on Board FR. Frame F.S. Far Side FSC Full Scale FT. Feet FTG. Footing FW. False Work G Girder GA. Gauge GAL. Gallon GALV. Galvanized GI or GALVI Galvanized Iron Table 12.1 (cont.) Steel Erection Drawing Symbols and Abbreviations 12.12 Structural Steel Erection UNIT 12

Commonly Used Symbols and Abbreviations in Steel Erection GL Glass or Grade Line GLZ Glaze G.O.L. Gauge Outstanding Leg G.O.S. Gauge Outstanding Side GR. Grade GS or G.S. Galvanized Steel H.D. Heavy Duty HOR. Horizontal H.R. Handrail H.R.S. Hot Rolled Steel HSS Hollow Structural Section (Tube Steel – round, square, or rectangular shaped) HT. Height I Iron I.D. Inside Diameter I.F. Inside Face IN. Inches INCL. Include/Inclusive INT. Interior I.O.R. Inspector of Record IPS Improved Plow Steel ISO International Standards Organization J. Joist JR. Junior (lightweight beams or channels) JT Joint K.P. Kick Plate L, , or ∟, ∠ Angle Angles, Back to Back L. Left LAT. Lateral LBS. or # Pounds Table 12.1 (cont.) Steel Erection Drawing Symbols and Abbreviations Unit 12 — Introduction to Structural Steel Erection and Detail Drawings 12.13 UNIT 12

Commonly Used Symbols and Abbreviations in Steel Erection LG. Long L.H. Left Hand L.I.W. Load Indicating Washer LLV Long Leg Vertical L.O. Layout L.O.A. Length Over All LONG. Longitudinal LT. Light LVL. Level MACH. Machine MATL. Material MAX. Maximum MC Miscellaneous Channel M.C. Marine Channel MET. Metal MFD Manufactured MFG Manufacturing MFR Manufacturer MIN. Minimum MISC. Miscellaneous MIT Miter MK. or MK Mark MM. Millimeter MOM. Moment M.S. Mild Steel M.T. Magnetic Test MTL Material N. North NA Not Applicable N.C. National Course N.D.T. Non-Destructive Testing N.F. National Fine/Near Face N.L. Nosing Line NO. or # Number NOM. Nominal Table 12.1 (cont.) Steel Erection Drawing Symbols and Abbreviations 12.14 Structural Steel Erection UNIT 12

Commonly Used Symbols and Abbreviations in Steel Erection NOR Normal NOS Nosing N.S. Near Side N.T.S. Not to Scale OA Overall OAL Overall Length O.C. or O/C On Center O.D. Outside Diameter O.F. Outside Face OH Opposite Face O.O. or O/O Out to Out OPG. Opening OPP. Opposite OPP. H. Opposite Hand OPT Optional ORN. Ornamental O.S.L. Outstanding Leg OVHD Overhead PAT. Pattern PCS. Pieces PERP or ⊥ Perpendicular PJP Partial Joint Penetration PL. or PL Plate P. to P. or P.P. Point-to-Point PRCST Precast PREFAB Prefabricated PRI Primary PROJ. Project/Projection PROP Proposed P.S.I. Pounds Per Square Inch PT Pretensioned PWR Power QA Quality Assurance QC Quality Control Table 12.1 (cont.) Steel Erection Drawing Symbols and Abbreviations Unit 12 — Introduction to Structural Steel Erection and Detail Drawings 12.15 UNIT 12

Commonly Used Symbols and Abbreviations in Steel Erection QTY Quantity R. Right/Radius RAD. Radius RBS Reduced Beam Section RD, RND, or Round RE or REINF Reinforce or Reinforcing REF. Reference REFL or REF LN Reference Line REQ’D. Required REV. or Revision R.H. Right hand RM. Ream Rot. Rotation/Rotate R.P. Reference Point S American Standard Beam (I-Beam) S. South S.A.E. Society of American Engineers SC Slip-Critical SCH or SCHED Schedule SECT. Section SH. or SHT. Sheet S.L. or SL. Ship Loose SLP Slope SP Specific SPA. Space SPCS. Spaces SPECS. Specifications SPL. Splice SQ. or □/ Square SR. Stair Rail S.R. Sag Rod SS or SST Stainless Steel ST Snug-Tightened ST or STL Steel Table 12.1 (cont.) Steel Erection Drawing Symbols and Abbreviations 12.16 Structural Steel Erection UNIT 12

Commonly Used Symbols and Abbreviations in Steel Erection ST. or STR. Straight STD. Standard STIFF. Stiffeners STRUCT. Structural STWY. Stairway SUP’T. Support SYM. Symmetrical ⊺ Structural Tee T. Top T& B Top and Bottom T.B. Top of Beam TEMP. Template, Temperature, or Temporary TF/TOF Top of Footing THD. Thread THK. Thick THRU Through TJ Top of Joist T.O.C. or TOC Top of Concrete TOL. Tolerance T.O.S. or TOS Top of Steel T.P. Top Plate TR. Tread TRN BKL Turnbuckle TW Top of Wall TYP Typical U.B.B. Unbonded Brace U/N Unless Noted UON or U.N.O. Unless Otherwise Noted/Unless Noted Otherwise UTRTD Unthreaded VAR Varies VD Void VERT. Vertical VOL Volume Table 12.1 (cont.) Steel Erection Drawing Symbols and Abbreviations Unit 12 — Introduction to Structural Steel Erection and Detail Drawings 12.17 UNIT 12

