Seismic analysis & design of surface power house, … MOHAN VERMA.…1 shows powerhouse during construction. Unit bay portion (24.5m wide x 111m long) consists of MIV floor at El.853.00

Seismic analysis & design of surface power house,

Rampur H.E. Project (412 MW)

Verma, L.M.

Chief General Manager (Civil Design),SJVN Limited,

Shimla-171006, Himachal Pradesh, India

Abrol, R.K.

Additional General Manager (Civil Design),SJVN Limited,


Chauhan,Manish

Manager (Civil Design),SJVN Limited,


Abstract

Rampur Hydro Electric Project 412MW (RHEP) is a tail race extension of existing Nathpa Jhakri

Hydro Electric Project (NJHEP) and runs in tandem with it. RHEP is located on river Satluj, in district

Kullu & Shimla of Himachal Pradesh, India. RHEP is designed to receive 383.88 cumecs desilted

water from tail race outfall of NJHEP with a gross head of 138.70m. The Powerhouse Complex of

RHEP is surface type, with a size of 158m x 34.5m wide x 48m high including two service bays.

This paper briefly describes loading, method of analysis and design of foundations, retaining walls,

superstructure for Surface Power House building. The analysis is based upon seismic parameters values

approved by National Committee on Seismic Design Parameters (NCSDP). Foundations of

superstructure were modelled using Modulus of Subgrade reaction for the rock beneath and analysed

accordingly. Retaining walls were designed for combination of dynamic increment on earth pressure,

active earth pressures and surcharges above. Column, Beams, Substructure and Powerhouse Steel

roofing system were designed for all load combination including seismic, using STAAD Pro &Ansys

software.The results and references obtained are being used as a reference for optimizing & improving

the engineering design & layout of upcoming Surface Power Houses.

1. Introduction :

The surface Power House of Rampur Hydro Electric Project is located on right bank

of river Satluj at EL 878.00m (Service Bay level) nearVillage Bayal, District Kullu

(Himachal Pradesh). Surface Power house complex (158m x 34.5m wide x 48m high)

consists of Unit bay having 6 units, two Service bays and a Control bay. Unit bay

(111mX24.5m wide) houses six Francis turbines each of 68.67MW capacity. Service

bay 1 is located on western side of unit bay and service bay 2 on eastern side. The

control bay is located on northern side of unit bay and gate shafts are located on

southern side. Two lifts including stair cases have been provided on western and

eastern sides of unit bay. The cross section & plan of Power House (Fig. 1 & 2) shows

the different floor elevations & lines markings such as D, E, A, F, C, G, B, H. Picture

1 shows powerhouse during construction.

Unit bay portion (24.5m wide x 111m long) consists of MIV floor at El.853.00 (MIV

floor) where Main Inlet Valves are installed, one no. for each unit. Turbine floor is at

EL861.45 where related panels (cooling water system etc.) are kept and access to

turbine block is provided. Generator floor is at EL865.45 and it houses generator

related panels like NGT, earthing transformer etc. Machine floor is at EL871m

housing UCB, excitation panels etc. For maintenance and repair of MIVs and

Journal of Engineering Geology Volume XLII, Nos. 1 & 2

A bi-annual Journal of ISEG June-December 2017

52

Runners, openings are kept in turbine, generator and machine floor slabs.Service bay

1 & 2 (27m X 24.5m& 20m X 24.5m respectively)located at El.878m are beused for

erection, installation, maintenance etc. of rotor, stator, MIV, transformer etc.EOT

cranes (2 Nos.) of 150T capacity have been provided at El.890m and runs all along

Service bay 1, unit bays and service bay 2. The unit bays and service bays are covered

by a sloping lattice roof truss system.

