Behaviour of steel fiber reinforced high strength self-compacting concrete beams under combined bending and torsion

This paper investigates experimentally and analytically the behavior of steel fiber reinforced high strength self-compacting concrete beams under combined bending and torsion. In the recent decades, steel fiber reinforced high strength self-compacting concrete (SFHSSCC) is considered a very important material in the structural engineering field. High strength concrete attracts designers and architects as it offers good durability and the esthetics of a construction as well. One of the advantages using the SFHSSCC is to provide high ductile behavior. SFHSSCC has also a high toughness, with improvement in workability, and high residual strengths after the initiation of the first crack. The main challenge in many past studies is to select the effective fiber contents that should be added to the concrete mixture. In the present study, a Hooked shape steel fibers are used; the hooked steel fibers were evaluated using the volume fractions, which varied between 0.0%, 0.75% and 1.5%. A total of six beams were tested, and classified into three groups. The beam shapes are chosen to create the torsional and bending moments simultaneously. All beams, have 200 cm length, a cross section of (10 × 20) cm, longitudinal bottom steel reinforcement of 3Φ10, longitudinal top steel reinforcement of 2Φ10, additional longitudinal steel 1Φ8 placed in the mid height of the cross sections, and closed stirrups of 10Φ8/m. The first group is considered as a reference group consisting of a beam casted from conventional normal weight concrete. The second group is consisted of two beams casted from self- compacting concrete, the first beam in the second group was casted without steel fibers and the second beam was casted with steel fibers volume fraction equal to 0.75%. The third group is consisted of three beams that were casted from high strength self- compacting concrete (HSCC) with steel fiber volume fractions equal to 0.0%, 0.75% and 1.5% respectively. The experimental results were validated using finite element analysis. It is concluded that the effect of steel fiber reinforced high strength self- compacting concrete (SFHSSCC) enhances the behavior of beams under combined bending and torsion.