Seismic Analysis of Flat Slab Building with Shear Wall

Seismic Analysis of Flat Slab Building with Shear Wall

Athira.M.V.

PG Student, Department of Civil Engineering,

Sreepathy Institute of Management And Technology, Vavanoor, Kerala, India

Sruthi K Chandran

Assistant Professor, Department of Civil Engineering,

Sreepathy Institute of Management And Technology, Vavanoor, Kerala, India

AbstractIn present construction practice flat slab systems has become widely used in reinforced concrete buildings. In RC buildings flat slab system exhibit several advantages over conventional moment resisting frames. Flat slab system reduces floor height to meet the architectural and economical demand. However, under earthquake loading, the structural effectiveness of flat slab constructions is hindered by its alleged inferior performance. Shear walls are used to resist lateral forces parallel to the plane of the wall. Large forces are generated due to seismic action resist by high in plane stiffness and strength of shear wall. Mainly to avoid the total collapse of the buildings under seismic forces, shear wall act as a flexural member. In this paper, study of 14 storey building in zone IV is considered, and is analysed with flat slab by changing various shapes of shear wall to determine different parameters like storey shear, storey displacement, storey drift and time period. Analysis is done using ETABS V.16.Software. Response spectrum analysis i.e. linear dynamic analysis is performed on the system to get the seismic behaviour.

Keywords Flat slab, Shear wall, Response spectrum analysis, Lateral loads, Storey drift

1. INTRODUCTION

   The modern trend is towards taller and slender structures and there has been a considerable increase in the construction of tall buildings both residential and commercial. In the building type of structures, the primary purpose of all kinds of structural systems is to transfer gravity loads effectively. Lateral loads like wind loads, earthquake loads and blast forces are attaining importance and every designer is facing with the problems of providing stability and adequate strength against lateral loads. Therefore, it is very important for the structure to have sufficient strength against vertical loads together with adequate stiffness to resist lateral forces.

   Without the aid of beams, solid concrete slabs of uniform depths called flat plates are transfer loads directly to the supporting columns. Today, the most commonly used slab systems used for multi-storied buildings are Flat plates. Their lack of resistance to lateral loads is the main disadvantage of Flat plates or Flat slab. Hence, in high rise constructions special features like shear walls to be provided. Shear wall can be defined as structural elements, which provide strength, stability and stiffness lateral loads deriving strength. To reduce ill-effects of twist of buildings, shear walls must be located symmetrically in plan.

   Fig.1. Shear Wall Building

2. SCOPE AND METHODOLOGY OF THE STUDY In the present paper, an attempt is made to study and

   compare the effects of earthquake on a multi storied building for different shapes of shear walls using Extended Three- dimensional Analysis of Building Systems (ETABS).

3. STRUCTURAL MODELING AND ANALYSIS Linear dynamic (Response Spectrum) analysis with

   rigid floor diaphragms used to evaluate the seismic response of multi-storey building. Etabs V.16. is used for the analysis of structure. Building situated in Seismic zone IV and soil type is II.

   1. Details of Structural Elements and Materials Used

      Grade of concrete	M35
      Grade of steel	Fe 500
      Modulus of Elasticity of steel, Es	20,0000MPa
      Modulus of Elasticity of Concrete	35000MPa
      Floor to floor height	3m
      Plinth height above GL	1.5m
      Slab thickness	200mm
      External wall	200mm
      Column	350 x 350mm
      Beam	300 x 600mm
      Live load on all floors & roof	2 4 kN/m
      Floor Finish	2 1 kN/m
      Partition load	2 1 kN/m

      Table 1 Material Properties

   2. Geometry of the Considered Model

   No. of Storeys	14
   No. of Bays in X Direction	5
   Bay Width in X Direction	6m
   No. of Bays in Y Direction	5
   Bay Width in Y Direction	6m
   Storey Height	3m

   Table 2 Model Geometry

   With the help of five different shape of shear wall studied the effectiveness of shear wall. Six models were analysed for comparing time period, lateral displacement, storey shear and storey drift.