EL 865.45

TRENCH

13200

EL. 846.50y

yEL. 846.10

yy

2000

EL.853.5

10000

BACK FILL

C/L

-OF

DR

AF

T

DT GATE HOIST

4875 4875

TRANSFORMER

EL.901.00EL.898.30

MIV

DRAINAGE GALLERY(2000 x 2500)

EL.848.452

y y y y y y y y y

G-L

INE

y

y

y

y

y

GENERATOR

EOT CRANE BEAM(1700X1500)

PANEL/CONTROL ROOM

E.O.T. CRANE(2X150 TONNES)

E-L

INE

A-L

INE

B-L

INE

H-

LIN

E

EL. 852.779

EL. 849.188

POWERHOUSE - TYPICAL CROSS - SECTION

C/L - OF PENSTOCK

EL.858.40

TRT

C/L-OF PENSTOCK

DRAFT TUBE

y

E.O.T. CRANE

CABLE

yy

TRANSFORMER

400052505250

C-L

INE

F-L

INE

D-L

INE

47508250

C/L

-OF

UN

IT

VENTILATION

24500

EL.865.45

11800

y y y y y y y y

THRUST COLLARS

(ALONG C/L OF UNIT)

EL . 878.00

EL.856.20

22000

1250

1000

SWITCHYARD

GAS INSULATED

ROOF TRUSS

DCDV / BATTERY

LINE PROTECTION

BOARD SPACE

MIVPEDESTAL

SPIRAL

CASE

ACCESS

THRUST BLOCK

FRAME FORGIS BUSHING

DT GATE SHAFT

YA

RD

FOR RAIL TRACK

EL . 853.00EL . 851.00

EL . 863.34

BUS DUCT/

GALLERY

EL . 888.00

TR

AN

SF

OR

ME

R

GENERATOR FLOOR

TURBINE FLOOR

EL.861.45

MACHINE FLOOR

EL.871

STATION SERVICE2000

EL.878

EL.883.50

EL.889

EL.867.60

EL.865.19

EL . 878.00

EL.890.00

EL.895.00EL.895

(10 TONNES)

2000

2000

2000

EL.853

MACHINE FLOOREL.871.00

GENERATOR FLOOREL.865.45

TURBINE FLOOREL.861.45

MIV FLOOREL.853.00

TU

BE

GA

TE

ROOM

Figure 2

Figure 1



53

Water enters spiral case at EL858.4m and henceforth to draft tube, through penstocks

embedded in thrust block below control bay raft and main inlet valve.

The powerhouse frame consists of four longitudinal column rows (D, E, A & B lines)

with one transverse column row at beginning and end of frame block. Each frame

block consists of two units. An expansion joint has been provided after every frame

block. D-line columns are 1mX2m from EL865.45m to EL898.3m and 1mX1.1m

above EL898.3m. E-line columns are 1mX1m from EL865.45m to EL889m. A-line

columns are 1mX2m from EL853m to EL890m, 1mX0.9m from EL890m to EL895m

and 1mX0.5m above EL895m. B-line columns are 1mX2.5m from EL853m to

EL878m, 1mX2m from EL878m to EL890m and 1m X 0.9m above EL890m.

2. Geology:

In the investigation stage subsurface exploration of power house area has been done

by drilling 8 nos. holes with depth varying from 30-45m. Exploratory drill holes

established the availability of rock surface at a depth of about 4.50 m along the centre

line of the Powerhouse building. The rock encountered between depths of 4.50m to

28.00m was mainly grey - greenish Phyllite, thinly to moderately foliated and further

between 28 to 45m depth, it was mainly dark phyllite and is thinly to closely foliated.

The rock in general is soft and flaky in nature but at places it is fresh and hard in

nature.

The rock in Power house and TRT area mainly comprises of carbonaceousphyllites

and the rock quality is poor to very poor. The foliation of rock is dipping towards the

pit from river side in southern portion.The details of major joint sets are as follows:

1st set of joints are mainly foliation joints N20ºW; 40º, the whole circle

bearing works out to be 340º; 40º. These joint sets have been named as J1.

2nd set of joints are S10ºW; 55º, the whole circle bearing works out to be

190º; 55º. These joint sets have been named as J2.

3rd set of joints are N75ºW; 60º. The whole circle bearing comes to be 285º;

60º. These joint sets have been named as J3.

