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STRUCTURAL RESEARCH SERIES NO. 830 I. NSF/CEE-84035
PB85-'1496J1
SCALE RELATIONSHIPS OF CONCRETE BEAM-COLUMN JOINTS
by Paul R. Philleo and Daniel P. Abrams
A Report to the National Science Foundation Research Grants CEE-8119385 and PFR-8007094
Department of Civil, Environmental, and Architectural Engineering
College of Engineering and Applied Science
University of Colorado, Boulder REPRODUCED BY
NA T!.ONAL TECHNICAL INFORMATION SERVICE
u.s. DEPARTMENT OF COMMERCE SPRINGFiElD, VA. 22:5:
Structural Research Series No. 8301:
SCALE RELATIONSHIPS OF CONCRETE BEAM-COLUMN JOINTS
by
Paul R. Philleo
and
Daniel P. Abrams
A report to the
NATIONAL SCIENCE FOUNDATION
Research Grant CEE-8119385 and PFR-8007094
Department of Civil, Environmental, and Architectural Engineering
College of Engineering and Applied Science
University of Colorado Boulder
February 1984
Any opinions, findings, conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.
ABSTRACT
The objective of this study was to investigate the
ability of reduced-scale models of reinforced concrete
beam-column joints to predict the response of large-scale
prototypes. Six large-scale (approximately three quarter
scale) specimens and six medium-scale (approximately one
quarter scale) specimens were tested. Data from these
tests were combined with data from tests of small-scale
(approximately one-twelfth scale) specimens which were
tested as part of a previous investigation. Each specimen
was subjected to a reversed lateral load which was applied
at the top of each column. Specimens of different scales
were compared with regard to their load-rotation responses.
Explicit scale factors based on the load-rotation
relationship were derived.
ACKNOWLEDGEMENTS
The investigation described in this report was part
of a continuing study of reinforced concrete structures
subjected to earthquake motions. The work was funded by
the National Science Foundation under grants PFR-8007094
iv
and CEE-8119385. Experimental work was done at the Structural
Research Laboratory at the University of Coloradoo
The writers wish to express their appreciation to
Professors Gerstle and Frangopol for their critical review of
the manuscript, and to numerous graduate students, especially
Bill Epp, Scott McNary, and Peter Waugh, for their support.
Acknowledgement is also due to Dave Jones and his staff for
assisting with the fabrication of the test apparatus.
This report was prepared as a thesis for the degree of
Master of Science in Civil Engineering by Paul Philleo under
the direction of Daniel Abrams. Any opinions, findings, and
conclusions or recommendations expressed in this publication
are those of the authors and do not necessarily reflect the
views of the National Science Foundation.
CONTENTS
ACKNOWLEDGEMENTS • . . . . . . LIST OF TABLES . .
LIST OF FIGURES
CHAPTER
1. INTRODUCTION
1.1 Objective and Scope
1.2 Related Research Elsewhere
2. OUTLINE OF EXPERIMENTAL WORK
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.9
Introductory Remarks
General Configuration of the Test Specimens • • . • • . . . • .
Description of the Large-Scale Specimens • . . . . . . . . .
Description of the Medium-Scale Specimens •
Materials .
Fabrication •
Test Apparatus
Instrumentation
Testing Procedure
3. SCALE RELATIONSHIPS OF EXTERIOR JOINTS
3.1 Introduction
3.2 Description of Large-Scale Specimen Response
iv
vii
.viii
1
1
2
6
6
6
9
16
17
19
19
24
26
32
32
32
CHAPTER
4.
5.
3.3 Comparison of Large and Small-Scale Specimens . • •..
SCALE RELATIONSHIPS OF INTERIOR JOINTS
4.1 Introduction
4.2 Description of Large-Scale Specimen Response . . ...
4.3 Comparison of Large-Scale Interior and Exterior Joints. .• •. .
4.4 Differences due to Different Reinforcement
4.5
4.6
Comparison of Large and Small-Scale Specimens . . . . . • .
Comparison of Large and Medium-Scale Specimens
SUMMARY AND CONCLUSIONS
5.1 Summary •.
5.2 Conclusions
5.3 Recommended Future Research •
REFERENCES
APPENDIX
vi
45
50
50
50
65
65
70
73
76
76
77
79
80
85
vii
TABLES
Table
2.1 Summary of Specimens Tested 7
FIGURES
Figu~e
2.1 Configuration of Test Specimens 8
2.2 Specimen Dimensions • 10
2.3 Beam and Column Cross Sections 11
2.4 Shear Reinforcing Detail 13
2.5 End Connections for Large-Scale Specimens 14
2.6 Details of End Connections 15
2.7 Measured Properties for Concrete and Steel 18
2.8 Forrnwork for Large and Medium-Scale Specimens . . . • . • . . 20
2.9 Large-Scale Test Apparatus 21
2.10 Medium-Scale Test Apparatus 22
2.11 Small-Scale Test Apparatus 23
2.12 Description of Physical Quantities Measured 25
2.13 Instrumentation . • . . 27
2.14 Beam Rotation LVDT Arrangement 28
2.15 Location of Strain Gages in Large-Scale Specimens 29
2.16 Displacement Histories 30
3.1 Load-Rotation Response for Exterior Joint 33
3.2 Response of Exterior Joint 34
3.3 Load-Strain Response for Exterior Joint 35
3.4 Photographs of Damage of Exterior Joint 40
3.5 Crack Widths for Exterior Joint . 42
. ,';'
\1.1 I
ix
FIGURE
3.6 Comparison of Small-Scale and Large-Scale Specimens . 46
4.1 Load-Rotation Response for Interior Joint 51
4.2 Load-Displacement Response for Interior Joint . . . . . . . . . 52
4.3 Measured Beam Rotations in Interior Joint 53
4.4 Load-Strain Response for Interior Joint 54
4.5 Photographs of Damage of Interior Joint 60
4.6 Crack Widths for Interior Joint . 62
4.7 Load-Rotation Response for Specimen LIJ4 66
4.8 Photographs of Damage of Specimen LIJ4 67
4.9 Crack Widths for Specimen LIJ4 69
4.10 Comparison of Small-Scale and Large-Scale Specimens . . . . . . . . . . . . 71
4.11 Comparison of Medium-Scale and Large-Scale Specimens . . . . . . . . 74
A.l Load-Rotation Response for Specimen LEJI 86
A.2 Load-:-Rotation Response for Specimen LIJI 87
A.3 Load-Ro~ation Response for Specimen LIJ2 88
CHAPTER 1
INTRODUCTION
1.1 Objective and Scope
The overall objective of this experimental study was to
examine the behavior of large-scale reinforced concrete beam-column
joints and to compare the behavior with reduced-scale models. The
test variables were the configuration and the size of the test
specimens. Interior and exterior joints were tested and behavior of
specimens at three different scales was studied.
Two large-scale exterior and four large-scale interior
joints were constructed and subjected to lateral load reversals. An
additional six interior joint specimens were constructed at medium
(1/4) scale and subjected to deflection histories similar to the
large-scale specimens. One exterior and one interior joint were
tested as a pilot test program by others (10). All other specimens
were tested by this investigator. Small- (1/12) scale interior and
exterior joints were tested at the University of Illinois (12).
Steel and concrete properties and reinforcing ratios for all three
scales were kept similar so direct comparisons between scales could
be made.
This report pertains to all the testing of beam-column joint
specimens at the University of Colorado. A description of test
procedures are presented in Chapter 2. The responses of exterior
J
2
joint specimens and scale relationships of that component
configuration are described in Chapter 3. A similar description for
interior joints constitutes Chapter 4. Sonclusions reached during
the investigation, including recommendations for future scaling
studies, are summarized in Chapter 5.
1.2 Related Research Elsewhere
Use of models to represent behavior of structures is not a
new subject. The early Greeks and Romans used models to design
structures in the absence of mathematical algorithms. In more
recent times, models have been used to predict forces and
deformations in beams, flat plates, box girders, and arch dams, to
name only a few. In Europe, laboratories have been established for
the specific purpose of model studies. Examples of these are the
Laboratorio Nacional De Engenharia Civil in Portugal, the Instituto
Sperimentale Modelli E Strutture in Italy, the Cement and Concrete
Research Association in England, and the Institut fur Modellstatik
at the University of Stuttgart.
In the United States and Japan, tests of small-scale
building models have stimulated new research related to improved
methods of analysis and design. A few examples of innovative
improvements which have used test data from small-scale building
models as a reference are noted in the following. Takeda (19)
formulated complex behavior of reinforced concrete members subjected
to load reversals with a set of rules so that nonlinear dynamic
response could be calculated. Nonlinear analysis of reinforced
concrete frames has been suggested as a design tool (22,23) using
3
similar hysteresis rules. Newmark (18) suggested a simplified
analysis procedure using an elastic analysis with response spectra
modified to include effects of inelastic response. Shibata and
Sozen (20) proposed a design method that used a linear analysis to
represent nonlinear behavior. A substitute structure with member
stiffnesses chosen on the basis of nonlinear behavior was used with
conventional modal analysis procedures. Biggs (21) has evaluated
this approach with the inelastic response spectrum approach and the
equivalent base shear approach. Further simplified analysis
approaches include representing a MDOF structure with a SDOF model
(24), and using modal analysis for bilinear systems (25). New
trends to obtain a simple design criterion for reinforced concrete
frame structures concentrate on simply limiting the drift (26)
without an explicit description of the lateral forces.
Numerous building models have been subjected to simulated
earthquake motions (2,3,4,5,7,8,9) at the University of Illinois.
