Jo(' A - AISC Home...W14x176 column and W2lxl66 beam (A992 steel) were tested with the SAC loading...

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AISC E&R Lbrary

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Report No.

SSRP- 2oo1/05

May 2001

....

. .

STRUCTURAL SYSTEMS

RESEARCH PROJECT

EFFECT OF STRAIGHTENING METHOD

ON THE CYCLIC BEHAVIOR OF k AREA

IN STEEL ROLLED SHAPES

by

Chia-Ming Uang

Brandon Chi

Final Report on a Research Project Funded by the American lnstitute of Steel Construction

Department of Structural Engineering

University of California, San Diego

La JolJa, California 92093-0085

I' I I I I I I I I I I I I I I I I I

University of Cali fomi a, San Diego


Structural Systems Research Project

Report No. SSRP - 200 1105

Effect of Straightening Method on the Cyclic

Behavior of k Area in Steel Rolled Shapes

by

Chia-Ming Uang Professor of Structural Engineering

Brandon Chi Graduate Swdenl Researcher

Final Report on a Research Project Funded by the American Institute of Steel Construction


University of California, San Diego

La Jolla, California 92093-0085

May 2001

l :z ,f) LA>

I I I I I I I I

II

I I I I I I I I I

ABSTRACT

The research objective was to evaluate the effect of rotary-straightening on the cyclic

behavior of k area in column sections. A lOtal of five full-scale steel moment connections with

W14x176 column and W2lxl66 beam (A992 steel) were tested with the SAC loading protocol.

The first three specimens did not use continuity plates and doubler plate; the only variable was

the method of straightening of the columns (rotary-straightened, gag-straightened. and non

straightened). To promote the potential for fracture. a I-inch diameter hole was drilled in the k

area at the bottom flange level of the beam. Continuity plates and a doubler plate were used for

the last two specimens-one with a rotary-straightened column and another one with a non

straightened column. No attempt was made to avoid welding of the doubler plate and continuity

plates in or near the k area

The fU"St three specimens all failed by fracturing of the column flange outside the panel zone

at large drift levels. The fracture initiation was caused by the stress concentration in the middle

of the beam flange width because no continuity plates were used. Fracture initiated from the hole

in the gag-straightened and non-straightened columns. but not the rotary-straightened column.

Thus. no clear pattem indicating that rotary-straightening promoted fracture was observed.

Brittle fracture occurred in the beam at 6% drift for the last two specimens. The fracture initiated

in the weld access hole. which started in the k area of the beam due to stress concentration. To

avoid this type of failure. providing a smooth profile for the weld access hole is important.

Although this testing program did not reveal adverse effect created by rotary straightening.

material testing conducted by Lehigh researchers clearly showed that the ductility and toughness

of the material in the k area were significantly reduced. Therefore. it is prudent that designers

follow the AlSC Advisory to avoid welding in the k area.

I I I I I I I I I I I I I I I I I I I

ACKNOWLEDGEMENT

Funding for this research was provided by the American Institute of Steel Construction. Dr.

S. Zoruba and Mr. T. Schlafly served as the coordinating manager for this project. The authors

would like to thank Mr. R. Ferch, Vice President of Herrick Corporation, for the generous

donation of fabrication service for the moment connection test specimens. Drs. 1. Fisher and E.

Kaufmann at Lehigh University provided material test data contained in Chapter 2.

ii

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I I I I I I I I I I I I I I I I I I

TABLE OF CONTENTS

ABSTRAcr ..................................................................................................................................... i

ACKNOWLEDGEMENT ....................... .... ......................................................... .. ... ..... ........... ..... ii

TABLE OF CONTENTS ................................................................. ......... .................................. ... ii i

UST OF TABLES ......................................... .................................... .......................................... v

LIST OF FIGURES ..... ............................................................................... ...... ...... .................. ...... vi

I. INTRODUcrION ......................................................................................... .......................... 1

1.1 Statement of Problem .................................................................................................. 1

1.2 Objective of Research ............................................ ..................................................... 2

1.3 Scope ............................................. ......... .. ............................................ ....................... 2

2. TESTING PROGRAM .... .. ........................ ... ...... .. ................................ ..... ... .......................... 4

2. 1 Test Specimens ............................................ ... ....... ...................... ... .......................... ... 4

2.2 Material Characteristics .......................................................... ..... .. ........... ..... .............. 5

2.3 Specimen Design .. ....................................................................................................... 5

2.4 Test Setup ....................................... .. ................ .... ............. ....... ... .... .. ... ... .. ............. ..... 7

2.5 Test Procedure ................... ........................................................................................ .. 8

2.6 Instrumentation .............. .. .. .. ..... ...... .......... .......... .... ............... ...................................... 8

2.7 Data Reduction ................................................................ .... .. .... .................................. 8

3. TEST RESULTS OF SPECIMENS WITHOUT CONTINUITY PLATES AND DOUBLER

PLATE ...... ........................................................................................ ............ .......... ...................... 20

3.1 General ................................ ......... ............................... .. ..... .. ... ......................... ........ . 20

3.2 Specimen Kl (Rotary-Straightened Column) ........................................................... 20

3.3 Specimen K2 (Gag-Straightened Column) ............................................................... 32

3.4 Specimen K3 (Non-straightened Column) ...... ............... .. ...... .. ................................. 43

4. TEST RESULTS OF SPECIMENS WITH CONTINUITY PLATES AND DOUBLER

PLATE ......... ... ......................... ...................... .... .. ................................................................... .... .. 53

4.1 General .................... .. .................... ...... ................. ............... ............ .................... ..... . 53

4.2 Specimen K4 (Rotary-Straightened Column) ........................................................... 53

4.3 Specimen K5 (Non-Straightened Column) ............................................................... 61

iii

I ~ I" I I I I I I I I I I I I I I I I I

5. IMPLICATIONS OF TEST RESULTS ... ........... .... ............................ .... ........................... ... 70

5.1 Test Specimens without Continuity Plates ................................................................ 70

5.2 Test Specimens with Continuity Plates and Doubler Plate .... .................. ..... ............ 71

6. SUMMARY AND CO CLUSIONS .................................................................................... 73

REFERENCES ........................ ............................................................... ....................................... 75

iv

I ,


o

LIST OF TABLES

Table 2. 1 Test Matrix ................ ............................. .............. .... ................................ ....................... 9

Table 2.2 Chemical Compositions ...................................... ............................................................ 9

Table 2.3 Beam and Column Mechanical Properties ..... ...... .. .. ... ... ........... .... ... .... .. ......... .... ....... ... JO

Table 2.4 Column Mechanical Properties (Kaufmann et aI . 2001) .... .... ........... .... ...... .... .............. JO

v

1,0 ,0

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I I I I I I I I I I I I I I I I I

LIST OF FIGURES

Figure 1.1 k Area in a Wide-flange Section ... ... .... .......................................................................... 3

Figure 1.2 Rotary-straightening of Rolled Shape .................... ........ .... .. .......................................... 3

Figure 2.1 Tensile Coupon Layout (Kaufmann et al . 2001) .. .................... .. .. .... ........................... 11

Figure 2.2 k-Area Stress-Strain Behavior for the Three Differently Processed Sections

(Kaufmann et al. 2001) .......................................................................................................... I 1

Figure 2.3 k-Area Hardness and CVN for the Three Differently Processed Sections (Kaufmann et

al . 2001) .................................................. ... ... ........................................... ......................... ..... 12

Figure 2.4 Overall Dimensions of Test Assembly ............................. .. ......................................... 13

Figure 2.5 Specimens KI to K3: Moment Connection Details ........ .. .................................. ......... 14

Figure 2.6 Specimens K4 and K5: Moment Connection Details .................................................. 15

Figure 2.7 SAC Standard Loading History ................................................................................... 16

Figure 2.8 Specimens Kl to K3: Layout of Displacement Transducers ....................................... 16

Figure 2.9 Specimens KI to K3: Strain Gage and Rosette Locations ................ .. .... ................ .. ... 17

Figure 2.10 Specimens K4 and K5: Layout of Displacement Transducers .................................. 18

Figure 2.11 Specimens K4 and K5: Strain Gage and Rosette Locations .... .................................. 19

Figure 3.1 Specimen Kl: Panel Zone Yielding and Crack Initiation at Toe of Bottom Flange

Groove Weld (3% Drift) ....................................................................................................... 22

Figure 3.2 Specimen Kl: Fracture of Column Flange at Bottom Flange Level and Propagation

near k Area (4% Drift) .................................................... .............. .... .. .................................. 23

Figure 3.3 Specimen Kl : Deformed Configuration at to in. Beam Deflection ............................ 24

Figure 3.4 Specimen Kl : Crack at Toe of Top Flange Groove Weld (10 in. Beam Deflection) .. 24

Figure 3.5 Specimen Kl : Load versus Beam Tip Displacement Relationship ............................. 25

Figure 3.6 Specimen Kl : Moment versus Total Plastic Rotation Relationship ............................ 25

Figure 3.7 Specimen Kl : Strain Gradient through Thickness of Beam Top Flange ..................... 26

Figure 3.8 Specimen Kl : Beam Bottom Flange Strain Profiles .................................................... 27

Figure 3.9 Specimen Kl : Response of Column Flange Out-of-plane Deformation and Transverse

Strain ..................................................................................................................................... 28

Figure 3.10 Specimen KI: Strain Profiles along Column k Line at Beam Top Flange Level.. .... 29

vi

1'1) I I I I I I I I I I I I I I I I I I

,,:;. to

Figure 3.11 Specimen Kl: Strains in the Column k Area at Beam Top Flange Level (Rl) ......... 30

Figure 3.12 Specimen Kl: Strains around Hole in the Column k Area Region (R4) ................... 31

Figure 3. I 3 Specimen K2: Yielding Panern (1 % Drift) ..... ................. ......................... ................. 33

Figure 3.14 Specimen K2: Fracture of Column Flange (4% Drift) ..... ........ ................. ........... .... 34

Figure 3.15 Specimen K2: Fracture of Column at Beam Top Flange Level (5% Drift) ........... .... 35

Figure 3.16 Specimen K2: Fracture Propagation in Hole Region ....... ............. .. .... .. ..................... 36

Figure 3.17 Specimen K2: Load versus Beam Tip Deflection Relationship ................................ 37