   Fig.2 Plan and 3-D View of Proposed Building (Without Shear Wall Bare Frame)

   Fig.3 Plan and 3-D View of Model with Box Type Shear Wall

   Fig.4 Plan and 3-D View of Model with H-Shaped Shear Wall

   Fig.5 Plan and 3-D View of Model with L-Shaped Shear Wall

   Fig.6 Plan and 3-D View of Model with Straight Shear Wall

   Fig.7 Plan and 3-D View of Model with T-Shaped Shear Wall

   1. Time Period

4. RESULTS AND DISCUSSION

   Graph 1 Storey v/s Displacement

   From this study we concluded that storey displacement is less in L type shear wall. Storey shear

   Time period summarization given in below table Table 3 Time Period for Different Shear Wall

   Cases	Time Period (sec)
   Bare	2.832
   Box	0.856
   H	1.757
   L	0.699
   T	1.133
   Straight	0.770

   From this study we come to know that the time period less in L shaped shear wall.

   1. Storey Displacement

      Table 4 Storey Displacement for Different Shear Wall

      Cases		Storey Displacement(mm)
      Bare		50.020
      Box		17.232
      H	X	20.32
      	Y	26.669
      L		14.618
      T		22.918
      Straight		15.782

      maximum is observed for bare frame and H shaped shear wall.

   2. Storey Shear

      Table 5 Storey Shear for Different Shear Wall

      Cases	Storey Shear(kN)
      Bare	3567.60327
      Box	10844
      H	9155.3655
      L	12512
      T	11737
      Straight	8145.9031

      Graph 2 Storey v/s Storey Shear

   3. Storey Drift

      Tale 6 Storey Drift for Different Shear Wall

      Cases	Storey Drift
      Bare	0.001763
      Box	0.000478
      H	0.000766
      L	0.000409
      T	0.000449
      Straight	0.000658

      Graph 3 Storey v/s Storey Drift

5. CONCLUSION

In this paper the study is carried out according to the earthquake code book IS 1893[PART I] 2002 and analysis is carried out by taking regular plan of building [G+14] on medium soil [TYPE II] and ZONE IV is done by linear dynamic with different shear walls. A comparison is carried out to determine the optimum position of shear wall.

The following are the conclusion taken in this paper.

1. The bare frame gives more displacement, time period and storey drift compared to other shapes of shear wall. Hence, the presence of shear wall is possible of controlling the damage that may occur due to earthquake force.

2. Time period comparison gives the L shaped shear wall is better shape than others.

3. From the comparison of storey displacement values L shaped shear wall indicate lesser displacement and then better one is straight shear wall.

4. Storey displacement value obtained from the analysis indicates that L shape obtained least value then better one is T shaped shear wall.

5. Storey shear maximum for L shaped and T shaped.

6. Structure with L shaped shear wall is suitable for the effect of earthquake load on the performance of building.

REFERENCES

1. IS 1893 (part 1) (2002) Indian Standard Criteria for Practice for Earthquake Resistant Design of Structures General Provisions and Buildings (Fifth Revision).

2. M A Rahman (2012), Effects of openings in shear wall on seismic response of structures, International Journal of Computer Applications, Volume 59, December 2012.

3. Navyashree K (2014), Use of flat slabs in multi-storey commercial building situated in high seismic zone, International Journal of Research in Engineering and Technology, Volume 03, August 2014.

4. M Santhosh ((2014), Seismic analysis and design of multi-storey building with non-parallel shear wall system, International Journal of Engineering and Management Research, Volume 04, April 2014.

5. G S Hiremath (2014), Effect of change in shear wall location with uniform and varying thickness in high rise building, International Journal of Science and Research, Volume 03, October 2014.

6. Lakshmi K O (2014), Effect of shear wall location in buildings subjected to seismic loads, ISOI Journal Engineering and Computer Science, Volume 01, December 2014.

7. Sachin P Dyavappanavar (2015), Seismic analysis of RC multi-storied structures with shear walls at different locations, International Research Journal of Engineering and Technology, Volume 02, Aug- 2015.

8. Aneeket T Patil (2016), Behaviour of multi-storey building under the effect of wind and earthquake for different configuration of shear wall, Journal of Civil Engineering and Environmental Technology, Volume 3, April-June, 2016.