STRUCTURAL STEEL EDUCATIONAL COUNCIL

TECHNICAL INFORMATION & PRODUCT SERVICE

December 1993

Common Steel ErectionProblems

and Suggested Solutions

by

James J. Putkey

Acknowledgements

The author wishes to thank the following persons for their input, review,and comments on the content of this Steel TIPS publication:

· Members of the Structural Steel Educational Council· Dave McEuen, California Erectors, Bay Area, Inc.· William C. Honeck, Structural Engineer with Forell/Elsesser Engineers, Inc.

The information presented in this publication has been prepared in accordance with recognizedengineering principles and construction practices and is for general information only. While it isbelieved to be accurate, this information should not be used or relied upon for any specificapplication without competent professional examination and verification of its accuracy, suitability,and applicability by a licensed professional engineer or architect. The publication of the materialcontained herein is not intended as a representation or warranty on the part of the Structural SteelEducational Council, or of any other person named herein, that this information is suitable for anygeneral or particular use or of freedom infringement of any patent or patents. Anyone making useof this information assumes all liability arising from such use.

COMMON STEEL ERECTION PROBLEMS ANDSUGGESTED SOLUTIONS

List of Problems

No. • Pa_=e No.

Erection5. One-Bolt Connections 116. Columns or Bents Tied Together With Non-Bolted Steel Joists 157. Steel Joists Without Bolted Bridging 168. Columns or Bents Tied in With Timber 179. Steel Columns or Partial Bents Not Tied In 1810. Non-Self-Supporting Steel Frames 1911. Column Splices Too Low or Too High Above Floor 2012. Columns Interrupted by Beams 2113. Columns Offset From Beam Framing 2214. Revisions and Alternates Not Flagged on Drawings 2315. Double-Framed Beam Connections to Girder 2416. Double-Framed Beam Connections to Column Web 25

Bolting17. Mixed Bolts 2718. Mixed Bolt Diameters 2819. Reuse of High-Strength Bolts 28

Welding20. Prequalified and Non-Prequalified Weld Joints 2921. Extending Continuity Plate for Back-up Bar 3022. Welded Connections to Inside of Column 3123. Restrained Welded Joints 3324. Fie ld-Welded Curb Angles 35

Decking25. Steel Floor Deck Spanning Uneven Surfaces 36

General26. Project Specifications 37

Anchor Bolts1. Low Anchor Bolts 52. Misplaced Anchor Bolts 7

3. Rotated Anchor Bolt Pattern 94. Inadequate Anchor Bolts for Column Erection 10

COMMON STEEL ERECTION PROBLEMS ANDSUGGESTED SOLUTIONS

Introduction

Preface

About two years ago a structural engineer asked methe following question, "Why don't you write a book-let on steel erection? We keep seeing the sameerection problems occur over and over again, and itwould be nice to have a reference for erectors,fabricators, and structural designers to either avoida problem or to present a solution to a problem."The question was posed to two steel erectors, andthey both thought such a publication would be anexcellent idea. The end result is this Steel TIPS.

Many publications exist that inform the structuraldesigner on how to select types of steel, designeconomically, reduce fabrication costs, and how todesign various types of structures or portions ofstructures. But what source of information is avail-able to the designer when the steel erector makesan inquiry regarding the steel design or experiencesproblems that require the designer's input? Theseinquiries or problems may result from:

· Erection or fabrication errors.· Erection procedures or sequences.· Faulty work of other trade contractors.· Design that can lead to safety problems.· Erection equipment loads into the structure.· Changes or alternates requested by the owner.

Now, looking ahead in the construction timetable,one might logically ask the following questions,"What source of information is available to thestructural designer to produce a design that canavoid these erection problems? What are thedetails to avoid? What are the desired details? Whydoesn't the steel industry provide structural design-ers, and others, with solutions to common design-related problems experienced bythe steel erector"

Purpose

The purpose of this Steel TIPS is to provide struc-tural designers and steel erectors with a basic andconvenient source of solutions to common steelerection problems that involve the structural de-signer.

Organization and Content

To provide structural designers with solutions tocommon steel erection problems, 26 common prob-lems with suggested solutions are provided. Theproblems are divided into six categories: anchorbolts, erection, bolting, welding, decking, and gen-eral. In each category a specific problem is shownby its title. The problem is then described and thesuggested solution is given.

The content of this Steel TIPS does not address thevarious methods of erecting steel. If the designerneeds to design a structure with unusual features,or with a required erection procedure or sequence,then a sponsor firm of the Structural Steel Educa-tional Council might be consulted to make certainthe unusual features can be economically erected.

The erection problems presented are not only "com-mon'' problems, but may also be considered basic,reoccurring problems. So the content is chosen tobe especially useful to the new structural designer(and maybe experienced designers).

Some of the problems or portions of problemsaddressed in this Steel TIPS are mentioned oraddressed in previous Steel TIPS, or in the AISCpublications Modern Steel Construction, and SteelDesign Guide Series. These problems and theirsolutions are now conveniently gathered into thispublication.

4

1. Low Anchor Bolts

Problem

Anchor bolts are sometimes set with their topslower than the detailed elevation. Two situationscan exist: 1 ) the bolts are placed so Iow that the topof the bolt is below the top of the base plate and theanchor bolt nut cannot be engaged, or 2) the bolttop extends above the base plate, but not highenough to allow full thread engagement of the nut.

Setting Tolerances. Section 7.5 of the AISCCode of Standard Practice requires the owner toset anchor bolts in accordance with approvedanchor bolt plans. [1] The Code provides for a+1/2-inch tolerance for the elevation of the top ofanchor bolts. The contractor setting the anchorbolts should be able to meet this tolerance, buterrors can occur. Section 7.5 in the Commentaryon the Code of Standard Practice discusses theinstallation of anchor bolts. [2]

Bolt Detailing. Anchor bolt detailing is discussedin Chapter 7 of AISC Detailing forSteel Construc-tion. [3] To match the minus 1/2-inch tolerancenoted in Section 7.5 of the Code, the steel detailershould allow for at least a 1/2-inch projection of thebolt above the top of the nut. If the anchor bolt isset 1/2-inch Iow, the nut will still obtain full threadengagement. However, when the minus 1/2-inchtolerance is exceeded, the problem of a Iowanchor bolt exists.

S o l u t i o n

Extending the Bolts. Anchor bolts that are setIow are commonly called "short anchor bolts."Short bolts need to be corrected by making themlonger. Two methods of making the bolts longerare threaded couplers and welded extensions.The "Steel Interchange" feature in Modem SteelConstruction, January 1993, and "Some PracticalAspects of Column Base Selection," SteelDesignGuide Series 1: Column Base Plates, discussthese two methods. [4, 5] For either correctionmethod, the erector must work with the structuraldesigner (and general contractor). If the anchorbolts are designed to resist uplift, in addition toproviding column stability during erection, then thestructural designer may require special proce-dures. See AISC Manual of Steel Construction,Specification J10, page 5-172, for loads on an-chor bolts. [6]

Preventative Solution. A"preventative" solutionthat anticipates Iow anchor bolts is to design anddetail anchor bolts with additional bolt projection.Examples include:

· The structural designer shows a 1-inch bolt pro-jection above the top of the nut in the base platedetails on the structural drawings. This 1-inchbolt projection allows bolts to be set an additional1/2-inch lower than the minus 1/2-inch setting toler-ance provided by the AISC Code of StandardPractice, and still obtain full thread engagement.

· The steel fabricator details anchor bolts with thetop of the bolt one bolt diameter above the top ofthe nut. So for bolts larger than 1-inch diameter,even more bolt projection is furnished than theabove example. For example, the detail of a 2-inch diameter bolt will show the top of the boltdetailed 2 inches above the top of the nut.

Full Thread Engagement. Short anchor boltsthat prevent full thread engagement can be afrustrating problem. First, the question arises,What is full thread engagement?. Section IIl.F inChapter 2 of AISC Quality Criteria and InspectionStandards discusses full thread engagement forhigh-strength bolts. [7] Section III.F refers toSection 2(b) of the "Specification for StructuralJoints Using ASTM A325 or A490 Bolts," on page5-265 of AISC Manual of Steel Construction. [6]Section 2(b) states, "The length of bolts shall besuch that the end of the bolt will be flush with oroutside the face of the nut when properly in-stalled." The same criteria could apply to nuts onanchor bolts.

Second, what action is necessary if the top of thebolt is just below the top of the nut? Instead oflengthening the bolt, the nut might be welded to thebolt by filling in the space between the top of thebolt and the top of the nut with weld metal. How-ever, welding the nut to the bolt is not alwaysallowed, particularly if high-strength, heat-treatedbolts and nuts are used, and the bolts are subjectto tensile loads. See "Steel Interchange" in theDecember 1992, May 1993, and July 1993 issuesof Modern Steel Construction. [8, 9, 10] If theerector can prove the '"fill-in" weld is adequate, thestructural designer may approve this welding pro-cedure. But to provide proper column support, theweld may need to be made before the lifting line isreleased from the column.

5

Instead of welding the nut to the bolt, the erectormight consider limited air carbon arc gouging ofthe base plate surface under the nut to provide fullthread engagement. This procedure must beapproved by the structural designer.

Practical Procedure. A practical procedure is forthe erector to review the as-built survey of the boltelevations before starting erection, determine boltsthat are set Iow, work with the contractor to resolvehow to correct them, decide who is to make thecorrections, and make corrections before erectioncrews arrive at the jobsite.

