headed reinforcement
TRANSCRIPT
USE OF HEADED REINFORCEMENT IN BEAM - COLUMN JOINTS
John W. Wallace, Ph.D., P.E.Associate Professor, UCLA
Scott W. McConnell, M.S., P.E.Structural Engineer, Schoor-DePalma, NJ
National Science Foundation
Headed Reinforcement Corporation
ERICO Incorporation
HEADEDREINFORCEMENT ?
Plate Anchor Rectangular/Round Threaded/Friction Weld Area = 5 to 10 Bar Area Beam-Column Joints Standard Hooks Ease of Fabrication & Placement
WHY HEADED REINFORCEMENT ?Congestion/Fabrication/Placement
AVAILABLE INFORMATIONAnchorage/Beam-Column Joints UCLA & Clarkson University
Wallace, McConnell, Gupta Reports/ACI Papers (1994, 1997, 1998)Also Yu (2001)
University of Texas, AustinJirsa, Devries, BashandyPh.D. Dissertations (1996), ACI Paper (1999)
University of KansasMcCabe, Wright, Wu (Reports, 1997)
PROJECT OVERVIEW
EXTERIOR ROOF& CORNER JOINTS
EXTERIOR INTER-STORY JOINTS
HYDRAULIC ACTUATOR
LOAD CELL
CLEVIS
52"
HEAVY LINK
SPECIMENLVDT FOR DISPL.CONTROL
RIGID REFERENCEFRAME
36"
TIE DOWN REACTION WALL
STRONG FLOOR
TEST SETUPExterior Roof Connections
SPECIMEN DETAILSExterior Roof Connections
#5 GR60 US REBAR(16 mm)
#3 STIRRUP(9.5 mm)
14.5"
9.5"0.75"
BEAM CROSS SECTION
11" x 16"280 mm x 406 mm
COLUMN CROSS SECTION
16" x 16"406 mm x 406 mm
#6 (20mm)
14.5"
14.5"0.75"
#3 HOOP & CROSSTIES
(368 mm)(241 mm)
DESIGN REQUIREMENTSExterior Roof Connections
Strong Column - Weak Beam (352-01)
Joint Confinement Reinforcement (352-01)
Joint Shear Stress Limits (352-91)
2 (1.1 Test).1 / beamcolumn MM
(test) 51.1/
f/f )1/(3.0
',,
y'c
dreqshprovidedsh
chgcsh
AA
AAshA
0.1 to 5.0 /
kips 140 to 75P ) 60)(25.1)( (
kips 140)"5.13)("16((psi) 4000 )12)(85.0(2
nu
beamsu
n
VV
ksiinAV
V
DESIGN REQUIREMENTSExterior Roof Connections
Anchorage Requirements– Tension (318 Eq. 21-5, 352-91)
– Compression (318 S12.3)
1.55 to 25.122)/14.23 to (18 /
23.14(psi) f/ 900 (0.75)
(psi) f/ 1200 (psi) f/f 02.0'c
'c
'cy
dprovided
bddbd
dbdb
ll
ddll
ddl
1.5 to 23.16.14/22) to 18( /
14.6 (psi) f/925 (psi) f 65/ f 'c
'c
bbdhprovided
bbbydh
ddll
dddl
LOAD HISTORYExterior Roof/Inter-Story Connections
0 200 400 600 800C o u n ter N u m b er
-6
-4
-2
0
2
4
6
Dri
ft L
evel
(%
)
BC EJ -1
Specimen DamageExterior Roof Connections
KJ16 - Top Bar Pull-out
REINFORCING DETAILSExterior Roof Connections
Top View Side View
Restraint Bars Restraint Bars
Moment-Rotation ResponseExterior Roof Connections
-0 .0 6 -0 .0 4 -0 .0 2 0 .0 0 0 .0 2 0 .0 4 0 .0 6
S p ec im en R o ta tio n
-2 5 0 0
-2 0 0 0
-1 5 0 0
-1 0 0 0
-5 0 0
0
5 0 0
1 0 0 0
1 5 0 0
2 0 0 0M
omen
t (in
-kip
s)
-2 5 0
-2 0 0
-1 5 0
-1 0 0
-5 0
0
5 0
1 0 0
1 5 0
2 0 0
Mom
ent (
kN-m
)
K n ee Jo in t # 1 7
4 .0 % 3 .0 %
