1,721,016 research outputs found
Effect of Bond-Slip on the Crack Bridging Capacity of Steel Fibers in Cement-Based Composites
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Multiple cracking and strain hardening in fiber-reinforced concrete under uniaxial tension
No full textFiber-reinforced concrete (FRC) showing strain hardening after cracking is commonly defined as High Performance Fiber Reinforced Cementitious Composite (HPFRCC). In the post cracking stage, several cracks develop before complete failure,which occurs when tensile strains localize in one of the formed cracks. As iswell known,multiple cracking and strain hardening can be achieved in cement-based specimens subjected to uniaxial tension by increasing the volume fraction of steel fibers with hooked ends, or by using plastic fibers with and
without steel fibers, or bymeans of high bond steel fibers (e.g., twisted fibers or cords). To better understandwhy,
in such situations, highmechanical performances are obtained, an analyticalmodel is herein proposed. It is based
on a cohesive interface analysis,which has been largely adopted to investigate themechanical response of FRC or the snubbing effects produced by inclined fibers, but not the condition ofmultiple cracking and strain hardening ofHPFRCC. Through this approach, all the phenomena that affect the post-cracking response of FRC are evidenced, such as the nonlinear fracture mechanics of the matrix, the bond–slip behaviour between fibers andmatrix, and the elastic response of both materials. The model, capable of predicting the average distance between cracks as
measured in some experimental campaigns, leads to a new design criterion for HPFRCC and can eventually be used to enhance the performances of cement-based composites
Equivalent Confinement in HPFRCC Columns Measured by Triaxial Test
No full textThe ductility of high-performance fiber-reinforced cementitious concrete (HPFRCC) can be developed not only in tension but also in compression. This aspect is evidenced in the present paper by comparing the behavior of HPFRCC cylindrical specimens under uniaxial compression, with the mechanical response of normal vibrated concrete (NC) and self-consolidating concrete (SCC) subjected to triaxial compression. The ductility of all the cement- based composites is computed through a nondimensional function that relates the inelastic displacement and the relative stress during softening. In the case of NC and SCC specimens, the results show that increasing the confining pressure results in an increase in fracture toughness. Conversely, the tests on HPFRCC specimens show that, even in the absence of confinement, HPFRCC can achieve practically the same ductility observed in normal and self- consolidating concretes with 1 MPa (0.15 ksi) of confining pressure. Thus, the presence of HPFRCC in compressed columns is sufficient to create an active distributed confinemen
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