K L Rakshith, Smitha, International Journal of Advance Research, Ideas and Innovations in Technology.

ISSN: 2454-132X Impact factor: 4.295 (Volume3, Issue4) Available online at www.ijariit.com Effect of Bracings on Multistored RCC Frame Structure under Dynamic Loading Rakshith K L Department of Civil Engineering Sahyadri College Of Engineering And Management, Mangalore rakshithkl29@gmail.com Smitha Department Of Civil Engineering Sahyadri College Of Engineering And Management, Mangalore smitha.civil@sahyadri.edu.in Abstract Braced frames are known to be efficient structural systems for buildings under high lateral loads such as seismic or wind loadings. The potential advantage of bracing system is that it is comparatively small increase in mass associated with the retrofitting scheme since this is a great problem for several retrofitting techniques. In this study building modelling is done for regular and vertical irregular building with and without bracing system. Response spectrum analysis is done for each model with different types of bracings. The results in terms of displacement, storey drift, storey shear of regular and irregular structure is compared. Keywords Bracings, Response spectrum, Storey drift, Base shear I. INTRODUCTION The resistance to lateral load from wind and earthquake is the reason for the evolution of bracing. From design of earthquake resistant structure has several changes and improvement in the structure is found. A study of earthquake engineering calls for good kind of geophysical procedure that causes earthquake. Seismology is the study of the generation, transmission and measurement of seismic waves by the means of earth and the sources that stimulate them. The study of seismic wave distribution through earth provides the greatest effort to the understanding of the interior structure of earth. Seismic analysis is a part of structural analysis and in computation of reaction due to earthquake. It is also the process design of structural elements and also in the retrofitting of the region where earthquake is more common. From the application of bracing which increase the seismic behavior of structure and improves the stiffness and capacity of the building. In braced frame structures the load is transferred from frame to the braces. Bracings also increase the strength by avoiding weak columns. These braces are resistant against the wind load and the seismic forces. It is necessary to provide bracing to improve the strength of the structures. The different types of bracings such as inverted V bracings, X bracings etc are commonly used. Steel bracing system is one of the effective measures for resisting the horizontal forces like seismic and wind forces in reinforced concrete multistorey buildings. Bracing members are subjected to tension and compression; subsequently they are provided to take these forces. Steel bracing framework expands the stiffness and strength of the RC multistory building and reduces their deformation. Bracings improves the stiffness of structure also reduces the displacements, drifts etc. These braced frame structures increase tensile and compressive of the building. Also braced frames also resist the wind load and seismic forces. The bending moments in the column is reduced. Braced are most commonly used in construction, also it is being economical. These bracings are economical which is easy to place. These bracing improves stability and resists lateral loads. Beams and columns are designed for vertical load in braced construction. Beams and column are arranged in orthogonal manner in multistored frame structure. To provide resistance the to horizontal force acting.. There are two types of bracings. Vertical bracing which provides load pattern to transmit the horizontal load from ground level and to provide great stability. Horizontal bracing which transmit the horizontal force to the plane of vertical bracing, which provides resistance to horizontal force. These bracings are provided at each floor level. 2017, www.ijariit.com All Rights Reserved Page 696