2. Misplaced Anchor Bolts

Problem

The erector discovers anchor bolts are:

· Incorrectly spaced.· Located off the established column lines.· Tilted (out of plumb).· Bent over flat, damaged, or even broken off.· Installed with the bolt pattern rotated 90 degrees.

See the problem, "Rotated Anchor Bolt Pattern."· Installed to include anycombination of the above.

Installation Conditions. The installation of an-chor bolts is not an easy task under the best ofconditions. If the foundation contractor has a firm,level, dry, and uncongested job site, then the steelerector will probably find properly installed anchorbolts. But we all know most foundation sites arenot in the above listed condition. So misplacedanchor bolts may be expected.

S o l u t i o n

Survey of Bolts. The first line of defense for thesteel erector against misplaced anchor bolts is toreview the as-built anchor bolt survey before steelerection starts. Then the steel erector will know ifany corrective work is required, have the correc-tive work performed before steel erection starts,and not be faced with the frustration and delayexpense of correcting the bolts while erecting thecolumns.

Setting Tolerances. Section 7.5 of the AISCCode of Standard Practice specifies tolerances forsetting anchor bolts. [1] These tolerances ac-knowledge that bolts will not be set exactly asshown on the anchor bolt plan. To allow formisplaced bolts, holes in the base plates or holesin the framing angles from the columns to the baseplates are allowed to be made oversized. SeeTable 6-1 on page 6-12, ManualofSteelConstruc-tion, Vol. II, Connections. [11] For example, 23/4-

inch diameter holes are allowed for 13/4-inch diam-eter bolts. Thus, the oversized holes will allow theerector to overcome some misplacement of theanchor bolts.

If the bolts are misplaced too much for the over-sized holes to overcome, then corrective workmust be performed. The type of corrective work

depends on the function of the anchor bolts. Allanchor bolts serve to locate the columns andprevent overturning of the columns during steelerection. Some anchor bolts tie the column to thefoundation to resist uplift, overturning, and shearfrom building design loads. The latter functionsmay require more extensive corrective work formisplaced bolts. In any event, inform the struc-tural designer of the corrective work.

If bolts are misplaced up to 1/2 inch, the oversizedbase plate holes normally allow the base plate andcolumn to be placed near or on the column line.For example, the 23/4-inch diameter base platehole for a 13/4-inch diameter anchor bolt allows fora 1/2-inch adjustment of the base plate. If the boltsare misplaced by more than 1/2 inch, then correc-tive work is required.

Anchor Bolts Designed to Prevent Overturn-ing of Column During Steel Erection. Foranchor bolts designed to prevent overturning ofthe column during steel erection, corrective workmay include:

· Slotting the base plate or column angle holes.· Fabricating a base plate to match the misplacedbolts.

· Fabricating an oversized base plate with stubbolts welded to the base plate in the correctlocation, and then welding the base plate to therotated bolts.

· Making an "s" bend in the bolts. (But not toosharp of a bend.)

· Chipping away the concrete to make a larger "s"bend.

· Burning off the bolt and placing new expansionbolts.

· Burning off the bolt and welding a new bolt to theside of the projecting stub.

An extensive discussion on misplaced anchorbolts is given in "Some Practical Aspects of Col-umn Selection," by David T. Ricker. [5] A discus-sion on the design and use of column bases andbase plates is contained in Chapter 6 of the AISCManual of Steel Construction, Volume II, Connec-tions. [11]

Another solution that anticipates anchor bolt mis-placement is for the structural designer to detailoversized holes in the base plates that are evenlarger than the oversized holes allowed by Table

6-1 on page 6-12, Manual of Steel Construction,VoL II, Connections. [11] Plate washers with boltholes 1/16 inch larger than the bolt diameter arethen welded to the base plate. This solution allowsadditional tolerances in setting the anchor bolts.The plate washer is placed between the top nutand the top of the base plate, and is welded to thebase plate after the column is erected and aligned.A bottom plate washer is required above thebottom leveling nut. This bottom plate washer isnot really added material because it will also beneeded with the standard oversized holes. Seethe following detail for anchor bolt, nut, and platedetails.

Anchor Bolts That Resist Uplift, Overturning,and Shear. For anchor bolts designed to resistuplift, overturning, and shear from building designloads, corrective work may be limited to:

· Slotting the base plate or column angle holes.· Fabricating a base plate to match the misplaced

bolts.· Chipping out the concrete, removing the mis-

placed bolts, and concreting in new, correctlyplaced bolts (in the extreme case).

COLUMN

EXTRA OVERSIZE HOLEIN BASE PLATE

WASHER

- C%OUT %_.-E-

CONCRETE///

PLATE

B

GROUT FORM

x_ PLATE WASHER •. NOT REQUIRED IF / / /

LEVELING NUT • SHIMS ARE USED/ / / , • /

,ANCHOR/ /

BASE PLATE DETAIL

Exercise caution before using this detail. If theanchor bolts are designed to resist column shearforces (see below), the anchor bolts must bedesigned to resist bending because shear forcesto the bolts are applied at the plate washer--whichmay be a few inches above the surface of theconcrete.

3 . R o t a t e d A n c h o r B o l t P a t t e r n

P r o b l e m

The erector discovers anchor bolts placed with theanchor bolt pattern rotated 90 degrees from thedetailed orientation.

I I l

O 1 • - - OI I I

DetailedOrientation

I I I- - 0 - - + O--

- - + .. +--

- - O - - + - 0 - -I I I

As-BuiltOrientation

Solut ion

Uniform Spacing. One means to prevent rotatedanchor bolt patterns is to use uniform bolt spacing.As stated by David T. Ricker in Steel TIPS, 'q'hepossibility of foundation errors will bereduced...when anchor bolt spacing is kept uni-form throughout the job." [12] If a square anchorbolt pattern is used, a rotated pattern cannotoccur. So the ultimate uniform spacing is to designa square anchor bolt pattern--if possible.

Anchor bolt patterns that are rotated 90 degreesmay be corrected using the procedures listed formisplaced anchor bolts.

S u r v e y of Bolts. When the anchor bolts aresurveyed before fabrication, the base plates maypossibly be fabricated to match the bolt spacing, orthe base plates may possibly be rotated on thecolumns. Correction methods are discussed in"Some Practical Aspects of Column Base Selec-tion.'' [5]

Case H i s t o r y . On a 20-story building in SanFrancisco, California, the steel erector surveyedthe as-built location of anchor bolts. Thecontractor's superintendent, John, was an "oldtimer" and took much pride in his work. Hecarefully explained to the surveyor, with his fore-men present, that he personally supervised theanchor bolt installation. All the bolts were at thecorrect elevation, were exactly spaced, and were"right on" the column lines. After the survey wascomplete, the surveyor reported the results toJohn, with his foremen present. The surveyorstated all the bolts were at the exact elevation,correctly spaced, and "right on" the columns lines.John smiled. But when the surveyor told him thebolts on column lines B2 and B3 were rotated 90degrees, his smile disappeared. And no matterhow he measured the bolts, they were still rotated90 degrees.

9

4. Inadequate Anchor Bolts for Column Erection

Problem

After reviewing the anchor bolt and column basedesign, the erector discovers the anchor bolt andbase plate design do not provide for adequateresistance to overturning of columns during erec-tion. This problem can occur when:

· Only two anchor bolts are provided, levelingplates are not used, and shims or wedges cannotbe placed under the base plate.

· The structural designer or detailer has not madeprovisions for the anchor bolts to resist lateralforces on the free-standing columns.

S o l u t i o n

Overturning of Column. After the column is seton a leveling plate, or on anchor bolt leveling nuts,or on shims, or on a base plate, the anchor bolt andbase plate design must be capable of resistingoverturning caused by lateral forces on the col-umn. The lateral forces may consist of wind, othersteel members striking the column, erection equip-ment striking the Column, or even ironworker con-nectors at the column top. Chapter 6, page 6-12,in the AISC Manual of Steel Construction, VolumeII, Connections, mentions overturning due to acci-dental collisions during erection. [11] Overturningis also discussed in "Some Practical Aspects ofColumn Selection." [5] Overturning is usually nota problem when the anchor bolts and column baseare designed to resist overturning and uplift frombuilding design loads.

Prevent the Problem. The best method to pre-vent the above problem is to perform proper plan-ning for anchor bolt and base plate design. Properplanning means:

· The erector lets the steel detailer know whatlateral loads the column base design must resist.A specified lateral load from any direction at thecolumn top is provided to handle wind or objectsstriking the column.

· The erector coordinates foundation constructionwith the general contractor to make certain shimsmay be placed under column bases with onlytwoanchor bolts when leveling plates are not used.

· The steel erector requests four-bolt anchor boltpatterns when leveling plates are not used. Thecolumn is then landed on four supporting levelingnuts. Shims under the base plate may also beadded to help resist overturning.

If proper planning is not performed, the steelerector may face a safety problem while erectingthe columns. The column may need to be guyed-off before the lifting line is released. But guys alsopresent another safety hazard because guys arenot easy to see and something may run into orstrike the guy. Steel struts similar to tilt-up wallstruts may be used. Struts present a less hazard-ous situation because they are easily seen andtake up less space.

