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AISC 2005 SEISMIC PROVISIONS: DESIGN DRAWING REQUIREMENTS
2008 NASCC –Nashville, TN
Authors:
Larry A. Kloiber, PE Lawrence A. Kloiber PE has been involved in
designing, fabricating and erecting structural steel for almost 40
years, first as an AISC Engineer and then with LeJeune Steel Co.
Larry is a graduate of Marquette University with a BCE and the
author of numerous papers on steel design and fabrication. He is a
member of the AISC Specification Committee and the AWS D1.1 Code
Committee. AISC in Sept 2002 presented Larry with a Lifetime
Achievement Award in “Special recognition for many years of service
to the structural design, construction, and academic communities”.
In 2004 he received the TR Higgins Lectureship Award for the best
paper on structural steel design from the AISC for his paper “The
Design of Orthogonal and Skewed Connections.”
Larry S. Muir, PE
Larry S. Muir, PE has been employed by Cives Steel Company for
over 12 years, currently as chief engineer of Cives Steel Company
and president of Cives Engineering Corporation. He is a member of
the AISC Specification Committee and the AWS D1.1 Subcommittee on
Design. Mr. Muir holds Bachelor’s degrees from both the Southern
College of Technology and the University of Tennessee, Knoxville.
He also holds a Master’s degree from the University of Tennessee.
Mr. Muir has been responsible for connection design for a number of
projects with seismic requirements. He has authored or co-authored
numerous technical papers and is currently working on an AISC
Design Guide for Vertical Bracing Connections with Dr. William A.
Thornton.
ABSTRACT The 2005 Seismic Provisions for Structural Steel
Buildings require the structural design drawings to “show the work
to be preformed” and presents a list of items required for the
seismic load resisting system. The use of the list requires a
knowledge of the connection requirements in the Provisions for the
various seismic load resisting systems along with the requirements
in Appendix Q – Quality Assurance and Appendix W – Welding
Provisions. Other requirements for the seismic load resisting
system connections are found in ANSI /AWS D1.8 and ANSI / AISC FEMA
358-05. This paper will review these design drawing requirements
and point out where they can found in these documents.
AISC 2005 SEISMIC PROVISIONS: DESIGN DRAWING REQUIREMENTS
The experiences of the 1994 Northridge and the 1995 Kobe
earthquake have expanded our knowledge regarding the seismic
response of steel building structures. This has resulted in new,
complex and unique design and fabrication requirements per the 2005
AISC Seismic Design Provisions (Provisions). The adoption of
SEI/ASCE 7 (ASCE 2005) by the governing codes has expanded the
range of buildings that now must be designed using these
Provisions. The increased number of structures that must be
designed and built with a seismic response modification factor
(R-factor) greater than 3 coupled with trend for structural design
firms to practice nationally
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rather than regionally means that there may be firms designing
these buildings that are not be familiar with some of the special
requirements of the Provisions. This paper will attempt to point
out the design information that is required to ensure that
fabricators and erectors can accurately bid, fabricate and erect
these structures.
There is a fundamental difference in design concept between a
typical non-seismic building design (including ones with an R ≤ 3)
and a design for R>3 using the Provisions. A non-seismic
building under full design loads may experience some local
inelastic response but typically members and connections will not
experience significant yielding. If however a building designed for
R>3 experiences a full design seismic event it is likely that
most of the seismic load resisting system (SLRS) will experience
substantial yielding possibly over several cycles. Therefore it is
important that all of the requirements for materials, bracing and
connection details be as specified to enable this systems to
perform as designed. To ensure this happens the Provisions require
the structural design drawings and specifications show the work to
be preformed. Unlike non-seismic building structures where it is
possible to provide member sizes and loads along with general
connection requirements and have the detailer complete the design
as outlined in the Code of Standard Practice Section 3.1.2 the
Provisions require the design drawings show the connection
configuration along with connection material and sizes.
The Provisions provide an outline of some of the key information
required on the design documents as well as detailed requirements
for the various types of SLRS. The Commentary to the Provisions
provides excellent background information and a rationale for the
requirements along with some guidance on connection details.
