STRENGTH AND DUCTILITY OF WELDED JOINTS - AISC

418 Pages·2008·9.58 MB·English

STRENGTH AND DUCTILITY OF WELDED JOINTS 
SUBJECTED TO OUT‐OF‐PLANE BENDING 

by 

Ivan Gomez  Yu Kay Kwan 
Amit Kanvinde  Gilbert Grondin 

University of California, Davis University of Alberta

Final Report Presented to 

American Institute of Steel Construction 

July 2008
Executive Summary
The current AISC design specification for welded connections does not make a
distinction between joints subjected to eccentric loads in the plane of the weld group, and
those subjected to eccentric loads not in the plane of the weld group. The effect of
loading perpendicular to the root notch and moment transfer by bearing of the connected
plates in the compression zone of the welded joint are both factors that may affect
significantly the load carrying capacity of these joints. To investigate the root notch effect
and the load transfer mechanism, an experimental program was conducted consisting of
24 welded cruciform test specimens tested in direct tension and 60 cruciform weld
specimens tested under combined shear and bending.
Results from twenty-four cruciform tests indicate that the strength of fillet welds is not
affected significantly by the presence of the root notch. The E70T7-K2 welds show
approximately twice the ductility of the E70T7 welds, whereas the E70T7 welds show a
slightly reduced ductility as compared to previous published data for lap-welded joints.
However, the ductility for all the welds is relatively insensitive to root notch length.
Complementary fracture mechanics based finite element simulations are conducted to
examine and generalize experimental findings. The simulations indicate that larger notch
lengths do not further reduce the strength and ductility of the welds.
Earlier test results and the test results from this test program reveal that the current (13th
Edition) AISC design tables for eccentrically loaded welds are highly conservative (i.e.
test-to-predicted ratios are, on average, 1.75; with a coefficient of variation = 0.25) for
joints with out-of-plane eccentricity. This conservatism is attributed to the disregard of
plate bearing stresses that significantly alter the stress distribution in the joint. An
alternate approach that explicitly incorporates this bearing effect is proposed, and the
resulting strength predictions are determined to be significantly less conservative when
compared to the current design standards. Limitations of the research and future work are
outlined.
A total of 14 strength prediction models were evaluated. The model consisting of a
modified version of the instantaneous center of rotation approach developed by Dawe and
Kulak (1972) was found to provide the target safety index with a resistance factor of
0.75. A simple closed form model was developed and is proposed as a substitute for the
more complex instantaneous center of rotation model. The proposed closed form model
provides a safety index of 4.0 with a resistance factor of 0.75.