Other models have been tested in New Zealand (27) and California
(28,29,15), and many tests will probably be done in the future.
Small-scale components of some of these models have been tested by
subjecting them to slowly applied loading reversals (12,13,14,30).
Compa~ison of large-scale components (31,32,33,34,35,36,37, 38,39)
with these small-scale components has been made but only
qualitatively because specimen geometries, amounts of reinforcement,
and loading patterns have not been kept consistent. The question of
modeling was not an issue.
4
Past research on modeling of reinforced concrete behavior at
a small scale is not new. A publication of the American Concrete
Institute (40) summarizes work done in the sixties. Most of this
work was not concerned with dynamic response, but rather direct
scaling of materials to monotonically increasing loads. Work by
Staffier (41) in the seventies addressed the problem of strain-rate
effects on model reinforcement. Krawinkler (42) and Moncarz (43)
investigated correlations between large and small-scale specimen
response. Similar small-scale component models as those described
at the University of Illinois (12,13,14,30) were tested. Their work
did not study the sensitivities of response of a multistory
structure to differences inherent in scaling at the component
level. Verification of conclusions deduced from small-scale
building tests was not within the scope of the research. Various
model studies of multistory concrete buildings have been done in the
People's Republic of China at the Academy of Building Research in
Beijing (44).
Previously at the University of Colorado, Bedell and Abrams
(11) studied scale relationships of concrete columns. A sustained
axial force representing gravity loads was varied for different
specimens to investigate differences in behavior attributable to
inconsistent model~ng of gravitational accelerations. Scale
relationships were defined which showed the ratio of strengths of
different scale specimens to be proportional to the square of the
length scale factor for that particular component.
5
In a U.S.-Japan cooperative effort in Tsukba New Town, a
full-scale seven-story building was tested to failure (1). As part
of the effort, many subprojects have sprouted in the United States.
These projects form a comprehensive study of testing reinforced
concrete buildings for earthquake resistance. Large-scale
components have been tested at the University of Texas. A one-fifth
scale model was tested on an earthquake similator in California
(47), while a one-tenth scale model was tested in Illinois (45).
Another multi-investigator research program was a study of
the Imperial County Services Building in El Centro, California which
was damaged severely by an earthquake in 1979. Large-scale
components of this building have been tested in California. A
one-tenth scale model was tested on an earthquake similator in
Illinois to test the usefulness of small-scale models in estimating
response of full-scale structures (46).
CHAPTER 2
OUTLINE OF EXPERIMENTAL WORK
2.1 Introductory Remarks
Two exterior and four interior large-scale beam-column joint
specimens, and six interior medium-scale specimens were tested as
outlined in the first chapter. This second chapter presents details
of specimen design, fabrication, instrumentation, and test
procedures used for the tests. In addition, figures showing the
dimensions and details of the small-scale specimens tested at the
University of Illinois are included so the reader may compare
specimens at different scales. A summary of all specimens tested is
given in Table 2.1.
2.2 General Configuration of the Test Specimens
The configuration of each beam-column joint was chosen so
that forces would be transferred across the specimen similarly to
those transferred in a similar element in a multi-story frame
structure. Boundary conditions at the ends of the beams and columns
were chosen to replicate idealized points of contraflexure in a
laterally loaded frame. A horizontal load P was applied at the top
of the column (Fig. 2.1) which represented the story shear. A pin
connection at the base of the column, and a roller support at the
end of each beam simulated appropriate restraint conditions.
TABL
E 2
.1
SUM
MAR
Y O
F SP
ECIM
ENS
TEST
ED
SPEC
IMEN
TY
PE
SCA
LE
INV
ESTI
GA
TOR
NU
MBE
R TE
STED
Ex
teri
or
Join
t L
arg
e S
tew
art
(1)
1
Inte
rio
r Jo
int
Lar
ge
Ste
war
t 1
Ex
teri
or
Join
t S
mal
l K
reg
er
(2)
5
Inte
rio
r Jo
int
Sm
all
Kre
ger
4
Ex
teri
or
Join
t L
arg
e P
hil
leo
1
Inte
rio
r Jo
int
Lar
ge
Ph
ille
o
3
Inte
rio
r Jo
int
Med
ium
P
hil
leo
6
(1)
Ste
wart
, J.
and
Abr
ams,
D
.P.,
"C
om
par
iso
n o
f L
arg
e an
d S
mal
l-S
cale
R
ein
forc
ed
Co
ncr
ete
Beh
avio
r",
Mas
ters
T
hesi
s,
Un
ivers
ity
o
f C
olo
rad
o,
July
, 1
98
2.
(2)
Kre
ger
, M
.E.
and
Abr
ams,
D
.P.,
"M
easu
red
Hy
stere
sis
Rela
tio
nsh
ips
for
Sm
all-
Sca
le
Bea
m-C
olum
n Jo
ints
",
Civ
il
En
gin
eeri
ng
Stu
die
s,
Str
uctu
ral
Res
earc
h S
eri
es
No.
4
53
, U
niv
ers
ity
of
Illi
no
is,
Urb
ana,
A
ug
ust
, 1
97
8.
'-.I
8
!z ... ~ ! ... ~
CJl a..
~ Q)
S OM U Q) p..
(J)
.., CJl Q)
H
4-< 0
~ 0
OM .., (\l >-l ;::I bO
OM 4-< ~ 0 U
,.....;
N
. bO
OM
"'"
a..
9
Column and beam lengths were chosen to replicate ratios of
moment-to-shear in an actual frame, and equaled one-half of story
heights or bay widths. Proportioning of flexural strengths was done
so that the beams would be weaker than the columns. Nonlinear
behavior was expected to occur at the ends of the beams while the
column was expected to crack but not yield.
2.3 Description of the Large-Scale Specimens
Specimens dimensions are shown in Fig. 2.2. The large-scale
specimens were nine times larger than the small-scale specimens,
which was equivalent to 3/4 scale; however. large-scale specimens
were considered to be full size because reinforcing bars were #5 or
#6, cross sections were at least 343 x 343 mm (13.5 x 13.5 inches),
and the maximum aggregate size was 20 rom (3/4 inch). To define the
exact scale any closer would require a firm definition of a standard
beam or column size which would be meaningless.
Amounts of longitudinal reinforcement in the beams and
columns of five large-scale specimens (Fig. 2.3) were chosen to
match reinforcing ratios in the small-scale specimens (Fig. 2.3).
Beams were reinforced with three #6 bars on the top and bottom faces
(area of steel on one face was equal to .84% of the effective depth
times the width). Columns were reinforced with eight #5 bars (area
of steel was equal to 1.02% of the gross cross sectional area). The
beams in the sixth specimen were reinforced with five #4 bars on
each face (Fig. 2.3). This area of steel was slightly less (.62%)
than the others, but corresponded to the maximum number of bars
allowed by ACI provisions (16). The reinforcement was changed
10
I b
- --I-f-
b
I I
1 a a
a b
Large Scale 1370 I11III 1030 I11III
Medium Scale 457 !DIll 343 mm
Small Scale 152 mill 114 mID
Fig. 2.2 Specimen Dimensions
a
a
a
larg
e-S
cale
34
3 mm
larg
e-S
cale
. lI
J4
343
mm
Med
ium
-Sca
la
114
mm
Sma l
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cal a
38
mm
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ars
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ars
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m 5
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ire
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Fig
. 2
.3
ilea
m
and
C
olum
n C
ross
S
ecti
on
s I-'
I-'
12
in this specimen to investigate the effect of bar development length
on the steel-concrete bond within the joint region. The column
reinforcement in the sixth specimen was identical to the other five.
Symmetrical layers of beam reinforcement were not
representative of an actual structure which would be governed by
gravity loadings, but was done so that behavior could be compared
with the small-scale specimens. Column shears for the interior
joint specimen were expected to be twice those for the exterior
joint specimen, however the same reinforcement was used for each
because axial forces in an actual structure subjected to lateral
loads would be much larger in the exterior than interior columns.
Although the effect of column axial load was not part of this
investigation, proper replication was felt necessary for
correlations with possible future studies.
Stirrups and ties were provided with a high factor of safety
similar to that used in the design of the small-scale specimens. In
all six large-scale specimens, #3 closed hoops were used in the
columns and beams '(Fig. 2.4), and were spaced according to ACI
requirements (16).
Forces were transferred to the specimens by means of steel
"T" sections which were bolted to embedded plates (Fig. 2.5 and
2.6). The plates were tied to the longitudinal reinforcing bars in
the beam or column, and were held in place during casting by bolts.
These bolts were removed when the forms were stripped. This detail
enabled the "T" sections to be used on all six specimens. Roller
bearings were press-fitted to a hole in the "T" sections to produce
13
-a - b
1-1--- I--- t---~ I- f-- r-~ ~ I--~
I 1::::= ~ ~ I::::=:
I I--- f....- bi
U '\ "\ I ~s INTERIOR JOINT T
II 1I
-~
- ~
a bT r I--
-.;;;..... I'-':-- -{
t>r v I--
I
s~ V-I
EXTERIOR JOINT I I
Io-.~
a b s Large-Scale 102 mm 76 mm #3 closed hoops
Medium-Scole 34 mm 2S mm #9g wire closed hoops
Small-Scale 11 mm 8 mm #16g ,ire spirals
Fig. 2.4 Shear Reinforcing Detail
r A
n ~
~1MM
~
!r
b I>
b
y.
~
l)
17
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e. f}
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UT
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MM
Fig
. 2
.5
En
d
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nn
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r L
arg
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cale
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pecim
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72
MM
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SEC
TIO
N 8
-9
>-'
.l
'-
Fig . 2 . h DL'ldi Is nf End COnnL'l'lLons
)5
16
the pin connection at the column base and beam ends (Fig. 2.6).