Picture 1 Powerhouse during construction stage



54

3. Method of Frame Analysis:

The complete structure has been modelled, including column, beams and trusses to

assess the exact effect during normal and emergency conditions. Bracing for trusses

have also been modelled in the STAAD Pro model. Columns and beams have been

considered as 3-D space frame (modelled using centre lines of structural members and

offsetted where necessary) (See Picture 2). 3 D frame analysis has been carried out

using STAAD Pro Software. The columns have been considered fixed at bottom ends.

The analysis of superstructure when it is fully constructed has been called Finished

Stage analysis (Picture 2).

Moreover an intermediate stage analysis called construction stage analysis (Picture 1)

has been carried out, which represents a stage during construction that lasted for over

a year. During this stage, only A line and B line columns are to be raised so as to

install 150T EOT crane and roof truss, so that EOT crane can help in erection of spiral

case, pit liner, stay rings, lowering of rotor, stator, turbine etc. during the project

construction stage. This stage is common for all units. In this stage B-line columns

have been considered up to EL895m, laterally tied at EL865.45m on d/s side with DT

gate shaft. A-line columns have been considered up to EL895m with D & E line

columns up to EL878m along with floor slabs of EL871m & EL878m on control bay

side. However floors in unit bay portion have not been considered.In all the analyses

the structure has been considered to behave independently from the barrel and

generator foundation i.e. no load transference from the superstructure to barrel and

generator foundation has been considered. Analysis of barrel & generator foundation

was done separately using Ansys software. Load from unit bay floors (live and dead)

have been distributed directly to corresponding beams.

The seismic analysis has been done as per IS 1893 (Part 1): 2002. Response spectrum

method of analysis has been used for analysis. Base shear due to response spectrum

method was compared with static method, and whenever response spectrum base

shear was lesser all response quantities were scaled up appropriately. Spectra for

response spectrum analysis was taken as per site specific seismic parameters studies

carried out for RHEP by IIT Roorkee. STAAD Pro software has been used for seismic

as well as non-seismicanalysis.The member forces have been taken from the STAAD

Pro analysis. Based on the end forces, the critical cases for structural design have been

selected for design.



55

Picture 2 3D STAADPro Model (Finished Stage)

4. Design Loads:

The following loads have been considered in Frame analysis:

4.1 Dead Loads:

Self-weight of columns, beams and roof truss has been calculated through STAAD

Pro Software (Self weight command). Dead load of floor slab of 300mm thickness

(including 50mm floor finish)has been applied through STAAD Pro software as

uniformly distributed area load.Dead load of 300mm thick RCC wallshas been

transferred as uniformly distributed load on corresponding beams at actual beam c/l

eccentricity. Dead load of roof sheeting has been considered as 0.125kN/m2 and has

been applied as uniformly distributed load on roof purlins.Same load as that of roof

sheeting has been considered for false ceiling at bottom bracing level of trusses and

applied as uniformly distributed load on bottom bracing.

4.2 Live load:

Live loads have been taken as per IS 4247 Part-1.

Floor at EL 889m (GIS floor)= 20kN/m2

Floor at EL 883.5m(Battery Room & Office area) = 10kN/m2

Floor at EL 878m(Control Room area)=10kN/m2

Floor at EL 871m(Machine floor)= 10 kN/m2

Floor at EL 865.45m(Generator Floor)= 10 kN/m2

Floor at EL 861.45m(Turbine Floor)= 15 kN/m2

False ceiling level = 0.375 kN/m2 (erection and maintenance).

Roof (Inaccessible) = 0.75kN/m2

Live load on floor slabs has been applied through STAAD Pro software as uniformly

distributed area load.

4.3 Wire Stringing Load:

A triple conductor wire with stringing tensile load of 9Tonnes at EL900.5m along D

line columns/beams has been considered at specified locations. Also shield wire

stringing load of 0.8Tonnes has been considered at EL908.5m along D line columns.



56

4.4 Seismic loads:

Project is located in the seismic zone 4 as per seismic map of India. Site specific

studies for determining seismic parameters had been carried out for RHEPby

Earthquake Engineering Department of IIT Roorkee.

The studies recommends following design earthquake parameters for the Power

House, which havebeenapproved by National Committee for Seismic Design

Parameters (NCSDP):

αh=0.14 g andαv=3

2αh=0.09g

Full seismic load in one horizontal direction only (longitudinal or transverse) has been

considered to be acting along with the full vertical seismic load simultaneously. The

response due to combined effect of the above two seismic components (vertical and

horizontal) has been evaluated.