Figure 3.18 Specimen K2: Moment versus Total Plastic Rotation Relationship .......................... 37

Figure 3.19 Specimen K2: Beam Bottom Flange Strain Profiles ................................................. 38

Figure 3.20 Specimen K2: Response of Column Flange Out-of-plane Deformation and

Transverse Strain ................................................................................................................... 39

Figure 3.21 Specimen K2: Strain Profiles along Column k Line at Beam Top Flange Level ... .. .40

Figure 3.22 Specimen K2: Strains in the Column k Area at Beam Top Flange Level (R I) ........ 41

Figure 3.23 Specimen K2: Strains around Hole in the Column k Area (R4) ............................... .42

Figure 3.24 Specimen K3: Panel Zone Yielding Pattern at I % Drift ........................................... 44

Figure 3.25 Specimen K3 : Panel Zone Yielding Pattern at 3% Drift ................ ..................... .. .... 44

Figure 3.26 Specimen K3: Column Flange Fracture at Beam Bottom Flange Level (5% Drift, l SI

Cycle) ....................... ................................ ........... ......................... ................... .. .................... 45

Figure 3.27 Specimen K3: Column Flange Fracture at Beam Bottom Flange Level (5% Drift, 2nd

Cycle at 3.14 in) ................. ..................................................................... .............................. 45

Figure 3.28 Specimen K3: Fracture Propagation in Hole Region ................................................ .46

Figure 3.29 Specimen K3: Load versus Beam Tip Deflection Relationship .... ........................... .47

Figure 3.30 Specimen K3: Moment versus Total Plastic Rotation Relationship .......... ............... .47

Figure 3.31 Specimen K3: Beam Bottom Flange Strain Profiles .......... .. ........................ ... .... ... .. .48

Figure 3.32 Specimen K3: Response of Column Flange Out-of-plane Deformation and

Transverse Strain ................................................................................................................... 49

Figure 3.33 Specimen K3: Strain Profiles along Column k Line at Beam Top Flange Level ...... 50

Figure 3.34Specimen K3 : Strains in the Column k Area at Beam Top Flange Level (RI) .... .. .... 51

Figure 3.35 Specimen K3: Strains around Hole in the Column k Area (R4) ................. ............... 52

Figure 4.1 Specimen K4: Yielding of Panel Zone at 3% Drift .......................................... ........... 54

Figure 4.2 Specimen K4: Column Kinking due to Significant Panel Zone Yielding at 6% Drift 55

VII

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IX>

Figure 4.3 Specimen K4: Brittle Fracture of Beam Top Flange at 6% Drift ................................ 56

Figure 4.4 Specimen K4: Load versus Beam Tip Deflection Relationship .................................. 57

Figure 4.5 Specimen K4: Moment versus Total Plastic Rotation Relationship .. .......................... 57

Figure 4.6 Specimen K4: Panel Zone Responses .......................................................................... 58

Figure 4.7 Specimen K4: Beam Bottom Flange Strain Profiles .................................................... S9

Figure 4.8 Specimen K4: Strain Gradient through Thickness of Beam Top Flange .. ...... ............. 60

Figure 4.9 Specimen K5: Yielding Pattern in the Panel Zone at 3% Drift ................................... 62

Figure 4.1 OSpecimen K5: Yielding in Panel Zone and Beam Flange at 3% Drift.. ...................... 63

Figure 4.11 Specimen K5: Panel Zone Yielding at 5% DrifL ...................................................... 63

Figure 4.12 Specimen K5: Crack Initiation in Top Flange Weld Access Hole at 5% Drift ......... 64

Figure 4.13 Specimen K5: Curvature of Beam Bottom Flange near Weld Access Hole at 5%

Drift ...... .............................. ....... .. ................... ........ ........................................... .......... .......... 64

Figure 4.14 Specimen K5: Brittle Fracture of Beam Bottom Flange during the 6% Drift Cycle .6S

Figure 4.1S Specimen K5: Load versus Beam Tip Deflection Relationship ................................ 66

Figure 4.16 Specimen KS: Moment versus Total Plastic Rotation Relationship .......................... 66

Figure 4.17 Specimen KS: Comparison of Panel Zone Responses ............................................... 67

Figure 4.18 Specimen KS: Beam Bottom Flange Strain Profiles ................................................. 68

Figure 4.19 Specimen K5: Strains near Beam Bottom Flange Weld Access Hole ....................... 69

Figure S.1 Comparison of Strength for Local Web yielding ........................................................ 72

viii

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.-1. INTRODUCTION

1.1 Statement of Problem

Incidents of brittle fracture that initiated from the k area of wide flange sections have

been reported recently (Tide 2000). One example in seismic applications is the cracking

in the column web when the continuity plates (column transverse stiffeners) are welded

to the connection region in shop fabrication . The k area is the region extending from

about the midpoint of the radius of the fillet into the web approximately 1 to 1.5 inches

beyond the point of tangency between the fillet and web (see Figure 1.1).

The majority of rolled steel shapes have been produced in the past two decades from

scarp steel in an electric furnace and cast continuously into near shape configuration.

Except for heavy sections, these structural shapes are typically straightened by the rotary

straightening process in order to bring them into the dimensional tolerance specified in

the ASTM standard. The process involves passing a structural shape through a series of

rollers placed near the k areas (see Figure 1.2). Cold bending in these areas during the

straightening process generally produces cyclic plastic deformations. Strain hardening

together with strain aging results in higher tensile strength, lower ductility and toughness

(Tide 2000. Jaquess and Frank 1999). If welding is performed in or near the Ie area,

thermal strains are likely to serve as a trigger to promote brittle fracture.

In response to the concerns raised by the designers and fabricators, AISC issued an

advisory (lwankiw 1997), suggesting some interim measures to mitigate the k area

problem. In the meantime, AISC also initiated a series of research projects to study the

issue. The AlSC research includes four studies. The first study, conduced at Lehigh

University, deals with the characterization of cyclic inelastic strain behavior on properties

of rolled sections (Kaufmann et aI . 2(01). The second study, load tests on the Ie area of

rotary-straightened column sections to determine the effects on performance, was

conducted at both Lehigh University (Kaufmann et aI. 2(01) and the University of

California, San Diego (UCSD); the UCSD part deals with seismic moment frame

applications. To minimize the effect of welding in the panel zone region, a reassessment

of the design criteria and new alternatives for continuity plates and web double plate is

1

I· . I I I I I I I I I I I I I I I I I I

conducted as the third tudy at the University of Minnesota (Dexter ct a!. 200 1). The

fourth study, also conduced at the University of Minnesota, deals with the updating of

standard shape material properties database for design and reliability (Dexter et al. 2001).

1.2 Objective of Research

This research was parallel to the pull-plate monotonic tests at thc Lehigh University.

The objective of the re earch at UCSD was to investigate experimentally the effect of

member traightening methods on the rolled steel column performance in seismic

moment-resisting frames.

1.3 cope

To evaluate the effect of rotary straightening on the cyclic performance of rolled

wide-flange shapes, members that were either not straightened or straightened by gag

were also included in the experimental program. A total of five fu ll-scale moment

connection specimens were tested with the SAC loading protocol. Tensile coupon tests

were conducted on the column shapes. More thorough material testing of the column

shape, showing the effect of rotary straightening on the material characteristics in the k

anea, was conducted at Lehigh University. (Steel column shapes used for the re earch at

both Lehigh University and UCSD were from the same heat of steel.)

2

I :~


k I I

1.5" to 2"

I I

Figure 1.1 k Area in a Wide-flange Section

k-area

Figure 1.2 Rotary-straightening of Rolled Shape

3

Rollers


2. TESTING PROGRAM

2.1 Test pecimens

Figure 2.4 shows the test setup that is commonly used for the cyclic testing of steel

moment connections. The column and beam seizes for all five specimens were WI4x 176

and W21 x l66, respectively; A992 steel was specified. The column shapes for both the

Lehigh and UCSD specimens were from the same heat (Heat No. 150314 from ucor

Yamato).

Table 2.1 shows the test matrix. The first three specimens (Specimens Kl to K3) did

not use continuity plates and doubler; the only variable was the method of straightening.

Figure 2.5 shows the connection details. The beam was sized to introduce high

concentrated forces through flanges to the column without experiencing significant

yielding and buckling in the beam. Since the objective of this study was focused on the k

area in the column, not the beam flange groove welded joints, these welds were made in

the shop. It was specified that shop welding be done with electrodes having a minimum

Charpy v- otch impact value of 20 ft-Ibs at _200 F. To promote the likelihood of

fracture in the k area such that the relative performance of three columns with different

straightening schemes could be studied, a I-in. diameter drilled hole in the k area, located

at the bottom flange level of the beam, was specified. Nevertheless, the as-received

specimens showed that these holes were actually drilled because the column web was too

thick to punch. It should be noted that the connection was not designed to meet the

seismic design provisions. Instead, the design objective was to introduce large

concentrated forces to the column.

Continuity plates and a 'h-in. thick doubler plate were used for Specimens K4 and

K5 (see Figure 2.6). The doubler plate of A36 steel was groove welded to the column

web near the k area in an attempt to "disturb" the material property in the k area by the

welding heat input.

Fabrication of lest specimens was provided by Herrick Corporation.

4

I :; 1i1


2.2 Material Characteristics

Table 2.2 shows the chemical analysis of the steels as obtained from the certified mill

test reports. Steel coupons were cut from the column web and column flange for tensile

testing at UCSD. The measured mechanical characteristics are presented Table 2.3.

More thorough tensile tests of the coupons taken from the column flange, web, and k

area were conducted at Lehigh University (Kaufmann et aI . 2001); the locations of the

coupons are shown in Figure 2.1, and the results are listed in Table 2.4. Note that the

yield strength of the coupons taken from the k area of the rotary-straightened member

was much higher than those of the other coupons. Rotary straightening also significantly

reduced the elongation, which is a measure of material ductility, from about 30% to 10%.

However, such increase in yield strength reduction in elongation did not exist for the gag

straightened member. A comparison of the stress versus strain curves for the coupons

taken from the k areas is presented in Figure 2.2

Hardness and Charpy V-Notch (CVN) tests were also conducted by Lehigh

researchers. The variations of the measured values in Figure 2.3 clearly show that rotary

straightening significantly reduced the toughness in the k area.