II. OBJECTIVES To study the seismic performance of RCC frame structures with different type of bracings under dynamic loading. Also results in terms of displacement, storey drift, base shear are found out. III. MODELLING In this study RCC framed building having an area of 25m X 20m and height 30m with all supports are fixed. The analysis is done by ETABS software according to Indian Standard codes. In this study, twelve models of RCC frame structure having G+9 floors with different bracing types for both regular and irregular structures, were selected in order to determine the behaviour of structural steel during seismic activity in seismic zones, zone III and zone V. The columns are fixed at the ground and are taken as restrains. The building height is 30m with storey height 3m in base as well as typical structure respectively. Table 1: Model types `Sl.no Regular Building Irregular Building 1 Regular bare frame Irregular bare frame 2 X Bracing X Bracing 3 Inverted V Bracing Inverted V Bracings 4 V Bracings V Bracings 5 Eccentric forward bracing Eccentric forward bracing 6 Eccentric backward bracing Eccentric backward bracing Table 2: Model description Sl.no Model Description 1 Zones III 2 Zone factor 0.16 3 Importance factor 1 4 Response reduction factor 5 5 Structure height 30m 6 Soil Condition Medium 7 Damping Ratio 5% 8 Floor Finish 1.0 KN/m 2 9 Live Load 4.0 KN/m 2 10 Density of Steel 78.50 KN/m 3 Sl.no Table 3: Material properties Material Properties 1 Column 230x600mm 2 Beam 230x450mm 3 Bracing ISMB 250 4 Thickness of Slab 250mm 5 Grade of Steel Fe 250 6 Distance in X-Direction (Length) 25m 7 Distance in Y-Direction (Width) 20m 8 Distance in Z-Direction (Height) 30m 9 Floor to Floor Height 3m 10 Spacing of Beams 5m 2017, www.ijariit.com All Rights Reserved Page 697

Fig 1: Plan of building model for regular and irregular structure 2017, www.ijariit.com All Rights Reserved Page 698

Fig 2: Elevation of regular and irregular frame model IV. RESULTS AND DISSCUSSION Seismic analysis of RCC frame building for both regular and irregular building is carried out for the analysis. Both the buildings, regular as well as irregular is analysed with bracing frame and by applying different types of bracings, the results are tabulated such as, Maximum storey displacement, Maximum storey drift and storey shear is noted. A. Results for regular structure 1) Displacement in X and Y direction Table 4: Displacement results `Serial no Bracings Displacement in X Displacement in Y 1 Bare frame 16.76 28.94 2 X bracing 3.49 4.87 3 V bracing 4.1 5.97 4 Inverted V 3.97 5.01 5 Ecc forward 6.3 8.52 6 Ecc backward 6.77 8.77 2017, www.ijariit.com All Rights Reserved Page 699

storey height in m K L Rakshith, Smitha, International Journal of Advance Research, Ideas and Innovations in Technology. 12 10 8 6 4 2 0 0 5 10 15 20 25 30 lateral displacement in mm x bracing without bracing v bracings inverted v bracing ecc forward ecc backward displacement eec back Fig 3: Displacement plot From the analysis result it is observed that, displacement is less in braced frame structure compared to unbraced structure also from Response Spectrum Method the x bracings is having least displacement of 3.49mm and 4.87mm in both directions. The stiffness value for X bracing have been comparatively increased compared to other bracing systems. The stiffness will be 79.17% and 83.17%. 2) Storey drift in X and Y direction Table 5: Storey drift results Serial Number Type of Bracings Drift in X direction Drift in Y direction 1 Bare Frame 0.0018 0.00145 2 X Bracing 0.000133 0.000185 3 V Bracing 0.000183 0.000222 4 Inverted V 0.000158 0.000195 5 Eccentric forward 0.000252 0.000337 6 Eccentric backward 0.000272 0.000351 2017, www.ijariit.com All Rights Reserved Page 700

Fig 4: storey drift plot The storey drift of braced structure is less than that of unbraced structure. From the analysis result it is found that x bracing have least amount of storey drift in both directions. The storey drift value for X bracing in both direction is 0.000133 and 0.000185. 3) Base shear in X and Y direction Table 6: Base shear results Serial Number Bracings Base shear in X direction Base shear in Y direction 1 Bare Frame 1093 671.5 2 X Bracing 2448 2432 3 V Bracing 1784 2409 4 Inverted V 2418 1771 5 Eccentric forward 2426 2329 6 Eccentric backward 2351 2332 2017, www.ijariit.com All Rights Reserved Page 701