2.4 Description of the Medium-Scale Specimens
The medium-scale specimens were three times largeL' than the
small-scale specimens, which was equivalent to 1/4 scale (Fig.
2.2). These specimens were designed to be the smallest possible
into which conventional reinforcing bars would fit for longitudinal
reinforcement. The beams (Fig. 2.3) were reinforced with two #3
bars on the top and bottom faces (area of steel equaled 1% of
concrete area). The columns were reinforced with six #3 bars (area
of steel equaled 2.4% of concrete area). The columns were heavily
reinforced to make sure they remained much stiffer than the beams.
Shear reinforcement was provided by #9 gage wire which was cut from
a spool and bent to form closed hoops (Fig. 2.4). Stirrup and tie
spacing was scaled down from the large-scale design and therefore
coincided with the ACI seismic design provisions (16).
Forces were transferred to the medium-scale specimens by
means of holes through the specimen which were lined with steel
conduit. A bolt extended through these holes and through ball
bearings that had been press-fitted into supporting channels. When
properly connected, the specimen could rotate about the ball
bearing, thus producing the necessary pin connections at the beam
and column ends. The medium-scale test apparatus will be discussed
in more detail in Section 2.7.
17
2.5 Materials
The concrete used in the large-scale specimens was
manufactured and delivered by a local pre-mix concrete firm. Type 1
Portland Cement was used and the maximum aggregate size was 20 mm
(3/4 inch). The mix proportions by weight were .6:1:2.8:3.6 (water:
cement: fine aggregate: coarse aggregate). The concrete used in the
medium-scale specimens was designed and manufactured in the
laboratory. Again Type 1 Portland Cement was used, but the maximum
aggregate size was scaled down to 7 mm (1/4 inch). The mix
proportions by weight were .5:1:2:2.2. Physical properties of the
concrete were determined from samples taken during casting and
tested one day after each specimen was tested. The measured
stress-strain characteristics of the concrete are presented in Fig.
2.7a. Compressive tests were done on 152 by 205 mm (6 by 12 inch)
cylinders in a 1300 kN (300 kip) testing machine. Compressive
strains in the concrete were measured with a mechanical dial gage
sensitive to .03 mm (.001 inch) over a gage length of 127 rom (5
inches). Modulus of rupture tests were done in a 45 kN (10 kip)
testing machine, and split cylinder tests were done in the 1300 kN
testing machine.
The reinforcing bars, hoops, and wire were purchased from a
local manufacturer. The longitudinal reinforcing steel consisted of
deformed bars conforming to ASTM A-615 Specification for Grade 60
steel. The stress-strain characteristics are presented in Fig.
2.7b. These tests were done in a 500 kN (100 kip) capacity load
frame operated in strain control at a rate of .0005 per second.
CONCRETE
30
2D
- LARGE-scALE
..... MEDIUM-SCALE
- - - - SMALL-scALE
.002
STRAIN a
.003 • 0Q.4
~~------~--------~------~------~
300
.OOS
LARGE-scALE
MEDIUM-SCALE
- - - - SMALL-scALE
.010
STRAIN b
.01S .020
Fig. 2.7 Measured Properties for (a) Concrete and (b) Steel
18
19
Strain was related to elongation of the bar measured over a 25 mm (1
inch) length.
2.6 Fabrication
The reinforcing cages were secured together with #16 gage
wire ties. Conventional reinforcing chairs were used to hold the
cage in position during casting. The large-scale specimens were
cast upright in plywood forms stiffened with battens (Fig. 2.8).
The medium-scale specimens were cast flat in wood forms with one
side exposed (Fig. 2.8). The concrete was compacted with a high
frequency vibrator. Cylinder and prism samples were taken
intermittently during casting. All specimens and samples were cured
under moistened burlap for seven days, at which time the forms were
removed. Thereafter the specimens were air cured until the testing
date, 28 days after casting.
2.7 Test Apparatus
Each specimen was loaded with an apparatus which was
designed to simulate the transfer of forces through actual building
elements. Diagrams of the apparatus used to test large, medium and
small-scale specimens are presented in Figs. 2.9-2.11. For the
large and medium-scale tests, load was applied with a 156 kN (35
kip) ram which was mounted on a concrete reaction-block structure.
The reaction block was constructed of four modules which were
prestressed to the test floor. The ram was controlled
electronically so that lateral displacement of the top of the column
would be at a constant rate. This provided a safeguard against
b
Fill· 2 . 8 Formwork fo r (a) Large and (b) Medium-Scale Specimens
to
SW Iv
a A
SS
EM
BLY
II I, j I
II
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ER B
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23
,-__ specimen~ L ____ -4 __ --,
~+ ___ -++ 4-4----._+--- 4--1--- --+-L_ --I ! r-----I~ __ ---1
13 mm 41 0/2") Threaded Bolt W/Coupler
451mm ( 1.5')
Fig. 2.11
I
Collar With Fitted I ' I
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at 4 Locations +.-J
Note: Support Removed f Of Ex.1erio( Join1 Specimens ----...-j
P in Support ----.
Small-Scale Test Apparatus, from Kreeger (12)
24
excessive instantaneous damage if a specimen were to suddenly loose
strength.
The ram was connected to the specimen with a swivel head
which permitted rotation in the vertical and horizontal planes with
negligible resistance. Swivel heads were located on each end of the
ram so that transverse forces would not exist across the ram and
possibly load the specimen out of plane. Roller supports were
simulated at the ends of the beams using a set of steel channels
which were connected at the top and bottom to fixtures with roller
bearings. For the range of lateral displacement used in this test
series, the channels permitted horizontal movement with negligible
resistance and essentially no vertical movement. Out of plane
movements of the specimens were prevented with a set of cables and
turnbuckles which were attached to the beam ends and secured to the
test floor at an angle of 33 degrees with the horizontal.
2.8 Instrumentation
For all specimens, applied load, joint rotation, load-level
displacement, and rotation at beam ends were measured (Fig. 2.12).
In addition, the strains in the reinforcement in the large-scale
specimens were measured. The applied load was measured with the 156
kN (35 kip) capacity load cell with a sensitivity of 0.1%. The
joint rotation was measured using a pair of 127 mm (5 inch) LVDT's.
A rigid aluminum bar, 1830 mm (72 inches) for the large-scale, and
686 mm (27 inches) for the medium-scale was secured to the joint
region on each side of the specimen. A rigid rod connected these
aluminum bars to the core of the LVDT. The load-level displacement
APP
LIED
LO
AD
LOAD
LE
VEL
DIS
PLA
CEM
ENT
JOIN
T
ROTA
TIO
N 1#
~ ...
WES
T BE
AM
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N EA
ST
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TATI
ON
Fig
. 2
.12
D
esc
rip
tio
n o
f P
hy
sical
Qu
an
titi
es
Mea
sure
d
o
N
\.Jl
26
was measured with a 102 mm (4 inch) LVDT in a similar arrangement
(Fig. 2.13).
Inelastic rotations within a specified gage length of 152 rom
(6 inches) for the large scale, and 76 mm (3 inches) for the medium
scale, at the ends of the beams were measured. One 25 mm (1 inch)
LVDT was mounted on the top and bottom faces of each beam and
attached to the column face. Swivel connections were provided so
that free rotation of the LVDT and the core was possible (Fig.
2.14). All displacement transducers had sensitivities of less than
.5 of the range of the particular instrument. Prior to testing,
each transducer was calibrated on a vertical milling machine
sensitive to .003 mm (.0001 inch).
Strains in the longitudinal reinforcement in the large-scale
specimens were measured at locations indicated in Fig. 2.15. Strain
gages were attached to the middle reinforcing bar in each beam.
Voltage outputs from the load cell, LVDT's, and strain gages
were fed into an analog-digital converter. The resulting binary
coded number was read by a Hewlett-Packard 9825T computer which then
stored the number permau~ntly on magnetic tape. Following testing,
the numbers on tape were converted to measurements by the 9825T, and
plotted using a Hewlett-Packard 7225B plotter.
2.9 Testing Procedure
Each large and medium-scale specimen was loaded through
repeated cycles of ever increasing rotation (Fig. 2.16). The first
six cycles led up to the yield load, and the remaining cycles
represented loading in the post-yield region. Joint rotation was
2080 mm
[IJ'~ .' : ' :~'
, " " '/I' !? " .' "
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5action A-A
RIGID ROO ± 102 14M LVOT
A A
~~~--~-----.~~~~ :!:. 127 14M LVDT
'o:t -0)
o '! 127 14M LVOT
Fig. 2.13 Instrumentation
27
28
I r -
FREE ROTATION CONNECTION
t! J Ii E
I 0 r h It)
r 152 mm l
--
CYD1' IIlI.DER\TTACHED TO SPEC'''''''
\ L W
I • I ~ 25 M~ LVDT
......
Fig. 2.14 Beam Rotation LVDT Arrangement
J ,...,
Ie
#1 r'\
'I-'
I
-. -. ,..., -. '{g ~ 111 #i2 m #10
#2 #3 '#4 tIS #6 -. -. 1'1'\ ,..... ,..... '-v 'V 'v 'V ';7
216 mm 216 ! D 152 I 152 216
-
216 mm 216 lJIII 152 I 102
Fig. 2.15 Location of Strain Gages in Large-Scale Specimens
29
-. #(4
#7 ~
'I-' )
216
o cri
o N
o . ... o d
c . ... I
(I) :z III :::t -U III n. (I)
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31
the controlling variable due to its non-dimensional nature.
