Seismic Analysis of Multistoried Building and Critical Study of its Foundation

IJSTE - International Journal of Science Technology & Engineering | Volume 2 | Issue 10 | April 2016 ISSN (online): 2349-784X

Seismic Analysis of Multi-Storied Building and Critical Study of its Foundations M Ragini B.Naidu PG Student Department of Civil Engineering Yeshwantrao Chavan College of Engineering, Nagpur

Dr. S. D. Bhole Professor Department of Civil Engineering Yeshwantrao Chavan College of Engineering, Nagpur

Abstract The paper presents the study of building foundations of reinforced concrete multistoreyed buildings for G+5, G+10, G+15 designed for seismic forces in the various seismic zones of Indian subcontinent with varying SBC 100KN/m2, 150KN/m2, 200KN/m2.. The foundation types considered are; isolated footings, raft foundations under different allowable bearing pressure values of the supporting soils. The study provides the requirement of structural quantities of the building in different seismic zones. The result of the study is useful for the design professionals and cost engineers during early stages of design development and cost planning. The study also highlights the achievable economy in foundation costs through proper evaluation of allowable bearing pressure of soils through adequate geotechnical investigations of the building sites.

Keywords: Reinforced Concrete, Building Foundations, Quantity model, Seismic Design ________________________________________________________________________________________________________ I.

INTRODUCTION

Building foundation, as an interface structural component between the building and the supporting ground, perform the important function of transmitting the building loads including the wind and earthquake effects to the supporting soil strata without its shear failure or excessive settlements. At sites with potential for soil liquefaction under earthquake motions, appropriate measures in terms of suitable selection and design of foundations and/or ground improvement techniques are considered based on detailed geotechnical investigations. The selection of suitable foundation systems for multi-storied buildings are governed by several factors like; building loads, wind and earthquake effects, ground profile and water table conditions, chemically aggressive ground conditions, allowable bearing pressure of soils at different depths, provision of basement stories, proximity to adjoining buildings and other project specific requirements.

For medium rise multi-storied developments with reinforced concrete framed superstructure, depending upon the building loads and allowable bearing pressure of soils, foundations with isolated footings under the individual columns or raft/mat foundations covering the entire footprint of the building are adopted.The paper presents the quantity of building material of building foundations of reinforced concrete A multi-storied building G+5. G+10,G+15 are designed for seismic forces in the various seismic zones(zone II,zone III, zone IV, zone V) of Indian subcontinent and compared the quantity of reinforced concrete in various zone. The foundation types considered are; isolated footings and raft foundation with different allowable bearing pressure values of the supporting soils.The results of the study are useful for the design professionals and cost engineers during early stages of design development and cost planning. The study also highlights the achievable economy in foundation costs through proper evaluation of allowable bearing pressure of soils through adequate geotechnical investigations of the building sites.

Objective of this paper -

Methods of Seismic Analysis of tall RCC building Variation in design parameters by provision of foundation in the RCC building Comparisons in the values of design parameters for different foundation Propose the structurally most efficient foundation for the multi-storey RCC building II. WORK CARRIED OUT

A G+5, G+10, G+15 floors reinforced concrete building analysis is carried out using STAAD Pro V8i software. The lateral loads to be applied on the buildings are based on the Indian Standard. Building is analysed according to IS456-2008 and earthquake loading is applied as per the recommendation of IS 1893-2002.The study is performed for seismic zone II,III,IV,V as per IS 1893-2002 and foundation design is carried out for all zone with varying SBC 100KN/m2, 150KN/m2 and 200KN/m2.

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Seismic Analysis of Multi-Storied Building and Critical Study of its Foundations (IJSTE/ Volume 2 / Issue 10 / 137)

Sr No. 1 2 3 4 5 6 9 10 11 12 13

Table – 1 Details of model data of the building Description Parameter Depth of foundation 2.0 m No. of stories G +5,G+10,G+15 Type of building use Residential Floor to Floor height 3.0m Seismic zone II,III,IV,V Unit wt. of masonry wall 20 kN/m3 Thickness of slab 120 mm Thickness of outer wall 230mm Thickness of outer wall 115mm Type of steel Fe-415 Grade of concrete M-25

Fig. 1: Plan of proposed structural frame

Modelling: Building frame with the following geometrical types are considered for analysis in 4 different seismic zones (Zone II, Zone III, Zone IV and Zone V) for seismic and gravity loading in each configurations of frames.

Fig. 2: elevation of G+5 building

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Seismic Analysis of Multi-Storied Building and Critical Study of its Foundations (IJSTE/ Volume 2 / Issue 10 / 137)

Fig. 3: Elevation of G+10 building

III. RESULT Area of Steel Required for Isolated Footing for Different Sbc in G+5 Building: ZONE II III IV V

SBC=100 KN/m2 AREA OF STEEL in mm2 163072.41 201810.93 246430.19 247904.96

SBC=150 KN/m2 AREA OF STEEL in mm2 127518.17 162831.27 192383.51 199920.29

SBC=200 KN/m2 AOS mm2 103733.22 144659.30 160357.01 174571.48

reduction % 27.8817 23.9386 28.0931 24.0019

reduction % 57.2036 39.5077 53.6759 42.0077

Area of Steel Required for Isolated and Raft Foundation for Sbc 100kn/M2: ZONES II III IV V