Appendix W of the Provision covers welding requirements, however it
was intended that this would be superseded by AWS D1.8-2005,
Structural Welding Code – Seismic Supplement which has subsequently
been published. In addition the AISC Seismic Design Manual has
general design information along with information on various
pre-qualified SLRS along with sketches of connection details and a
discussion of items such as demand critical welds and protected
zones. Finally there is ANSI/AISC 358-05 Prequalified Connections
for Special and Intermediate Moment Frames for Seismic
Applications. This is available in electronic format either as a
download from AISC or as a CD-ROM. This publication contains
essential information for designing and detailing SLRS moment
frames and the required connection details. STRUCTURAL DESIGN
DRAWING AND SPECIFICATION REQUIREMENTS The Provisions Section 5.1
as mentioned above provides an outline of the key information that
must be shown on the structural design drawings and requirements.
These are as follows:
1. Designation of the seismic load resisting system (SLRS) 2.
Designation of the members and connections that are part of the
SLRS 3. Configuration of the connections 4. Connection material
specifications and sizes 5. Locations of demand critical welds 6.
Lowest anticipated service temperature (LAST) of the steel
structure, if the structure is not enclosed and
maintained at a temperature of 50 °F (10 °C) or higher 7.
Locations and dimensions of protected zones 8. Locations where
gusset plates are to be detailed to accommodate inelastic rotation
9. Welding requirements as specified in Appendix W, Section
W2.1.
The User Note to this list goes on to state the following:
User Note: These Provisions should be consistent with the Code
of Standard Practice, as designated in Section A4 of the
Specification. There may be specific connections and applications
for which details are not specifically addressed by the Provisions.
If such a condition exists, the contract documents should include
appropriate requirements for those applications. These may include
nondestructive testing requirements beyond those in Appendix Q,
bolt hole fabrication requirements beyond those permitted by the
Specification, bolting requirements other than those in the
Research Council on Structural Connections (RCSC) Specification for
Structural Joints Using ASTM A325 or A490 Bolts, or welding
requirements other than those in Appendix W. The other items would
include bracing requirements SLRS moment frames and gravity column
splice details. Designation of the Seismic Load Resistant System
(SLRS)
It is imperative that the engineer define both for himself and
for the fabricator the extents of the SLRS. It must be noted that
this task may not be as easy as it first appears. The seismic load
resisting system does not consist only of
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the members within the bounds of the systems designated in
Chapters 9 through 17 of the Provisions (SMF, IMF, OMF, SCBF,
etc.), but instead also extends to members that deliver the seismic
loads to the frames. This becomes especially confusing since the
IBC Table 1617.6.2 is titled, “Design Coefficients and Factors for
Basic Seismic-Force-Resisting Systems”, which at least would imply
that the Seismic Force Resisting System is limited to those members
contained within the Framing Systems listed in the table. The
Provisions however define the seismic load resisting system as the
“assembly of structural elements in the building that resists
seismic loads, including struts, collectors, chords, diaphragms and
trusses.” Modern analysis methods can further complicate the task
of defining the SLRS for a particular structure. If an entire
structure is modeled three-dimensionally in the computer and then
subjected to a static, dynamic or pseudo-dynamic seismic loading
than potentially every member in the structure will resist some of
the seismic load. Does this mean that every member in the structure
is part of the SLRS and must meet the requirements of the
Provisions? Such a broad interpretation is rare, but not unheard
of. In order to facilitate the discussion a new term Primary
Seismic Load Resisting System (P-SLRS) will be introduced. The
P-SLRS will consist of only those members for which the
requirements of Sections 9-17 apply, whereas the SLRS consists of
these members plus any other members carrying seismic loads.
Designating the P-SLRS in the structural notes where the other
seismic design information is given is necessary but often not
sufficient. It would instead usually be shown in Item 2 where the
individual elements are designated on the plans and elevations. It
may be helpful to provide a short verbal description of the total
system in the structural notes as a guide for the design team. It
is important not to define the SLRS too generally since potentially
unnecessary cost increases will be incurred. The Provisions require
that “the design of connections for a member that is a part of the
SLRS shall be configured such that a ductile limit state in either
the connection or the member controls the design.” It should also
be noted that this requirement does not limit the type of member or
loading condition to which the ductile limit state must apply. A
strict interpretation would be that all members or connections
designated to be within the SLRS must be governed by a ductile
limit state for all loading conditions. This would mean that the
shear connection for a gravity beam that happens to be in a line
designated as the SLRS must be governed by a ductile limit state.
