Tests of High-Performance Fiber-Reinforced Concrete Coupling Beams

James K. WightF.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 ≈ 1100% of flexural and shear strength

Construction Issues, L/d ≈ 2Low 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

SP-1 SP-2

3 D16

Test Setup

Actuator

Precast Coupling Beam

“Rigid” Links

Wall Block

Wall Block

Test Specimens

4 D13

SP-1 SP-2

3 D16

Test Specimens

2 D16

2 D16

SP-3 SP-4

2 D16

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

Reinforcement Detail, RC Wall

Beam 1

Beam 2

Beam 3

Beam 4

48 in. (1200 mm) 24 in. (600 mm)

26 in. (650 mm)

54 in. (1350 mm)

42 in. (1050 mm)

42 in. (1050 mm)

42 in. (1050 mm)

12 in. (300 mm)

#2

#37 in. (175 mm)

2.3 in. (60 mm)

3.5 in. (88 mm)

7.5 in. (188 mm)

Confinement spacing:

Design wall concrete shear stress

3wb

2 'c cf

Reinforcement details, RC Wall

RC Wall Behavior; ~ 42% coupling ratio

Reinforcement Detail, FRC Wall

Confinement spacing:

Design wall concrete shear stress

2w wb bor

4 'c cf Beam 1

Beam 2

Beam 3

Beam 4

48 in. (1200 mm) 24 in. (600 mm)

26 in. (650 mm)

54 in. (1350 mm)

42 in. (1050 mm)

42 in. (1050 mm)

42 in. (1050 mm)

12 in. (300 mm)

7 in. (175 mm)

3.5 in. (88 mm)

10.5 in. (263 mm)

8 in. (200 mm)

Comparison of Wall Behavior

R/C

HPFRC

At system drift of 1.5%:o HPFRC: 1 mm crackso RC: Spalling of cover

to expose many stirrups

Damage Tolerance

HPFRC coupling beams are significantly more damage tolerant than reinforced concrete

beams

HPFRC

R/C

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