IRJET - Sesismic Analysis of Multistorey Building using ETABS
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This document summarizes a study that analyzes the seismic performance of a multi-story building using the structural analysis software ETABS. The building is designed according to Indian codes for dead, live, wind and seismic loads. Shear walls are included in the structural design to resist lateral loads. Two models are analyzed - one with columns designed as shear walls, and one with minimal column thickness. The results show that the model with shear walls performed better under lateral loads and had higher base shear than the column-only model. The study concludes that including appropriately placed shear walls improves the structural stability of buildings under seismic loads.
IRJET - Sesismic Analysis of Multistorey Building using ETABS
- 1. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 07 Issue: 03 | Mar 2020 www.irjet.net p-ISSN: 2395-0072 © 2020, IRJET | Impact Factor value: 7.34 | ISO 9001:2008 Certified Journal | Page 1196 SESISMIC ANALYSIS OF MULTISTOREY BUILDING USING ETABS DHIVYABHARATHI S, ASHWIN R, AKILAN S, ARUNPRABHU K.S 1Assistant Professor, Department of Civil Engineering, Bannari Amman Institute of Technology, Sathyamangalam, Tamilnadu, India- 638401 2, 3,4UG Students, Department of Civil Engineering, Bannari Amman Institute of Technology, Sathyamangalam, Tamilnadu, India- 638401 ----------------------------------------------------------------------***--------------------------------------------------------------------- Abstract – This project presents RCC framed building designed and analyzed underthelateralloadingeffectof wind and earthquake using E-tabs software. It is incorporated with all, major analysis of static, dynamic linear and non-linear loads. At the modelling stage, the members are arranged as line members, taking the horizontal effects of wind & seismic forces. Key Words: Etabs, Multi-storey building in Etabs, Lateral load, shear/Lift wall, Optimum position of shear wall, Base shear, centrally placed shear wall. 1. INTRODUCTION The increase in population has increased the demand for land occupancy which in turn has led to the construction of high raised buildings. The primary purpose of structural components is to resist the gravity loads. In addition to these loads, the structure must be designed to resist lateral forces to ensure structural stability. The Shear walls are the structural components most widely employed to design an earthquake resistant structure. But the codal provisions for seismic design do not allow reduction in column thickness. In this study an attempt is made to reduce the thickness of column and at the same time without violating the codal suggestions. The main objective of the study is to satisfy the architecturaldemandwithbetterstabilityof the structure. The present paper briefly describes the comparative behaviour of models in which column is designed as shear wall to that of column designed with minimal thickness as that of wall. 1.1 Structural system RCC columns,shear walls andbeams have beenlaidout in plan in coordination with architectural and services drawingsis provided.The seismiczone III isconsidered for Chennai. Regarding sub structure, as per the soil reportpilefoundationisrecommended.Thecut-offlevel of the piles has been considered as 1m below the existing ground level. The refusal strata were encountered at 7.5m depth. Hence, the effective length of the piles to be taken will be 8-9.5 m. The load carrying capacity of different diameter piles and depth are given below: A structure is said to be designed efficiently if all the members are so arranged in a way that they transmit their selfweightandotherimposedloadstofoundation and supporting structures by cost effectively so as to satisfy the requirement of architecture, structural stability and thenatureofthesitewithsufficientsafety. In addition to engineering calculation, experience and good judgement may also do much towards safety and economy of the structure. 1.2 Design codes Design RCC design has been based on provision laid down as IS: 456-2000 General construction in plain and reinforced concrete- code of practice, following Limit state philosophy. Other codes of practice to be referred to are as follows: 1) IS 875-1987 Part (I, II and IV) code of practice for design loads for buildings and structures (other than earthquake) 2) IS 875 Part III-2015 code of practice for wind loads for buildings and structures. 3) IS 1893-2016 criteria for earthquake resistant construction of buildings. 4) IS 4326-1993 Earthquake resistant construction of buildings. 5) IS 456-2000 Code of practice for plain and reinforced concrete. Diameter of pile(mm) Load carrying capacity (KN) Uplift capacity (KN) 450 700 300 500 900 400 600 1250 600