The tests were monitored by a continuous plotting of load
versus rotation and load versus load-level displacement. All
measured parameters were read at intervals such that a smooth curve
could be obtained later when the data were reduced. Crack patterns
were photographed at the end of each cycle, and at maximum rotations
for large-amplitude cycles. Widths of significant cracks were
recorded at maximum positive, negative, and zero rotations. Each
test took approximately eight hours to complete.
CHAPTER 3
SCALE RELATIONSHIPS OF EXTERIOR JOINTS
3.1 Introduction.
This chapter is a description of how accurately the response
of a large-scale exterior joint was predicted by its small-scale
counterpart. Because the large-scale specimen so nearly resembled
an actual building element, it was considered the control in this
investigation. Its response is described in detail here, then the
response of the small-scale specimen is compared to it. The reader
should recall no medium-scale exterior joints were tested. This was
because the mechanisms exhibited by the exterior joints were simple
compared to those in the interior joints, so it was felt further in
vestigation of the exterior joint at medium scale was not necessary.
3.2 Description of Large-Scale Specimen Response
The load-rotation curve for a large-scale specimen is
shown in Fig. 3.1. It is divided into two graphs for a clearer
presentation. Curves showing load-displacement, load-rotation at
the beam end, and load-strain relationships are shown in Figs.
3.2-3.3. Photographs of damage in the joint region are shown in
Fig. 3.4. Measured widths of significant cracks are listed in Fig.
3.5. The data from just one specimen is presented because the
31-
33
e,~ ____ ~ ______________ ~ ____ ~ ____________ _
EXTERIOR JOINT Sl'ECIMEN
,r-----~------~--------~~~~----------~----------~
-211
-ell .. .. .. .. .. OJ .. .. .. oJ ~ '" .,; '" oJ I I I I
JOINT ROTATION -11111. RADIANS
a
911
EXTERIOR JOINT SPECIMEN lit
<411
211 i
~ • 61
i -21
-<411
-ell
-ell .. ., .. OJ .. OJ .. OJ .. OJ .. OJ .. of oJ oJ 'i '" "' .; oS N 01 I I I I I
JOINT ROTATION -1111, RADIANS
b
Fig. 3.1 Load-Rotation Response for Exterior Joint
~ JDINT SPECllEM I
~+-----~------~------~-----+------~----~~----~----~ .. gj I
-211
~ .. .. rt 't
.. •
.. ;
.. ..
extERIIJI JOINT SPEClIEN I t
.. It .. .. '" .. • 1 .: i' 1 iii iii -I
BEAll IIITAnlll.1&I, RADIANS
Fig. 3.2 Response of Exterior
• .. • - • i
OJ .. n .. - ell ell 01
Joint
34
ElCTERIDR JOINT SPECIMEN
S'TRAIN CAGE.- 1
a~ ______ ~ ____ ~ ______ ~ ____ ~
-211
~~--__ -. ______ ~ ____ ~ ______ ~ ____ ~ ____ ~ __ ----~-----4
60 ~-
-2Q
-60
Fig.
.. N
1 or
EXTERIOR JOINT SPECIMEN
STRA IN CAGE no. 2
'" ,
• ..
o d
STEEl.. STRAIN .,00
b
... II '" .. .. ..
3.3 Load-Strain Response for Exterior Joint
35
z:
'" si a ...J
a
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~
z "
80
60
40
20
o
-20
-EO
-80
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Fig.
---,-------,------,----,----,---,- ---.,----1 EXTERIOR JOINT SPECIMEN
STRA IN GAGE no. :3
EXTERIOR JOINT SPECIMEN
STRA IN GAGE no. 4
'" ,. '" ,.
a ci
STEEt.. STRAIN -lOa
a ci
c
STEEL STRA IN .100
d
/
1 1
1
j I '"
N
3.3 Load-Strain Response for Exterior Joint
36
37
EXTERIDR JOINT SPECIMEN
STlIAIN CAGE.... S
J~----+-----+-----~----~~~~----~------------t
~~~------~~-------N~-----~'-----~.:-----~"------:N;-----~~:-----~~ 111 1 '" Ii '" '" '"
EXTERIDR JOINT SPECIMEN
STlIAIN CACE.- a
21
-ea ... (It N " • ~ N (It ... '" Ii III 1 III III 1 Ii III
I I
stm.. STlIAIN -1111
f
Fig. 3.3 Load-Strain Response for Exterior Joint
~ o ..J
::l
~ ..J 0. a. <:
HO ,.----...--------,r------,-----,------,---,------r--~
EXTERIOR JOINT SPECIMEN J 511
STRIIIN G"CiE no. 7
4U
_._----+ ...... _. -...... +-.-----+---~---+--+----+- ......
-4D
8D.O
60. U
40. 0 ~ 20. a ~
i
--'"
EXTERIOR JOINT SPECIMEN
STRA IN OAGE no. 8
\ "
\'\~' '., " .. ~\
o ci
".
STEEL. STRAIN .100
g
j
ll.ll ~-----I----i---+--~~~---t------j I
-20. 0 ~
-40. U \
I I
-60. a ~
-80. 0 L-.. -.--L..-----l.---.......J----J......---~---_:O:----\Il:::-----:.O ~ ~ ~ ~ 9 ~ m ¢ ~
ci
STEEL. STRAIN -\00
h
Fig. 3.3 Load-Strain Response for Exterior Joint
38
39
u----~--------~--~----~--~----~---+----~--_t
IDI'TiRIDR JOINT SPEl:IMEN
211
~
~ II
fil
i -21 r -411
I
.....a 111 N .. .. .. • .. .. .. N ... .. .. 01 01 f "' 01 '" '" .I .. I I I I
IITEEI.. II'TIIAIH -1.
i
Fig. 3.3 Load-Strain Response for Exterior Joint
L
-
/~
Fig. 3 . 4 Photographs oE Damage of Exterior Joint
Fig . 3 . 4 Pho t ographs or Damage of Exterior Joinl
1ft
42
Cycle
5 .8 .8
6 1.0 .9
7 1.6 1.6
8 1.8 .2 2.0 .2
9 2.5 1.0 2.5 .8
10 3.0 1.6 3.0 1.6
11 3.5 1.6 3.0 1.4
12 5.0 2.0 3.0 1.4
13 5.0 2.5 3.5 1.6
14 5.0 3.0 5.0 2.5
IS 5.0 3.0 5.0 2.5
Fig. 3.5 Crack Widths for Exterior Joint
replication of the response between specimens was quite good. The
following description of the characteristics response of the
large-scale specimen was made in reference to the load-joint
rotation relationship shown in Fig. 3.1.
43
As seen in Fig. 3.1a, the response to initial loading showed
a high elastic stiffness up to point A, which was at 20 kN (4.5
kips). At this point the first flexural cracks opened, which caused
the stiffness reduction seen in the response curve. This stiffness
reduction was also seen in the load-strain curves in Figs. 3.3.
During unloading the stiffness matched the original elastic
stiffness. Loading in the opposite direction produced an identical
response; a high elastic stiffness up to cracking at point B, a
slight reduction in stiffness until unloading began, and a high
unloading stiffness back through zero load.
The remaining five cycles shown in Fig. 3.1a represent all
those in the pre-yield range of loading. During each successive
cycle the loading stiffness decreased from the previous cycle. This
was due to progressive cracking of the specimen, as shown by Figs.
3.4 and 3.5. Unloading stiffness remained high, but by the sixth
cycle a noticeable stiffness reduction occurred near the loading
axis at point C. At this stage, the original flexural cracks had
opened wide enough so a crack on the top of the beam could not close
before a crack on the bottom of the beam began to open. This left
very little of the beam actually in contact with the column and
created, momentarily, a soft section. The stiffness increased
starting at point D in Fig. 3.1a because the cracks in the top of
the beam were then able to close. This was supported by the
load-strain relationships in Figs. 3.3a and b which showed no
increase in compressive strain upon further loading.
44
The eight curves shown in Fig. 3.1b represent the response
in the post yield range of loading. When the load reached 58 kN (13
kips) at point E, yield occurred. This was evidenced by the
load-strain curves in Fig. 3.3. Yielding caused the stiffness
reduction seen after point E. In this range the unloading stiffness
again started out very high, but the stiffness reduction near the
load axis became more pronounced. In the last two cycles, cracking
was so extensive that by the time the top cracks were able to close,
the bottom cracks had opened far enough to prevent a noticeable
increase in stiffness. The load-strain relationships in Fig. 3.3c
and d showed a considerable change in compressive strain in later
cycles which was caused by open flexural cracks. The particularly
low stiffness along segment FG in the final cycle could have been
due to a slight deterioration in bond. However, since the bars were
anchored securely with a 90 degree bend, this effect of bar slip was
minimal in the exterior joint.
Other general observations resulting from testing the
exterior joints were as follows:
1) The shapes of the load-rotation and load-displacement
curves were essentially the same. This indicated the deformations
of the column were nearly elastic during the test.
2) The shapes of the load versus joint rotation and load
versus beam rotation curves were similar, which indicated that most
of the nonlinear action of the beam occurred at the column face.
Furthermore the beam rotations were a significant amount of the
total rotations, which suggested nonlinear behavior in the joint
region.
3) The strength of each specimen did not deteriorate with
cycles of large deformation.
45
4) If a new maximum rotation was not reached during the
current cycle, there was little reduction in stiffness upon loading.
5) If during the current cycle, the specimen was loaded to no
more than the maximum load of the preceeding cycle, there was a
reduction in the area bounded by the hysteresis loop. This
represented a decrease in the amount of energy dissipated which was
a result of increased deformations within the joint region.
