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David T. Ricker
Value Engineering
and Steel Economy
Author
David T. Ricker graduated from the
University of Connecticut in 1951
with a Bachelor of Science degree
in Civil engineering. The following
12 years he was with American
Bridge, except for military service.
In 1963, he joined The Berlin Steel
Construction Co., Inc. and has
served as chief draftsman, chief
engineer and currently as vice
president-engineering.
Ricker, active in AISC, ASCE and
SSFNE, lectures periodically before
these organizations and at several
schools and universities. He has
authored numerous articles on the
practical aspects of structural steel
fabrication and erection. He is a
member of the AISC Committee on
Manuals, Textbooks and Codes and
the ASCE Committee on Design of
Steel Building Structures.
39-1
Summary
If the structural steel fabricating industry is to survive and thrive, it
must stay competitive in the
market-place. The cost of fabricated
steel depends to a great extent on
what the fabricator is required to do
to the raw steel shapes and how he
does it. Erectability is another significant factor in determining the
cost of steel construction.
This lecture will concentrate on
the designer's role in creating a
safe, economical structure for his
client. In addition to such obvious
cost savers as the elimination of
overhead field welding and unnecessary stiffeners, there are many
additional ways to enhance the
value of the steel work. Quite often,
a seemingly innocuous decision
during the design stage can increase the steel quotations by thousands of dollars. If the designer is
aware of cost-saving methods of
steel construction, his client benefits in the long run. Sometimes, this
may be the deciding factor in the
selection of steel over competing
materials.
This lecture provides tips for economical steel construction and
alerts designers to recent trends in
design presentation resulting in
huge increases in steel estimating
costs.
© 2003 by American Institute of Steel Construction, Inc. All rights reserved.
This publication or any part thereof must not be reproduced in any form without permission of the publisher.
VALUE ENGINEERING AND STEEL ECONOMY
By David T. Ricker, P. E.
Vice President - Engineering
The Berlin Steel Construction Company, Inc.
Berlin, Connecticut
Designers who regularly practice value engineering consistantly
create the best value for their client. There are things which the
client can do for himself such as picking the right designer for
his project, clearly stating his goals and requirements, not
changing is mind, and allowing ample time for design and
construction. There are also things which a fabricator/erector
can do to cut construction costs. But the party with the greatest
impact on the economic success of the project is the designer.
Not only are the interests of the client directly in his hands but
he also has a tremendous influence on the caliber of performance and
monetary rewards of the other members of the construction team.
Listed here are a number of things which a designer can do to
enhance his design posture and assure that all parties concerned
benefit from the construction project.
1.
First, any designer who works in steel should take
advantage of steel's many strong points:
a.
Good weight-to-strength ratio.
b.
The efficiency of off-site preassembly.
c.
Speed of delivery and erection.
d.
Steel is readily available, can be stock piled and stored.
e.
Steel has strength in three directions.
f. Steel is elastic, versatile, and durable.
g.
Maintains its strength after heating and yielding.
h.
Steel is easily worked.
i.
Steel structures can be added to, subtracted from,
altered, and reinforced to adapt to use changes.
j.
Steel is compatible with other building materials.
k.
Steel is easily inspected.
l.
Steel design is user friendly.
2.
A designer should keep current on the costs of the various
steel products he prescribes. Attached to this article is a
list of mill extras expressed as a percent of increase above
the base price of the steel at the mill. (Figure 1.) A steel
fabricator can supply current base prices. The designers
should be aware of where the money is spent on steel
construction - 50% on material, 20% on shop costs, 20% in
erection, and 10% on other items such as drawings, painting,
and shipping.
3.
A designer should take advantage of allowable stress increases
permitted by AISC Specification 1.5.6 for temporary loads such
as earthquake and wind.
4.
Consideration should be given to the use of partial
composite design of floor beams - something in the range of 50%
39-2
to 75%. Full composite design is inefficient. The cost of one
shear stud in place equals the cost of approximately 7 pounds
of steel. Unless this ratio can be attained the addition of
more studs will prove uneconomical.
