Time Dependent Behaviour of High Strength Concrete Beams

Abstract

Over the past several years, development in structural materials such as prestressed concrete and the use of high-strength steel, and the use of methods of design such as ultimate strength, have led to a progressive increase in the strength of the concrete used in structures. Therefore, interest in high-strength concrete has increased greatly.

The substitution of High-Strength-Concrete for the Normal-Strength­ Concrete might significantly reduce the cost. In addition, the amount of compressive steel reinforcement might be substantially reduced. Reduction in span-to-depth ratio might also be possible in long-span reinforced and prestressed concrete.

With the continuous development in concrete as a primary construction material and with the recent development of the production of High-Strength­ Concrete (H-S-C), a natural tendency would be to exploit a higher proportion of the strength of the concrete. Therefore, it is important to know the behaviour of High­ Strength-Concrete under stress and sustained loads above the ordinary normal working stress. Most of the previous studies on the time-dependent-deflection were carried out at low stress levels compared to the short-term ultimate of the normal concrete. In this research High-Strength-Concrete beams with three compressive strengths were tested under different percentages of sustained ultimate loads, and different percentages of compression reinforcement, for long period of time.