2.3 Specimen Design

2.3.1 Specimen Kl to K3

According to Formula (KI- l) of the LRFD Specification (AlSC 1994), the strength

for the limit state of local flange bending of the column is

R. = 6 .251~ F1f = 6.25(1.31)2(50.0) = 536 kips (2.1)

where the measured yield strength of the column flange is used for Fyf- The strength for

the limit state of local web yielding of the column, as given by Formula (Kl-2) of the

LRFD Specification, is

R. = (5k + N)F ",,I w = (5x 2.0 + 1.36)(52.0)(0.83) '" 490 kips (2.2)

where Fyw is the measured yield strength of the column web. Therefore, local web

yielding governs the strength.

5


A beam size of W21x 166 was selected such that the beam will remain essentially

elastic while supplying a sufficient amount of concentrated force to the column flange.

Assuming that the beam remains elastic and that beam theory can be applied to compute

the bending stress in the beam flange, it can be shown that the beam flange force, PI, at

the column face is related to the applied load, P, as follows:

PLb(d - t j )bj t j Pj = 6.4P

21 s (2.3)

where Lb is the distance from the loading point to the column face. Equating Eqs. 2.2 and

2.3 give a P value when the web local yield strength is reached:

PLWY

= 490 = 76.6 kips 6.4

(2.4)

The panel zone strength based on Formula (9-1) of the AISC Seismic Provisions

(AISC 1997) is

= 0.6(52.0)(15.22)(0.83)[1 + 3(15.65)(1.31)2 ] = 506 ki s 22.48(15.22)0.83 P

(2.5)

Note that the panel zone strength in the above equation corresponds to a shear strain level

of 4 times the shear yield strain. The relationship between the panel zone shear strength

and the applied load is

Vp

, = Pj - Ve = Pj - PLe = 6.4P-l.IP = 5.3P He

(2.6)

where Vc is the column shear force, Le is the distance from the loading point to the

centerline of the column, and He is the column height. Equating Eqs. 2.5 and 2.6 gives the

applied load when the panel zone shear strength is reached:

P = 506 = 95.5 kips '" 5.3

(2.7)

A comparison of Eqs. 2.4 and 2.7 shows that local web yielding would govern the

strength of the test specimens K 1 to K3.

6


2.3.2 pecimens K4 and K5

Continuity plates are u ed such that local flange bending and local web yielding are

not the governing limit states. A II2-inch thick doubler plate was used in Specimens K4

and K5 in order to introduce heat input, by welding, near the k area. The panel zone

strength is thus increased to

V = 506 + 0.6(47.0)(15.22)(0.5)[1 + 3(15.65)(1.31) ' ] = 506 + 316 = 822 kips (2.8) 22.48(15.22)0.5

Lacking coupon test results, the yield strength of the A36 doubler plate is assumed to be

47 ksi (Brockenbrough 2001). Equating Eqs. 2.6 and 2.8 gives the applied load when the

panel zone shear strength is reached:

p., = 822 = 155.1 kips 5.3

(2.9)

Therefore, the strength of test specimens K4 and K5 is expected to be 53% stronger than

the first three specimens.

The strong column-weak beam condition is satisfied for all test specimens:

L M ~ _ 2ZJ 1< 2(320)(50) = 1.48 ~ 1.0 (OK) L M ;' Zb F,. 432(50)

(2.10)

2.4 Test etup

Figure 2.4 shows the test setup. Each specimen was mounted to the strong floor and

the strong wall. To simulate inflection points, the ends of the column were mounted on

shon W 14><370 sections, positioned to experience weak-axis bending. A corbel was

bolted to the free end of the beam and attached to a servo-controlled actuator. Lateral

support for the assembly was provided by a steel column on each side of the beam near

the actuator. The two steel columns were tied together with threaded rods to increase

lateral stiffness. Greased steel plates attached to the support columns were used to

minimize friction between the support column and the beam.

7

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.'" 2.5 Test Procedure

Specimen loading followed the SAC standard loading protocol (Clark et al. 1997).

The loading sequence is presented in Figure 2.7. The loading sequence was controlled by

story drift angle. The loading began with six cycles each at 0.375%, 0.5%, and 0.75%

drift. The next four cycles in the loading sequence were at 1 % drift, followed by two

cycles each at 2%, 3%, 4%, etc., until the specimen fails. Positive drift was defined as

the downward displacement negative bending to the beam.

2.6 Instrumentation

The instrumentation included the use of strain gages, rosettes, and displacement

transducers. Figure 2.8 shows the location of the displacement transducers for

monitoring the global response of the first three specimens. Displacement transducers

L2, L3 were placed diagonally in the column web panel zone to monitor the average

shear deformation. Transducers IA and L5 measured the column movement at the beam

flange levels, while L6, L7, and L8 monitored column end movement, if any. L9 was

used to measure the relative deformation of the column flanges at the top flange level of

the beam. Ll, used to control the loading sequence, measured the overall vertical

displacement at the beam tip. The applied load was measured with a load cell mounted

on the actuator. Carefully arranged strain gages and rosettes, as shown in Figure 2.9,

were used to measure local responses. Similar arrangements for the displacement

transducers, strain gages, and roseltes for Specimens K4 and K5 are presented in Figure

2.10 and Figure 2.11.

2.7 Data Reduction

The data reduction procedure was formulated by Uang and Bondad (1996). The total

plastic rotation of the connection was calculated by dividing the plastic component of the

beam tip displacement by the length from the tip of the beam to the column centerline.

8


'/:>

Table 2.1 Test Matrix

Specimen No. Straightening Method Continuity Plates, Doubler Plate

Kl Rotary No

K2 Gag No

K3 None No

K4 Rotary Yes

K5 None Yes

Table 2.2 Chemical Compositions

Specimen Member Heat No. C Mn P S Si Cu Ni Cr CE

Columns WI4x l76 150314 0.06 1.34 0.015 0.021 0.24 0.34 0.10 0.11 0.35

Beams W21x l66 154423 0.06 1.10 O.ot5 0.033 0.24 0.37 0.12 0.07 0.29

CE C Mn + S. Cr + Mo + V N. + Cu = + + +---

6 5 15

9


Table 2.3 Beam and Column Mechanical Properties

Member Coupon Yield Strength Tensile Strength Elongation

(ksi) (ksil (%)

Column Flange 50.0 66.7 33 Wl4x l76

Web 52.0 70.5 31

(Mill Celt.) (58) (76) (21)

Beam (Mill Cert.) (50.0) (74.0) (22)

W21 x l66 • Based on 8-mch gage length.

Table 2.4 Column Mechanical Properties (Kaufmann et aJ. 2001)

W14x 176 Test Location Yield Strength Tensile Strength Elongation (ksi) (ksi) (%)

Web 54.14 70.34 29.7

Rotary k-area 77.13, 82.41 85.64,84.86 9.4, 9.4 S trai gh tened

Flange 54.01 70.89 31.3

Web 55.06 70.39 28.9

Gag k-area 52.15, 53.00 69.92, 71.04 29.7 Straightened

Flange 53.92 70.99 28.9

Web 56.03 71.22 28.8

Non k-area 54.18, 54.09 71.44, 70.78 29.4, 30.1 Straightened

Flange 54.92 71.87 31.3

• Based 00 8-IOCh gage length.

10

I· I 1 1 I 1 I I I I I I I I I I I I I

W14X176

r-- <t.

J VJI ~ w·,

r-t3l16" r-1 $lUI'

w L:.-

'112": I

Figure 2.1 Tensile Coupon Layout (Kaufmann et aJ. 2(01)

loo~.------------------------------------------,

Ul Ul Q)

60000

~ 40000 (J)

20~

" •

- Unstralghtened . .. Gag Straightened

- - Rotary Straightened

O+-----~-----r----~r-----~----_r----~

0.00 0.05 0.10 0.15

Strain (inlin)

0.20 0.25 0.30

Figure 2.2 k-Area Stress-Strain Behavior for the Three Differently Processed

Sections (Kaufmann et aI . 200 1)

11

I •

I 100 60

I 95 -6- HAS

CVN 50 Ii>

90 .0

40 -. Eo

I CD 85 u. a:: 30 '" :x: 80 "-

I @

I 75 jf! 20 z >

W14 X 176 10 ()

70 Inside Flange Fa e Rotary Straighlened

I 65 0 0 2 3 4 5

Disl From Oulside Flange Face (in.)

I 100 I

60

I 95 ~HRB

lz:==:~ 50

-- CVN Ii> 90 ,e

40 ~

I CD 85 u. a: 30 '" I 80 I r-.

I @

75 /1 20 z

I > W14 X 176

()

70 10 Inside Flange Fa e Gag Straighlened

I 65 0

0 2 3 4 5

Disl From Oulside Flange Face (In.)

I 100 60 ~HRB

I 95

k::: :.:: I __ CVN 50 ~ co

90 .0

40 -. ::: ....... ~

CD 85 .. u.

I a:: 30 '" :x: 80 I "-I @

75 jf! 20 z

I > W14 X 176 10

()

70 Inside Flange Fa e Unstraightened

65 0

I 0 2 3 4 5

Dis!. From Oulside Flange Face (in.)

I Figure 2.3 k-Area Hardness and CVN for the Three Differently Processed Sections

I (Kaufmann et aJ . 2001)

I 12

I· I I I I 1 I I I I I I I I I I I I I

, w

-y

l 11 '-7"

~ 10"

, I , I 6'-3" ,

I ,--

K - ------------~

!, L W21XI66 i- 17' - 3 I 6'-3" , IL W 14X 176

b I IT-I ,

/4"

Vicker ActuatorJ If- l~

T W 14 X 398 ~ 3'-10"

J , I r', ~ , r

Figure 2.4 Overall Dimensions of Test Assembly

13

I ~ 'i) ,~

~.


W14XI76

2" @

6"

2

Punched Hole: I" DlA. -\.1---./

3-112"

3/16 5/16

Section A-A

S/16 B-USa

,-L.<;<>---<Backgouge T&B 30°

R=1/4 W21XI66

112""S",,16" Plate

Bolts: 3/4" A32S 6" on Center

1-3/8" H

30~i' "";\ 11-3/8" IY'

4-118"

v

4-118"

\AI" ~ad.