5.
Take advantage of live-load reductions if governing codes
permit.
6.
Select a proper mix of A36 and high strength steels. High
strength steels are advantageous when strength is the major
design criteria. High strength steel (A572 Gr 50) is about
13% more costly than A36 steel but over 35% stronger. When
deflection, stiffness, or some other serviceability criteria
governs, the nod will often go to A36 steel because the heavier
sections required will generally have a higher moment of
inertia.
7.
Select optimum bay lengths. An exhaustive study by John Ruddy,
P.E. (AISC Engineering Journal Vol. 20 #3, 1983) indicated that
a rectangular bay with a length-to-width ratio of approximately
1.25 to 1.50 was the most efficient. The filler members should
span in the long direction with girder beams in the short
direction. (Figure 2)
8.
Tailor the surface preparation and painting requirements to the
project conditions - do not underdo nor overdo the coating
requirements.
9.
Show all necessary loads on the design drawing to avoid costly
overdesigning of connections or dangerous underdesigning. This
is an AISC specification requirement.
10.
Indicate who is responsible for "grey area" items such as loose
lintels, masonry anchors, elevator sill angles, elevator
sheeve beams, fastenings for precast concrete spandel panels,
etc. Unless the responsibility is specifically delegated it is
likely that the cost of these items will be included in the
bids of 2 or more subcontractors, meaning the client may
pay more than once for the same article.
11.
Don't require the steel subcontractor to perform work that
should be done by other trades such as installing masonry
anchors, ceiling hangars, lateral bracing for interior walls,
toilet partition supports, window wall supports, and the like.
Information required to perform this work is often slow to
develop resulting in needless delay for the steel fabricator.
The most efficient steel jobs are those on which the steel
fabricator/erector is allowed to concentrate on the steel
framework while unencumbered by the intricacies pertinent to
the other trades. This reduces coordination requirements, and
allows the steel framework to be turned over to the other
trades in far less time that would otherwise be possible.
12.
Consider the use of cantilevered rafters and purlins to save
weight on roof design. (Figure 3.)
39-3
© 2003 by American Institute of Steel Construction, Inc. All rights reserved.
This publication or any part thereof must not be reproduced in any form without permission of the publisher.
13.
Do not design for minimum weight alone. Such a design may
require more pieces and more connections and will be more
labor intensive in both the shop and the field.
14.
Excessively stringent mill fabrication and erection
tolerances, beyond state-of-the-art construction practices,
will probably reduce the number of bidders and raise the cost
to the owner. ASTM A6 tolerances and those established by the
AWS and AISC have served the industry well and should be
adhered to except under extraordinary circumstances where some
special condition would dictate a more strict treatment.
15.
Designate the proper type of high strength bolt value. The
correct application of each type is well documented in the
current bolt specifications. Do not specify "friction" value
for the purpose of obtaining an extra factor of safety.
16.
Allow the use of tension control (twist-off) high strength
bolts. These bolts are as reliable as are other methods of
measuring bolt tension and save labor costs.
17.
Where possible specify fillet welds rather than groove welds.
Groove welds are more costly because of the joint preparation
required and the generally greater volume of weld. (Figure 4.)
18.
Use single pass welds where possible.
19.
Favor the horizontal and flat welding positions. These welds
are easier and quicker to make and are generally of a higher
quality. (Figure 5.)
20.
Don't call for more weld than is necessary. Overwelding
creates excessive heat which may contribute to warping and
shrinkage of the members resulting in costly straightening
expense.
21.
Grant the fabricator the option of eliminating some column
splices. The cost of one column splice equals the cost of
about 500# of A36 steel. The fabricator should study the
situation carefully before he decides to omit the column splice
and run the heavier shaft up to the next splice - the resulting
column may be too long for safe erection.
22.