AREA OF STEEL of isolated footing in mm2 163072.4146 201810.9346 246430.1984 247904.9623

AREA OF STEEL of raft(mm2) 131163.1773 161271.1285 163787.3074 166613.1702

REDUCTION % 24.32789294 25.13767127 50.45744525 48.79073605

Fig. 4: Comparison between raft and Isolated Footing ZONE II III IV V

quantity of conc in m3 144.250375 172.906625 178.578 184.175625

INCREASE % 19.86563293 23.79725183 27.67774434

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Seismic Analysis of Multi-Storied Building and Critical Study of its Foundations (IJSTE/ Volume 2 / Issue 10 / 137)

Fig. 5: Comparison with Different SBC

Quantity of Concrete in Raft Foundtion for G+5:

Fig. 6: Quantity of Concrete for G+5

Quantity of Concrete in Raft Foundtion For G+10 ZONE II III IV V

quantity of conc in m3 228.2468 228.2468 228.9578 242.1698

INCREASE % 0 0.31150498 6.09997733

Fig. 7: Quantity of Concrete for G+10

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Seismic Analysis of Multi-Storied Building and Critical Study of its Foundations (IJSTE/ Volume 2 / Issue 10 / 137)

Quantity of Concrete in Raft Foundtion for G+15: ZONE II III IV V

quantity of conc in m3 276.0679 285.2929 301.044 321.714

INCREASE % 3.341569532 9.047095755 16.53438489

Fig. 8: Concrete Quantity in M3 for G+15 ZONE II III IV V

QUANTITY OF CONC 127.7622 201.624 238.2306 295.1913

Quantity of Concrete in Isolated Footing for G+5 Sbc 150n/Mm2: ZONE II III IV V

QUANTITY OF CONC 91.623 150.5354 177.8375 230.0202

Quantity of Concrete in Isolated:

Fig. 10: Quantity of Concrete for G+15 sbc-100N/mm2

FOOTING FOR G+5 SBC 200N/mm2 ZONE II III IV V

QUANTITY OF CONC 71.7093 126.3104 154.1572 183.6465

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Seismic Analysis of Multi-Storied Building and Critical Study of its Foundations (IJSTE/ Volume 2 / Issue 10 / 137)

Fig. 11: Quantity of Concrete for G+5 sbc-150N/mm2

Fig. 12: Quantity of Concrete for G+5 sbc-200N/mm2

IV. OBSERVATIONS & CONCLUSIONS -

Steel required for Isolated footing is increasing as zone is increasing for different storey For sbc=100N/mm2, steel required for isolated footing is increased 24% for zone 3, 51% for zone 4, 52% for zone 5 in compare to zone2.

For sbc=150N/mm2, steel required for isolated footing is increased 28% for zone 3, 51% for zone 4, 57% for zone 5 in compare to zone2.

For sbc=200N/mm2, steel required for isolated footing is increased 39% for zone 3, 59% for zone 4, 68% for zone 5 in compare to zone2.

As sbc is inreasing from 100N/mm2 to 150N/mm2 the percentage of steel required is decreasing about 25%.

As sbc is inreasing from 100N/mm2 to 200N/mm2 the percentage of steel required is decreasing about 50%.

Area of steel required for raft foundation G+5 is incrasing by 23% for zone 3, 25% for zone 4, 27% for zone 5 in comapare to zone 2.

Area of steel required for raft foundation G+10 is incrasing by 2% for zone 4, 15% for zone 5 in comapare to zone 2.

Area of steel required for raft foundation G+15 is incrasing by 2% for zone 3, 3% for zone 4, 15% for zone 5 in comapare to zone 2.

It has been noted that area of steel for raft foundation is less than isolated footing.

There is 25% reduction in area for zone 2, zone 3 and approximate 50% reduction in area for for zone 4, zone 5.

The quantity of concrete for isolated footing is increases as zone is changing from zone 2 to zone 5 The quantity of concrete for isolated footing is reduces as the sbc is increses from 100n/mm2 to 200n/mm2.

The quantity of concrete for raft foundation is increses as zone is changing from zone 2 to zone REFERENCES

[1] [2]

V.Thiruvengadam J.C.Wason Lakshmi Gayathri,”Cost Modeling Of Reinforced Concrete Buildings Designed For Seismic Effects” 13th World Conference On Earthquake Engineering Vancouver, B.C., Canada August 1-6, 2004 Paper No. 1956 V. Thiruvengadam, J. C. Wason and K. I. Praseeda,”Cost Modeling Of Foundations Of Reinforced Concrete Buildings Designed For Seismic Effects” , 13th World Conference on Earthquake Engineering, Vancour, B. C., Canada, Paper No: 1956

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Seismic Analysis of Multi-Storied Building and Critical Study of its Foundations (IJSTE/ Volume 2 / Issue 10 / 137) [3] [4]

S.K. Ahirwar, S.K. Jain And M. M. Pande,” Earthquake Loads On Multistorey Buildings As Per Is: 1893-1984 And Is: 1893-2002: A Comparative Study” The 14th World Conference on Earthquake Engineering October 12-17, 2008, Beijing, China.

Kulkarni J.G., Kore P. N., S. B. Tanawade,”Analysis of Multi-storey Building Frames Subjected to Gravity and Seismic Loads with Varying Inertia” International Journal of Engineering and Innovative Technology (IJEIT) Volume 2,

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