~ 11-3/8' 30 (jy

H 1-3/8"

I

Weld Access Hole Detail

Figure 2.S Specimens KI to K3: Moment Connection Details

14


n

1-112" THK. ~II--'

Stiffener Plate

112" A36 ~:;........; Doubler Plate

6" --,oj

TYP. >--'::;;:>--,..

W14X176

@

@

@

'--,...,.-< T &B 5/16

45° m/--t--J\rM'--.L..----l 114

Note: Use A36 steel for doubler plate.

See Fig. 2.5 for

connection details

W21X166

DETAll..A

Figure 2.6 Specimens K4 and K5: Moment Connection Details

15

I. o

I ~


0.05 ,--------------------.-.---. S 0.04 ~ 0.03 ~ 0.02 ~ 0.01

---------------.---------------------------- -

€ 0 -l._AJ\

~ -0.01 !2 -0.02 ~ -0.03 E -0.04

-------------------------------------

-0.05 .L---_____________ LLL...J

Loading Step

Figure 2.7 SAC Standard Loading History

f=.-=

b. ~

l I 1'-7"

~ 10"

.. LIIf I L6

1=='" , I L 6'-J"

~ ~

U J-II2" .. ft _._-- --- ..

I ~ 0

1==,. i L W2IXI66 11'-~. I 6'-J"

' I\- W 14 X 176

J"

314"

n&- L8

tr Vicker AClualor....l ~.

~W14X J98 'iii J't ,... r-ii~

II ,

II ii J ~!

:1

II ,

,1 i! Ii ii I , II

Figure 2 ,8 Specimens Kl to 10: Layout of Displacement Transducers

16

I I I I I I I I I I I I I I I I

~ ~

West

West H

c.L. 4 "

A v

2"

Sl;! l"· 2" 2" RI"

S13 -2 S14 _

N2 RJIIO R4

JJ R4'

A v

Beam Top Range (Top Face)

Beam Top Range (Bottom Face)

I - :>4 TS" l -~,

Rosene Dirccuons (R4 only) I I

2 3 )'2

r- r : ~ R5 ,> •

I-

SISJ..r

Note; R4· OD K-I only NOIe: R4 on K-2 and K-3 R4· & R4 placed at 1/2" fro m edge of hole

West

Beam Bottom Range (Bottom Face)

2-112" 2-112"

Figure 2_9 Specimens Kl to K3: Strain Gage and Rosette Locations

17

, .'I I I I I I I I I I I

• I I I I I I

L 6'-3"

t-..,..------I 0

W 2 1 X 166

3'-10"

-!

1.2. 1.3 on Doubler LIO. Lli on Col. Web

17'-314"

Figure 2.10 Specimens K4 and K5: Layout of Displacement Transducers

18

1-I I I I I I I I I I I I I I I I I I

o

rr

II

II RI(R2)

West 2" Beam Top A""e

...,fi (Top Face)

- >I T," -s,

2" Beam Top flanae W es' H (Bouom Face)

-.. T," - «

3 2

N .... RI plaad OIl Doubler l'IIIe IU pIaad OIl Col .... Wei> Rl" 011 K·' DIlly. In" from cd&< o( cope bole

Wes, Beam lIotIom FlaD&e (Top Face)

R4R3 R

••• m;: f.! I f. 2" C.L 2"

Wes' 2" Beam Oo.om Aanae !1 (lIoI,om Face)

Figure 2.11 Specimens K4 and K5: Strain Gage and Rosette Locations

19

1·I I I I I I I I

II I I I I I I I I I

3. TEST RESULTS OF SPECIMENS WITHOUT CONTINUITY

PLATES AND DOUBLER PLATE

3.1 General

Test results of the first three test specimens without continuity plates and doubler

plate will be presented in this chapter. For each test specimen, observed performance

will be presented first, followed by the recorded global and local responses from

displacement transducer and strain gage recordings. The instrumentation plan is shown

in Figure 2.8 and Figure 2.9.

3.2 Specimen Kl (Rotary- traightened Column)

Minor flaking of the whitewash was observed in the panel zone during the I % drift

cycles. At 2% drift, kinking of the column due to panel zone yielding was noticed.

Figure 3.1(a) shows the column kinking at 3% drift. Notice the flaking of whitewash in

the column flange that occurred just above the top flange and below the bottom flange of

the beam. At this drift level , a hairline crack developed at the toe of the groove weld

connecting the beam bottom flange to the column flange [see Figure 3. I (b)]. During the

fust positive excursion of 4% drift, the column flange at the bottom flange level was

almost completely fractured [see Figure 3.2(a)]. Figure 3.2(b) shows that the fracture

extended into the column web and propagated upward near the k area by about half the

beam depth. Before the test was stopped, it was decided to reverse the direction of

loading and to displace the beam to lOin. Figure 3.3 shows the deformed configuration

with severe column kinking. Only minor crack at the toe of the top flange groove weld

was observed (see Figure 3.4); column fracture at the top flange level could not be

developed.

The load ve.rsus deflection relationship of the test specimen is shown in Figure 3.5.

Discarding the cycle where column fracture occurred, the total plastic rotation reached

0.02 radian (see Figure 3.6).

Strain gages were placed on both faces of the beam top flange, 2 in. away from the

column face. A comparison of the readings of a pair of strain gages (51 and 54, see

20

1--I I I I I I I I I I I I I I I I I I

t

Figure 2.9) near one edge of the beam flange is shown in Figure 3.7. Two observations

can be made. First, the strain on the outer (top) surface was higher than that on the inner

surface. Second, the slopes of both plots are opposite in sign, indicating a significant

strain gradient through the thickness of the flange. For example, when the top flange was

in tension, the figure indicates that the top face was in tensile strain, while the bottom

face was in compressive strain although the strain magnitude was low.

Fi ve strain gages (S6 through S 10, see Figure 2.9) were placed across the underside

of the bottom flange to monitor strain profiles. Because continuity plates and doubler

plate were not used, the strain profiles across the flange width at different drift levels

sbowed significant strain concentration (see Figure 3.8). High strains that occurred in the

center of the flange width were responsible for the crack initiation shown in Figure

3.1(b), which eventually led to column fracture.

The column flange tended to bend out of plane (i.e., ''warp'') because continuity

plates were not used; the flaking pattern of the column in Figure 3.2(a) shows this effect.

A displacement transducer (L9) was placed at the top flange level of the beam to monitor

the relative out-of-plane deformation between two column flanges. Prior to column

fracture, the symmetric response in Figure 3.9(a) shows that the deformation was about

the same under both tension and compression forces . To measure the amount of

transverse strain induced by the out-of-plane bending, a strain gage (S 16) was placed

transversely on the inside face of the column flange connecting to the beam. Figure

3.9(b) shows that the transverse strain reached the yield strain at 4% drift.

A total of five gages (S11 through S 14 and RI) were placed vertically along the k

line of the column at the top flange level to monitor the strain profiles (see Figure 3.10).

The highest strain reached 24€y, where €y is the actual yield strain, yet no fracture

developed in the k area. At the top flange level, the strain state in the column k area is

shown in Figure 3.11.

A rosette (R4) was placed above the hole in the k area of the column at the bottom

flange level. The response plots shown in Figure 3.12 indicate that the strain levels were

not high. Consequently, the rosene was placed to the side of the hole for the next two

specimens.

21

I: I I I I I I I I I I I I I I I II II

I

(a) Panel Zone Yielding and Column Kinking

(b) Crack lnitiation at Toe of Bottom Flange Groove Weld

Figure 3. 1 Specimen K I : Panel Zone Yielding and Crack Lnitiation at Toe of

Bottom Flange Groove Weld (3% Drift)

22

I: . I

I '~

I I I I I I I I I I I I I

I I II I

I

I'

(a) Fracture of Column Flange

(b) Propagation of Column Fracture near k Area

Figure 3.2 Specimen K 1: Fracture of Column Flange at Bottom Flange Level and

Propagation near k Area (4% Drift)

23

I·· I I I I I I I I I I I I I I I I I I

Figure 3.3 Specimen Kl: Deformed Configuration at 10 in . Beam Deflection

Figure 3.4 Specimen Kl: Crack at Toe of Top Flange Groove Weld ( lOin. Beam

Deflection)

24

I :~


t ...

Story Drift Ratio -0.08 -0.06 -0.04 -0.02 0.0 0.02 0.04 0.06 0.08

0 0 ~

0 I()

Cii 0.

:;< ~o

'C

'" 0 -'

0 ":'

8 ~ ,

·10 ·5 0 5 10 Deflection (in)

Figure 3.5 Specimen Kl: Load versus Beam Tip Displacement Relationship

~ U. o c E OJ

8":'

-

.

-1lII ~\(' 1\

)

l /.~ 'tJ

-0.06 -0.04 -0.02 0.0 0.02 0.04 0.06 Total Plastic Rotation (rad)

Figure 3.6 Specimen Kl : Moment versus Total Plastic Rotation Relationship

25

I : I I I I I I I I I I I I I I I I I I

'.' ,n

8.---------------.---------------.

'iii' a. g 0 1---"""---'\------1r-\_' ~ .3

'iii' a.

8 ~ , ~ ______ ~ ________ ~ ______ J_ ______ ~

-0,010 -0,005 0.0 Strain

(a) Top Face (51)

0,005 0,010

8.---------------.---------------.

go 1---------~#i~+_~---7_---~

~

-0,010 -0.005 0.0 0.005 0.010 Strain

(b) Bottom Face (54)

Figure 3.7 Specimen Kl : Strain Gradient through Thickness of Beam Top Range

26

I :~ ,-.'

J

I I -4 -2

Normalized Strain o 2 4 8 6

CD

I ~~ ~

I :2 :;:'" , .., ~

0 - - 0.5%

'" ... . . 1.0% 0 I>. i: x + --.- 2.0%

\ '. \ r x - - 3.0% '. \ \

\ 0 I>. i: x

r

\ \ \

\ \ '.