Avoid designing column splices at mid-story height. These are
often too high for the erector to reach without rigging a float
or scaffold. If the splice can be located no higher than 5'-0
above the tops of the steel beams it will save the expense of
the extra rigging and still be in a region of the column where
bending forces are relatively low. (Figure 6.)
23.
Do not design column splices to "develop the full bending
strength of the governing column size". Seldom is the splice
located at the point of maximum bending and seldom do the
bending stresses result in a condition which would require a
full strength splice. The column has axial compressive
39-4
© 2003 by American Institute of Steel Construction, Inc. All rights reserved.
This publication or any part thereof must not be reproduced in any form without permission of the publisher.
stresses. The excess capacity is allotted to bending stresses
which occur as compression in one flange and tension in the
the other flange. The compression forces are added to each
other at one flange while at the other flange the tension force
is subtracted from the compression force. Seldom does this
other side of the column ever go into tension and never into
full allowable tension of the magnitude that would require a
full strength splice. Thus, there is little justification for
ever requiring a full strength column splice. (Figure 6.)
24.
Consider using a heavier column shaft or using a high strength
steel to eliminate the need for web doubler plates and/or
column stiffeners opposite the flanges of moment connected
beams. One pair of stiffeners installed costs approximately
the same as 250# of A36 steel if the stiffeners are fillet
welded. If they must be groove welded the cost skyrockets to
the equivalent of 1000# of A36 steel. The cost of one
installed doubler plate is about the same as 325# of A36 steel.
(Figure 7.) Considering that for an average two-floor column
there could be as many as 4 pair of stiffeners and 2 doubler
plates, at least 1750# of A36 steel (about 1550# of A572 Gr. 50
steel) could be sacrificed in order to save the time and
expense of making the lighter shaft work. The value engineering should be done by the designer in such cases.
25.
Avoid designing heavy or awkward members in remote hard to
reach portions of the structure. This may eliminate the need
for larger more expensive hoisting equipment.
26.
Reinforce beam web penetrations only where necessary. The
United States Steel Co. has prepared design aid booklets ADUSS
27-8532-01 and ADUSS 27-8482-02 which help to identify web
penetrations which require reinforcing and also the amount of
reinforcing necessary. It may be less costly to use a beam
with a heavier web, to move the opening to a less critical
location, or to change the proportions of the opening to something less demanding. In any event, the value engineering
should be done by the designer. (Figure 8.)
27.
For heavy bracing, where possible, translate the bracing work
points so that they lie on the intersection of the flange faces
rather than the centerline of members. (Figure 9.) Generally
this will result in a more compact, efficient connection.
(See article by William Thornton in the AISC Engineering
Journal - Vol. 21, 3rd Quarter 1984.)
28.
Allow the prudent use of oversized holes and slots to facilitate fit-up and erection. They may eliminate or reduce the need
for costly reaming of holes or refabrication.
29.
Specify that connection material be made of A36 steel including
such items as column base plates and beam moment connection
material even if the main members are of high strength steel.
Allow the option of using high strength steel if the fabricator
desires.
39-5
© 2003 by American Institute of Steel Construction, Inc. All rights reserved.
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30.
Avoid calling for the indiscriminate use of stiffeners.
Stiffeners are required to prevent local deformation or to
transfer load from one part of a member to another. (Figure
10.) If the main members are capable of taking care of themselves then the cost of stiffeners can be saved.
31.
Avoid odd sections which may not be readily available or which
are seldom rolled. These could result in costly delays.
32.
In areas of roof which are subject to snow drift loading
arrange the purlins parallel to the drift and vary the spacing
of the purlins so the same gage of roof deck can be used
throughout. (Figure 11.)
33.
Space floor beams so as to avoid the necessity for shoring
during the concrete pour. The cost of shoring is relatively
expensive and can easily be offset by varying the span, gage,
or depth of the floor deck.
34.
Avoid the "catch-all"
like this: "Fabricate
necessary to complete
undoubtedly be padded
This is unfair to the
35.
