Experimental and finite element studies on the behavior of hybrid reinforced concrete beams

This paper presents an experimental and numerical investigation on the behavior of reinforced concrete hybrid beams under two point load. Eight beams of dimensions (150x200x1300 mm) were cast and tested. The hybrid specimens contain of two layers, the upper layer (in the compression zone) made of self-compacted concrete (SCC) with compressive strength of approximately 75 MPa while the layer located in tension zone made of normal strength concrete (NSC) with compressive strength of approximately 30 MPa. These specimens were tested and compared with reference specimens made of SCC or NSC only. The main considered variables were: the SCC layer thickness in hybrid beams; and the effect of shear reinforcement on the total capacity of the tested beams. The test results showed that, using hybrid concrete in casting the reinforced beams has a significant effect in enhancing the general behavior of the specimens. The failure load increased by (18.2-54.5 %) in hybrid beams contained SCC by (25, 50 %) of the total beam height, respectively compared with corresponding reference specimens made of NSC only. It was also noticed that the use of shear reinforcement has an important role in increasing the total capacity of the specimens by about (35.3-38.5 %). ANSYS program (Version 15.0) was employed for modelling the specimens. The numerical results showed that, the general behaviour of the finite element models was in good agreement with the experimental data.