Commonly Used Symbols and Abbreviations in Steel Erection W Wide-Flange Beam W. West W/ With W.D. Working Drawing WF Wide Flange WH Weep Hole WI Wrought Iron W.L. Working Line W/O Without W.P. Work Point/Wear Plate WT. Weight WWF Welded Wire Fabric or Welded Flange Beam XH Extra Heavy YD. Yard Yld. Yield Z Zee Table 12.1 (cont.) Steel Erection Drawing Symbols and Abbreviations 12.18 Structural Steel Erection UNIT 12

▶▶OBJECTIVE 5: WELDING SYMBOLS Welding symbols are used on drawings to indicate the exact location, size, dimen- sions, and type of a needed weld, along with other information about the weld. An arrow serves as the base of the welding symbol; information about a weld is conveyed through other symbols (weld symbols) and data placed in standard loca- tions along that arrow. Figure 12.9 shows the welding symbol with its arrow, and the specific types of information conveyed through the welding symbol. Figure 12.9 Weld and Welding Symbols Unit 12 — Introduction to Structural Steel Erection and Detail Drawings 12.19 UNIT 12

Figure 12.10 shows various weld symbols that may appear on the welding symbol. Figure 12.10 Weld Symbols The weld symbols shown in Figure 12.9 and Figure 12.10 are the most current approved by the American Welding Society (AWS) and the Canadian Welding Bureau (CWB). The nine generic elements of an assembled welding symbol are described and shown in Table 12.2. ELEMENTS OF AN ASSEMBLED WELDING SYMBOL Name Description Example in Context Reference line The reference line is the horizontal line where weld symbols and other informa- tion are given. The lower side of the line is called the “arrow side,” while the other side is simply called the “other side.” Arrow The arrow points to the location of the weld on the drawing. 12.20 Structural Steel Erection Table 12.2 Nine Elements of an Assembled Welding Symbol UNIT 12

ELEMENTS OF AN ASSEMBLED WELDING SYMBOL Name Description Example in Context Basic weld symbols These symbols designate the type of weld to be used and its location with respect to the arrow. In this case, the weld is to be a fillet weld located on the arrow side of the object to be welded. Dimensions and other data Dimensions provided in a welding sym- bol often include weld size, strength, level, pitch, number, root openings, depths, and groove and angle prepara- tion. The dimensions here indicate that the weld is to be 1⁄2 inch thick and 2 inches in length, and the center-to-cen- ter spacing of the weld is to be 4 inches. 1⁄2 2-4 Supplementary symbols These may indicate weld appearance, materials used, or welding conducted away from the shop. The supplementary symbol given here indicates that the weld is to be convex. 1⁄2 2-4 Finish symbols Finish symbols indicate the method of finishing (not the degree of finish). The finish symbol illustrated is “G,” which indicates that the weld will be finished by grinding. A “C” would indicate a weld to be finished by chipping, while an “M” would indicate a weld to be fin- ished by machining. 1⁄2 G2-4 Tail The tail is only used to emphasize par- ticular references; it is used to help indi- cate that a certain process must be used or certain specifications followed, for example. In this case, the tail calls atten- tion to a specification numbered A-1. If there is no need to indicate a special pro- cess or certain specifications, the tail is nor- mally omitted from the welding symbol. A-1 1⁄2 G2-4 Process speci- fications or other refer- ences These are the reference notations that might be provided in the tail. The refer- ence given here indicates a process to be used (oxyacetylene welding, or OAW). OAW 1⁄2 G2-4 Field Weld Symbol This symbol resembling a flag indicates that a weld needs to be made in the field. This symbol is omitted if a weld will not be made in the field. OAW 1⁄2 G2-4 Table 12.2 (cont.) Nine Elements of an Assembled Welding Symbol Unit 12 — Introduction to Structural Steel Erection and Detail Drawings 12.21 UNIT 12

UNIT 12 Symbols for V-Groove, J-Groove, and U-Groove Welds Symbols for Fillet, Square Groove, and Bevel Groove Welds 12.22 Structural Steel Erection Just as with any part of blueprint reading, being able to correctly interpret weld sym- bols takes practice and experience. Very rarely can someone new to reading blueprints and welding symbols easily call to mind a three-dimensional image of a weld placed according to welding symbol instructions. Table 12.3 can help with such beginning visualizations. Its second column shows what a properly placed weld would look like on a member, while its other columns give the proper terms for the type of weld speci- fied and the weld symbols used to indicate that such a weld is required. Application Arrow-side fillet weld Other-side fillet weld Both-sides fillet weld, one joint Both-sides fillet weld, two joints Arrow-side square groove weld Both-sides square groove weld Arrow-side bevel groove weld Both-sides bevel groove weld Arrow-side V-groove weld Both-sides V-groove weld Arrow-side J-groove weld Both-sides J-groove weld Arrow-side U-groove weld Both-sides U-groove weld Desired Weld Section or End Elevation Plan Table 12.3 Welding Symbols and Applications