Avoid the "nebulous" specification which calls for stiffeners
as required, roof frames as required, reinforcing of beam web
penetrations as required, etc., etc. The fabricator/erector
rarely has enough time to find out what is and what is not
required therefore he will include in the bid an allowance for
the questionable items whether or not they are eventually
needed. Thus the client again coughs up the cost of something
that may never be supplied. This is one reason why it is
advantageous to all parties to make the design as complete as
possible.
36.
Avoid the overly restrictive specification. The more
restrictions listed in the steel specifications the greater
the chances that no one will be able to meet them all. This
will eliminate some of the competition and often result in
higher bids.
specification which reads something
and erect all steel shown or implied
the steel framework." The bids will
to cover whatever might be "implied".
client.
When value engineering is performed by the designer the cost savings
benefits go mainly to the client in the form of lower bids. When
the value engineering is done by the fabricator/erector the cost
savings is shared with the client, sometimes!
* * * * * * * *
STEEL JOIST ECONOMY
The key to economical steel joist design is "standardization". Open
web steel joists were originally conceived as single span members
carrying uniform loads and as such they are at their best. Joists
39-6
© 2003 by American Institute of Steel Construction, Inc. All rights reserved.
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are a standard product with relatively few variables. Departure
from the standard will generally increase the cost of the joist.
The following list of "do nots" will reveal some of these cost
risers.
1.
2.
Do not specify non-standard joist depths.
Do not call for non-parallel chords for "H" & "K" series
joists.
3.
Do not specify severe top-chord slope for long span joists
and joist girders.
4.
Do not call for clip angles, brackets, or any such superficial
attachments to be attached to the joist by the manufacturer as
this would disrupt the normal handling and shipping system.
5.
Do not specify non-standard camber.
6.
Do not specify a special joist paint, surface preparation, or
method of paint application.
7.
Do not specify a special paint color other than the standard
brownish-red or grey.
8.
Do not prescribe a special paint thickness.
9.
Do not specify special chord or web sizes.
10. Do not call for a special web profile.
11. Do not specify special material. The Steel Joist Institute
(SJI) specification permits a broad range of acceptable
material.
12. Do not stipulate hot rolled or cold rolled material to the
exclusion of the other. The SJI specification permits both
types.
13. Do not prohibit or limit the number of joist chord splices, or
to restrict the splice locations, or to require that the splice
be made in a particular manner. The SJI prescribes splicing
procedures which have passed the test of time.
14. Do not call for holes in highly stressed portions of joist
chords.
15. Do not call for joist top chord extensions to be too long or
too heavily loaded.
16. Do not call for concentrated loads on joists which are beyond
their capacity to resist. The SJI has established maximum
limits.
17. Do not specify bottom bearing joists if underslung ends will
suffice.
18. Do not call for cross-bridging where the SJI specification
permits the use of horizontal bridging.
19. Do not specify that the joist welds be made using a special
weld process or electrode.
20. Do not indicate "ceiling extensions" if the ceiling is "hung"
below the joist.
21. Do not require that modest concentrated loads be delivered at
a panel point. A joist top chord is designed to support a
400# load anywhere between panel points in addition to the
normal uniform load.
Attention paid to these small items will result in substantial joist
economy.
39-7
© 2003 by American Institute of Steel Construction, Inc. All rights reserved.
This publication or any part thereof must not be reproduced in any form without permission of the publisher.
There are other ways to realize cost savings in joist construction.
Sometimes it is less expensive to use a heavier joist if it reduces
the bridging requirements. (Figure 12.) Bridging installation is
very labor intensive. For example, a 12K1 joist 17'-0 long requires
2 lines of bridging whereas a 12K3 joist of the same length requires
only 1 line of bridging. This is a 50% reduction in bridging and
the cost of the heavier joist is only about $3.00 more.
When a span is so short as to make it impractical or impossible to
use an open web joist, a joist substitute can be used, such as
angles, channels, small wideflange, tubes or combinations thereof.
