Analysis and Design of Multistorey Building using ETABS

 

Analysis and Design of Multistorey Building using ETABS

Fathima Shalbana1, Niba E1, Farsana C V1, Athulya Vijay N2

1Students,2Assistant Professor,

Department of Civil Engineering, KMCT College of Engineering for Women, Kerala, India

AbstractStructural Engineers are mainly concerned with finding out the behavior of a structure when subjected to horizontal forces and adequate stiffness is required for the buildings which are high rise in order to con front horizontal forces aroused by winds and earthquakes. To confront the horizontal forces i.e., lateral loads developed by earthquakes and to contribute more stiffness to the structure we use Shear walls, which are added to the interior of the proposed structure. The principle objective of this project is to Plan, analyse and design a multi-storeyed building [ G + 4(3 dimensional frame)] using ETABS. The design involves analysing the whole structure by ETABS. The design methods used in ETABS analysis are Limit State Design conforming to Indian Standard Code of Practice. ETABS features a state-of- the-art user interface, visualization tools, powerful analysis and design engines with advanced finite element and dynamic analysis capabilities. From model generation, analysis and design to visualization and result verification, ETABS is the professionals choice. Initially it started with the analysis of simple 2 dimensional frames and manually checked the accuracy of the software with the results. The results proved to be very accurate for all possible load combinations [dead, live, wind and seismic loads].

KeywordsAnalysis and designing,Etabs,commertial building

1. INTRODUCTION

Structural engineering is a wider discipline under the field of civil engineering. It is a vast topic with unlimited theories and practices. Its a field that is still developing with huge innovations and ideas. The roles and responsibilities of a structural engineer includes structural designing, selection of materials best suited for the structure, analysis of structures etc. The present project deals with the analysis and design of a multi storied commercial complex at Puthiyara, Kozhikode. Structural designing include calculating loads and stresses acting on the building, analysis for the loads, design of sections of structures to sustain the loads. So that the structure designed will withstand the load predicted safely.

Analysis of structure is presently carried out by software like ETABS, SAP, STAAD etc. As years pass new software are being developed for analysis of structures at different condition of loads like wind, earthquake etc. the results can be understood and interpreted from the software to know the validity of values provided as output.

Now a days framed structures are preferred for commercial buildings. The framed system of construction has mainly two advantages. Firstly, the walls, which are used for, are not load bearing ones and hence the thickness of the walls can be reduced to a considerable extent. This reduces weight of the building and the load transferred to the foundation will be lessened. Subsequently the construction materials can be saved. Secondly the floor area of the building can be increased

A structure is subjected to various types of loading such as permanent, movable and occasional. The permanent loads are due to self-weight of structure, semipermanent ones are due to fixtures, furniture, stationary etc. which are rarely moved and is considered as Imposed Loads or live loads. 2 Movable loads are due to moving vehicles, etc. The occasional loads are due to wind, earthquake or floods.

Earthquake has also become one of the natural challenging factor for the efficient construction work. It is one of the dominant constrains while designing the frame building in the earthquake prone zone. Earthquake is a natural phenomenon as old as history of earth itself and is considered to be the most unpredictable one among all other natural disasters. Now a days, designers and engineers are giving more emphasis towards the earthquake resistance while analyzing and designing any structure to minimize the seismic impact.

1. 1. DESIGN PHILOSOPHIES

      There are three philosophies for the design of reinforced concrete namely:

      1. Working stress method
      2. Ultimate load method
      3. Limit state method

   2. STAGES IN STRUCTURAL DESIGN

      The process of structural design involves the following stages

      • Structural planning.
      • Estimation of loads.
      • Analysis of structure.
      • Member design.
      • Drawing, detailing and preparation of structures. 2.OBJECTIVE
        • To analyse and design a G+4 commercialbuilding.
        • To prepare the master plan for the commercial building
        • To compare the result with ETABS

