STRUCTURAL

DESIGN BASIS REPORT

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1. INTRODUCTION

The purpose of this document is to describe the structural system, analysis

and design criteria for the proposed new building for Woodlands Hospital at
Kolkata.

2. SCOPE OF WORKS

The scope of the work includes the following:

 Proposed new hospital building
 External works

3. DESIGN PHILOSOPY

3.1 PROPOSED NEW HOSPITAL BUILDING

The proposed building consists of 1 Basement + Ground floor + 10 floors. The

proposed structural system comprises of composite steel column with Deck
slab and structural steel beams. Columns are spaced at approximately 7.75 X
6.968m center to center. Lateral Stability is mainly provided by reinforced
concrete wall, which is located in lifts, stair wells and edges based on
design requirement. These walls are generally designed for resisting lateral
loads that induced from wind or earthquake other than gravity loads. Linac
room is considered with RC wall at basement floor level.

Floor to floor heights:

 Basement floor : 6.00 m

 Ground floor : 3.90 m
 First to third floor : 3.45 m
 Fourth floor : 3.75 m
 Fifth to tenth floor : 3.60 m

Overhead tank is considered above staircase head room slab. Supporting system
for Solar panel is considered above terrace slab.

The foundation system shall be designed in accordance with the site-specific

soil investigation report and the type of foundation has been decided as
Pile foundation. The RCC Retaining wall for basement is designed for gravity
loads, soil pressure, water and surcharge load.

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Water proofing is considered for raft, pile cap, terrace, toilets & wet
areas, AHU rooms, water tank and basement of Retaining wall. Fire tender
load is considered wherever fire tender access there.

4.0 DESIGN LOADS

4.1 DEAD LOADS

The super imposed dead loads that are envisaged to act permanently (wherever
applicable) are as following:

Items Intensity in kN/m2 of plan area

Depends on the thickness, slope and

Weatherproof course* kind of material to be used for
weatherproofing.

Partitions** Actual

Floor finish 1.2

False ceiling + M&E Services

0.5
(including supporting system)

*The loading due to weatherproof course consists of the following

a. 100mm avg. thick Brick Bat Coba laid to the required slope
b. 20mm thick Bedding mortar
c. Weight of pressed clay tiles
**In toilet area the actual partition loads shall be calculated and
considered wherever it is applicable.

4.2 SUPER IMPOSED LAODS:

The superimposed load or otherwise live load assessed based on the occupancy
classifications as per IS: 875 (Part 2) – 1987 is listed as follows: -

UDL Conc. #
Occupancy classification
KN/m2 Load KN

Laboratories Actual Actual

X-ray rooms, Operating Rooms,

4.5 4.5
general Storage area, ICU

Office rooms and OPD rooms 4.5 2.7

Wards, Dressing rooms and lounges 4.5 1.8

Records/files store rooms and

5.0 4.5
storage space

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 Medical Equipment Actual Actual

Dormitory 4.5 1.8

Dining rooms and cafeterias 4.5 2.7

Kitchen 4.5 4.5

Corridors, passages and

4.5 4.5
staircases including fire escapes

Assembly areas with fixed seat 4.5 -

Assembly areas without fixed

5.5 3.6
seats Most of the areas of Terrace is covered
with steel roof, so loading is as per the
Baths and toilets 4.5 -
uses of that area. Only remaining areas
Terrace 10.0 - (Open to sky ) this load will be assigned.

As per vendor
Lift machine room
requirement
# The concentrated loads are considered to be applied in positions, which
produce maximum stresses and where deflection is the main criteria, in the
positions, which produce the maximum deflections.

• Chillers, cooling tower and Equipment loads shall be considered in the

design as per vendor detail.

• Other live loads to be considered are as follows:

• Route for taking in equipment to be strengthened – MRI, CT, PET

CT, Linac etc.

• Filling load in kitchen and sunken areas.

Wind code revised in the year 2015. We

4.3 WIND LOAD: are following IS 875 part 3 - 2015 with
latest ammendment
The wind pressure shall be calculated based on the data furnished below and
other provisions laid in IS: 875 (Part 3) – 1987.

