Effect of different grades of concrete on rc framed multi-storied building

Due to the application of advanced material technology, concrete with high compressive strength is currently produced and used in many countries. This type of concrete can be produced by micro-silica and superplasticizers as well as applying good quality control procedures. The use of high-strength concrete (HSC) in building construction is becoming popular because it has many advantages such as increased strength and stiffness, reduced size of concrete sections, improved resistance to creep and drying shrinkage, and material durability. Therefore we can use high strength concrete (HSC) in columns and normal strength concrete (NSC) for beams & floor sections. Thus this study will investigate the performance of 8 storey tall buildings in ZoneIV for medium grade soil with varying high strength concrete (HSC) normal strength concrete (NSC) subjected to far-field ground motions scaled to collapse of the structure using varying grades (M20, M25, M30, M35, M40, and M50) of concrete strength subjected to seismic ground motions scaled to collapse of the structure using a linear static method and this will be achieved through analytical modeling and analysis using ETABS2018 software.


Introduction
As reinforced concrete frames respond to strong ground motion, it is likely that elements of the frame will have nonlinear behavior. The elements that yield may experience large deformations that contribute to increased localized story deformations in the frame. This is especially true when columns undergo inelastic deformations, as the drift at the story with yielding columns may magnify in part caused by the secondary effects of the axial loads. In addition, 1t is important to minimize the occurrence of yielding in concrete columns, especially near the base of the frame, because of difficulties encountered for detailing these elements for ductile response under high axial loads. If yielding in the columns can be eliminated, then the building will tend to respond with a stiff spine and drift will be evenly distributed over the height of the structure. This leads to smaller story drifts (the relative drift between two consecutive floor levels) and less subsequent damage in the lower portion of the frame where columns are subjected to high axial loads.

Significance of the study
All the structural elements in the buildings i.e. beams, columns & slabs are needed to resist all kinds of the loads acting on them. Even if a single column is failed in building that leads to a drastic effect in terms of life & economy, Although we design our building by taking strong column weak beam criteria (SCWB), In case of high rise buildings due to wind loads and in case of low rise & medium rise buildings due to earthquake loads plastic hinges may develop in the columns before the beams so that leads to failure of columns. Therefore by using different grades of concrete in reinforced concrete building frames we increase the axial, flexural & shear characteristics of columns to carry heavy loads coming from the surrounding beams and slabs.

Objective and scope of the work
The objective of the present study is to evaluate the effect of different grades of concrete criterion on Rc Frame (moment-resisting frame) building by using linear, nonlinear methods and quantify the economical, Storey displacements & Storey drifts as per IS codes. To determine displacement, inter-storey drifts of Rc Framed Structure for different grades of concrete. The study will investigate the performance of tall buildings with varying grades of concrete strength subjected to seismic ground motions scaled to collapse of the structure using a linear dynamic analysis approach and This will be achieved through analytical modeling and analyses using ETABS software. The scope of the project is limited to reinforced concrete framed structures designed for dead loads (DL), live loads (LL), wind loads (WL) & seismic loads (EL). The structure is evaluated in accordance with the codal provisions. The analysis is done for 8 storey structure and is analyzed for different grades of concrete for beams and columns. The same building is analyzed and designed for different values of concrete strengths M20, M25, M30, M40, M50.

Structural Modelling
The building is evaluated and modeled using ETABS2017. The structural components are modeled taking into consideration the various aspects of the building details. Common elements in reinforcedconcrete construction include frames i.e. beams and columns. The building models are generated in the integrated building analysis and design software ETABS 2017. Beams and columns are modeled using three-dimensional (3D) frame elements, while the slabs are defined as rigid diaphragms. The cracked section properties of both beams and columns are taken from practical field cross-sections used in India. Both dead and live loads and wind loads are assigned to the building models according to IS

Results and discussions
By using different grades of concrete in 8 storey framed buildings we can conclude that when the grade of concrete increases in the columns there is a decrease in cross-section sizes & lateral storey displacements. EQX*-Siesmic force in X-direction, EQY#-Siesmic force in Y-direction

Conclusions
We can see there is a significant reduction in terms of lateral storey displacements and cross-sectional sizes.
If we compare the results of M25 C230x600 with the M50 C230x525 case there is a significant reduction in cross-section size for an approximate equivalent lateral displacement. Further, we can calculate the economic value of the reduction of cross-section sizes with varying different grades of concrete.