The strictest interpretation would also mean that all connections
to a collector element must be governed by a ductile limit state
whether that element transfers lateral load or not. It can often be
difficult to configure connections such that a ductile limit state
is achieved (Muir 2007). If fully detailed connections are to be
provided to the fabricator, as the Provisions indicate, this is
less of an issue. However, if connection design is to be completed
by the fabricator or designated to a third party, not only must the
SLRS be clearly defined, but an interpretation of the Provisions
must also be agreed to. Designation of the members that are part of
the SLRS This allows the entire construction team to locate the
critical design elements of the building and helps provide a check
to make sure nothing is overlooked or missing. The importance of
this can not be overstressed. We have seen buildings where this was
not done and key elements of the diaphragm and collector systems
and in one case some moment frames were not properly detailed in a
timely manner resulting construction delays and charges. We think
the SLRS should be shown both in plan and elevation. In plan it is
possible to either do a key type plan showing the elements or it
can be shown my shading all of the elements on the structural
plans. Either way the entire SLRS including drag struts and any
diaphragm members should be shown. It is important to also show the
SLRS in elevation as is typically done for vertical bracing. It is
our recommendation that all member sizes be shown on the elevation
rather than showing beams sizes only on the plans as is often done
with bracing elevations. This will help when you add the items
required in Items 3,4, 5, 7, & 8. Where the SLRS involves other
materials such as shear walls these elements should be indicated
where the steel connects to them. Configuration of the
connections
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The responsibility for completing connection design can vary
from project to project and even more so depending on the
geographic location of the structure. Engineers in the Eastern part
of the U.S. are often accustomed to relegating connection design to
the fabricator. Nearer the West coast connection design is often
completed by the Engineer. The Provisions state that the connection
configuration must be shown on the structural design drawings. This
could be a pretty ambiguous statement, but when read alongside Item
4 below and the Commentary to the Provisions, it becomes difficult
to satisfy the Provisions without providing fully detailed
connections for the SLRS on the structural design drawings. With
this in mind the connections for the prequalified SLRS moment
frames and braces have a number of very specific detail
requirements for items such as welds, bolts, stiffeners, gusset
plates, continuity plates and doubler plates, with which some
engineers may not be familiar. For example there are dimensions
given for detail corner clips on continuity plates to prevent
welding in the “k” zone of the column web as shown in commentary
Figure C-I-7.2 below.
When configuring a connection it is important that a force be
resisted by a single type of connection in other words either
entirely by bolts or by welds to ensure its performance under full
load. The commentary to Provisions gives examples of this as shown
below.
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Beam to column moment connections have required dimensions and
surface finish requirements for weld access holes as shown in the
recommend access hole below.
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All of this information along with the location and work points
should be shown. We will give more examples when we review the
specific details for the various types of SLRS. Connection material
specifications and sizes The Provisions in Section 6.1 and
ANSI/AISC 358-05 in the material sections of the various
prequalified SLRS discuss the material requirements. The Provisions
references Section A3.1a of the 2005 AISC Specification for
Structural Steel Buildings (Specification) for material that can be
used in SLRS. Wide flange shapes should preferably be ASTM A992
since this specification was developed specifically for SLRS
members. A992 has specified maximum yield to tensile ratio to
ensure ductility along with a limit on the carbon equivalent to
ensure weldablity.
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Material requirements for the connection elements must be
consistent with the prequalified details in ANSI/AISC 358-05. This
includes the material specification along with the size and
thickness of each element along with bolts and welds. Bolt material
grade, size, location, and tensioning must be shown. The Provisions
Section 7.2 Bolted Joints, addresses bolting requirements. While
bolts typically are designed as bearing type connections with
standard holes, all bolts are required to be pretensioned and have
Class A faying surfaces. In other words the connections are
designed as bearing but detailed as if they were slip critical.
This means painted members may have to be masked at the connections
and galvanized structures will require hand-wire brushing in order
to roughen the faying surfaces. There are exceptions for bolted
bracing where oversize holes are permitted in one ply provided the
connection is designed as slip critical and for end plate moment
connections, which do not require a Class A faying surface. Section
7.3 Welded Joints, references Appendix W for welding requirements
along with requirements of AWS D1.1 for weld procedure
specifications. We will go into this in more detail when we review
the new AWS D1.8 material. Basically the Provisions require that
all welds in the SLRS be made with a filler metal that can produce
welds with a minimum Charpy-V-notch toughness of 20 ft-lbs at 0 ºF
either by test or manufacturer’s certification. There are
additional requirements for demand critical welds as noted below.