Basic wind speed = 50 m/sec

Risk coefficient = 1.08 (Mean Probable Design Life of
All Structure 50toyears)
parameter need revise
Design wind speed at any height Vz=
Terrain category = 2 K1K2K3K4Vb
Structure class = Class C Structures K1 = Risk Coefficient = 1.08
K2 = Terrain roughness and height factor
Topography factor = 1.0 K3 = Topography factor = 1
K4 = Importance factor = 1
Design wind Pressure = 0.6 Vz2
4.4 EARTHQUAKE LOAD:

The loading due to earthquake is assessed based on the provisions of IS:

1893-2002. Seismic zone – III is considered as per codal provisions and
Latest Seismic Code is 1893-2016 with
latest ammandements

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Importance factor of 1.5 for hospital building is considered. R value is
considered as 4 for Composite building with RCC Structural walls.

4.5 TEMPARATURE LOAD:

The effects of thermal actions on the structures due to climatic for the
structure shall be considered by applying temperature loads. Since building
is covered with façade/ Blockwork on the external sides and no appreciable

temperature on the internal floors during the service life of the building.
Therefore, all the floors are not designed for any temperature loads.

As terrace slab is exposed to outside, there shall be considerable

temperature variation through terrace slab. Therefore, terrace shall be

LOAD Limit state of Collapse Limit state of Serviceability

COMBINATION
DL LL WL/EL TL DL LL WL/EL TL

DL + LL 1.5 1.5 -- -- 1.0 1.0 -- --

1.5 or
DL +/- WL -- 1.5 -- 1.0 -- 1.0 --
0.9$

DL + LL +/- WL 1.2 1.2 1.2 -- 1.0 0.8 0.8 --

1.5 or
DL +/- EL -- 1.5 -- 1.0 -- 1.0 --
0.9$

DL + LL +/- EL 1.2 1.2 1.2 -- 1.0 0.8 0.8 --

DL + LL + TL 1.5 1.5 -- 1.5 1.0 1.0 -- 1.0

designed for temperature loads.

As per IS:875 (Part 5) - 1987, the maximum temperature for Kolkata is 42.5°
C and the minimum temperature is 7° C. Considering a mean average concrete
temperature of 27° C, the total mean temperature variation of 15.5° C raise
& 20° C fall is considered. The effect of this temperature variation is
considered on exposed area in the analysis.

4.6 LOAD COMBINATIONS

The various loads shall be combined in accordance with the stipulations in

IS 456:2000. Whichever combination produces the most unfavorable effect in
the building, foundation or structural member concerned shall be adopted.

$ This value is to be considered when stability against overturning or stress

reversal is critical

DL - Dead load

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 LL - Live load
WL - Wind load
EL - Earthquake load
TL - Temperature load
Wind load and earthquake load shall be considered for both x & y directions.
The above load combinations will be considered and effect of worst
combinations will be taken for design of various building elements.

Whenever imposed load is combined with earthquake load the appropriate part
of imposed load as specified in IS: 1893 – 2002 will be used both for
evaluating earthquake effect and for combined load effects used in such
combination.

Safe Bearing Capacity will be suitably increased as per IS 1904-1986 for

combination with WL and as per IS 1893 (Part 1)-2002 for combination with
EL.
IS 1893 part 1 - 2016
IS 875 part 3 - 2015 with with latest ammendment
5.0 DESIGN LIFE
latest ammendment
The design life of the structure is taken as 50 years as per IS 875 (Part
3)-1987 based on return period. This requirement is not applicable to
replaceable materials. ETABS/SAFE/STAAD/
Any internationally
6.0 ANALYSIS & DESIGN METHODOLOGY accepted software
packages
The analysis of the structural steel Composite structures is carried out
using the ETABS/SAFE software package. Beams and columns are modeled as frame
elements while RC walls are modeled as shell element and conventional deck
slab is considered as membrane element. The slab has been considered as a
diaphragm at the respective floor levels to resist the lateral forces.
Appropriate loads and its combinations, as per relevant clauses in IS codes,
for most unfavorable effects are chosen for design.

SERVICEABILITY LIMITATIONS

Steel Elements

 Floors and Roofs Beam Elements Span/250

 Cantilever Beam Span/150
Lateral Sway

 The lateral sway at the top of building due to Wind loads shall not
exceed H/500,
Lateral Drift

 Allowable drift at any storey < h/250 where h = storey height due
to Seismic.

