Lessons Learned in Structural Software: Implementing a ... · cannot achieve SCWB, lateral bracing, provisions of AISC 341 Short spans with Deep Beams, connections each have a span/depth

Moment Frames: Design and Detailingper AISC 341 and 358

By Matthew J. Mester, PE, SE

SidePlate Systems, Inc.

SE University, June, 2017 www.LearnWithSEU.com

Topics

Moment Frame Design PrinciplesR=3 Moment Frame SystemsR=3.5 Ordinary Moment Frame SystemsR=4.5 Intermediate Moment Frame SystemsR=8 Special Moment Frame SystemsConnection Design PrinciplesConnection Types in AISC 358

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Learning Objectives

Identify how drift can be controlled in moment framesDifferentiate between R=3, OMF, IMF, and SMF lateral systemsIdentify when to use AISC 358 prequalified connections in moment frames

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Topics


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What code is required in your jurisdiction?

Lateral Analysis/Choosing your Code

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What code is required in your jurisdiction?


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What code is required in your jurisdiction?ASCE 7-05, IBC 2006 or IBC 2009, AISC 360-05, AISC 341-05, AISC 358-05

ASCE 7-10, IBC 2012 or IBC 2015, AISC 360-10, AISC 341-10, AISC 358-10 including Supplements 1&2

Future codes: ASCE 7-16, IBC 2018, AISC 360-16, AISC 341-16, AISC 358-16 including Supplements


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What is important in Moment Frame Design?

Drift?, Strength?, Ductility?

Lateral Analysis

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Columns

BeamsVerticalForce

LateralForce

Beam/ColumnConnection

Typically, DRIFT will govern the design of moment frames, not STRENGTH, but must check bothWhat governs drift in Moment Frames?

Rotation of beamsRotation of columns

Base conditionsDeformation of panel zones

To limit drift, you can increase beams, columns, or panel zone thickness…BUT you will have the most success with increasing BEAM size

Lateral Analysis

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Drift Limits for Wind ProvisionsWhat is required? Is it the Law?

IBC 1604.3 Serviceability: “Structural Systems shall have adequate stiffness to limit deflections and lateral drift.”ASCE 7-10 §1.3.2 Serviceability: “Structural systems, and members thereof, shall be designed to have adequate stiffness to limit deflections, lateral drift, vibration, or any other deformations that adversely affect the intended use and performance of buildings and other structures.”

Lateral Analysis for Wind Loads

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What is required? Is it the Law?ASCE 7-10 §C1.3.2 Commentary Appendix C –Serviceability Considerations (non-mandatory): “Serviceability limit states involve the perceptions and expectations of the owner or user and are a contractual matter between the owner or user and the designer or builder. It is for these reasons, and because the benefits are often difficult to define or quantify, that serviceability limit states for the most part are not included within the model United States Building Codes.”


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How do you select drift limits?AISC Design Guide 3 – Serviceability Design Considerations for Steel Buildings by West & Fisher

H/400, H/500, H/600 for frames with spandrel supported cladding depending on type of exterior system using a 10-year wind MRI


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How do you select drift limits?“Serviceability Limit States Under Wind Loads” by Lawrence G. Griffis, EJ AISC, v30, 1993 Q1

H/400 for steel frames (H=story height and total height)H/400 corresponds to 1/4” in 8’ (the damage threshold limit for gypsum wallboard), or 3/8” in 12’ which corresponds to standard soft joint thickness in brick veneer construction.