Locations of demand critical welds Welds are designated demand
critical in the Provisions based on consideration of the inelastic
strain demand and the consequence of failure. The location of these
demand critical welds is given in Provisions and in ANSI/AISC
358-05 in the section applicable to designated SLRS. These welds
shall be made with a filler metal that can produce welds with a
minimum Charpy-V-notch toughness of 20 ft-lbs at -20ºF as
determined by test of manufacturer’s certification and at 40 ft-lbs
at 70ºF as determined by Appendix X or other approved method. The
User Note in Section 7.3b lists some typical demand critical welds
in SLRS. They are as follows:
a. Welds of beam flanges to columns b. Welds of single plate
shear connections to columns c. Welds of beam webs to columns d.
Column splice welds including welds to base plates
There are a number of other quality control / quality assurance
items associated with demand critical welds that are covered in
Appendices W and X along with AWS D1.8. Items such as use of
backing bars and run off tabs including requirement for trimming
and finishing of run off tabs are specifically addressed. Lowest
anticipated service temperature (LAST) of the steel structure, if
the structure is not enclosed and maintained at a temperature of 50
°F (10 °C) or higher. The majority of building applications are in
temperature controlled situations where this will not be a concern.
When structures are subjected to temperatures less than 50 °F such
as a freezer storage building or an unheated building in a cold
climate additional requirements for filler metals are necessary for
demand critical welds. Locations and dimensions of protected zones
The protected zone is the area immediately around the plastic
hinging region. The FEMA/SAC testing has demonstrated the
sensitivity of these areas to discontinuities caused by welding,
penetrations, changes in section or construction caused notches.
The Provisions Section 7.4 has the following requirements for the
protected zone:
(1) Within the protected zone, discontinuities created by
fabrication or erection operations, such as tack welds, erection
aids, air-arc gouging and thermal cutting shall be repaired as
required by the engineer of record.
(2) Welded shear studs and decking attachments that penetrate
the beam flange shall not be placed on beam flanges within the
protected zone. Decking arc spot welds as required to secure
decking shall be permitted.
(3) Welded, bolted, screwed or shot-in attachments for perimeter
edge angles, exterior facades, partitions, duct work, piping or
other construction shall not be placed within the protected
zone.
Exception: Welded shear studs and other connections shall be
permitted when designated in the Prequalified Connections for
Special and Intermediate Moment Frames for Seismic Applications
(ANSI/AISC 358), or as
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otherwise determined in accordance with a connection
prequalification in accordance with Appendix P, or as determined in
a program of qualification testing in accordance with Appendix S.
The locations and dimensions of these protected zones for moment
connections are found in the Provisions and in ANSI / AISC 358 in
the applicable type of SLRS. The protected zone for SCBF consists
of the middle quarter of the brace and an area near the end
connections where buckling is likely to occur. For EBF the link
represents the protected zone. The fabrication and erection work
and the subsequent work by other trades have the potential to cause
discontinuities in the SLRS. When located in the protected zone
these discontinuities are required to be repaired by the
responsible contractor to the satisfaction of the structural
engineer. This highlights the need to clearly show the protected
zone on the design drawings and to clearly specify the requirements
for construction in this area. Locations where gusset plates are to
be detailed to accommodate inelastic rotation When an R greater
than 3 is assumed, significant inelastic response is expected
during a seismic event. Therefore, unlike a structure designed to
behave elastically, the braces in a SCBF, OCBF, or EBF are expected
to buckle. It has been observed that the large deformations that
occur during out-of-plane buckling of the brace can tend to tear
the gusset free from the beam and/or the column. For this reason,
the Provisions Section 13.3b require bracing connections to have
required flexural strength equal to 1.1 Ry Mp (LRFD). This required
strength need not be met in conjunction with the forces calculated
to support the brace loads. Instead it should be investigated as an
independent load case. Bracing typically however is designed using
the exception to 13.3b that allows bracing that can meet the
required tensile strength and can accommodate the required
inelastic rotations associated with post-buckling rotations need
not meet this provision. Tests have shown this can be accomplished
where a single gusset plate is used and the brace end is separated
by at least two times the thickness of the plate from a line
perpendicular to the brace axis about which the plate can bend
unrestrained. This typically is a line between the ends of the
gusset plate weld to the beam and to the column or column
connection. See the figure from the commentary below.