Tall, unsupported columns may require an erec-tion engineer to analyze the column base (anchorbolts). For example, an airplane hangar had 90-foot high columns with trusses at the top. Thecolumn bases had multiple anchor bolts that tiedthe column base to the foundation. The columnswere 30 inches deep and 12 inches wide. The boltdesign provided adequate support in the strongdirection of the column, but inadequate support inthe weak direction. The steel erector solved theproblem by erecting a column "bent" consisting oftwo columns and the fill-in beams. This "bent"gave adequate resistance in the weak direction.The ironworkers still did not trust support in thestrong direction, so they added wire rope guys.After all, the ironworkers had to be at the columntop to connect the trusses.

Case History. Even with the proper column basedesign, the steel erector must still be cautious. Onone industrial building, the owner scheduled asmall ceremony for the first column erected. Thecolumn was set on four anchor bolt leveling nuts,the top nuts were tightened, and the column wasthen released from the lifting line. The columnpromptly fell over because the column had onlybeen tack-welded to the base plate. What a wayto start? Needless to say, the steel erector madea big impression at the ceremony.

5. One-Bolt Connections

Problem

While reviewing the design drawings, the erectordiscovers the structural designer has provided aconnection with no bolts, or with only one bolt.

Code Requirements. The Construction SafetyOrders, Section 1710(c)(1 ), states:

During the final placing of solid web struc-tural members, the load shall not be re-leased from the hoisting line until the mem-bers are secured with not less than twobolts, or the equivalent at each connectionto keep members from rolling and to sustainanticipated loads. Bolts shall be drawn upwrench tight. [13]

The term "solid web structural member" is in-tended to mean a beam, channel, girder, or evena column standing vertically connected at oneend. The two bolts are required to keep the beamfrom rolling and to sustain erection loads. Almostall bolted members are designed with at least twobolts just to take the design load. However, somewelded members may show no bolts.

Work Practices. Apart from the requirements ofSection 1710(c)(1), two bolts are also required toallow the ironworker connector to "connect" thebeam in a safe, quick, and economical manner.The ironworker will place the tapered shaft of aspud wrench in one bolt hole, place a bolt in thesecond bolt hole, and then be able to remove thespud wrench shaft to place the second bolt, if thesecond bolt is required. If only one bolt hole isprovided, the connector obviously cannot use thatbolt hole for both the connecting spud wrench anda bolt. Certain steel members can be erectedwithout any bolts, or with only one bolt. However,erection costs are increased because the membermust be held with the load line until the single boltcan be placed, or, in the case of no bolts, atemporary weld is made.

Tubes. Steel tubes, commonly used as bracingmembers in braced frames, may be shown on thedesign drawings without any erection bolts, or withonly one erection bolt. See the following twodetails for examples of this situation.

t II l i t

No Bolt

IIT IL

One Bolt

Solution

Provide for Two Bolts. The erector should makeprovisions in its estimate for at least two boltconnections on all members. During steel detail-ing, the erector should coordinate with the fabrica-tor, detailer, and structural designer to make pro-visions for the required two bolts.

Tube Bracing. Steel tube bracing memberspresent special problems to the erector. A typicaltube bracing design provides for a slotted end to fitover a gusset plate. The tube is then fillet-weldedto the plate. As mentioned under "Problem," thedesign drawings may show no bolts, or only onebolt to allow for erection of the tube.

The steel tube should not be subject to the provi-sions of Section 1710(c)(1 ) because it is not a solidweb member. Further, the slotted ends will keepthe tube from rolling when the load line is released.However, the ironworker connector still needs atleast two bolts at each end of the tube to safelymake the connection.

Erection Angles on Tubes. The following DetailA shows how one erector solves the two-boltproblem by using erection angles atthe ends of thetube. The two bolts in the erection angle at the topend of the tube allow the ironworker connector tosafely connect that end of the tube first. The twoslotted bolt holes in the connection angle at thebottom of the tube allow that end of the tube to beconnected with a spud wrench. This methodpresents the following problems:

· Long slots in the tube are difficult to make in theshop and difficult to fit-up and weld in the field.

· The tube is required to be erected by first posi-tioning the tube in the same vertical plane as thegusset plates and then swinging it in into posi-tion--a task not readily accomplished, if at all.

· Panel geometry may not allow the tube to beerected unless the tube angles, gusset plates,and tube slots are specially shaped and thebottom gusset plate is shipped loose.

Plates on Tubes. The following Detail B showshow structural engineer William C. Honeck solvesboth the two-bolt problem and difficult erection

problem by using plates shop-welded to the endsof the tube. This method has the following advan-tages:

· The fabricator makes a block and short slot ateach end of the tube instead of the difficult longslot.

· The difficult positioning of the long slot to thegusset plate is eliminated.

· The tube is easier to erect and can always beerected because it is simply brought in sideways.

Long Bolts. An alternate solution is to place twoerection bolts through the tube and gusset plate.This solution has problems because when thelong bolts are tightened to fit up the slot to thegusset plate, the tube sides may bend in.

Other Tube Connections. For other tube endconnections, see the article by Lawrence A. Kloibertitled, "Designing Architecturally Exposed SteelTubes," in the March 1993 issue of Modern SteelConstruction. [14] However, the one-boltconnec-tions illusl]'ated in that article are not recommended.

2

NOTES: 1. REQUEST APPROVAL FROM ENGINEER TOLET ANGLES REMAIN IN PLACE.

2. THIS DETAIL IS MEANT TO ILLUSTRATE THEUSE OF ANGLES ON THE ENDS OF THE TUBE.SEE COMMENTS IN THE "SOLUTION" FORPROBLEMS WITH THIS DETAIL,

•k

Z ERECTION BOLTS

/ ,

-/V l/

Z 3x3x 3,8 WITH TWO

LONG SLOTTED HOLES IN ANGLE

DETAIL AANGLES ON ENDS OF TUBE - SLOT IN TUBE

13

THIS DETAIL PRODUCES A VERY SMALL ECCENTRICITYTHAT CAUSES BENDING IN THE BRACING MEMBER,THIS BENDING SHOULD BE CONSIDERED IN THEDESIGN OF THE BRACE.

REGULAR HOLES FORTWO ERECTION BOLTS

TUBE PL

OPTIONALFIELD ORSHOP WELD

• • GUSSET PL

/

TUBE PLATE ON GL OF TUBE • •AND WORK GL

LONG SLOI-FED HOLES IN TUBE PLATEFOR TWO ERECTION BOLTS

DETAIL BPLATES ON ENDS OF TUBE

14

6. Columns or Bents Tied Together With Non-Bolted Steel Joists

Problem S o l u t i o n

The design drawings show columns or bents (par-tial steel frames) tied together with steel joists thathave welded end anchorages (no bolts). Thiscondition is unacceptable to the erector because:

· The Construction Safety Orders, Section1710(c)(3) states:

In steel framing, where bar joists are utilized,and columns are not framed in a least twodirections with structural steel members, abar joist shall be field-bolted at columns toprovide lateral stability during construction.[13]

· The welded connection provides no fit-up forspacing adjacent columns or frames.

· The Steel Joist Institute (SJI) requires bolted endanchorages for joists at column lines to providelateral stability during construction.

If the erector discovers column line joists withwelded end anchorages, the erector should:

· Condition its bid for bolted end anchorages.· Work with the detailer, fabricator, joist supplier,

and structural designer to provide bolted endanchorages.

If for some reason the column line joists aredelivered to the jobsite without bolted end anchor-ages, the erector must provide the required boltholes in the field.

The SJI Standard Specifications Load Tables andWeight Tables for Steel Joists and Joist Girders,and Technical Digest, No. 9, Handling and Erec-tion of Steel Joists and Joist Girders are mustreferences for joist design, fabrication, and erec-tion. [15, 16]

15

7. Steel Joists Without Bolted Bridging

Problem

Open web steel joists are furnished without boltedbridging required for proper and safe erection.

Code Requirements. The Construction SafetyOrders, Section 1710(c)(4) states:

Where Iongspan joists or trusses, 40 feet orlonger, are used rows of bridging shall beinstalled to provide lateral stability duringconstruction prior to slacking of hoistingline. [13]

Industry Procedures. The Steel Joist Institute's(SJI) Standard Specifications Load Tables andWeight Tables for Steel Joists and Joist Girdersgives various requirements for erecting joists. [15]For example, Section 6, "Handling and Erection,"for K-Series steel joists requires bolted diagonalbridging to be installed on certain joists before thehoisting cables are released. The SJI TechnicalDigest, No. 9, Handling and Erection of SteelJoists and Joist Girders, also discusses stability ofjoists and required bolted bridging. [16]

S o l u t i o n

Joist Design. The structural designer must becautious when designing steel joists or using pre-engineered joists. If the designer shows bridgingdetails, then care must be taken to follow thehandling and erection requirements of the SteelJoist Institute. The Institute's requirements meetthe requirements of the Construction Safety Or-ders.

The erector should review the design drawingsand work with the fabricator and joist supplier tomake certain that the required bolted bridging isfurnished.

Assemble Joists. The erector can assemblegroups of joists on the ground, complete withbridging, and erect the assembled group to standalone as a laterally stable unit. This method oferecting joists also solves the problem of erectorsworking on highly unstable joists. Section 6,"Handling and Erection," in Reference 15, alsostates:

When it is necessary for the erector to climbon the joists to install the bridging, extremecaution must be exercised since unbridgedjoists may exhibit some degree of instabilityunder the erector's weight.

Case History. On one project, a metal deckforeman happened to walk on the top chord of anewly erected joist that had no bridging installed.The joist moved laterally and the foreman fell off.The joist erector was following proper erectionprocedures, and had reviewed those procedureswith the metal deck contractor. The foreman hada momentary lapse of safety procedures. Thisexample illustrates that the required joist erectionprocedures are not to be taken lightly by thestructural designer or erector.

