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AISC Live Webinar July 12, 2018

Stiffeners and Doublers – Oh My!

AISC Live Webinars Thank you for joining our live webinar today. We will begin shortly. Please stand by. Thank you. Need Help? Call ReadyTalk Support: 800.843.9166

There’s always a solution in Steel

AISC Live Webinars Today’s audio will be broadcast through the internet. Alternatively, to hear the audio through the phone, dial: (888) 378-4398

Passcode: 694105

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AISC Live Webinar July 12, 2018

Stiffeners and Doublers – Oh My!

AISC Live Webinars Today’s live webinar will begin shortly. Please stand by. As a reminder, all lines have been muted. Please type any questions or comments through the Chat feature on the left portion of your screen. Today’s audio will be broadcast through the internet. Alternatively, to hear the audio through the phone, dial: (888) 378-4398

Passcode: 694105

AISC Live Webinars AISC is a Registered Provider with The American Institute of Architects Continuing Education Systems (AIA/CES). Credit(s) earned on completion of this program will be reported to AIA/CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request. This program is registered with AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product. Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.

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Stiffeners and Doublers – Oh My!

AISC Live Webinars Copyright Materials This presentation is protected by US and International Copyright laws. Reproduction, distribution, display and use of the presentation without written permission of AISC is prohibited.

© The American Institute of Steel Construction 2018 The information presented herein is based on recognized engineering principles and is for general information only. While it is believed to be accurate, this information should not be applied to any specific application without competent professional examination and verification by a licensed professional engineer. Anyone making use of this information assumes all liability arising from such use.

Course Description Stiffeners and Doublers – Oh My! July 12, 2018 This webinar will present tips for avoiding costly doubler and stiffener detailing, along with good engineering practices that can make a big difference in the success of projects. The webinar will present a relative cost comparison between using stiffeners and doublers versus increasing member sizes. The latest requirements regarding doubler and stiffener design responsibilities will also be presented.

Copyright © 2018 American Institute of Steel Construction 3

AISC Live Webinar July 12, 2018

Stiffeners and Doublers – Oh My!

Learning Objectives • • •



List locations within a building structure where stiffener and doubler plates are utilized. Describe the cost implications of using stiffener and doubler plate details versus using larger member sizes. Describe how the responsibility of stiffener and doubler detailing is assigned on the project using guidelines provided in the 2016 AISC Code of Standard Practice for Steel Buildings and Bridges. Explain how to communicate design responsibility in the contract documents. Explain how to properly design stiffener and doubler plates according to the 2016 AISC Specification for Structural Steel Buildings.

Stiffeners and Doublers Oh My! Carol Drucker, S.E., P.E., P.Eng. Drucker Zajdel Structural Engineers, Inc.

8

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Stiffeners and Doublers Summary • • • • • • •

What are doublers? When are they required? Doubler Cost COSP and Doublers Doubler Design Stiffener Applications Stiffener Design Stiffeners and Doublers

9

What is a Doubler? • A doubler is a plate at a member web used to reinforce a section for the required load

Courtesy of Lyndon Steel Company

Stiffeners and Doublers

10

Copyright © 2018 American Institute of Steel Construction 5

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Stiffeners and Doublers – Oh My!

What is a Doubler? • A doubler plate is typically used to reinforce a column web panel zone B

B A

Stiffeners

A

Doublers Section A-A

Section B-B

Stiffeners and Doublers

11

Doublers • Other common applications – Coped beam web shear connections – Chevron connections – Truss Connections

a

a b

b

See Blodgett, Figure 41

Stiffeners and Doublers

12

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Stiffeners and Doublers – Oh My!

Why Doublers?

w

• Coped Beam to Girder – – – – –

Shear Yielding, Shear Rupture Block Shear Flexural Yielding, Flexural Rupture Flexural Buckling See Spec Part J and Manual Chapter 9

l

Capacity

V+ Doubler Force = Required Force – Strength of Section Stiffeners and Doublers

13

• Shear Flow at Top Edge of Doubler

C

C+dC

y2-y1

Shear Force and Stress v(t)(dz) dz

fv  t t

V (Q ) I (t )

See Salmon and Johnson, Steel Structures Design and Behavior

Element Shear Stress

Stiffeners and Doublers

14

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Stiffeners and Doublers – Oh My!

Shear Force and Stress • Shear Flow at Top Edge of Doubler Average web shear used for design of steel beams

fv 

V (Q ) I (t )

f avg 

V ( d )(tw )

Stiffeners and Doublers

15

Shear In a Member • Shear Flow at Top Edge of Doubler

fv 

Stiffeners and Doublers

V (Q ) I (t )

16

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Stiffeners and Doublers – Oh My!

Doubler Configurations • Doubler configurations commonly used: Prepped, Flush, and Offset • For flush doublers: use (1) doubler if thickness < 1/2” to 5/8”. • Doubler hierarchy (flush and prepped configurations): 1. Place on side without shear connection 2. Place on side with smaller beam framing into column web • Consider shear beam framing into doubler

Prep and Fillet Weld

Offset and Symmetric

Flush

Offset with Spacer Plate

Stiffeners and Doublers

17

Doublers • Design Guide 13

N1

BEVEL, IF REQUIRED

Kdet

ENCROACHMENT OF WEB DOUBLER PLATE INTO COLUMN FILLET PER 15th ED MANUAL FIGURE 10-3 GROOVE WELD MAY BE A NON-PREQUALIFIED DETAIL (SEE DG13 SECTION 4.4.3)

(A) GROOVE-WELDED DETAIL N1. RIDING THE K CAUSES A GAP BETWEEN THE DOUBLER AND FACE OF WEB

Kdet

teff AT TOE OF FILLET

ENCROACHMENT OF WEB DOUBLER PLATE INTO COLUMN FILLET PER 15th ED MANUAL FIGURE 10-3

(B) FILLET-WELDED DETAIL WITH PLATE BEVEL EQUAL TO PLATE THICKNESS

Stiffeners and Doublers

18

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Doubler Prep • Design Guide 13 Dmin 

0.6 Fy (treq ) 1.392

wmin  t req 2  (t dp  clip ) (tdp  clip ) Dreq  max( Dmin , wmin (16)) x



x  t req  (tdp  clip ) 2



(tdp  clip )

wmin

2  treq 2  2(tdp  clip )

Stiffeners and Doublers

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Flush Doublers: DG13 • Not a prequalified CJP weld

kdet - tfc ENCR. 5/16" 1/8" 3/8" TO 1/2" 3/16" 9/16" TO 13/16" 1/4" 7/8" TO 1 1/4" 5/16" 1 5/16" TO 1 3/8" 3/8"