1. PLAN OF COMMERTIAL BUILDINGFig :3.1 Ground Floor Plan

   Fig 3.2. 1-4 Floor Plan

   Fig 3.4 Stair Room Plan

2. METHODOLOGYPRE-PLANNING DISCUSSION

   PREPARATION OF SKELETAL PLAN

   STUDY OF PLAN

   LOCATING COLUMNS

   DIMENSIONING OF COLUMN, BEAM, SLAB

   LOAD CALCULATION OF DL, LL, WL

   ETABS 3D MODELLING

   ST ANALYSIS FOR LOAD COMBINATION

   STRUCTURAL DESIGN OF BEAM, COLUMN, SLAB, STAIR AND FOUNDATION

   STRUCTURAL DRAWING

3. A BRIEF DESCRIPTION OF SOFTWARES USED IN TRAINING

   1. 1. ETABS 2017:

         ETABS is an engineering software product that caters to multi- story building analysis and design. Modeling tools and details, and cross-sections may be generated for concrete and steel structures. ETABS provides an unequaled suite of tools for structural engineers designing buildings, whether they are working on one-story industrial structures or the tallest commercial high-rises. Immensely capable, yet easy-to-use, has been the hallmark of ETABS since its introduction decades ago, and this latest release continues that tradition by providing engineers with the technologically-advanced, yet intuitive, software they require to be their most productive

      2. AUTO-CAD 2016:

   All the drawing and detailing works for this training were done by making use of AutoCAD 2007, developed by M/s. AUTODESK, USA. As such, this is the pioneering software in CAD. AutoCAD is a vector graphics drawing program. It uses primitive entities such as lines, poly-lines, circles, arcs and text as the foundation for more complex objects. AutoCADs native file format, DWG, and to a lesser extent, its interchange file format, DXF has become the standards for interchange of CAD data..

4. MODELING IN ETABS
   

   Groups

   Table 7.4 – Group Definitions

   1. 1. PropertiesThis chapter provides property information for material frame sections ,shell sections and links.

         Materials

         Table 1-Material Properties- Summary

         Fig 6.1 Importing of Floor Plan from Auto-cad:

         Column locating

5. STRUCTURE DATAThis chapter provides model geometry information, including items such as story levels, point coordinates, and element connectivity
   

   Story Data

   Frame Sections

   Table 2 – Frame Sections – Summary

   Shell Sections

   Table 3 – Shell Sections – Summary

   Reinforcement Sizes

   Table 4 – Reinforcing Bar Sizes

   Table 7.1 – Story Data

   Tendon Sections

   Table 5 – Tendon Section Properties

   Grid Data

   Table 7.2 – Grid Systems

   1. 1. Framing Of Model

   <h4Mass

   Table 7.3- Mass Source

6. ANALYSIS IN ETABSThis chapter provides loading information as applied to the model.
   

   Load Patterns

   Table 4.1 – Load Patterns

   Load Cases

   Table 6 – Load Cases – Summary

   1. 1. Auto Wind Loading

         Indian IS875:1987 Wind Load Calculation

         Lateral wind loads for load pattern WL X according to Indian IS875:1987, as calculated by ETABS

         Exposure Parameters Exposure From = Diaphragms Structure Class = Class B Terrain Category = Category 2 Wind Direction = 0 degrees

         Basic Wind Speed, Vb Vb = 39 meter/sec

         Windward Coefficient, Cp,wind Cp,wind =0.8

         Leeward Coefficient, Cp,lee Cp,lee =0.5 Top Story = Story6

         Bottom Story = Base

         Factors and Coefficients

         Risk Coefficient, k1 [IS 5.3.1] k1 = 1

         Topography Factor, k3 [IS 5.3.3] k3 = 1

         Lateral Loading

         Design Wind Speed, Vz [IS 5.3]

         Vz = Vb k1 k2 k 3 Vz = 40.837095

         Design Wind Pressure, p z [IS 5.4] pz = 0.6 V 2 z

         Applied Story Forces

         Lateral wind loads for load pattern WL Y according to Indian IS875:1987, as calculated by ETABS