Any given detail drawing may contain several dozen or more different welding symbols, and a weld must be made to correspond with each symbol shown. The sheer number of these symbols and the differences between each weld can be over- whelming to someone new to reading blueprints. Just as all of the plans, notes, and specifications must be adhered to for a project to be built correctly, each individual weld must be properly prepared, placed, and welded for a project to be completed properly. There is always an engineering rea- son for all of the specific information shown with each different welding symbol. Figure 12.11 (a portion of a drawing of a welded steel truss) illustrates the significant quantity of welds required that can appear on a drawing, and the engineering needs for such welds. Figure 12.11 Portion of a Drawing of a Typical Welded Steel Truss Note: More information about welding symbols and welding is pro- vided in the welding course. Unit 12 — Introduction to Structural Steel Erection and Detail Drawings 12.23 UNIT 12

▶▶OBJECTIVE 6: PIECE MARKS After their initial creation in a mill, structural shapes are sent to a fabricator in what is called stock (or plain) material, steel that has not been welded, cut, blocked-out/ coped, had holes drilled or punched into it, etc. Any of these preparations to the material that need to happen before the shapes can be used on a job site are done by the fabricator. This includes adding piece marks (also called mark numbers or piece numbers). A piece mark is a code that is normally painted or stamped on a member. It is used as a means of identifying that member: the piece mark stamped on a structural member should correspond with the piece mark indicated for that member on a drawing or set of drawings. The position of a piece mark on E drawings usually corresponds with the location of the erected member’s piece mark. For example, a line may be given on a set of E drawings to represent a particular beam, beam “9B2.” To indicate this, the piece mark label “9B2” will appear on the end of the corresponding line. In this example, the left side of the line is towards the west on the plans, so if the label appears on the left side as it does in Figure 12.12, the beam is erected so that the piece number is towards the west. If the label “9B2” appeared on the right side of the line, the beam would be erected so that the piece number would be towards the east. The letter in the piece mark is often used as a code for the type of structural mem- ber, while the numbers convey drawing information. In Figure 12.12, “B” indicates a beam, the “9” indicates that the member is shown on shop detail sheet number 9, and the “2” references the fact that this beam is the second beam shown on the sheet. Figure 12.12 Piece Mark Lines As They May Appear on a Drawing If a lower-case letter is used in place of an upper-case letter, it indicates a compo- nent part of a member, and is called a small part number. For example, “b2” might indicate an angle bracket on beam B2. A lower-case letter at the end of a piece mark, such as B2a or B2l, however, usually indicates that these members are identical to the originally listed member (in this case, B2), except, perhaps, for a difference of one hole or cope. 12.24 Structural Steel Erection UNIT 12

Note: E1 and E2 of the 2040 drawings show piece marks for angles, beams, columns, door jambs, and door headers. E3 shows examples of piece marks for angle braces and grating. Although identifying marks may vary according to individual company standards, and may vary from fabricator to fabricator or detailer to detailer, the basic method of marking is as follows: Piece mark Job number Example: 6B3 2040 In this example, “6B3” is the piece number; 2040 is the job or contract number. Unit 12 — Introduction to Structural Steel Erection and Detail Drawings 12.25 UNIT 12

▶▶OBJECTIVE 7: STRUCTURAL STEEL SHAPES AND NOTATION SEQUENCES Structural members are made up of standard structural shapes formed from steel. These shapes include beams, angles, plates, channels, tees, zees, and bars, which can be joined together to create girders, joists, trusses, and other useful members. Note: Structural members are normally sent to a job site from a fabricator. Except for plates, standard structural shapes are sent to the fabricator in forty foot lengths. If needed, longer lengths are specially ordered, while shorter lengths are cut from the forty foot pieces. Stock material is rarely sent to a job site before fabrication, but if it is or needs to be, it is generally sent in twenty foot lengths. On drawings, structural steel shapes and their needed dimensions are identified through notation sequences, letters and numbers presented in a specific order to convey information about the type, weight, and dimension of structural members. Descriptions of the various standard structural shapes, and examples of their typi- cal notation sequences, are provided below. Shapes and Sequences American standard beams (Figure 12.13) are generally called I-beams because of their resemblance to the capital letter “I.” They are designated on drawings by the letter “S,” and are easily identified by the sharp slope on the inside face of the flange (162/3% slope). An example notation sequence for an I-beam that might be found on a drawing is S20 × 66 × 12’6”. This means the following: Figure 12.13 American Standard Beam S refers to the structural shape of the beam (i.e., it is an I-beam). 20 is the depth (always actual depth) in inches. 66 is the weight per foot of the piece in pounds. 12’6” is the length of the piece in feet and inches. 12.26 Structural Steel Erection UNIT 12