Commentary to Seismic Provisions – Fig C-I-13.2 Brace-to-gusset
plate requirement
for buckling out-of-plane bracing system Welding requirements as
specified in Appendix W, Section W2.1. The general welding
requirements are given in AWS D1.1 and additional requirements for
the SLRS are invoked in Appendix W and now in AWS D1.8. We have
already talked about the basic filler metal requirements and will
discuss this in more detail when reviewing Appendix W requirements.
AWS D1.1 has always required a written weld procedure specification
(WPS) for every structural weld. Prior to Northridge this was often
overlooked. Now it is clearly required and the structural engineer
or his welding consultant is required to review and approve the
WPS. The contract documents should clearly show this.
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Additional structural drawing detail requirements in the
Provisions
1. SLRS column splice requirements are given in Section 8.4a.
The splices need to be located away from beam to column
connections. The recommendation is typical to be 4 to 5ft above the
beam but in general the splice should be in the middle third of the
column. Because of the splice strength requirements in Section 8.3
it is important that the splice be fully detailed on the design
drawings. Where bolted splices are used there must be plates or
channels on both sides of the web.
2. Columns that are not part of the SLRS also have additional
requirements as spelled out in Section 8.4b. The minimum forces
required to be developed in these splice will require a special
column splice and this detail should also be shown on the design
drawings.
3. SLRS column bases must meet the requirements of Section
8.5a,b,&c and anchor rod embedment should be per ACI 318
Appendix D. Anchor rod sizes and locations, along with washer
requirements, hole sizes and base plate welds must meet these
design requirements and must be shown. Where special embedment is
used for base fixity the design requirements must be shown. The
commentary to this section gives a good discussion along with
examples of how to develop these forces. While the Provisions do
not cover column bases for columns that are not part of SLRS some
consideration should be given to developing a limited amount of
base shear either by embedment or by bearing on the anchor
rods.
4. Width / thickness ratios of SLRS members must be less than
those that are resistant to local buckling in order achieve the
required inelastic deformations required. While the width /
thickness ratios given in the Specification Table B4.1 for compact
sections are adequate to prevent buckling before the onset of
strain hardening, tests have shown that they are not adequate for
the required inelastic performance in several SLRS. Provisions
Table I-8-1 gives the limiting ratios for seismically compact
member. This often governs the selection of round or rectangular
diagonal members in seismic braced frames and may control the
sizing of strut members also.
5. Lateral bracing requirements for Special Moment Frame (SMF)
columns at beam connections are covered in Section 9.7. If the
bracing requirement can not be met by the floor slab and the
elements of the moment connection than the required bracing member
and connection should be shown.
6. SMF beams require bracing at both the top and bottom flanges
per Section 9.8. While the floor slab typically will brace the top
flange additional braces should be shown where required with the
necessary connections.
Appendix W –Welding Provisions and ANSI / AWS Dl.8 Structural
Welding Code – Seismic Supplement These two documents list the
minimum information that must be shown on the design documents.
Appendix W requires the following information as a minimum:
(1) Locations where backup bars are required to be removed (2)
Locations where supplemental fillet welds are required when backing
is permitted to remain (3) Locations where fillet welds are used to
reinforce groove welds or to improve connection geometry (4)
Locations where weld tabs are required to be removed (5) Splice
locations where tapered transitions are required (6) The shape of
weld access holes, if a special shape is required (7) Joints or
groups of joints in which a specific assembly order, welding
sequence, welding technique or other
special precautions are required The D1.8 list includes the
items above along with some of the requirements in the Provisions.
D1.8 includes a requirement to show any joints that require a
specific assembly order, special welding techniques (See ANSI /
AISC 358-2005 for Prequalified End Plate Moment Connections) or
other special precautions. There is also a requirement to show a
Quality Assurance Plan for the project. The steel backing and weld
tabs used with complete joint penetration (CJP) welds in fully
restrained moment connections must be removed, except the top
flange backing attached to the column by a continuous fillet weld
at the edge below the CJP weld need not be removed. Tests have
shown that by fillet welding this unfused edge of the backing the
stress riser is significantly reduced. It is important that the
underside of the backing be welded only to the column and not to
the underside of the beam flange. The moment connection detail
should show this.
