International Journal of Research and Innovation (IJRI)
International Journal of Research and Innovation (IJRI) 1401-1402
ANALYSIS AND DESIGN OF RESIDENTIAL TOWER BY DYNAMIC ANALYSIS USING RESPONSE SPECTRUM METHOD
D.Ramarao1, K. Mythili2, G.Venkat Ratnam3 1 Research Scholar, Department Of Civil Engineering, Aurora's Scientific Technological & Research Academy, Hyderabad, India 2 Associate professor , Department Of Civil Engineering, Aurora's Scientific Technological & Research Academy, Hyderabad, India 3 Associate professor , Department Of Civil Engineering, Aurora's Scientific Technological & Research Academy, Hyderabad, India
Abstract This Project Named As “Analysis And Design Of Residential Tower (2basemetns+Stilt+31 Upper Floors)By Dynamic Analysis Using Response Spectrum Method� Involves The Analysis And Design Of Residential Tower 3-D Frames Of Uniform Floor heights for typical floors using very popular software tool ETABS 9.7.2. The main thesis of this Project is to achieve the following: 1).To arrive at minimum number of modes required to get modal mass participating ratio more than 90% by dynamic analysis using Response Spectrum Method. 2). To limit the lateral deflection at the top of the tower less than H/250(Where H = Height of the tower till terrace) for seismic load. 3). To limit the Inter Storey Deflection(Storey Drift) in any storey due to the minimum specified design lateral force, with factor of 1.0 less than 0.004 times the storey height. In addition to that the detailed study of seismology was undertaken and the feasibility of the software tool to be used was also checked. Till date many such projects have been undertaken on this very topic but the seismic analysis were generally done by static analysis but to this the seismic analysis is done by dynamic analysis for all possible load combinations pertaining to IS 456, IS 1893 and IS 13920.
*Corresponding Author: D.RAMARAO, Research Scholar, Department of CIVIL Engineer-
Design methodology:
ing, Aurora's Scientific Technological & Research Academy, Hyderabad, India
S. No
Points
Description
Published: October 27, 2014 Review Type: peer reviewed Volume: I, Issue : II
1
Structural system
Conventional beam slab arrangement
2
Method of analysis
Space frame method has been used for analysis of this structure, Software- E TABS
3
Foundation design
Conventional raft- SAFE software shall be used for the designing of raft.
Citation:D.RAMARAO1,(2014)Analysis And Design Of Residential Tower By Dynamic Analysis Using Response Spectrum Method
Brief Description of the Structure Proposed Structure consists of Residential Tower to be constructed at Gurgaon.
Salient Features of building are as follows.
Loads to be considered while designing: 1
Dead loads
Sizes of structural members x density of concrete
25 kN/cum
Name
New Town Heights at Gurgaon
a
Floor finish load
1.2 kN/sqm
Location
Gurgaon
b
3.0 kN/sqm
Type
Residential Building
No.of floors
2B+ST+31 Floors
Water proofing Terrace load on terrace, Inclusive of brick batcoba
IS-875-I
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International Journal of Research and Innovation (IJRI)
2
3
Live load
Masonry loads
i)Living rooms, bed room kitchen & toilets etc. ii)Corridors, passages & stairs iii)Balconies
2 KN/sqm. 3 KN/sqm 3 KN/sqm
External Wall loads(Concrete Blocks) Internal(Fly ash bricks)/ density
20 KN/sqm 10 KN/sqm
IS-875-II
Recommendation for construction materials: S.No
Construction Material
Specification
1
Reinforcement steel
Fe 500 D (TMT) (Ductile steel to be used)
2
Grade of concrete for a) Columns – M40,M35,M30,M25 b) Foundations/rafts - M25 c) Retaining wall and tie beams – M25 d) Conventional beams – M20,M40 e) Conventional slabs – M20
Ready Mix Concrete
3
Type of Masonry:
Concrete Block work for external walls and Fly ash brickwork for internal walls
4
Cement: OPC cement is preferable to use for important RCC work. In case of non-availability of OPC cement, PPC cement can be used.