Figure 13 shows limits for minimum lengths of short joists. Figure
14 shows some of the shapes which can be utilized as "short joists".
* * * * * * *
METAL DECK ECONOMY
Formed metal deck for floors and roofs plays a significant role in
steel building construction. There are enough variables in deck
design to make it important for designers to put the right
combination together so that the client will receive full value.
Listed here are some of the variables.
1.
2.
3.
4.
5.
Type: roof deck, floor form
Profile: narrow, intermediate, wide
Depth
Gage.
6.
7.
Side laps.
End laps,
8.
Finish.
9.
Span, stress, and
deflection.
Fastening Systems.
Roof Deck
Roof deck is available generally in 1-1/2" and 3" depths, (special
deeper deck is available from a few manufacturers), in gages from 16
ga. through 22 ga., and with painted, G60 galvanized, or G90
galvanized finishes. Roof deck is available in accoustic and
non-accoustic styles, with or without cells. Three profiles are
available - narrow, intermediate, and wide-rib. Side laps are
either nestable or interlocking. (Figure 15.) Deck ends are
usually overlapped for a minimum of 2". Die set (swaged) ends were
offered at one time as an aid to deck nesting but modern deck
profiles are such that this is no longer necessary. In fact, there
are distinct disadvantages affecting the erectability of deck panels
which have die set ends. The span is important because it has a
direct effect on several other deck properties, namely the profile,
gage, depth, stress, and deflection limits.
Narrow rib deck is so inefficient that it is seldom used.
Intermediate-rib deck is less expensive, generally, than wide-rib
deck. (Intermediate deck is offered in 24 ga. by some
manufacturers.) For a given span and gage, wide-rib is stronger
than intermediate-rib which, in turn, is stronger than narrow-rib
roof deck. As a rule thick deck costs more than thin deck all
things being equal, and 3" deck costs more than 1-1/2" roof deck.
39-8
© 2003 by American Institute of Steel Construction, Inc. All rights reserved.
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Generally G90 galvanized deck costs more than G60 galvanized deck
which, in turn, costs more than painted roof deck. Some deck
manufacturers offer other finishes such as electro-galvanized,
phosphorized, and galvanized/painted, which may be cost-affective.
On occasion a manufacturer may offer a special price on a certain
type of finish. The availability of the specified product should be
checked prior to finalizing the deck selection.
This brings up a pertinent point. Often specifications are written
listing several acceptable deck manufacturers. As some of you have
no doubt found out, the deck industry is very volatile. Not only do
deck companies come and go, but the products they offer are apt to
vary from time-to-time. Also, some companies only market their
product in certain parts of the nation. It is nearly impossible for
a designer to keep track of all the changes. It is perhaps more
effective merely to stipulate that the deck manufacturer must be a
member in good standing of the Steel Deck Institute (SDI) or to
prove in some other manner that he knows what he is doing.
********
The following example of value engineering will illustrate how the
various deck variables can be selected in order to provide the
client a suitable product at a fair price:
It is required to provide metal roof deck for a large warehouse.
The engineer has made several efficiency and cost studies and has
determined that a wide rib, 20 ga., 1-1/2" deep deck on a seven foot
3-span condition meets his requirements for load carrying ability
and deflection. He selected the wide-rib deck because, had he used
intermediate rib, it would have required an 18 ga. thickness.
Narrow rib was not considered because the span would have been so
short that it would have required many more supporting members.
