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Sub ect:

Design Basis Report forCivil and Architectural Engineering

Note:

This document presents the Design Basis Report for Civil and Architectural

Engineering for 400 kV Switchyard


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Index

S. No. Description Page Number

1.0 PREFACE.............................................................................................................................. 4

2.0 SITE ASSUMPTIONS FOR CIVIL WORK DESIGN .............................................................. 4

3.0 MATERIAL PROPERTIES.................................................................................................... 5

3.1 STRUCTURAL CONCRETE ...................................................................................................... 5

3.2 FILL CONCRETE ................................................................................................................... 5

3.3 GROUT ............................................................................................................................... 5

3.4 REINFORCING STEEL ........................................................................................................... 5

3.5 UNIT WEIGHTS OF STRUCTURAL MATERIALS ......................................................................... 5

4.0 LOAD DATA.......................................................................................................................... 6

4.1 GANTRY TOWER LOADS ....................................................................................................... 6

4.2 EQUIPMENT LOADS............................................................................................................... 6

4.3 EARTH PRESSURE ................................................................................................................ 6

4.4 HYDROSTATIC PRESSURE ..................................................................................................... 6

5.0 LOADING CONDITIONS AND LOAD COMBINATIONS ....................................................... 6

6.0 STABILITY OF TOWER & EQUIPMENT FOUNDATION....................................................... 7

6.1 SLIDING AND OVERTURNING................................................................................................. 7

7.0 DRAINAGE AND ROAD........................................................................................................ 7

7.1 DRAINAGE............................................................................................................................ 7

7.2 ROADWAYS .......................................................................................................................... 8

8.0 CONCRETE COVER.............................................................................................................. 9

9.0 CODES OF PRACTICE, STANDARDS AND REFERENCES................................................ 9


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1.0 Preface

Design Criteria for Civil and Architectural Engineering represent the principal design regulations

and design procedure to be followed .The General design data, assumptions in the design procedure, guideline, steps and codes whichshall be followed for the design of various foundations are listed and explained. The Foundationshall be designed separately from basic foundation design concept with loads from thesuperstructure, Equipment and all possible combinations as explained in 4.0, 5.0. The design ofthe foundation shall satisfy the provisions of ACI 318.

The design criteria shall be a ready reference and design guide for the Civil and Architecturaldesign.

The design data and Site Assumptions for Civil Work Design which shall be used arelisted in 2.0.

The design data for the Material properties for Civil Work Design required and the values

required for defining the material constants in the analysis and design software are listedin 3.0.

In designing the foundations the Global stability concept shall be checked as explained in6.0. The Foundation shall be designed separately and applied with loads from thesuperstructure, Equipment and all possible combinations as explained in 4.0, 5.0. Thedesign of the foundation shall satisfy the provisions of ACI 318/ASCE 10-97.

The final design output drawings shall be reviewed in light of quality managementprocedures .

All the relevant codes which shall be used in designing various Civil and Architecturalelements are listed in 8.0.

2.0 Site Assumptions for Civil Work Design

Identification of Site Conditions and Site Assumptions for Civil Work Design

Description Design Conditions

1 Site Location Place Elevation 1013 m

2 Temperature Ambient Outdoor Temperature From 10C to 50.0C

Mean Annual Temperature 20.0C

3 Average AnnualRainfall

The design rainfall intensity is 162 mm/hour/10year,

4 Snow Load Not Applicable

6 Wind Load As per Technical Specification


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7 Seismic Conditions Seismic acceleration, 0.1g shall be taken for Gantry & Equipment structure only.

8 Soil Data As per Geotechnical Investigation Report

Table 1: Site Assumptions for Civil Work Design

3.0 Material Properties

3.1 Structural Concrete

The compressive strength will be determined according to ACI 318.

Grade (minimum) 30 N/mm2 or equivalent (for foundations, walls etc.)

(min. compressive cylindrical): fck, after 28 days

All exposed edges shall be chamfered 25 mm UNO

3.2 Fill Concrete

For filling purposes and as lean concrete layer underneath foundations concrete 20 N/mm2

(cylindrical strength) shall be used.

Minimum thickness of the fill concrete shall be 75 mm and shall extend 50 mm all around beyondreinforced concrete outline plan area UNO.

3.3 Grout

Non shrink Grout shall be of min. compressive strength 35 N/mm2 as per approved standard.

3.4 Reinforcing Steel

Reinforcement steel shall be of grade 60 deformed conforming to ASTM A615 with the followingmechanical properties shall be used:

Yield strength fyk = 60ksi (413.7 N/mm2 )

Minimum clear cover for various elements shall be as follows:-

Faces in contact with earth (foundation bottom, side face) : 75 mm

Trench wall/ Manhole wall : 50 mm

Minimum Development length UNO shall be as per ACI 318 but not less than 50d

Minimum Lap length UNO shall be as per ACI 318 but not less than 50d

50% staggering shall be done for lap splices.

