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TECHNICAL PAPER

1600 40
Load-carrying capacity First rupture Lowest prestressing tendon (1) FEM (1) Present approach
120 Second rupture Second prestressing tendon (2) FEM (2) Present approach
FEM (3)
Bottom non-prestressing tendons (3)
Present approach
Third 1200 Extreme compressionfiber (c) FEM 30
rupture
Load (kN) 80 Cracking load Tensile stress in tendons (MPa) 800 First Second Third 20 Compressive stress in concrete (MPa)
rupture
rupture
rupture
40
Present approach 400 10
Experimental, B-1
Finite element (FE) analysis
0 0 0
0 10 20 30 0 10 20 30
Deflection (mm) Deflection (mm)
(a) (b)
Figure 10: (a) Load-deflection curves obtained from different approaches and
(b) Variation in tensile and compressive stresses in the tendons and concrete with deflection
The results obtained from the finite element (FE) analysis are 1. The load-carrying capacity of the BFRP-prestressed
compared with the analytical results obtained using the present concrete beam, estimated based on the unified design
design approach and the experimental findings. The load- approach, is in a good agreement with that using the
deflection responses obtained from the different approaches strain compatibility method. Moreover, the theoretical
are shown in Figure 10(a). The results of the finite element estimations of the load-carrying capacity, following both
(FE) analysis show the failure of the beam in three stages, as the analytical approaches, are in agreement with the
anticipated in the present design approach, and the peak experimental findings.
loads with the corresponding deflection are found in a good
agreement with the results of the present design approach with 2. The load-deflection response of the BFRP-PSC beam,
maximum differences of 10.7% and 21.4% for the peak loads analytically obtained from the flexural design approach
and deflections, respectively. However, the load-deflection adopted, is in a good agreement with the experimental
responses obtained from the present design approach as well findings for the pre-failure zone; however, the estimation
as the finite element (FE) analysis are not matching well with of deflection, using this approach, deviated from the
the experimentally measured counterparts in the post-peak experimental findings in the post-peak zone, though, the
stage, which can be attributed to the uncertainties in material additional inelastic energy (area under the load-deflection
properties and prestress losses. Figure 10(b) shows the variation curve in the post-peak zone) is in a close agreement
in tensile stress in the tendons and compressive stress in the with the experimental results. Consequently, the ductility
extreme compression concrete fiber with deflection of the beam. evaluated from the presented design approach is
The sequential rupturing of the BFRP tendons can be seen from comparable owing to the successive/ progressive ruptures
Figure 10(b), wherein the deflection values corresponding to the of the BFRP tendons imparting higher nonlinearity.
three ruptures of the tendons are matching with the deflection 3. The partial prestressing of the concrete beam, designed
values at the load drops in the FE load-deflection curve in as an under-reinforced section, with two layers of the
Figure 10(a). This testifies that the tendons did not rupture BFRP tendons, vertically distributed along the depth of
simultaneously in the design approach adopted here, instead, the cross-section, resulted in a high energy ratio reached
the sequential rupturing of the BFRP tendons imparted higher to 89.6% and achieved an acceptable ductile behavior.
nonlinearity in the flexural member, thereby enhancing the Hence, the under-reinforced design can be recommended
energy ratio, i.e., ductility. for the structural members partially prestressed with the
BFRP tendons following the presented design approach.
6. CONCLUSIONS
4. The finite element (FE) simulation results are found in a
Basalt fiber-reinforced polymer (BFRP)-prestressed concrete good agreement with the results obtained from the current
(PSC) beams were designed based on the analytical approach, design approach, and showed the sequential rupturing of
analyzed numerically, and tested experimentally. The flexural the BFRP tendons, as intended in the design philosophy,
behavior of the BFRP-PSC beams was investigated when the in the post-peak zone. It therefore proved the efficacy of
beams were under-reinforced, particularly from viewpoint of the philosophy of the current flexural design by providing
ductility achieved. The conclusions drawn from the present study more ductility to the beam and introducing a kind of
are as follows. progressive failure.

26 THE INDIAN CONCRETE JOURNAL | JANUARY 2021