Axial, Shear and Moment Interaction of WT Connections · PDF fileAxial, Shear and Moment Interaction of WT Connections and Shear Tab Connections Presented by: ... −Determination

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Axial, Shear and Moment Interaction ofWT Connections andShear Tab Connections

Presented by:Adam FriedmanScott Thompson

Overview

� Literature Review

� Experimental Program

− Test Specimen Overview

− Test Assembly Overview

− Test Procedure

� Experimental Results

− Determination of Forces

− Determination of Connection Forces

− Verification of Data Results

− Determination of Bolt Forces

2

Overview (continued)

� WT Connection

− 3 Bolt WT Test Results



− Conclusions

� Shear Tab Connection

− 3 Bolt ST Test Results



− Conclusions

Overview (continued)

� Comparisons

− Limit States

− Forces at Approx. Maximum Moment

− Forces at Initial Failure

− Forces at Secondary Failure

− Bolt Forces at Approx. Maximum Moment

− Interaction Diagrams

� Conclusions

� Future Research

� Questions/Comments

3

Literature Review

� “Simple Beam Connections in Combined

Shear and Tension” by Guravich and Dawe

� “Behavior of Bolted Beam-Column Connections under Catenary Action” by Girhammar

� “FEMA-355D State of the Art Report on Connection Performance”

� “Robustness of Composite Floor Systems with Shear Connections: Modeling, Simulation, and Evaluation” by Sadek, El-Tawil, and Lew

� “Guide to Design Criteria for Bolted and Riveted Joints” by Kulak, Fisher, and Struik

Test Specimen OverviewWT Connection

3 Bolt WT

4 Bolt WT

5 Bolt WT

4

Test Specimen OverviewWT Connection-Limit States

222.4 kips

Test Specimen OverviewShear Tab Connection

3 Bolt Shear Tab

4 Bolt Shear Tab

5 Bolt Shear Tab

5

Test Specimen OverviewST Connection-Limit States

Test Specimen OverviewST Connection-Limit States

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Test Assembly Overview

Test Assembly Overview

7

Test Assembly OverviewHydraulic Cylinder Frame

Test Assembly OverviewSpecimen Connection

8

Test Assembly OverviewDWT & DWT Support

Test Assembly OverviewStrain Gages

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Test Assembly OverviewStrain Gages

Left Beam Right Beam

Test Assembly OverviewPin Connection

10

Test Procedure

� Initial Verification / Setup Procedure

− Attached and Secured True pin connections, Hydraulic Cylinder Frame, and Test Beams.

− Test beams suspended via (2) ratchet slings “Come-a-longs”.

− Loads cells were verified within 100 pounds of force (0.1% accuracy) via secondary test frame.

− (2) DWT’s verified within 0.01 inches and attached to isolated cold-formed steel track.

− Strain Gauges placed and verified to have 120 ohms of resistance after 24 hours dry time.

− Attached load cells, strain gages, and DWT’s to data acquisition system.

Test Procedure (continued)

� Test Protocol – Assembly (WT)

− Bolted WT test Specimens to stub column flange to a minimum snug tight condition.

� Test Protocol - Assembly (All)

− Attached threaded rod assembly to stub column web to a minimum snug tight condition.

− Lifted and attached test specimens and stub column into place. Attached to test beams at a minimum snug tight condition.

− Attached “come-a-long” to stub column web.

− Adjusted and level test assembly.

− Extended and attached hydraulic cylinder. Attached with (2) threaded nuts at threaded rod assembly.

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Test Procedure (continued)� Test Protocol – Assembly (All) (Continued)

− Applied a plaster whitewash at exterior face of connection.

− Installed Lexan safety containment cage to exterior face of test assembly.

− Slacked “come-a-longs” to prevent binding during testing.

� Test Protocol – Data Collection (All)

− Initiated data collection software.

− Applied initial “shake out” load to enact bearing in connection.

− Applied load at pump operators discretion while monitoring real-time load vs. deflection curve.

− Continued loading until obvious failure or sudden loss of applied load.

− Pending failure mechanism, continued loading until secondary failure mechanism.

