Seismic Response of Multistory Flat Slab Building with and without Shear Wall

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Seismic Response of Multistory Flat Slab Building with and without Shear Wall

Sameer Bunkar1, Siddharth Pastariya2

1 M.Tech Scholar, Department of Civil Engineering, Sri Aurobindo Institute of Technology Indore M.P

2Assistant Professor, Department of Civil Engineering, Sri Aurobindo Institute of Technology Indore M.P

Abstract: In present scenario the analysis of flat slab is more composite and also is significant to study the behavior against different forces acting on the components of a multistoried building. The analysis may be carried out using software like Stadd Pro, Etabs etc. In this research work to compare the behavior of multi-storeyed building of conventional R.C.C., having flat slab with or without shear walls and to analyze the effect of building height on the performance under sesmic forces. In flat slab building the affect of shear wall (with & without) on seismic behavior with different thickness and different position of shear wall are considered. For this, G+9, G+18, G+27 and G+36 Storeyed models, the plan size 20X20m are chosen. For calculating different parameters, shear wall are provided at different location. To study the effect of different location of shear wall on flat slab multi-storey building, static analysis (Equivalent Static Analysis) in software STAAD Pro is carried out for zone V. The seismic parametric studies comprise of lateral displacement, storey drift, drift reduction factor and contribution factor.

I. INTRODUCTION

One of the major problems in the modern construction world is the problem of vacant land. This scarcity in urban areas has led to the vertical construction growth of low-rise, medium-rise, tall buildings and even sky-scraper (over 50 meters tall). These buildings generally used Framed Structures subjected to the vertical as well as lateral loads. In these structures, the lateral loads from strong winds and earthquakes are the main concerns to keep in mind while designing rather than the vertical loads caused by the structure itself. These both factors may be inversely proportional to each other as the building which is designed for sustaining vertical loads may not have the capacity to sustain or resist the above mentioned lateral loads. The lateral loads are the foremost ones as they are in contrast against one another as the vertical loads are supposed to increase linearly with height; on the other hand lateral loads are fairly variable and increase rapidly with height. For buildings taller than 15 to 20 stories, pure rigid frame system is not adequate because it does not provide the required lateral stiffness and causes excessive deflection of the building. These requirements are satisfied by two ways. Firstly, by increasing the members size above the requirements of strength but this approach has its limitation and secondly, by changing the structural form into more stable and rigid to restrict deformation. This increases the structures stability and rigidity and also restricts the deformation requirement.

  1. METHDOLOGY & MODELLINGFor the different combinations of loading conventional R.C.C flat slab structure with & without shear wall at particular locations are modeled & analyzed. Now compare between conventional R.C.C flat slab structure and flat slab R.C.C. structure with shear walls situated in seismic zone V. Following cases of building are as follows:

    Case 1: Conventional R.C.C. structure without shear wall. Case 2: Conventional R.C.C. structure with Flat slab.

    Case 3: Shear wall core type with flat slab (Placings-1). Case 4; Shear wall core type with flat slab (Placings-2). Case 5: C shaped shear wall with flat slab (Placings-1). Case 6: C shaped shear wall with flat slab (Placings-2). Case 7: L shaped shear wall at corners with flat slab.

    Case 8: Parallel shear wall along periphery with flat slab. Case 9: Non-Parallel shear wall along periphery with flat slab. Case 10: + shaped shear wall at center with flat slab.

    Case 11: E Shaped shear wall with flat slab (Placings-1). Case 12: E Shaped shear wall with flat slab (Placings-2).

    with shear wall

    Fig. 1 3-D View ofFig. 2 3-D View ofFig. 1 3-D View of
    Conventional RCCFlat slab structureFlat slab structure
    Structure
  2. RESULT & DISCUSSION
    1. Fundamental Natural Period: The approximate fundamental natural period of vibration (Ta), in seconds, of a moment- resisting frame building may be calculated to maximum values in comparison of different height of building with different frames is computed as :-Ta = 0.075 h0.75for RC buildings with beams.

      Ta = 0.09/ d 0.5for RC buildings without beams.

      S

      n o.

      Height Of Building (m)No. of Store yConventional Bare Frame StructureFlat Slab Structure sFlat Slab With Different Shear Wall Placings
      (Frame 1)(Frame 2)(Frame 3)(Frame 4)
      129.890.9560.5990.5990.599
      258.6181.5881.17931.17931.1793
      387.4272.41381.75891.75891.7589
      4116.2362.65442.33852.33852.3385
      S

      n o.

