الفهرس 
Disadvantages of using HSC and UHSC:Only 14 pages are availabe for public view
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Abstract
Due to technological development, advance in tall buildings’ construction and more frequent use of prestressed concrete in buildings and bridges, the demand for the use of High and Ultra High Strength Concrete (HSC and UHSC respectively) used in reinforced concrete structures has increased rapidly. For example, in building design using higher concrete strength lead to significant reduction in the dimensions of concrete members, which helped increasing spans and the construction of taller and lighter buildings. Also, in design of bridges, the use of UHSC is very useful in decreasing the number of girders required as well as reducing their depth with increased spans.
Design of reinforced concrete elements mainly depends on the characterestics of the equivlant compressive stress block subjected to combined flexural and compressive stresses. This research is based on determining the design parameters of the equivalent compressive stress block for ultra high strength concrete having strength higher than 60MPa, as such parameters are not well defined compared to those used for Normal Strength Concrete (NSC).
Seven C-bracket concrete specimens were tested under combined flexure and compression stresses to determine the realistic stress distribution at the compression zone of ultra high strength concrete members. The main variable was the concrete compressive strength for each specimen. Equivalent rectangular stress block parameters as well as the ultimate compressive strain for those members were obtained from experimental investigations & compared to those defined in major international design codes.
The values of the equivalent rectangular stress block parameters changes with the increase in the concrete compressive strength. The stress-strain relationship for HSC and UHSC obtained from tested specimens indicated that the ascending branch is more linear when compared to NSC. Also, the failure of HSC and UHSC became more brittle than NSC in a more explosive manner.