\

S6

S7

I EO os Ql III

E'"

I o ' --~v 0 '

I I /

I / I / r I Ob .//X'

1/ .'/ II /

S8

S9

I CD , 0'" + x

, S10

-0.005 0.0 0 .005 0.010 0.Q15

I Strain

(a) Positive Bending

I Normalized Strain

-8 -6 -4 -2 0 2 4

CD 0 -- -0.5%

I £.q-~

i5

I ~'" :2 ~

,..0 /'x

~.··~I • ... .. -1.0% + .-.- -2.0%

" .' /' " )( -- -3.0% .' /' " " " 0 ._ ... -4% ,.. /' " o· x/ +" I>. 0 , I ,

I I I J ,

S6

S7

I EO os Ql III

f5~

I .::

~"f

, \ \

\ , \ \ , \ \

0 X ~ I>. 0 J \ \

\'" \ r \ \ , \ ,

S8

S9

0 x + 1>.0 S10

I CD , r -O.Q15 -0.010 0 .0 0.005 -0.005

I Strain

(b) Negative Bending

I Figure 3.8 Specimen Kl : Beam Bottom Flange Strain Profiles

I I

27

I I I I I I I I I I I I I I I I I I ,

'[

8

o

'" •

8 ~ • L-~ ______ L-______ ~ ______ -L ______ --W

-0.1

-1

0.0 0.1 Deformation (in)

0.2

(a) Relative Deformation between Column Flanges

Normalized Strain o 1 2 3

0.3

4

;g.ol-I+--U-I--j~+-I--il--+------------"-<

~

-0.002 0.0 0.002 Strain

0.004

(b) Column Range Transverse Strain

0.006

Figure 3.9 Specimen K 1: Response of Column Flange Out-of-plane Defonnation

and Transverse Strain

28

I I I I I I I I I I I I , I I I I

-20 -15

~

~

r

-0.04 -0.03

-10 ·5

0 - -0.5% ... .... . -1 .0% + .-.- -2.0% x -- -3.0% 0 ._ ..... -4% v --- -10 in

,

-0.02 -0.01

Normalized Strain -10 -5 0

,

x + 4:

/ i ) / I : Ii :

X + J>Q

I I ! I I I ,

\ ., : \ \ \ :

\ ., ~ x + \ \ 1 \ \ x~

, -0.02 -0.01

Strain 0.0


Normalized Strain o 5 10 , r -+: x, 0 .,

v, : '. , "', . \ "

': " " " '.

0" + x ' 0

Ii \ , \ \ ,

\ \ .

r '" / ., : ./ / .' ., : .' / /

~ + X' .0 f

5 10

0 -- 0.5% ... .. ... U)% + ._ .- 2.0% x -- 3.0%

0.01 0.02

15 20 ,

-.., -, -, -'-"'v \

\ \ \

, ./ ,

./ , ./

, v' ./ , ,-, 1 i / i / ./

~ I ... ./

X 0 v '

, ,

0.0 0.01 0.02 0.03 0.04 Strain


Sll

S12

AU

S13

S14

Sll

S12

AU

S13

S14

Figure 3.10 Specimen Kl : Strain Profiles along Column k Line at Beam Top

Flange Level

29

I ~ ,t) w ,j)


-60 0 0 ~

0 ~Lt') <I> 0.

go "0

'" 0 ...J

8 ~ ,

-0.10

-60 8 ~

0 ~Lt') <I> 0.

32 ~o

"0

'" 0 ...J

8 ~ ,

8 ~ ,

-0.10

-0.10

-40

-40

Normalized Strain -20 0 20 40 60

~

I:::I;,..Jlu I

-0.05 0.0 0.05 0.10 Strain

(a) Horizontal Component

Normalized Strain -20 0 20 40 60

-0.05 0.0 0.05 0.10 Strain

(b) Vertical Component

Normalized Shear Strain -20 0 20

(/ft, ""

J'. V v..,

-0.05 0.0 0.05 0.10 Shear Strain

(c) Shear Strain

Figure 3.11 Specimen Kl: Strains in the Column k Area at Beam Top Flange Level

(Rl)

30

I'~

I I I I I I I I I I I I I I I I ,

-6 Normalized Strain

-2 0 2 4 6 8~----~----~------r-~--~----~----~

o ~'" ~ ;g, 0 f----------------~

~~------~~--~------~----~ -0.010 -0.005 0.0 0.005 0.010

Strain (a) Horizontal Component

Normalized Strain -6 -4 -2 0 2 4 6

8 .-----~----~----~r_----~----~----__, ~

o ~'" ~ ;g.ol------------------I

~ ~c.......------~----~ ______ '__ ____ ~

-0.010 -0.005 0.0 0.005 0.010 Strain



8r----~---~~---~---,

o ~'" ~ ~o f-----------------~ ~

~~------~~--~------~----~ -0.010 -0.005 0.0

Shear Strain (c) Shear Strain

0.005 0.010

Figure 3.12 Specimen K1 : Strains around Hole in the Column k Area Region (R4)

31

I ·· ,l:>

I I I I I I 11

I I I I I I I I I I I

,..,

3.3 Specimen K2 (Gag-Straightened Column)

Flaking of the whitewash around the hole, an indication of stress concentration,

occurred at 0 .5% drift. Flaking in the panel zone was observed at 0.75% drift. Figure

3. 13 shows the yielding pattern at I % drift. Kinking of the column due to panel zone

yielding was obvious at 2% drift. At 3% drift level , hair-lines cracks developed at the

weld toe of both flanges of the beam. Figure 3.14 shows the extent of crack that

propagated into the column flange at the top and bottom flanges at 4% drift. The column

flange at the top flange level fractured completely at 5% drift [see Figure 3.15(a»).

Fracture in the column flange also led to a separation in the column web [see Figure

3.l5(b»); the fracture extended into the column web and propagated downward near the k

area for about one-fifth of the beam depth. At this point it was decided to reverse the

loading direction to test the column at the bottom flange level. Figure 3.16 shows the

tearing of the hole at different displacement levels. The fracture propagation was gradual,

leading to a slow degradation in strength. The test was stopped at 12 in. beam deflection

(8.6% drift). This specimen performed better than Specimen K1. While the latter one

was not able to complete one cycle at 4% drift, Specimen K2 was subjected to one

complete cycle at 5% drift before the column flange fractured completely.

The load versus deflection relationship of the test specimen is shown in Figure

3.17. Ignoring the incomplete cycle where column fracture occurred, the total plastic

rotation reached 0.04 radian (see Figure 3.18).

Strain gradient through the thickness of the beam flange, similar to that shown in

Figure 3.7, was also observed in this specimen. Figure 3.19 shows the strain profiles

across the width of the beam bottom flange, indicating strain concentration at the mid

width of the beam flange. The out-of-plane deformation of the column flange at the top

flange level is shown in Figure 3.20(a). The transverse strain of the column flange in

Figure 3.20(b) is lower than that of Specimen Kl , probably due to the fracture of the

column flange at the beam top flange level. The strain profiles along the k line of the

column at the top flange level are depicted in Figure 3.21. The maximum tensile strain

reached 12Ey. The strain state in the k area of the column at the top flange level is shown

in Figure 3.22. The measured strains next to the hole at the bottom flange level are

shown in Figure 3.23.

32

r---

I· I I I I I I I I I I I I II I I I I I

(a) Yielding Pattern

(b) Close-up View

Figure 3.13 Specimen K2: Yielding Pattern ( I % Drift)

33


(a) Top Flange Level

(b) BOllom Flange Level

Figure 3. 14 Specimen K2: Fracture of Column Flange (4% Dnft)

34

I· I I I I I I I I I I I I I I I I I I

(a) Fracture of Column Flange

(b) Propagation of Fracture into Column Web near k Area

FIgure 3. 15 Specimen K2: Fracture of Column at Beam Top Flange Level (5%

Drift)

35

I· I I I I I I I I I I

II I I II I I I I I

(a) 7 in. Drift (b) 8 in. Drift

(c) 9 in. Drift (d) lOin. Drift

Figure 3.16 Specimen K2: Fracture Propagation in Hole Region

36

I ,·

1 1 1 1 1 1 1

.....

1 I 1 1 1 1 1 1 1 1 1


8 ~

0 It)

(i) 0.

32 -0 "0 <0

.3 0 ~

8 ~ ,

-10 -5 0 5 10 Deflection (in)

Figure 3.17 Specimen K2: Load versus Beam Tip Deflection Relationship


Figure 3.18 Specimen K2: Moment versus Total Plastic Rotation Relationship

37

I ~-.)

I

I I -2

Normalized Strain o 2 4 8 6

<0

I £~ ~

.r::

I i5 §N , "0

~

0 -- +0.5% .. ..... U)% 0 .6. -I: xo + ._ .- 2.0%

\ \ \. ".

x -- 3.0% \ \. ", 0 ._ .... 4% \ \. \

0 A i: xo -\

'. \ \ "-'. \ \ \ \ .

S6

57

I EO '" Q)

CIl EN

I o ' .:

~'f

I '9

I I IT

I // I /-.. ,

0 .6. .+ /'1> I ' , : / ~ .. . ,/., : / / ,-

O.6.+· XO·

,

58

59

S10

-0.005 0.0 0.005 0.010 0.015

I Strain


I Normalized Strain

-8 -6 -4 -2 0 2 4 , ,

<0 0 -- -0.5%

I g~ .r:: i5

I §N , 31 :::;

V .<> /X .+ .6.0 .. ..... -1.0% I / ,

:.: .... ; + ._ .- -2.0% I

/ / , x -- -3.0% I

/ / 0 ._ ... -4% I / X/

, v --- -5% VO + .6. 0

I I \ I I I

I \ I I I

I ,

56

S7

I EO '" Q)

CIl EN o '

I .:

~'f

I i \ \ \ \ \ \

I I I , \ '. V, <> X + .6. 0 , , \ \

"'\ \ , , \ \ , , , \ \

'v <> x + .0.0

S8

59

510

I '9 ,

-0.015 -0.010 -0.005 0.0 0.005

I Strain


I Figure 3.19 Specimen K2: Beam Bartom Flange Strain Profiles

I I 38


o on

8 ~L-__ ~~ ____ L-____ ~ ____ -L ____ ~ __ ~

-0.2 -0.1 0.0 0.1 0.2 Deformation (in)


Normalized Strain -0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1

8

8 ~L-__ -L ____ ~ ____ ~ ____ ~ ______ L-__ ~

-0.0008 -0.0006 -0.0004 -0.0002 0.0 0.0002 Strain

(b) Column Flange Transverse Strain

Figure 3.20 Specimen K2: Response of Column Flange Out-of-plane Deformation


39

I: I I I I I I I I I I I I I I I I 1 I

-20 -1 5

-

~

-0.04 -0.03

-10 -5

0 -- ~.5% A ..... -1.0% + ._ .- ·2.0% X -- -3.0% 0 ._ .... ·4%

~

-0.02 -0.01

Normalized Strain -10 -5 0

/ 0/ +

Ii I

/ / I , I I

O. x + <>'0 , I I

I '.~ I I

" \. ". I " ' ". '\ '. ",

O.X + ~

' . .\ \. :\ \\ '. :

"'.\ \ . «+.c

-0.02 -0.01 Strain

0.0


Normalized Strain o 5 10

r +',.~" .. , '. '. " ". '. '." " " , ,

0<>' + X 0

I . .