In earthquake analysis, weight of panel walls, floor slabs and roof sheeting has been

considered as a lumped mass, distributed equally at joints. Earthquake effect on self

weight has been considered by software itself. During earthquake, only 50% live load

has been considered on floor slabs. However no live load has been considered on roof

during earthquake.

4.5 Crane loads:

Crane load corresponding to 2 Nos. 150T crane on erection bay area at EL 890m and

1 No. 10T EOT crane at EL 898.3m in control bay area has been taken both for

normal condition (fully loaded moving crane with surges) and emergency condition

(seismic condition unloaded stationary crane). Longitudinal surge has been taken as

5% of static wheel load and transverse surge has been taken as 10% of weight of

trolley and load lifted. Crane loads have been applied as concentrated loads on crane

beams in STAAD Pro-3D analysis for various load locations.

4.6 Wind loads:

The wind load has been worked out below in accordance of IS: 875 (Part III).

The reference of clauses, figures and tables given below are from IS: 875 Part III

(1987)

Design wind pressure Pz (Cl 5.4) = 0.6 x Vz2 = 1.22 kN/m2

Wind loads in horizontal directions have been applied directly on structure by

STAAD Pro commands and as uniformly distributed load vertically upwards on

purlins of trusses.

4.7 Temperature Loads:

The roof trusses have been designed for ± 280C temperature variation, which is

approximately 2/3rd of the max/min temperature difference. Temperature load has

been applied on trusses for both contraction and expansion conditions.

4.8 Snow Loads:

Snow load corresponding to a feet of snow has been considered i.e. 2.7kN/m2



57

4.9 Earth Pressure Loads:

On southern side of unit bays are the gate shaft and collection gallery. This portion

has been backfilled to EL874m after construction. Hence earth pressure on d/s side

i.e. on B line side has been considered along with water pressure corresponding to

high flood level. This pressure has been applied as uniformly distributed load (varying

trapezoidally) on B-line columns.

5. Load Combinationsfor Frame analysis:

Different load combinations have been taken as per IS 4247 Part-II:

Normal load case with fully loaded moving cranes at different locations.

Emergency load case 1 with fully loaded moving cranes at different locations

and temperature loads (contraction and expansion due to temperature load).

Emergency load case 2 with fully loaded moving cranes at different locations,

full dead loads and live loads, temperature loads (contraction and expansion

due to temperature load) and full wind load. This combination has not been

considered in construction stage analysis.

Emergency load case 3 with full earthquake forces along with unloaded

stationary cranes at different locations, full dead loads, appropriate percentage

of live loads and temperature loads (contraction and expansion due to

temperature load).

6. MaterialSpecifications

The following material properties have been adopted in design:

a) Structural Concrete

Grade M25A20, Characteristic Strength 25 N/mm2,

Modulus of Elasticity 25000 N/mm2 (MPa), Unit Weight 24.5 kN/m

3

b). Structural reinforcement

Grade Fe 415 grade, Characteristic Strength of Steel 415 N/mm2 (MPa),

Modulus of Elasticity 200,000 N/mm2 (MPa), Unit Weight 78.5 kN/m

3

c). Structural Steel

Grade Fe 250 grade, Characteristic Strength of Steel 250 N/mm2 (MPa),

Modulus of Elasticity 200,000 N/mm2 (MPa), Unit Weight 78.5 kN/m

3

7. Methodof Design:

7.1 Raft:

MIV Raft at EL853m and Control Bay Raft at EL862m have been modelled as elastic

foundation using plate elements in STAAD Pro software, using appropriate modulus

of sub grade reaction. Maximum axial loads and maximum moments from

superstructure frame(corresponding values), raft dead load,appropriate live load, MIV

pedestal loads and MIV servomotor loads have been applied on the raft model. All

conditions have been considered in evaluating critical loads to be applied on raft

model i.e. construction stage and finished stages. From output of raft model critical

bending momentsand shear forces have been obtained and design has been done

manually as per Limit state design method.



