Description
Construction of slabs in areas with weak soil conditions has commonly used pile-supported slab structural design so that the adverse effects of soil-structure interaction in terms of differential settlement, cracking, or long-term serviceability problems are avoided. In this application, the construction of slabs on closely spaced pile caps (typical span-depth ratios between 8 and 30) is referred to as elevated ground slabs (EGSs). These slabs may be subjected to moderately high loading, such as concentrated point loading of up to 44 kip (150 kN) and uniformly distributed loadings of 1000 lb/ft2 (50 kN/m2). The dynamic loadings may be due to moving loads such as forklifts, travel lifts, and other material handling equipment. Fiber-reinforced concrete (FRC) has been successfully used to address the structural design of these slabs. Based on the knowledge gained, the area has been extended to a construction practice for slabs supported by columns as well. Applications are further extended to multi-story building applications. This report addresses the methodology for analysis, design, and construction of steel FRC (SFRC) slabs supported on piles or columns (also called elevated SFRC [E-SFRC]). Sections of the report address the history, practice, applications, material testing, full-scale testing, and certifications. By compiling the practice and knowledge in the analysis design with FRC materials, the steps in the design approach based on ultimate strength approach using two-way slab mechanisms are presented. The behavior of a two-way system may not require the flexural strength of conventional reinforced concrete (RC) because of redistribution, redundancy, and failure mechanisms. Methods of construction, curing, and full-scale testing of slabs are also presented. A high dosage of deformed steel fibers (85 to 170 lb/yd3 [50 to 100 kg/m3]) is recommended as the primary method of reinforcement. Procedures for obtaining material properties from round panel tests and flexural tests are addressed, and finite element models for structural analysis of the slabs are discussed. Results of several full-scale testing procedures that are used for validation of the methods proposed are also presented.
Keywords: ductility; durability; fiber-reinforced cement-based materials; fibers; flexural strength; jointless slab; moment-curvature response; plastic shrinkage; reinforcing materials; shrinkage; shrinkage cracking; slab-onground; slab-on-piles; steel fibers; steel fiber-reinforced concrete; toughness; yield line analysis.
Table of Contents
CHAPTER 1—INTRODUCTION
1.1—Introduction
1.2—Scope
CHAPTER 2—NOTATION AND DEFINITIONS
2.1—Notation
2.2—Definitions
CHAPTER 3—HISTORICAL DEVELOPMENT OF SLABS-ON-GROUND AND ELEVATED STEEL FIBER-REINFORCED CONCRETE SLAB SYSTEMS
3.1—Historical background
3.2—Advantages of G-SFRC and E-SFRC slab systems
CHAPTER 4—CURRENT DESIGN METHODS AND CONSTRUCTION PRACTICES
4.1—Introduction
4.2—Existing standards and design methodologies
4.3—Slab dimensioning, fiber dosage rate, and typical loading conditions
4.4—Additional construction provisions
4.5—Limitations and areas of needed research
CHAPTER 5—MATERIAL AND STRUCTURAL DUCTILITY
5.1—Introduction
5.2—Material ductility
5.3—Structural ductility
5.4—Two-way slab mechanism
5.5—Test methods applicable to design
CHAPTER 6—DESIGN GUIDES FOR TENSILE STRAIN SOFTENING, DEFLECTION HARDENING MATERIALS
6.1—Structural analysis
6.2—Approaches to evaluate nominal flexural strength of E-SFRC slabs
6.3—Design of E-SFRC based on yield-line theory applied to slabs
6.4—Evaluation of load capacity of E-SFRC slabs
6.5—Examples
CHAPTER 7—FULL-SCALE TESTING OF ELEVATED SLABS
7.1—Full-scale elevated slab testing program available test results
7.2—Test program
7.3—Discussion of full-scale structural tests
7.4—Comparison of experimental load capacity and model computed values
7.5—Design verification numerical examples
7.6—Verification of punching shear of piles
CHAPTER 8—REFERENCES
Authored references
APPENDIXES