• Design Guide 13 – tdp =1/4” to 3/8” max: • C-L1a or C-L1a-GF with square cut edges (or beveled) – tdp > 1/4” to 3/8”: • TC-U4a with beveled plates edges

tfc kdet

DOUBLER MAY ENCROACH INTO COLUMN FILLET BY ENCR. ABOVE, FABRICATOR TO CONFIRM

DOUBLER PLATE

Stiffeners and Doublers

20° TO 30°

20

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Flush Doubler: Seismic Provisions • Prequalified doubler weld added to 2016 AWS D1.8/D1.8M Clause 4.3 • AISC 341-16 Seismic Provisions designate this weld as a “full strength” PJP Groove Weld (See Comm E3) – Routine ultrasonic testing is not required – 1/16-in. gap permitted between doubler and column web – Required strength of weld = available shear yielding strength of doubler

Stiffeners and Doublers

21

Flush Doubler: AWS D1.8/D1.8M :2016

a

R

*AWS D1.8/D1.8M Clause 4.3: Decreased groove angle (a) and decreased root (R) require 3 macroetch test

Stiffeners and Doublers

22

Copyright © 2018 American Institute of Steel Construction 11

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Stiffeners and Doublers – Oh My!

Flush Doubler Welds at Column Radius tfc kdet

tfc

DOUBLER MAY ENCROACH INTO COLUMN FILLET BY ENCR. BY AISC ACCEPTABLE AMOUNT

kdet

DOUBLER MAY ENCROACH INTO COLUMN FILLET BY ENCR. BY AISC ACCEPTABLE AMOUNT

a

20.0°

20.0° TO 30° PJP WELD NO TESTING REQUIRED

PJP WELD NO TESTING REQUIRED. PREPARE A WELD PROCEDURE SPECIFICATION (WPS) AND CONFIRM FULL PENETRATION

Rweld=(0.75)(0.6)(Fexx )(E)

WELD PER AWS D1.8 CLAUSE 4.3

Rweld= FULL SHEAR STRENGTH

PJP WELD NO TESTING REQUIRED PER D1.8 CLAUSE 4.3

Rweld= FULL SHEAR STRENGTH

Stiffeners and Doublers

23

Shear In a Member • Exceptions at Chevron

y/2 MIN y Stiffeners and Doublers

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Stiffeners and Doublers – Oh My!

Shear In a Member • Exceptions at Chevron

Stiffeners and Doublers

25

Doubler Extension

W-SHAPED BEAM

COLUMN

COLUMN

BOLTED FLANGE PLATE WIND AND LOW SEISMIC EXT = 2.5 kdes

(6" MAX)

COLUMN

DIRECTLY WELD CONNECTION WIND AND LOW SEISMIC EXT = 2.5 kdes

W-SHAPED BEAM

EXT

EXT

EXT

W-SHAPED BEAM

EXT

EXT

EXT

• Doubler Extension

(6" MAX)

Stiffeners and Doublers

END PLATE CONNECTION WIND AND LOW SEISMIC EXT = 3 kdes + t p

(6" MAX)

26

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Stiffeners and Doublers – Oh My!

Doubler Extension Seismic

W-SHAPED BEAM

COLUMN

EXT

W-SHAPED BEAM

EXT

W-SHAPED BEAM

EXT

EXT

EXT

EXT

• Doubler Extension

COLUMN

COLUMN

BOLTED FLANGE PLATE HIGH SEISMIC

WELDED FLANGE HIGH SEISMIC

END-PLATE CONNECTION HIGH SEISMIC

EXT = 6"

EXT = 6"

EXT = 6"

Stiffeners and Doublers

27

Wind and Low Seismic • Doubler Termination

A

Size weld for 25% of stiffeners unbalanced force. See Design Guide 13

AISC minimum if no stiffeners

A Column Web Stiffener

Stiffener

Doubler Section A-A Stiffeners and Doublers

28

Copyright © 2018 American Institute of Steel Construction 14

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Stiffeners and Doublers – Oh My!

High Seismic • Doubler Termination

A

Develop 75% of the shear yielding strength of doubler

Weld not required except if Eq E3-7 is not satisfied by both column web alone and doubler plate alone (to limit buckling of the doublers)

t

( d z  wz ) 90

Eq. E3-7

A Column Web Stiffener

Stiffener

Doubler Section A-A Stiffeners and Doublers

29

Continuous Doublers • Doubler Termination Size weld for 50% of the stiffeners unbalanced force A A

Column Web

E3.6f.2(c): Connect for lesser of: - Sum of stiffener tensile strength - Available shear strength of stiffener - Available shear strength of doubler Doubler

Stiffener AISC minimum if no stiffeners

Wind and Low Seismic

Stiffener Weld not required, Comm. E3, pg. 9.1-240

Section A-A High Seismic Stiffeners and Doublers

30

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Stiffeners and Doublers – Oh My!

Cost of Doublers • Rule of Thumb (Per Seismic Design Manual): Upsizing columns between 50 to 100 lb/ft might still be more cost effective than installing doubler plates and continuity plates. • Cost of Steel = $800/ton average (FOB mill) ($881 for plate) http://stld-cci.com/ • Platts S&P Global is also a good source for price of steel Size

Stiffeners and Doublers

WT/FT

Price/cwt*

*cwt=hundredweight:31 100 lbs Multiply by 20 for $/ton

Cost of Doublers – DG13 (1999)

Stiffeners and Doublers

32

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Stiffeners and Doublers – Oh My!

Cost of Doublers tST , TYP A

• • • •

LRFD, Grade 50 Plates W14x90 Column W24x55 Moment Connected Beams M = 350 kip-ft NOTES: – 1/2” stiffeners required – 1/2” doubler required

A

W24x55 BEAM

W24x55 BEAM

1. GR50 STEEL 2. 14 FT FLOOR-TO-FLOOR (#) tDB

• Upsize to W14x109 Column

COLUMN TYP. WW WW

– Stiffeners not required – 3/8” doubler required

COL. WEB

DOUBLER

TYP. WF WF

• Upsize to W14x193 – Stiffeners not required – Doubler not required

WW

STIFFENER

TYP

SECTION A

STIFFENERS

Stiffeners and Doublers

33

Cost of Doublers Cost Comparison for Different Column Sizes

NOTES: 1. GR50 STEEL 2. 14 FT FLOOR-TO-FLOOR tST , TYP.