      Height Of Building (m)No. of Store yFlat Slab With Different Shear Wall Placings
      (Frame 5)(Frame 6)(Frame 7)(Frame 8)
      129.890.5990.5990.5990.599
      258.6181.17931.17931.17931.1793
      387.4271.75891.75891.75891.7589
      4116.2362.33852.33852.33852.3385
      S

      n o.

      Height Of Building (m)No. of Store yFlat Slab With Different Shear Wall Placings
      (Frame 9)(Frame 10)(Frame 11)(Frame 12)
      129.890.5990.5990.5990.599
      258.6181.17931.17931.17931.1793
      387.4271.75891.75891.7589.7589
      4116.2362.33852.33852.33852.3385
      1. Natural Time Period (second)3

        2.5

        2

        1.5

        1

        0.5

        0

        9 Storey 18 Storey 27 Storey 36 Storey

        Frame 1 Frame 2 Frame 3 Frame 4

        Frame 5 Frame 6 Frame 7 Frame 8

        Frame 9 Frame 10 Frame 11 Frame 12

        (B). Average Response Acceleration Coefficient (Sa/g) :-Average response accelerationcoefficient is a factor denoting the acceleration response spectrum of the structure subjected to earthquake ground vibrations, and depends on natural period of vibration and damping of the structure to maximum values in comparison of different height of building with different frames is computed as :-

        Sno.Height Of Building (m)No. Of StoreyConventional Bare Frame StructureFlat Slab StructuresFlat Slab With Different Shear Wall Placings
        (Frame 1)(Frame 2)(Frame 3)(Frame 4)
        129.891.4222.272.272.27
        258.6180.8561.1531.1531.153
        387.4270.5630.7730.7730.773
        4116.2360.5120.5820.5820.582
        Sno.Height Of Building (m)No. Of StoreyFlat Slab With Different Shear Wall Placings
        (Frame 5)(Frame 6)(Frame 7)(Frame 8)
        129.892.272.272.272.27
        258.6181.1531.1531.1531.153
        387.4270.7730.7730.7730.773
        4116.2360.5820.5820.5820.582
        Sno.Height Of Building (m)No. Of StoreyFlat Slab With Different Shear Wall Placings
        (Frame 9)(Frame 10)(Frame 11)(Frame 12)
        129.892.272.272.272.27
        258.6181.1531.1531.1531.153
        387.4270.7730.7730.7730.773
        4116.2360.5820.5820.5820.582
      2. Average Response Acceleration Coefficient2.5 (Sa/g)

        2

        1.5

        1

        0.5

        0

        St

        St

         

        18

        18

         

        9 oFrreayme 1 FrSatmoere2y

        Fra2m7eSt3or

        ey

        ey

         

        Frame346 Storey

        Frame 5 Frame 6 Frame 7 Frame 8

        Frame 9 Frame 10 Frame 11 Frame 12

        (C).Base Shear:- The total design lateral forces or design seismic base shear (Vb) along any principal direction to maximum values in comparison of different height of building with different frames shall be determined by the following expression :-

        (Frame 5)

        (Frame 6)

        (Frame 7)

        (Frame 8)

        (m)
        129.891302.0731302.0731589.0221589.022
        258.6181315.2981315.2981601.9071601.907
        387.4271320.3251320.3251606.9321606.932
        4116.2361322.861322.861609.4661609.466
        Sno. Height OfNo. Of StoreyFlat Slab With Different Shear Wall Placings

        (Frame 5)

        (Frame 6)

        (Frame 7)

        (Frame 8)

        (m)
        129.891302.0731302.0731589.0221589.022
        258.6181315.2981315.2981601.9071601.907
        387.4271320.3251320.3251606.9321606.932
        4116.2361322.861322.861609.4661609.466
        Sno. Height OfNo. Of StoreyFlat Slab With Different Shear Wall Placings

         

        Vb= AhW

        (Frame 1)

        (Frame 2)

        (Frame 3)

        (Frame 4)

        Sno.Height Of BuildingNo. Of StoreyConventional Bare Frame StructureFlat Slab StructuresFlat Slab With Different Shear Wall Placings
        (m)
        129.892497.9091015.1231445.5471445.5
        258.6183181.7851028.6891458.6021458.602
        387.4273050.621033.7181463.6291463.629
        4116.2363688.971036.2541466.1631466.163
        Sno.Height Of BuildingNo. Of StoreyFlat Slab With Different Shear Wall Placings
        Building (m)
        (Frame 9)(Frame 10)(Frame 11)(Frame 12)
        129.891302.0731302.0731373.811373.81
        258.6181315.2981315.2981386.951386.95
        387.4271320.3251320.3251391.9771391.977
        4116.2361322.861322.861394.5121394.512