Three-inch deep deck was considered and the span could have been
increased to 10'-0 and the deck lightened to 22 ga., however the
supporting members increased in size and did not fit in well with
the bay width of 35'-0. 20 gage deck is amongst the most commonly
used. Most manufacturers carry a stock of 20 and 22 gage coils
resulting in good availability and quick delivery. Painted deck was
selected because the interior of the building is dry, well
ventilated, and not subject to corrosive atmosphere, condensation,
dampness, or any other condition that would have required a more
expensive coating. The Engineer needed some diaphram strength from
his deck system so he selected a deck with nestable side laps rather
than interlocking side laps. Interlocking side laps are normally
fastened with a button punching device and this method is unreliable
in transmitting diaphragm shear forces. Nestable side laps can be
welded, screwed, or pop riveted. In 20 and 22 gage deck there is a
danger of blow-throughs when welding side laps so a self-drilling
screw system was selected. Plain rather than die-set panel ends
were stipulated. There was no reason to require die-set ends. The
probability existed that the deck might have to be laid in a
patchwork manner and die-set ends would have created a severe
hardship for the erectors since die-set deck is ordinarily laid out
end-to-end all in one direction from one end of the building to the
39-9
© 2003 by American Institute of Steel Construction, Inc. All rights reserved.
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other. The deck was supported by members which had relatively thick
flanges. For this reason it was felt that welding would be the most
efficient manner of fastening. (Figure 16) If the supporting
material had been thinner, screw type or power-driven fasteners
would have been considered. As it was, the Engineer did wisely
permit all three methods in his specification. Since the deck was
thicker than 0.028", weld washers were not needed nor specified.
* * * * * * * *
The previous scenario is typical of the deck selection process used
by many designers. Note that unnecessary features were not
specified such as galvanizing, die-set ends, weld washers, accoustic
treatment, cell-deck, insulation clips, ceiling hangers, or
restrictive erection procedure. The end result is a roof deck no
more expensive than it has to be and which will fulfill the design
and performance requirements.
* * * * * * * *
Floor Deck
Similar economical advantages can be realized in the selection of
floor deck.
Floor deck for the support of poured-in-place concrete is available
in several styles - form deck (centering) which usually comes in a
modified corrugated profile varying in nominal depth from 1/2" to
1-1/4", composite (deformed) floor deck, cellular deck, deck for use
with shear studs, deck which cannot be used with shear studs, vented
or unvented deck, and deck with provisions for hanging ceilings.
(Figure 17) Deck is available in 1-1/2, 2, and 3" depths and some
manufacturers have special deeper decks. Inverted roof deck can be
utilized as a form for placing wet concrete. Floor deck is
available in gages from 16 to 28 depending upon the type selected.
It is available in uncoated, galvanized, phosphatized, painted, and
certain combinations, again depending upon the manufacturer and type
of deck. Floor deck comes with either nestable or interlocking side
laps, depending on the type and manufacturer.
As with roof deck there are many variables amongst floor deck
features, enough so that careful selection must be made in order to
assure that the client receives maximum value. The cost conscious
designer will only specify those features which he deems necessary
to proper performance and will reject unnecessary requirements which
serve no particular purpose in his structure. If he does a good job
chances are the deck bids will be as low as possible.
* * * * * * * *
TUBE AND PIPE ECONOMY
Tubes and pipes make economical column members. They are an
excellent choice when stiffness about both axes is required. They
can be used as hollow members or filled with concrete. There is no
39-10
© 2003 by American Institute of Steel Construction, Inc. All rights reserved.
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great strength advantage to filling small tubes or pipe with
concrete. A TS3x3x1/4x10'0 has a capacity of 37k when filled with
concrete and 33k when unfilled. For larger columns there is
an advantage to adding concrete filling. For example, a pipe 8"
standard column 12 feet long has a capacity when filled with 3000
psi concrete of 217k whereas the unfilled capacity is only 155k.
Tubes and pipes have less surface area than equivalent wideflange
members. For example listed here are the surface areas per linear
foot of three common sizes:
W8x31 = 3.89 sq. ft.
TS8x8x1/4 = 2.65 sq. ft.
pipe 8 std = 2.26 sq. ft.
This can be a significant cost factor if the members require an
exotic surface coating or fire proffing.
Tubes offer excellent resistance to torsional forces and can be used
to support eccentric loads such as relieving angles for brick
veneer, stone, or precast concrete. (Figure 18)
Tubes also make efficient bracing members. Figure 19 shows various
methods of connecting tube and pipe members. They can also be
combined with other structural shapes to produce some startling
aesthetic effects. (Figure 20.)
