Comparision of IS-875(Part 3)1987 and IS-875(Part 3)2015 for Tall Junction Tower

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Comparision of IS-875(Part 3)1987 and IS-875(Part 3)2015 for Tall Junction Tower

Comparision of IS-875(Part 3)1987 and IS-875(Part 3)2015 for Tall Junction Tower

Thejaswini I M1

1Student,

Department of Civil Engineering, Sri Siddhartha Institute of Technology,

Tumakuru, Karnataka, India

Sowjanya G V3

3Assistant Professor, Department of Civil Engineering,

Sri Siddhartha Institute of Technology, Tumakuru, Karnataka, India

Sudharshan B S2

2Professional Structural Engineer STAC Consultants, Bangalore, Karnataka, India

Abstract:- Intention of the present work to compare the behavior of junction tower build for the material handling purposes in thermal power plant when applied with wind load based on IS-875(part 3)1987 and IS-875(PART 3)2015. The loads are applied based on IS-875 (part 3) 1987 and IS-875(part 3)2015 was applied separately. The design in both the cases was performed using the codal provisions and standards of IS 800- 1984(working stress method). The results (design, sway) in both the cases were compared.

I. INTRODUCTION

The junction towers are the supporting structures which are constructed to provide a support for the belt conveyors to convey the material to the power generation point in thermal power plant. It is built mainly for the intension to turn the material conveyor belt on particular degree in the industry. The change of direction is achieved by way of dropping the material from upper level to lower level of conveyor running in different direction. The junction towers also facilitates in transferring one belt conveyor to other belt conveyor going in two or more direction. The junction tower also accommodates horizontal and vertical gravity take up in order to maintain the belt tension as per the design requirements. It also houses Dust Extraction System, screw conveyor Inline Magnetic Separators, Cranes / Monorails etc.

2. OBJECTIVES

  1. To perform the analysis and design of junction tower based on IS-875(part 3)1987 and IS-875(part 3)2015 for both coastal and non coastal zones and compare the quality of steel required in each condition.

  2. To find the percentage of members that do not satisfy the codal provisions of IS-875(part 3)2015 but satisfy 1987.

  3. To find what type of members that does not satisfy the codal requirements of 2015 version that satisfied in 1987 version.

  4. To find the additional quantity of steel required to satisfy the codal provision of IS-875(part 3)2015.

  5. To compare the maximum sway in both orthogonal directions as per IS-875(part 3)1987 and IS-875(part 3)2015.

  6. To determine the additional quantity of steel required to satisfy the sway requirements of junction tower analyzed and designed as per IS-875(part 3)2015.

3. BUILDING DETAILS

Junction tower is composed of structural steel members braced in both framing directions. It is provided wherever conveyor gallery changes its direction. The tower dimension is 14m×14m with 75m height. The maximum allowable sway according to codal provisions of design is h/1000(i.e 75m). The support provided was hinged support. It is assumed that the structure is cladded on all sided.

TABLE NO: 1 BUILDING DETAILS

MODEL

Structure

Steel Structure

Building Dimension

14mx14m

Height

75m

Number Of Floors

6

Floor finish

R.C floor

Roof Finish

R.C roof

Cladding

C G I

Number of conveyors

2

Location of conveyor

EL @54 , EL@ 66

Y

X

Z

FIG 1 3D VIEW IN STAAD.pro

Load Cases

  1. Dead Load

  2. Live Load

4. LOADS CONSIDERED

PZ according to IS-875(PART 3) 2015

The design wind pressure at any height above mean ground level shall be obtained by the following relationship between wind pressure and wind velocity:

PZ = 0.6 ×VZ2

  1. Wind load at +Z direction

  2. Wind load at – Z direction

  3. Wind load at +X direction

  4. Wind load at – X direction

  5. Wind load at internal pressure WLIP

  6. Wind load at internal pressure WLIS

    Dead load and live load have been taken as per IS 875 (part 1)1987 and IS 875(part 2)1987 respectively. The following are the loads considered for design.