58

Picture 3 Critical Moment Contour

Picture 4 Critical Stress Contour

Modulus of subgrade reaction value has been taken as 10000T/cum (references taken

from National Building Code and “Foundation Analysis & Design” by Bowles). Main

reinforcement in each direction and shear reinforcement has been calculated. Check

for foundation punching shear and bearing pressure check has also been carried out. A

reinforcement of 32mm diameter Fe415 bars @ 150mm c/c along both directions

along with 12mm diameter stirrups @ 300mm c/c along A & B-lines and 150 c/c in

transverse direction has been proposed for MIV Raft.A reinforcement of 32mm

diameter Fe415 bars @ 200mm c/c along both directions along with 16mm diameter

stirrups @ 200mm c/c both ways has been proposed for Control Bay Raft.A safe

bearing capacity of 52T/Sqm was considered, with an increase of 50% in seismic load

conditions as per IS codes. Design was also checked manually considering imposed

loads from superstructure columns, MIV, Live Loads, Self-weight etc. and

eccentricities in either directions.

7.2 Columns:



59

For column design maximum moments in Y and Z directions, maximum shears in Y

and Z directions, maximum and minimum axial forces have been considered and the

design has been performed using STAAD Pro software. Forces have been considered

at one end at a time and for one maximum value, other corresponding values have

been considered in design. Additional moment due to slenderness of columns has also

been considered in design. Design has also been checked manually.

7.3 Beams:

For beam design maximum hogging and sagging moments, maximum shears and

maximum torsion have been considered and the design has been performed using

STAAD Pro software. Forces have been considered at one end at a time and for one

maximum value, other corresponding values have been considered in design. Design

has also been checked manually.

7.4 Steel Trusses (For Machine Hall and GIS Floor):

The member forces have been taken from the STAAD Pro analysis.Based on the

member forces, the critical cases for structural design have been selected and the truss

members are designed for the same. For emergency conditions with wind and

earthquake loads, a increase of 33.33% has been considered in permissible stresses

whereas for temperature loads this increase is considered as 25%. This allowable

increase in permissible stresses for wind, temperature and earthquake loads has been

incorporated in corresponding load combinations.Overall increase of 25% has been

considered in permissible stresses in welds for design of welded connections, for all

emergency cases.

The pinned connection with RCC frame has been achieved by erecting a rocker

bearing at site, which has been designed accordingly.The bearing consists of a top

saddle arrangement and bottom saddle arrangement connected by a rocker pin on

which rotation takes place.Saddle, bearing plates, pin have been designed for bearing,

shear and bending stresses.Connection of rocker bearing to foundation plate has been

designed for shear and bending stresses.The foundation plate has been checked to

pass above load safely to concrete beneath without exceeding concrete bearing

stresses. Foundation plate has been anchored to concrete beneath by 6 nos. M33

bolts,ensuring maximum load carrying capacity of bolt is not exceeded.

Design has been done as per IS 800 using STAAD Pro software, and has also been

checked manually. Each member has been designed for axial forces, moment in either

axes or shear forces.It has been ensured that a combined ratio of axial and bending

stresses to permissible stresses is less than unity.Truss joints have been designed for

combined stresses including axial forces and bending moments, since the joints are

welded & will offer resistance to moments.

7.5 Retaining Wall:

In order to protect the power house complex from floods during high flow season,

flood protection wall has been provided towards river side with its base at El. 867.50

and top at El.880. This wall was constructed before under taking excavation of power

house pit as per opinion of experts.



60

The retaining wall has been designed for a normal load condition comprising of self-

loads and earth fill loads. The wall has also been checked for earthquake load

combination comprising self-loads, earth fill loads and horizontal & vertical

earthquake loads on gravity loads& earth fill loads (dynamic increment). A high flood

condition has also been considered which considers self-loads, earth fill loads,

horizontal water pressures and uplift water pressure.

8. Permissible Deflections:

For Construction stage analysis the maximum horizontal displacement due to

earthquake forces shall not exceed 0.4% of the storey height H (H = EL895 -

EL853m). Maximum horizontal displacement is 103.91mm corresponding to

permissible limit of 168mm. (Safe)

For Finished Stage analysis the maximum horizontal displacement due to earthquake

forces shall not exceed 0.4% of the storey height H (H = EL901 - EL877.95m).