I I I I I i

I

/! I / I I / i I

• ,.. + x .0

f i / /

I .' I /

I / /

I>+ X 0

0.0 0.01 0.02 Slrain


5 10

Sll 0 -- 0.5% A ..... 1.0% + ._.- 2.0% x -- 3.0% 0 ._ .... 4% S12

Rl .l

S13

S14

1

0.Q1 0.02

15 20

Sll

S12

Rl.l

S13

S14

0.03 0.04

Figure 3.21 Specimen K2: Strain Profiles along Column k Line at Beam Top

Flange Level

40



8 ~

0

"'''' Co 32 ~o

"0

'" 0 -J

8 ~ ,

-0.10 -0.05 0.0 0.05 0.10 Strain


-60 -40 Normalized Strain

-20 0 20 40 60 8 ~

0

"'''' Co 32 :;0

'" 0 -J

8 ~ ,

-0.10 -0.05 0.0 0.05 0.10 Strain



8r-----~----~------~----~

-fil ~ 32 :;0 ~--------------+H ~ -J

-0.10 -0.05 0.0 0.05 Shear Strain

(c) Shear Strain

0.10

Figure 3.22 Specimen K2: Strains in the Column k Area at Beam Top Flange

Level (R1)

41

I :~

I I I I I

I I I I I I I I

t

Normalized Strain 0-60 -40 -20 0 20 40 60 0 ~

0 ~'" U) c. ~ ~o

-0 OJ 0 -'0

u;>

0 0 ~ ,

-0.1 0 -0.05 0.0 0.05 0.10 Strain


Normalized Strain 0-60 -40 -20 0 20 40 60 0 ~

0 ~'" U) c. ~ ~o

-0 OJ 0 -'0

u;>

8 ~ ,

-0.10 -0.05 0.0 0.05 0.10 Strain


Normalized Shear Strain 0 -20 0 20 0

0 ~'" U) c. ~ ~o

-0 OJ 0 -10

'" , 0 0 ~ ,

-0.10 -0.05 0.0 0.05 0.10 Shear Strain

(c) Shear Strain

Figure 3.23 Specimen K2: Strains around Hole in the Column k Area (R4)

42

I ~

I ~


3.4 Specimen K3 (Non-straightened Column)

Flaking of the whitewash around the hole was observed at 0.5% drift. Panel zone

yielding occurred during the 0.75% drift cycles (see Figure 3.24). Flaking of the column

flange just above the beam top flange and below the beam bottom flange was noticed at

1.5% drift. Significant column kinking due to the yielding of panel zone occurred at 3%

drift (see Figure 3.25). At the end of 3% drift cycles, sign of cracking at the column

flange at both beam flange levels were observed.

Figure 3.26 shows the extent of column fracture during the first cycle at 5% drift.

Shown in Figure 3.27 is the complete fracture of the column flange during the second

cycle of 5% drift. The extent of fracture propagation around the hole during the 5% drift

cycles is presented in Figure 3.28. Although the propagation of cracks along the kline

was relatively fast , the behavior was not brittle and the strength degradation was limited.

The specimen was able to experience one excursion at 6% drift before it failed in the

reverse excursion. While the fracture in the column flange propagated into the column

web near the k area for Specimens Kl and K2, this was not the case for Specimen K3.

The latter one also performed better than the other two specimens; Specimens Kl, K2,

and K3 experienced complete fracture of the column at 4%, 5%, and 6% drifts,

respectively.


3.29. Ignoring the incomplete cycle where column fracture occurred, the total plastic

rotation reached 0.04 radian (see Figure 3.30).

The strain profiles across the width of the beam bottom flange are shown in Figure

3.31. The out-of-plane deformation of the column flange reached 0.15 in. at 5% drift [see

Figure 3.32(a»). The strain profiles along the k line of the column at the top flange level

are shown in Figure 3.33. Figure 3.34 shows the strain state in the k area at the top flange

level. Figure 3.35 shows the strain state next to the hole at the bottom flange level.

Because the extent of crack in the hole region of Specimen K3 at 5% drift was more

significant than that of Specimen K2 at 6% drift, the softening of the stiffness attracted

less force (or strain) demand in the hole region.

43

I· 1 I I I I I I I I I I I I I I I I I

Figure 3.24 Specimen K3: Panel Zone Yielding Pauern at I % Drift

Figure 3.25 Specimen K3 : Panel Zone Yielding Pattern at 3% Drift

44

I , I ~


Figure 3.26 Specimen K3: Column Flange Fraclure al Beam BOllom Flange Level

(5% Drift, lSI ycle)

Figure 3.27 Specimen K3: olumn Flange Fracture al Beam BOllom Flange Level

(5% Dri ft , 2nd Cycle at 3. 14 In)

45

.' I I I

'. 'I I I I


(a) 5% Drift, I st Cycle (b) 5% Drift, 2nd Cycle at 1.02 in

(c) 5% Drift, 2nd Cycle at 3.14 in (d) 5% Drift, 2nd Cycle at 6 in

Figure 3.28 Specimen K3: Fracture Propagation in Hole Region

46



8 ~

g en a. :x ~o

"0 os 0

...J

~

8 ~ .

-1 0 -5 0 5 10 Deflection (in)

Figure 3.29 Specimen 10: Load versus Beam Tip Deflection Relationship

~ ,---------------------,----------------------, -~ c: '6. :Xo o~

8 ~&()

co Q)~ E . o ::;~ ~ • L-~ ____ ~ __ ~ ____ ~ __ -L __ __' ____ ~___'


Figure 3.30 Specimen 10: Moment versus Total Plastic Rotation Relationship

47

I~

I Normalized Strain

I CD

-2 o 2 4 6 8

0 -- +0.5%

I :§:v .t= i5 §'"

I • "0

~ EO co Q)

I ID

E'" o • .:::

I .~ -.:t o·

.. ... .. 1.0% ()\ + '\. + .-.- 2.0% \. ". ~ x -- 3.0% '. '."

'. '." " ' . , o ~ -+: x

\ \ \ \ \

\ •

I ,.

/ I / ,.

I

r~ //X : .' / : ,./ /

.;. . / ao.X

S6

S7

S8

S9

S10

~

I i.

-0.005 0.0 0.005 0.010 0.015 Strain

I (a) Positive Bending

Normalized Strain -8 -6 -4 -2 0 2 4

I CD

I ~v .t= i5 §'"

I -6 ~ EO '" Q)

I ID

E'" o • .::: .~ v

I o·

l- • 0 - -0.5%

.111 V '> X + A 0 • ..... · 1.0%

..... / ,

I / I + ._.- ·2.0% I x -- ·3.0% .' , / I .... / I 0 ._ ... -4% .' , , I V -_. '5%

'1El 0 X + A 0 • . ...... -6% I- " i / I

I if

/ I :1 I : , I I

" i \ \

\ ' \ \ \ f 1 \ I \ \

III V ~ X + A 0 '. ,

\ '.

\ .... , \ I

I- \ ... ' \ \ I \ . I

III V <> X + A 0

S6

S7

S8

S9

S10 CD •

I -0.015 0.0 0.005 -0.010 -0.005 Strain

I (b) Negative Bending

I Figure 3.31 Specimen K3 : Beam Bottom Flange Strain Profiles

I I 48

II I I I I I I I I I I I I I I I I I

8

g •

8 ~L-__ ~ ______ ~ ____ ~ ____ -L ____ ~ __ --J

-0.5

8

g •

8

-0.2 -0.1 0.0 Deformation (in)

0.1 0.2


Normalized Strain -0.4 -0.3 -0.2 -0.1 0.0 0.1

~L-__ ~ ____ ~ ____ ~ ____ ~ ______ L-__ ~

-0.0008 -0.0006 -0.0004 -0.0002 0.0 0.0002 Strain

(b) Column Flange Transverse Strain

Figure 3.32 Specimen K3: Response of Column Flange Out-of-plane Defonnation


49

I I I I I I I I

,.,

I I I I I I I I I I

Normalized Strain -20 -15 -10 -5 0 5 10

X 7 '" 0 -- 0.5%

/ I I ... ..... 1 .0"~

/ I + ._-- 2.0% x -- 3.0% I I

S11

~ X + Lo 0 \ \ I \ \

\ \

S12

\ , \ I \

, ,

AU

X + LoO \'. : \ \ \ :

\ "' : - X+...:

S13

S14

_L

-0.04 -0.03 -0.02 -0.01 0.0 0.01 0.02 Strain


Normalized Strain -10 -5 o 5 10 15 20

, ,

'2 :::.... Lo b XO ~ ~\~ \~~ > ' . \ '" ~ '. \ "

S11

S12

"' . . '" ", g, '" Lo 0\ \ X, "'0 ., .

