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ABSTRACT
It is important to identify the first concrete crack load in order to fulfill early diagnosis and to satisfy early warning of a dangerous scenario. In this study, a model for predicting the first crack load on hollow-cored rectangular beam point loaded at midspan was developed combining a Numerical method and experimental approach. The Modulus of Rupture was introduced into the governing moment curvature relation since it defines the point at which the first crack begins. Experimentally, Flexural testing with point loads at mid-span were performed on fifteen (15) beams made up of three (3) beam types at 1KN interval over a span of 750mm using the Universal Testing machine. The beams were simply supported by roller points. The dimensions of the beams were kept constant and varied while the following hollow diameters were investigated; 0, 30, 60,75 and 105mm. Numerically ,the beam was designed as a beam element point loaded at midspan with varied width(b) and depth(h) and a span of 750mm and the support conditions were defined as pinned support. Governing equations relating failure load with modulus of rupture, stiffness matrix, shape functions, and moment of inertia were developed. The equation for predicting the first crack load relating the First crack load with the modulus of rupture were derived. The moment of inertia was calculated by discretizing the Hollow-Cored Beam section using Isoparametric geometric transformation.