Test Procedure (continued)

Typical Failed State

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Experimental Results

� Nine tests per connection type

− (3) 3-Bolt Connections



� Special Notes:

− 3WT2 required reaming of bolt holes

− 4WT1 required reaming of bolt holes

− 5ST1 had issued with testing equipment

− SG1 did not function properly for all tests

− SG6 did not function properly for all tests

Determination of Forces

� Collected Output Data:

− Time (steps)

− Applied Load at each load cell (pounds)

− Deflection at each draw wire transducer (DWT) (inches)

− Stain at 8 locations (µε)

� Using Microsoft Excel, output data were manipulated to find:

− Average Deflection (inches)

− Average Applied Load (kips)

− Rotation (radians)

− Stress (ksi)

− Axial Force (kips)

− Moment (kip-feet)

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� Beam End Rotation

� Average Deflection

� Applied Load

� Stress at Strain Gage – Hooke’s Law

,


� Axial & Flexural Stress Interaction Equation

� Determine Moment Equation

� Determine Axial Force Equation

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Determination of Forcesat Connection

� Determine Moment at Connection:

Determination of Forcesat Connection

� Axial Components

− Horizontal Force (Tension)

− Vertical Force (Shear)

� Applied Shear (Vertical Force)

15

Verification of Data Results

Free Body Diagram

Verification of Data Results� Axial Force

� Transverse (Shear) Force

� Vertical Components of Forces

� Summation of Vertical Force

� Percent Difference

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Verification of Data ResultsWT Connection

Test Side

Actuator

Force (kips)

Measured

Moment, M

(kip-ft)

Measured

Axial, P

(kips)

Measured

Rotation, θ

(radians)

Transverse

Force, Rt

(kips)

Vertical

Component of

Rt (kips)

Axial Force,

Ra (kips)

Vertical

Component of

Ra (kips) ΣFy (kips)

Percent

Difference

(%)

Left 7.34 7.72 0.102 2.387 2.374 7.720 0.786

Right 7.01 7.54 0.102 2.279 2.267 7.540 0.768

Left 7.19 5.83 0.092 2.337 2.327 5.830 0.536

Right 7.05 6.17 0.092 2.294 2.284 6.170 0.567

Left 7.43 7.48 0.098 2.416 2.404 7.480 0.732

Right 6.85 7.67 0.098 2.226 2.215 7.670 0.750

Left 15.68 9.20 0.079 5.097 5.081 9.200 0.726

Right 13.91 9.99 0.079 4.521 4.507 9.990 0.788

Left 14.36 13.24 0.079 4.667 4.653 13.240 1.045

Right 12.98 13.50 0.079 4.220 4.207 13.500 1.065

Left 13.65 9.60 0.074 4.439 4.426 9.600 0.710

Right 13.06 10.62 0.074 4.247 4.236 10.620 0.785

Left 24.83 24.56 0.070 8.072 8.052 24.560 1.718

Right 22.07 25.25 0.069 7.177 7.160 25.250 1.741

Left 25.17 23.87 0.068 8.183 8.164 23.870 1.622

Right 22.71 24.16 0.068 7.384 7.367 24.160 1.642

Left 26.21 30.62 0.069 8.522 8.502 30.620 2.111

Right 23.05 31.55 0.068 7.495 7.478 31.550 2.144

-0.288 5.31%

-0.473 8.41%

-0.417 3.90%

-0.078 0.72%

0.043 0.42%

0.305 1.61%

0.353 1.85%

0.416 2.02%

5.425

5.628

10.686

10.892

10.200

18.975

19.148

20.651

3WT1

3WT2

3WT3

4WT1

4WT2

4WT3

5WT1

5WT2

5WT3

10.87%-0.6075.588

Verification of Data ResultsShear Tab Connection

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Determination of Bolt Forces

� Goal to better understand force distribution.

� Provide approximate bolt force analysis technique.

� Verify validity of collected data with comparison to bench mark bolt shear rupture value determine by Kulak et al.

� Provide forces which justified approximate connection failure rupture limit states.