Stiffeners Column

A

Doublers

tST

Flange Weld WF

Web Weld WW

#

W14x90

1/2”

5/16”

5/16”

W14x90

1/2”

5/16”

W14x109

-

W14x109 W14x193

Cost Ratio

tDB

Doubler Weld WD

Weld Det.

1

1/2”

-

A

1.00

5/16”

1

1-1/2”

3/8”

B

0.75

-

-

1

3/8”

-

A

0.85

-

-

-

1

1-1/2”

5/16”

B

0.66

-

-

-

-

-

-

-

1.08

A

W24x55 BEAM

(#) tDB

W24x55 BEAM

COLUMN

OR

TYP.

20.0°

TYP.

DETAIL (A) GROOVE WELD

Stiffeners and Doublers

WD DETAIL (B) FILLET WELD

34

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AISC Live Webinar July 12, 2018

Stiffeners and Doublers – Oh My!

Who Checks for Doublers? • Code of Standard Practice – 2005 and 2010 COSP Section 3.1.1 3.1.1 Permanent bracing, column stiffeners, column web doubler plates, bearing stiffeners in beams and girders, web reinforcement, openings for other trades and other special details, where required, shall be shown in sufficient detail in the Structural Design Drawings so that the quantity, detailing and fabrication requirements for these items can be readily understood.

Stiffeners and Doublers

35

Who Checks for Doublers? • Code of Standard Practice – 2005 and 2010 COSP Section 1.1 1.1

In the absence of specific instructions to the contrary in the Contract Documents, the trade practices that are defined in this Code shall govern the fabrication and erection of the Structural Steel.

Stiffeners and Doublers

36

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Who Checks for Doublers?

TYP.

CJP

• Specific instructions to the contrary: – Contract documents can modify the COSP. For example, the Specification can indicate: “AISC’s COSP applies with the following modifications: Where reaction forces are given on the design drawings, Fabricator is responsible for designing stiffeners and/or doublers if necessary.”

CONTINUITY PLATES AS REQUIRED EACH SIDE OF COLUMN WEB TO MATCH THICKNESS OF BEAM FLANGES (SEE NOTE 1)

COLUMN

TYP.

PROVIDE WEB DOUBLER PLATES AS REQUIRED (SEE NOTE 1) NOTES: 1. PER THE PROVISIONS OF CHAPTER J OF THE AISC SPECIFICATIONS, PROVIDE COLUMN FLANGE STIFFENERS WHERE REQUIRED TO RESIST FORCES FROM MOMENT CONNECTIONS. PROVIDE COLUMN WEB DOUBLER PLATES AS REQUIRED FOR UNBALANCED MOMENT. ASSUME 20 KSI AXIAL STRESS IN COLUMNS FOR THE PANEL ZONE CHECKS

Stiffeners and Doublers

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Who Checks for Doublers? • Misleading Information: – Detail indicates stiffeners to be checked but not doubler – No loads given – No indication that Fabricator is to check for doublers on drawings or in Spec

Stiffeners and Doublers

38

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Stiffeners and Doublers – Oh My!

Who Checks for Doublers? • Current Code of Standard Practice – 2016 COSP (303-16) Section 3.1.2 » Option 3A: Member reinforcement (e.g. stiffeners, doubler, etc.) shall be designed by the owner’s designated representative and shown in the structural design documents issued for bid » Option 3B: Member reinforcement at connections is delegated design, but the quantities and conceptual configurations shall be provided and relied upon for bidding purposes. If no quantities or conceptual configurations are shown, member reinforcement at connections will not be included in the bid. Note: For Option 1 and 2, EOR designs stiffeners and doublers Stiffeners and Doublers

39

Check for Doublers Determine Column Panel Zone Shear Strength • AISC Clean Column:

www.aisc.org/cleancolumn

Stiffeners and Doublers

40

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Doublers at Lateral Moment Connections - FBD Inflection point assumed at h/2

Pf1 = Mb1/db1

Pf1 +Pf2

Vc = ∑(Mb)/h Stiffeners if required

Vc

Pf2 = Mb2/db2

Mc Vp Mc

h

Panel Zone, Doublers if Required Vc

Vp = Panel Zone Shear = Pf1 + Pf2 - Vc

Vc

Shear

Moment

Stiffeners and Doublers

41

Forces from 3D Analysis

Vc Mc

Mc Vc

Shear Stiffeners and Doublers

Moment 42

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Check for Doublers Determine Column Panel Zone Shear Strength • Must Have

P

– Beam Moments

• Best to Have – Break Down of Beam DL, LL, and Lateral Moments – Column Axial Load

Stiffeners and Doublers

43

Deflected Shape

Joint moments Typ.

Lateral

Gravity

Stiffeners and Doublers

44

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Stiffeners and Doublers – Oh My!

Deflected Shape

Joint moments Typ.

Lateral

Gravity

Stiffeners and Doublers

45

Moment Connections – Doublers • ∑M = 0 ∑(Mb) < ∑(Mc) • Sum of beam moments can not exceed sum of column moment strengths Vp max = Panel Zone Shear = 2(Mc)/db - 2(Mc)/h

Stiffeners and Doublers

46

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Moment Connections – Doublers • ∑M = 0 ∑(Mb) < Mc

Top of Column

• At top of column, sum of beam moments can not exceed column moment strength Vc max = Panel Zone Shear = Mc/db

Stiffeners and Doublers

47

Moment Connections – Doublers • Add dead and lateral loads on both sides • Add live load on one side MD2 MLAT2

MD1 ML1 MLAT1

Stiffeners and Doublers

48

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Moment Connections – Doublers

Column Web Doublers Loading Criteria

% Columns Requiring Doublers

Full Moment Beam, Limited to Strength of Column

100%

Actual Moments Given with No Break Down

79%

Actual Moments Given with Break Down

26%

Stiffeners and Doublers

49

Give Actual Loads

1 ½” Stiffeners on a W14x90 Column

Courtesy of Larry Muir and Bill Thornton

Stiffeners and Doublers

50

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Check for Doublers Determine Column Panel Zone Shear Strength, J10.6   0.9   1.67

• Elastic Range:

aPr  0.4 Py : R n  0.6 Fy d c tw  aP aPr  0.4 Py : R n  0.6 Fy d c tw  1.4  r  Py 

Pr (J10-9)

  

(J10-10)

• Plastic Range:

 3bc f tcf2 aPr  0.75 Py : R n  0.6 Fy d c t w  1   ddt b c w 

   2  3b t   1.2a Pr aPr  .75 Py : R n  0.6 Fy d ct w  1  c f cf   1.9   d d t  Py b c w  

(J10-11)   

(J10-12)

• http://risa.com/news/code-requirements-for-panel-zone-shear-deformation/ Stiffeners and Doublers

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Check for Doublers Determine Column Panel Zone Shear Strength • Force in Doubler Vdoubler = SPf –Vc –Rn Vdoubler = SPf –Vc–Rn/

LRFD ASD

Pf

• Size of Doubler

d

Pf

– AISC Specification Eq. G2-1 Use ”d” of column

Vn  (0.6 Fy AwCv1 )

Vn   (0.6 Fy AwCv1 ) 

Stiffeners and Doublers

52

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Check for Doublers Determine Column Panel Zone Shear Strength • Consider beam shear when beam frames into doubler Pf=M/dm

H=Vg (x)/ dm Vg

Vg

V=Pf (dm)/x1

Vg V=Pf (dm)/x1

0.5Vg

0.5Vg

H=Vg (x)/ dm Alternate 1 Distribution

M

x

x1

Pf=M/dm

Alternate 2 Distribution, DG13

Stiffeners and Doublers

53

Doubler Web Buckling • Wind and Low Seismic Doublers: Minimum thickness to prevent shear buckling (Spec Section G2): h  2.24 E / Fy t



t =

h Fy

W-SHAPED BEAM

381

h  d c  2 kdes t = thickness of web doubler Alternatively, use plug welds and the total thickness (t= thickness column web + thickness doublers) can be used COLUMN

Stiffeners and Doublers

54

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Doubler Web Buckling • DG13 is per 1993 Spec which  = 0.9 versus  = 1.0 in 2016 Spec for Shear

t

t

h Fy 418 127 Fy

W-SHAPED BEAM

1993 LRFD, Section F2 Engineering for Steel Construction, 1984 Based on 1978 Spec Section 1.18.2.3 for Compression of COLUMN

Built-up Members Stiffeners and Doublers

55

Doubler Web Buckling • High Seismic Doublers wz

( d z  wz ) 90 d z  d b  2 tbf t

dz

W-SHAPED BEAM

wz  d c  2 tcf Where: t = thickness of column web or individual doubler

COLUMN

Stiffeners and Doublers

56

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Doubler Web Buckling • High Seismic Doublers with plug welds ( d z  wz ) 90

W-SHAPED BEAM

dz

t

wz

Where: t = thickness of column web + thickness of individual doublers

Stiffeners and Doublers

57

Moment Connections • Consider load path and equilibrium

Panel Zone Shear

• Same depth beams at cantilevers with equal and opposite moments do not need to be checked for doublers Stiffeners and Doublers

58

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Stiffeners • Stiffener Plates

B

B A

Stiffeners

A Doublers Section A-A

Section B-B

Stiffeners and Doublers

59

Stiffeners • Other Common Applications

Column Bearing on Beam

Beam over Top of Column

Stiffeners and Doublers

Chevron Connections

60

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Stiffeners • Other Common Applications

Stability (J10.7)

To Direct Force Stiffeners and Doublers

61

Stiffeners • Stiffeners, Spec J10.8 B

3



twc 2

b

bf

twc

b

– Minimum thickness, t:

t

B

bf

– Minimum width, b:

tf

Section B-B

2 b t 16 Where: tf (thickness) and bf (width) are for the element delivering the force

Stiffeners and Doublers

62

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Stiffeners • Limiting Stiffener Slenderness – Minimum width, t > b/16:

Simply Supported

• For plates with one free edge: 2

t  cr    0.769 Dx D y  0.270( Dxy  D yx )  1.712Gt  b

Dx  8, 000 ksi D y  31, 000 ksi

bs

Fixed

Dxy  16, 000 ksi Gt  2, 400 ksi

x

 cr  33 ksi bs  15.2  16 ts

Free

y

Simply Supported

cr

Reference: Welded Interior Beam-to-Column Connections, AISC

Stiffeners and Doublers

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Stiffeners • Stiffeners, Seismic Provisions – Minimum width, b:

B

B

bf

t b  wc 2 2

t

2 3t f 4

One sided connections Two sided connections

b

tf

twc

t

bf

– Minimum thickness, t:

Section B-B

Stiffeners and Doublers

64

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Stiffeners • Stiffeners – Minimum Length

ds

• AISC 360-16 Specification Section J10: – Transverse stiffeners shall extend a minimum of one-half the depth of the member except as required in Section J10.3 (WC)*, J10.5(WB), and J10.7(Unframed ends of beams not restrained against rotation about their longitudinal axis) *To satisfy web crippling strength, ½-depth stiffener increased to ¾-depth in the 15th Edition based on EJ 4th Qtr, 2015, Crippling of Webs with Partial-Depth Stiffeners under Patch Loading, by Salkar, et al

– Avoid welding stiffeners on 3-sides if possible, terminate at kdet for fabrication cost savings Stiffeners and Doublers

65

Stiffeners • Stiffeners – Designing Partial Depth Stiffeners

b' • Reference EJ 4th Qtr, 2015, “Crippling of Webs with PartialDepth Stiffeners under Patch Loading” by Salkar, et al

a' 15th

• Reference for brackets

Manual Ed, Fig 15-2

Stiffeners and Doublers

66

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Stiffeners • Stiffener Clips – Gravity, Wind, and Seismic R=3 • Stiffeners should clear kdet and k1 • k-area (1-1/2” from k) is area of potentially lower notch toughness in rotarystraightened W-Shapes, see Commentary J10.8

Fig C-J10.8: Recommended placement of stiffener fillet welds to avoid contact with “k-area”

• Tests show a corner clip of 1-1/2” with fillets stopped short by (1) weld size can avoid this problem Fig C-J10.7:

Can reduce to ¾” at flanges for additional weld length

Representative “k-area” of wide-flange shape

67

Stiffeners • Seismic Stiffener clips – Seismic Provisions: • Reference AWS D1.8/D1.8M, Clause 4.1 – At web: Extend 1-1/2” min beyond kdet – At flange: Not to exceed 1/2” beyond k1 – Shall facilitate suitable weld termination – If curved, r = 1/2” min • Welding in the k-area should be avoided

Stiffeners and Doublers

AISC’s Seismic Provisions, Fig C-D2.3:

68

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Stiffeners/Continuity Plates • Flange Welds – AISC Specification Section J10.8 • Welds to be sized for the difference between the required strength and available strength.