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7.0 MATERIALS

The self-weight of the various elements are computed based on the unit weight
of materials as given below:

Materials Unit weight kN/m3

Reinforced Cement Concrete 25.00

Plain Cement Concrete 24.00

Cement Concrete Solid Block work 20.00

Steel 78.50

Dry Soil 18.00

Wet Soil 20.00

Water 9.81

Aluminum 27.00

Glass 26.00

AAC Block work 7.00

Reinforced Cement Concrete

The Grades of concrete to be used in the construction of the works shall be

as follows, in accordance with IS 456: 2000:

Grade of Max. Size of

Concrete item Type of cement
Concrete Aggregate (mm)

Pile cap M40 20 OPC

Raft M40 20 OPC

Retaining wall M30 20 OPC

Columns M40 20 OPC

Rc walls M40 20 OPC

Slab & beams M30 20 OPC

Sump/STP walls M30 20 OPC

Staircase M30 20 OPC

Reinforcement

Steel reinforcement shall be of Grade Fe 500 D / Fe 415 conforming to IS:

1786-2008.

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Structural Steel

 Steel plates, Hot rolled medium & high tensile structural steel of
grade E350 BR conforming to IS: 2062:2011.
 Steel Hollow section & Tubes YST 310 shall conform to IS 4923 & IS1161.
 Bolts, Nuts & Washers conforming IS 1363 -2002, IS1364-2004 & IS6623-
2004.

Structural steel painting

 The structural steel surface preparation for beams & columns shall be
with abrasive blasting of SA2.5.
 All exposed surface of the steel shall be painted with base coat of
Zinc rich epoxy primer (80 micron).
 All encased steel columns shall not be painted.
 The Floor & Roof beams are protected with Vermiculate for 3 Hour Fire
rating.
 All columns to be of rolled sections and encased in concrete
TR60+ Metal Deck /
 All external beams to be encased in concrete. LYSAGHT SMART
DECK to withstand
Steel Deck Sheeting
design load.

 Profiled deck sheets of TR60+ Metal Deck of E350 Grade will be used
for metal decking of composite slab systems.

Fire Resistance

According to fire resistance Type 1 Construction has been adopted for the
structure. The fire rating considered for various structural elements for
Type 1 construction are as follows.

Deck Slab & Floor slab, Staircase : 2 hrs

Column Shear walls & Lift walls : 4 hrs
Beam : 3 hrs

Crack Width
The concrete used for Raft, retaining walls, podium slab & terrace slab mixed
with poly propylene fiber to minimize the cracks. The base slab, Raft and
Retaining walls are protected by water proofing agents against soil/water.
These elements shall be designed for limiting crack width of 0.2mm. the water
retaining structures shall be designed for limiting crack width of 0.1mm.
All other structural elements shall be designed with limiting crack width of
0.3mm.

Waterproofing

Following water proofing specification shall be followed for respective

structural elements:

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 ITEM SPECIFICATION

Pile cap & Raft 1.2mm thick self-adhesive HDPE membrane.

Retaining wall Crystalline waterproofing

Two coat of acrylic
Toilet, Kitchen, AHU rooms Single component poly urethane polymer
& wet areas

Water tanks Food grade epoxy coating

Terrace Two component polyurethane + underdeck

insulation Under deck insulation
not considered as
most of the terrace is
Podium slab Two component polyurethane
covered with shed.

Waterproofing shall also be considered for sumps, drainage chambers, lift

pits, refuge terrace, all wet areas etc.

All water tanks and sumps will be lined with white glazed tiles fixed with
food grade, non-toxic adhesive suitable for submerged conditions.
FOUNDATION SYSTEM -- refer Last page
8.0 NOMINAL COVER TO REINFORCEMENT

From Durability requirement, exposure condition is considered as mild for

Structural elements above ground level and moderate for Structural elements
below ground level. The Nominal cover to reinforcement to meet Durability
requirement shall be as follows:

Moderate - 30 mm
Mild - 20 mm
For two-hour fire resistance, the nominal cover to meet the durability
requirement shall be as follows:

Columns: 40 mm or dia of longitudinal reinforcement whichever is greater.