� Benchmark Data for ¾” ASTM A325-X Bolt:

− Rn=(80.1ksi)*(.0442in2)=35.4kips


� Forces at bolt line included:

− Measured axial force

− Applied shear force

− Measured moment

− Inherent moment in connection

� Forces analyzed using an approximated average maximum measured moment.

− Range created each side of Mm, max

− Same range used for Vapp, Pm, and θm

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� All forces expressed in units of force with respect to the primary orthogonal axes.

� Paxial expressed as:

� Measured moment and applied shear forces were resolved using (2) Instantaneous Center of Rotation (ICOR) analyses as described per the AISC 13th Edition Specification.

� Initial elastic analysis provided unrealistic bolt forces.


� ICOR analysis accounts for maximum expected deformation of bolt and connecting material equal to a maximum of ∆max=0.34 inches.

� Coefficients λ, µ, ∆ very depending on grade and thickness of connected material.

Force vs. Deformation Curve

¾” A325 bolt in double shear

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� Vapplied analyzed with 3 ½” bolt offset

− Not addressed per AISC 13th Edition.

− Inherent 20% reduction in bolt shear capacities (BGAF) per AISC 13th Edition.

� Mm analyzed using a normalized shear force, Vnorm, equal to “1”

− Eccentricity taken as Mm in inches.

+


� Bolt forces for each ICOR analysis transformed to the orthogonal axes.

� Resultant bolt force taken as the square root of the sum of the squares.

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3WT Connection Testing

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Test Side

Moment, M

(kip-ft)

Shear, V

(kips)

Axial, P

(kips)

Rotation, θ

(radians) Notes

Left 16.83 2.79 7.72 0.102

Right 15.16 2.79 7.54 0.102

Left 16.52 2.71 5.83 0.092

Right 15.25 2.71 6.17 0.092

Left 16.01 2.81 7.48 0.098

Right 13.83 2.81 7.67 0.098

Test Values at Estimated Maximum Moment

3WT1

3WT2

3WT3

Test Side

Moment, M

(kip-ft)

Shear, V

(kips)

Axial, P

(kips)

Rotation, θ

(radians) Notes

Left 6.86 5.32 35.72 0.132 Bolt shear failure at bottom bolt

Right 3.52 5.32 36.59 0.133

Left 6.78 5.22 35.06 0.125

Right 5.25 5.22 36.13 0.125 Bolt shear failure at bottom bolt


Right 1.25 5.45 41.43 0.128

3WT1

3WT2

3WT3

Test Values at Initial Failure


Test Specimen Bolt Left Side Right Side

Top 33.07 29.98

Mid. 3.10 3.05

Bot. 37.98 34.77

Top 33.03 30.50

Mid. 2.53 2.62

Bot. 36.74 34.43

Top 31.59 26.92

Mid. 3.04 3.09

Bot. 36.36 31.81

Bolt Shear at Estimated Max. Moment (k)

3WT1

3WT2

3WT3

Max. Bolt Shear = 35.4 kips1

1Kulak, Geoffrey L., John W. Fisher and John H.A. Struik. 2001. Guide to Design Criteria for Bolted and Riveted

Joints Second Edition. United States: Research Council on Structural Connections.

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3WT1 Connection Testing


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Test Side

Moment, M

(kip-ft)

Shear, V

(kips)

Axial, P

(kips)

Rotation, θ

(radians) Notes

Left 31.67 5.34 9.20 0.079

Right 28.09 5.34 9.99 0.079

Left 29.00 5.45 13.24 0.079

Right 26.22 5.45 13.50 0.079

Left 27.58 5.10 9.60 0.074

Right 26.39 5.10 10.62 0.0744WT3


4WT1

4WT2

Test Side

Moment, M

(kip-ft)

Shear, V

(kips)

Axial, P

(kips)

Rotation, θ

(radians) Notes

Left 30.29 7.44 32.24 0.097


Left 28.21 7.10 28.87 0.093


Left 27.28 6.99 30.87 0.091



4WT1

4WT2

4WT3






Top 33.55 29.19

2 26.82 23.21

3 31.10 27.88

Bot. 37.94 33.97

Top 28.98 26.02

2 22.90 20.45

3 29.16 26.84

Bot. 35.36 32.53

Top 28.26 26.76

2 22.47 21.20

3 26.98 26.21

Bot. 32.87 31.87


4WT1

4WT2

4WT3

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Test Side

Moment, M

(kip-ft)