FILLET

S (E)

– AISC’s Seismic Provision • Shall be CJP Welded per E3.6f2(c)

PJP

CJP

Stiffeners and Doublers

69

Stiffeners/Continuity Plates • Web Welds – Design Guide 13 • Weld for unbalanced stiffener force – AISC’s Seismic Provision • E3.6f.2(c): Connect for lesser of: - Sum of stiffener tensile strength at column flanges - Available shear strength of stiffener at column web - Available shear strength of column web (or doubler if doubler extended)

Stiffeners and Doublers

FILLET

S (E)

PJP

CJP

70

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Stiffeners/Continuity Plates • Stiffener Design – AISC Specification Chapter J Pstiffener = Pf – minimum Rn Pstiffener = Pf – minimum Rn/

LRFD ASD W-SHAPED BEAM

Rn is the minimum nominal strength for the applicable limit states – If kl/r < 25, yielding (k = 0.75) (J4.4) If kl/r > 25, see Spec Chapter E

COLUMN

Stiffeners and Doublers

71

Stiffener Design • Flange Local Bending – AISC Specification Section J10.1, Eq. J10-1

Load width

Rn  6.25 Fyf t 2f   0.90 (LRFD)

  1.67 (ASD)

– Applicable to tension load only – Not applicable if load width is less than 0.15bf – Reduce Rn by 50% if force is applied less than 10tfc from end of column Stiffeners and Doublers

See Blodgett 5.7-8

72

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– AISC Specification Section J10.2

2.5

5kdes+lb

1

• Web Local Yielding Rn  Fywtw  5kdes  lb 

lb

Stiffeners

Spec Equation J10-2 k des

Rn  Fywtw  2.5kdes  lb  Spec Equation J10-3, Force  d from end of column   1.50 (ASD)

lb = bearing length, in.

W14x90 COL

  1.00 (LRFD)

W24x55 BEAM

d Stiffeners and Doublers

73

Stiffeners • Web Local Crippling – AISC Specification Section J10.3

 l Rn  0.80t  1  3  b  d 

  tw    tf

 l Rn  0.40t  1  3  b  d    4l Rn  0.40t w2  1   b   d    0.75 (LRFD)

  tw    tf

2 w

2 w

1.5

  

 EF t yw f  Qf  tw 

1.5

 EF t yw f  Qf  tw  1.5  EF t  t  yw f  0.2   w   Qf   t  t  f  w    2.00 (ASD)   

Spec Equation J10-4, Force applied distance > d/2 from end of member Spec Equation J10-5a, Force applied distance < d/2 from end of member, lb/d<0.2 Spec Equation J10-5b, Force applied distance < d/2 from end of member, lb/d>0.2 See Section J10.3 for Qf definition

Stiffeners and Doublers

74

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Stiffeners • Web Compression Buckling – AISC Specification Section J10.5, Eq. J10-8

Rn 

24tw3 EFyw

  0.90 (LRFD)

h

Qf

  1.67 (ASD)

– Reduce Rn by 50% if force is applied less than d/2 from end of column

W24x55 BEAM

Stiffeners and Doublers

W14x90 COL

– Applicable to double-concentrated forces at the same location

W24x55 BEAM

75

Stiffeners • Web Compression Buckling – Equation J10.8 developed from point loads and restrained flanges – If lb/d > approximately 1, Use Chapter E – See Chapter C and Appendix 6 for Stability

Test Set-up from Chen and Oppenheim 1970

Stiffeners and Doublers

See Spec Appendix Section 6.2.2 for point bracing (nodal bracing) required strength and stiffness

76

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Stiffeners/Continuity Plates • Stiffener Design – AISC’s Seismic Provision • Also Required if tcf < bbf/6

Eq (E3-8) W-SHAPED BEAM

COLUMN

Stiffeners and Doublers

77

Stiffener Eccentricity • DG13 which references testing by Graham, et al (1959), indicates stiffeners with 2” eccentricity, e, are 65% effective, reduced linearly: Rn_emax = 0.65 Rn

Stiffeners and Doublers

e

• Further research discussed for eccentric stiffeners

e

• Can slope stiffener if stiffener not needed for beam-to-column web moment connection

e = 2" MAX

78

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Web Sidesway Buckling – Beams • Web Sidesway Buckling (J10.4) – AISC Specification Eq. J10-6 and J10-7 3 Equation J10-6,  h / tw   Cr t w3 t f    Compression Flange Rn  1  0.4    L /b   h2  restrained, applicable if b f     (h/tw)/(Lb/bf)<2.3

Cr t w3 t f   h / t w  0.4  Rn  h 2   Lb / b f 

  

3

   

Equation J10-7, Compression Flange not restrained, applicable if (h/tw)/(Lb/bf)<1.7 AISC Commentary, Fig.C-J10.2 Web sidesway buckling

  0.85 (LRFD)   1.76 (ASD) • Compression flange braced, tension flange unbraced • Lb = largest laterally unbraced section along either flange at the point of load. Stiffeners and Doublers

79

tst

Web Buckling - Girders tw

• Additional Stiffener Requirements for Beam and Girder Flange(s) – AISC Specification Section J10.8

beff =25tw AT

• Check web and stiffeners as column section with kl = 0.75h (see Spec Sections

E6.2, J4.4)

INTERIOR

tst

A

tw

A

• beff = 25 tw at interior 12 tw at ends of members

– For fabrication cost savings, fit one side of stiffener to bear at flange and transfer force at opposite end of stiffener by weld Stiffeners and Doublers

beff =12tw AT EXTERIOR Section A-A 80

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Stiffener & Doubler Example • Given: – Distance to end of column much larger than column depth – W Shapes ASTM A992, Fy = 50 ksi

-

Plates Grade 50, Fy = 50 ksi AISC Specification 360-16 AISC 15th Edition, LRFD ASCE 7-10 R= 3 Wind determined not to control

MD1 = 130 kip-ft

MD1 ML1 ME1 W27x94

W14x176

ML1 = 220 kip-ft ME1 = 690 kip-ft MD2 ML2 ME2 W27x94

MD2 = 130 kip-ft ML2 = 220 kip-ft ME2 = 690 kip-ft 81

Stiffeners and Doublers

Stiffener & Doubler Example • Find: – Check if stiffeners are required. If required, size the stiffeners. – Check if doublers are required. If required, size the doublers.