In other words, the beam in this example (S20 × 66) measures 20” in depth, and has a weight of 66 lbs/ft. Wide-flange beams (Figure 12.14) differ in depth from I-Beams, and are used both as beams and columns. Wide-flange beams are sometimes referred to as H or HP shapes. An example of a notation sequence for a wide-flange beam can be found on detail drawing 8 of the 2040 drawings. For piece 8B3, the member indicated is a W12 × 14 × 14’6”. This means the following: W indicates that the structural shape is a wide-flange beam. 12 is the nominal depth in inches. 14 is the weight per foot of the piece in pounds. 14’6” is the length of the piece in feet and inches. All wide-flange beams have a nominal (not always actual) depth. In other words, a W10 × 39 does not necessarily measure 10” in depth; it might measure 9’ 7⁄8” in depth with a weight of 39 lbs/ft. Similarly, a W8 × 24 might measure 7’ 15/16” in depth, with a weight of 24 lbs/ft. Figure 12.14 Wide-Flange Beam Note: The terms “wide-flange” or “W” are often applied to any shape that has a regular wide flange (e.g., a wide-flange tee). American standard channels (Figure 12.15) are used as girts, purlins, and hangers, and can take the place of light beams. All standard channels have a slope on the inside face of the flange. An example of a notation sequence for a channel can be found on detail drawing 10 of the 2040 drawings, where piece 10DH1 is indicated as a C8 × 11.5 × 15’8”. This means the following: Figure 12.15 American Standard Channel Unit 12 — Introduction to Structural Steel Erection and Detail Drawings 12.27 UNIT 12

C is the designation for channel. 8 is the depth of the channel from flange to flange (this is always an actual dimension). 11.5 indicates the weight of the piece in pounds per feet. 15’8” is the length of the channel in feet and inches. Tees (Figure 12.16) are structural mem- bers formed into the shape of the letter “T.” They are created by cutting a beam through the center of its web, thus forming two T-shapes. An example notation sequence for a wide- flange tee might be WT 6 × 7 × 14’6”: Figure 12.16 Tee W indicates that it is wide-flange. T indicates that the structural shape is a tee. 6 is the length of the leg (the stem) in inches. 7 is the weight of the tee in pounds per foot. 14’6” is the total length of the tee in feet and inches. This shape would be cut from a W 12 × 14 (by cutting the wide flange along the center of the web, two WT 6 × 7s are fabricated). Zees (Figure 12.17) are structural members formed into the shape of the letter “Z.” Their notation sequence is depth by flange width by weight per foot by length. As an example, the notation sequence Z 6 × 31⁄2 × 15.7 × 20’6” is read as follows: Z indicates that the structural shape is a zee. 6 is the depth of the piece in inches. 31/2 is the flange width in inches. 15.7 is the weight of the zee in pounds per foot. 20’6” is the total length of the piece in feet and inches. Figure 12.17 Zee 12.28 Structural Steel Erection UNIT 12

Plates (Figure 12.18) are rolled sheets that are rectangular in cross section. They are designated by the letters “PL.” Universal mill plates (UM) are plates rolled to a specific width. Sheared plates are sheared to specific widths. Plates are also made with a raised pattern (e.g., checker plate). The nominal thickness of the plate is that of the plate exclusive of the height of the raised pattern. Figure 12.18 Plate Steel An example notation sequence for a plate can be found on detail drawing 10 of the 2040 drawings, where piece 10P1 is indicated as a PL 1⁄2 × 18 × 1’6”: PL is the designation for plate. 1/2 is the thickness of the plate in inches. 18 indicates the width of the plate in inches. 1’6” is the length of the plate in feet and inches. Bar steel is like plate steel, but is usu- ally 8” or less in width. It can be square, round, flat (or rectangular), or other shapes. A sag rod is an example of bar steel (see detail drawing 10 of the 2040 drawings for an example). The notation sequence for square bars (Figure 12.19) designates the size of the bar, gives the square symbol ( ), and then indicates the length of the bar. For example, the notation sequence 1” × 6’-0” can be read as follows: 1 is the size of the bar in inches. indicates that the shape is square bar steel. 6’-0” is the length of the bar in feet and inches. Figure 12.19 Square Bar Steel Unit 12 — Introduction to Structural Steel Erection and Detail Drawings 12.29 UNIT 12

