Analytical Practices to Obtain Efficient Concrete Grade in Outrigger Walls below Plinth Level in Multistorey Building

— To make the structure that would be free from lateral effects, some of the additional components should be implemented to it to make it safe. Some of the supplementary components are shear wall, bracing elements, belt supported system, outrigger wall system etc. These supplementary components when added to the multistoried fascinating and high rise structure can make it stiffer that ultimately fulfill the living needs. These add-ons make the structure safer for various horizontal and vertical irregularities. In this study outrigger system is taken for analysis by implementing the outrigger walls below the plinth level. Previous studies shows the outrigger system used at a particular height, but none of the researches shows this kind of the structural stability research approach. The main objective of the current theme is to prove the optimum grade of concrete that can be used when this kind of approach is adopted. Total 8 cases were selected, analyzed and compared among each other to select the optimum one. Building case OT8 observed and obtained as efficient case and should be recommended when this type of stability in building will be provided.


INTRODUCTION TO STABILITY ENHANCEMENT CRITERIA
The tall structures needs firm stable ground to achieve lateral stability with lesser ground area for living and commercial purposes. The stabilization of the structure has done when using the current guidelines of the Indian Standardization. The dual structural configurations are now the main criteria for current tall structures. Since the construction an industry expand day by day and follows the financial customs that operates cost effective structures.
The only view in this industry matter is financial along with reallocation and liquidity of funds for operation and maintenance of the construction. With this financial operation in this industry, structural engineers needs to do a very tough task to make the stability of the structures at each part or at each stages when design steps has going on. When construction work on site is going on, it sometimes loses the financial trend when the structural stability is there to make the structure heavy that sustain the hazardous seismic activities.
To make the structure more sustainable in these seismic activities, some supplementary stiffening structural members are needed like heavy weight R. C. C. components, belt supported systems, outrigger systems, dual structural systems, truss belt systems etc. These supplementary components on one hand, it stabilizes the structure more effectively, but on the other hand, it increases the mass of the structure that ultimately increases the base shear. Hence it is essential to make the structure more light and stable, subsequently it lessen the financial trend in the project.
As per the generalized theory of stability, many research activities are going on numerous researches done in this field established many things in terms of stability of the structure by means of and without adding the supplementary components. Practices that stability escalates could be achieved by:-1. By implementing some stability improvement structural components that resist the lateral and vertical loads.
2. Altering the size of the structural elements. 4. By decreasing the bulkiness of the structure.
5. By changing the grade of concrete in overall or in the part of the structure.

II. OBJECTIVES OF THE CURRENT STUDY
The current study consists of providing the outrigger wall system below the plinth level to increase the lateral load handling capacity in multistoried building. A complete analytical procedure has followed to obtain the each parametric result, compared among all eight cases to obtain most efficient case. As per Indian standard under earthquake Zone III, the following objectives selected in this study:- 10. To analyze the maximum nodal displacement case in X direction with most efficient case that provides more stability among others. 11. To obtain the maximum nodal displacement values in Z direction with most efficient case among all eight cases.
12. To demonstrate and recommend the efficiency of wall belt below plinth level with optimum concrete grade to stabilize the structure.

III. PROCEDURE AND 3D MODELING OF THE STRUCTURE
A semi commercial (G+16) storied apartment is supposed to be situated at seismic zone III and rested on medium soil. This apartment has both vertical load along with horizontal loads acting over it and this seismic load creates the maximum deflection at the top of the structure. With 900 sq. m. area, Dimensions and different input parameters of the building are selected and applied over the structure and then seismic load is applied over it with various seismic parameters as mentioned in Table 1 and Table 2 respectively.
For the analysis of the optimum grade of outrigger, a total of eight different cases have chosen for the parametric analysis, its description shown below. Dead loads, Live loads, Response spectrum loads and load combinations as per Indian Standards are applied on the apartment. M20, M25, M30, M35, M40, M45 and M50 grade of concrete used with Fe 500 grade of steel is used. Figure 4 shows typical floor plan of the apartment, its front view without wall outrigger at plinth, with wall outrigger at plinth and finally last figure shows the description of different components of apartment with Wall Outrigger below plinth level.   Graphical representation of each result parameters has discussed as per different wall outrigger case shown below:- Observing all the parameters, after the application of Outrigger Wall provided below plinth level, the Building case OT8 observed and obtained as efficient case and should be recommended when this type of stability in building will be provided.

ACKNOWLEDGEMENT
I would like to thank Mr. Sagar Jamle, Assistant Professor, Department of Civil Engineering, Oriental University, Indore for his continuous support and guidance for the completion of this entire work. I am glad that he simultaneously works with a batch of 12 research scholars and do support individual scholars intensively.