2 .0 %
1 .5 %
1 .0 %
M n = 1 5 0 8 in -k ip s (P = 4 9 .5 k ip s)
C lo s in g
O p en in g
M n = 1 0 1 1 in -k ip s (P = -3 3 k ip s)
6 .0 %
0 .5 %
MEASURED REBAR STRAINSBeam Top Bars Within the Joint
-2000
0
2000
4000
6000
MIC
RO
ST
RA
IN TB1-FACE
TB1-MID
1.0% 2.0% 4.0%
1.0% 2.0% 4.0%
0 100 200 300 400 500DATA POINT
-2000
0
2000
4000
6000
MIC
RO
ST
RA
IN TB2-FACE
TB2-END
TEST SETUPExterior Inter-Story Connections
12.75 ft (3.89 m)
10 ft(3.05m)
SPECIMEN GEOMETRYExterior Inter-Story Connections
BEAM CROSS SECTION
18" x 24"457 mm x 610 mm
COLUMN CROSS SECTION
18" x 18"457 mm x 457 mm
DESIGN REQUIREMENTSExterior Inter-Story Connections
Strong Column - Weak Beam (352-01)
Joint Confinement Reinforcement (352-01)
Joint Shear Stress Limits (352-91)
2 (1.7 Test).1 / beamcolumn MM
(test) 17.1/
f/f )1/(3.0
',,
y'c
dreqshprovidedsh
chgcsh
AA
AAshA
80.0/
kips 207 ) 60)(25.1)( 79.04(
kips 260)"18)("18((psi) 4000 )15)(85.0(2
nu
columnu
n
VV
VksiinxV
V
DESIGN REQUIREMENTSExterior Inter-Story Connections
Anchorage Requirements– Tension (318 Eq. 21-5, 352-91)
– Compression (318 S12.3)
352)per (0.82 9.06.14/13 /
14.6 (psi) f/925 (psi) f 65/ f 'c
'c
bbdhprovided
bbbydh
ddll
dddl
0.9113/14.23 /
23.14(psi) f/ 900 (0.75)
(psi) f/ 1200 (psi) f/f 02.0'c
'c
'cy
dprovided
bddbd
dbdb
ll
ddll
ddl
Beam End RotationExterior Interstory Connections
BCEJ1 - Drift Level 6%
Potentiometer
Potentiometer
MOMENT-ROTATIONExterior Inter-Story Connections
-0.06 -0.04 -0.02 0.00 0.02 0.04 0.06JOINT ROTATION 24" FROM THE COLUMN FACE
-6000
-4000
-2000
0
2000
4000
6000
MO
ME
NT
(ki
p-i
n)
6 %
4 %
2 %
3 beam bars in tension
4 beam bars in tension
M n= 2860
M n= 3760
Specimen DamageExterior Interstory Connections
BCEJ1 - Drift Level 6% Bottom Bar Push-Out @ 6%
Compression Bar Push-OutExterior Inter-Story Connections
Beam Moment Capacity Compression Steel Slight Pushout Occurs Redistribution From Steel to Concrete Minor Reduction in Beam Moment Capacity Note - Compression ld Satisfied by Checking Tension ld
Summary ObservationsHeaded Bars in Beam-Column Joints
Required Embedment Length Kansas Study: ld = 0.60 ldh Texas Study: ld = (0.60 - 0.70) ldh UCLA/Clarkson Large-Scale Study: ld = 0.82 ldh Other Design Requirements Flexural Strength Ratio: Mcolumn /Mbeam > 1.2 Joint Shear Emdedded Bars Must Be Shoved To Back of Joint Practical Recommendation for Emdedment ld = 0.75 ldh
CONCLUSIONSBeam-Column Joint Tests
– Six Specimens (3 Exterior, 3 Roof)– Small Cover/Need for Transverse Steel– Push-Out of Compression Bars
ACI Committee 352 Draft Report– Modified to Allow Use of Headed Bars
Research Needs - Cyclic Loading– Cover/Transverse Reinforcement– Multiple Layers of Reinforcement