STRUCTURAL STEEL EDUCATIONAL COUNCIL

TECHNICAL INFORMATION & PRODUCT SERVICE

JUNE 1992

What Design Engineers Can DoTo Reduce Fabrication Costs

This Tips was printed from an article that appeared inthe AISC magazine "Modern Steel Construction." Acomplimentary subscription to "Modern SteelConstruction" may be obtained by contacting AISC,Chicago.

Bill Dyker, manager of engineering, and JohnD. Smith, vice president of sales, with AISC-member Garbe Iron Works, Inc., Aurora, IL:

When welding base plates to columns in theshop or field, designs should not show "all-around",illet welds unless the weld is required to resist amoment or a large uplift. Usually, welds as shown onPage 4-130 of the AISC Manual of Steel Construc-tion, ASD--Ninth Edition are adequate. Similar con-sideration should be given to attaching cap plates tocolumns.

Designs, espe-cially CAD generatedissues--should bereviewed to ascertainthat all pieces can beerected without unduerestraints Also, the re-viewer should be alertto avoiding framingconditions that causedeep copes at theends of beams. This

A compilation ofcomments fromexperienced fabricators acrossthe country

Avoid framing conditions that causedeep copes at the ends of beams.The cost for a few extra pounds ofsteel per foot for a deeper beamoften will be easily offset by the

savings from not having to designand fabricate special connections

and cope reinforcements.

solution occurs especially when relatively shallowbeams support deep beams and both beams may ormay not be at the same elevation. The cost for a fewextra pounds of steel per foot for a deeper beamoften will be easily offset by the savings from nothaving to design and fabricate special connectionsand cope reinforcements.

If beam-column moment connections requiredoubler plates in the column web, consider increas-

ing the column size to eliminate the need for suchplates. The costs to design, detail, approve andfabricate doubler plates could be offset by the costof a heavier column.

Designs should not arbitrarily call for stiffenersin webs of columns at moment connections. Withthe variety of computer programs available, (e.g.AISC's CONXPRT program), the designer should

be able to describeon the drawings whichcolumns require stiff-eners and the stiffenersizes. Again, perhapsa slight increase in theunit weight of a col-umn would offset allthe costs--detailingthrough fabrication--associated with webstiffeners. Thesecosts really begin to

escalate when doubler plates are needed along withstiffeners. Further complicating the situation andadding to costs is when connections must be pro-vided for beams attaching to column webs in thevicinity of stiffeners.

Designers should not arbitrarily call for beamconnections that virtually fill the "T" distance ofbeam webs when lesser connections will accom-modate the loads.

Partial Penetration Groove Weld Full Penetration Groove Weld

iTotal Cost Per Weld

$145Total Cost Per Weld

$350

Amount of weld in partial-penetration weld calculated using ,it/6 + 1/8.Costs include: preparation; root pass; backup bar or back gouge;

cleaning of welds between passes; cut-off of run-out tab;weld material; and inspection.

Average wage rates calculated at $60/hr.

Source: Drawings courtesy of Garbe Iron Works; calculations courtesy of American Bridge

When designers run into an uncommon framingcondition, they should consult a fabricator for ideason how to solve the problem.

Designers should not call for A325-SC boltsunless they are meeting the criteria for the use ofsuch bolts as listed in the ASTM A325 Specification.In its publications, AISC is placing more emphasison using bearing type connections. This will bereflected in the forthcoming revised EngineeringFor Steel Construction.

Galvanizing should be limited to members whoseexposure to the elements could result in structurefailure from excessive rusting and/or where paintingis impractical. Whether or not it is the intent ofMasterspec, its wording in regards to galvanizingcalls for pieces to be galvanized which do not fit theaforementioned conditions. Galvanized steel re-quires special fabrication and has an inherentlyhigher cost.

Designers should not arbitrarily includeMasterspec or other standard specification sectionsin the design documents, as many times suchsections conflict with the drawings. Similarly, whendesigners prepare their standard details and jobnotes, they should present information pertinent tothe project. Standard job notes should be updatedperiodically to reflect current industry practice.

Keep base plates and column sizes as uniformas possible without grossly oversizing.

Do not specify high strength steel "here andthere"--keep it in groups, e.g. "columns" or "maingirders."

Keep connections, angles, and plates as stan-dard as possible with the fabricator allowed tochoose bolted or welded.

Show steel plainly on structural drawings with-out blending it into the architectural design.