16

8. Columns or Bents Tied in With Timber

Problem

The structural designer produces a building de-sign that uses a combination of timber beams andsteel bents (partial steel frames) in order to reducecosts. The timber beams tie the steel bentstogether. The combined frame is usually laterallystabilized by horizontal and vertical plywood dia-phragms in the timber direction.

Erection Supports. The steel erector has theproblem of determining how to temporarily sup-port the steel bents. The steel framing is obviouslya non-self-supporting steel frame as specified inSection 7.9, 'q'emporary Support of StructuralSteel Frames," in the AISC Code of StandardPractice. [1] The erector must furnish adequatetemporary supports as required by the Code. Theerector is also governed by Section 1710(a), "Brac-ing,'' of the Construction Safety Orders. [13]

Solution

Designate in Contract. First of all, the structuraldesigner must realize the problems inherent in acombination design of steel frames and timber tie-in beams. Section 7.9.3 in the Code of StandardPractice states in part, "Such frames shall beclearly designated as 'non-self-supporting.'" [1 ] Ifthe structural designer does not make that state-ment in the contract documents, then the steelerector may make a claim against the owner.

All-Steel Frame. One solution to the temporarysupport problem is for the steel erector to ap-proach the fabricator, contractor, and structuraldesigner to replace the timber beams on thecolumn lines with steel beams. Then, at least theerector will have an all-steel frame that will beeasier and safer to temporarily support. Ofcourse,the best solution from the steel industry's view-point is to ask the structural designer to replace allthe timber beams with steel beams.

Support Methods. If the structural designercannot change or modify the design, then the steel

erector is faced with the problem of determininghow to erect the steel and furnish temporarysupports that provide the required lateral stabilitywith the least hazardous working conditions. Anymethod the erector chooses to erect the steel andtimber will present greater safety hazards than thehazards in erecting an all-steel frame.

Some methods the erector can follow are to:

1. Erect the steel bents supported in all directionsand then leave the jobsite. This solution presentsa hazardous condition because other trades mightrun into or remove the supports---especially if wirerope guys are used. Temporary horizontal steelstruts between the steel bents will allow the use ofless hazardous wire rope "X" bracing in lieu of theundesirable wire rope guys.

2. Work with the carpenters and erect the steelconcurrently with the timber beams. This methodpresents the hazards of two trades working to-gether, and one relying on the other--not the bestof conditions. Temporary supports will still berequired, and the ironworkers and other trades willprobably not end the project on the best of terms.

3. Use a combination of methods 1 and 2.

Case History. On a recent project, a combinationsteel bent and timber beam structure with fourlevels of steel was used. The erector chosemethod I above--erect the steel, guy it off, andleave the jobsite. The bents were supported withwire rope "X" bracing in the steel frame directionand wire rope guys in the timber beam direction. Inthe timber beam direction, the columns were guyed-off at three floor levels to anchors in the concretebasement floor. Guys at the third level were sosteep, their ability to prevent lateral displacementwas questionable. Fortunately, the frame did notcollapse. However, the carpenters had to con-stantly make adjustments to the plywood dia-phragms in order to keep the building plumb. Thequestion might be asked, "Would an all-steel framehave been more efficient and economical?"

9. Steel Columns or Partial Bents Not Tied In

Problem

The structural designer produces a building de-sign that uses a combination of steel and otherbuilding materials. Steel columns may be com-pletely tied in by timber or concrete, or partial steelbents may be tied in by concrete. A variety ofdesigns may exist, but all of them require tempo-rary supports by the steel erector.

Similar Problem. This problem is similar to theproblem, "Columns or Bents Tied in With Timber."But this problem presents a more hazardous con-struction condition because the steel is, for themost part, unsupported free-standing columnswith an irregular steel beam pattern.

Erection Supports. The steel erector has theproblem of determining how to temporarily sup-port the steel members. The steel members areobviously a non-self-supporting steel frame asspecified in Section 7.9, "Temporary Support ofStructural Steel Frames," in the AISC Code ofStandard Practice. [1] The erector must furnishadequate temporary supports as required by theCode. The erector is also governed by Section1710(a), "Bracing," of the Construction SafetyOrders. [13]

Solution

Designate in Contract. The structural designermust realize the problems inherent in a combina-tion design of steel and other materials. Section7.9.3 in the Code of Standard Practice states inpart, "Such frames shall be clearly designated as_non-self-supporting._" [1] Although the steelmembers are obviously non-self-supporting, thestructural designer must make a statement in thecontract documents that the frames are non-self-supporting, or the owner may be subject to a claim.

Hazardous Methods. The temporary supportsdetermined by the steel erector will present avarying degree of safety hazards depending onthe type of supports. One method of temporary

support is to guy-off the columns with wire ropeguys that are anchored to the concrete floor orconcrete footings. This solution presents an ex-tremely hazardous condition because the wirerope guys will interfere with construction opera-tions of the steel erector and the othertrades. If thewire rope guy is struck by construction equipmentor materials being hoisted, or if the wire rope guyis accidentally slacked-off by a worker who thinks,"It is in the way," a disastrous accident can occur.Such an accident did occur on a high-rise buildingin Toronto, Canada, when a wire rope guywas cutby another trade because it was in the way. Wirerope guys are also subject to a multitude of prob-lems that must be constantly monitored. Forexample, the wire rope clamps must be properlyplaced and checked to make certain they have notbeen loosened. Turnbuckles must also be con-stantly observed to make certain they have notbeen slacked-off or tampered with. Wire ropeguys may be the most economical and easiesttype of temporary support to install, but they presentthe most hazardous safety condition.

Another safer, temporary support is to providerigid struts from the steel members to the concretefloor or footings. Struts are more visible than wirerope guys and can take more physical abuse.

Case History. The steel erector should takeadvantage of adjacent existing structures to stabi-lize the steel being erected. For example, on oneproject 200-foot-long trusses were erected aroundthree sides of an existing hangar. On two sides ofthe hangar the new columns were temporarilybraced to the existing columns with angle frames.These frames:

· Stabilized the long free-standing columns.· Located the columns for vertical alignment.· Stabilized the truss bents until bottom chordmembers could be connected.

No wire rope guys were required, which made thesteel erector and the contractor very happy.

18

10. Non-Self-Supporting Steel Frames

Problem

The structural designer produces a building de-sign where the completed steel frame is not stable.Section 7.9.3 in the AISC Code of Standard Prac-tice defines this type of steel frame as a non-self-supporting steel frame. [1] The AISC definition is:

A non-self-supporting steel frame is onethat, when fully assembled and connected,requires interaction with other elements notclassified as Structural Steel to provide sta-bility and strength to resist loads for whichthe frame is designed.

Designate in Contract. Such frames are re-quired to be clearly designated as "non-self-sup-porting" in the contract documents. The Code ofStandard Practice defines contract documents tomean the contract, plans, and specifications. Thestructural designer must convey the "non-self-supporting" designation, preferably on the struc-tural drawings (plans). If the structural designerdoes not make such a designation on the draw-ings, then the owner may receive claims for extrawork from the steel erector and contractor. If thedrawings are not so designated and the steelerector does not realize the non-self-supportingcondition, and if a construction failure occurs, thenthe structural designer may wish the steel framehad been designed as a self-supporting frame.

New Code. The AISC recently issued a newversion of the Code of Standard Practice, effectiveJune 10, 1992. This version replaces the Septem-ber 1, 1986 version contained in the Manual ofSteel Construction. [6] Significant changes aremade to Section 7.9.3, "Non-Self-Supporting SteelFrames." Hopefully, these changes will alleviatecontroversies that resulted from varied interpreta-tions of language in the September 1, 1986 ver-sion.

Erector Furnishes Supports. The steel erectoris required to furnish and install temporary sup-ports for the erection operation for both self-sup-porting and non-self-supporting steel frames. SeeSection 1710 of the Construction Safety Orders,and Section 7.9 of the AISC Code of StandardPractice. [13, 1] For many erectors, furnishingtemporary supports for self-supporting frames is adifficult task. Furnishing supports for a non-self-

supporting frame may tax the resources of theerector. Then if the non-self-supporting frame isnot designated as such in the contract documents,and the erector does not realize this condition untilwork is started, the erector may have extremedifficulty in erecting the frame.

S o l u t i o n

Designate on Drawings. The most obvioussolution, and the course of action required by steelindustry practice, is for the structural designer todesignate non-self-supporting frames in the con-tract documents. See page 26 of "Structural SteelConstruction in the '90s," in Steel TIPS. [17] If the"non-self-supporting" designation is made on thedrawings, erectors will be able to determine duringthe bidding or negotiating period if they can copewith the problems presented by such frames.

Analyze Frames. As a second line of defense, theerector might be wise to use the services of anerection engineer to analyze any suspicious-look-ing frames. Even the most experienced erectorsmay miss the fact that a frame is non-self-support-ing when that designation is not made in thecontract documents. Section 1710(b) in the Con-struction Safety Orders, requires a civil engineercurrently registered in California to prepare anerection plan for trusses and beams over 25 feetlong. [13] Hopefully, the engineer would discoverthat the frame is non-self-supporting.

Examples. Some examples of non-self-support-ing frames are:

· Concrete shear walls that attach to a non-mo-ment steel frame--after the steel is erected.