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Where removal of the steel backing is required, the root should
be back gouged to sound weld metal and a reinforcing fillet with a
minimum leg of 5/16 in. While this is a minimum size weld care
should be taken to make sure this reinforcement completely covers
the area that was gouged. The toe of the fillet weld leg against
the beam should be located on the base metal. Weld tab removal
shall extend to within ⅛ in. of the base metal except at continuity
plates when it can be ¼ in. Gouges and notches are not permitted
and while grinding to a flush condition is not required the contour
should provide a smooth transition. AWS D1.8 provides recommended
details for these areas. There are a few cases where weld tab
removal may impractical or unnecessary so the drawings should make
it clear where weld tab removal is required. Appendix A and D 1.8
contain a number of other special requirements that should either
be specifically referenced in contract documents. In addition to
the filler metal requirements mentioned above, demand critical
welds have the following requirements:
• Manufacturers certificates of conformance for filler metals •
Special restrictions on care and exposure of electrodes •
Supplemental welder qualification for restricted access welding for
bottom flange welding through access
holes • Special weld sequence for bottom flange welding through
access holes • Supplementary requirements for qualification of
ultrasonic testing (UT) technicians.
Appendix Q – Quality Assurance Plan The Quality Assurance Plan
(QAP) should be prepared by the engineer of record and made a part
of the contract documents. Appendix Q provides the minimum
requirements for this plan listing requirements for the Contractor
Documents, Quality Assurance Agency Documents, Inspection Points
and Frequencies along with special requirements for weld and bolt
inspections. Again each of the requirements should be listed or the
appropriate sections referenced in the contract documents to make
sure both the contractor and the agency responsible for quality
assurance are aware of what is required. For example it is
important that the fabricator and erector submit for approval a WPS
for all welds and that the WPS for a demand critical weld for a
bottom flange weld made through a weld access hole list the
required materials, the proper technique and the required welder
certification. Appendix Q has specific requirements for NDT of
welds that must be shown on the contract documents. These include
UT testing requirements for CJP welds and base metal over 1½ in.
thick connected with CJP welds loaded in tension in the through
thickness direction. There are also requirements for magnetic
particle (MT) inspection of certain thermally cut surfaces such as
weld access holes when the flange exceeds 1½ in. thick and areas
where weld tabs have been removed except for continuity plates.
Quality assurance requirements for bolting include verifying that
faying surfaces meet the specification requirements and that the
bolts are properly tensioned per the Research Council on Structural
Connections (RCSC) specification. ANSI / AISC 358-05 - Prequalified
Connections for Special and Intermediate Moment Frames for Seismic
Applications SMF and IMF details that are prequalified to the
requirements of the Provisions should be used. This will avoid the
time and cost required for the testing required by Appendix S to
qualify new designs. ANSI / AISC 358-05 provides general design
requirements for prequalified systems along with special details
and limits for Reduced Beam Section (RBS) and Bolted End-Plate
connection designs. A good summary of this information was
presented in the January 2007 issue of Modern Steel Construction.
When using any prequalified system it is important to first verify
that the members specified meet the section limits specified. This
includes both minimum b/t and maximum depth and weight limits if
any. Adding moment frames or changing member sizes late in the
project to meet these requirements may cause serious cost and delay
problems.
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RBS connections have specific geometry and finish requirements
for the thermally cut reduced section. The required geometry should
be shown on the contract documents along with the protected area
and the finish requirements either directly specified or referenced
to ANSI / AISC 358-05, Section 5.7 Fabrication of Flange Cuts.
End-plate connections both unstiffened and stiffened have been
prequalified for SLRS, though neither are prequalified for SMFs
when concrete structural slabs are in direct contact with the
steel. The qualified connections requirements are given in great
detail in Section 6. For example Table 6.1 Parametric Limits on
Prequalification gives limits for each of the key end plate
parameters. The end-plate connections should be fully detailed on
design drawings and each of the dimensions checked to make sure it
complies with Table 6.1. The prequalified end-plate connections
have very specific weld details required for the beam flange and
web connection to the end plate. The flange weld requirement is
given as follows:
“The beam flange to end-plate joint shall be made using a CJP
groove weld without backing. The CJP groove weld shall be made such
that the root of the weld is on the beam web side of the flange.
The inside face of the flange shall have a 5/16-in. (8-mm) fillet
weld. These welds shall be demand critical. Backgouging of the root
is not required in the flange directly above and below the beam web
for a length equal to 1.5k1. A full-depth PJP groove weld shall be
permitted at this location.”