Maximum horizontal displacement is 90.3mm corresponding to permissible limit of

92.2mm. (Safe)

9. Challenges Faced:

9.1 Southern Slope Stability:

For southern slope stability, wedge analysis was carried out using Unwedge

software.Joint sets as described under para 2 “Geology”, cohesion value of 6.03KPa,

friction angle equal to 27.580 and unit weight of 2.47gm/cc was considered for wedge

/planar analysis.Since the foliation of rock is dipping towards the pit from river side in

southern portion, an unstable wedge formation was observed on southern slope.

Accordingly support consisting of 25mm dia rock bolts having alternate lengths of 7m

& 6m at spacing 1.5mx1.5m along with 100mm thick Shotcrete was proposed to

stabilize the wedge.Drainage holes of 76mm dia and 4m length have also been

proposed at a spacing of 3mx3m on southern slope.Further, for foliation angle, planer

failure analysis was done.As per provided support, anchorage force was greater than

required.

During excavation of Power House pit, rock fall was observed on southern slope.

After due discussions held between designdepartment,site, geology department. &

GSI geologist, it was proposed to increase the length of rock bolts to 9m & 7m. It was

also decided to cut the slopes, in the non-draft tube portions, at angle of about 71.5°

with respect to horizontal.Due to very poor geological conditions encountered at site

and detachment of Rock ledge in the corner portion between unit No. 2 &3, it was

decided to enhance the existing support system by providing additional beams and

columns (about 1.6m wide) in the south wall of pit. In this arrangement, beams at

three levels i.e. about EL. 868, EL. 863 & EL 858 were proposed. This arrangement

made the grid in the form of concrete beam in horizontal direction and along cut

profile in the south wall of pit. Two rows of staggered rock bolts having dia as 32mm

and about 8-9m long were to be provided through each beam.

Adequate instruments (MPBX & prism targets) were installed on southern slope. The

movements and cracks on southern slope, based on instrument data, were reported by



61

Site Engineers. Thus in consultation with site, it was decided to provide a 1m thick

slab/raft at EL 872.7m +/- along with 32 dia grouted anchor bars. 32 dia grouted

anchor bars 9m deep, 1.5m centre to centre, both ways were also proposed. The

inclination of anchor bars proposed to be about 20° with vertical, dipping towards

river side to stitch maximum foliations. The aim was to water tight and avoid the

chimney formation in the TRT area. Also further movement of cracks was expected to

be arrested.

Still due to ongoing construction work of d/s side and ingress of water from river side,

partial detachment of rock on southern slope occurred. The recommendations of

various experts viz.GSI, CWC, Advisory Board Members, World Bank etc. were

considered. Overburden was removed upto El.868m and southern slope to be

stabilized by 36 dia grouted anchor bars, 7500mm long @ spacing of 1.5m c/c.

Shotcrete of 150mm thick with wire mesh was provided (Fig. 3).

Figure 3 Southern Slope stability

9.2 Control of Differential sway & Total Sway:

During preliminary analysis it was found out that due to unsymmetrical frames(on u/s

side frame consisted of D line, E line & A line columns whereas on d/s side just B

line cantilever frame) supporting either truss ends, differential sway at EOT crane

level or total sway at top was exceeding permissible limits. In case of differential

sway it meant that there were chances that load might be transferred to the EOT crane.

Thus it was decided to tie column tops by roof trusses so as to limit differential sway

at EOT crane level and total sway at column tops. In order to keep trusses light weight

and also effective in holding together RCC frames, a rocker bearing was proposed at

column/beam & truss junction, which would eliminate moment and transfer only



62

lateral force. This rocker bearing was designed accordingly as designed in section

“Method of Analysis”. Thus truss connections to superstructure (columns or beams)

have been considered as pinned. This has been achieved in STAAD Pro model by

releasing moment in plane of truss by STAAD Pro release command, thus ensuring

that the joint only transfers thrusts and the moment is not transferred at these joints.