In recent years tube and pipe prices have become more competitve.
Availability is sometimes a questionmark - a fabricator or supplier
should be consulted.
* * * * * * * *
UNECONOMICAL DESIGN PRACTICES
A goodly portion of the fabricator's overhead expense is spent on
estimating. For every job he gets he may make 10 to 20 unsuccessful
attempts. Some recent project specifications have been written in
such as way as to require the fabricator to complete significant
portions of the steel design in order to prepare an accurate cost
estimate. Here are some examples:
1.
"Metal roof deck shall be designed by the metal deck contractor. Dead load is 25 psf. Live load to be in accordance with
local applicable building codes. Maximum live load deflection
is L/240. Drift loading shall be taken into consideration.
The decking contractor shall coordinate all roof opening sizes
and locations and shall design and provide headers as required.
Minimum deck thickness is 20 ga."
2.
"Metal floor deck shall be designed by the metal deck contractor without shoring to carry the weight of the wet concrete plus
a temporary load of 20 psf or a concentrated load of 150# on a
one foot width of deck, whichever results in a heavier deck.
Deflection is limited to L/180 or 3/4" whichever is the
39-11
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smaller. If shoring is required at thickened slabs or tapered
ramps the deck contractor will determine the need for shoring
and design and provide the shoring as required. Minimum floor
deck thickness is 20 ga."
3.
"All floor beam and girder connections shall be at least strong
enough to develop the end reaction of the uniformly loaded
member considered fully composite. The end reaction of all
beams and girders shall be calculated from the current AISC
Manual of Steel Construction "Uniform Load Constant Table"
multiplied by the ratio Str/S to account for the composite
construction. The connection design shall also consider all
concentrated loads acting on the member." (No loads given.)
4.
"Provide welded stiffener plates on both sides of the beam web
at points of concentrated loads." (No loads given.)
5.
"At tower wind bracing connect for the full compression
capacity of the member or 50% of the tension capacity, whichever is greater." (No load given.)
6.
"All beams and girders framing to columns shall have connections designed for a horizontal bracing force on both ends equal
to 1% of the maximum allowable load on the column. The maximum
load on the column = 0.6 Fy A where A equals the gross area of
the column." (No loads given.)
7.
"Provide web doubler plates as required at all beams and
columns where shear loads are beyond the capacity of the
member."
8.
"Provide column stiffeners as required at all column moment
connections where the beam flange forces are beyond the
capacity of the column member."
9.
"Verify the stud shear capacity with the type and brand of
floor deck supplied. The number of studs shown on the design
is based on N=9 and a stud capacity of 11.5k. Adjust the
quantity of studs shown on the design if the stud capacity
differs from that given above."
10.
"Design column base plates for the full capacity of the column
using the procedure given in the current AISC Manual of Steel
Construction. Design beam bearing plates for the full capacity
of the beam at the given span." (No loads given in either
case.)
* * * * * * * *
These are but 10 examples in which a considerable amount of
additional design work must be done by the fabricator before he can
produce an accurate estimate of his costs. If 8 fabricators are
pursuing a particular project the additional design work would be
repeated 8 times. This duplication of effort is a shameful waste of
America's time and energy. It will boost estimating costs and this
39-12
© 2003 by American Institute of Steel Construction, Inc. All rights reserved.
This publication or any part thereof must not be reproduced in any form without permission of the publisher.
will eventually be passed on to the client. The time consumed will
undermine one of steel's strong points - speed of delivery. The
fabricator who elects to bypass the necessary design investigations
may end up in deep trouble with a bid and a job that is much too
low. If he loads his bid to cover "worst case" conditions the
chances are he will not get the job. If all bidders elect to
pad the bids the client ends up paying more than he should. When a
fabricator has to determine loads via analysis of the member the
results will often be unrealistic. If the member was designed based
on stiffness, aethetics, minimum thickness requirements, or
deflection, this information is not normally known by the analyser.