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Thomas Schlafly, Director of FabricatingOperations & Standards, AISC:

A few sample connections should be sized atthe same time that beams are sized to avoid prob-lems such as requiring more bolts than the connec-tion can handle.

Consider and note construction tolerances ondesign drawings and provide adjustments in appro-priate details. For example, make embedded plates6" to 8" larger than the beam and connect with longslots to accommo-date concrete toler-ances. This will al-low the steel to re-main in plumb evenif the concrete isslightly off and willsimplify curtainwallerection. Another ex-ample would be to put curb plates on in the field orto provide other means of adjustment.

Shade the pieces coming out of the page insketches to catch interferences and difficulties withmembers in the "third" dimension.

A good rule of thumb to remember is that themore pieces in a detail, the more expensive it is tofabricate. Also, apound of weldmentis worth about $30to $60. Likewise, ex-pansion joints arevery expensive andshould be avoided ifpossible.

Rafters shouldbe run up hip roofsrather than horizontally, if possible, because thegeometry is much simpler.

Larry L. Mednick, president, with AISC-member Globe Iron Construction Co., Inc.,Norfolk, VA:

Structural and architectural drawings should becoordinated so they agree (e.g. on details anddimensions).

Develop details that work to minimize the re-quired coordination between trades, such as thosefound in AISC's Load and Resistance Factor De-sign of Simple Shear Connections and AllowableStress Design of Simple Shear Connections (formore information, call 312/670-2400 ext. 433).

Try not to use a lot of different sizesections to save a small amount ofsteel. It may cost more to buy and

track the different section sizes thanis saved by the reduced weight.

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Don't hesitate to ask a fabricator for alternateconnection types and details that work best andminimize costs and still meet AISC-accepted proce-dures.

Bob Petroski, P.E., vice president/generalmanager/chief engineer with AISC-memberHercules Steel Co., Inc., Fayetteville, NC:

We sometimes find big discrepancies betweenwhere the architect and the engineer show steel. Itis very important that drawings be coordinated

dimensionally be-tween the architectand engineer.

Too many ad-denda in the jobstage create head-aches for the fabri-cator. We like to seea current set of draw-

ings when the job is issued; not a bid set of drawingswith a series of addenda.

Engineers need to be realistic when it comes towelding. Don't call for full penetration welds if they'renot needed. Don't call for continuous welds if youcan use intermediate welds. Remember, whenthere's a lot of welding on light pieces, it can result

Incomplete design drawings shouldnot be released simply to meet aschedule. In the long run, it will

cause more delays as the fabricatoris forced to check the design.

in distortion.Engineers should

show non-typical con-nections on the draw-ings so all fabricatorsare bidding on thesame design.

I don't believe inusing a lot of differentsize sections to save

a minimal amount of steel. It sometimes costs moreto buy and track the different section sizes than issaved by the reduced weight.

Eugene Miller, retired structural engineer,formerly with AISC-member American BridgeCo. and AiSC-member Trinity Industries,Houston:

Don't call for full penetration welds when partialor fillet welds will do the job.

Incomplete design drawings should not be re-leased simply to meet a schedule. In the long run, itwill cause more delays as the fabricator is forced tocheck the designs and the detailer has to stop andask questions.

Steel Tips June 1992 3

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Designers should consult with fabricators whenusing a special type of weldment.

When design drawings are revised, the changesshould be properly highlighted on a design docu-ment, rather than presented in sketch form.

Computers shouldn't have the last word in theselection of member sizes. Designs should be prag-matically reviewed to avoid ill-working solutions,such as where a W31 frames into a W12.

Designers should write specifications for indi-vidual projects rather than simply using hurriedlyadopted off-the-shelf specs.

Barry L. Barger, Vice President-Production,AISC-member Southern Iron Works, Inc.,Springfield, VA: (these comments are excerptedfrom his paper, "Practical Engineering In ShopFabrication And Erection--How It Can Benefit TheOwner," presented at the 1991 National SteelConstruction Conference)

Noted below are items typically shown or notedon contract drawings that severely limit or prohibit afull range of connections or may force the exclusiveuse of framing angles even if the fabricator isallowed to choose thetypes of simple shearconnections for aproject. In all in-stances, the problemcan simply be over-come by showing therequired reaction forthe members on thecontract drawings:· Requiring 7/8"-

Tubes and pipes make economicalcolumn members. They are an

excellent choice when stiffness aboutboth axes is required. And they have

less surface area than equivalentwide flange members.

diameter bolts when 3/4"-diameter are sufficient.· Requiring uniformly loaded beams to carry 125%

of the end reaction.· Using friction bolts (slip-critical) when bearing

bolts are adequate.· Specifying the minimum number of double rows

of bolts for each section size.· Listing unrealistically high reaction multiplication

factors on composite beams.While it must be remembered that the engineer

of record is at liberty to be as conservative as hewishes, the above requirements will always signifi-cantly add to the project's cost and may not be in thebest interest of the owner.