W14x176

Stiffeners if required

W27x94

W27x94

Panel Zone, Doubler if Required 82 Stiffeners and Doublers

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Stiffener & Doubler Example • Solution: – 1. ASCE 7-10, Load Combinations for Strength Design

1. 1.4D 2. 1.2D + 1.6L + 0.5(Lr or S or R)

= 182 kip-ft = 508 kip-ft

3. 1.2D + 1.6(Lr or S or R) + (L or 0.5W) 4. 1.2D + 1.0W + L + 0.5(Lr or S or R)

= 376 kip-ft = 376 kip-ft

5. 1.2D + 1.0E + L + 0.2S 6. 0.9D + 1.0W

= 1070 kip-ft = 117 kip-ft

7. 0.9D + 1.0E

= 807 kip-ft

MD1 = 130 kip-ft ML1 = 220 kip-ft ME1 = 690 kip-ft MD2 = 130 kip-ft ML2 = 220 kip-ft ME2 = 690 kip-ft

Governing Load Combination: 5. 1.2D + 1.0E + L + 0.2S M1 = M2 = 1.2(130 kip-ft) + 1.0 (690 kip-ft) + 1.0(220 kip-ft) = 1070 kip-ft 83 Stiffeners and Doublers

Stiffener & Doubler Example • Solution: – 2. Determine Each Beam’s Flange Force

Mu d  t pl

Pfl 

Mu d  t fb

Pfl1

Pfl2

Flange Plate

Directly welded W27x94 BEAM

W14x176 COL

Pfl 

W27x94 BEAM

84 Stiffeners and Doublers

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Stiffener & Doubler Example • Solution: – 2. Determine Each Beam’s Flange Force

M1 d b  tf b 1070 kip-ft  26.9in. - 0.745 in.  491kips

W27x94 BEAM

Pfl2

W14x176 COL

Pfl1

Pfl  Pfl 1  Pfl 2 

W27x94 BEAM

85 Stiffeners and Doublers

Stiffener & Doubler Example • Solution: – 3. Check Stiffener Limit States • Web Local Yielding (J10.2)

   1.00 

– AISC Specification Eq. J10-2

Rwy  Fywtwc  5kdesc  lb   427 kips < Pfl  491kips n.g. Stiffeners Required

W27x94 BEAM

W14x176 COL

 1.00  50 ksi  0.830 in.  5 1.91in.   0.745in.  W27x94 BEAM

Note : lb  t fb

86 Stiffeners and Doublers

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Stiffener & Doubler Example • Solution: – 3. Check Stiffener Limit States • Web Local Crippling (J10.3)

   0.75 

– AISC Specification Eq. J10-4

Rwc

1.5    lb   t wc   EFyc t fc   0.80t 1  3      t wc  dc   t fc     1.5   0.745in.   0.830 in.   2  0.75(0.80)  0.830 in. 1  3       15.2 in.   1.31 in.    2 wc

 29000 ksi  50 ksi 1.31in.  0.830in.

 672 kips  Pfl  491kips o.k.

Note : lb  t fb 87 Stiffeners and Doublers

Stiffener & Doubler Example • Solution: – 3. Check Stiffener Limit States • Web Compression Buckling (J10.5)

   0.90 

– AISC Specification Eq. J10-8

Rwb  

24t w3 c EFyc

 (0.90)

h

W14x176 COL

h  dc  2kdesc  15.2in.  2 1.91in.  11.4 in. Qf

24  0.83in.

3

 29000 ksi  50 ksi 

11.4 in.  1305 kips  Pfl  491kips o.k.

(1.0)

W27x94 BEAM

W27x94 BEAM

88 Stiffeners and Doublers

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Stiffener & Doubler Example • Solution: – 3. Check Stiffener Limit States • Flange Local Bending (J10.1)

   0.90 

– AISC Specification Eq. J10-1

R fb  6.25 Fyc t 2fc  0.90  6.25  50 ksi 1.31in.

2

 483 kips < Pfl  491kips n.g. Stiffeners Required

See Blodgett 5.7-8

89 Stiffeners and Doublers

Use of Manual Tables • Web Local Yielding

   1.00 

– AISC 15th Edition Manual Eq. 4-2a

396 41.5 1310 483 Rn  Pwo  Pwilb kips    396 kips   41.5   0.745in. in.    427 kips  Pfl  491kips n.g. Stiffeners Required

90 Stiffeners and Doublers

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Use of Manual Tables • Web Local Crippling

   0.75 

– AISC 15th Edition Manual Eq. 9-50a

Rn  2  R3  lb  R4    kips     2 313kips   0.745in.  31.1  in.      672 kips  Pfl  491kips o.k.

91 Stiffeners and Doublers

Use of Manual Tables    0.90 

• Web Compression Buckling

– AISC 15th Edition Manual Eq. 4-3a

396 41.5 1310 483

Rn  Pwb  1310 kips  Pfl  491kips o.k.

92 Stiffeners and Doublers

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Use of Manual Tables • Flange Local Bending

   0.90 

– AISC 15th Edition Manual Eq. 4-4a

396 41.5 1310 483

Rn  Pfb  483 kips  Pfl  491kips n.g. Stiffeners Required

93 Stiffeners and Doublers

Stiffener & Doubler Example

lst

• Solution:

bst

– 4. Column Stiffener Design • Determine Force in the Stiffeners

Pst1tot  Pst 2tot  Pfl  min(Rwy , Rwc , Rwb , Rfb)  491 kips  427 kips

Snip

= 64 kips • Determine Beam Force Per Each Stiffener

Pst 1  0.5( Pst1tot )  0.5(64 kips) = 32 kips Pst 2  0.5( Pst 2tot )  0.5(64 kips) = 32 kips

94 Stiffeners and Doublers

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Stiffener & Doubler Example • Solution:

bst

– 4. Column Stiffener Design • Determine Minimum Stiffener Width per AISC’s Specification, Section J10.8

Snip

bfb twc 10 in. 0.83 in.     2.92in. Min. (See Note below) 3 2 3 2 bfc  twc 15.7 in.  0.830 in. bst max    7.44in. Max 2 2 bst min 

Use bst = 7" Stiffener *Note: Use bpl in lieu of b fb if moment connection plate delivering the load 95 Stiffeners and Doublers

Stiffener & Doubler Example • Solution:

bst

– 4. Column Stiffener Design • Determine Minimum Stiffener Thickness per AISC’s Specification, Section J10.8

tst min 

bst 7 in.   0.438in. 16 16

tst min 

tfb 0.745 in.   0.373 in. 2 2

Snip

Controls (See Note below)