9.3 Structural Analysis of Different Construction Stages:

During the project construction stages various analyses were carried out to finalize an

optimised structure which would be economical, safe for all loads as described earlier

and to cater Electro Mechanical requirements. Before project construction,

commencement of preliminary analysis was carried out, which helped in knowing the

general behaviour of the structure and helped in optimizing the sizes of columns and

beams. Theses analyses also brought to light the challenge to control sway (total &

differential).Afterwards the construction stage analysis was carried out, which has

been described earlier. This would be the stage during construction when only

cantilever frames would be erected so that EOT cranes could become operational and

assist in barrel erection, spiral case erection, rotor & stator lowering etc. Analysis was

also done to realise the requirement of roof trusses during construction stage. Since

erection of rotor, stator, spiral case lining, runner etc was going on in parallel with

civil structure erection, there was also need to check the safety of structure during

operation of EOT cranes for transportation of Electro – Mechanical equipments

through superstructure frames. Analyses were done for same and structure safety

ensured by setting up safety guidelines for crane operation. Analyses were also done

for erection of steel trusses using Derek structure, when approach of tower crane was

found to be limited due to construction activities. When the issue of change in layout

of control room was encountered, a complete separate analysis was carried out to

ensure safety of revised structure. Analyses were also done to check effect of

conductor stringing loads on superstructure at different elevations, so as to finalize

final conductor load location and strengthening required on that account. There were

other analyses that were carried out simultaneously which are not too significant as

far as the scope of this paper is concerned.

10. Conclusion:

This paper brings forth the methodology of seismic as well as non seismic analysis &

design, various loads considered and load combinations considered in analysis and

design of surface powerhouses. Analyses of different construction stages, based on

erection sequence of frames and loads coming over structure, have been carried to

take advantage of EOT crane for installation of heavy equipment & to facilitate the

construction process.Emphasis has been laid on foundation design based on Modulus

of Subgrade reaction, southern slope stabilization and design of retaining walls.

Overall it has been emphasized that the structural engineer has to work continuously

and has to be always ready to mould his design for changes/modifications during

construction or due to geological surprises, in a manner that the structure conforms to

Electro-Mechanical & construction requirements, is best possibly optimised and is

safe for all the loads it will be subjected to during its life time.

11. References:



63

In general, relevant Indian Standards (IS) have been used in the design:-

IS 456-2000 Code of Practice for Plain and Reinforced Concrete, Fourth

Revision

IS 1786-1985 Specification for High Strength Deformed Steel Bars and Wires

for Concrete Reinforcement”, Third Revision

IS 1893 (Pt-1)-2002 Criteria for Earthquake Resistant Design of Structures, Part 1 -

General Provisions and Buildings, Fifth Revision

IS 1893-1984 Criteria for Earthquake Resistant Design of Structures (Fourth

Revision)

SP 16-1978 BIS Handbook: Design Aids to IS: 456

SP 34-1987 BIS Handbook on Concrete Reinforcement and Detailing

IS 4247(Pt-1)-1993 Structural design of surface hydroelectric power

Stations, (Part-1) Data for design – Code of practice (3rd

revision)

IS 4247(Pt-2)-1992 Code of practice for Structural design of surface hydroelectric

power Stations, (Part-2) Superstructure (2nd revision)

IS 4247(Pt-3)-1998 Code of practice for Structural design of surface hydel power

Stations, (Part-3) Substructure (2nd revision)

IS 800-1984 Code of practice for general construction in steel

IS 808-1989 Dimensions for hot rolled steel beam, column, channel and

angle Sections

IS 1367(Pt-3):2002 Technical supply conditions for threaded fasteners

SP:6 (1) – 1964 ISI handbook for structural engineers (Structural Steel

Sections)

IS 816 Code of practice for use of metal arc welding for general

construction in mild steel

Report No.

EQD-3018-EQ: 2009-26 Site Specific Design Earthquake Parameters for Rampur H.E.

Project, Himachal Pradesh

Documents

Seismic analysis & design of surface power house, … MOHAN VERMA.…1 shows powerhouse during construction. Unit bay portion (24.5m wide x 111m long) consists of MIV floor at El.853.00