Abstract:
Reinforced concrete is used as construction material in every country. In many, including Bangladesh, reinforced concrete is a dominant structural material in engineered construction. The universal nature of reinforced concrete construction stems from the wide availability of reinforcing bars and the constituents of concrete, stones, sand, and cement, the relatively simple skills required in concrete construction, and the economy of the reinforced concrete compared to other forms of construction. Concrete is a relatively brittle material whose tensile strength is small compared with its compressive strength. This prevents its economical use in structural members that are subject to tension either entirely or over part of their cross section as in beams or in other flexural members.
To offset this limitation, It was found possible, in the second half of the nineteenths century, to use steel with its high tensile strength to Reinforce Concrete, chiefly in those places where its low tensile strength would limit the carrying capacity of the member. The reinforcement, usually round steel rods with appropriate surface deformations to provide interlocking, is placed in the forms in advance of the concrete. In more recent times, it has been found possible to produce steels, at relatively low cost, whose yield strength is 3 to 4 times and more that of ordinary reinforcing steels. This high-strength materials offer may advantages, including smaller member cross section, reduced dead load, and longer spans.
The Present study is aimed at finding out the variation of costing for a R.C building with different grades of steel (60 grades and 75 grades). To achieve the aim of this study a 20-Story height of structure has been selected. ETABS v9.0.4 version software has been used for analysis and design of various structural elements. BNBC-1993 load combinations have been followed. All structural elements of the building have been designed for same load combination. Auto CAD 2004 software has been used for reinforcement detailing and Microsoft excel 2007 software has been used for down various graph and calculation the quantity of required reinforcement.
Average reinforcement required for beams, columns, shear walls and in each square feet, has been calculated separately for two grades of steel. It is found that average reinforcement required per square feet this building is 2.35 kg and 2.13 kg for grade 60 (420 MPa) and grade 75 (520 MPa) respectively. It is observed that the result of the present study of a 20-storied residential building structure reinforcement cost 9.50% lower for using 75 grades (520 MPa) steel instead of 60 grades (420 MPa) steel of a same structure while concrete strength is same.