6) Each specimen's ability to deform exceed the stroke length
of the loading actuator (+-5 inches). In no case did a crushing
failure or reinforcement fracture occur.
3.3 Comparison of Large and Small-Scale Specimens
For ~omparison purposes the load-rotation curve for the
large-scale specimens was reproduced in Fig. 3.6 along with a
similar curve for the small-scale specimens. In this figure the
vertical axis for the small-scale specimens was normalized to
increase the flexural strength for direct comparison with the
response of the large-scale specimen. The adjustment factor was the
square of the length scale factor (9) multiplied by the ratio of the
products of the reinforcing ratio and the measured yield load:
46
aO.----r--~~--._--~----·~--_r----r_--_r--_.----~--_,--_,
eo EXTERIOR JOINT S~ECIMEN
- - P ult.
zo
o ~--~---4----+----+--~~~-H~~~--1----+----+----+---4
-20
-lID -i' uit. __ _ __ __
JOINT ROTATION 0100. RADIANS
a
- - - - - - - P ult.
21
-4
-811 -P ult. _ _ _ _ _ _ _ _
... • n • n • n • II • II • n • aI ; ; ~ ~ 1 '" "' ~ ~ III III oj I I ,
JOINT' RllTATlIlN .1" IWIlNIS b
Fig. 3.6 Comparison of (a) Small-Scale and (b) Large-Scale Specimens
47
Conventional principles of mechanics assumed for ultimate strength
design were used to determine this scaling factor. The horizontal
axis, rotation, was nondimensional and therefore not adjusted.
Within the range of rotation of +-.010 radians, the
stiffness characteristics exhibited by the large-scale specimens
were modeled well by the small-scale specimens. The response of the
small-scale specimens showed similar trends to the response of the
large-scale specimens with regard to stiffness reduction at first
cracking, a gradual degradation of stiffness upon loading, and a
high unloading stiffness which reduced near zero load. The
small-scale specimens also modeled the slight stiffness increase
upon loading representing crack closure. One further similarity was
that no substantial loading stiffness reduction occurred in cycles
which did not contain new extreme rotations.
When looked at qualitatively, the two figures in Fig. 3.6
gave further information regarding the effects of scaling on
strength and stiffness. A normalized cracking load of about 30 kN
(6.75 kips) was observed for the small-scale specimens. This was
somewhat higher than that of the large-scale specimens. This may
have been attributable to a higher strength in the mortar from which
the small-scale specimens were cast. The normalized maximum load of
the small-scale specimens was approximately 60 kN (13.5 kips) which
matched that of the large-scale specimens.
48
In the load reversal region, the reduced stiffness segment
extended through a rotation equal to approximately .010 radians for
the small-scale specimens, as compared to approximately .005 radians
for the large-scale specimens. This may have been attributable to
bond deterioration which was more prevalent in all of the
small-scale specimens tested. The relatively weaker bond resulted
in the lower average stiffness of a complete cycle for small-scale
specimens.
The weaker bond resistance of the small-scale specimen may
be inferred by the change of slope of the load-rotation curve (Fig.
3.6a). During the first large amplitude cycle, in the first
quadrant of loading, a significant change of stiffness was observed
after cracking but before yield of reinforcement should have
occurred. It should also be noted that no appreciable cracking had
occurred due to diagonal tension within the joint of the specimen.
This change of slope may have been attributable to a localized
deterioration in bonding of beam reinforcement within the column.
During subsequent cycles of loading, the stiffness in this range was
greatly reduced. This tendency was also observed during the third
cycle following the first large amplitude cycle.
Because of the limited range of the response of the
small-scale specimens, direct comparisons with the large-scale
specimens could not be made for rotations greater than .010
radians. However, as previously mentioned, specimens at both scales
resisted nearly equal loads at maximum rotations. These loads were
slightly less than loads calculated by conventional mechanics used
49
in ultimate strength design (16) which have been shown in the
figure. In addition, the unloading slopes during large amplitude
cycles were very similar for specimens at both scales. These
similarities suggest that the large-scale specimens' behavior could
be represented well by the small-scale specimens for loading cycles
in the non-linear, or post-yield, range of response.
CHAPTER 4
SCALE RELATIONSHIPS OF INTERIOR JOINTS
4.1 Introduction
This chapter is a description of how accurately small-(1/12)
and medium-(1/4) scale interior joints models could predict the
response of large-scale prototypes. As with the exterior joints,
the large-scale specimen was considered the control, and its
response is explained in detail. A brief description of the fourth
large-scale specimen follows, P?inting out the differences in
response due to a different distribution of longitudinal
reinforcement. Then the small, and finally the medium-scale
specimen responses are compared to that of the large-scale specimen.
4.2 Description of the Large-Scale Specimen Response
The load-rotation curve representing the first three large
scale specimens is shown in Fig. 4.1. The load-displacement,
load-beam rotation, and load-strain relationships are plotted in
Figs. 4.2-4.4. Photographs of damage and crack information are
presented in Figs. 4.5 and 4.6. Data is presented for just one
specimen because replication with other specimens was very good.
The characteristic response is described with reference to the
load-rotation response of Fig. 4.1.
51
1~r-------~--------~--------T-----------------~------~
INmlIDR JOINT 5P£ClNEN
98
.t--------.--------~----~~~~----~------~------~
-
-laft----------.~------~~---------.~--------n.---------.~------~ft ~ f 1 ~ ~ ~ ~
!lIT!RtDR JOINT i!KC1ME11
Fig. 4.1 Load-Rotation Response for Interior Joint
1811
INTE
RIO
R JO
INT
Sf'E
CltE
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1211
811
i 041
1
§ II
fit ... ~ .....
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1
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li III
III
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III
III
III
III
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III
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Fig
. 4
.2
Lo
ad-D
isp
lace
men
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esp
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se
for
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rio
r Jo
int
l.n
N
-128
-1S~ __ .-+I ____ ., _____ ", __ ~----~ __ ~----~--__ ~ __ ~ ____ ~ __ ~----, .. . .. ot ot i
• -I .. ; • Pi
.. '"
• - • /II • 01
lST----+----~--~----~--~----~----~--~----~--~----~--_T
INTERIIlR JOINT SPECIMEN
-1.+-__ ~----~--~----~--~----~--__ ~--~----~--~----~--~ • 1
Fig. 4.3
n n • .. • r 1 '" 01 -
VEST IEAII RUTATlIII -1l1li. RltDl/lllS
.. - • N n N • 01
Heasured Beam Rotations in Interior Joint
53
~
~ III
~ '"
1~~----------~----~----~------------------~-----r
INTERlDR JOINT SPECIMEN 121
STRAIN CAGE.... I
a~ ____ +-____ +-____ ~ __ ___
-121
-IML---__ ~-------. .-.----~~~----~-------~~-----: ... ------~~:-----~~ ; ; 1 1 = · · · ·
181
1211
£11
411
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-1M V1 N ~ ~ I I
INTERIDR JOINT SPECIMEN
51Wo\IN (lAta _ 2
.. a ~
1 1 1 • .. a 01 01 oS,
.. .. H .I
Fig. 4.4 Load-Strain Response for Interior Joint
54
55
150 i--INTERIOR JOINT SPECIMEN
120 ~ STR~ IN CACE no. 4
"r ~
.0
~ 5 0 Gl
~ <
--0
~r ~ -'t
-WII -- I .. ~ N 0 "! ~ ~ I " d
STEel.. STRAIN -100 C
160 r-----
1 I i I
It<TERIOR JOINT SPIiCIHEN i 120 f- ~
i ~.# I I I STRA I N CACE no. 5
},f'
~ 80 f-
I
I f' I ~. ~
40 I .-0".9~ " ~,/ "
-- .. -::
1 I a f-- -----t--
I I
-40 ~ i j
-30 1-
-120
I J I I
--160 L __ ~ '" "! 0 "! ~ ~
I I I d
STEEL STRA IN -100
d
Fig. 4.4 Load-Strain Response for Interior Joint
100 ,--- - ~-"----r------,-----,-- ---r-----,---~--,__-----, I
i 120 f--
! I
80 ~
~~ or
-40 ~
I -~ I
-120 r I
INTERIOR JOINT SPECIM~N
STRA. I N GACE no. 6
-160 L_...l-. ___ "--__ --' ___ -'-___ -'-___ ~--_::__--__:: ~ m N 0 ~ m ~
I' 1" d
STEEl. STRAIN 0100
e
1a~----~~--~----~----,_----------~----~----_r
121
81
-121
INTERIlIR JOINT !ll'£C11EM
sntt.lll ct.GIt _ T
.. N .. ; ; ; • ..
III III N
III '" III
Fig. 4.4 Load-Strain Response for Interior Joint
56
~
~ fa
i
l~~----~--~~--~----~----~----~----~----~----~----t
1211
41
I
-41
---I.
-11. .. N .: .: I I
INTERIDR JOINT SPECIMEH
STRIIIM GAC!! _ II
.. a .. 't ~ 1
• .. ~ II
t1IIL mAIM -1_ g
.. II
.. ~
II ..
1~~ ________________________ ~~ __ -, ________________ -----+-----, INTERIDR J01NT SPECIMEH
1201
STRIIIH GAOl _ 1.
I~--------------------~~~~--~~--~----t
-12111
h
Fig. 4.4 Load-Strain Response for Interior Joint
57
:<
~ " , a UJ
--' Q.
