r - The Hong Kong Polytechnic University

EXPERIMENTAL PROGRAMS
Materials and Mix Proportion
The cementitious materials used in this study were ASTM Type III Portland cement and class C fly ash. The
coarse aggregate had a maximum size of 12.7 mm and consisted of solid crushed limestone from a local source,
with a density of about 2.70 g/cm 3 . The fine aggregate was #16 flint silica sand (ASTM 50-70).
polycarboxylate-based superplasticizer (SP) was used to achieve desired workability. In addition to the SP, a
viscosity modifying admixture (VMA) was also used to enhance the viscosity and avoid fiber segregation. This
mixture has 1.5% volume fraction of hooked steel fiber with circular cross-section was used with tensile
strength of 2300MPa and aspect ratio of 79 (diameter= 0.38mm and length= 30mm). Average 28-day
compressive strength based on 100×200 mm cylinders is approximately 40 MPa. Details of matrix composition
are given in Tables 1.
Cement
Table 1 Relative composition of SCHPFRC mixture by weight and compressive strength
Fly
Ash
Sand
Coarse
Aggregate
Superplasticizer
f ¢
Water VMA Steel Fiber c
(MPa)
1.0 0.875 2.2 1.2 0.005 0.8 0.038 0.315 40
Specimen Geometry and Test Setup
A 890×890×70 mm concrete panel was fabricated for the shear panel test. Figure 2 illustrates the geometry and
reinforcement layout of the panel. In order to provide an adequate post-cracking resistance of the panel, forty D6
deformed wires were provided for the x-direction reinforcement, giving a total reinforcement area of 1543 mm²,
which equated to a reinforcement ratio of 2.47%.
5/16" Threaded Rod
D6 Bars
ρ x= 2.47%
Pure Shear
Pure Shear
70
70
εy
εh
εv
εx
890
890
Pure Shear
Pure Shear
Y
X
Unit: mm
Figure 2 Dimension, reinforcement layout and LVDT setup of panel
This in-plane pure shear panel test was conducted by using the Panel Tester Machine developed by Vecchio
(1979, 1982) at the University of Toronto. This machine and experimental setup were designed to apply various
in-plane loading conditions to a concrete panel. The in-plane shear forces are generated by the horizontal and
vertical jacks on each opposing side of the panel. There are adjustable links on the frame to prevent out-of-plane
displacement and keep the panel aligned. Deformations (strains) of the panel were obtained continuously from
the LVDTs and strain gauges throughout the duration of each test. Additional data were also obtained from
Zurich gauge readings that were taken at each load stage to verify the accuracy of LVDT. These data were
subsequently analysed to investigate the response characteristics of the concrete panels under in-plane pure
shear loading.
RESULTS AND DISCUSSIONS
The shear stress-shear strain response of SCHPFRC panel is plotted in Figure 3. The behavior kept linear up to
first cracking at the shear stress of 1.5 MPa. The panel failure occurred at a maximum shear stress of 4.3MPa
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