        4000

      3. Base Shear (Vb)=Ah x W (KN)3000

        2000

        1000

        0

        9 Storey 18 Storey 27 Storey 36 Storey

        Frame 1 Frame 2 Frame 3 Frame 4

        Frame 5 Frame 6 Frame 7 Frame 8

        Frame 9 Frame 10 Frame 11 Frame 12

        (D).Sway (mm):- Storey is the space between two adjacent floor and sway is the displacement of one level relative to the other level above or below according to maximum values in comparison of different height of building with different frames is computed as :-

        Sno.Height Of Building (m)No. Of StoreyConventional Bare Frame StructureFlat Slab StructuresFlat Slab With Different Shear Wall Placings
        (Frame 1)(Frame 2)(Frame 3)(Frame 4)
        129.89969.117269.66551.06345.468
        258.6182551558.223171.984145.822
        387.4273740.156899.449380.564353.549
        4116.2366303.6581306.101749.87732.193
        Sno.Height Of Building (m)No. Of StoreyFlat Slab With Different Shear Wall Placings
        (Frame 5)(Frame 6)(Frame 7)(Frame 8)
        129.89107.785107.78552.67450.13
        258.618284.661335.081191.481168.205
        387.427710.428710.428421.848347.498
        4116.2361413.9711413.971749.947588.376
        Sno.Height Of Building (m)No. Of StoreyFlat Slab With Different Shear Wall Placings
        (Frame 9)(Frame 10)(Frame 11)(Frame 12)
        129.8978.16452.602108.763120.121
        258.618339.499169.427350.573391.01
        387.427773.819361.885697.144701.344
        4116.2361295.04643.8481407.691807.018

        7000

        6000

        5000

        4000

        3000

        2000

        1000

        0

      4. Sway (mm)9 Storey 18 Storey 27 Storey 36 Storey

        Frame 1 Frame 2 Frame 3 Frame 4

        Frame 5 Frame 6 Frame 7 Frame 8

        Frame 9 Frame 10 Frame 11 Frame 12

        1. Shear Force (KN) :-Shear force at a section of a beam is defined as algebraic sum of all the forces acting on one side of the section. Calculated value of shearing forces according to different variations in storey height with different frames is computed as:-
          Sno.Height Of Building (m)No. Of StoreyConventional Bare Frame StructureFlat Slab StructuresFlat Slab With Different Shear Wall Placings
          (Frame 1)(Frame 2)(Frame 3)(Frame 4)
          129.89254.01394.51256.40854.564
          258.618310.311108.573150.08174.039
          387.427344.688131.487198.143138.468
          4116.236328.392152.674312.216222.337
          Sno.Height Of Building (m)No. Of StoreyFlat Slab With Different Shear Wall Placings
          (Frame 5)(Frame 6)(Frame 7)(Frame 8)
          129.8952.95452.95454.3459.586
          258.61884.922106.132113.821152.01
          387.427217.78-217.78206.693272.78
          4116.236-317.431317.431305.396387.594
          Sno.Height Of Building (m)No. Of StoreyFlat Slab With Different Shear Wall Placings
          (Frame 9)(Frame 10)(Frame 11)(Frame 12)
          129.8949.93944.94462.00146.393
          258.618118.31781.338112.42667.257
          387.427224.402125.738213.636134.209
          4116.236338.717204.499329.981210.785

          (E) Shear Force (KN)

          (E) Shear Force (KN)

           

          500

          400

          300

          200

          100

          0

          500

          400

          300

          200

          100

          0

           

          9 Storey

          18 Storey

          27 Storey

          36 Storey

          9 Storey

          18 Storey

          27 Storey

          36 Storey

          Frame 1 Frame 2 Frame 3 Frame 4

          Frame 5 Frame 6 Frame 7 Frame 8

          Frame 9 Frame 10 Frame 11 Frame 12

          Frame 1 Frame 2 Frame 3 Frame 4

          Frame 5 Frame 6 Frame 7 Frame 8

          Frame 9 Frame 10 Frame 11 Frame 12

           