When detailing this connection on the design drawings a PJP weld
depth equal to the beam flange thickness should be shown over the
web for the length specified above. On the flange either side of
this PJP weld, a standard CJP weld detail with a reinforcing fillet
should be shown. The web weld requirements are as follows:
“The beam web to end-plate joint shall be made using either
fillet welds or complete joint penetration (CJP) groove welds. When
used, the fillet welds shall be sized to develop the full strength
of the beam web in tension from the inside face of the flange to 6
in. (150 mm) beyond the bolt row farthest from the beam
flange.”
Where possible it is recommended that the fillet welds be shown
for the web welds. Other Contract Document Requirements The
Provisions in addition to all of the design the drawing
requirements covered above has in Section 5, Appendix Q and
Appendix W various requirements for shop drawings, erection
drawings and submittals that the fabricator and erector should
provide. The structural engineer should be familiar with these
requirements and either specifically or by section reference
require these submittals and be prepared to review and approve as
required. Summary A review of the Provisions, AWS D1.8 and ANSI /
AISC 358-05 shows that when a decision is made to use a R-factor
greater than 3 sizing of members is just the first of many steps to
meet the design drawing requirements. Often the material weight
reduction gained by using a large R-factor is more than offset by
the time and cost of providing all of the required details and
quality assurance. Each of these documents have an extensive
commentary with important background information and helpful
sketches of key details. In addition there are other sources such
as Lincoln Electric Company’s “FEMA 353 Welding Manual” which
explains filler metal requirements and shows samples of various
documents that should be submitted. References
1. AISC (2005), Specification for Structural Steel Buildings,
ANSI/AISC 360-05, March 9, American Institute of Steel
Construction, Inc., Chicago, IL.
2. AISC (2005a), AISC/ANSI 341-05, Seismic Provisions for
Structural Steel Buildings, American Institute of Steel
Construction, Inc., Chicago, IL.
-
3. AISC (2005b), Prequalified Connections for Special and
Intermediate Steel Moment Frames for Seismic Applications,
4. ANSI/AISC 358-05, American Institute of Steel Construction,
Inc., Chicago, IL. 5. ASCE (2005), Minimum Design Loads for
Buildings and Other Structures, SEI/ASCE 7-05, American
Society of Civil Engineers, Reston, VA. 6. AWS (2004),
Structural Welding Code Steel, ANSI/AWS D1.1:2004, American Welding
Society, Miami,
FL. 7. AWS (2005), Structural Welding Code – Seismic Supplement,
ANSI/AWS D1.8:2005, American Welding
Society, Miami, FL. 8. Kochalski, Gregory and Jason Ericksen
(2007), “Prequalified Seismic Moment Connections” Modern Steel
Construction. January 2007. American Institute of Steel
Construction, Inc., Chicago, IL. 9. Muir, Larry S. (2007),
“Designing for Ductile Performance of Bolted Seismic Connections”
Engineering
Journal. 1st Q 2007, American Institute of Steel Construction,
Inc., Chicago, IL.
Welcome ScreenCopyrightForeword2008 NASCC CommitteeTable of
Contents3D Software and Complex Hip and Valley Roof SystemsAESS and
the New Canadian matrix: A Category ApproachAISC 2005 Seismic
Provisions: Design Drawing RequirementsConstructability and
TeamworkCool Stuff From EuropeDesign of Lateral Load Resisting
Frames Using Steel Joists and Joist GirdersDesigning with
DampingDetailing and Fabricating High SeismicFive Useful Stability
ConceptsGreen Design: Going Beyond Material IssuesHow Much is Your
Business Really Worth and What Factors Affect the Value of Your
Business?Impact of Diaphragm Behavior on the Seismic Design of
Low-Rise Steel BuildingsImportant Lessons They Didn't Teach Me at
College (or at Least I Don't Think They Did)Large-Scale Tests of
Steel Plate Shear Walls with PEC ColumnsNondestructive Examination
and Special Inspection of Seismic WeldingProcedures and Processes
to Manage CNC DataQuality Assurance for Structural Engineering
FirmsRecent Developments From Research on Steel Plate Shear
WallsThe SJI Composite Steel Joist Catalog First Edition 2007 for
Use by the Design ProfessionalThe Upside of InsuranceT.R. Higgins:
Buckling-Restrained Braced FramesUsing Cold-Formed Steel Members:
Where Do I Begin?
Author IndexHelpPrintSearchExit
