Tests of High-Performance FiberReinforced Concrete Coupling Beams
James K. Wight
F.E. Richart, Jr. Collegiate Professor
Dept. of Civil and Env. Eng.
University of Michigan
Co-Researchers: Gustavo Parra-Montesinos and Remy
Lequesne, Afsin Canbolat and Monthian Setkit
Key Thought

Change from better rebar details to
enhanced material properties
Mt. McKinley Bldg., Anchorage, Alaska - 1964
Diagonal Reinforcement, L/d ≈ 1
100% of flexural and shear strength
Construction Issues, L/d ≈ 2
Low angle and reinforcement congestion
Research Objectives



Use HPFRC to reduce transverse and
diagonal reinforcement requirements in
coupling beams
Develop information on shear strength
and damage tolerance of HPFRC members
subjected to large displacement reversals
Investigate the use of precast HPFRC
coupling beams in earthquake-resistant
coupled wall systems
Test Specimens
4 D13
3 D16
SP-1
SP-2
Test Setup
Actuator
Wall Block
“Rigid” Links
Precast Coupling
Beam
Wall Block
Test Specimens
4 D13
3 D16
SP-1
SP-2
Test Specimens
2 D16
2 D16
2 D16
SP-3
SP-4
Construction issues: Beam embedment
CB-2 design (L/d = 1.75)
Precast Coupling Beam
Extra mid-depth reinforcement used to move
flexural hinging away from cold joint
CB-2 behavior
CB-2 During Testing
3% Drift
5.5% Drift
Four story
coupled-wall
specimen
• 25% scale
• axial load in lower
stories
• slabs for load
transfer at 2nd and
4th levels
48 in. (1200 mm)
24 in. (600 mm)
12 in. (300 mm)
Reinforcement
Detail,
RC Wall
Beam 4
42 in. (1050 mm)
Beam 3
42 in. (1050 mm)

Confinement spacing:
bw 3
Beam 2
3.5 in. (88 mm)
42 in. (1050 mm)
Design wall concrete
shear stress

c  2 f 'c
2.3 in. (60 mm)
Beam 1
#2
7 in. (175 mm)
#3
54 in. (1350 mm)
26 in. (650 mm)
7.5 in. (188 mm)
Reinforcement details, RC Wall
RC Wall Behavior; ~ 42% coupling ratio
48 in. (1200 mm)
24 in. (600 mm)
12 in. (300 mm)
Reinforcement
Detail,
FRC Wall
Beam 4
42 in. (1050 mm)
Beam 3
42 in. (1050 mm)
Confinement spacing:
bw 2 or bw
 Design wall concrete
shear stress

c  4 f 'c
Beam 2
3.5 in. (88 mm)
42 in. (1050 mm)
Beam 1
7 in. (175 mm)
54 in. (1350 mm)
8 in. (200 mm)
26 in. (650 mm)
10.5 in. (263 mm)
Comparison of Wall Behavior
Damage Tolerance
R/C
R/C

HPFRC
HPFRC
HPFRC coupling beams
are significantly more
damage tolerant than
reinforced concrete
beams
At system drift of 1.5%:
o
HPFRC: 1 mm cracks
o
RC: Spalling of cover to
expose many stirrups
HPFRC Wall Damage
Conclusions – stout coupling beams
• Adequate confinement of diagonal reinforcement is
achieved by HPFRC without the need for bar-type
confinement reinforcement
• Contribution of HPFRC to shear capacity of coupling
beams is significant and must be considered in design
• Precast coupling beam placement proved to be simple
and is believed to be a viable alternative method for
assembling a coupled-wall system
http://nees.org/warehouse/project/47
Innovative Applications of Damage Tolerant
Fiber-Reinforced Cementitious Materials for
New Earthquake-Resistant Structural
Systems and Retrofit of Existing Structures