• Try a 1/2” Stiffener

*Note: Use t pl in lieu of t fb if moment connection plate delivering the load 96 Stiffeners and Doublers

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Stiffener & Doubler Example

lst

• Solution: • Check Minimum Thickness Due to Tension Yielding – AISC Specification Section J10.8

snip  max(k det c  tfc, k 1c 

twc ,1.5 in.) 2

 max(2.625 in.  1.31 in., 1.625 in. 

bst

– 4. Column Stiffener Design Snip

0.83 in. ,1.5 in.) 2

 1.5 in. Pst Fyp (bst  snip ) 32 kips  0.90(50 ksi)(7 in.  1.5 in.) = 0.129 in.  0.5 in. o.k.

tst min 

*Note: Can reduce snip at flange if needed. 97

Stiffeners and Doublers

Stiffener & Doubler Example – 4. Column Stiffener Design • Check Minimum Thickness Due to Compression Buckling – AISC Specification Section J10.8 and E3    0.90 

bst

lst

• Solution:

lst  dc  2tfc  15.2 in.  2(1.31 in.) = 12.6 in. k  0.75 kl klst 12 0.75(12.6 in.) 12    65.5 r tst (0.5 in.) Limit  4.71 Fe 

2 E

 r kl

2



E 29,000 ksi  4.71  113 Fyp 50 ksi π 2 (29,000 ksi)

 65.5

2

 66.6 ksi 98

Stiffeners and Doublers

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Stiffener & Doubler Example – 4. Column Stiffener Design • Check Minimum Thickness Due to Compression Buckling – AISC Specification Section E3    0.90  50 ksi Fyp     Fcr   0.658 Fe  Fyp   0.658 66.6 ksi  50 ksi  36.5 ksi       Fcr  0.90(36.5 ksi) = 32.9 ksi

bst

lst

• Solution:

(E3-2)

Rearrange Pn  FcrAg to Solve for tst min (E3-1) Pst tst min  Fcr (bst ) *Note: Buckling limit state included for example purposes. 32 kips  (32.9 ksi)(7 in.) = 0.139 in.  0.5 in. o.k. 99

Stiffeners and Doublers

Use of Manual Tables – AISC Manual Table 4-14: KL/r Table 65 22.0 33.0 66 21.8 32.7

Stiffeners and Doublers

100

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Stiffener & Doubler Example • Solution:

Lwf

– 4. Column Stiffener Design • Weld Design of Stiffener to Column – AISC Specification Section J2

Lww

Snip

Lww  lst  2 snip  12.6 in. - (2)1.5 in. = 9.6 in. Lwf  bst  snip  7 in. - 1.5 in. = 5.5 in.

  0.928 ASD   1.392 LRFD D min fl 

Pst 32 kips  = 1.39 (16th of an inch) (2) Lwf (1.5) 1.392(2)(5.5 in.)(1.5) 1/4” Fillet Weld o.k. 101 Stiffeners and Doublers

Stiffener & Doubler Example • Solution: – 4. Column Stiffener Design

Note : 0.928 D  (0.6)( Fexx )(0.707)( w) / 

w D  (0.60)(70 ksi)(0.707)   / 2  0.928 D  16  D 1.392 D  (0.6)( Fexx )(0.707)( w)     16  w D  (0.60)(70 ksi)(0.707)   (0.75)  1.392 D  16  1.5  1.0  0.5(sin())1.5  1  0.5(sin(90))1.5  1.5

Reference Spec Eq (J2 - 5) 102

Stiffeners and Doublers

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Stiffener & Doubler Example • Solution: – 5. Determine Flange Forces for Column Doubler Checks • Based on ASCE 7 Load Cases • Determine sum of flange forces for each load load combination. Consider symmetric gravity moments and pattern loading if applicable

ASCE 7-10 1. 1.4D

MD1 = 130 kip-ft

2. 1.2D + 1.6L + 0.5(Lr or S or R)

ML1 = 220 kip-ft ME1 = 690 kip-ft

3. 1.2D + 1.6(Lr or S or R) + (L or 0.5W ) 4. 1.2D + 1.0W + L + 0.5(Lr or S or R )

MD2 = 130 kip-ft

5. 1.2D + 1.0E + L + 0.2S 6. 0.9D + 1.0W

ML2 = 220 kip-ft ME2 = 690 kip-ft

7. 0.9D + 1.0E 103 Stiffeners and Doublers

Stiffener & Doubler Example • Solution: – 5. Determine Flange Forces for Column Doubler Checks • Determine Critical Load Combination:

Governing Load Combination 5: M 1_ 5 = 1.2(130 k-ft) + 1.0 (690 k-ft) + 1.0(220 k-ft) = 1070 kip-ft M 2_ 5 = 1.2(-130 k-ft) + 1.0 (690 k-ft) = 534 kip-ft

MD1 = 130 kip-ft

Pfl1_ 5 

M1 1070 kip-ft   491 kip db1  tfb1 26.9 in. - 0.745 in.

ML1 = 220 kip-ft ME1 = 690 kip-ft

Pfl 2 _ 5 

M2 534 kip-ft   245 kip (Stiffener not required) db 2  tfb 2 26.9 in. - 0.745 in.

MD2 = 130 kip-ft

Pfd  Pfl1_ 5  Pfl 2 _ 5  491 kips  245 kips  736 kips

ML2 = 220 kip-ft ME2 = 690 kip-ft 104

Stiffeners and Doublers

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Stiffener & Doubler Example • Solution: – 5. Determine Flange Forces for Column Doubler Checks • Confirm column strength does not control:

SM b = M 1_ 5 +M 2 _ 5 = 1070 kip-ft + 534 kip-ft = 1604 kip-ft 0.9(320 in.3 )(50 ksi) = 1200 kip - ft 12in. / ft = 1200 kip-ft + 1200 kip-ft = 2400 kip-ft

M nc  ( Z xc )( Fyc )  SM c = M c _ t +M c _ b

SM b = 1604 kip-ft < SM c  2400 kip-ft

Beams Control

105 Stiffeners and Doublers

Stiffener & Doubler Example • Solution: – 6. Determine Panel Zone Shear Reduction Due to Column Shear

Pfd

Vc

hcol  15 ft M  M2 Vc  1 hcol 1070 kip - ft + 534 kip - ft  15 ft  107 kips

Vc Pfd1 M1

M2

h

Vp  Pfd  Vc  736 kips  107 kips  629 kips

Pfd2

Vc

Vp

Vc Shear 106 Stiffeners and Doublers

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Stiffener & Doubler Example • Solution: – 7. Column Doubler Check

   0.90 

ᶲRn

• Web Panel Zone Shear Strength – AISC Specification Section J10.6

a  1.0 (LRFD); 1.6 (ASD) W27x94 BEAM

aPr  (1.0)870 kips = 870 kips LRFD

W27x94 BEAM

Py  Fyc Agc  (50 ksi)(51.8 in.2 ) 2590 kips aPr (1.0)870 kips   0.336  0.4 Py 2590 kips

W14x176 COL

Since aPr  0.4 Py : R n  0.6 Fy d ct w

(J10-9) 107

Stiffeners and Doublers

Stiffener & Doubler Example • Solution: – 7. Column Doubler Check

   0.90 

ᶲRn

• Web Panel Zone Shear Strength – AISC Specification Section J10.6

Rn  0.6 Fywt wc dc W27x94 BEAM

 0.90(0.6)(50 ksi)(0.830 in.)(15.2 in.)