· Column line beams that need metal deck forlateral support to carry axial or vertical loads--and the deck is not in place.

· Floor framing that needs metal deck to transferhorizontal loads--and the metal deck is not inplace.

· Roof trusses that help provide lateral stability byframe action--but the bottom chords cannot beconnected until all¥oof loads are applied.

· Tilt-up walls attached to the non-self-supportingsteel framo and the walls have no lateral sup-port. See Section 7.9.3 in the Commentary onthe Code of Standard Practice. [2]

19

11. Column Splices Too Low or Too High Above Floor

Problem

On one tier building, the column splices are de-signed at 6'-0" above the top of steel. On anothertier building, the splices are designed at 3'-6"above the top of steel. The 6'-0" splices are toohigh to allow the connectors, bolters, and weldersto work without scaffolding or floats. The 3'-6"splices are not high enough to allow safety wirerope attachments for exposed floor edges at theperiphery of the building or at interior floor open-ings.

S o l u t i o n

Splice Design. Designthecolumnsplices atleast4'-0" above the top of steel. This height will:

· Allow attachments for the top safety wire rope tobe placed on the column. The attachment for thetop wire rope needs to be located to provide thecorrect height for both the erector and contractor,if the contractor wants to use the wire ropeinstalled by the erector without moving the wirerope.

Column attachments for the safety wire rope needto be placed so the wire rope is located between 42

and 45 inches above design finish floor height asrequired by Section 1710(e)(3) of the ConstructionSafety Orders. [13] The 4'-0" splice meets thisheight requirement for most cases. The determin-ing factor is the floor thickness. If the floor is toothick, the height of the column splice should beincreased. The 4'-0' height is recommended inChapter 6, page 6-19, of the Manual of SteelConstruction, Volume II, Connections, and byBarry L. Barger in "What Design Engineers CanDo to Reduce Fabrication Costs." [11, 12]

· Allow the erectors, bolters, and welders to work *without scaffolding or floats. The article, "ValueEngineering and Steel Economy," by David T.Ricker, in Steel TIPS, discusses splices that aretoo high. [18]

· Provide for uniformity in shipping, unloading,sorting, and erecting columns. If column splicesare designed at different heights above the floorelevation on the same floor, or are designed withthe same tiers spliced at different floors, thenerection costs will increase.

Erector Requests. The structural designer shouldconsider requests from the erector to increase ordecrease the designed column splice heights.

20

12. Columns Interrupted by Beams

Problem

On a two-floor shopping center building, the col-umns, rather than being one continuous piecefrom the base plate to the roof, are interrupted bythe beam framing. The structural designer hasused the interrupted-column-framing system toutilize continuous, supported beams.

Suspended Beams. In addition to thecontinuousbeams, the design utilizes cantilevers with sus-pended beams between the two cantilevers. Seeelevation sketch below. This type of design in-creases erection and plumbing costs even morethan just continuous beams because the bentunits must be plumbed individually to allow thesuspended beams to be erected.

More Difficult Erection. The interrupted columns willmake steel erection more difficult and more costlybecause:

I • SUSPENDED

ii ii/ 1II II

U H

BEAMS

I I

Elevation

Vibration. Continuous beam framing, especiallywith cantilevers, may produce a design with ex-cessive vibration. This vibration is not really an

erection problem, but the ironworkers willnotice and comment on the vibration. And

I surely, if the ironworkers feel the vibration,the tenants will also feel the vibration.

Solution

In this particular case, the steel erectormust work with the design presented.However, on future projects the structuraldesigner should realize the interrupted-column design will increase the erector'scost. Any savings visualized by usingcontinuous beams may be negated by the

· More pieces are required to be erected.· The columns are more difficult to plumb and keepplumb.

· The complete frame is more difficult to plumb.· The sequence of and direction of erection maybe limited.

increased erection cost. The structural designermay want to perform a brief value engineeringexercise on using full-length columns versus inter-rupted columns.

21

13. Columns Offset From Beam Framing

Problem

On a tier building, some of the columns are offsetfrom the beam framing grid line. See sketchbelow. This offset will present erecting and deck-ing problems to the steel erector.

OFFSETmB

TJ

T

F F•

FLOOR PLAN

Solution

If possible, the structural designer should arrangethe framing so the columns and beams are tiedtogether on the main column lines without offsets.Keeping the framing on common column linesallows for more efficient loading, erecting, anddecking procedures. Also, lateral loads from erec-tion equipment are more easilytransmitted throughthe floor framing system.

22

14. Revisions and Alternates Not Flagged on Drawings

Problem Solution

Design drawings are issued without revisions high-lighted, marked, or flagged to clearly indicate therevisions. The fabricator and erector do not noticethe revisions. During construction, the structuraldesigner, contractor, or owner asks, "Why is thatdoor framing there?," or in an extreme case, "Isn'tthe weld on those box columns too small?"orDuring bidding, the bid form and specificationsrequest and describe alternates, but the drawingsdo not clearly indicate the alternates. As a result,the fabricator and erector miss the scope of analternate. During construction, the structural de-signer, contractor, or owner asks, "Where is eleva-tor No. 6 going to fit?."

Indicate on Drawings. The structural designermust clearly indicate revisions and alternates onthe design drawings by:

· Using the standard symbol for a revision.

· Placing a "cloud" around the revision or alter-nate, and identifying the cloud with the revisionsymbol or alternate number.

· Using some other highlighting or flagging methodto show the revision or alternate.

By Fabricator and Erector. The fabricator anderector must follow the above practice wheneverthey make revisions to their shop, erection, anderection scheme drawings.

Flagging. "Flagging" revisions is discussed byBob Petroski, Eugene Miller, and David T. Rickerin the article, "What Design Engineers Can Do toReduce Fabrication Costs," in Steel TIPS. [12]

23

15. Double-Framed Beam Connections to Girder

P r o b l e m

If two opposing beams, each with double framingangles, connect to the same girder and sharecommon bolt holes, an erection safety hazardexists. This type of connection is shown in DetailA • below. Detail A---4 is shown on page 5 of

L

DOUBLE FRAMING ANGLESSHOP AND FIELD BOLTED

, , , A - - 4 - - .Relative Cost

1.05

Whereas the previous connections of this series have employedsingle shear elements, A-4 is the standard connection consisting ofdouble framing angles which are both shop and field bolted. TheRela•ve Cost Index of A-4 is 5% above the single tab shear baseconnection A-l, but large beam loading could influence the eco-nomics and use this connection relative to A-1 because of anincrease in weld size. There is a safety hazard in erection whenusing this connection. Placing pins and bolts while tnjing to aligntwo opposing beams through common holes may require the addi-tion of seat angles on one or both sides of the girder to keep thebeam in position. Eliminating this hazard, as required by OSHAlaws, will add additional cost to this connection.

Steel Connections/Details and Relative Costs.[19] Note: Both the detail and complete accompa-nying comments are shown. Portions of the com-ments regard relative costs for both shop and field,may refer to a detail sequence, and may not applyto the subject matter of this problem. However, thecomplete comments are shown because the rela-tive costs should be of interest to most readers.This note also applies to details in subsequentproblems that are taken from Steel Connections/Details and Relative Costs.The hazard exists because the ironworker mustremove the bolts from the first beam connected, inorder to connect the second beam. Once the bolts

are removed, the connection no longer complieswith the requirements of Section 1710(c)(1 ) of theConstruction Safely Orders. [13] This sectionrequires each end of a beam to be secured with notless than two bolts before the hoisting line isreleased.

S o l u t i o n

To avoid this hazardous connection, design theconnection as shown in Detail A--1 on page 4 ofSteel Connections/Details and Relative Costs.[19] Connection Detail A - - l , shown below, usessingle shear tabs (plates) shop-welded to thecarrying girder and field-bolted to the beams.

. - . f , .

t

SHOP WELDED TAB-FIELD H.S. BOLTED

= . . A - - 1 . . ,Relative Cost

1.00

Connection A-1 is the most economical for this series of shear con-nections and is assigned a Relative Cost Index of 1.00. This connec-tion employs a single shear tab shop welded to the carrying girderand field bblted to the beam.

Detail A--1 provides a more economical connec-tion than Detail A--4, because it provides for safererection, faster erection, and better ironworkermorale. As stated byW. A. Thornton in Steel TIPS,"As this example illustrates, single angles will workeven in heavy industrial applications, and they aremuch less expensive than double angles, espe-cially for erection." [20]

24

16. Double-Framed Beam Connections to Column Web

Problem

If two opposing beams, each with double framingangles, connect to the same column web andshare common bolt holes, an erection safety haz-ard exists. Additionally, beam erection and boltaccess is difficult. This type of connection is

shown in Details BW--4 and BW--5 below. Thesedetails are shown on page 9 of SteelConnections/Details and Relative Costs (Steel TIPS). [19]

1 · RETURN

1SHOP WELDED ANGLES TO BEAM

H.S. BOLTED TO COLUMN WEBDOUBLE ANGLES

SHOP AND FIELD H.S. BOLTED

--- BW--4-- - ,,-,,BW--5 = · =Relative Cost Relative Cost

1.20 1.30

Double angle connections BW-4 and BW-5 have relative costs of 1.20 and 1.30. The shop-welded angles areslightly less. Installation of these connections is hazardous because of the difficulty in placing pins or erectionbolts through common holes. Addition of angle seats under the beams may be necessary to keep the beams fromfalling. The relative costs of BW-4 and BW-5 will then be even higher than those noted. Use of connections BW-4 and BW-5 may not be possible at columns with moment connections to the flanges because continuity platesor stiffeners, as shown in the "CF" series connections, would interfere with entry of the beam. A design engineermay wish to use connections similar to BW-1 or BW-2 to avoid this problem as well as to take advantage of theobvious economies.

