Tests of High-Performance Fiber- Reinforced 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

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 SP-1SP-2 3 D16

Test Setup Actuator Precast Coupling Beam “Rigid” Links Wall Block

Test Specimens 4 D13 SP-1SP-2 3 D16

Test Specimens 2 D16 SP-3SP-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 2 nd and 4 th levels

Reinforcement Detail, RC Wall Confinement spacing: Design wall concrete shear stress

Reinforcement details, RC Wall

RC Wall Behavior; ~ 42% coupling ratio

Reinforcement Detail, FRC Wall Confinement spacing: Design wall concrete shear stress

Comparison of Wall Behavior

R/C HPFRC At system drift of 1.5%: o HPFRC: 1 mm cracks o 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

Innovative Applications of Damage Tolerant Fiber-Reinforced Cementitious Materials for New Earthquake-Resistant Structural Systems and Retrofit of Existing Structures