Torsional behavior model of steel-fiber-reinforced concrete members modifying fixed-angle softened-truss model

Consideration on punching shear strength of steel-fiber-reinforced concrete slabs

“…In the proposed model, the shear contribution of the uncracked concrete in the compression zone comes from the plasticity model of concrete and the concept of equivalent shear stress block, and the shear contribution of the steel fibers is determined by the direct tensile force transfer model (DTFTM), which considers the bond behavior of steel fibers and the pull-out failure mechanism. [23][24][25][26] The proposed model is also verified by comparing with the test results of SFRC slab-column connections collected from the literature. 1,[11][12][13][14]16,[27][28][29][30][31] In addition, the relation between the shear contribution of the undamaged concrete in the compression zone and that of the steel fibers in the tensile zone is also discussed in detail.…”

“…As shown in Figure 7(b), the bond factor (r f ) was set to 1.0, 0.75, and 0.5 for hook-shaped, crimp-type, and straight-type fibers to consider the differences in the maximum bond strengths of the steel fibers. [23][24][25][26] Because it is difficult to accurately determine the effective embedded length of the steel fibers at the crack surface, the average bond length is assumed to be one-fourth of the fiber length in the DTFTM, 23,24 as shown in Figure 7(c). The surface area of a steel fiber (A fp ) at the crack surface can then be expressed as follows…”

Fixed-Angle Smeared-Truss Approach with Direct Tension Force Transfer Model for Torsional Behavior of Steel Fiber-Reinforced Concrete Members

“…3(a), the strain gradients within the thin-walled element in the d-r directions are assumed to be linear, and those in the crack directions (2-1) are also assumed to be linear (Hsu 1984, Ju et al 2013. Then, the relationship between the average strain ( 2 ε or 1 ε ) of element A within the effective depth of the shear flow zone ( d t ) and the maximum strain ( 2s ε or 1s ε ) at the extreme fiber of the thin-walled tube can be obtained, and the effective thickness of the shear flow zone ( d t ) can be expressed in a simple closed form (Jeng and Hsu 2009).…”

“…The analytical models for torsional behavior of SFRC members presented in existing studies (Gunneswara Rao and Rama Seshu 2005;Masur et al 1989;Karayannis 2000a;Mansur and Paramasivam 1982;Craig et al 1984;Ju et al 2013), have mostly adopted the macroscopic approach, and as afore-mentioned, they requires massive experimental efforts because a large number of biaxial shear tests is essentially necessary to determine the constitutive equations of composite material in tension or shear. It is also difficult to evaluate the interaction behavior between concrete and steel fibers at the crack interfaces quantitatively in such macroscopic models.…”

“…It is also difficult to evaluate the interaction behavior between concrete and steel fibers at the crack interfaces quantitatively in such macroscopic models. For the analysis of torsional behavior of SFRC members, many influential factors should be taken into account (Gunneswara Rao and Rama Seshu 2005;Masur et al 1989;Karayannis 2000a;Mansur and Paramasivam 1982;Craig et al 1984;Ju et al 2013). The deformation compatibility and three-dimensional force equilibrium considering the strain gradient within the shear flow zone should be properly established, reflecting complex stress transfer mechanisms such as the bond action between fibers and surrounding concrete, the fiber tensile behavior Kim et al 2012;Lim et al 1987b), and the fiber directionality (Romualdi and Mandel 1964;Soroushian and Lee 1988;Lim et al 1987), in addition to the aggregate interlocking at the crack interface (or interface shear transfer) (Collins and Mitchell 1991) and dowel action of reinforcements (Swamy and Bahia 1979).…”