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Wind Speed Maps in ASCE 7-10 Commentary, App C


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Drift Limits for Seismic Provisions (ASCE 7 Table 12.12-1)

Maximum drift based on ASCE 7 provisions

Lateral Analysis for Seismic Loads

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d xex

CI

The R Factor in Moment Frame Design

ASCE 7 Design Coefficients (ASCE 7 Table 12.2-1)

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Seismic Design Principles

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Response Spectrum of MRFs

Reduction in Response Spectrum based on type of system used and its R factor

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Design Ground Motions

0

0.2

0.4

0.6

0.8

1

1.2

0 0.5 1 1.5 2 2.5 3

Period, T

Res

pons

e Ac

cele

ratio

n, g

Poll Question

The element to increase in size to most efficiently help you control drift in a moment frame is:

The Type of Weld Used in a ConnectionBeamsContinuity PlatesDoubler Plates

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Topics


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R=3 Moment Frame Systems

Not required to be designed for seismic resistanceTypically wind governed structureMembers (beams, columns, connections) designed for the LRFD or ASD load combinations in the building code LRFD ASD

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When are they allowedSeismic Design Category A, B, and C with no limits on heightStill must check some of the seismic requirements in Chapter 12 of ASCE 7

Overstrength Factor = 3Deflection amplification Factor = 3

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Use of AISC 360 for design of beams, columns, and connection elementsConnections designed for LRFD or ASD load combinationsTypically, EORs will delegate the connection design to fabricators with their in-house/connection design engineerEORs need to show/give design loads on drawings and indicate which force level shears and moments are shown

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Topics


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R=3.5 OMFs

When are they allowedSDC A, B, C with no restrictions

ASCE 7-10, Section 12.2.5.6Limitations on SDC D, E, and F: Allowed for lighter buildings Typically allowed up to 65 feet in height, but weight no more than 20 psf for floors and walls tributary to OMFMostly single story frames unless under 35 feetPermitted in light frame construction up to 35 feet where floor/roof load does not exceed 35 psf and wall load does not exceed 20 psf


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R=3.5 OMFs

Provides minimal inelastic deformation capabilitiesNo width-thickness ratios of members beyond what is required in AISC 360No protected zones on beamNo strong column-weak beam requirementsNo lateral bracing requirements except as required to meet AISC 360Must use Demand Critical Welds between beam flange and column where applicableConnection may be fully restrained(FR) or partially restrained (PR)

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R=3.5 OMFs

FR Connection must be designed for: Flexural strength of 1.1*Ry*Mp

Shear load of maximum moment from connection, Ev = 2[1.1*Ry*Mp]/Lcf

OR maximum flexural & shear load that can be delivered to the system based on strength of column/foundation upliftPanel zone requirements of Section J10.6 of AISC 360Continuity plate requirements of Sections J10.1-10.3 of AISC 360

PR Connections must be designed for minimum of:50%*Mp of beam for flexural strengthShear strength similar to FR OMF connection

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R=3.5 OMFs

When would you use an OMF in practice?Local code requires its use over R=3 systemEngineer wants to specify over IMF to avoid requirements in AISC 341At a connection where capacity of beam is required by code (ie. BRBF beam to column connection)Engineer wants control over lateral joint design/does not want to specify moments and shears at all lateral jointsLight gage/residential structure or small enclosed mechanical room at top of a building

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R=3.5 OMFs

Example of what an OMF looks like in practice

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Topics


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R=4.5 IMFs

When are they allowedASCE 7-10, Section 12.2.5.7

Limitations on SDC D: 35 feet in height or lighter buildingLimitations on SDC E, and F: lighter buildings Typically allowed up to 65 feet in height, but weight no more than 20 psf for floors and walls tributary to IMFMay be multi story frames in certain situationsPermitted in light frame buildings up to 35 feet where floor load does not exceed 35 psf and wall load does not exceed 20 psf


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R=4.5 IMFs

Provides limited inelastic deformation capabilitiesMembers must meet moderately ductile requirements within AISC 341Protected Zone requirements exist on beam/connectionNo strong column-weak beam requirementsLateral bracing requirements exist…~100*ry of moment frame beam for fy = 50ksi for moderately ductile beamsMust use Demand Critical Welds for:

Between beam flange and column where applicableColumn splice groove weldsWelds between column and base plate

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R=4.5 IMFs

Connection must be able to sustain story drift angle of 0.02 radians and flexural resistance must be 0.80*Mp at the 2% radiansRequired shear strength of connection:

Ev = 2[1.1*Ry*Mp]/Lh

Connections within AISC 358 may be used to justify conformance to performance requirementsPanel zone requirements similar to OMFs, Section J10.6 of AISC 360Continuity plates must follow requirements of SMF section

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R=4.5 IMFs

When would you use an IMF in practice?Local code mandates a minimum R valueSDC D with building no taller than 35 feet, BUT do not want to or cannot achieve SCWB, lateral bracing, provisions of AISC 341Short spans with Deep Beams, connections each have a span/depth ratio found in AISC 358Want to specify a connection on your drawings and get a small break in design spectrum, R=3.5 vs R=4.5Not very common…

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R=4.5 IMFs

Example of what an IMF looks like in practice

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Topics


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R=8 SMFs

When are they allowedAlways allowed…but can you get drift to work in your moment frame?

ASCE 7-10, No Limits on any height buildings

Overstrength Factor = 3Deflection amplification Factor = 5.5

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R=8 SMFs

Provides significant inelastic deformation capabilitiesMembers must meet highly ductile requirements within AISC 341Protected Zone requirements exist on beam/connectionStrong column-weak beam requirements existLateral bracing requirements exist…~50*ry of moment frame beam for fy = 50ksi for highly ductile beamsMust use Demand Critical Welds for:

Between beam flange and column where applicableColumn splice groove weldsWelds between column and base plate

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R=8 SMFs

Strong Column Weak Beam Requirements…why?

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Plastichinges

Deformed frame shape

Undeformedframe

L’

L

h

Drift angle -

Plastichinges

Deformed frame shape

Undeformedframe

L’

L

h

Drift angle -

R=8 SMFs

Connection must be able to sustain story drift angle of 0.04 radians and flexural resistance must be 0.80*Mp at the 4% radiansRequired shear strength of connection:

Ev = 2[1.1*Ry*Mp]/Lh

Connections within AISC 358 may be used to justify conformance to performance requirementsPanel zone requirements thickness based on t>(dz+wz)/90, doubler plates typically requiredColumn bracing requirements in AISC 341

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Comparison of OMF vs IMF vs SMF

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OMF IMF SMF Deformation Capabilities Minimal Limited Significant Story Drift Angle None specified 0.02 radians 0.04 radians

Connection Flexural Strength 1.1RyMp

Performance confirmed by testing per AISC 341, ChK; connection achieves

80%Mp at story drift angle = 0.02 radians

Performance confirmed by testing per AISC

341, Ch K; connection achieves 80%Mp at

story drift angle = 0.04 radians

Connection Shear Strength

V for load combination including overstrength plus shear from application of Emh = 2[1.1RyMp]/Lcf

V for load combination including overstrength plus shear from application of

Emh = 2[1.1RyMp]/Lh

V for load combination including overstrength

plus shear from application of Emh =

2[1.1RyMp]/Lh

Panel Zone Strength AISC 360, J10.6 AISC 360, J10.6 AISC 360, J10.6

Equations J10-11 & J10-12

Panel Zone Thickness AISC 360, J10.6 as required

AISC 360, J10.6 as required t>(dz+wz)/90

Comparison of OMF vs IMF vs SMF

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OMF IMF SMF

Continuity Plates As required by AISC 341, Section E1.6b

Match tested or AISC 358, Section 2.4.4 and E3.6f

Match tested or AISC 358, Section 2.4.4

and E3.6f

Beam-Column Proportions No requirements No requirements M*pc/ M*pb > 1.0

Width-Thickness Limitations AISC 360 AISC 341 Section D1.1, Moderately Ductile Member

AISC 341 Section D1.1, Highly Ductile

Member

Stability Bracing of Beams AISC 360 Bracing per AISC 341 for Moderately Ductile Member