         Exposure Parameters Exposure From = Diaphragms Structure Class = Class B Terrain Category = Category 1 Wind Direction = 90 degrees

         Basic Wind Speed, Vb Vb = 39 meter/sec

         Windward Coefficient, Cp,wind Cp,wind =0.8

         Leeward Coefficient, Cp,lee Cp,lee =0.5 Top Story = Story6

         Bottom Story = Base Include Parapet = No Factors and Coefficients

         Risk Coefficient, k 1 [IS 5.3.1] k1 = 1

         Topography Factor, k3 [IS 5.3.3] k3 = 1

         Lateral Loading

         Design Wind Speed, Vz [IS 5.3]

         Vz = Vb k 1 k2 k 3 Vz = 42.787095

         Design Wind Pressure, p z [IS 5.4] pz = 0.6 V 2 z

         Applied Story Forces

      2. Auto Seismic Loading

   IS 1893:2016 Seismic Load Calculation

   Lateral seismic loads for load pattern EQ X according to IS 1893:2016, as calculated by ETABS

   Direction and Eccentricity

   Direction = X Structural Period

   Period Calculation Method = Program Calculated

   Factors and Coefficients

   Seismic Zone Factor, Z [IS Table 3] Z = 0.36 Response Reduction Factor, R [IS Table 9] R = 5 Importance Factor, I [IS Table 8] I = 1 Site Type [IS Table 1] = II

   Seismic Response

   Spectral Acceleration Coefficient, Sa /g [IS 6.4.2]

   Sa g = 1.36 T Sa g = 2.396565

   Equivalent Lateral Forces

   Seismic Coefficient, Ah [IS 6.4.2] Ah = Z I Sa g 2 R

   Calculated Base Shear

   Applied Story Forces

   lateral seismic loads for load pattern EQ Y according to IS 1893:2016, as calculated by ETABS.

   Direction and Eccentricity

   Direction = Y

   Structural Period

   Period Calculation Method = Program Calculated

   Factors and Coefficients

   Seismic Zone Factor, Z [IS Table 3] Z = 0.36 Response Reduction Factor, R [IS Table 9] R = 5 Importance Factor, I [IS Table 8] I = 1 Site Type [IS Table 1] = II

   Seismic Response

   Spectral Acceleration Coefficient, Sa /g [IS 6.4.2] Sa g = 1.36 T Sa g = 2.10472

   Equivalent Lateral Forces

   Seismic Coefficient, Ah [IS 6.4.2] Ah = Z I Sa g 2 R

   Calculated Base Shear

   Applied Story Forces

7. LOAD COMBINATIONS

Design of the structures would have become highly expensive in order to maintain either serviceability and safety if all types of forces would have acted on all structures at all times. Accordingly the concept of characteristics loads has been accepted to ensure at least 95 percent of the cases, the characteristic loads are to be calculated on the basis of average/mean load of some logical combinations of all loads mentioned above. IS 456:2000, IS 875:1987 (Part-V) and IS 1893(part-I):2002 stipulates the combination of the loads to be considered in the design of the structures. The different combinations used are:

Table 4.10 – Load Combinations

10 ANALYSIS RESULTS

The structure was analysed as ordinary moment resisting space frames in the versatile software Etabs 2015. Joint coordinate command allows specifying and generating the coordinates of the joints of the structure, initiating the specifications of the structure. Member incidence command is used to specify the members by defining connectivity between joints. The columns and beams are modelled using beam elements. Member properties have to be specified for each member. From the analysis, maximum design loads, moments and shear on each member was obtained. From these values, we design the structure

1. 1. Axial Force.
   2. Elevation view of axial force diagram

   3. Torsion diagram

   4. Elevation view of torsion diagram

   5. plan view of torsion diagram

   6. Shear force diagram

   7. Elevation view of shear force diagram
   8. Plan view of shear force diagram
   9. Bending moment diagram
   10. Elevation view of bending moment diagram
   11. Plan view of bending moment diagram

