Dr. D.R. Panchal Assistant professor, Applied Mechanics and Structural Engineering Department, Faculty of technology and Engineering, The M.S. University of Baroda, Vadodara, Gujarat, India.
ABSTRACT:
In this present paper the comparative study of G+30 steel concrete composite, steel and RCC building is done using dynamic analysis i.e. time history analysis. Etabs structural package is used for the analysis. In case of composite building the encased column sections are used. The analysis is done using the IS 1893-2002.The time history analysis using total five ground motion earthquake data i.e. Bhuj, Kobe, Chamoli, Uttarkashi, Chamba were used in order to achieve the seismic response and the average response of all five ground motion database were compared for the above mentioned buildings. The nonlinear modal analysis (FNA) method were used for the analysis purpose. The parameters such as Base shear, Story drift and maximum top displacement are compared. Results shows that the composite building shows response nearly similar to the steel building. On the other hand, RCC building shows more response compared to steel and composite building.
INTODUCTION:
Now a day there is a drastic demand of column free area in construction of mid to high rise building. If the conventional RCC system will used for the construction, then the column size would be much higher and if the purely steel building will have used then it’s have its own disadvantages regarding stiffness and fire resistance. So one has to think about different structural system in such a way that it gives the advantages of both steel and RCC, so for this the composite system is incorporated in order to achieve more column free area for the mid to high rise buildings. In case of composite columns, the steel section will be encased in RCC. In this case the steel provides the sufficient ductility and concrete provides the sufficient resistance against the dynamic loading. So the composite building frames shows the better characteristics of the RCC and Steel which results in rapid construction and ultimately saving in cost of the construction.
FIG. 1 COMPOSITE ELEMENTS
Composite action between the steel beam and concrete slab is an important feature of the composite building frames. The composite action between steel beams and the concrete slab is achieved with help of the mechanical shear connectors; this will impart the sufficient lateral load resistance and increase the moment carrying capacity of the steel beam which results in reduction of the size of the beam and larger spans can be achieved. So eventually the composite system will considerably reduce the total weight of the building and improves the performance under different kind of loading systems. Also the composite system provides a sufficient increment in lateral stiffness of the structure so it will be much effective in case where the lateral stiffness is important parameter. Fig.1 shows the composite columns (a) and composite deck slab with steel beam (b).
TIME HISTORY ANALYSIS
The dynamic analysis i.e. time history analysis is used in order to achieve the actual performance of the building using the different ground motion database. The time history analysis is the performance of the structure at each and every time interval during an earthquake event which is mainly the function of the inertia force and acceleration. The ground motion database includes the base acceleration, displacement and velocity which is recorded at suitable station as mentioned in the input file.
The time history analysis is also known as nonlinear dynamic analysis. This is very accurate method to assessed the seismic performance of the building. It is a step by step procedure and its required ground motion database for a particular earthquake event. The data mainly posses’ acceleration, velocity and displacement plotted against the time of the particular earthquake even, which gives the performance of the structure under a particular earthquake event.
OBJECTIVES:
- To compare the seismic behaviour of G+30 storeyed composite, RCC and steel frame using Time History Analysis.
- To find the responses of the buildings in terms of the base shear, maximum top displacement and storey drift.
- To compare the results of the static method (ESA) and dynamic method (RSA and TH).
- To observe the behaviour of the buildings under the five different ground motion databases as mentioned above.
In this present work the time history analysis of the three buildings are considered i.e. steel concrete composite, RCC and Steel. This is the G+30 storey commercial office building having 105 m height from the ground level along with the three floors of basement for the parking purpose. Also the central lift shaft of RCC is provided. The plan of the typical floor is as shown in fig 2. There are total five ground motion earthquake database i.e. Bhuj 2001, Kobe1995, Chamoli, Uttarkashi, Chamba were used and results are compared.
