Abstract
This study evaluates the static and fatigue bond behavior in basalt fiber-reinforced polymer (BFRP) bars embedded in concrete. For bond behavior under a mono-tensile load, BFRP bars with four types of surface patterns (round, rectangular, cross-winding, and spiral-winding) were adopted, and 20 groups of rib parameters were introduced for round-type BFRP bars. The bond–slip relationships and the influences of the above parameters on bond behavior were investigated. An analytical model for simulating the relationships of full bond slip was studied by data fitting. For bond behavior under cyclic loads, the relationship between stress levels and the number of cycles was investigated, and the slip of round-ribbed BFRP bars was studied with respect to the number of cycles. The results showed that the rectangular, cross-winding, and spiral-winding ribbed bars experienced serious wear, and that the average bond strength was approximately 80.6% of that of the round-ribbed bars. Thus, the bond behavior of the round rib is superior to those of the other surfaces. In addition, a bond–slip constitutive model for a BFRP bar is proposed, representing four main stages: a micro-slip stage, a slip stage, a descending stage, and a residual stage. Under cyclic loads, an equation was proposed for predicting fatigue life with a regression coefficient of 0.880, and a development law of slip was characterized as three stages: the linear increase stage, the steady increase stage, and the sharp increase stage, respectively.
Highlights
Fiber-reinforced plastic (FRP) bars have been applied to concrete structures, as they exhibit a high strength-toweight ratio, are non-electromagnetic, and have excellent corrosion resistance (Wu et al 2007; Keller 2003)
Caro et al (2017) conducted experimental studies on the bonds of FRP bars with parameters of embedment length, FRP bar type and diameter, concrete compressive strength and hole diameter. They found that increase in bar diameter from 10 to 12 mm led to a 30.4% increase in the pull-out capacity and 9.2% decrease in the maximum average bond stress for the specimens with DE carbon fiber reinforced polymer (CFRP) bars
2.1 Parameters of Test Specimen For monotonic tests and cyclic tests, specimens adopt the same design characteristics based on the code of Japan, with an FRP bar with a diameter smaller than 17 mm, and with the side length of concrete cube specimen recommended to be set to 100 mm (Japan Society of Civil Engineering 1995)
Summary
Fiber-reinforced plastic (FRP) bars have been applied to concrete structures, as they exhibit a high strength-toweight ratio, are non-electromagnetic, and have excellent corrosion resistance (Wu et al 2007; Keller 2003). Malvar et al (2003) carried out tensile and bond tests for carbon fiber reinforced polymer (CFRP) rebars They found that bars with molded external deformations mimic those of steel rebar exhibited a bond strength of 10.1 MPa, bar with small deformation (0.0025 mm or 0.001 in high) was only 3.59 MPa. There is a primary need to explore more influencing factors and to develop constitutive laws for the BFRP bar, i.e., a new theory for the design of reinforced structures with BFRP bars needs to be developed For this purpose, a wide range of bond tests are performed to examine bond strength, slip, and different failure modes, to investigate how different types of rib parameters interact with concrete. Of local deformation, the decrease of stiffness, and early failure in practical engineering
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