The notation sequence for round bars (Figure 12.20) follows a similar pattern: first the size of the bar is given, then the round symbol ( ), and then the length of the bar. For example, the sequence 1⁄2 × 6'-0\" can be interpreted in this way: 1/2 is the size of the bar in inches. indicates that the shape is round Figure 12.20 Round Bar Steel 6'-0\" is the length of the bar in feet and inches. bar steel. The notation sequence for flat bars (Figure 12.21), however, gives the let- ters “FB” first, then the width, then the thickness, and then the length. For example, FB 31⁄2 × 1⁄4 × 6'-0\" means the following: FB indicates that the shape is flat bar steel. Figure 12.21 Flat Bar Steel 6'-0\" is the length of the bar in feet and inches. 31/2 is the width of the bar in inches. 1⁄4 is the thickness of the bar in inches. Angles (see Figure 12.22) consist of two legs (of equal or unequal widths) set at right angles to each other. They are designated by the letter “L.” 12.30 Structural Steel Erection Figure 12.22 Angle with Unequal Legs For angles, the notation sequence (flat bar and plate dimensions) is always given in this order: symbol, length of legs, thickness, and angle length. Angles, of course, have two widths (one for each of the legs); in the case of unequal legs, the longest leg is shown first. UNIT 12

On detail drawing 10 of the 2040 drawings, piece 10A1 is designated an L 3 × 3 × 1⁄4 × 2'9\". This means the following: L indicates that the structural shape is an angle. 3 is the length of one leg in inches. 3 is the length of the other leg in inches. 1⁄4 is the thickness of each leg. 2'9\" is the overall length of the angle in feet and inches. Table 12.4 summarizes the standard notation sequences of many structural steel shapes. STRUCTURAL STEEL SHAPE NOTATION SEQUENCES Type of Shape Notation Sequence Example American standard beam Symbol–height × weight × length S20 × 66 × 12'6\" Wide-flange beam Symbol–height × weight × length W12 × 14 × 14'6\" Bearing pilings Symbol–height × weight × length HP 8 × 36 × 6'-0\" Miscellaneous beam Symbol–height × weight × length M8 × 6.5 × 6'-0\" American standard channel Symbol–height × weight × length C8 × 11.5 × 15'8\" Miscellaneous channels Symbol–height × weight × length MC6 × 12 × 6'-0\" (Standard) tee Symbol–height × weight × length ST12 × 53 × 6'-0\" Wide-flange tee Symbol–height × weight × length WT 6 × 7 × 14'6\" Miscellaneous tee Symbol–height × weight × length MT2.5 × 9.45 × 6'-0\" Zee Symbol × web × flange × weight × length Z 6 × 31⁄2 × 15.7 × 20'6\" Plate Symbol × width × thickness × length PL 1⁄2 × 18 × 1'6\" Square bar Size–symbol × length 1\" × 6'-0\" Round bar Size–symbol × length 1⁄2 × 6'-0\" Flat bar Symbol × width × thickness × length FB 31⁄2 × 1⁄4 × 6'-0\" Equal leg angle Symbol–leg × leg × thickness × length L 3 × 3 × 1⁄4 × 2'9\" Unequal leg angle Symbol–leg × leg × thickness × length L6 × 4 × 1⁄2 × 6'-0\" Pipe Nominal inside diameter-type 6\" standard pipe Tubing Nominal outside diameter × wall thickness × length HSS 6 × 4 × 1⁄4 × 6'-0\" Table 12.4 Notation Sequences of Structural Steel Shapes Unit 12 — Introduction to Structural Steel Erection and Detail Drawings 12.31 UNIT 12

Structural Members in Application Structural steel members can be used for many different purposes within a single structure. Some of these different applications are shown in Figure 12.23 (a legend follows the figure). Bear in mind that this figure simply provides an overview. It is impossible to cover all of the potential applications for which a structural member may be designed. Figure 12.23 Structural Steel in Buildings LEGEND 1 Angle lug on framed opening 2 Anchor bolts 3 Column base plate 4 Second floor beams 5 Wall bearing base plates (shoes) 6 Bracing for structural steel 7 Seat (shelf) lug 8 Column 9 Conveyer structural steel framework 10 Crane rail beams and stops 11 Overhead door jams 12 Floor plate 13 Girder 14 Grilled beams of steel for crane rail column base supports 12.32 Structural Steel Erection UNIT 12

LEGEND 15 Joist support in a framed opening 16 Floor deck 17 Lintel 18 Canopy 19 Monorail beam 20 Sash angles 21 Crane rail to column angle clip 22 Brick angle 23 Column poured in concrete 24 Bar joist 25 Window sill 26 Suspended ceiling supports 27 Sag rod 28 Trusses 29 Bolted column splice 30 Rebar anchors on rafters on block way bond beams 31 Girts 32 Purlins 33 Crane rail column 34 Grating 35 Roof deck 36 Shear stud 37 Beam to column clip 38 Cross-bridging for bar joist 39 Stairs and handrail 40 Monorail beam clamp Unit 12 — Introduction to Structural Steel Erection and Detail Drawings 12.33 UNIT 12