!l;
1':0
ao
40
a
-40
-80
-120
-160
INTERIOR JOINT SPECIMEN
STRA IN CACE no. 11
OJ
"
Q
d
STEEL. STRAIN *\00
i IS~ ____________________ ~ __________ ~ ____ ~ ____ -,
INTERIOR JOINT SPECIMEN 1211
STRAIN GAG! _ 12
I~-------------------J~~----~--------~
-1211
-lSl-------+-------+-------+-----~:_----~~----~N=_----~~=_----~.~ 11: • • • •
Fig. 4.4 Load-Strain Response for Interior Joint
58
~
~ f3
i
1111
lIITIIUa. JaINI' SPECIMEN 1211
!IT1IAIN CAGE _ 13
III
414
I
-41
-1211
1111~----~----~-----+-----;------~----+-----~-----r
ItmIIJIlR JDJNI' SPIClMEII 1211
STRAIN CAGE _ 14
-1211
-IIII·~·~-----"+-------N~-----~~------.~----~~~----~N~-----:"~----~. ... .. .. .. .. 1 111 ..
Fig. 4.4
S'!1!EL STRAlH el.
1 Load-Strain Response for Interior Joint
59
Fig . 4 . 5 Photographs of Damage of Inlerior Joinl
Fig. 4 . 5 Photographs of Damage of fnteri()r Joint
6/
62
C 1 C
Cycle Al E F
4 .5 .3 .4 .3
5 1.4 .5 1.4 .6 .6
6 1.4 .2 .5 .2 .7 .3 .7
7 2.0 .2 .5 .2 .7 .3 1.0
8 2.0 .2 .7 .2 1.8 .6 1.0
9 2.0 .2 1.4 .2 1.8 .4 1.0 .4
10 3.0 .5 1.4 .2 1.8 .4 1.0 .6 .3
11 3.0 .5 1.4 .2 2.0 1.4 1.0 .6 .3
12 3.0 .5 1.4 .2 2.0 1.5 1.5 .6 .7
13 3.0 .5 2.5 .7 2.5 .6 1.5 .6 1.2 1.0
14 4.0 .6 3.5 .4 3.0 .4 2.5 1.6 1.2 1.0
15 5.0 1.4 4.5 1.0 5.0 .6 2.5 2.0 1.2 1.2
Fig. 4.6 Crack Widths for Interior Joint
63
Referring to Fig. 4.la, the specimens responded to initial
loading with a high elastic stiffness up to the cracking point A,
whi~h occurred at 40 kN (9 kips). Cracking caused a stiffness
reduction which continued until the unloading point. This phenomena
was also observed in the load-strain responses in Fig. 4.4. The
unloading stiffness matched the loading stiffness. As was always
the case, loading in the opposite direction produced an identical
response: a high elastic stiffness reduced when cracks opened at
point B. The reduced stiffness continued until unloading, upon
which the stiffness assumed its high elastic value back through zero
load.
The remaining five cycles shown in Fig. 4.1a represent all
those in the pre-yield range of loading. The gradual decrease in
loading stiffness was caused by progressive cracking in the
specimens. Unloading stiffnesses continued to be high, but near the
load reversal point (point C in Fig. 4.la) a stiffness reduction
became apparent. This was due partially to open flexural cracks on
both faces of the beams, but more importantly, it was due to some
deterioration of the steel-concrete bond within the joint region.
Since the curve between points C and D had some slope, it indicated
the specimens were resisting load. This suggested that the bond had
not been completely destroyed. At point D, flexural cracks on beam
faces A and D (Fig. 4.6) closed, thereby causing a stiffness
increase.
The family of curves in Fig. 4.lb represents the response in
the post-yield range of loading. Yield occurred at a load of 118 kN
64
(26.5 kips) as shown in by load-strain graphs in Fig. 4.4. Yield
caused the stiffness reduction seen at point E on Fig. 4.1b. The
response curves in this range showed the unloading stiffness to
start out very high, but to gradually decrease as the curve
approached zero load. In the load reversal region between points F
and G, the stiffness was observed to decrease more and more. This
was caused by progresive bond deterioration of the beam bars within
the joint. By the final cycle the bond had been completely
destroyed and the curve in that region was essentially horizontal.
With no bond resistance, the tensile force in the beam bars was
constant across the width of the joint. This phenomenon, coupled
with the fact that no concrete was in compression because of open
flexural cracks, caused the specimens to have no resistance to
loading. The specimens could resist load only after the column had
rotated far enough to close some of the flexural cracks and subject
the concrete to flexural compressive stresses.
The progression of bond deterioration could also be inferred
from the load-strain relationships. As more of the bond was
destroyed, a longer segment of a bar was put into tension.
Eventually, when the bond was completely destroyed, the segment of a
bar within the joint region was constantly in tension. This was
seen in Figs. 4.4c,d,h,i,j which were the responses indicated by all
the strain gages within the joint.
65
4.3. Comparison of Large-Scale Interior and Exterior Joints
The six general characteristics listed at the end of Section
3.2 for exterior joints were also observed during the tests of
interior joints. However, the two configurations showed two
distinct differences in their responses. First, the interior joints
resisted twice the load, at both cracking and yield, as did the
exterior joints. This would be expected since the interior joints
had two beams extending from them. The second difference was the
exterior joints showed much less stiffness loss in the load reversal
range of the response. This was because bond deterioration in the
exterior joints was not nearly as great as in the interior joints.
4.4 Differences due to Different Reinforcement
The reader should recall the fourth large-scale interior
joint specimen was reinforced differently from the first three.
While the area of steel in the beams was kept essentially the same,
smaller diameter bars were used. This section discusses the effect
of that change. Fig. 4.7 shows the load-rotation relationship for
this specimen. Photographs of damage and crack information are
given in Figs. 4.8 and 4.9.
The effect of using smaller bars could be seen by comparing
Figs. 4.7 and 4.1. For smaller bars (Fig. 4.7), the pinching of
each hysteresis loop in the vicinity of the origin was not nearly as
pronounced as for larger bars (Fig.-4.1). As discussed in Section
4.3, pinching of a hysteresis loop was an indication of slip of the
beam reinforcement as a result of bond deterioration in the joint
188
I 12
11
sa
i 4&
~ II
fit ... ~ -4
&
-sa
-121
1
-161
11 IS
11
1 15
1
'i N
7
I
Fig
. 4
.7
SPEC
IMEN
LIJ
4
111
151
111
151
111
IS
111
..: .
'# as
as .
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... I
I
JDIN
T RD
TATI
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1811
. RA
DIAN
S
Lo
ad-R
ota
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esp
on
se
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ecim
en L
IJ4
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N
N
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cri
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-
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Fig . 4 . 8 Photogr aphs of Damage of Specimen LIJ4
b/
tl ~,
) } /
" ., - .-
I tl 15 /
r f
I
) '"' I '\, r
Fig . 4 . 8 Pho t ograph s of OamD~c uf Specimen 1.[.14
Cycle
3
4
5
6
7
8
9
10
11
12
13
82
A 1
.2
.4
.7
.9
1.6
1.4
1.6
2.0
2.5
3.0
3.5
.2
.2
.6
.4
.9
.5
1.0
.9
1.8
1.8
2.5
.5 .2
.6 .2
1.2 .4
1.6 .5
2.5 .5
3.0 .5
3.5 1.8
3.5 1.0
4.0 3.5
4.0 3.5
4.5 5.0
.5 .2 .2 .2
.6 .2 .4 .2
1.2 .4 .7 .6
1.6 .5 .9 .4
2.5 .5 1.6 .9
3.0 .5 1.4 .5
3.5 1.8 1.6 1.0
3.5 . 1.0 2.0 .9
4.0 3.5 2.5 1.8
4.0 3.5 3.0 1.8
4.5 5.0 3.5 2.5
Fig. 4.9 Crack Widths for Specimen 11J4
69
E F
.2 .5
.2 .5
.4 .5
.4 .5
.3 .6
.3 .6
.5 1.0
.4 .8
.5 .8
.6 1.0
70
region. The load-rotation curve (Fig. 4.7) suggested bond
deterioration was not as prevalent in the fourth specimen as in the
first three. The reason for this was the shorter development length
of the smaller diameter bars in the fourth specimen. This enabled
the steel to accept higher tensile forces before the bond was
damaged. For this reason, in the future attention should be given
to modeling the ratio of reinforcement development length to the
width of the column.
Another effect of the shorter development length was that
the steel yielded at a lower load of 100 kN (22.5 kips). Ultimately
though, the fourth specimen exhibited essentially the same strength
as the first three. During the final cycle, the loading stiffness
had reduced to where no noticeable yield point could be defined.
This could have been attributable to the Bauschinger effect in the
steel, since by this point the steel had been loaded past its yield
point several times.
Like the first three specimens, the fourth specimen showed
an ability to deform which exceeded the range of the loading
actuator. No crushing failure occurred, nor did the reinforcing
steel ever fracture.
4.5 Comparison of Large and Small-Scale Specimens
For comparison purposes, the load-rotation curve of Fig. 4.1
was reproduced in Fig. 4.10 along with a similar curve from tests of
small-scale specimens. In this figure the vertical axis
71
160
INTERIOR JOINT SPECI~EN 120
SO
z " ~ .w 9 ffi ::; .. .. <
lil N ::; -40 <
~ z
-90
-120
-leo 0 "' 0 "' 0 ~ 0 ~ 0 Ul 0 Ul 0
~ 'l' 'l' i i , c:i
'" '" .. JOINT ROTATION .100. RAOIANS
a
1.
IImRIIIt JOINT 9P!CIMEN 121
• 48
~
! • iii
i -411
... -121
-1 •
• .. • n • n • n :! ., • WI •
'1 '" '" - - 0; '" '" .: '" oJ 01 I I I I
JOINT ROTATION *1_ RADING b
Fig. 4.10 Comparison of (a) Small-Scale and (b) Large-Scale Specimens
for the response of the small-scale specimens was normalized as
previously described in Section 3.3.