Bracing per AISC 341 for Highly

Ductile Member

Column Splices AISC 360 AISC 341 Section D2.5 and E2.6g

AISC 341 Section D2.5 and E3.6g

Protected Zones Not required Yes, as governed by connection in AISC 358

Yes, as governed by connection in AISC

358

Topics


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Connection Design Principles & Failures

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Mu

VuT OR CV

T OR C

%Vu

%Vu

Connection Design Principles & Failures

Typical Failures in Moment Frame Connections

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Connection Design Failures

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Weld Element

Stresses

Through Thickness Column Flange Pull-Out

Column

Flange Stress Distribution

Beam Flange

Web Fracture due to Weak Panel Zone

Abrupt “divot” pull-outcolumn flange base metal

Brittle weld fracture due topeaked triaxial strains

Sudden column web fracture due to inherently weak panel zone

Divot ‘pull-out’ of column flange base metal

Brittle failure of girder flange weld of girder-to-column

weld connection

Beam-to-column weld failure propagates into column flange and web

Connection Design Principles

SAC: SEAOC, ATC, CUREELed to FEMA project after 1994 Northridge EarthquakeSeries of guides, FEMA 350-353 developed as a guide to use moment frame connections in buildingsEventually, AISC 358 published in 2005 with first set of prequalified connectionsCPRP, Connection Prequalification Review Panel in charge of reviewing and adding connections to AISC 358

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Connection Testing to Justify Performance

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-0.05 0.0 0.05-15

-10

-5

0

5

10

15

Total Plastic Rotation (rad.)

Mom

ent a

t Col

umn

Face

(x10

00 k

ip-in

)

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

M/M

pn

Topics


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Connection Types in AISC 358-05

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Number of Connections in AISC 358-053 connections totalIncluded: Reduced Beam Section (RBS), Bolted Unstiffened Extended End Plate, Bolted Stiffened Extended End Plate

Supplement Number 1 to AISC 358-053 additional connectionsIncluded: Bolted Flange Plate(BFP), Welded Unreinforced Flange-Welded Web(WUF-W), Kaiser Bolted Bracket (KBB)****First Proprietary Connection introduced


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Number of Connections in AISC 358-056 total connections


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Total number ofConnections in AISC 358

8Includes: Original six +

SidePlate** & ConXtech**(**Proprietary Conns)

Connection Types Added to AISC 358-10

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Common Connection Types in AISC 358

Reduced Beam Section (RBS)

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RBS Connection

Reduced Beam Section (RBS) Examples

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RBS Connection Limits

Beam limitsW36x Max, 300 lb/ft Max, bf = 1.75” Max

Span to depth7 or greater for SMF, 5 or greater for IMF

Column limitsW36x Max, Built Up or Rolled Shape, No Limit on Weight

Protected Zone = Face of Column to Edge of Reduced Beam Section CutReduced Beam Section Cut shall have surface roughness of 500 -in or better

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Common Connection Types in AISC 358

Welded Unreinforced Flange, Welded Web (WUF-W)

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Connection Types in AISC 358, WUF-W

Beam limitsW36x Max, 150 lb/ft Max, bf = 1” Max

Span to depth7 or greater for SMF, 5 or greater for IMF

Column limitsW36x Max, Built Up or Rolled Shape, No Limit on Weight

Protected Zone = Face of Column to One Beam DepthWeld access hole shall be per AWS D1.8

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WUF-W Connection

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Connection Types AISC 358 Summary

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Type of Connection SMF Span/Depth IMF Span/Depth

Reduced Beam Section (RBS) 7 5

Bolted Unstiffened Extended End-Plate 7 5

Bolted Stiffened Extended End-Plate 7 5

Bolted Flange Plate (BFP) 9 7

Welded Unreinforced Flange-Welded Web (WUF-W) 7 5

Kaiser Bolted Bracket (KBB) 9 9

ConXtech 7 5

SidePlate 4.5 3

Simpson Strong-Tie Strong Frame No Limits No Limits

Double Tee 9 9


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Type of Connection Beam Depth Limit Beam Weight

