HIGH PERFORMANCE FIBER REINFORCED CEMENT

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					HIGH-PERFORMANCE FIBER REINFORCED CEMENT
 COMPOSITES FOR NEW COUPLED WALL SYSTEMS
AND RETROFIT OF EXISTING FRAMED STRUCTURES
Submitted By:
James K. Wight1, Gustavo J. Parra-Montesinos1, Sarah Billington2, Sherif El-Tawil1, Antoine E. Naaman1,
and James LaFave3
1
 University of Michigan, 2Stanford University, 3University of Illinois
Department of Civil and Environmental Engineering
2340 G.G. Brown Building
Ann Arbor, MI 48109-2125

Submitted to Session (please mark one):

!    5. NEESR Project Spotlight NEW/Recently Underway PROJECTS (NEESR Project personnel only)


Major points/topics:

"   Strain-hardening, high-performance fiber reinforced cement composites to develop highly
    damage-tolerant earthquake-resistant structures.
"   Component tests will be conducted to evaluate the behavior of precast coupling beams and
    panels for use in new coupled wall systems and for retrofitting deficient framed structures,
    respectively.
"   Hybrid system tests that combine state-of-the-art finite element simulation with large-scale
    experimentation will be conducted for evaluation of the behavior of the proposed coupled
    wall system and the efficiency of the retrofit scheme during earthquakes.

Abstract/Summary
This research integrates researchers in the field of fiber cement composites, reinforced concrete,
computational mechanics and large-scale experimentation to develop new coupled wall systems
and a cost-effective, rapidly implemented retrofitting technique for deficient framed structures.

This research was conceived from the idea that the next generation of reinforced concrete (RC)
structures should utilize ductile cementitious materials in critical regions, rather than extensive
reinforcement detailing to provide shear resistance, concrete confinement and thus, an increase in
deformation capacity of structural members and systems. In other words, the approach is to use a
“better material” rather than “more material”. Recent breakthroughs in fiber reinforced concrete
technology have made this possible by allowing the achievement tensile strain-hardening
behavior in cementitious materials with the use of relatively low volume fraction of
discontinuous fibers (approximately 1.5%). Tensile strain capacities that exceed 1.0%, and a
compression behavior that resembles that of well-confined concrete are typical of this new
generation of fiber reinforced cement composites. Because of their superior response compared
to traditional fiber reinforced concretes, these materials are often referred to as high-performance
fiber reinforced cement composites (HPFRCCs).
The two primary applications for HPFRCC materials to be developed in this research are coupled
shear walls in reinforced concrete (RC) structural systems and infill panels used to upgrade steel
or RC framed structures by adding stiffness, strength, and energy dissipation capacity. Coupled
shear walls are a popular structural system for medium-rise structures in zones of moderate to
high seismicity. During a large earthquake it is anticipated that the coupling beams will undergo
significant inelastic deformations and it is important for these beams to have a high energy
dissipation capability and good stiffness retention. Steel reinforcement detailing required in RC
coupling beams to resist earthquake-induced deformations are labor intensive and costly, which
often lead practicing engineers to discard their use in medium- and high-rise construction.

In this investigation, the behavior of coupled wall systems that feature precast, lightly reinforced
HPFRCC coupling beams will be investigated through hybrid tests that combine refined finite
element simulation with large-scale testing of structural subassemblies (Figure 1). To facilitate
system construction, it is proposed that the HPFRCC coupling beams be precast at a remote
location. The precast beams would then be brought to the site and placed between the wall forms
before concrete is cast at that particular story level. HPFRCC materials will be used 1) as a
replacement for steel confinement reinforcement, 2) to provide additional shear resistance, and 3)
to increase coupling beam damage tolerance. The NEES MUST-SIM Facility at the University of
Illinois, in combination with the NEES-grid, will offer the opportunity to take HPFRCC
materials to the system level and develop the next generation of coupled wall systems capable of
remaining operational after a major earthquake without the need for major repairs.

The second proposed application for HPFRCC materials is for the construction of precast infill
panels that will be used to upgrade steel and RC framed structures by adding lateral strength,
stiffness, and energy dissipation capacity (Figure 2). This phase of the research is focused on
steel framed structures and in particular critical facilities (hospitals, emergency response centers,
schools, telecommunications centers, laboratories etc.), that must remain in full service during
any seismic upgrade construction activity, as well as during repair activities after a seismic event.
Therefore, the emphasis is on small and light precast units that can easily be moved into the
facility and installed without disrupting normal operations. These elements are sized for the
ability to be transported in an elevator and handled by two workers. The NEES RRW-ESF
facilities at UC Berkeley will be used to evaluate the effectiveness of HPFRCC infill elements
for the seismic upgrading of existing frame structures through large-scale experimentation and
simulation (Figure 2).
                                   LBCBs (attached to strong wall)




                                                RC Wall            1.0 m
            Precast HPFRCC
            Coupling Beam
                                     0.9 m                         1.6 m                                          NEESGrid
                                                                                                                Computer Clusters
                                                RC Wall            1.0 m                                         Storage Devices
                                                                                                                   Middleware

                         a) Coupling Beam Component Test                                                           Networking


                                             LBCBs (attached to strong wall)




                                                                                                                    MGRID
                                                                                                                   FEA Code
                                                                                                                 NPACI Clusters
1.0 m
                                                                                                                 Storage Devices
1.0 m                 RC Loading                                                                                   Middleware
                      Block                               0.4m
                                                                                                                   Networking
1.6 m
                                                                     Precast HPFRCC
                                                                     Coupling Beams


                      RC Coupled
1.6 m                 Wall            1.5 m               0.7 m


                                                                               RC Wall
1.0 m                                                                          Foundation



                             b) Coupled Wall Specimen                                                                               c) Prototype 10-story Wall Structure
                                   Figure 1 - Test specimen simulating coupling beams and coupled-wall base
                                                                                 Reconfigurable Reaction Wall
                                                                                  U.C. Berkeley NEES Site




                                                                                                                 Experiment
        ~4.5 to 6 m




                                                                                                                                       Simulation




                                        ~ 6 to 9 m

                              Figure 2 - Hybrid simulation of infilled steel frames for UC Berkeley NEES Site

				
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