~ .... " , , ~ 0 1------------tE~:...-+--*""-/~. ---------i A1 .1

E / .:: " / :ll 0---0.5% : i I I ID ')I ... .... . -1.0% cJ> + X 0

~ ~ '_-' :=' :~:: / ...... ,.' II ,// . 0 · - .... -4% . I / ,.-

in... p+XO 0' S14

S13

-0.02 -0.01 0.0 0.01 0.02 0.03 0.04 Strain

(b) Nega1ive Bending

Figure 3.33 Specimen K3: Strain Profiles along Column k Line at Beam Top

Flange Level

50

I: 111

I .~

I I I I I I I

'I I I I I I I I I I


8

0 _ 10 (I) C. :i: -0 '0 .. 0

...J

8 ~ •

-0.10 -0.05 0.0 0.05 0.10 Strain



8 ~

0 _10 (I)

C. :i: -0 '0 .. 0

...J

8 ~

• -0.10 -0.05 0.0 0.05 0.10

Strain (b) Vertical Component


0 0 ~

-g (I) c. :i: -0 '0 .. 0

...J

8 '7

-0.10 -0.05 0.0 0.05 0.10 Shear Strain

(c) Shear Strain

Figure 3.34Specimen K3: Strains in the Column k Area at Beam Top Flange Level

(Rl)

51

I I I I I I I I I I I I II I

I I I I

Normalized Strain -60 -40 -20 0 20

0 ILl

en a. 32 :;;0

'" .3 0 ILl ,

-0.10 -0.05 0.0 0.05 Strain


-60 -40 Normalized Strain

-20 0 20

0 ILl

en a. 32 :;;0

2! ..J

0 ILl ,

-D.l0 -D.05 0.0 0.05 Strain



en a.

32 -ol---------+_

~ g ,

-0.10 -0.05 0.0 Shear Strain

(e) Shear Strain

0.05

40 60

0.10

40 60

0.10

0.10

Figure 3.35 Specimen K3: Strains around Hole in the Column k Area (R4)

52

In I' . I I I I I I I 1 I I I I I I I I I I

4. TEST RESULTS OF SPECIMENS WITH CONTINUITY PLATES

AND DOUBLER PLATE

4.1 General

Two test specimens to be presented in this chapter were nominally identical to the

rust three specimens presented in Chapter 3, except that continuity plates and doubler

plate were added to enhance the panel shear strength. No attempt was made to avoid

welding in the k area of the column.

4.2 Specimen K4 (Rotary-Straightened Column)

Minor flaking of the whitewash in the panel zone (both the column web and doubler

plate) was first observed at 1 % drift. Flaking in the beam flanges was observed at 3%

drift. Figure 4.1 shows that, at 4% drift, the yielding of the test specimen was

concentrated in the panel zone. The doubler plate experienced more yielding than that in

the column web because a lower grade of steel (A36) was used. Figure 4.2 shows the

kinking of the column due to significant yielding in the panel zone during the first cycle

at 5% drift. After completing one cycle at 6% cycle, the beam top flange experienced

brittle fracture during the second cycle. Figure 4.3 shows that the fracture initiated from

the weld access hole in the k area of the beam web and was due to stress concentration.

The test was then stopped.


4.4. Prior to column fracture, the total plastic rotation reached 0.047 radian (see Figure

4.5). Figure 4.6 shows that the shear defonnations in both the doubler plate and column

web in the panel zone were about the same. The continuity plates were effective to

reduce the strain concentration in the beam flanges (see Figure 4.7). Nevertheless,

continuity plates did not eliminate the strain gradient through the thickness of the beam

flange (see Figure 4.8).

53


(a) Doubler Plate Side

(b) Column Web Side

Figure 4.1 peclmen K4: Yielding of Panel Zone at 4% Drift

54

I' I ~

I I I I I I I

'. I I I I I I I I I


(b) Column Web Side

Figure 4.2 Specimen K4: Column Kinking due to Significant Panel Zone Yielding at 5%

Drift

55


M

(a) Brittle Fracture of Beam Top Flange

(b) Close-up View of Fracture

Figure 4.3 Specimen K4: Btittle Fracture of Beam Top Flange at 6% Drift

56

•• I

. " I



8 N

0 0 ~

U) 0.

:i1 ~o

'0

'" 0 -'

8 ";'

8 C)'

-10 -5 0 5 10 Deflection (in)

Figure 4.4 Specimen K4: Load versus Beam Tip Deflection Relationship



57

1.-'"

I I I £0

6.'" :i<

I ~O ~~

!'l '"

I u. cO E :::>

80 I - ~ '" .

C G>

§~

I :::!!'

I I I £0

6.'" :i<

~o I )(~ -G>

0

'" u.

I cO E :::>

80 - ~

I '" ' C G> Eo 0'"

I :::!! '

I I I I

r-

r-

r

~ ~

~ -0.06 -0.04 -0.02 0.0 0.02

Plastic Rotation (rad)

(a) Column Web

m ~

~ W , , ,

-0.06 -0.04 -0.02 0.0 0.02 Plastic Rotation (rad)

(b) Doubler Plate

0.04

0.04

Figure 4.6 Specimen K4: Panel Zone Responses

58

0.06

0.06

I ,., I

Normalized 5train

I CD

-5 o 5 10 15

0 -- 0.5%

I :?...,. ~

.c;

32

I ~'" , :g ~ EO

I '" '" a:J

8~ .:

I ~~

... .... . 1.0% 0 A + X 0 + ._.- 2.0%

\ , \ \ f- x -- 3.0% '. ,

\ 0 .- .... 4 .0% '. , \ , 0 A + X .0 f-

I 1 \ /

1 \ /

1 , /

I 1 / , 1 / , , • ,

0 A + X ~

I I \ ,

f- 1 \ \ I ,

56

57

58

59

OA + X 0 510

I ~ , ,

-0.01 0.0 0.Q1 0.02 0.03 5train

I (a) Positive Bending

Normalized 5train

I CD

-15 -10 -5 0 5

f- • ,-0 - -0.5%

I :5~ ~

.c; -ti ~'"

I ,:, ~

~ X -+: /:10 .& ..... - 1.0% , \ , l

+ ._.- -2.0% I- \ '.

)( -- -3.0% \ 0 ._ ... -4.0%

'. \ ,

0 x + 0 , I I I : '. , I I , I

56

57

EO ca

I '" a:J

E'" o ' .:

I ]i., 0

/ I f r / I I .

, ,

) ::{ .0 / x I

/ I I

/ I .. I 0 x' + AO

sa

59

510 ~

I , ,

-0.03 0.0 -0.02 -o.Q1 0.Q1 5train

I (b) Negative Bending

I Figure 4.7 Specimen K4: Beam Bottom Range Strain Profiles

I I 59

-~---

I~ ,

I'


--------------- --- - - - - ---------------

8

~

I

-0.10 -0.05

8

~ I

-0.10 -0.05

t'-,.... r-~~

-.n

\\1

~

0.0 Strain

(a) Top Face (S1)

0.0 Strain

(b) Bottom Face (S4)

, , 0.05 0.10

I

0.05 0.10

Figure 4.8 Specimen K4: Strain Gradient through Thickness of Beam Top Flange

60

I '~


4.3 pecimen K5 (Non- traigbtened Column)

The performance of this specimen was very similar to Specimen K4. Figure 4.9

shows the yielding in the panel zone at 3% drift. Figure 4.10 shows that the beam flange

had yielded, but no local buckling was observed. Figure 4.11 depicts the column kinking

due to yielding in the panel zone at 5% drift. At this drift level , sign of stress

concentration at the weld access hole started to show (see Figure 4.12). The curvature of

the beam bottom flange in the weld access hole region, shown in Figure 4.13, was an

indication that a significant amount of beam shear was transferred through the beam

flanges to the column. Brittle fracture of the beam bottom flange occurred during the first

cycle at 6% drift (see Figure 4.14), and the test was stopped. The fracture occurred in the

k area of the beam web due to stress concentration in the weld access hole.


4. I 5. Prior to column fracture, the total plastic rotation averaged 0.038 radian (see Figure

4.16). Figure 4.17 shows that the panel zone shear deformations in both the column web

and the doubler plate were similar. With the presence of continuity plates. the beam

flexural strains across the width of the beam flange were relatively uniform (see Figure

4. I 8). A rosette (R3) was placed 1h in. from the weld access hole of the bottom flange.

Figure 4.19 shows that the venical component of the strain reached 7.4 times the yield

strain.

61

I I'



(b) Column Web Side

Figure 4.9 Specimen K5 : Yielding Pattern in the Panel Zone at 3% Drift

62


Figure 4.10 Specimen K5 : Yielding in Panel Zone and Beam Flange at 3% Drift

Figure 4.12 Specimen KS: Panel Zone Yielding at 5% Drift

63


Figure 4.13 Specimen K5 : Crack Initiation in Top Flange Weld Access Hole at 5% Drift

peC Jll1en K-5

Figure 4.14 Specimen K5: Curvature of Beam Bottom Flange near Weld Access Hole at 5% Drift

,

64


n

(a) Bottom View

(b) Top View

Figure 4. 16 Specimen KS: Brittle Fracture of Beam Bottom Flange during the 6% Drift Cycle

6S

I I I I I I I I I I I I I

Story Drift Ratio -0.08 -0.06 -0.04 -0.02 0.0 0.02 0.04

~

g ,...

g ,... ,

0.06 0.08

~ ~ __________ ~ ________ -L ________ ~ __________ ~

-10 -5 o Deflection (in)

5 10

Figure 4.15 Specimen KS: Load versus Beam Tip Deflection Relationship



66

I·· I I I I I I I I I I I I I I I I I I

- ~ <U •

c: CD Eo ON ~.

-~ <U •

c: CD Eo ON ~.

-0.06 -0.04 -0.02 0.0 0.02

-0.06 -0.04

Plastic Rotation (rad)

(a) Column Web

-0.02 0.0 0.02 Plastic Rotation (rad)

(b) Doubler Plate

0.04 0.06

0.04 0.06

Figure 4.17 Specimen K5: Comparison of Panel Zone Responses

67

.~

•• I I I I

• • I

~ I

I I

• I I I I I I

CD

CD

.~ ~ 0'

CD ,

l-

t-

t-

I-

-0.03

Normalized Strain -5 o 5 10 15

, 0 -- 0.5% A ..... 1.0% ~ -+: x <> + .- .- 2.0% , \ \ x -- 3.0%

, \ \

0 .- .... 4.0% ~ ,

\ '. + x '0.