12.34 Structural Steel Erection UNIT 12

▶ READING STRUCTURAL STEEL BLUEPRINTS UNIT 13 ▶ OBJECTIVES After completion of this unit, you should be able to interpret structural steel drawings. This knowledge will be evidenced by correctly completing the assignment sheet and by scoring a minimum of 70% on the unit test. Specifically, you should be able to: 1. Identify the information on structural steel erection and shop detail drawings This objective is covered in the pages that follow. Unit 13 — Reading Structural Steel Blueprints 13.1 UNIT 13

▶▶OBJECTIVE 1: READING STRUCTURAL STEEL ERECTION AND SHOP DETAIL DRAWINGS Table 13.1 provides information on the structural steel erection and shop detail drawings found in the blueprints packet and referenced throughout this manual. An Ironworker must understand these drawings to be able to correctly erect the structural steel members according to the architect’s and engineer’s specifications. The integrity of a structure depends on drawings being read and followed correctly. DRAWING NUMBER NAME DESCRIPTION AB1 Anchor Bolt Plan This plan shows the location of each set of anchor bolts and the proper spacing of the anchor bolts within each individual pattern and as they relate to one another. A section or detail is shown giv- ing the Ironworker the diameter and length of the anchor bolts, as well as the nut and washer requirements. The amount of space needed for grouting purposes is also shown here, as is the elevation of the finished floor. This plan also gives column and grid line designations and their proper center lines. E1–E2 Front & Back Isometric Views These two sheets show the finished building in 3-D. This can help the Ironworker visualize the finished product. E3 Framing Plans This drawing gives information regarding the framing of both the second floor and the roof. The location of the two angle roof frames is given on this sheet, as are the sections for the bar joists. There is also a lot of information in the notes for this drawing which pertain to the erection and installation of the bar joists. E4 Elevations This drawing shows each elevation line. It also gives each of the three different column splice details. Table 13.1 Structural Steel Drawings Summary 13.2 Structural Steel Erection UNIT 13

DRAWING NUMBER NAME DESCRIPTION E5 Roof Decking & 2nd Floor Grating Plan The grating plan and the roof decking plan are both shown on this sheet. This provides the Ironworker with all of the information needed to properly place the grating and decking in their respective locations. Many notes are given which pertain to the decking. E6 Stair Plan & Sections On this sheet the stair and ladder erection plan is given. There are also four sections shown, three for the stair erection and one for the ladder installation. 1–5 Columns These are shop fabrication or shop detail draw- ings. They give all of the information needed for the Ironworkers to fabricate the columns needed for this structure. The Bill of Material on each sheet gives all of the small part information, the shop and field bolts needed, as well as the indi- vidual and total weight of the pieces. 6- 9 Beams These are shop fabrication or shop detail draw- ings. They give all of the information needed for the Ironworkers to fabricate the beams that are needed to erect this structure. The Bill of Material on each sheet gives all of the small part information, the shop and field bolts needed, as well as the individual and total weight of the pieces. 10 Miscellaneous Pieces This shop drawing shows the fabrication details for the miscellaneous members that are included with this structure. These include the door jambs and header, the sag rod and girt, the leveling plates for the columns, and the two angle roof frames. Field bolts and small part information is given in the Bill of Material, including the weights of each piece and the total weight. 11–12 Braces These two sheets give the Ironworkers all of the information they need to fabricate the necessary braces for this project. The Bill of Material on each sheet gives all of the small part information, the shop and field bolts needed, as well as the individual and total weight of the pieces. Table 13.1 (cont.) Structural Steel Drawings Summary Unit 13 — Reading Structural Steel Blueprints 13.3 UNIT 13

DRAWING NUMBER NAME DESCRIPTION 13 Grating This shop drawing shows the fabrication details for the grating needed to erect this structure. The Bill of Material includes the weights of each piece and the total weight. 21–23 Stair Stringer & Handrail, Stair Stringer & Ladder, and Handrail These sheets give the Ironworkers all of the information they need to fabricate the necessary stair stringers, handrails, and the ladder for this project. The Bill of Material on each sheet gives all of the small part information, the shop and field bolts needed, as well as the individual and total weight of the pieces. Table 13.1 (cont.) Structural Steel Drawings Summary 13.4 Structural Steel Erection UNIT 13

▶ SECTION 3 ERECTING OTHER STRUCTURES UNITS 14-19



▶ ERECTING BRIDGES UNIT 14 ▶ OBJECTIVES After completion of this unit, you should be able to identify the basic types of bridges and describe the general process for erecting a bridge. This knowledge will be evidenced by correctly completing the assignment sheet and by scoring a mini- mum of 70% on the unit test. Specifically, you should be able to: 1. Explain the history of bridge construction 2. Describe how bridges work with respect to loads, forces, and spans 3. Identify six of the most common types of bridges 4. Describe major steps in the erection of a bridge Each of these objectives is covered in the pages that follow. Unit 14 — Erecting Bridges 14.1 UNIT 14