I would also like to give a few tips that may eithermake a job go easier and avoid problems. Most of

them are just simple common sense, but are oftenforgotten.· For erection stability, if using leveling nuts, do not

use less than four anchor bolts.· Place column splices 4' above the top of steel so

that perimeter safety cables may be attachedbefore the next floor is erected.

· If skewed hole patterns are required, try to skewthem in the connection material rather than themain member.

· When a job is designed in A572 Grade 50, list thesmall beams (W8xl0, etc.) that can use A36 sothe fabricator can take them from stock.

· If making last minute changes, design in A36 sothat material may be located quickly from ware-houses.

· Stop stiffeners shortwhere you can so they do nothave to be fitted.

David T, Flicker, retired structural engineer,formerly with AISC-member The Berlin SteelConstruction Co,, Inc,, Berlin, CT:

Tubes and pipes make economical columnmembers. They are an excellent choice when stiff-

ness about both axesis required.

They can be usedas hollow members orfilled with concreteHowever, there is nogreat advantage to fill-ing small tubes or pipewith concrete. ATS3x3x1/4 x 10' hasa capacity of 37 kips

when filled with concrete and 33 kips when unfilled.For larger columns, there is an advantage, though.For example, a pipe 8" standard column 12' long hasa capacity when filled with 3,000 psi concrete of 217kips, whereas the unfilled capacity is only 155 kips.

Hollow structural sections have a number ofadvantages over wide flange shapes:· Tubes and pipes have less surface area than

equivalent wide flange members. For example,listed here for comparison are the surface areasper linear foot of three common sizes:

W8x31 = 3.89 sq. ftTS8x8x1/4 = 2.65 sq. ftpipe 8 std = 2.26 sq. ft

This can be a significant cost factor if the mem-bers require an exotic surface coating or fire proofing.

4 Steel Tips June 1992

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Tube Connections

· Tubes offer excellent resistance to torsional forcesand can be used to support eccentric loads suchas relieving angles for brick veneer, stone, orprecast concrete.

· Tubes also make efficient bracing members. Theyalso can be combined with other structural shapesto produce some startling aesthetic effects.

· In recent years, tube and pipe prices have be-come more competitive. Availability, however, issometimes a questionmark--a fabricator or sup-plier should be consulted.

Flagging Changes. Changes on all plans andshop drawings issued subsequent to the date of thecontract should be flagged so that revisions can beeasily located. Designers, fabricators and erectorsalike should observe this suggestion.

Tolerances. It is essential that erected toleracesare compatible with systems and materials beingsupported by the steel frame so that adjustment forthe trades that follow is possible. The publishedfabrication and erection tolerances will usually ac-complish this. However, if special tolerances arerequired, they must be clearly indicated on theplans.

Multiple details. Shop bolting and welding onthe same beam increases material handling, animportant element in fabrication cost.

Fillet welds. If possible, fillet welds should be5/16" maximum, or a size that can be made in onepass. Oversized welds add unnecessarily to thecost of fabrication and erection and also may causedistortion.

Bolt uniformity. Minimizing the number of di-ameters and types of bolts on a given job lessensthe chance for a mixup in the shop or field and allowsmore efficiency in drilling or punching operations.

Anchor bolts. The possibility of foundationerrors will be reduced when the fewest anchor boltand base plates sizes are used and when anchorbolt spacing is kept uniform throughout the job.

Partial depth stiffeners. Consider using par-tial-depth beam and column stiffeners where theyare adequate rather than full-depth fitted stiffeners.

Composite beams. To make composite beamseconomical, at least 6 to 7 lbs. of total beam weightper stud should be saved.

Relieving angles. The thickness of relievingangles is normally 5/16" or 3/8". If calculationsindicate a greater thickness than this, the basicdesign assumptions should be reviewed and per-haps a different approach attempted.

Odd sections. Before specifying odd sections,the designer should contact a local fabricator todetermine their availability.

Steel Tips June 1992 5

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