Study Behavior of Hollow Reinforced Concrete Beams

The concept of opening or hollow in the structure elements is made to meet the architectural demands through passing mechanical or electrical runs, in addition creating reduction in weight and savings in materials. This concept done by installing circular PVC pipe in tension zone of reinforced concrete beams as concrete below the neutral axis acts as a stress transfer medium between compression and tension zone. A total of 10 reinforced concrete beams of size 2500mm x 200mm x 300mm were casted and tested by four point bending test. The results such as crack load, ultimate load, crack pattern, failure modes, loads deflection curves, stiffness, ductility index and absorbed energy for all tested beams were studied. The test results indicated that, the pipe diameter less than 0.25 width of under or over reinforced beams their center at two investigated location (0.53*d) and (0.60*d) had no effect on the capacity and stiffness of beam. For larger pipe diameter, the ultimate capacity of beams depend on its location and flexural and shear reinforcement ratio, crack width of beams with inserted PVC pipe were wider and failure modes were brittle diagonal shear failure. Analytical study is carried out using ANSYS 14.5 program and the maximum difference in predicting failure load is about 19.00% so the use of computer software to model these beams is much faster and saving cost.