72
Within the range of rotation of +-.010 radians, the
small-scale specimens showed similar characteristics to the
large-scale specimens with regard to a stiffness reduction at first
cracking and a gradual stiffness degradation upon loading.
Furthermore, unloading stiffnesses between the two scales matched
very closely. The normalized maximum load of the small-scale
specimens was 120 kN (27 kips), essentially the same as for
large-scale specimens.
The good correlation between scales was not as evident in
the load reversal range of the response (+-lOkN). After just one
load cycle into the nonlinear range, the small-scale specimens lost
bond across the width of the column. The gradual stiffness
degradation caused by progressive bond loss, which was
characteristic of the large-scale specimens, was not modeled at
small-scale. For the small-scale specimens, one complete large
amplitude cycle was sufficient to pull the bar from each side of the
joint in each direction, thereby destroying the bond. Bond
resistance was hampered in the small-scale specimens for two
reasons: first, mechanical anchorage was reduced because the wire
which made up the reinforcement was smooth. Second, the tensile
development length of the wire was approximately 130 rom (5 inches)
based on pullout tests (45). This was considerably greater than the
column width of 50 mm (2 inches). In the large-scale specimens the
development length of the reinforcement was 460 mm (18 inches) based
73
on the ACI document 318-77 (16). This was equal to the width of the
column. Future small-scale specimens may model prototype structures
better if a wider column, bmall diameter wire, or some form of
mechanical anchorage is used.
Subsequent load-cycles of the small-scale specimens revealed
forms of behavior conistent with those described above. After the
large-scale specimen had been put through enough large-amplitude
cycles to completely destroy its bond, its response was very similar
to that of the small-scale specimen. The small-scale specimens did
exhibit some general trends which were characteristic of the
large-scale specimens. Their strength and ability to deform were
never exceeded, subsequent cycles to greater extremes caused reduced
loading stiffnesses, unloading sti.ffnesses began high but decreased
substantially near zero load.
In summary, the small-scale interior joint specimens did not
model the hysteretic response of a large-scale spe~imen in the load
reversal region of the response, until the large-scale specimen had
gone through several large-amplitude loading cycles. Apart from
this deviation, the small-scale specimens were able to mimic both
the strength and the elastic stiffness characteristics of the
large-scale specimens.
4.6 Comparison of Large and Medium-Scale Specimens
The load-rotation curves for the large and medium-scale
specimens are shown in Fig. 4.11. The vertical axis of the response
of the medium-scale specimen was normalized according to the
74
lSI
INTERIOR JOINT SPECIIIElI 1211
911
~
~ 4
iii ~ II .. <
~
i -4
-811
-1211
-1811 os '" .. It1 os It1 .. It1 .. '" .. It1 .. Pi N N i i .; .; .; N N Pi , , , ,
JOINT ROTIITlDII -!IIIII. AADIAIIS
a 11.
IIlT'ERIDR JOINT SPEI:IIEN lZ11
•
.. §
~ • Fa
i .....
---1Z11
-lilt .. .. os II> .. II os .. os It .. ., II
'l' 01 01 ; , , , , .. .. " ~ 01 01 ,,;
JlltNT ROTATlDH -lilli, AADIANS
b
Fig. 4.11 Comparison of (a) Hedium-Scale and (b) Large-Scale Specimens
procedure outlined in Section 3.3. In this case the length scale
factor was 3.
75
The responses in Fig. 4.11 showed that all the sClffness
characteristics exhibited by large-scale specimens were modeled well
at 1/4-scale. Since conventional concrete was used in fabricating
medium-scale specimens, cracking strengths between scales were
essentially the same. Since standard deformed bars were used in the
medium-scale specimens, the degradation in stiffness due to bar slip
was modeled well. The only noticeable differences in the responses
was in the normalized maximum load for the medium-scale specimens,
which was slightly higher than the maximum load for the large-scale
specimens. Unlike the small-scale, medium-scale models of
beam-column joints showed they can be used to replicate behavior of
full-scale prototypes well enough to be used as design aids.
CHAPTER 5
SUMMARY AND CONCLUSIONS
5.1 Summary
The purpose of this investigation was to determine if
reduced scale models could depict the behavior of reinforced
concrete beam-column joints under lateral load reversals. This was
done by examining the differences in response of several test
specimens. Specimens were constructed at large-scale (3/4-scale),
medium-scale (1/4-scale), and small-scale (1/12-scale). Large-scale
specimens were the control specimens. This investigator tested one
large-scale exterior joint, two large-scale interior joints, and six
medium-scale interior joints. One large-scale exterior joint and
two large-scale interior joints were tested by others at the
University of Colorado. All of these tests, combined with the
results of tests of small-scale interior and exterior joints done at
the University of Illinois, provided the data necessary to make
comparisons. In this report data was presented for only one
specimen of each scale and configuration because replication between
like specimens was very good. Comparisons were based on the
strength, stiffness, and energy dissipation characteristics
exhibited by the hysteretic load-rotation relationship of each test
specimen.
76
77
5.2. Conclusions
The results of the research have shown that a reduced-scale
model of a beam-column joint can depict the response of a prototype
within both the linear and nonlinear ranges. Specific conclusions
and recommendations derived from the study are given below:
1) Reduced-scale specimens can be proportioned directly with
the length scale factor. All depth, width, and cover dimensions can
be scaled exactly. Allowance should be given to the percentage and
strength of reinforcement.
2) Story shears resisted by a reduced-scale beam-column jOint
can be related to forces resisted by a large-scale specimen
according to the following relations:
~S
3) Scale relationships for small-scale specimens were highly
dependent on the configuration of the component. For tests of
exterior joints, where the longitudinal reinforcement was securely
anchored in the joint region, overall stiffnesses and strengths were
represented well by small-scale specimens. Tests of the interior
joints did not show such good correlations between scales. Demand
for more bond resistance was inherent for the interior joints
because of the simultaneous push and pull on the beam reinforcement
across the width of the joint. Bond degredation occurred at both
small and large-scales, but to varying extents. Small-scale
78
specimens suffered complete bond loss after only one large amplitude
loading cycle. The loss of bond in the large-scale specimens was
more gradual. This demonstrated the need to develop a more
effective means of anchorage for small-scale reinforcement. The
ratio of the development length of reinforcement to the width of the
column should be considered when designing specimens at
small-scale. Use of small-scale specimens may be used to represent
the hysteretic characteristics of a reinforced concrete beam-column
joint for verification studies of numerical models. However,
precise quantitative representations of these characteristics using
a small-scale model may be inappropriate.
4) Bond degradation was found to be highly dependent on the
development length of longitudinal reinforcing bars. In tests of
large-scale specimens, one reinforced with #4 bars had significantly
less bond loss with no loss in strength than those reinforced with
#6 bars.
5) Specimens fabricated at 1/4-scale, using conventional
concrete and standard deformed reinforcing bars, had very similar
strength and stiffness characteristics to 3/4-sca1e specimens.
Variance between load-rotation curves for large and medium-scale
specimens was smaller than that for large-scale specimens reinforced
differently. Furthermore, the variance was smaller for physical
models constructed at 1/4-sca1e than that for numerical models and
prototypes. Results of the research show that medium-scale
specimens may be used directly for design and analysis of full-scale
reinforced concrete frame structures.
79
5.3 Recommended Future Research
This study determined that simple components of
two-dimensional reinforced concrete frame structures can be
represented well by medium-scale models. Future research should
focus on more complex structures to determine if similar scale
relationships to those put forth in this report can be applied to a
variety of components. Components which could be investigated
should include unsymmetrically reinforced rectangular beams,
T-beams, three-dimensional frames, walls, shell structures, and
cable-stayed or segmentally prestressed bridges. Data from such
tests could be used to verify existing nonlinear analysis
techniques.
Future research should ~lso concrete on the development of
small-scale technology. It would be very advantageous to produce a
1/12-scale model which could predict the response of large-scale
specimens as accurately as a 1/4-scale model.
The results of this study have shown it would be conceivable
to test a 1/4-scale model of a concrete frame structure to examine
the lateral load resistance in many full-scale structures. In a
moderate-sized structural engineering laboratory, it would be
feasible to test a model as tall as twenty stories.
BIBLIOGRAPHY
1. "Recommendations for a U. S.-Japan Cooperative Research Program Utilizing Large-Scale Testing Facilities", U.S.-Japan Planning Group Cooperative Research Program Utilizing Large-Scale Testing Facilities, Earthquake Engineering Research Center, University of California, Berkeley, Report No. 79-26, September, 1979.
2. Gulkan, P., and M.A. Sozen, "Inelastic Response of Reinforced Concrete Structures to Earthquake Motions", Journal of the American Concrete Institute, Vol. 71, No. 12, December, 1974, pp. 601-609.
3. Otani, S., and M.A. Sozen, "Simulated Earthquake Tests of Ric Frames", Journal of the Structural Division, ASCE, Vol. 100, No. ST3, March, 1974, pp. 687-701.
4. Aristizabal-Ochoa, J.D., and M.A. Sozen, "Behavior of Ten-Story Reinforced Concrete Walls Subjected to Earthquake Motions", Civil Engineering Studies, Structural Research Series No. 431, University of Illinois, Urbana, October, 1976.
5. Lybas, J.M., "Concrete Coupled Walls: Earthquake Tests", Journal of the Structural Division, Vol. 107, No. ST5, May, 1981, pp. 835-856.