    • Self weight of the structural members

    • Cladding

    • Conveyor

    • Staircase

Wind load: IS-875(PART 3)

The basic wind speed (Vb) of 50m/sec at a different height above the ground level is considered.

Design wind velocity VZ = Vb x k1 x K2 x k3 Vz = design wind speed at any height z in m/s; Vb = 33 m/sec(non-coastal zone)

Vb = 50 m/sec(coastal zone)

K1= 1.05(non-coastal zone), 1.08(coastal zone) K2 =

Height(m)

K2

1987

2015

0-6

0.99

1.05

6-18

1.03

1.09

18-24

1.06

1.12

24-30

1.09

1.15

30-54

1.14

1.20

54-75

1.20

1.26

TABLE NO:2 Height Factor for IS-875(1987) and IS-875(2015)

Where

PZ = design wind pressure in N/ms at height z, and VZ = design wind velocity in m/s at height

The design wind pressure Pd can be obtained as

Pd = Kd × Ka × Kc × Pz

Kd = wind directionality factor, Ka = area averaging factor, and Kc = combination factor

Kd = 0.9(non coastal), 1.0(coastal) Ka =1.0

Kc = 0.9

TABLE NO:4 PZ and VZ values for IS-875(2015)

Height (m)

Non coastal zone

Coastal zone

vz(m/s)

Pz(kN/m2)

vz(m/s)

Pz(kN/m2)

0-6

45.05

1.22

73.71

3.26

6-18

46.76

1.31

76.52

3.51

18-24

48.05

1.39

78.62

3.71

24-30

49.34

1.46

80.73

3.91

30-54

51.48

1.59

84.24

4.26

54-75

54.05

1.75

88.45

4.69

  1. RESULTS AND DISCUSSIONS

    The junction tower is designed as per the codal standards. The percentage changes in sway in different wind load for both versions of codes are tabulated. The percentage change in the increase of quantity of steel according to new version of code and number of failed members are tabulated below.

      1. SWAY

        TABLE NO: 5 SWAY FOR NON-COASTAL ZONE

        LOADS

        SWAY (mm)

        1987

        2015(loads as per 1987)