▶▶OBJECTIVE 1: HISTORY OF BRIDGE CONSTRUCTION Ironworkers build bridges (see Figures 14.1 and 14.2). In fact, we build them so much that “bridge” is the first type of work listed in our name, the International Association of Bridge, Structural, Ornamental and Reinforcing Iron Workers. Bridges are built to span a physical obstacle such as a valley, road, railroad tracks, river, or other body of water. Their designs vary depending on the function of the bridge and the nature of the terrain where the bridge is to be constructed (in other words, they vary based on the obstacle to be overcome). Bridge erection requires many of the same skills required in erecting buildings, but there are some important considerations to take into account when erect- ing bridges. For example, working over water can present special challenges with respect to the safety of the workers involved in the project. Hoisting equipment can also differ from the types used for conventional structural erection. For the erection of a bridge over water, cranes may need to be on barges to provide the best acces- sibility to the erection site. The first bridges were likely constructed of wooden logs or planks using a simple support and crossbeam arrangement. Most of these early bridges were very poorly built and could rarely support heavy weights; however, even well into the 19th cen- tury most bridges were made of wood as timber was inexpensive and designers did not have to worry about the moving weight of automobiles and heavy trucks. Figure 14.1 Bridge Being Constructed Over Land Figure 14.2 Bridge Being Constructed Over Water 14.2 Structural Steel Erection UNIT 14

Still, these bridges were plagued with problems: even the best woods have little strength in tension and wood can rot, dry out, be eaten by termites, or catch fire. Many a wooden bridge has been destroyed by fire caused by lightning. It was this inadequacy that led to the development of better bridges, including stone bridges: stone is the longest-lasting bridge material and has been used in the making of bridges for millenia. Some stone arch bridges and aqueducts built over two thousand years ago are still standing, such as that shown in Figure 14.3. Figure 14.3 Old Arch Bridge These arch-based bridges are often beautiful, have impressively long spans, and could withstand conditions that would have swept other bridges away; however, they are generally too costly to build today. Most bridges today are made with steel, and have evolved over the past 200 years as engineers have come to better understand the possibilities inherent first in cast iron and then in wrought iron. Bridges today are typically made from structural steel, but reinforced, pre-stressed and post-tensioned concrete, as well as compos- ite materials, are also used. Steel works well for bridges because of its tremendous compressive and tensile strength, and because it is available in many shapes and sizes, including in wires and cables, plates, and shaped bars or beams. It is also economical, reliable, and versatile, permitting all sorts of designs to solve special problems. Concrete has adequate compressive strength for bridge piers, as well as for paved roadways, but it is very heavy and has little tensile strength. Tensile strength can be added to concrete by reinforcing it with steel bars, which can make it suitable for short-span bridges. Sometimes concrete bridges are designed as arches and faced with stone so they resemble stone arch bridges. Pre-stressed concrete contains stretched strands of steel wire that make it possible for concrete beams to span longer distances; however, very few pre-stressed bridges have been attempted that approach the size of monumental steel bridges. Unit 14 — Erecting Bridges 14.3 UNIT 14

▶▶OBJECTIVE 2: HOW BRIDGES WORK There are three basic considerations in bridge construction: the types of loads the bridge will endure, the forces that may act upon the bridge, and the possible spans that may be used. Loads The three types of loads to consider in bridge construction are the weight of the bridge itself, the live and moving loads, and the wind load. Consider, for instance, the very first type of bridge in existence: it was probably a plank of wood placed over a stream. If a plank used for this purpose is thin in rela- tion to its length, it will sag; if it is too long, it will collapse. This is evidence that you must take into consideration the weight of a bridge itself, otherwise known as the dead or static load. If, however, you stand at the middle of the plank over the water, it may sag even more. In designing a bridge, therefore, the maximum weight of whatever the bridge is intended to carry must also be considered. This is called the live or dynamic load. When you walk across the plank, it bounces under you, illustrating the effect of a moving or movable live load. If a strong wind were to push against the plank, it would cause it to shake. This is the wind load that must be kept in mind. Forces The various forces that act on a bridge (see Figure 14.4) result in stresses in its parts or members. All bridges except arch bridges are designed to handle both tension and compression. When you put a weight on a timber that is resting on the ground, the only stress you need to worry about is compression. But if you place the timber between supports, making a “beam” bridge, that same weight creates two stresses. The top of the timber is in compression, but the bottom is in tension. 14.4 Structural Steel Erection Figure 14.4 Forces Acting Upon a Bridge UNIT 14

