Ultimate bending strength of RC beams made of high strength concrete

• Main Authors: Lim, Edrick Dan P., Uy, Erwin K., Yu, John David T.
• Format: text
• Language: English
• Published: Animo Repository 2009
• Online Access: https://animorepository.dlsu.edu.ph/etd_bachelors/12161
• Institution: De La Salle University

High strength concrete is widely used in the construction industry today especially in high-rise buildings because of its strength and its preferably low cost compared to other building materials. However, the structural codes being used in the Philippines were based from normal strength concrete therefore, it might not be applicable for high strength concrete. This research will study the flexural strength of high strength concrete beams using three theoretical models including the one found in the Code to determine which one is the most applicable. The flexural behavior of reinforced high strength concrete beams in yield stage was compared to the parabolic and exponential stress blocks, while in ultimate stage, parabolic, exponential and simplified rectangular stress blocks were compared. Twenty-five specimen were prepared for this study having a dimension of 150mm x 300mm x 1650mm (b x 1 xh). Two groups of beams having different reinforcement ratio with concrete strengths of 35, 55, 85 and 95 MPa were prepared for flexural tests. Flexural tests were done using the third-point loading. Stain gauges were attached to the steel reinforcement inside the beam to be able to monitor real-time strain data. The flexural behavior was evaluated for both the yielding and ultimate stage. The computed theoretical moment at yield using parabolic stress block resulted in moments larger than that of the experimental, while the exponential stress block resulted in moments smaller than the experimental. The ultimate moment from the three theoretical stress blocks produced moments smaller than that of the experiment indicating that they could be used in determining the ultimate bending strength of reinforced concrete beams.