17-09-2012, 11:58 AM
STRENGTH AND PERFORMANCE OF FIBER-REINFORCED CONCRETE COMPOSITE SLABS
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ABSTRACT
The purpose of this research is to evaluate and compare the influence of four types
of secondary reinforcement on various component strengths related to composite slabs.
These components include the composite slab strength under uniform load, the strength of
two types of shear connectors used with composite beams and joists, composite slab
strength due to a concentrated load, and the flexural toughness and first-crack strength of
fiber-reinforced concrete using ASTM C1018 (1998) standard test. The performance of
the specimens reinforced with fibers are compared with that of the specimens reinforced
with welded-wire fabric (WWF), with the purpose of determining if fiber-reinforced
concrete can be used as an alternative to WWF.
INTRODUCTION
GENERAL
Today, the use of composite floor slab systems in steel framed buildings is
common practice. Among the numerous advantages over reinforced concrete slabs, are the
lightweight and the ease with which the steel deck is handled and erected. The deck also
takes the place of temporary formwork for the fresh concrete, which saves time and
reduces construction costs. Once the concrete has cured and the components become a
composite system, the cold-formed steel deck serves as positive slab reinforcement.
Even though the concept of composite slabs began in the 1920’s, the first
application to take advantage of this concept did not take place until the middle 1950’s. To
develop bond between the concrete and the steel deck, the first system utilized shear wires
welded directly onto the ribs of the steel section (Luttrell, 1995). The main problems
associated with this method were the expensive and time consuming welding process, and
that the decks couldn’t be “nested” for shipping purposes.
Embossments were added to the steel deck profiles in the 1960’s. In 1967, the
American Iron and Steel Institute (AISI) initiated a research project at Iowa State
University with the purpose of obtaining design criteria for composite slab systems.
Design criteria and specifications for composite slab systems were incorporated for the
first time in the ASCE “Specifications for the Design and Construction of Composite
Slabs” (ASCE 1992). The Steel Deck Institute (SDI) funded several research projects
thereafter. As a result of the new research, a new method was developed for determining
the strength of composite slabs, and was presented in the SDI “Composite Deck Design
Handbook” (CDDH) (Heagler et al. 1993).
OBJECTIVE:
The objective of this project is to evaluate and compare the influence of four types
of secondary reinforcement on various component strengths related to composite slabs.
These components include the composite slab strength under uniform load, the strength of
two types of shear connectors used with composite beams and joists, composite slab
strength due to a concentrated load, and the “Flexural Toughness and First Crack Strength
of fiber reinforced concrete” (ASTM C1018, Standards 1998). The relative serviceability
performance with respect to the control of shrinkage and temperature cracks is not
addressed in this work. The effect of the fibers in adhesion properties of the finished slab
or mechanical bonding between the concrete and the steel deck were not considered.
THESIS ORGANIZATION
Previous related research is presented in the Literature Review in Chapter 2. The
experimental research related to the composite slabs tested under uniform load conditions
is described in Chapter 3. This chapter also includes the analysis of the experimental
results for this set of tests and a description of the First Yield Method and the ASCE
Appendix D Alternate Method. The results and comparisons for the ASTM-C1018
“Standard Tests Method for Flexural Toughness and First-Crack Strength of Fiber-
Reinforced Concrete” are presented in Chapter 4. The experimental research and results
analysis of the composite slab specimens tested under concentrated and linear load conditions are presented in Chapter 5. Push-out tests experimental research, results and
analysis are presented in Chapter 6. Chapter 7 summarizes the results from all four sets of
tests. Conclusions and recommendations are also given in this chapter. The details of each
test specimen are provided in the appendices.