25

The hazard exists because the ironworker mustremove the bolts from the first beam connected inorder to connect the second beam. Once the boltsare removed, the connection no longer complieswith Section 1710(c)(1) of the Construction SafetyOrders. [13] This section requires each end of abeam to be secured with not less than two boltsbefore the hoisting line is released.

S o l u t i o n

To avoid this hazardous connection, design theconnection as shown in Detail BW--1 on page 8 ofSteel Connections/Details and Relative Costs (SteelTIPS). [19] Connection Detail BW--1, shown be-low, uses single shear tabs (plates) and horizontalstiffener plates shop-welded to the column with thesingle shear plates field-bolted to the beams.Detail BW--1 provides a more economical connec-tion than Details BW--4 or BW--5, because itprovides for safer erection, faster and easier erec-tion, easy bolt accessibility, and better ironworkermorale.

COL. FLG.

SHOP WELDED TAB AND PLATESFIELD H.S. BOLTED

, , ,BW--1 , , ,Relative Cost

1.00

For simple shear connection to column web the base 1.00 indexconnection BW-1 has a single vertical plate welded to the columnweb with horizontal stiffener plates (normally 1/2" thick) welded atits top and bottom. The bolt holes are located outside the toe of thecolumn flanges, which allows for easy erection entry of the beam aswell as accessibility for impacting the high strength bolts.

26

17. Mixed Bolts

Problem

The structural drawings show a mixed "bag ofbolts" throughout the structure. Different kinds ofbolts shown include:

· A325 bearing bolts in single-plate shear connec-tions for the connections of fill-in beams. Someof the connections require a snug-tight conditionof the bolts to prevent moment transfer. Otherconnections allow snug-tight or fully-tightenedbolts.

· A325 slip-critical bolts and A490 slip-critical boltsfor beam-to-column web connections at the samecolumn work point.

· A325 slip-critical bolts and A490 slip-critical boltsfor bracing connections at the same work point.

Bolt Design on Most Projects. The majority ofprojects are designed with only one kind of bolt--fully-tightened A325 bolts. Designing for differentkinds of bolts requires additional quality control,with resulting added cost, to prevent the erectorfrom installing the wrong kind of bolt. Additionalquality control includes the following actions:

· The fabricator (or erector) must prepare an erec-tion drawing that shows--in addition to the boltdiameter and length---whether the bolt is A325,A490, slip-critical (fully-tightened), bearing (snug-tight or fully-tightened), or bearing (snug-tightonly).

· The erector must not only distribute A325 andA490 bolts of the correct diameter and length tothe work points, but must make certain that theA325 and A490 bolts are installed in the correctconnection at a work point.

· The erector must set up procedures and checksto make certain that bearing bolts required to besnug-tight are not accidentally fully-tightened.

· The inspector must set up procedures to deter-mine that each kind of bolt is properly installedand tightened.

S o l u t i o n

Bolt Design. The possibility of the erector usingthe wrong kind of bolt can be reduced or elimi-nated, and costs reduced, if:

· A325 and A490 bolts are not used at the sameconnection point.

· The use of A490 bolts is limited to similar connec-tions throughout the job--say all 36-inch-deepbeams, or all bracing connections.

· The single-plate shear connections are designedto allow fully-tightened bearing bolts. This designassumes some transfer of moment is allowed.Fully-tightened bolts should be allowed becauseallowable loads for single-plate shear connec-tions as tabulated in Table X on page 4-52 in theManual of Steel Construction are based on fully-tightened or snug-tight bearing bolts. [6]

Steel erectors have discovered that the differencein cost of installing snug-tight bearing bolts, fully-tightened bearing bolts, and slip-critical bolts (fully-tightened) is not distinguishable. Let's look at theinstallation requirements for bearing bolts. Sec-tion 8(c), "Joint Assembly and Tightening of Shear/Bearing Connections," in the "Specification forStructural Joints Using ASTM A325 or A490 Bolts,"in the Manual of Steel Construction states:

Bolts in connections.., shall be installed inproperly aligned holes, but need only betightened to the snug tight condition. Thesnug tight condition is defined as the tight-ness that exists when all plies in a joint arein firm contact. This may be attained by afew impacts of an impact wrench or the fulleffort of a man using an ordinary spudwrench. [6]

So after figuring out which bolts are bearing bolts,the ironworker now has a choice of using the fulleffort of a spud wrench or a few impacts of animpact wrench. The choice is obvious. Theironworker will use the impact wrench, and prob-ably fully tighten the bolts, whether or not the boltsneed full tightening.

Bolt Uniformity. As stated by David T. Ricker, in"What Design Engineers Can Do to Reduce Fab-rication Costs," in Steel TIPS:

Bolt Uniformity. Minimizing the number ofdiameters and types of bolts on a given joblessens the chance for a mixup in the shopor field... [12]

27

18. Mixed Diameter Bolts

Problem

The structural drawings show various bolt diam-eters. The different diameters of bolts increasesthe chance for the wrong bolts to be supplied orinstalled. Additionally, installation cost is increaseddue to added quality control, more supervision,more tools, and tool changes.

Solution

Bolt Uniformity. The structural designer shouldbe aware that different diameters of bolts will addto the fabrication and bolting cost. As stated byDavid T. Ricker in "What Design Engineers CanDo to Reduce Fabrication Costs," in Steel TIPS:

Bolt Uniformity. Minimizing the number ofdiameters and types of bolts on a given joblessens the chance for a mixup in the shopor field and allows more efficiency in drillingor punching operations. [12]

Minimize Number of Diameters. If structuraldrawings require several diameters of bolts, theerector should work with the fabricator and struc-tural designer to minimize the number of diam-eters to be used. For example:

· Replace large-diameter machine boits withsmaller-diameter A325 bolts to match other A325bolt diameters.

· Keep the A325 bolt diameters the same by usingeither more or less bolts.

· Limit the number of bolt diameters. Instead ofusing 3/4-inch, 7/8-inch, 1 -inch, and 11/B-inch diam-eters, try to use just 7/8-inch and 1 -inch diameters.

· Avoid using large-diameter A490 bolts. 13/8-inchand 11/2-inch diameter A490 bolts require bigger,heavier, and more costly equipment to tightenthe bolts. Some erectors do not have this equip-ment. Further, the ironworkers certainly don'tlike to use the heavy equipment.

19. Reuse of High-Strength Bolts

Problem

To correct alignment of exterior beams connectedwith A325 slip-critical bolts, the erector loosensand retightens some bolts and loosens, removes,reinstalls, and retightens other bolts. However,the inspector and engineer claim that retighteningthe bolts constitutes reuse of the bolts, and theyrequest that the bolts be replaced.

Solution

Reuse of A325 Bolts. The "Specification forStructural Joints Using ASTM A325 or A490 Bolts"(Specification) in Part 5 of the Manual of Steel

Construction, prohibits the reuse of A490 boltsand galvanized A325 bolts, but allows the reuse ofother A325 bolts, if approved by the responsibleengineer. [6]

The steel erector should bring to the attention ofthe inspector and engineer Section 8(e), page 5-276, "Reuse of Bolts," in the Specification. TheSpecification, along with the AISC recommenda-tions on page 17 in Quality Criteria andlnspectionStandards (AISC publication S323), should allowthe erector to obtain approval from the engineerfor the reuse of A325 bolts. [6, 7]

The "Steel Interchange" feature in Modern SteelConstruction, March 1992, contains an excellentdiscussion on the reuse of non-galvanized A325bolts. [21]

28

20. Prequalified and Non-Prequalified Weld Joints

Problem

Both prequalified weld joints and non-prequalifiedweld joints are used in the structure. Either thestructural designer designs a connection with anon-prequalified weld joint that requires a quali-fied-by-test weld joint, or the erector decides that,for cost considerations, a qualified-by-test joint ismore appropriate than a prequalified weld joint.When problems occur using the qualified-by-testjoint, or even the prequalified joint, a finger-point-ing contest is sometimes generated, and correc-tive action is required.

Solution

By Welding Code. The article, "Welded Joints -Requirements," in Part 4, page 4-152, of theManual of Steel Construction states in part:

AWS prequalification of a weld joint is basedupon experience that sound weld metal withappropriate mechanical properties can bedeposited, provided work is performed inaccordance with all applicable provisions ofthe Structural Welding Code. [6]

Design with Prequalified Joints. So the firstessential step for a sound weld is to design con-nections that can use prequalified weld joints.These joints are shown in Part 4 of the Manual ofSteel Construction, and in Section 2 of the Struc-tural Welding Code. [6, 22]

Use Prequalified Joints. The second essentialstep is for the steel erector to use prequalified weldjoints at the connections, and to follow all therequired procedures.

Qualified-By-Test Joints. If prequalified weldjoints are not used, either by necessity or bychoice, the third essential step is to use a qualified-by-test weld joint. The AWS Structural WeldingCode sets forth the requirements for testing andqualifying non-prequalified weld joints. [22]

Take Precautions. The fourth essential steprequires the steel erector to take precautions whilewelding, and not take the attitude that a qualifiedjoint--prequalified or non-prequalified--will pro-duce a successful weld. As further stated in thearticle quoted above, a successful weld also re-quires attention to:

· The magnitude, type, and distribution of forces tobe transmitted.