6. Healey, T.J., and M.A. Sozen, "Experimental Study of the Dynamic Response of a Ten-Story Reinforced Concrete Frame with a Tall First Story", Civil Engineering Studies, Structural Research Series No. 450, University of Illinois, Urbana, August, 1978.
7. Moehle, J.P., and M.A. Sozen, "Earthquake-Simulation Tests of a Ten-Story Reinforced Concrete Frame with a Discontinued First-Level Beam", Civil Engineering Studies, Structural Research Series No. 451, University of Illinois, Urbana, August, 1978.
8. Abrams, D.P., "Experimental Study of Frame-Wall Interaction in Reinforced Concrete Structures Subjected to Strong Earthquake Motions", Seventh World Conference on Earthquake Engineering, Istanbul, Turkey, September, 1980.
9. Moehle, J.P., and M.A. Sozen, "Experiments to. Study Earthquake Response of RIC Structures with Stiffness Interruptions", Civil Engineering Studies, Structural Research Series No. 482, University of Illinois, Urbana, August, 1980.
10. Stewart, J. and Abrams, D.P., "Comparison of Large and Small-Scale Reinforced Concrete Behavior", Masters Thesis, University of Colorado, July, 1982.
81
11. Bedell, R., and Abrams, D.P., "Scale Relationships of Concrete Columns", Structural Research Series No. 8302, Department of Civil Engineering, University of Colorado, Boulder, January, 1983.
12. Kreger, M.E., and D.P. Abrams, "Measured Hysteresis Relationships for Small-Scale Beam Column Joints", Civil Engineering Studies, Structural Research Series No. 453, University of Illinois, Urbana, August, 1978.
13. Gilbertsen, N.D., and J.P. Moehle, "Experimental Study of Small-Scale Ric Columns Subjected to Axial and Shear Force Reversals", Civil Engineering Studies, Structural Research Series No. 481, University of Illinois, Urbana, July, 1980.
14. Abrams, D.P., and M.A. Sozen, "Experimental Study of Frame-Wall Interaction in Reinforced Concrete Sructures Subjected to Strong Earthquake Motions", Civil Engineering Studies, Structural Research Studies No. 460, University of Illinois, Urbana, May, 1979.
15. Aktan, A.E., Bertero, V.V., Chowdhurry, A.A., and Nagashima, T., "Experimental and Analytical Predictions of the Mechanical Characteristics of a liS-Scale Model of a 7-Story Reinforced Concrete Frame-Wall Building Structure", Earthquake Engineering Research Center, University of California, Berkeley, Report No. 83-13, 1983.
16. "Building Code Requirements for Reinforced Concrete (ACI-77)" , American Concrete Institute, Detroit, 1977.
17. Gavlin, N.Lo, "Bond Characteristics of Model Reinforcement", Civil Engineering Studies, Structural Research Series No. 427, University of Illinois, Urbana, April, 1976.
18. Newmark, N.M., "Current Trends in the Seismic Analysis and Design of High Rise Structures", Chapter 16 in Earthquake Engineering, Prentice-Hall, Inc. Englewood Cliffs, N.J., 1970, pp. 403-424.
19. Takeda, T., M.A. Sozen and N.N. Nielsen, "Reinforced Concrete Response to Simulated Earthquakes", Journal of the Structural Division, ASCE, Vol. 96, No. 8T12, December, 1970, pp. 2257-2573.
20. Shibata, A., and M.A. Sozen, "The Substitute-Structure Method for Seismic Design in RIC", Journal of the Structural Division, ASCE, Vol. 102, No. ST1, January, 1976, pp. 1-18.
82
21. Biggs, J.M., W.K. Lau, and D. Persinki, "Aseismic Design Procedures for Reinforced Concrete Frames", Department of Civil Engineering, Massachusetts Institute of Technology, Publication No. R79-21, Order No. 653, July, 1979.
22. Derecho, A.T., S.K. Ghosh, M. Iqbal, and M. Fintel, "Strength, Stiffness, and Ductility Required in Reinforced Concrete Structural Walls for Earthquake Resistance", Journal of the American Concrete Institute, No.8, Vol. 76, August, 1979, pp. 875-896.
23. Fintel, M., and S.K. Ghosh, "Aseismic Design of a 31-Story Frame-Wall Building", Proceedings of ASCE/Engineering Mechanics Division Specialty Conference: "Dynamic Response of Structures: Experimentation. Observation, Prediction, and Control", Atlanta, Georgia, January, 1981, pp. 874-886.
24. Saiidi, M. and M.A. Sozen, "Simple Nonlinear Seismic Analysis of R/C Structures", Journal of the S~ructural Division, ASCE, Vol. 107, No. ST5, May, 1981, pp. 937-952.
25. Tansirikongkol, V. and D.A. Pecknold, "Approximate Modal Analysis of Bilinear MDF Systems", Journal of the Engineering Mechanics Division, ASCE, Vol. 106, No. EM2, April, 1980.
26. Sozen, M.A., "Review of Earthquake Response of R/C Buildings with a View to Drift Control", Seventh World Conference on Earthquake Engineering, Istanbul, Turkey, September, 1980.
27. Wilby, G.K., "Response of Concrete Structures to Seismic Motions", Ph.D. Thesis, Department of Civil Engineering, University of Canterbury, Christchurch, New Zealand, July, 1975.
28. Hidalgo, P., and R.W. Clough, "Earthquake Simulator Study of a Reinforced Concrete Frame", Earthquake Engineering Research Center, University of California, Berkeley, Report No. 74-13, December, 1974.
29. Oliva, M.G., "Shaking Table Testing of a Reinforced Concrete Frame with Biaxial Response", Earthquake Engineering Research Center, University of California, Berkeley, Report No. 80-28, 1980.
30. Abrams, D.P., "Measured HystereSis Relationships for Small-Scale Beams", Civil Engineering Studies, Structural Research Series No. 432, University of Illinois, Urbana, November, 1976.
31. Popov, E.P., V.V. Bertero and H. Krawinkler, "Cyclic Behavior of Three R.C. Flexural Members with High Shear", Earthquake Engineering Research Center, University of California, Berkeley, Report No. 72-5, October, 1972.
32. Soleimani, D., E.P. Popov and V.V. Bertero, "Hysteretic Behavior of Reinforced Concrete Beam-Column Subassemblages", Journal of the American Concrete Institute, No. 11, Vol. 76, November, 1979, pp. 1179-1196.
33. Viwathanatepa, S., E.P. Popov, and V.V. Bertero, "Selsmic Behavior of Reinforced Concrete Interior Beam-Column Subassemblages", Earthquake Engineering Research Center, University of California, Berkeley, Report No. 79-14, June, 1979.
34. Vallenas, J.M., V.V. Bertero and E.P. Popov, "Hysteretic Behavior of Reinforced Concrete Structural Walls", Earthquake Engineering Research Center, University of California, Berkeley, Report No. 79-20, August, 1979.
83
35. Zagajeski, S.W., V.V. Bertero, and J.G. Bouwkamp, "Hysteretic Behavior of Reinforced Columns Subjected to High Axial and Cyclic Shear Forces", Earthquake Engineering Research Center, University of California, Berkeley, Report No. 78-05, 1978.
36. Hanson, N.W., and H.W. Conner, "Seismic Resistance of Reinforced Concrete Beam-Column Joints", Journal of the Structural Division, ASCE, Vol. 93, ST5, October, 1967, pp. 533-560.
37. Uzumeri, S.M., and M. Seckin, "Behavior of Reinforced Concrete Beam-Column Joints Subjected to Slow Land Reversals", Department of Civil Engineering, University of Toronto, Report No. 75-05, March, 1974.
38. Otani, S., and W.T. Cheung, "Behavior of Reinforced Concrete Columns Under Biaxial Lateral Load Reversals", Department of Civil Engineering, University of Toronto, Publication 81-02, Fe bruary, 1981.
39. Jirsa, J. 0., "Development of Loading System and Initial Tests: Short Columns under Bidirectional Loading", Department of Civil Engineering, University of Texas at Austin, CESRL Report 78-2, 1978.
40. Zia, P., R.N. White and D.A. VanHorn, "Principles of Model Analysis", Models for Concrete Structures, Special Publication of American Concrete Institute No. 24, 1970.
41. Staffier, S.R., and M.A. Sozen, "Effect of Strain Rate on Yield Stress of Model Reinforcement", Civil Engineering Studies, Structural Research Series No. 415, University of Illinois, Urbana, February, 1975.
42. Krawinkler, H., "Possibilities and Limitations of Scale-Model Testing in Earthquake Engineering", Proceedings of the Second U.S. National Conference on Earthquake Engineering, Earthquake Engineering Research Institute, August, 1979.
43. Moncarz, P.D., and H. Krawinkler, "Material Simulation in Dynamic Model Studies of Steel and Reinforced Concrete Structures", Seventh World Conference on Earthquake Engineering, Istanbul, Turkey, September, 1980.
84
44. Scholl, Roger E., ed., "EERI Delegation to the People's Republic of China", Earthquake Engineering Research Institute, Berkely, CA, January, 1982.
45. Kreger, M.F. and Sozen, M.A., "A Study of the Causes of Column Failures in the Imperial County Services Building During the 15 October 1979 Imperial Valley Earthquake". Civil Engineering Studies, Structural Research Series No. 509. University of Illinois, Urbana, August, 1983.
46. Wolfgram, Kathy, Report on I/IO-scale Model of Japanese Full-Scale 7-Story Test Structures, University of Illinois, 1984.
APPENDIX
Load-Rotation Curves
for Other Large-Scale Specimens
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