ii
Acknowledgments
This project was conducted as a joint collaboration between the University of California
Davis and the University of Alberta. The project was funded by the American Institute of
Steel Construction (AISC) and the Natural Sciences and Engineering Research Council
of Canada (NSERC). The authors gratefully acknowledge Mr. Tom Schlafly of AISC and
Dr. Duane Miller of Lincoln Electric who provided valuable advice and reviewed the
welding and shop procedures. Marshall Roberts, graduate student at UC Davis, assisted
with the experimental setup, and Jorge Camacho, undergraduate researcher at UC Davis,
assisted with the specimen measurements; the authors are thankful for their efforts. The
assistance of Mr. David DeBlasio of Gayle Manufacturing Company in preparing the
specimens is greatly appreciated. The authors also acknowledge Bill Sluis, laboratory
technician at UC Davis for assistance with design of the test setup.
iii
Table of Content
1. Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.1 General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.3 Objectives and Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Literature Review. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.2 Behavior of Fillet Welds Under Load . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3 Experimental Programs on Joints Loaded with Out-of-Plane
Eccentricity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.4 Theoretical Studies on Eccentrically Loaded Welded Joints . . . . . . . . 8
2.5 Cruciform Joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
2.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
3. Cruciform Tension Experiments, Finite Element Simulations and
Ancillary Tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.2 Filler Metal Classifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
3.3 Base Metal Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.4 Ancillary Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.5 Cruciform Specimen Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.6 Cruciform Test Setup and Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . 15
3.7 Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3.8 Results of Cruciform Tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.9 Discussion of Cruciform Results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
3.10 Finite Element Simulations to Generalize Test Results . . . . . . . . . . . . 20
3.11 Fractographic Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3.12 Summary of Observations from Cruciform Tests . . . . . . . . . . . . . . . . 24
4. Cruciform Bend Experiments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . 44
4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
4.2 Bend Specimen Preparation, Test Setup, Test Procedure and
Description of Recorded Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
iv
4.3 Measurements of the Cruciform Specimens . . . . . . . . . . . . . . . . . . . 47
4.4 Experimental Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
4.5 Summary of Observations from Cruciform Bend Tests . . . . . . . . . . . 53
5. Collection of Test Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
5.2 Ancillary Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
5.3 Tests on Welded Joints with Out-of-Plane Eccentricity . . . . . . . . . . . 69
5.4 Comparisons Between the Test Programs . . . . . . . . . . . . . . . . . . . . . 71
5.5 Comparison of Material Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
5.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
6. Analysis and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
6.2 Description of Existing Analytical Models . . . . . . . . . . . . . . . . . . . . . 98
6.3 Evaluation of the Existing Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
6.4 Segregation of Test Specimens in Accordance to Toughness
Requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
6.5 Reliability Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
6.6 Level of Safety Provided by Existing Models. . . . . . . . . . . . . . . . . . . . . 115
6.7 Proposed New Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
6.8 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
7. Summary and Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
7.1 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
7.2 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
Appendix A – Welding Procedures and Specifications . . . . . . . . . . . . . . . . . . . . . A-1
Appendix B – Cruciform Specimen Measurements . . . . . . . . . . . . . . . . . . . . . . . . B-1
Appendix C – Ancillary Test Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . C-1
Appendix D – Tension Test Load-Deformation Curves . . . . . . . . . . . . . . . . . . . . . D-1
Appendix E – Bend Test Experimental Response Results. . . . . . . . . . . . . . . . . . . . . E-1
Appendix F – Instantaneous Center of Rotation Approach . . . . . . . . . . . . . . . . . . . F-1
v
Appendix G – Predicted Welded Joint Capacity for All Existing Models . . . . . . . . G-1
Appendix H – Simplified Strength Prediction Model . . . . . . . . . . . . . . . . . . . . . . . . H-1
Appendix I – Proposed Design Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I-1

vi
List of Tables
3.1 Basic material properties from standard tension coupons . . . . . . . . . . . . . . . 26
3.2 Results from Charpy V-Notch tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
3.3 Chemical composition of the filler metals (% by weight) . . . . . . . . . . . . . . . 27
3.4 Loading rates for cruciform tension tests . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3.5 Test matrix and summary of experimental data from cruciform tension
tests. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28
3.6 Summary of experimental data from cruciform tests using throat area
based on post-fracture measurements. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3.7 Summary of data from other tension test programs on cruciform
specimens. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