· Accessibility.· Restraint to weld metal contraction. See the

problem, "Restrained Welded Joints."· Thickness of connected material.· Effect of residual welding stresses on connected

material.· Distortion.

The articles, "Avoiding Weld Defects," "CorrectingWeld Defects," "Nondestructive Testing (NDT),"and "Projects Specifications," contained in "Struc-tural Steel Construction in the '90s," in Steel TIPS,contain much valuable information on producingsuccessful welds. [17]

Welding Procedure. The essential step, andone that is often overlooked, is for the erector toproduce a complete and comprehensive weldingprocedure for each project. The welding proce-dure should include:

· A weld sequence for both the complete frameand the individual joint. The joint sequenceshould include when beam-to-column web jointsare tightened, if the webs are bolted.

· The prequalified and qualified-by-test joint weld-ing procedures.

· A requirement that only certified welders may beused, and that they must be certified for theprocess used and the weld position. A weld jointmay be properly designed, be prequalified, andbe thoroughly planned, but the success of theweld produced depends on a certified and dedi-cated ironworker making the weld.

29

21. Extending Continuity Plate for Back-up Bar

Problem

In certain beam-to-column web welded momentconnections, the back-up bar for the flange weldfouls on the column flanges.

Solution

Plate Design. To provide adequate clearancesfor back-up bars, design the connection with con-tinuity plates extended beyond the column flanges.See Detail DW--1, on page 12 of Steel Connec-tions/Details and Relative Costs (Steel TIPS). [19]Detail DW--1 and "Note" also discuss correctwelding of the continuity plate. For convenience,a modified Detail DW--1 is shown below.

Extending the continuity plate is also recommendedon pages 4-11 and 6-55 in the AISC Manual ofSteel Construction, Volume II, Connections. [11]

Fabricator or Erector Requests. Ifthe structuraldesigner has not provided for an extended conti-nuity plate, the fabricator or erector will probablyrequest the plate to be extended. The structuraldesigner should grant that request.

T&B

/-T- tE

FLANGE > tx,

II

- - EXTENSION

WEB BOLTED - FLANGE BUTT WELDED

30

22. Welded Connections to Inside of Column

P r o b l e m

The structural drawings show beam-to-columnweb connections made with field welds inside thecolumn flange areas. See Details BW--3 and

DW--4 below. Some of these welds are difficult tomake because of electrode positioning, equip-ment access, welder access, and welder visibility.

NON-MOMENT CONNECTION M O M E N T C O N N E C T I O N

I t lIIOPTIONAL

SHOP WELDED SEAT- FIELD WELDED TO BEAM

- - = B W - - 3 = = =Relative Cost

1.09

The extra connection pieces as well as the drilling of holes throughthe beam flange add to the cost of this connection. If the columnhas moment connections to its flange with column stiffeners, theuse of this connection may be prohibited as in the cases of connec-tions BW-4 and BW-5.

1" TYP.

, . • - 1 • IF REQ'D.

EA. SIDETO COL. FLG.

•- NO TAPER

OPTIONALTRIM LINE

WELDED MOMENT PLATES WITH SEAT

. . . D W - - 4 . . =Relative Cost

1.50

Connection 0W-4, which is all welded, is not popu-lar because of its high relative cost compared withthe first two connections in this Plate prepa-ration and the full penelTation welding of flangeplates to the column results in an increase of therelative cost to 50% over base connection 0W-1.

31

Solution

To avoid the above problems, make the beam-to-column web connections as shown in DetailsB W - - 1 and D W - - 1 below. The fabricator anderector should work with the structural designer tochange the undesirable details to the desirabledetails.

N O N - M O M E N T C O N N E C T I O N M O M E N T C O N N E C T I O N

) COL. FLG.

SHOP WELDED TAB AND PLATESFIELD H.S. BOLTED

,,,,. BW--1 ,,-,,Relative Cost

1.00

For simple shear connecUon to column web the base 1.00 indexconnection BW-1 has a single vertical plate welded to the columnweb with horizontal stiffener plates (normally 1/2" thick) welded atits top and bottom. The bolt holes are located outside the toe of thecolumn flanges, which allows for easy erection entry of the beam aswell as accessibility for impacting the high strength bolts.

T. & B. FLANGE

- E '1I

i

!

MI

I

/+

1

WEB BOLTED- FLANGE BUTT WELDED

. . . DW--1 . . .Relative Cost

1.00

DW-1 is the base 1.00 index connection andemploys a bolted vertical web extension plate.Note that only fillet welds are necessary for thever'dcal web plate. Flanges are folly welded to thecontinuity plates.

All the above details are from Steel Connections/Details and Relative Costs (Steel TIPS). [19]

32

23. Restrained Welded Joints

Problem

In beam-to-column flange moment connections,the most economical and most common designuses welded flanges and a high-strength boltedweb with ' • bolts. This connection isshown in Detail CF--1 on page 10 of Steel Con-nections/Details and Relative Costs (Steel TIPS).[19] Detail CF--1 is shown below.

Problems may occur on large beams with thickflanges and deep webs. If the web bolts aretightened before the welds are made (the mostdesired erection sequence), then the welds will berestrained by the bolts while cooling, which couldresult in lamellar tearing of the column flange, orcracked welds.

CF--1

T. & B. FLG. F--2

WEB BOLTED- FLANGE BUTT WELDED

· ==CF--1 =,, , ,=CF--2 , , ,Relative Cost Relative Cost

1.00 1.06

For this category of connecUon, the beam-to-column moment connection CF-1 is the base Rela-live Cost Index 1.00 connection, with a singleshear plate being fillet welded to the columnflange. Beam flanges are fully welded to thecolumn flange, providing a very ductile and eco-nomical moment connection. Attaching the sheartab to the column with a full penetration weldrather than a double fillet weld increases the rela-•ve cost 6%.

Solution

Acceptable Procedure. For most beam flanges,the structural designer should allow the web boltsto be tightened before the welds are made. Thisprocedure is acceptable because:

· While the welds are cooling, the shrinkage forcein the weld will overcome the allowable load onthe bolts. The bolts will slip horizontally and gointo bearing. After the weld has cooled, the boltswill not slip again.

· After the weld is made, the bolts will still act asslip-critical bolts--as designed.

Special Procedures. For beams with too manyweb bolts, the weld shrinkage force will not be ableto overcome the allowable bolt load. Specialdesign and erection procedures should be fol-lowed, because the weld area must be allowed toshrink. Additionally, "snugged-up" bolts may notbe able to be tightened after welding because thebolts will bind as the weld shrinks and preventproper tightening. Two methods can be used tosolve the problem:

· Keep the design of bolted webs. Provide hori-zontal slotted holes in the column shear plate forweld shrinkage. Bolts are then fully-tensionedafter the flange welds are made.

· Change the design to welded webs. Someerectors use horizontal slotted holes in the col-umn shear plate for standard bolts. Other erec-tors use standard holes in the shear plate anduse erection bolts. After the flange welds aremade, the web is then welded to the column asshown in Detail CF---4, on page 11 of SteelConnections/Details and Relative Costs (SteelTIPS). [19] The web weld is restrained by thewelded flanges. However, since the weld size ismuch smaller than the flange welds and distrib-uted over a larger area of the column flange,lamellar tearing or a cracked weld should notoccur if proper welding techniques are used.

Welding Techniques. Proper welding techniquesincluding preheat, peening, postheat, controlledcooling, and electrode selection will help to avoiddefects in restrained welds. For information onrestrained welded joints see:

33

· "Avoiding Weld Defects," on page 14 of "Struc-tural Steel Construction in the '90s," in SteelTIPS. [17]

· Page 4-152 in the Manual of Steel Construction.[6]

· "Commentary on Highly Restrained Welded Con-nections,'' AISC Engineering Journal. [23]

Records. The structural designer may require theerector to provide proof that webs can be boltedbefore successful flange welds are made. Recordsof past experiences will be helpful to provide therequired proof. The records will be available if theerector has made welding procedures for priorprojects that include a welding sequence wherethe webs are bolted before the flange welds aremade.

34

24. Field-Welded Curb Angles

P r o b l e m

The structural drawings show curb angles (or bentplates) field-welded to periphery beams with over-head welds. See design detail below. Theseoverhead welds are costly and require the welderto work on the exterior of the building--a safetyhazard not only to the welder, but to workers andothers below the welder.

I

I

V

· •' • A325 SC

•HOLESIN BEAM@P

Design Detail

Solution

Tolerances. Field-adjustment of curb angles isnecessary when the alignment of the angles re-quires limits closer than the normal steel framealignment tolerances specified in Sections 7.11.3.1and 7.11.3.2 in the Code of Standard Practice. [1]When alignment of the angles is allowed to followthe normal steel frame alignment, then the anglesare shop-welded. Tolerances for adjustable itemsare specified in Section 7.11.3.3 of the Code. Donot expect the steel erector to adjust the angles toa "zero tolerance."

The alignment of these adjustable items requiresan adjustable connection to accommodate mill,fabrication, and erection tolerances. See the lastparagraph on page 48 of the Commentary on theCode of Standard Practice. [2]

Field Attachment. Two methods of field-attach-ing the angles to provide adjustment and to avoidthe overhead welds are:

. Field-bolting. Space bolts as required.

· Field-welding with slotted plug welds near thetoe of the beam flange. Space welds as required.

See details below for these suggested two attach-ment methods.