- 2. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 07 Issue: 03 | Mar 2020 www.irjet.net p-ISSN: 2395-0072 © 2020, IRJET | Impact Factor value: 7.34 | ISO 9001:2008 Certified Journal | Page 1197 2. Material of specifications Grade of concrete The Indian Code IS: 456-2000, permits a minimum grade of concrete for reinforced members as M 25 and the following concrete Grades have been for various structural elements. 1) M-25 grade concrete hasbeenusedforallstructural elements. 2) M-25 grade concrete has beenusedforpilesandpile caps (400kg/m3) Reinforcement All reinforcement bars to be used in the structural elements shall be high yield strength deformed thermo- mechanically treated bars with yield stress of 500 MPa and minimum elongation of 18.0% conforming to IS: 1786-1985. Cover to Reinforcement Minimum values for the nominal cover to be provided to all reinforcement, including links of normal weight aggregate concrete depend on the condition of exposure and minimum specified period of fire resistance.Clearcovertothemainreinforcementinthe various structural elements depends on above criteria shall be: 1) Pile cap - 75mm 2) Columns – 40mm 3) Pedestals – 40mm 4) Beams – 30mm or bar diameter 5) Slabs – 20mm 6) Staircase – 20mm 7) Water tank walls and slabs – 30mm 8) Shear walls – 25mm 2.1 Loads Dead Loads Following unit weight of building materials have been considered in accordance with IS: 875(Part- I) and IS 1911 1) Reinforced cement concrete - 25KN/m3 2) Plain cement concrete – 25KN/m3 3) Brick masonry – 19KN/m3 4) Light weight filling in sunken area – 10KN/m3 5) Cement mortar/plaster – 20KN/m3 6) Floor finish – 2KN/m3 7) Brick bat for terrace – 20KN/m3 Live Loads Following live loads have been considered in design in accordance with IS: 875(Part II)-1987 1) General Floor area – 2KN/m3 2) Staircase & corridor – 4KN/m3 3) Play area, Gym floor load – 5KN/m3 Seismic Loads As per IS 1893 (Part I)-2002 Where, Ah – Design Horizontal seismic coefficient W – Seismic weight of the building Design Horizontal seismic coefficient, Ah = z/2*I/R*Sa/g Z – Zone factor = 0.16 as applicable for structure Built in Zone III I – Importance factor for the building = 1.5 R – Response reduction factor = 5 (SMRF) Sa/g – Average response accelerationcoefficientis taken for soil type – 2 and 5% damping Seismic forces are calculated for full dead load plus percentage of imposed load. Wind Loads It can be mathematically expressed as follows Vz = Vb x K1 x K2 x K3 Design Wind speed (Pz) The wind pressure at any height above mean ground level shall be obtained by the following relationship between wind pressure and wind speed Pz = 0.6 Vz 2 Where, Pz = Wind pressure at height z, in N/m2 and Vz = Design wind speed at height z, in m/s
- 3. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 07 Issue: 03 | Mar 2020 www.irjet.net p-ISSN: 2395-0072 © 2020, IRJET | Impact Factor value: 7.34 | ISO 9001:2008 Certified Journal | Page 1198 Load Combination The building is analyzed for following Load combinations as indicated in IS: 456-2000. Whenever dead &imposedloadiscombinedwithearthquakeload with appropriate part of the imposed load as specified in IS: 1893-2002 is adopted both for evaluating effect and for combined load effects used in such combinations 1) 1.5 x (Dead load + Live load) 2) 1.5 x (Dead load ± Earthquake load/wind load in X- direction 3) 1.5 x (Dead load ± Earthquake load/wind load in Z- direction 4) 0.9 x (Dead load) ± 1.5 (Earthquake load/wind load in X-direction) 5) 0.9 x (Dead load) ± 1.5 (Earthquake load/wind load in Z-direction) 6) 1.2 x (Dead load + Live load±Earthquakeload/wind load in X-direction) 7) 1.2 x (Dead load + Live load±Earthquakeload/wind load in Z-direction) 2.2 Design Methodology The RCC design shall be based on provisions laid down in IS: 456-2000 code of practice for plain and reinforcedconcrete,followinglimitstateofphilosophy. The structure model involves the assemblage of structural elements that present the typical frame in a building and its behaviour under external loading is observed. It has been assumed that buildings falls under seismic loading. The height of each storey is 3m. The grade of concrete used is M25 and the grade of steel usedisFe500.Beamsandcolumnsweremodelled as frame elements and the beam-column joints are assumed to be rigid, intended to get bending moments at the face of beam and column. 3. CONCLUSION From the results obtained, it has been noticed that the model shear wall is more stable than the model designed with column against lateral forces. At the same time, the base shear is higher in shearwallmodel as that compared with column model. Hence it advisable to place shear wall in appropriate positions in the structure wherever required. Usage of ETABS software minimizes the time required for analysis and designs. REFERENCES 1) Ashiru Muhammad et al., Comparative analysis of seismic behaviour of multi storey composite steel and conventional Reinforced concrete Framed structures, International journal of scientific and Engineering Research vol-6 Issue-10, ISSN: 2229-5518, 2015. 2) Kulvendra Patel, Wind and seismic Analysis of Elevated Tank using staad.pro, International Research Journal of Engineering and Technology, Vol-5. Issue - 10, 2018. 3) Mahendra Kumar et al., Seismic Behaviour of Buildings with Shear wall, International Journal of Engineering Research and Technology, ISSN: 2278- 0181, 2018. 4) Sirisha.p et al., Comparative Analysis of two Different Wind speeds for a Multi-storey building. International Journal of Engineering sciences and Research Technology. ISSN: 2277-6955, 2016. 5) Tejashree Kulkarni et al., Analysis and Design of High rise BuildingFrameUsingstaad.pro,International Journal of Research in Engineering and Technology, Vol-5, Issue-4, 2016.