Comparitive Study of Seismic Analysis Between Conventional and Flat Slab with Drop and without Drop Framed Structures with Different Masonary Infills

Comparitive Study of Seismic Analysis Between Conventional and Flat Slab with Drop and without Drop Framed Structures with Different Masonary Infills

M Vinod Kumar Reddy [1],

Post Graduate Student,

JNTUA College of Engineering Anantapuramu, Anantapuramu,

Andra Pradesh, India, 515002

Dr. Vaishali G Ghorpade [2]

Assosiate Professor,

JNTUA College of Engineering Anantapuramu, Anantapuramu,

Andra Pradesh, India, 515002

Abstract:-Most of the high-rise buildings in India consist of moment resisting frames with brick infill. But the brick infill is a non-structural element and therefore all the lateral load is assumed to be resisted by the frame. A brick infill is brittle when compared with reinforced concrete frame and fails in an earthquake, the lateral failure can be controlled by using masonry infill such as shear wall, strut and Bracings etc.

If the structure is suitably designed, the infill can increase overall strength, lateral resistance and energy dissipation of the structure; and these infill reduces lateral deflections and bending moments in the frame, thereby decreasing the probability of collapse. Hence, accounting for the infill in analysis and design leads to slender frame members, reducing the overall cost of the structural system. Designers often neglect the structural contribution of infill, codes of practice, which do not recognize the effect of infill panels, recommended that the base shear be calculated based on the natural period of frame alone. Besides being unrealistic, such an approach can lead to unsafe design, because frame members receive unintended shear and axial force.

Flat slab structures are one of the most popular floor systems in commercial buildings, residential buildings and many other structures. The Flat slab framed structures are favored by both architecture and client. In conventional framed structures slab is resting on the beams, forces is transferred from slab to beams and then beams to columns. But in Flat slab framed structures forces is transferred from slab to the columns directly. By using the masonry infill we can overcome lateral failure in the multistory buildings during earthquake.

1. BUILDING CONFIGURATION:

   The present study is an attempt to study the comparative seismic analysis of conventional, flat slab with drop and without drop framed structures with and without masonry infill wall using ETABS software. The parameters studied are Fundamental natural period, Design Base shear, Displacements and Story Drift for different types of building with and without Masonry infill wall.

   Keywords: E-Tabs, Flat Slabs, Infill walls, Conventional slabs, Base Shear, Story drift, Time Period.

   1. INTRODUCTION:

      Reinforcement concrete is the major construction material in all civil engineering structures. Earthquake resistance design of these RC structures is a continuous area of research since the earthquake engineering has started. The structures still damage due to one or more reasons during Earthquakes. The reasons to damage the structure either code imperfections or errors in analysis and design. The structural configuration system has played a vital role Earthquake resistance design.

      Size of Bracing	230*300 mm	230*300 mm
      Size of Shear Wall	230 mm	230 mm
      width	30 m	36 m
      Length	30 m	36 m

      Figure 2.1 Plan of building

      Figure 2.2 Model of building without Masonry

      Infill Wall

      Figure 2.3 Model of building with struct

      Figure 2.4 Model of building with shear wall

      Equivalent Diagonal Struct can be calculated by using the formula:

      Where, h =Length of contact between the wall and column.

      Figure 2.5 Model of building with X-bracing

      beam.

      L = Length of the contact between the wall and

2. Loading:

   Live load	4 kN/m²
   Floor finish	1.5 kN/m²
   Wall weight	13.8 kN/m
   	6.9 kN/m on roof
   Seismic loading:	IS 1893
   Zone factor	0.24 (zone IV)
   Soil type	II
   Importance factor	1.5
   Response reduction, R	5
   Ecc. Ratio	0.05
   Wind loading:	IS 875
   Wind speed	39 m/s
   Risk coefficient K1	1
   Terrain category type K2	4
   Topography K3	1.05

3. Type of masonry infill:

   1. Equivalent Diagonal Struct

   2. Bracing System

   3. Shear Wall

      W= Width of the strut

      A member in which the relative displacement is effectively prevented by bracings. To resist the torsional effect of wind and earthquake forces, bracings in plan should be provided and integrally connected with the longitudinal and transverse bracings, to impart adequate torsional resistance to the structure.