FIG. 2 ARCHITECTURAL LAYOUT
MODELING PARAMETERS:
| GEOMETRICAL DETAILS: | ||
| STOREY HEIGHT | = | 3.0 m |
| DEPTH OF THE FOUNDATION BELOW GROUND | = | 9.0 m |
| STAIRCASE | = | 2 Nos. |
| NO. OF STORIES | = | G+30 plus 3 Basement and staircase cabin |
| WALLS | = | 150 mm thick brick wall |
| Slab Thickness | = | 125 mm in RCC and Steel building |
| Lift shaft | = | 300 mm |
| MATERIAL PROPERTIES: | ||
| GRADE OF CONCRETE | = | M40 IN ALL CASE |
| GRADE OF STEEL | = | Fe 415 (HYSD) FOR REINFORCING STEEL |
| = | Fe 250 FOR STRUCTURAL STEEL |
COMPOSITE DECK PROFILE:
| LOADING: - | ||
| DEAD LOAD | = | SELF WEIGHT |
| FLOOR FINISH | = | 1.5 kN/m2 |
| LIVE LOAD IN PASSAGE AND OFFICE AREA | = | 4 kN/m2 |
| LIVE LOAD IN URINALS | = | 2 kN/m2 |
| LIVE LOAD IN STAIRCASE | = | 4 kN/m2 |
| EARTHQUAKE LOAD | = | AS PER IS1893 (PART 1) |
| MASONARY WALL | = | 7.65 KN/m |
| PARAPET WALL | = | 3 KN/m |
| SEISMIC DEFINITION: - | ||
| ZONE FACTOR ‘Z’ | = | 0.16 FOR ZONE III |
| IMPORTANCE FACTOR ‘I’ | = | 1 |
| RESPONSE REDUCTION FACTOR ‘R’ | = | 4 FOR ALL BUILDINGS |
| TIME PERIOD | = | 1.92 Sec FOR X DIRECTIONS |
| = | 1.45 Sec FOR Y DIRECTIONS | |
| SOIL TYPE | = | HARD SOIL |
GEOMETRICAL DIMENSIONS:-
| Table I - COLUMN SIZE | |||
| MODEL | COMPOSITE | STEEL | R.C.C. |
| FROM FOUNDATION TO G.L. | 800 x 800 with W 18 x 86 | W 36 X 487 | 1200 X 1200 |
| FROM GROUND LEVEL TO 10th FLOOR | 700 x 700 with W 18 x 86 | W 36 X 395 | 800 X 800 |
| FROM 10th FLOOR TO 20th FLOOR | 650 x 650 with W 18 x 60 | W 24 X 279 | 700 X 700 |
| FROM 20th FLOOR TO TERRACE | 450 x 450 with W 14 x 53 | W 18 X 185 | 550 X 550 |
| Table II - BEAM SIZE | |||
| MODEL | COMPOSITE | STEEL | R.C.C. |
| FROM FOUNDATION TO G.L. | W 18 X 60 | W 24 X 76 | 300 X 450 |
| FROM GROUND LEVEL TO 10th FLOOR | W 18 X 60 | W 24 X 55 | 300 X 450 |
| FROM 10th FLOOR TO 20th FLOOR | W 18 X 60 | W 21 X 68 | 300 X 450 |
| FROM 20th FLOOR TO TERRACE | W 18 X 60 | W 18 X 50 | 300 X 450 |
(Note: In case of composite and steel building American sections are used. Units of all the American sections i.e. W 18 x 86 where 18 is the depth in inches and 86 is the weight per unit length in Lb/feet. Units of all the RCC members are in mm.)
FIG. 3 STRUCTURAL LAYOUT
RESULTS:-
Fig. 4(a) Base Shear-X
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CONCLUSIONS:
- The results show that the response obtain in the form of base shear due to different earthquakes is more in case of the RCC building compare to the composite and steel building. As the base shear increases the forces in the member will increases which leads to increase in the sizes of the structural members and increase in the weight of the building.
- The drift value of the RCC building is less than the composite and steel building, also are within limit as per IS 1893 2002. As the drift values of all three buildings are within the limit specified in the code we can say that the composite and steel building shows more ductile behaviour compare to RCC building.
- The maximum top displacement of the RCC building is less than the other two buildings. The maximum top displacement of the composite and steel building are nearly same.
- The average response obtained from the five earthquake databases are compared with response of equivalent static analysis. In this also the response of the composite and steel building are nearly same which is better than the RCC building.
- The percentage increase of Time history analysis in the form of base shear, Storey drift and Maximum top displacement of RCC building is more compare to composite and steel building.
- From the results we can conclude that the composite building shows better performance compare to steel and RCC building. So in current situation of the infrastructure technology this system will become very beneficial.
- D.R. Panchal, P.M. Marathe, “Comparative Study of RCC, steel and composite (G+30 Storey) building”, Nirma University, Ahmedabad, India, International conference on current trends in technology,1-4, December2011.
- A.S. Patil and P.D. Kumbhar “Time history analysis of multistoried RCC buildings for different seismic intensities”, Department of Civil Engineering, Rajarambapu Institute of Technology, Rajaramnagar, India. International Journal of Structural and Civil Engineering Research Vol. 2, No. 3, August 2013.
- Prasad Kolhe and Prof. Rakesh Shinde, “Time history analysis of steel and composite frame structure”, Civil Engg. Dept., Pune University, Nashik, Maharashtra, India. International Journal of Innovative Research in Science, Engineering and Technology vol. 5, issue 1, January 2016.
- Cosmos Strong Ground Motion Data centre – Centre of Engineering strong ground motion database. Consortium of Organizations for Strong-Motion Observation Systems (COSMOS), University of California, Berkeley.
- ETABS-Integrated Building Design Software, “Extended 3-D analysis of the building systems”, California, Computers and structures Inc., Berkeley.
- IS 456: 2000. “Indian Standard Code of Practice for plain and reinforced Concrete”, Bureau of Indian Standards, New Delhi.
- IS 875: 1987. “Code of practice for design loads (other than earthquake) for building and structures – Part2: Imposed loads”, Bureau of Indian Standards New Delhi.
- IS 1893(Part-I) 2002: Criteria for Earthquake Resistant Design of Structures, Part-I General Provision and Buildings (Fifth Revision). Bureau of Indian Standards, New Delhi.
- R.P. Johnson, “Composite structures of steel and concrete'' Volume, Blackwell Scientific publications, UK.1994.