11 DESIGN OF RC BUILDING

General The aim of structural design is to achieve an acceptable probability that the structure being designed will perform the function for which it is created and will safely withstand the influence that will act on it throughout its useful life. These influences are primarily the loads and the other forces to which it will be subjected. The effects of temperature fluctuations, foundation settlements etc. should be also considered. The design methods used for the design of reinforced concrete structures are working stress method, ultimate load method and limit state method. Here we have adopted the limit state method of design for slabs, beams, columns and stairs. In the limit state method, the structure is designed to withstand safely all loads liable to act on it through its life and also to satisfy the serviceability requirements, such as limitation to deflection and cracking. The acceptable limit of safety and serviceability requirements before failure is called limit state. All the relevant limit states should be considered in the design to ensure adequate degrees of safety and serviceability. The structure should be designed on the basis of most critical state and then checked for other limit states.

Plan view of 1st floor

Plan view of 2nd floor

Plan view of 3rd floor

Plan view of 4th floor

Plan view of 5th floor

Plan view of 6th floor

Rendered view

RESULT AND CONCLUSION:

Analysis and design of an apartment building having G+10 storeys is done. Analysis is done by using the software ETABS V15.2, which proved to be premium of great potential in analysis and design of various sections. The structural elements like RCC frame, shear wall and retaining walls are also provided. As per the soil investigation report, an isolated footing is provided. The design of RCC frame members like beam and column was done using ETABS. The analysis and design was done according to standard specifications to the possible extend. The various difficulties encountered in the design process and the various constraints faced by the structural engineer in designing up to the architectural drawing were also understood.

FUTURE SCOPE:

• Dynamic analysis can also be done using ETABS.
• Slab and footing can be designed using SAFE.
• In ETABS 2017 different types of slabs can be designed.
• The sections designed in ETABS can also be designed by conventional methods or STAAD-PRO and result can be compared.
• The irregular structures subjected to different load cases can also be analyzed and designed in ETABS.

REFERENCES

[1] Design of R.C.C. Structures by N. Krishna Raju.

[2] Dr. Panchal and P M Marathe, comparative method of study for RCC, composite and steel options in a G+30 story commercial building situated in earthquake zone IV. Institute of technology, Nirma university, Ahmedabad-382 481,08-10 December, 2011.

[3] IS: 456-2000, Code of Practice Plain and Reinforced concrete.

[4] IS: 875-1987 (Part 1) 1987, Code of Practice for Design Loads (other than earthquake) for buildings and structures.

[5] IS: 875-1987 (Part 2) 1987, Code of Practice for Design Loads (other than earthquake) for buildings and structures – Imposed loads.

[6] Mohd atif, Prof. Laxmikant vairagade, Vikrant nair, comparative study on seismic analysis of multistorey building stiffened with bracing and shear wall, IRJET-2015

[7] Nabin Raj , S.Elavenil, Analytical Study on Seismic Performance of Hybrid Structural System Subjected To Earthquake , IJMER-2012

[8] Nitin N.S and R.M.Phuke , Analytical study of Braced Unsymmetrical RCC Building, IJSR-2013

[9] Shashikala koppad, Dr. S V Itti, comparative study of RCC and composite multi-storeyed buildings. ISO 9001:2008 certified International journal of engineering and innovative technology. Vol 3, ISSMC 5, November 2013.

[10] Sonia Longiam, S Aravindan, Analysis and design of shopping mall against lateral forces. International journal of engineering science invention.

[11] SP16, Bureau of Indian standard, New Delhi, 1990.

[12] Syed khasim mutwalli, Dr. Shaik kamal mohammed azam,

Dynamic response of high rise structure under the influence of shear walls. Syed khasim mutwalli. Int. journal of engineering research and applications. ISSN:22248-9622, Vol 4.