Other Predominant Forces: S. No
load
4)
Earth quake load. a).Zone for Gurgaon b).Importance factor c). Type of structure d).Response Reduction Factor Soil type Time period to be used
V 1 SMRF 5 2.0 0.075h^0.75
Wind loads. Basic wind pressure (Gurgaon) Category Class
47m/s 2 C
5)
Preference: Use OPC cement Under constraint PPC cement Flyash not to be used
Soft Storey Due to Stilt: To take care of soft storey due to stilt, besides the columns designed and detailed for the calculated storey shears and moments, shear walls shall be placed symmetrically in both directions of the building as far away from the centre of the building as feasible, to be designed exclusively for 1.5 times the lateral storey force. Dynamic analysis: Dynamic analysis is being performed by the Response Spectrum Method. The design base shear (VB) shall be compared with a base shear (VBT) calculated using a fundamental period Ta. Incase VB is less than VBT, all the response quantities are multiplied by scale factor. Detailing for ductility: As per the provisions of IS 13920.
Covers for R.C.C Structures: Following values as recommended by IS.456-2000 and as per norms of NBC for fire resistance – 2 hours. S.No 1
Environmental condition
Mild
2
Covering
IS – 456- clause-26.4
a).Footings
50mm
b). Rafts
50 mm
c).Columns and Lift walls
40mm
d).Slabs
20mm(valid for 1.5hrs)
e).Beams
20mm (valid for 1.5 hrs)and dia of the bar whichever is maximum
Following load cases considered for design calculation: 1.5(DL+LL), 1.2(DL+LL+SPEC X), 1.2(DL+LL+SPEC Y), 1.2(DL+LL+WLXP), 1.2(DL+LL+WLXN), 1.2(DL+LL+WLYP), 1.2(DL+LL+WLYN) 1.5(DL+SPEC X), 1.5(DL+SPEC Y), 1.5(DL+WLXP), 1.5(DL+WLXN), 1.5(DL+WLYP), 1.5(DL+WLYN).
Specification
Slabs and beams are additionally protected by plastering, flooring /water proofing Which helps to enhance fire resistance time further. 3
Retaining wall
40mm for soil side(1.5 hours ok for basement) 25mm for other side
4
Water retaining walls To avoid corrosion in case of water proofing failure
50mm (for severe condition)
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International Journal of Research and Innovation (IJRI)
(vi)Height to Width ratio of building: 5.071 (vii)Length to Width ratio of building: 1.155 B.Structural Analysis and Design: (i)Structural Analysis Software: ETABS 9.7.2 Version (ii)Structural System: SMRF (iii)Foundation System: Raft foundation for entire tower (iv)Loading parameters: (a)Dead load: Self weight of slab + wall load + floor finishes (b)Live load: For Living areas -2KN/M2 For Balconies, Corridors, Staircases-3KN/M2 (c) Seismic Load: As per IS 1893:2002 (i) Zone Factor (Z): 0.36 for zone V (ii) Importance Factor (I): 1.0 (iii) Soil type: 2.0 (iv) Fundamental Time Period (Tx/y):
A seismic design of high rise buildings has assumed considerable importance in recent times. In traditional methods adopted based on fundamental mode of the structure and distribution of earthquake forces as static forces at various stories may be adequate for structures of small height subjected to earthquake of very low intensity but as the number of stories increases the seismic design demands more rigorous. [1]*
Height of building till Terrace (h) = 110.5 Tx= (0.075 x h^0.75) = 2.556 sec Ty= (0.075 x h^0.75) = 2.556 sec (v)Response Reduction Factor (R):5 (for SMRF R is 5) (vi)Seismic Coefficient (Ah x/y): X=0.0192 (Refer Page no. 1 of Appendix 1) Y=0.0192 (Refer Page no. 2 of Appendix 1) (Vii) Seismic Weight: 325257.41kN. (Refer Page no. 1 of Appendix 1) (viii) Base shears Vibe x/y: Vbx=6230.28KN ( Refer Page no. 1 of Appendix 1) Vby=6230.28KN ( Refer Page no. 2 of Appendix 1) (ix) Damping: 5% ( Since it is a concrete structure) (V) Seismic Analysis Method: Response Spectrum Method . (a)No. of modes considered: 20 ( with 20 no’s of modes, modal mass participating ratio is more than 90%,Refer Table 1)