The resulting connection may be designed for a load that is many
times greater than the actual load. This is uneconomical for the
client. Worse yet it may result, over the long haul, in a shift by
some designers from steel to some other material because their steel
designs are consistently expensive. We certainly don't want this to
happen. Fortunately for the steel industry. These practices are
not universal.
The separating of design duties will further complicate the question
of design responsibility. Those who continue to fan the flames for
split responsibility will have a field day with this situation. The
unfortunate result is that the cost of steel construction will be
driven upwards at a time when the steel fabricating industry is
locked in a serious effort to stay competitive. To hold the line it
is essential that fabricators and designers cooperate to the fullest
extent possible.
* * * * * * *
THE END
* * * * * * *
David T. Ricker
June, 1988
39-13
© 2003 by American Institute of Steel Construction, Inc. All rights reserved.
This publication or any part thereof must not be reproduced in any form without permission of the publisher.
MILL EXTRAS
Percent increase
above base price*
Light
Medium
sections.......WF..................................
sections......WF..................................
Heavy
sections.......WF..................................
Standard beams................Higher Base Price..........
Standard
channels........................................
Miscellaneous channels...................................
Standard
Cut lengths
angles..........................................
<10'........................................
10%
17%
24%
13%
9%
17%
14%
Inquire
9%
5%
1%
0
40' to 50'.................................
1%
50' .......................................
0
50' to 60'.................................
1%
60' .......................................
0
>60'
.......................................
6%
Quantity >10k. ..........................................
0
< 1k .......................................... 23%
A572-50 ................................................. 13%
A588 .................................................... 35%
Chemistry (Special ingredients or amounts)............... varies
End milling ............................................. 16%
Splitting tees .......................................... 12%
Cambering ............................................... 12%
10' to 20'.................................
20' to 30'.................................
30' to 40'.................................
40' .......................................
*
These percentages are general in nature, vary between suppliers
and are subject to other variations.
FIGURE
1
FIGURE 2
© 2003 by American Institute39-14
of Steel Construction, Inc. All rights reserved.
This publication or any part thereof must not be reproduced in any form without permission of the publisher.
FIGURE
3
FIGURE 4
39-15
© 2003 by American Institute of Steel Construction, Inc. All rights reserved.
This publication or any part thereof must not be reproduced in any form without permission of the publisher.
FIGURE
FIGURE
39-16
5
6
© 2003 by American Institute of Steel Construction, Inc. All rights reserved.
This publication or any part thereof must not be reproduced in any form without permission of the publisher.
FIGURE
7
FIGURE
8
39-17
© 2003 by American Institute of Steel Construction, Inc. All rights reserved.
This publication or any part thereof must not be reproduced in any form without permission of the publisher.
FIGURE
9
FIGURE 10
39-18
© 2003 by American Institute of Steel Construction, Inc. All rights reserved.
This publication or any part thereof must not be reproduced in any form without permission of the publisher.
FIGURE 11
FIGURE
12
39-19
© 2003 by American Institute
of Steel Construction, Inc. All rights reserved.
This publication or any part thereof must not be reproduced in any form without permission of the publisher.
FIGURE
FIGURE
39-20
13
14
© 2003 by American Institute of Steel Construction, Inc. All rights reserved.
This publication or any part thereof must not be reproduced in any form without permission of the publisher.
FIGURE 15
FIGURE
16
39-21
© 2003 by American Institute of Steel Construction, Inc. All rights reserved.
This publication or any part thereof must not be reproduced in any form without permission of the publisher.
FIGURE
17
F I G U R E 18
39-22
© 2003 by American Institute of Steel Construction, Inc. All rights reserved.
This publication or any part thereof must not be reproduced in any form without permission of the publisher.
FIGURE
FIGURE
39-23
19
20
© 2003 by American Institute of Steel Construction, Inc. All rights reserved.
This publication or any part thereof must not be reproduced in any form without permission of the publisher.
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