\"\ \ \ , \ \ '. ,

\ \ ,

/.../ I / /

I / /

I / / Q> t x <>

f I I \

I I I \

~ + x <>

-0.01 0.0 0.01 0.02 0.03 Strain


Normalized Strain -15 -10 -5 0 5

o - .(l.S%

<> x -+: ... 0 ... . .... -1.0% \ \ '. \

+ ._.- -2.0%

" , '. x -- -3.0% , 0 ._ ... -4.0%

\ ,

'0 x + ... 0 I / I I / I

I I ,

\ I I

\ I I ; \ I <> X + ... 0 , / I

I / I : , I ,

<> x + ... <>

-0.02 -0.01 0.0 0.01 Strain


Figure 4.18 Specimen K5: Beam Bottom Flange Strain Profiles

68

S6

S7

S8

S9

S10

S6

S7

S8

S9

S10

I·


Normalized Strain -10 -5 0 5 10

a lI) ~

rna Coli)

8-1:l cua Oll) ...J.

:5 ~

• -0.02 -0.01 0.0 0.01 0.02

Strain (a) Horizontal Component

Normalized Strain -10 -5 0 5 10

a lI) ~

rna Coli)

g 1:l

~:5 ...J.

a lI) ~

• -0.02 -0.01 0.0 0.01 0.02

Strain (b) Vertical Component

Normalized Shear Strain -4 -2 0 2 4 6 8

-0.02 -0.01 0.0 0.01 0.02 Shear Strain

(c) Shear Strain

Figure 4.19 Specimen K5: Strains near Beam Bonom Flange Weld Access Hole

69

I .. I I I I I I I I I I I I 1 I I I I I

S. IMPLICATIONS OF TEST RESULTS

5.1 Test Specimens without Continuity Plates

5.1.1 Failure Mode

All three specimens perfonned and failed in a similar way. But the presence of the l

inch diameter drilled hole was not the cause of failure. Significant yielding in the panel

zone occurred first. Hairline cracks developed at the toe of the beam flange groove welds

at 3% drift ; significant kinking of the column flange was also observed at this drift level.

Local flange bending of the column produced stress concentration and crack initiation at

the center of the column flange. The crack then propagated outward to fracture the

column flange across its width. Complete fracture of the column flange occurred at 4%

drift for Specimen Kl and 5% drift for Specimens K2 and K3.

5.1.2 k Area Response

Based on the strain gage readings, the maximum strain that developed in the k area at

the top flange level of the beam was 24Ey for Specimen Kl and 12Ey for Specimens K2

and K3. No fracture was observed at such high strain levels. At the bottom flange level ,

where a I-inch hole was drilled, crack did not initiate from the hole in Specimen Kl ,

although crack developed in Specimens K2 and K3 at 5% drift. For the particular

connection details and hole arrangement tested, no consistent trend was observed among

all three columns.

5.1.3 Plastic Rotation

Although no continuity plates were used, the plastic rotation capacity was 0.02

radian for Specimen Kl and 0.04 radian for Specimens K2 and K3. Because the details

and welding of the beam flange groove welded joints were not intended to simulate a

field condition, the large plastic rotation should not be construed to imply that continuity

plates are generally unnecessary. On the contrary, for the column size tested, the test

results clearly showed that local flange bending tends to promote crack development at

the toe of the beam flange groove welds.

70

I '~


)

5.1.4 Strength Comparison

The maximum force applied by the top flange of the beam to the column can be

estimated by Eq. 2.3. A comparison of these forces with the LRFD strength (Eq. 2.2) for

local web yielding is shown in Figure 5.1. The LRFD strength is exceeded by 34% on

average. For seismic design , taking advantage of a portion of this overstrength to reduce

the thickness and the associated welding of continuity plates appears beneficial. To

match the measured strength for local web yielding, Eq. 2.2 can be modified as follows:

R, = (7k + N)F 1"1", (5 .1)

5.2 Test Specimens with Continuity Plates and Doubler P late

The maximum load applied to Specimens K4 and L5 was about 58% higher than

those of the first three specimens. Although the beam flanges applied a much higher

force to the column, no fracture in the k areas were observed. Both specimens had a

weak panel zone, delivering a large plastic rotation capacity (0.038 to 0.047 radian).

Significant kinking of the column due to panel zone yielding did not cause fracture.

Instead, since the bending moment in the beam was higher, the beam flange strains ('"

l5Ey) were about twice the values ('" 7Ey) recorded in the first three specimens. Brittle

fracture eventually occurred in the beams, initiating at either the top or bottom flange

from the weld access hole. Stress concentration that occurred in the k area of the beam

was responsible for the crack initiation. To prevent this type of failure , providing a

smooth profile for the weld access hole is very important.

Note that the maximum load achieved in Specimens K4 and K5 correlated well with

that predicted by Eq. 2.9. The measured response also showed that the panel zone shear

deformations in both the column web and the doubler plate were similar.

71


g,--------------------------------------,

Kl K2 K3

Specimen

Figure 5.1 Comparison of Strength for Local Web Yielding

72


6. SUMMARY AND CONCLUSIONS

The research objective was to evaluate the effect of rotary-straightening on the cyclic

behavior of k area in roUed column shapes. A total of five full -scale steel moment

connections with W14x176 column and W21xl66 beam (A992 steel) were tested with the

SAC loading protocol. The first three specimens did not use continuity plates and doubler

plate; the only variable was the method of straightening of the columns (rotary

straightened, gag-straightened, and non-straightened). To promote the potential for

fracture, a I-in. diameter hole was drilled in the k area of the column at the bottom flange

level of the beam. Continuity plates and a doubler plate were used for the last two

specimens-one with a rotary-straightened column and the other one with a non

straightened column. No attempt was made to avoid groove welding of the doubler plate

and continuity plates in or near the k area. Based on the test results, the following

observations can be made.

Maximum strains reached in the k area of the column at the top flange level of the

beam were 24Ey in the rotary-straightened column (KI) and 12Ey in the gag straightened

(K2) and non-straightened columns (K3). No fracture in this area was observed for all

three specimens.

A I-inch bole was drilled in the k area of the column at the bottom flange level of the

beam. No crack initiated from the hole in Specimen Kl . Cracks did initiated from the

hole of Specimens K.2 and K3, although this occurred at a high (5%) drift level. For the

type of details and member size tested, no consistent trend indicating that a drilled hole

would trigger early fracture in the k area of a rotary-straightened column was observed.

The test results showed that, under the cyclic loading condition, the strength as

predicted by the LRFD Specification for the limit state of local flange bending and local

web yielding is conservative. An average overstrength factor of 1.34 for local web

yielding was observed. To reduce the thickness and the associated welding of continuity

plates for the seismic design of steel moment connections, it appears desirable to take

advantage of a portion of this overstrength.

73

I ,

I I I I I I I I


The plastic rotation capacity varied from 0.02 to 0.04 radian for the first three

specimens. Although this modest amount of plastic rotation could be achieved without

using the continuity plates, it should be noted that the details and welding of the beam

flange groove welds were not intended to simulate a field condition. Without the benefit

of continuity plates, the test results clearly showed the potential of crack development in

the column flange due to stress concentration from local flange bending.

When continuity plates and doubler plate were used for the last two specimens (K4

and KS), the behavior and failure mode were similar, no matter whether the column was

rotary-straightened (K4) or non-straightened (KS). Both specimens experienced brittle

fracture of the beam flange at high drift levels ~ 5%). The fracture initiated from the

weld access hole in the k area of the beam, where the transition (i.e., profile) was not

made smooth. To prevent this type of fracture, it is essential to provide a smooth

transition in the weld access hole. Although both Specimens K4 and KS had a very weak

panel zone, and both specimens were able to deliver large plastic rotations , it should be

noted, again, that no attempt was made to simulate a field condition for making the beam

flange groove welds.

This testing program did not reveal adverse effect created by rotary straightening.

However, material testing conducted by Lehigh researchers (see Figure 2.2 and Figure

2.3) clearly showed that the ductility and toughness of the material in the k area were

significantly reduced. Therefore, it is prudent that designers follow the AlSC Advisory

(lwankiw 1997) to avoid welding in the k area.

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REFERENCES

I. AISC (1994), Manual of Steel Construction: Load and Resistance Factor Design,

2nd Edition, Chicago, IL.

2. AISC (1997), Seismic Provision for Structural Steel Buildings, 2nd Edition,

Chicago, IL, with Supplement No. 1, AISC, Chicago, IL.

3. Brockenbrough, R.L. (2001), "MTR Survey of Plate Material Used in Structural

Fabrication," Final Report to AlSC, R. L. Brockenbrough & Associates,

Pittsburgh, P A.

4. Clark, P., Frank, K., Krawinkler, H., and Shaw, R. (1997), "Protocol for

Fabrication, Inspection Testing, and Documentation of Beam-Column Connection

Tests and Other Experimental Specimens," Report No. SAC/BD-97/o2, SAC Joint

Venture, Sacramento, CA.

5. Dexter, R.J., Hajjar, J.F., Prochnow, S.D., Graeser, M.D., Galambos, T.V., and

Cotton, S.C. (200 1), "Evaluation of the Design Requirements for Column

Stiffeners and Doublers and the Variation in Properties in Properties of A992

Shape ," Proceedings, North American Steel Construction Conference, pp. 14-1

to 17-21, AISC, Chicago, IL.

6. Jaquess, T.K. and Frank, K. (1999) "Characterization of the Material Properties of

Rolled Sections," Report No. SAC/BD-99/07. SAC, Sacramento, CA.

7. lwankiw, . (1997), "AlSC Advisory Statement on Mechanical Properties near

the Fillet of Wide Range Shapes and Interim Recommendations," Modem Steel

Construction, Vol. 37. No.2. AlSC. Chicago.lL.

8. Kaufmann, E.J., Metrovich, B., Pense, A.W., and Fisher, 1.W . (2001), "Effect of

Manufacturing Process on k-Area Properties and Service Performance,"

Proceedings, North American Steel Construction Conference, pp. 17-1 to 17-24,

AISC, Chicago, IL.

9. Tide, R. (2000), "Evaluation of Steel Properties and Cracking in "k"-area of W

Shapes," Engineering Structures, Vol. 22, pp. 128-134.

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10. Uang, C.-M. and Bondad, D. (1996), "Static Cyclic Testing of Pre-Northridge

and Haunch Repaired Steel Moment Connection," Report No. SSRP-96/02,

Division of Structural Engineering, University of California, San Diego, CA.

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Jo(' A - AISC Home...W14x176 column and W2lxl66 beam (A992 steel) were tested with the SAC loading...

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