Design Code Calculations:

1. Dead Load: Dead load for Main IPB = 130 Kgf/m * 132.38 m = 17,210 Kgf Dead load for Tap off IPB = 75 Kgf/m * 69.543 m = 5,216 Kgf GCB Weight = 6500 Kgf Supporting Structure Weight = 8,793.5 Kgf

Total dead load = 37,720 Kgf

2. Live Load:

Live load for Main IPB = 100 Kgf/m2 * 0.96 m * 103.379 m = 9,925 Kgf Live load for Tap off IPB = 100 Kgf/m2 * 0.67 m * 54.093 m = 3,625 Kgf Total live load = 13,550 Kgf

3. Wind Load: Wind loads according to Bangladesh National Building Code.

Structures less than 10 m above ground are designed for Design wind pressure, qz = CI * Cc * Cz * Vb2 [Ref. 1]

Where,

Basic wind speed, Vb = 210 Kmph or 58.33 m/s [Given]

Importance factor, CI = 1.0 [From table 6.2.9]

Conversion co-efficient, Cc = 4.72E-05

Combined height and exposure co-efficient for exposure-B, height: 10 m, Cz = 1.0 [From Table 6.2.10]

Design wind speed, qz = 1.0 * 4.72E-05 * 1.0 * 2102 = 2.081 KN/m2 or 210 kgf/m2

Wind load along-X direction for Main IPB = Projected area * Design wind pressure

= 35.25 * 0.960 * 210 = 7106.4 Kgf Wind load along-X dir. for Tap off IPB = Projected area * Design wind pressure

= 28.687 * 0.67 * 210 = 4036.26 Kgf Total Wind load along-X direction = 7106.4 + 4036.26 = 11,143 Kgf

Wind load along -Y direction for Main IPB = Projected area * Design wind pressure = 45.9765 * 0.96 * 210

= 9,269 Kgf Wind load along-Y dir. for Tap off IPB = Projected area * Design wind pressure

= 15.911 * 0.67 * 210 = 2,239 Kgf Total Wind load along-Y direction = 9,269 + 2,239 = 11,508 Kgf

4. Seismic Load:

The earthquake force experienced by a structure depends on its own dynamic characteristics in addition to those of the ground motion. Response spectrum method takes into account these characteristics and is recommended for use in case where it is desired to take such effects into account. For design of other structures an equivalent static approach employing use of a seismic coefficient may be adopted. The design seismic forces shall be computed on the basis of importance of the structure and its soil-foundation system.

Seismic loads as Bangladesh National Building Code. The following procedure is considered for calculating seismic load.

Design base shear to be calculated by static force procedure. [Ref. 2]

Vb = Z * I * W/R

Where,

For Seismic Zone: Zone-II, Seismic Zone Co-efficient, Z = 0.15

Importance Factor as per UBC, I = 1.0 [From Table 6.2.23]

Response modification co-efficient, R = 8 for Intermediate moment resisting frame system.

C = 1.25 * (S/T)2/3

Where, S = 1.5 [For S3 from Table 6.2.25]

And T = Ct * (hn)3/4 Where, Ct = 0.073 (for Concrete MRF) and hn=10 m

T = 0.073 * (10)3/4 = 0.411

C = 1.25 * (1.5/0.411) 2/3 = 3.4

Design base shear to be calculated by static force procedure.

Vb = 0.15 * 1.0 * 3.4/8 = 0.064 * W

Seismic dead load,

W = Dead Load + 25% Live load = 37,720 + 0.25 * 13,550 = 41,107.5 Kgf

Vb = 2,631 Kgf

Seismic load along X and Y direction = 2,631 Kgf

Seismic load along Z-direction = 2/3*2631 = 1,754 Kgf

5. Short Circuit Force:

Short circuit force for Main IPB = 40.0765 m * 75 Kgf/m = 3,006 KgfShort circuit force for Tap off IPB = (3.645+19.536) m * 125 Kgf/m = 2,898 Kgf

6. Dynamic Forces during switching:

Dynamic force along X-direction = 5,300 Kgf [4x + 13 kN]Dynamic force along Y-direction = 5,300 Kgf [4x + 13 kN]

Dynamic force along Z-direction = 6,116 Kgf [4x + 15 kN]

EIGEN VALUE ANALYSIS:

Eigen value analysis does not involve the computation of response due to any loading, but yields the natural frequencies (Eigen values) and the corresponding mode shapes (Eigen vectors) of the structure when there is no dissipation of energy due to damping. A structure with a non-zero initial condition (initial displacement or velocity) corresponding to any of the mode shapes will exhibit simple harmonic motion at the corresponding natural frequency. The amplitudes of the free vibrations will depend on the initial conditions, and in the absence of damping, the vibrations will continue with out any decay.

The first step in the determination of structural response for the dynamic forces is to estimate the natural frequencies of the structure. The natural frequencies are solved by the Eigen value analysis as a solution, the following equation.

.. [K] {X} + [M] {X} = 0

Where, K = Global stiffness matrix M = Global mass matrix X = Nodal Displacement ..

X = Nodal acceleration vectors respectively.

This analysis involves undamped free vibrations of a given structure. In the absence of damping and applying loads, the equations of motion reduce to a generalized Eigen value problem, which can be solved by employing the various algorithms available in finite element software.

******************* RESULTS OF E I G E N V A L U E A N A L Y S I S **************

MODE ************* FREQUENCY ********** PERIOD NUMBER (RAD/SEC) (CYCLES/SEC) (SEC) 1 2.069531E+01 3.293760E+00 3.036044E-01 2 3.995018E+01 6.358268E+00 1.572755E-01 3 4.680752E+01 7.449648E+00 1.342345E-01 4 4.779191E+01 7.606319E+00 1.314696E-01 5 4.938052E+01 7.859154E+00 1.272402E-01

*************** SUM OF EFFECTIVE MASSES OF ALL MODES ****************

X-MASS Y-MASS Z-MASS MI-X MI-Y MI-Z

2.206E+00 2.206E+00 2.206E+00 2.0776E+08 6.020E+08 4.670E+08

STATIC ANALYSIS:

Results of static analysis consist of nodal displacements and element stresses. Nodal displacements would show the resultant deformation pattern of the given structure for the loadings considered. Element stresses will have six components as follows:

i) Normal stress component along three axes, x, y and z (σx, σy and σz)ii) Shear stress components Txy, TyZ, Tzx

iii) Principal stresses (σ1, σ2 and σ3)iv) Von-Mises Stresses given by

σvon= {(σ1- σ2) 2 + (σ2- σ3) 2 + (σ3- σ1) 2}/2 [Ref. 7]

In static stress analysis of IPB, following load cases were considered:

Load Combinations:

Load case 1 : Dead load

Load case 2 : Live load

Load case 3 : Wind-X

Load case 4 : Wind-Y

Load case 5 : Short circuit load

Load case 6 : Dynamic loads during switching

Load case 7 : Seismic-X

Load case 8 : Seismic-Y

Load case 9 : Seismic-Z

Load case 10 : LC-1 + LC-2 + LC-3 +LC-4 + LC-5 + LC-6 Load case 11 : LC-1 + LC-2 + LC-5 +LC-6 + LC-7 + LC-8 + LC-9

Out of 11 load cases, we are considering worst combination of LC-10 or LC-11, which includes wind or seismic loads which ever is dominant.