The bridge must therefore be designed to handle both compression and tension with- out buckling or snapping. Buckling is what happens when the force of compression overcomes a member’s ability to handle compression, while snapping is what hap- pens when the force of tension overcomes a member’s ability to handle that tension. Torsion is the stress produced by rotation or twisting of the bridge components, which is typically caused by high winds. This force has largely been eliminated in all but the largest suspension bridges. Bridges are designed either to dissipate or transfer these forces. To dissipate force is to spread it out over a greater area, which prevents any one spot from having to bear the concentrated burden of the force. To transfer force is to move it from an area of weakness to an area of greater strength, an area that is specifically designed to handle the force. Spans The span of a bridge (shown in Figure 14.5, which details the major components of a bridge system) is the distance between bridge supports. These supports may be columns, towers, or even the walls of a canyon. Some bridges consist of a single span while others have multiple spans. Lengths vary greatly, too: a beam bridge is likely to span a distance of up to 250 feet, a girder bridge up to 600 or 700 feet, a modern arch bridge can safely span up to 800 or 1,000 feet, and a suspension bridge can span up to 7,000 feet. There are three basic types of spans: simple, continuous, and cantilever. Any of these spans may be constructed using beams, girders, or trusses. Figure 14.5 Basic Parts of a Bridge Unit 14 — Erecting Bridges 14.5 UNIT 14

A simple span (Figure 14.6) is comprised of structural members that cross from one substructure unit to another. A simple span has fixed bearings on one end and expansion bearings on the other end. Any bridge that is supported by abutments alone is a simple span. Bridges are some- times constructed of multiple simple spans. Figure 14.6 Simple Span A continuous span (Figure 14.7) is a bridge or bridge segment with structural members that span continuously over one or more substructure units without a break. The structural members may have to be spliced to obtain the appropriate length; however, they are still considered single-piece members. Continuous spans are typically anchored to the substructure by a number of expansion bearings and a single fixed bearing. Bridges may be com- prised of a combination of both simple and continuous spans. Figure 14.7 Continuous Span A cantilever span (Figure 14.8) is used in bridges where the span is supported not at the ends but toward the center of the bridge truss (a cantilever is a beam or truss rigidly supported at one end, or in the middle, but not at both ends; it has forces applied along the free arm or at the free end). Many drawbridges are cantilever bridges, while canopies, balconies, large construction cranes, and diving springboards all make use of cantilevers. 14.6 Structural Steel Erection The cantilever beam of a bridge section is much weaker than a similar beam twice as long but supported at both ends. This should be taken into account when canti- lever spans are constructed. Figure 14.8 Cantilever Span UNIT 14

▶▶OBJECTIVE 3: BRIDGE TYPES There are many different types of bridges in the United States and Canada today; however, six of the most common types include beam bridges, girder bridges, truss bridges, arch bridges, suspension bridges, and cable-stayed bridges. Beam Bridges One of the simplest types of bridges is the beam bridge. Most of the bridges built by Ironworkers are the beam bridges we drive across every day. The bridge shown in Figure 14.9 is a com- mon highway beam bridge. Figure 14.10 also shows a modern beam bridge. Beam bridges consist of a horizontal beam supported at each end by piers. Since the weight of the beam pushes straight down onto the piers, the farther apart the piers are, the weaker the beam becomes. As a beam bridge is lengthened, it requires more supporting piers. As a result, beam bridges usually cover relatively short dis- tances (they rarely span more than 250 feet) and may be deemed unsuitable in instances where a bridge needs to have a lot of space underneath it. Figure 14.9 Common Highway Beam Bridge Large modern beam bridges use carefully designed beams to support the bridge deck; however, there are examples of stone beam bridges that have survived for a long time. In general, beam bridges must be designed to resist the bending that will occur with the heaviest load that the bridge is designed to withstand. Compression must also be overcome as it occurs on the top side of the beam bridge’s deck or roadway as it will shorten the upper portion of the deck. Compression on the upper portion of the deck also causes tension in the lower portion of the deck, which then lengthens that portion. Figure 14.10 Beam Bridge Unit 14 — Erecting Bridges 14.7 UNIT 14

To combat these potential problems, many beam bridges that you find on highway overpasses use concrete or steel beams to handle the load, while the size of the beam, and in particular the height of the beam, controls the distance that the beam can span. By increasing the height of the beam, the beam has more material to dis- sipate compression. Girder Bridges A girder bridge (Figure 14.11) is named such because it is comprised of girders. In modern steel girder bridges, the two most com- mon girders are I-beam girders and box girders. If we look at the cross section of an I-beam girder (Figure 14.12) we can immediately understand why it is called an I-beam (The cross section of the girder takes the shape of the capital letter I). A box girder (Figure 14.13) is much the same as an I-beam girder except that it takes the shape of a box. The typical box girder has two webs and two flanges; in some cases, however, there are more than two webs, creating a multiple chamber box girder. An I-beam is very simple to design and build and works very well in most cases. However, if a bridge contains any curves, the beams become subject to torque. The added stability and increased resistance to torque that the design of the box girder possesses makes it a better choice for bridges that involve any significant curvature. Because box girders are more stable, they are also able to span greater distances and are often used for longer spans than I-beams are. Figure 14.11 Girder Bridge Figure 14.12 I-Beam Girder Figure 14.13 Box Girder Note: The design and fabrication of box girders is more difficult and generally more expensive than that of I-beams. For example, in order to weld the inside seams of a box girder, a human or welding robot must be able to operate inside the box girder. 14.8 Structural Steel Erection UNIT 14