Shear, V

(kips)

Axial, P

(kips)

Rotation, θ

(radians) Notes

Left 6.16 4.45 32.22 0.105

Right 4.08 4.45 31.95 0.108 Bolt shear failure at 3rd Bolt

Test Values at Secondary Failure

4WT3


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Test Side

Moment, M

(kip-ft)

Shear, V

(kips)

Axial, P

(kips)

Rotation, θ

(radians) Notes

Left 50.15 9.49 24.56 0.070

Right 44.59 9.49 25.25 0.069

Left 50.84 9.57 23.87 0.068

Right 45.88 9.57 24.16 0.068

Left 52.95 10.33 30.62 0.069

Right 46.57 10.33 31.55 0.068

5WT1

5WT2

5WT3


Test Side

Moment, M

(kip-ft)

Shear, V

(kips)

Axial, P

(kips)

Rotation, θ

(radians) Notes


Right 45.02 9.97 29.40 0.073


Right 46.59 9.79 25.36 0.069


Right 47.13 10.63 33.40 0.069

5WT2

5WT3


5WT1






Top 31.99 28.16

2 28.37 24.88

3 5.62 5.74

4 37.79 34.57

Bot. 41.51 37.96

Top 32.60 29.25

2 28.93 25.88

3 5.50 5.55

4 38.09 35.15

Bot. 41.85 38.62

Top 32.86 28.43

2 29.03 24.99

3 6.82 6.99

4 40.83 37.15

Bot. 44.77 40.71


5WT1

5WT2

5WT3

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Test Side

Moment, M

(kip-ft)

Shear, V

(kips)

Axial, P

(kips)

Rotation, θ

(radians) Notes

Left 24.66 7.93 37.61 0.083 Bolt shear failure at 4th Bolt

Right 28.71 7.93 40.60 0.080

Test Values at Secondary Failure

5WT3

Test 3ST1 – Specimen 3STR1� Bolt Shear Rupture bottom bolt.

� Misalignment of middle bolt.

� No white wash available at time of 3 bolt testing.

� Large scale bearing deformation in shear plate.

� Beam end rotation near 0.14 radians.

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Test 3ST2 – Specimen 3STR2

� Tension rupture originating at bottom bolt hole.

� Elongation of bottom hole specimen 3STL2.

� Shear area reduction evident in bolt specimens.


� Similar tension rupture failure as 3STR2.

� Large scale variability in collected data of 3STL3.

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� Third Failure Mechanism:

− Localized block shear failure of bottom bolt.

� White wash provided detailed view of stress distribution at shear plate.

� Secondary bolt shear failure of 3rd bolt.


� System was capable of supporting an increase applied load post initial failure mechanism.

� Transition from flexure to catenary tension response.

� Increase in flexural demand at 0.03 radians.

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� Bolt shear rupture of bottom bolt.

� White wash depicts stress distribution.

− Force couple between top and bottom bolts.

− Stress concentration at bottom plate edge.


� Comparison of specimen 4STR1 and 4STR2.

� Increased catenary tension at max moment.

� Max beam end rotation 0.095 radians at failure.

4STR1

LOCALIZED BLOCK SHEAR FAILURE

BOLT SHEAR SECONDARY FAILURE

INCREASE APPLIED LOAD POST FAILURE

4STR2

BOTTOM BOLT SHEAR RUPTURE

SIGN OF INITIAL INCREASE IN APPLIED LOAD POST FALIURE

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Test 4ST3 – Specimen 4STL3

� Tension rupture failure of bottom bolt hole.

� 1 of the 2 left side failed specimens.

� Typical “curl” at bottom plate edge.

� Tears around bolt hole circumference.

� Connection unzipping as load applied post failure.

Test 5ST1 – Specimen 5STR1� Initial failure: Localized block shear of bottom hole.

� Secondary bolt shear failure of 4th bolt.

� Reversal of hydraulic inputs – Collected data skewed.