        2. Moment (KN-m) :-Bending Moment at a section of a beam is defined as algebraic sum of the moment of all the forces acting on one side of the section. Calculated value of Bending Moment according to different variations in storey height with different frames is computed as:-
          Sno.Height Of Building (m)No. Of StoreyConventional Bare Frame StructureFlat Slab StructuresFlat Slab With Different Shear Wall Placings
          (Frame 1)(Frame 2)(Frame 3)(Frame 4)
          129.89442.807158.62594.50591.464
          258.618544.546174.539255.285131.355
          387.427552.783211.171357.167254.303
          4116.236650.348244.955558.557407.479
          Sno.Height Of Building (m)No. Of StoreyFlat Slab With Different Shear Wall Placings
          (Frame 5)(Frame 6)(Frame 7)(Frame 8)
          129.8993.84993.84991.686100.05
          258.618-155.21218.851-197.566-271.523
          387.427376.815-376.815-365.796-486.797
          4116.236583.193-583.193540.386691.78
          Sno.Height Of Building (m)No. Of StoreyFlat Slab With Different Shear Wall Placings
          (Frame 9)(Frame 10)(Frame 11)(Frame 12)
          129.8988.02379.166101.73579.337
          258.618199.219-131.045-207.66124.343
          387.427-382.425-211.67-398.124247.654
          4116.236573.379-343.31-613.069-389.67

          (F) Moment (KN-m)

          800

          600

          400

          200

          0

          9 Storey 18 Storey 27 Storey 36 Storey

          Frame 1 Frame 2 Frame 3 Frame 4

          Frame 5 Frame 6 Frame 7 Frame 8

          Frame 9 Frame 10 Frame 11 Frame 12

        3. Axial Force (KN) :-In an axial-force member, the stresses and strains are uniformly distributed over the cross section. Hence for the calculation of the axial forces in member we have to consider forces in x-z plane when upward global direction is y.Calculated value of axial-force according to different variations in storey height with different frames is computed as:-
          Sno.Height Of Building (m)No. Of StoreyConventional Bare Frame StructureFlat Slab StructuresFlat Slab With Different Shear Wall Placings
          (Frame 1)(Frame 2)(Frame 3)(Frame 4)
          129.895641.6086383.9435866.2355858.292
          258.61811766.9512434.689238.98810083.79
          387.42716995.9217607.2313883.6513757.37
          4116.23621316.5322244.1417363.0917258.35
          Sno.Height Of Building (m)No. Of StoreyFlat Slab With Different Shear Wall Placings
          (Frame 5)(Frame 6)(Frame 7)(Frame 8)
          129.895906.7655906.7656418.136411.928
          258.61810722.231072212233.9312014.82
          387.42714737.0414737.0416519.4415919
          4116.23618484.0718484.0719728.8418792.54
          Sno.Height Of Building (m)No. Of StoreyFlat Slab With Different Shear Wall Placings
          (Frame 9)(Frame 10)(Frame 11)(Frame 12)
          129.896403.5975830.9595814.0395770.324
          258.61812330.159474.26110384.1310293.29
          387.42716972.3112804.0914234.2214179.22
          4116.23620674.6316045.617893.8317043.28

          (G) Axial Force (KN)

          25000

          20000

          15000

          10000

          5000

          0

          9 Storey 18 Storey 27 Storey 36 Storey

          Frame 1 Frame 2 Frame 3 Frame 4

          Frame 5 Frame 6 Frame 7 Frame 8

          Frame 9 Frame 10 Frame 11 Frame 12

          (G) Axial Force (KN)

          25000

          20000

          15000

          10000

          5000

          0

          9 Storey 18 Storey 27 Storey 36 Storey

          Frame 1 Frame 2 Frame 3 Frame 4

          Frame 5 Frame 6 Frame 7 Frame 8

          Frame 9 Frame 10 Frame 11 Frame 12

        4. Torsion (KN-m) :-Torsion, also known as torque, describes a moment that is acting upon an object around the same axis in which the object lies. A moment is a measurement of the propensity of a force to create motion around either a point or an axis, and is calculated as the force upon the object multiplied by the distance of the force from the chosen origin. Calculated value of torqueaccording to different variations in storey height with different frames is computed as:-
        Sno.Height Of Building (m)No. Of StoreyConventional Bare Frame StructureFlat Slab StructuresFlat Slab With Different Shear Wall Placings
        (Frame 1)(Frame 2)(Frame 3)(Frame 4)
        129.895.2980.1520.2380.234
        258.6188.3190.1540.1730.184
        387.4279.2650.1550.2040.23
        4116.23610.6160.1720.2670.386
        Sno.Height Of Building (m)No. Of StoreyFlat Slab With Different Shear Wall Placings
        (Frame 5)(Frame 6)(Frame 7)(Frame 8)
        129.891.7361.7360.3450.185
        258.6182.682.370.3090.14
        387.4272.4622.4620.3020.238
        4116.2362.3412.3410.3750.336
        Sno.Height Of Building (m)No. Of StoreyFlat Slab With Different Shear Wall Placings
        (Frame 9)(Frame 10)(Frame 11)(Frame 12)
        129.890.5680.1971.7221.929
        258.6181.430.192.5122.887
        387.4272.3340.2382.5942.989
        4116.2363.0150.3032.4291.764