PHASES OF THE PROJECT The project was divided into two phases. They are as follows:Phase-1- Developing model using ETABS. Phase-2- Analysis of reinforced concrete frames for static loads (dead, live, wind and load combinations) and dynamic load (Earth quake load-Spectrum cases). Inferences from the of Etabs Model: A.Geometrical Configuration of the Tower: (i)No of storey: (2 Basements + Stilt +31 upper floors) (ii)Floor Height in ‘m’: (Basement 2 is resting on Foundation system, Basement 1=3.65,GF=4.4,First Floor=3.25,Typical floor 3.2,LMR and SHR=2.785 ) (iii)No of lift: 3 (iv)No of staircase :2 (v)Total height of structure: 113.285m till LMR roof Height of building till terrace = 110.5m Width of building = 21.79m Length of building = 25.18m
(b)Modal Mass participation: First mode: 73% (Refer Table 1) Second mode: 18.2% (Refer Table 1) (c)Scale Factor i. Along X- direction: 1.4837 (Refer Appendix 3) ii. Along Y- direction: 1.6158 (Refer Appendix 3) (Vi) Total Deflection of Building: with fundamental time period i.Along X –direction: 110.81 mm (Refer for Point 595 of Table 2) < 442mm permissible (Permissible deflection = Span/250(=442mm) as per clause 23.2 of IS: 456-2000) ii.Along Y – direction: 129.56mm (Refer for Point 53 of Table 2) < 442mm permissible (Permissible deflection = Span/250(=442mm) as per clause 23.2 of IS: 456-2000) (Vii) Inter story Deflection (Storey Drift): With Fundamental Time period: 0.001467 <0.004(Refer Appendix 2)
Conclusion The tasks of providing full seismic safety for the residents inhabiting the most earthquake-
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International Journal of Research and Innovation (IJRI)
prone regions are far from being solved. However in present time we have new regulations in place for construction that greatly contribute to earthquake disaster mitigation and are being in applied in accordance with world practice. [8]* [4]*
Author:
In the regulations adopted for implementation in India the following factors have been found to be critically important in the design and construction of seismic resistant buildings: •Sites selection for construction that are the most favorable in terms of the frequency of occurrence and the likely severity of ground shaking and ground failure; •High quality of construction to be provided conforming to related IS codes such as IS1893, IS 13920 to ensure good performance during future earthquakes. •To implement the design of building elements and joints between them in accordance with analysis .i.e. ductility design should be done. •structural-spatial solutions should be applied that provide symmetry and regularity in the distribution of mass and stiffness in plan and in elevation. •Whereas such the situations demands irregularity maximum effort should be given to done away with the harmful effects like that of “ SHORT COLUMN EFFECT” Researchers indicate that compliance with the above-mentioned requirements will contribute significantly to disaster mitigation, regardless of the intensity of the seismic loads and specific features of the earthquakes. These modifications in construction and design can be introduced which as a result has increase seismic reliability of the buildings and seismic safety for human life.
D.Ramarao student at Aurora s scientific and technological and Research Academy,Hyderabad, India.
K. Mythili M.Tech(structural engg) Asso.Professor at Aurora's scientific and technological and Research Academy,Hyderabad, India.
G.Venkat Ratnam Asso.Professor Aurora's scientific and technological and Research Academy,Hyderabad, India.
References:[1].Murthy C.V.R, Learning earthquake design [2]Agrawal, Shrikhande Mansih, earth quake resistant design of structures [3]IS: 456:2000, Plain and Reinforced code of practice. [4]IS: 1893(Part-1):2002, Criteria for earth quake resistant design of structure. [5]IS: 13920:1993, Ductile detailing of RCC structure subjected to earth quake force. [6]SP:16,Design Aid for Reinforced concrete to IS:456:2000. [7]Ramamurtham,Theory of structures [8] Ashimbayev M.U., Itskov I.E., Lobodryga T.D.,living with natural and technological hazards, topic a.2: reducing vulnerabilities in existing building and lifelines
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