      A Shear Wall is a wall that is designed to resist shear, the lateral force that causes the bulk of damage in Earth Quakes. In Multi story structures, Shear walls are critical, because in addition to preventing the failure of exterior walls, they also support the multiple floors of the building, ensuring that they do not collapse as a result of lateral movement in an earthquake.

   4. RESULTS AND DISCUSSIONS:

The study examines the performance of multistory buildings with different slabs like Flat slab framed structures and conventional framed structures with different masonry infills such as Equivalent diagonal strut, bracing system, shear wall systems. In this present study the dynamic analysis of different framed structures is done by response spectrum method.

Model 1: Structure without masonry infill

Model 2: Structure wih considering Equivalent Diagonal Struct

Model 3: Structure with considering Shear wall Model 4: Structure with considering Bracing system Displacement:

Table 5.1. Maximum Displacement for Different types of buildings

Fig 5.1. Maximum Displacement for different type of buildings without and with infill wall.

Base Shear:

Table 5.2 Design base shear for different type of buildings.

Fig 5.2 Design base shear for different type of buildings without and with infill wall.

Time Period:

Fig 5.3 Fundamental Natural Period for different type of Buildings without and with infill wall.

Story Drift:

Fig 5.4 Maximum story drift for different type of buildings Without and with infill wall

6. CONCLUSION AND DISCUSSIONS:

1. By observing the above results the displacement of the structure is varies with varying the slab system and masonry infill system. The displacement of the flat slab with drop structures are having more deflection than conventional and flat slab with drop framed structures. Model 1 is 22 % higher than model 2, 38% higher than the model 3, 25% higher than the model 4

2. Base shear of the conventional framed structures are having more than Flat slab with drop and without drop framed structures. Conventional framed structures are having 7% more base shear than Flat slab with drop framed structures and 16% more than flat slab without drop framed structures, the structure with shear wall is having more Base shear than the structures having with struct and bracing.

3. Flat slab without drop framed structures are having more Time period than the conventional and flat slab with drop framed structures, without masonry infil structures are having more Time period than the with masonry infill structures.

4. Story drift is decreased by using the masonry infill, story drift is higher in structures having without masonry infill than with masonry infill structures

7. REFERENCES:

1. Bureau of Indian Standards: IS-875, part 1 (1987), Dead Loads on Buildings and Structures, New Delhi, India.

2. Bureau of Indian Standards: IS-875, part 2 (1987), Live Loads on Buildings and Structures, New Delhi, India.

3. Bureau of Indian Standards: IS-1893, part 1 (2002), Criteria for Earthquake Resistant Design of Structures: Part 1 General provisions and Buildings, New Delhi, India.

4. H.-S. Kim, D.-G. Lee. 2004. Efficient analysis of flat slab structures subjected to lateral loads.

5. Ema Coelho, Paulo Candeias, Giorgios Anamateros, Raul Zaharia, Fabio Taucer, Artur V. PINTO. 2004. Assessment of the seismic behaviour of RC flat slab building structures.

6. Vancouver, B.C., Canada. 2004. Efficient Seismic Analysis of Flat Plate System Structures.

7. R. P. Apostolska, G. S. Necevska-Cvetanovska, J. P. Cvetanovska and N. Mircic. 2008. Seismic performance of flat-slab building structural systems.

8. Sang-Whan Han, Ph.D., P.E.; Young-Mi Park; and Seong- Hoon Kee. Stiffness Reduction Factor for Flat Slab Structures under Lateral Loads.

9. Youngmi Park, Jaok Jo, Seungyong Oh, Sangwhan Han. A modified equivalent frame method under lateral loads.

10. George Lin. Stability of Column Supporting Flat Slab Without Beam Grid