3.5 Unit Weights of Structural Materials

Steel 7.85 T/m3 Reinforced Concrete 2.5T/m3

Mortar 2.0 T/m3 Plain Concrete 2.4T/m3


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Further material data will be determined by the Structural Engineer within the structural analysis.

4.0 Load Data

4.1 Gantry Tower Loads

Tower foundation loads for various load combinations shall be provided after its approval.

4.2 Equipment Loads

Equipment foundation loads for various load combinations shall be provided after approval of thesupporting superstructure.

4.3 Earth Pressure

Earth pressure for all underground structures shall be calculated using "coefficient of earth

pressure at rest". Additional uniform surcharge loading of 20 kN / m2 shall also be considered forthe design of all underground structures to account for the possible truck movement and otherloads during construction.

4.4 Hydrostatic pressure

For any underground structures if hydrostatic force is experienced during construction stage,computation shall be based on the buoyant unit weight of the soil plus full hydrostatic pressure.The full upward pressure of water below raft shall be taken over entire area.

5.0 Loading Conditions and Load Combinations

Load Combinations Using Allowable Strength Design are as follows

Basic Load Cases -

SW = Self WeightWLT = Wind load on ColumnWLG = Wind load on Gantry BeamNC = Normal ConditionBWC = Broken Wire ConditionEC = Earthquake conditions

Now following load combinations shall be used for both directions for the analysis -

SW +NC+WLT+WLG

SW+BWC+WLT+WLG

SW+EQ+WLT+WLG


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6.0 Stability of Tower & Equipment Foundation

6.1 Sliding and Overturning

Structures subjected to any load combination shall be designed so that the design satisfies

international standard requirements due to global stability, when necessary. Procedure andsafety factors are listed below:

Load Type 1: Dead Loads and Loads due to Normal Condition

Load Type 2: In addition to loads of type 1, simultaneous but not regularly occurring Broken WireCondition

Load Type 3: In addition to loads of type 1, simultaneous, possibly unforeseen loads like ShortCircuit Load

Safety factors must be at least:

Safety against Load Type

1 2 3

1 Sliding 2.0 1.25 1.25

2 Uplift 2.0 1.25 1.25

3 Overturning 2.0 1.25 1.25

7.0 Drainage and Road

7.1 Drainage

Rainwater drainage system within the switchyard fencing shall be made so as to connect it atoutfall points located outside the switchyard boundary. In drainage system design followingpoints have been considered:

a) The surface of the switchyard shall be sloped to prevent accumulation of water.b) Open surface trapezoidal drains having 500mm bottom width and sides having

slope of 1 horizontal : 2 vertical shall be provided.

c) Longitudinal slope shall not be less than 1 : 1000.

d) Open surface drain shall be constructed with a 100 mm thick plain cementconcrete bed of 1:2:4. Drain surface shall be filled up with coarse filter materialsof suitable size on the PCC bed. The top layer of the surface shall be filled upwith fine grained filter material of 150 mm thickness.

e) RCC pipe drain shall be used on the road crossing.Manholes shall be constructed along the drain route at certain intervals and itshall be connected through 200 mm diameter perforated drainflex pipe.


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f) The maximum velocity for pipe drains and open drains shall be limited to2.4m/sec and 1.8m/sec respectively.

g) For the design of storm water drains following Method shall be adopted:Total discharge coming out from an area is given as CIAQ 10=

Where Q = Peak Flow Rate (m3/sec)

A = area of the collection surface (hectare). C = runoff coefficientI = Maximum intensity of rainfall, in mm/ hr

Runoff coefficient for road and gravel area shall be taken as 0.95 and 0.5respectively.

Using Mannings formula, velocity of flow shall be calculated as

2/13/2*)/1*3968.0( SDnV =

Where,V = flow velocity (m/sec)n = Manning coefficient, dimensionlessD = Diameter of pipe (m)A = cross-sectional area of flow, m2

S = Slope of the energy grade line

7.2 Roadways

Bituminous paved access roads of 5 m and 3 m wide shall be provided inside the fence

perimterfor heavy equipments. Crown slope shall be 2 %. For design of road, wheelload SLW 30 shall be considered. Road shall be designed as per AASHTO Standards forpavment design. All roads within the fence shall be single lane. Adequate turning space forvehicles shall be provided and bend radii shall be set accordingly.


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8.0 Concrete cover

In design of concrete structures following covers have been envisaged:

a) Concrete exposed to earth : 75 mm

b) Concrete exposed to weather : 50 mm, for bar dia 16 to 40 mm

c) Concrete exposed to weather : 40 mm, for bar dia smaller than 16 mm

9.0 Codes of Practice, Standards and References

The design Codes and Standards used here are as follows

ACI 318M 99 : Building Code requirement for Structural Concrete

ASD : Allowable stress design for steel structure

ASCE 10 97 : Design of latticed steel Transmission Structures

AASHTO M145 : For design of Roads

UBC 1997 : Uniform Building Code

IBC 2002 : International Building Code

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