W27x94 BEAM

 341 kips W14x176 COL

Vp  629 kips > Rn  341 kips

n.g.

Doubler Required Stiffeners are not required

108 Stiffeners and Doublers

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Stiffener & Doubler Example • Solution: Vd

– 7. Determine Doubler Shear Force

Vd  Vp  Rn  629 kips  341 kips  288 kips Number of Doublers, nd = 1

W27x94 BEAM

Panel Zone, Doubler Required

W27x94 BEAM

W14x176 COL

109 Stiffeners and Doublers

Stiffener & Doubler Example • Solution: – 8. Column Doubler Design • Minimum Doubler Thickness to prevent Shear Buckling – AISC Specification Section G2.1

For, Cv = 1.0

td min 1 

h 2.24

Fyp dc  2kd esc  E 2.24

Fyp 15.2 in.  2(1.91in.) 50 ksi   0.211 in. E 2.24 29, 000 ksi

110 Stiffeners and Doublers

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Stiffener & Doubler Example • Solution: – 8. Column Doubler Design • Doubler Thickness Due to Panel Zone Shear – AISC Specification Equation G2-1

   1.00 

Vd (Cv ) (0.6)( Fyp )(dc )( nd ) 288 kips(1.0)  (1.00)(0.6)(50 ksi )(15.2 in.)(1)  0.632 in.

td min 2 

111 Stiffeners and Doublers

Stiffener & Doubler Example • Solution: – 8. Column Doubler Design • Doubler Vertical Edge Thickness Due to Beam-to-Column Web Shear Connection, Reference AISC’s Spec Equation J4-3

td min 3 

   1.00 

0.5Vconn ' x (0.6)( Fyp )( Ld )

0.5(0 kips)  0.0 in. 1.00(0.6)(50 ksi)(26.9 in. - 0.745 in. - 0.5 in.) Where : Ld  length of doubler  db  tfb  ts

td min 3 

td

min

Vconn’x

= max(td min 1, td min 2  td min 3) = max (0.211 in., 0.632 in. + 0 in.) = 0.632 in.

Use (1) PL 3/4" or (2) PL 3/8"

112

Stiffeners and Doublers

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Stiffener & Doubler Example • Solution: – 8. Column Doubler Design

   1.00  Lwf

• Doubler Horizontal Edge Thickness Due to Unbalanced Stiffener Force

Pst 1  Pst 2 td min 4  (0.6)( Fyp )( Lww )(2)

Lww

Ref Spec Eq (J4-3) Snip Pst2

Pst1

32 kips + 0 kips (1.00)(0.6)(50 ksi)(9.6 in.)(2)  0.056 in. < 3/4" o.k. 

113 Stiffeners and Doublers

Stiffener & Doubler Example – 8. Column Stiffener Thickness for Shear

   1.00 

• Check Minimum Thickness Due to Unbalanced Stiffener Force

bst

lst

• Solution:

Snip

Rearrange Rn  0.6 FypAgv to Solve for tst min

Ref (J4-3)

Pst 1  Pst 2 (0.6) Fyp (lst  2( snip)) 32 kips  0 kips  1.00(0.6)(50 ksi)(12.6 in.  2(1.5 in.)) = 0.111 in.  0.5 in. o.k.

tst min 

114 Stiffeners and Doublers

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Stiffener & Doubler Example – 8. Column Stiffener Weld • Stiffener Weld to Doubler Horizontal Edge and Column Web for unbalanced stiffener force Snip

Lwf

• Solution:

Lww

Lww  lst  2 snip  12.6 in. - (2)1.5 in. = 9.6 in.   0.928 ASD   1.392 LRFD

DOUBLER

Pst 1  Pst 2 (2)( Lww) 32 kips+ 0 kips  1.392(2)(9.6 in.) = 1.20 (16th of an inch)

COL. WEB

1/4

D min web 

STIFFENER

1/4

TYP

< 4 (16th of an inch), use 1/4” Fillet Weld o.k. 115

Stiffeners and Doublers

Stiffener & Doubler Example • Solution:

Lwf

– 8. Column Stiffener Thickness – Weld Design of Stiffener to Column – AISC Specification Section J2

Lww

Snip

Check plate and column web thicknesses for weld size

   0.75 

tst min 

(2)( D min) 1.392(2)(1.20)   0.114 in. (0.6) Fup 0.75(0.6)(65 ksi)

< tst = 0.5 in. o.k.

twc min 

(2)( D min) 1.392(2)(1.20)   0.114 in. (0.6) Fuc 0.75(0.6)(65 ksi)

< twc = 0.83 in. o.k.

116 Stiffeners and Doublers

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Stiffener & Doubler Example • Solution: 1/4 TYP 1/4

– 9. Summary  DOUBLER

DOUBLER MAY ENCROACH INTO COLUMN FILLET

COL. WEB

1/4 STIFFENER

1/4 SECTION A

TYP

SECTION B

a PL 3/4" DOUBLER B

B W27x94

1/2" STIFFENER PL NS/FS W27x94

A A W14x176 COLUMN

117

Stiffeners and Doublers

Conclusion • Doublers are required to resist shear forces exceeding the panel zone shear strength • AWS D1.8/D1.8M: 2016 has a prequalified doubler weld configuration • Sufficient information is needed to check for web doublers • Increasing the column size to eliminate stiffeners and doublers can be cost effective • Stiffeners (also known as continuity plates) are required to resist applied loads greater than the local strength of the supporting member • Stiffener applicable limit states are in Specification Section J10

Stiffeners and Doublers

118

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Questions?

119

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