� White wash revealed stress distribution at bolt holes.

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Test 5ST2 – Specimen 5STR2� Initial failure: Localized block shear of bottom hole.

� Secondary bolt shear failure of 4th bolt.

� Post failure applied load recovery not increase.

� Sustained maximum moment range.

� Beam end rotation 0.085 radians at failure.

Test 5ST3 – Specimen 5STL3� Initial failure: Tension rupture of bottom hole.

� Secondary bolt shear failure of 4th bolt occurred prior to plate unzipping.

� Post failure applied load increase.

� Beam end rotation 0.075 radians at failure.

5STR2 5STL3

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Approximate Shear Tab Failure States

� Goal to determine limit states based on observed failure modes and calculated bolt forces

� Utilize unfactored AISC 13th Edition limit states including:

− Tension rupture using Whitmore length.

− Bolt shear rupture

− Block Shear rupture

Shear Tab Testing Summary� (3) controlling failure states

− Bolt shear

− Shear plate Tension Rupture

− Local block shear rupture of bottom hole

� Flexural demand increased linearly at approximately 0.03 radians

� Three bolt connection show clear transition from flexure to catenary force transfer response.

� The rate of increase in catenary tensile forces increased as the flexural demand peaked.

� Average Beam end rotation at initial failure:

− 3 Bolt 0.133 Radians



� Evidence of Four and Five bolt connections capable of recovering or increasing applied load after failure.

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Comparisons

� Limit States

− Fy=36ksi vs. Fy=50ksi

− Fu=58ksi vs. Fu=65ksi

� Connection Forces at Approx. Maximum Moment

� Connection Forces at Initial Failure

� Connection Forces at Secondary Failure

� Bolt Forces at Approx. Maximum Moment

� Preliminary Interaction Diagrams

Connection Forces at Approximated Maximum Moment

WT Data Shear Tab Data

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Connection Forces at Initial Failure

WT DataShear Tab Data

Connection Forces atSecondary Failure

WT Data

Shear Tab Data

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Bolt Forces at Approximated Maximum Moment.

WT DataShear Tab Data

Preliminary Interaction Diagrams

� Linear interaction provides base line comparison.

� Provides a visual representation of force distribution at Maximum Measured moment.

� Rv equal to resultant of Vapp and Pm.

� Rv,max equal to bolt group shear capacity.

� Mm,max found using ICOR method.

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Preliminary Interaction Diagrams – WT

Preliminary Interaction Diagrams – Shear Tab

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Conclusions

� Data Reporting

− Provides valuable data for future research into robustness in steel design

� Flexural Resistance

− Testing showed that simple shear WT and shear tab connections have some amount of flexural resistance

� Catenary Action

− Testing showed that a two-span system exhibited catenary action after failure of a center support

Conclusions (continued)

� Limit State Evaluation

− Bolt shear failure reached expected levels based on reports in the Guide

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Future Research

� Variation of connection size, holes, bolts, and geometry

� Consider beam or column to serve as weak link (particularly for web limit states at the connection)

� Include a floor system (i.e. metal deck, concrete slab, etc.) to study the effects of composite action

� Test using a 2 x 2 bay incorporating connections at both the column flanges and column web

� Testing of alternative types of shear connections

� Finite element modeling and analysis of test assembly for analytical validation

Future Research (Continued)

� Refined bolt force analysis technique.

� Refined limit states for the combination of shear, tension, and flexural forces.

� Increase number of strain gages at supported beam.

� Determine specific ICOR coefficient values for material combinations tested.

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Questions/Comments

� Special Thanks to:

− Dr. Richard DeVries, MSOE

− Dr. H. Peter Huttelmaier, MSOE

− Prof. Chris Raebel, MSOE

− Dr. Doug Stahl, MSOE

− Dr. Chris Foley, Marquette University

− Germantown Iron & Steel

− Computerized Structural Design, S.C.

− US Steel Corporation

− American Institute of Steel Construction Foundation

Documents

Axial, Shear and Moment Interaction of WT Connections · PDF fileAxial, Shear and Moment Interaction of WT Connections and Shear Tab Connections Presented by: ... −Determination