J

/•L VOP!

iN PL Or ANGLE

NOTE: P=CENTER TO CENTERSPACING

Suggested Bolting Detail

@p• • 1 • . L VOP

' t '

! I

Suggested Welding Detail

35

25. Steel Floor Deck Spanning Uneven Surfaces

Problem

While placing the steel floor deck, the steel deckcontractor can not make the deck bear on adjacentsupports. This condition exists when:

· Fill-in beams or trusses with large camber areadjacent to column line beams or trusses withmuch smaller camber.

· Beams, trusses, or joists with large cambers areadjacent to deck shelf angles attached to con-crete walls.

The elevation differential of adjacent supports istoo great to allow the steel deck to deflect and bearon each support. See following elevation:

The saw cut is made to the top surface and verticalsurfaces of the ribs, but not the bottom surfacebearing on the beam. The resulting gap is tapedto contain the wet concrete. As the concrete ispoured, the fill-in beams will deflect and the gapmay close.

Note: The structural designer usually designs thedeck to span continuous over at least two supportsto take advantage of deck continuity over multiplesupports. This continuity reduces moment anddeflections in the deck. Before the deck is cut, thestructural designer must be notified.

FILL IN

STEEL FLOOR DECK 2

Deck Not Bearing

J • GAP, /-F

Solution

Practical Solution. A practical, and probably theonly solution, is to saw-cut the deck at the support(s)adjacent to the support that is not bearing. Thedeck will then change from a cantilevered to asimple span. See following elevation:

The taping of gaps at butted ends is found onpage 16, Article 4.3, "Lapped and Butted

Ends," in the Design Manual forComposite Decks, Form

Decks and RoofDecks. [24]

COLUMN LINE BEAM ORCONCRETE WALL WITH Roof Deck.SHELF ANGLE The installa-

tion of steelroof deck ondi f ferent ia lwarped sur-

faces is discussed in the January 1992 issue ofSteel TIPS, titled, "Steel Deck Construction." [25]

FILL

STEEL FLOOR DECK2 •SAW CUT

Deck Bearing

COLUMN LINE BEAM ORCONCRETE WALL WITHSHELF ANGLE

36

26. Project Specifications

Problem

At times the specifications may:

· Be vague.· Include implied statements.· Include requirements inappropriate to the project.· Be more restrictivethan necessaryfor the project.

For example, plumbing requirements that aremore restrictive than specified in the Code ofStandard Practice. [1]

· Require fabricator to complete design in order tomake a bid. If so, the erector must also makeassumptions.

· Conflict with the drawings or with notes andspecifications on the drawings. Note: In Califor-nia, the structural designers typically place speci-fication-type notes on the drawings.

· Not be written for the specific project.· Assign work to the steel fabricator, erector, mis-

cellaneous metal contractor, etc.

Solution

Avoiding Specification Problems. The fabrica-tor and erector must live with and comply withspecifications and drawings developed by thestructural designer. To avoid specification prob-lems, the structural designer should:

· Either prepare the specifications following theConstruction Specifications Institute's (CSI)Manual of Practice, or coordinate structural steelrequirements with the specification writer whenthe project has a specification writer. [26] Hope-fully, the specification writer will follow the CSIformat.

· Make certain specification-type notes placed onthe structural drawings agree with the structuralsteel specification section.

· Follow the specification requirements set forth inSection 3, "Plans and Specifications," in theCode of Standard Practice, and the checklistcontained in Section 3 in the Commentary on theCode of Standard Practice. [1,2]

· Review the structural steel specification sugges-tions in "What Design Engineers Can Do toReduce Fabrication Costs," and in "Value Engi-neering and Steel Economy," in Steel TIPS. [12,18] However, items 11 and 12 in "Value Engi-neering and Steel Economy" may be a littlemisleading. Specification writers should not as-sign work to subcontractors because the specifi-cations are normally directed to the general con-tractor. Instead, all of the required work anditems to be furnished should be specified in theappropriate specification section.

· Make certain the drawings show items requiredby the specifications. For example, if the speci-fications state, "Construction limits for erectionequipment are shown on Drawing S-6," then theconstruction limits must be shown on that draw-ing.

· Include Charpy requirements for Groups 4 and 5rolled shapes that require full penetration welds.See "Heavy Structural Shapes in Tension Appli-cations,'' in Steel TIPS. [27]

Specifications on Jobsite. Specification writersand structural designers are sometimes disturbedto discover the steel erector is not using thespecifications or structural drawings to erect thesteel. The specification writer and structural de-signer should realize the shop drawings, erectiondrawings, bolt lists, welding procedures, and some-times erection equipment used by the steel erectorare all developed from, are based on, and areextensions of the specifications and drawings.The steel erector's field crews will use thesedocuments to erect the steel, and not the specifi-cations and drawings prepared by the structuraldesigner.

37

Reference List

1. Code of Standard Practice for Steel Buildingsand Bridges, AISC, Chicago, June 10, 1992.

. Commentary on the Code of Standard Practicefor Steel Buildings and Bridges, AISC, Chicago,June 10, 1992.

3. Detailing for Steel Construction, AISC, Chicago,1983.

. David T. Ricker, "Steel Interchange," ModernSteel Construction, AISC, Chicago, January

p. 9.

. David T. Ricker, "Some Practical Aspects ofColumn Base Selection," Steel Design GuideSeries 1: Column Base Plates, AISC, Chicago,1990, 43-51.

6. Manual of Steel Construction: Allowable StressDesign, 9th ed., AISC, Chicago, 1989.

7. Quality Criteria and Inspection Standards, 3ded., AISC, Chicago, 1988.

. Vijay P. Khasat, "Steel Interchange," ModernSteel Construction, AISC, Chicago, May 1993,p. 10.

. David T. Ricker, "Steel Interchange," ModernSteel Construction, AISC, Chicago, July 1993,p. 9.

10. Thomas C. Powell, "Steel Interchange," ModernSteel Construction, AISC, Chicago, December1992, p. 12.

11. Manual of Steel Construction, Vol. II,Connections, AISC, Chicago, 1992.

12. "What Design Engineers Can Do to ReduceFabrication Costs," Steel TIPS, Structural SteelEducational Council, Moraga, California, June1992 (Printed from Modern Steel Construction,February 1992).and"What Design Engineers Can Do to ReduceFabrication Costs," Modern Steel Construction,AISC, Chicago, February 1992, 28-33.

13.

1 4 .

1 5 .

1 6 .

17.

1 8 .

1 9 .

20.

21.

Article 29, "Erection and Construction," CALlOSHA State of California Construction SafetyOrders, BNI Books, Los Angeles, June 1989, p.244.

Lawrence A. Kloiber, "Designing ArchitecturallyExposed Steel Tubes," Modern SteelConstruction, AISC, Chicago, March 1993, 30-38.

Catalog of Standard Specifications Load Tablesand Weight Tables for Steel Joists and JoistGirders, Steel Joist Institute, Myrtle Beach,South Carolina, 1992.

Technical Digest, No. 9, Handling and Erectionof Steel Joists and Joist Girders, Steel JoistInstitute, Myrtle Beach, South Carolina, 1992.

F. Robert Preece and Alvaro L. Collin,"Structural Steel Construction in the '90s," SteelTIPS, Structural Steel Education Council,Walnut Creek, California, September, 1991.David T. Ricker, "Value Engineering and SteelEconomy," Steel TIPS, Structural SteelEducational Council, Moraga, California, August1992 (Printed from Modern Steel Construction,February 1992).andDavid T. Ricker, "Value Engineering and SteelEconomy," Modern Steel Construction, AISC,Chicago, February 1992, 22-26.

Steel Connections/Details and Relative Costs,(Steel TIPS), The Steel Committee of California,Walnut Creek, California, 1986.

W. A. Thornton, Ph.D., P.E., "Designing for CostEfficient Fabrication," Steel TIPS, StructuralSteel Educational Council, Moraga, California,April 1992 (Printed from Modern SteelConstruction, February 1992).andW. A. Thornton, Ph.D., P.E., "Designing for CostEfficient Fabrication," Modern SteelConstruction, AISC, Chicago, February 1992,12-20.

"Steel Interchange," Modern Steel Construction,AISC, Chicago, March 1992, p. 10.

38

22. Structural Welding Code--Steel (D1.1), AWS,Miami, 1992.

23. "Commentary on Highly Restrained WeldedConnections," AISC Engineering Journal,Vol. 10, No. 3, 3d Quarter 1973, 61-73.

24. "SDI Specifications and Commentary forComposite Steel Floor Deck," Design Manualfor Composite Decks, Form Decks and RoofDecks (Publication No.26), Steel Deck Institute,Inc., Canton, Ohio, 1987, 14-21.

25. "Steel Deck Construction," Steel TIPS,Structural Steel Educational Council, Moraga,California, January 1992.

26. Manual of Practice, The ConstructionSpecifications Institute, Alexandria, Virginia.

27. "Heavy Structural Shapes in TensionApplications," Steel TIPS, Structural SteelEducational Council, Moraga, California,October 1993.

About the author

James J. Putkey is a consulting civil engineer in Orinda, California.He received a BCE degree from the University of Santa Clara in1954. After two years in the U.S. Army, 19 years with the ErectionDepartment of Bethlehem Steel Corporation--Pacific Coast Divi-sion, and seven years with the University of California--Office of thePresident, he started his own consulting business. He has providedconsulting services to owners, contractors, attorneys, and steelerectors for the past 12 years.

39

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