        (H) Torsion (KN-m)

        25000

        20000

        15000

        10000

        5000

        0

        9 Storey 18 Storey 27 Storey 36 Storey

        Frame 1 Frame 2 Frame 3 Frame 4

        Frame 5 Frame 6 Frame 7 Frame 8

        Frame 9 Frame 10 Frame 11 Frame 12

        (H) Torsion (KN-m)

        25000

        20000

        15000

        10000

        5000

        0

        9 Storey 18 Storey 27 Storey 36 Storey

        Frame 1 Frame 2 Frame 3 Frame 4

        Frame 5 Frame 6 Frame 7 Frame 8

        Frame 9 Frame 10 Frame 11 Frame 12

  3. CONCLUSION Based on the result following conclusion are drawn::

(A) The natural time period increases as the height of the building increases, since the values are represented by the help of tabular graphs, concluding that all the frames are having same values for different storey computations, it increases according to height though the major change is increased value of Frame 1 only.

  1. Average Response Acceleration Coefficient (Sa/g) decreases as the height of the building increases, since the values are represented by the help of tabular graphs, concluding that all the frames are having same values for different storey computations; it decreases according to height though the major change is decreased value of Frame 1 only.
  2. Design seismic base shear (Vb) is high in Frame 1 only and low in Frame-2 though there is a slight change in the values of different storey. The high base shear case is of 36 storey Frame 1 and the low base shear is of 9 storey frame 2.

(D) The values of Sway is clearly said that if moving towards the high storey buildings there is always sway though this paper concludes that if we are providing a structure according to frame 1 there is a lot of sway. Contrasting to this value having a minimum value from all the results in a particular storey is of sway in Frame 4.

  1. Shear force is increasing according to the height of the structure. Hence the maximum value is seen in 36 storey frame 8 and the minimum value is of 36 storey Frame 2.
  2. The Bending Moment seems to be maximum in 36 storey building. Frame 8 having the maximum values and frame 2 is having the minimum values of Moment.

(G) Axial force is also increasing on comparing the storey of different height. The maximum value is seems overall to be frame 2 and its minimum value seems to be frame 10.

(H) Last but not the least the important value used in the analysis is the value of Torsion i.e. the applied torque. Values also conclude that if moving towards more floors, there is always a greater value of torsion.Maximum value seems to be in Frame 2 and the minimum value seems to be in Frame 10.

ACKNOWLEDGEMENT

We do extremely thankful and respectful to our guide Prof. Siddharth Pastariya, Assistant Professor, Department of Civil Engineering, Sri Aurobindo Instiute of Technology, Indore (M. P.); that he always points to critical insights during the entire work, guides us, helps us discover the fun of devising the state of the art solutions.

REFRENCES

  1. Apostolska R P, Necevska-Cvetanovska G S, Cvetanovska J P and Mircic N (2008), Seismic performance of flat-slab building structural systems, The 14th World Conference on Earthquake Engineering October 12-17, 2008, Beijing, China.
  2. Bothara S D and Varghese V (2012), Dynamic analysis of special moment resisting frame Building with flat slab and grid slab, , pp. 275-280.
  3. Erberik M A and Elnashai S A (2004), Fragility analysis of flat-slab structures, Vol. 26, pp. 937948.
  4. Makode R K, Akhtar S and Batham G (2014), Dynamic analysis of multi-storey RCC building frame With flat slab and grid slab, , pp. 416-420.
  5. Mohamed A A El-shaer (2013), Seismic Load Analysis of different RC Slab Systems for Tall Building, INPRESSCO, Vol. 3, No. 5.
  6. Navyashree K and Sahana T S (2014), Use of flat slabs in multi-storey commercial building situated in high seismic zone,Vol. 03, No. 08, IJRET:
  7. Sable K S, Ghodechor V A and Khandekar S B (2012), Comparative Study of Seismic Behaviour of multi-storey flat slab and conventional reinforced concrete framed structures, International Journal of Computer Technology and Electronics Engineering, Vol. 2, No. 3

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