        2015

        X

        Z

        X

        Z

        X

        Z

        DL+LL

        6.24

        2.05

        6.24

        2.05

        7.85

        1.05

        DL+LL+(WL+X)+WLIP

        40.95

        3.19

        40.33

        3.23

        40.97

        1.61

        DL+LL+(WL+X)+WLIS

        29.00

        2.95

        42.11

        3.25

        42.66

        1.62

        DL+LL+(WL-X)+WLIP

        22.52

        1.14

        34.50

        0.66

        31.67

        0.29

        DL+LL+(WL-X)+WLIS

        28.54

        0.90

        32.72

        0.68

        29.98

        0.44

        DL+LL+(WL+Z)+WLIP

        2.67

        36.66

        4.21

        45.42

        1.54

        43.92

        DL+LL+(WL+Z)+WLIS

        2.28

        36.90

        2.43

        45.40

        0.15

        43.91

        DL+LL+(WL-Z)+WLIP

        10.34

        41.01

        1.51

        48.97

        1.27

        45.73

        DL+LL+(WL-Z)+WLIS

        4.32

        40.76

        0.27

        48.99

        1.37

        45.74

        DL+(WL+X)+WLIP

        36.96

        3.71

        36.33

        3.75

        36.53

        2.45

        DL+(WL+X)+WLIS

        30.93

        3.47

        38.11

        3.77

        38.22

        2.46

        DL+(WL-X)+WLIP

        26.51

        1.66

        38.49

        1.18

        36.11

        1.22

        DL+(WL-X)+WLIS

        32.53

        1.42

        36.71

        1.20

        34.42

        1.23

        DL+(WL+Z)+WLIP

        4.31

        36.14

        8.20

        44.90

        5.98

        43.08

        DL+(WL+Z)+WLIS

        1.72

        36.38

        6.42

        44.88

        4.29

        43.07

        DL+(WL-Z)+WLIP

        6.35

        41.53

        5.50

        49.48

        4.76

        46.57

        DL+(WL-Z)+WLIS

        0.32

        41.28

        3.73

        49.51

        3.07

        46.58

        0.9DL+(WL+X)+WLIP

        36.65

        3.46

        36.03

        3.50

        36.16

        2.26

        0.9DL+(WL+X)+WLIS

        30.63

        3.22

        37.81

        3.52

        37.84

        2.27

        0.9DL+(WL-X)+WLIP

        26.82

        1.41

        38.79

        0.93

        36.48

        1.03

        0.9DL+(WL-X)+WLIS

        32.84

        1.17

        37.01

        0.95

        34.79

        1.04

        0.9DL+(WL+Z)+WLIP

        4.00

        36.39

        8.50

        45.16

        6.36

        43.27

        0.9DL+(WL+Z)+WLIS

        2.02

        36.64

        6.73

        45.13

        4.67

        43.26

        0.9DL+(WL-Z)+WLIP

        6.04

        41.27

        5.81

        49.23

        5.13

        46.38

        0.9DL+(WL-Z)+WLIS

        0.02

        41.03

        4.03

        49.26

        3.44

        46.39

        K3= 1

        PZ according to IS-875(PART 3) 1987

        The design wind pressure at any height above mean ground level shall be obtained by the following relationship between wind pressure and wind velocity:

        PZ = 0.6 ×VZ2

        Where

        PZ = design wind pressure in N/ms at height z, and VZ = design wind velocity in m/s at height

        TABLE NO:3 PZ and VZ values for IS-875(1987)

        Height (m)

        Non coastal zone

        Coastal zone

        vz(m/s)

        Pz(kN/m2)

        vz(m/s)

        Pz(kN/m2)

        0-6

        34.30

        0.71

        73.71

        1.70

        6-18

        35.68

        0.76

        76.518

        1.86

        18-24

        36.73

        0.81

        78.62

        1.96

        24-30

        37.77

        0.86

        80.73

        2.07

        30-54

        39.50

        0.94

        84.24

        2.27

        54-75

        41.58

        1.04

        88.45

        2.52

        TABLE NO: 6 SWAY FOR COASTAL ZONE

          1. QUANTITY OF STEEL

            TABLE NO: 8 PERCENT INCREASE IN QUANTITY

            zones

            QUANTITY(KN)

            % INCREASE

            OLD

            NEW

            Non-coastal

            5037

            5150

            2.2

            Costal

            5919

            7874

            24.8

            LOADS

            SWAY (mm)

            1987

            2015(loads as per 1987)