3.8 Calibrated J values for different weld sizes and classifications . . . . . . . . . . 30
IC
4.1 Test matrix and summary of experimental data from bend tests . . . . . . . . . . . 55
4.2 Bend Test Loading Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
4.3 Design Table from the current (13th) edition (2005) of the AISC Steel
Construction Manual . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
5.1 Material Factor Specific for E60 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
5.2 Material Factor Specific for E70 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
5.3 Charpy V- Notch Impact Test Results (UC Davis) . . . . . . . . . . . . . . . . . . . . . 77
5.4 Weld Metal Tension Coupon Test Results (UC Davis) . . . . . . . . . . . . . . . . . 78
5.5 Specimen Data from Dawe and Kulak (1972) . . . . . . . . . . . . . . . . . . . . . . . . . 78
5.6 Specimen Data from Picard and Beaulieu (1985) . . . . . . . . . . . . . . . . . . . . . . 79
5.7 Summary of test results from Chapter 4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
5.8 Specimen Eccentricity Ratio used by Dawe and Kulak, Picard and
Beaulieu and UC Davis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
5.9 Predicted welded joint capacity on test results from University of
Alberta (Dawe and Kulak, 1972) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
vii
5.10 Predicted welded joint capacity on test results from Université Laval
(Beaulieu and Picard, 1985) using F = 80.1 ksi . . . . . . . . . . . . . . . . . . . . 85
EXX
5.11 Predicted welded joint capacity on test results from Université Laval
(Beaulieu and Picard, 1985) using F = 67.2 ksi . . . . . . . . . . . . . . . . . . . . 86
EXX
5.12 Predicted welded joint capacity on test results from University of
California, Davis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
5.13 Charpy V-notch Impact Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
5.14 Weld Metal Tension Coupon Test Results . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
5.15 Comparison of Cruciform Test Results with Prediction by Current
Design Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
6.1 Summary of Professional Factor, ρ , for Existing Models . . . . . . . . . . . . . . . 120
P
6.2 Summary of Professional Factor, ρ , for Specimens with Filler Metals
P
with No Toughness Requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
6.3 Summary of Professional Factor, ρ , for Specimens with Filler Metal
P
with Toughness Requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122
6.4 Summary of Geometric Factor ρ from Various Sources (Li et al.,
G
2007) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
6.5 Geometric Factor ρ for Tensile Specimens from UC Davis
G
(Leg size = 0.5 in) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
6.6 Geometric Factor ρ for Tensile Specimens from UC Davis
G
(Leg size = 0.313 in) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
6.7 Geometric Factor ρ for Bending Specimens from UC Davis
G
(Leg size = 0.5 in) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
6.8 Geometry Factor ρ for Bending Specimens from UC Davis
G
(Leg size = 0.313 in) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
6.9 Geometric Factor ρ for Specimens from Beaulieu and Picard
G
(Leg size = 0.236 in) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
6.10 Geometric Factor ρ for Specimens from Beaulieu and Picard
G
(Leg size = 0.473 in) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
6.11 Geometric Factor ρ for Specimens from Beaulieu and Picard
G
(Leg size = 0.315 in) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
viii
6.12 Geometric Factor ρ for Specimens from Beaulieu and Picard
G
(Leg size = 0.394 in) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
6.13 Summary of Material Factor ρ for tensile strength of the weld . . . . . . . . . . 133
M1
6.14 Summary of Material Factor ρ for static yield strength of the plate . . . . . . 134
M1
6.15 Summary of Material Factor ρ for ultimate tensile strength of the
M1
plate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
6.16 Summary of Material Factor ρ (Li et al., 2007) . . . . . . . . . . . . . . . . . . . . . 135
M2
6.17 Reliability Analysis for Models 4, 5 and 8 and Filler Metal with No
Toughness Requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
6.18 Summary of Safety Indices for Models 4, 5 and 8 on the Specimens
with Toughness Requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
6.19 Summary of Professional Factor, ρ , for Model 9 . . . . . . . . . . . . . . . . . . . . . . 138
P
6.20 Safety Index for Model 9 and Filler Metal with No Toughness
Requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
6.21 Safety Index for Model 9 and Filler Metal with Toughness
Requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

ix
List of Figures
1.1 Eccentrically loaded welded joints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1 Load verse deformation curves for fillet welds (Modified from Butler
and Kulak 1969 and Lesik and Kennedy 1990). . . . . . . . . . . . . . . . . . . . . . . . . 12
2.2 Normalized load verse deformation curves for fillet welds (Modified
from Butler and Kulak 1969 and Lesik and Kennedy 1990) . . . . . . . . . . . . . 12

3.1 Detail of standard tension all-weld and base metal test coupons . . . . . . . . . . . 31

3.2 Detail of plate assembly (in accordance with ANSI/AWS5.20)
indicating the extraction of all-weld tension coupons and Charpy V-
Notch specimens . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

3.3 Geometry of Charpy V-Notch impact test specimen. . . . . . . . . . . . . . . . . . . . . 32

3.4 Cruciform specimen assembly showing key dimensions and
fabrication detail . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3.5 Mean weld profiles for (a) all the 1⁄ inch welds including the different
2
filler metals and plate thicknesses (b) all the 5⁄ inch welds including
16
the different filler metals and plate thicknesses . . . . . . . . . . . . . . . . . . . . . . . . 33
3.6 Representative photograph showing specimen setup and
instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
3.7 Schematic of potentiometer mounting cart for measuring weld
deformation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
3.8 Plot showing typical tension test experimental response . . . . . . . . . . . . . . . . . 35
3.9 Photograph of fillet weld gage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
3.10 Pre-fracture weld measurement locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.11 Photograph of fractured surface showing initiation straight ahead of
root notch followed by shear fracture (Test #16) . . . . . . . . . . . . . . . . . . . . . . . 37

3.12 Post-Fracture measurement diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.13 Protractor used for measuring fracture angle . . . . . . . . . . . . . . . . . . . . . . . . . . 38

3.14 Comparison of measured capacity from tests with capacity predicted
using the AISC (2005) design equation (φ = 1.0) . . . . . . . . . . . . . . . . . . . . . . 39
x