Limit Beam tbf Beam Width

Req. Reduced Beam Section (RBS) W36x 300 lb/ft 1.75" None

Bolted Unstiffened Extended End-Plate Table 6.1, AISC 358 None 1" None

Bolted Stiffened Extended End-Plate Table 6.1, AISC 358 None 0.75" None

Bolted Flange Plate (BFP) W36x 150 lb/ft 1" None

Welded Unreinforced Flange-Welded Web (WUF-W) W36x 150 lb/ft 1" None

Kaiser Bolted Bracket (KBB) W33x 130 lb/ft 1" 6" to 10" min

based on type of bracket

ConXtech W18x-W30x 132 lb/ft 1" 12" Max

SidePlate W40x** 302 lb/ft** 2.5" Typically 1.5-2" less than column

Simpson Strong-Tie Strong Frame W16x None 0.40" None

Double Tee W24x 55 lb/ft 0.625" None


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Type of Connection Column Depth

Limit Column Weight

Limit Column

tbf Reduced Beam Section (RBS) W36x None None

Bolted Unstiffened Extended End-Plate W36x None None

Bolted Stiffened Extended End-Plate W36x None None

Bolted Flange Plate (BFP) W36x None None

Welded Unreinforced Flange-Welded Web (WUF-W) W36x None None

Kaiser Bolted Bracket (KBB) W36x None None

ConXtech HSS 16x16 or 16"

Built Up Box Column

None 3/8" Min

SidePlate W44x None None

Simpson Strong-Tie Strong Frame W18x None None

Double Tee W36x None None


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Type of Connection Protected Zone Length First Lateral Brace

Reduced Beam Section (RBS) dbeam to end of RBS cut Near RBS cut, no greater than d/2 away

Bolted Unstiffened Extended End-Plate Lesser Of: dbeam OR 3*bf from face of column Per AISC 341

Bolted Stiffened Extended End-Plate Lesser Of: dbeam OR 3*bf from face of column Per AISC 341

Bolted Flange Plate (BFP) Plates and bolted flanges of beam + dbeam

No greater than 1.5dbeam away from face of column

Welded Unreinforced Flange-Welded Web (WUF-W) dbeam from face of column Between dbeam and 1.5dbeam

away from face of column

Kaiser Bolted Bracket (KBB) Plates and bolted flanges of beam + dbeam

Between dbeam and 1.5dbeam away from face of column

ConXtech dbeam to end of RBS cut Per AISC 341

SidePlate 0.833*dbeam past SidePlate** Per AISC 341 past end of SidePlate

Simpson Strong-Tie Strong Frame Yield Links, Shear Plate, and

portion of beam in contact with them

AISC 360

Double Tee Plates and bolted flanges of beam + dbeam

Between dbeam and 1.5dbeam away from farthest bolt

Poll Question

Which of the following is not prescribed in AISC 358 connections:

Protected Zone RequirementsRotation Capacity of ConnectionWhich Connection an Architect will like the mostSize limitation on beams and columns

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Learning Objectives

Identify how drift can be controlled in moment framesDifferentiate between R=3, OMF, IMF, and SMF lateral systemsIdentify when to use AISC 358 prequalified connections in moment frames

66

Moment Frames: Design and Detailingper AISC 341 and 358

By Matthew J. Mester, PE, SE

SidePlate Systems, Inc.

SE University, June, 2017 www.LearnWithSEU.com

CHALLENGE QUESTION:

Which type of Moment Frame System is the answer to this session’s Challenge Question?

A. R=3 Moment Frame SystemsB. R=3.5 Ordinary Moment Frame SystemsC. R=4.5 Intermediate Moment Frame SystemsD. R=8 Special Moment Frame Systems

Please circle the answer that is announced so that you can use the information to complete your quiz for PDH.

Documents

Lessons Learned in Structural Software: Implementing a ... · cannot achieve SCWB, lateral bracing, provisions of AISC 341 Short spans with Deep Beams, connections each have a span/depth