            2015

            X

            Z

            X

            Z

            X

            Z

            DL+LL

            2.77

            2.03

            2.77

            2.03

            4.34

            4.54

            DL+LL+(WL+X)+WLIP

            58.42

            2.57

            95.35

            2.91

            57.27

            5.04

            DL+LL+(WL+X)+WLIS

            53.56

            2.47

            90.50

            2.81

            55.19

            4.97

            DL+LL+(WL-X)+WLIP

            45.27

            1.73

            79.30

            2.17

            43.48

            4.28

            DL+LL+(WL-X)+WLIS

            50.13

            1.58

            84.16

            1.85

            45.56

            4.21

            DL+LL+(WL+Z)+WLIP

            2.63

            59.54

            6.86

            98.32

            0.94

            50.77

            DL+LL+(WL+Z)+WLIS

            7.10

            59.64

            11.72

            98.42

            1.73

            50.83

            DL+LL+(WL-Z)+WLIP

            3.39

            63.57

            6.51

            102.29

            0.78

            59.81

            DL+LL+(WL-Z)+WLIS

            6.23

            63.46

            11.36

            102.18

            1.31

            59.75

            DL+(WL+X)+WLIP

            56.17

            3.02

            93.10

            3.36

            55.20

            4.02

            DL+(WL+X)+WLIS

            51.31

            2.92

            88.24

            3.26

            53.11

            3.96

            DL+(WL-X)+WLIP

            47.53

            2.14

            81.55

            1.86

            45.56

            3.26

            DL+(WL-X)+WLIS

            52.39

            2.03

            86.41

            1.76

            47.64

            3.20

            DL+(WL+Z)+WLIP

            4.50

            59.08

            9.12

            97.86

            1.72

            51.79

            DL+(WL+Z)+WLIS

            9.35

            59.19

            13.97

            97.97

            3.80

            51.85

            DL+(WL-Z)+WLIP

            3.62

            64.02

            8.76

            102.74

            1.30

            58.80

            DL+(WL-Z)+WLIS

            8.48

            63.92

            13.62

            102.64

            3.38

            58.73

            0.9DL+(WL+X)+WLIP

            56.08

            2.82

            93.01

            3.16

            54.98

            3.71

            0.9DL+(WL+X)+WLIS

            51.22

            2.72

            88.16

            3.06

            52.89

            3.65

            0.9DL+(WL-X)+WLIP

            47.61

            1.93

            81.64

            1.66

            45.78

            2.95

            0.9DL+(WL-X)+WLIS

            52.47

            1.83

            86.50

            1.55

            47.86

            2.89

            0.9DL+(WL+Z)+WLIP

            4.58

            59.28

            9.20

            98.07

            1.94

            52.10

            0.9DL+(WL+Z)+WLIS

            9.44

            59.39

            14.06

            98.17

            4.02

            52.16

            0.9DL+(WL-Z)+WLIP

            3.71

            63.82

            8.85

            102.54

            1.52

            58.49

            0.9DL+(WL-Z)+WLIS

            8.57

            63.72

            13.70

            102.44

            3.60

            58.43

  2. CONCLUSION

      1. The junction tower for a coal handling system was analyzed and designed according to the IS codes designed.

      2. 3.2% of members for non-coastal zone and 14.5% of members for coastal zone were not satisfying the codal requirement if IS-875(PART 3) 2015.

      3. The maximum horizontal sway in X-direction and Z- direction for IS-875(PART 3) 1987 and 2015 are as follows.

        TABLE NO: 9 MAXIMUM HORIZONTAL SWAY

        zones

        X-direction

        Z-direction

        1987

        2015

        (loads as per 1987)

        2015

        1987

        2015

        (loads as per 1987)

        2015

        Non- coastal

        40.95

        42.11

        42.66

        41.53

        49.51

        46.58

        Costal

        58.42

        95.35

        57.27

        64.02

        102.74

        59.81

          1. PERCENTAGE CHANGE IN FAILED MEMBERS

        Zones

        No of failed members

        % change

        Total

        Passed

        Fail

        Non-coastal

        1813

        1755

        58

        3.2

        Costal

        1813

        1550

        263

        14.5

        TABLE NO: 7 PERCENT CHANGE IN FAILED MEMBERS

      4. The increase in the percentage of quantity of steel for non- coastal zone is 2.2% and coastal zone is 24.8%.

      5. There is considerable change in the increase in quantity of steel only in coastal zone. It is better and efficient if we design according to old version.

REFERENCES

[1] Mohammed Asim Ahmed, effect of wind load on tall buildings in different terrain category,vol.4 june 2015 IJRET.

[2] Prof. Amey Khedikar Along wind load dynamic analysis of buildings with different geometries.2015

[3] IS: 875:1987 (part-1 and part2) Indian Standard Code of practice for design loads, Bureau of Indian Standards, New Delhi .

[4] IS: 875:1987 (part-3 ) Indian Standard Code of practice for design Wind loads, Bureau of Indian Standards, New Delhi.

[5] B. Dean Kumar and B.L.P. Swami, Wind effects on tall building frames-influence of dynamic parameters, Indian Journal of Science and Technology, Vol. 3, No. 5.May 2010, 583-587.

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