Shear wall: 30 mm
Retaining wall: 40mm (earth side); 30mm (building side)
Raft: 50 mm
Pile cap: 75 mm
Conventional Slabs: Bottom & Top cover shall be 25mm & 20mm respectively.
For any other elements not specified above, nominal cover shall be as per
the clause 26.4 of IS: 456-2000.

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9.0 EXTERNAL WORKS

Below listed external works are considered in scope of work.

• Security cabins.

• Front side compound wall with gate. For side and rear boundary wall,
the following works to be considered – removal of plaster, replastering
and painting with texture paint.

• VDF concrete Roads around the proposed building. Front road to be 40

mm thick flame finish granite. Other elements of road to include kerb
stone, plinth protection, road crossings, speed breakers,
thermoelastic paint for directions and road marking.

• Storm water drains along with water harvesting pits and sump of
adequate capacity with automatic pumping system.

• Parking area with VDF concrete

• LPG bank room, Biomedical waste handling room, Organic waste Convertor
room.

• Foundation for Compact substation, DG set, Chillers and cable trenches,

chillers for medical equipment etc. as shown in drawings.

• HT room & Metering room, cable trenches for HT and LT cables

• Fencing and gate for liquid oxygen tank

• Hatch for taking in equipment to basement.

10.0 DESIGN STANDARDS:

The relevant Indian Standard Codes, as given below, shall be followed for
structural design:

Sr Code Description

Code of Practice for Design Loads (other than

IS-875 (Part 1) –
1. earthquake) for buildings and structures – Unit weights
1987
of buildings materials and stored materials.

Code of Practice for Design Loads (other than

IS-875 (Part 2) –
2. earthquake) for buildings and structures – Imposed
1987
loads.

IS-875 (Part 3) – Code of Practice for Design Loads (other than

3.
2015 earthquake) for buildings and structures – Wind loads.

IS-875 (Part 4) – Code of Practice for Design Loads (other than

4.
1987 earthquake) for buildings and structures – Snow loads.

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 Sr Code Description

Code of Practice for Design Loads (other than

IS-875 (Part 5) –
5. earthquake) for buildings and structures – Special loads
1987
and load combinations.

6. IS: 456 – 2000 Code of Practice for Plain and Reinforced Concrete.

Specification for High Strength Deformed Steel Bars and

7. IS: 1786 – 2008
Wires for Concrete Reinforcement.

Specification for Mild Steel and Medium Tensile Steel

IS: 432 (Part 2)
8. Bars and Hard Drawn Steel Wire for Concrete
- 1982
Reinforcement – Hard Drawn Steel Wire.

Ductile detailing of reinforced concrete structures

9. IS: 13920 - 2016
subjected to seismic forces - Code of practice

Uncoated Stress Relieved low relaxation seven-ply strand

10. IS: 14268 - 1995
for Pre-stressed Concrete – Specification

11. IS: 2062 – 1999 Steel for General Structural Purposes. Specification.

12. IS: 1161 – 1998 Specification for Steel tubes for Structural Purposes.

13. IS: 800 – 2007 Code of Practice for General Construction in Steel.

14. IS: 1893 – 2016 Criteria for Earthquake resistant design of structures.

11.0 EXCLUSIONS:

Below mentioned items are not considered in scope of work.

 Modification & rectification in Existing building.

 Demolishing of existing building & external services.
 Stack parking structure.

FOUNDATION SYSTEM -
Proposed Structure is having a basement of minimum 5.2m depth from ground level.
Due to excavation for basement a relief of soil (W) will be there at foundation level.
Case 1 -If the structural load (W1) ≤ W the phenomenon called floating raft foundation.
Case 2 -If structural load (W1) > W , one has to check whether the soil can sustain that net load,this
phenomenon is called Compensatory raft foundation.

In proposed Structure Case 2 exists and the soil beneath the foundation is having SPT value 12~15.
So in that case foundation to be designed for remaining load (W2 ) i.e. difference of Structural Load and
Relief of the soil (W2= W1-W).
Since as per soil report SPT value is about 12~14, we are going for Compensatory raft instead of Pile.

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