Fig 5: Base shear plot Base shear of structure with bracings is more than base shear of unbraced structure. In this base shear of X bracing is more then that of other bracing system. The value of base shear for X bracing in X and Y direction bracing are 2448 and 2432 KN respectively. B. Results for irregular structure 1) Displacement in X and Y direction Table 7: Displacement results `Serial no Bracings Displacement in X Displacement in Y 1 Bare frame 15.24 27.74 2 X bracing 3.975 9.24 3 V bracing 5.19 11.22 4 Inverted V 4.32 9.96 5 Ecc forward 5.63 11.48 6 Ecc backward 12.81 13.54 2017, www.ijariit.com All Rights Reserved Page 702

Fig 6: Displacement plot From the analysis result it is observed that, displacement is less in braced frame structure compared to unbraced structure also from Response Spectrum Method the x bracings is having least displacement of 3.97mm and 9.24mm in both directions. Stiffness value for X bracing have been comparatively increased compared to other bracing systems. The stiffness will be 73.91% and 67%. 2) Storey drift in X and Y direction Table 8: Storey drift results Serial Number Type of bracings Drift in X direction Drift in Y direction 1 Bare Frame 0.000676 0.000234 2 X Bracing 0.000190 0.000143 3 V Bracing 0.000247 0.000662 4 Inverted V 0.000348 0.000586 5 Eccentric forward 0.000275 0.000695 6 Eccentric backward 0.000691 0.000934 2017, www.ijariit.com All Rights Reserved Page 703

storey height K L Rakshith, Smitha, International Journal of Advance Research, Ideas and Innovations in Technology. 12 10 8 6 4 2 without bracing x bracing v bracing inverted v bracing ecc forward 0 0 0.0005 0.001 0.0015 0.002 storey drift Fig 7: Storey drift plot ecc back The storey drift of braced structure is less than that of unbraced structure. From the analysis result it is found that x bracing is having a least amount of drift in both directions. The storey drift value for both direction (X and Y) is 0.000190 and 0.000143. 3) Base shear in X and Y direction Serial Number 1 Table 9: Base shear results Bracings Base shear in X-direction Base shear in Y-direction Bare Frame 858 511 2 X Bracing 1617 1340 3 4 5 6 V Bracing Inverted V Eccentric forward Eccentric backward 1614 1260 1582 1312 1612 1252 1610 1010 2017, www.ijariit.com All Rights Reserved Page 704

Fig 8: Base shear plot Base shear of frame structure with bracings is more than shear of unbraced structure. In this study base shear of X bracing is more that of other bracing system. The value of base shear for X bracing in X and Y direction is 1617 and 1340 KN respectively. V. CONCLUSIONS Based on the analysis carried out by Response Spectrum method. In RCC frame building the displacement and storey drift decreases for different types of bracing system used compared to RCC frame building without bracings and the base shear increases for different types of bracings system used compared to unbraced frame structures. In regular and irregular RCC frame structure X- bracing gives less displacement and storey drift and base shear is increased. In regular and irregular RCC frame structure the performance of X-bracing gives better results compared other bracing system. From the result the regular RCC frame is having more stiffness compared to vertical irregular RCC frame structure. Steel bracing are used to strengthen or retrofit the existing structure. REFERENCES [1] N Nithin and R M Phuke, Analytical study of braced unsymmetrical RCC building, International journal of science and research, Volume 4, Issue 5,, Page No 485-489, May 2015. [2] Nauman Mohammed and Islam Nazrul, Behaviour of multistored RCC structure with different type of bracing system, International journal of science and research, Volume 2, Issue 12, Page No 7465-7478, March 2013. [3] Shachindra Kumar and Abhay sharma, Seismic behaviour of RCC building frame with steel bracing system using various arrangement, International journal of engineering research and technology, Volume 2, Issue 5, Page No 479-483, July 2015.. [4] Dhiraj Naxine and Prasad, Comparative study in the analysis of multistored RCC structure by different types of concentric bracing bracing system, International journal of engineering research and technology, Volume 5,Issue 7, Page No 483-488, 2015. [5] Prakarsh Sangave, Influence of masonry infill wall, Tie beam and RCC bracing on soft storey mechanism, International Journal of Engineering Research, Volume 6, Issue 2, Page No 422-431, April 2015. 2017, www.ijariit.com All Rights Reserved Page 705