Ductility of graded concrete beams on different cross-sectional dimension ratio and steel reinforcement ratio

Abstract

Innovation in construction materials continues to grow from year to year. Graded concrete (GC) is a novelty in construction materials designed by combining two different concrete strength in one element. The potential use of GC applied as construction materials in the future makes the researcher intend to review the ductility on various cross-sectional dimension ratios and reinforcement ratios. Ductility is one of the essential characteristics in designing modern structures because it prevents brittle failure due to loading. Furthermore, it ensures the safety of the structural system due to dynamic loads caused by the earthquake. The importance of ductility in a structural system makes it necessary to conduct further investigations on GC beams. The GC beam is composed of two concrete mixes with different strength, namely 40 MPa in compression fibre and 20 MPa in tensile fibre. The beam specimen uses a cross-sectional dimension ratio of 2/3 and 1/2 with a minimum and maximum reinforcement ratio. The GC beam specimen is designed with a shear span of 2.5 and the transversal reinforcement is only installed in the support area. The beam specimens were tested at the age of 28 days with a four-point bending setup. The results demonstrated that the change in the ratio of the cross-sectional dimensions from 2/3 to 1/2 can increase the ductility of the GC beam by more than 200%. The use of a larger reinforcement ratio increases the ductility of the GC beam exceeds 100%. The increase in the ductility of the GC beam provides more resistance to the building during an earthquake. Ductility will make a structure able to maintain its strength and stiffness so that it will not collapse even though it has exceeded the designed safety limit.