Design Basis for Civil and Structural

SPECIFIC DESIGN REQUIREMENTS [CIVIL]

CONTENT

SPECIFIC DESIGN REQUIREMENTS [CIVIL]

1. INTRODUCTION

This section outlines the followings:

1. A brief description of Soil Characteristics.

• Design considerations for Reinforced Concrete Structures.

• Design considerations for Foundations.

• Roads.

2.00.00            GEO-TECHNICAL SYSTEM

Detail soil investigation, as required, to be carried out for foundation design of various facilities.

Soil characteristics and parameters to be adopted in final design, the successful bidder is required to do detail geotechnical investigation work as part of the contract to verify/generate data so required.

It should be noted that nothing extra whatsoever on account of variation between soil data annexed in this specification and that found by detailed geotechnical investigation to be carried out by bidder shall be payable.

The design of foundation shall be carried out by Limit State or working stress method as per the provisions of IS-456 (Latest) and on the basis of the soil investigation Report done by the Bidder. The type, size, depth of the foundation shall be based on the approved soil investigation report of Bidder/Owner’s soil investigation report whichever is conservative.

3.00.00                    LOADS

All structures and portions thereof shall conform to the latest revision of relevant Indian Standard specifications and also to the various other technical requirements.

All structures shall be designed to sustain within the stress limitation as specified in the Code, all dead loads plus assigned live, equipment, wind, seismic or other design loads.

a)               Dead Loads

Dead load shall include the weight of all structural components and

architectural appurtenances incorporated in the structures plus hung loads and any other permanent, externally applied load. This should also include equipment dead load. The content of tanks, Ash storage bins shall be measured at full capacity for this purpose. Hung loads and the contents of tanks and bins shall be listed separately so that they can be excluded from dead load when dead loads are acting as stabilizing loads for uplift.

The following unit weight of material shall be considered for computation of loads. Loads given in IS: 875 (part-I) shall be made use of for material not listed below.

Materials                                                         Unit weight

Plain cement concrete                        :           24.0 kN/cum Reinforced cement concrete  :           25.0 kN /cum Structural steel                       :           78.5 kN /cum

Brick work                                           :           19.0 kN /cum

Cement plaster                                    :           21.0 kN /cum

Floor Finish                                         :           24.0 kN /cum

Coal                                                     :           12.0 kN /cum

Fly Ash                                                :           16.0 kN /cum

Bottom Ash                                         :           16.0 kN /cum

b)               Live Loads

Live loads in different areas shall include dust loads, minor equipment loads, cable trays, small pipe racks/hangers, operation/maintenance loads etc. The loads considered shall not be less than those specified in IS: 875 (Part II).

The loads listed hereunder are minimum loads for the areas involved. Special use areas shall be investigated and loading revised upward as necessary.

Hung loads shall be based on minimum loading equivalents of 1.0 kN/Sq.m for piping and 0.5 kN/Sq.m for electrical, ventilation and air conditioning. Loadings resulting from concentrations of facilities in specific areas shall be substituted where listed base loading is excluded.

i)       Buildings

1. Roofs :

Inaccessible roof (Flat) :         1.5 kN/Sq.m + hung loads,

if any + 0.5 kN/Sq.m (dust load).

Accessible roof where

equipment are placed      :       5 kN/Sq.m + hung loads,

if any + 0.5 kN/Sq.m (dust load).

Accessible roof

Without equipments        :         1.5 kN/Sq.m + hung loads,

if any + 0.5 kN/Sq.m (dust load).

Inclined roof                    :         As per IS: 875 (Part 2) –

• Stairs & Platforms           :        5.0 kN/Sq.m

• Corridors                        :        5.0 kN/Sq.m

• Removable gratings, chequered plates,

walkways etc.                 :        5.0 kN/Sq.m

• Office, Laboratory, Conference rooms and other non-plant areas

etc.                                  :        5.0 kN/Sq.m

ii)     Buildings floors

1. Ground Floor               :           10 kN/Sq.m

• Cable Spreader Floor :            7.5 kN/Sq.m

• Equipment floor/

Operating Floor           :           15 kN/Sq.m / As supplied by

Equipment manufacturer, whichever is higher

• Office Floor                  :           5 kN/Sq.m

• AHU room floor            :           15 kN/Sq.m

• All other Floors            :           10 kN/Sq.m

iii)   Non-Plant Buildings

1. Floors with equipment:            10 kN/Sq.m

• All other floors             :           5 kN/Sq.m

iv)   Underground Structures/Trenches/pits

Minimum surcharge shall be 20 kN/Sq.m. For structures in vicinity of roads and heavy vehicular movement surcharge shall be considered as applicable as per loading specified elsewhere in this specification. Trenches/pits inside building shall be designed for a surcharge equal to Live Load intensity of Ground Floor or 15 kN/Sq.m whichever is greater.

v)     Covers for Trenches / Channels

Self-weight of top slab and a uniformly distributed load of 4.0 kN/Sqm

on each panel or one 0.75 kN central point load, whichever is critical, shall be considered. At road crossings, the covers shall be designed for vehicular movements as per IRC standards

vi)      Roads

Design of R.C roads shall be in accordance with Indian Road Congress standard IRC 15 & IRC-58.

vii)      Road Culverts and its allied structures including Road Crossing of Trenches.

At all road crossings RCC box culverts along with manholes on both sides shall be used. Such road culverts and its allied structures including R.C.C. Pipe Crossings & Road Crossing of Trenches shall be designed for Class `AA’ loading (wheeled and tracked both) and to be checked for Class `A’ loading as per IRC standards.

c)               Equipment Loads

1. All equipment, tank and piping design loadings shall include Hydraulic Testing loads.

1. Air and gas duct loadings shall include weight of insulation, duct attachments, dust accumulation loads, seismic, wind and other loads as applicable.

1. Weight of equipments, ducts, tanks, pipes, conduits etc. supported by structure shall include maximum possible loading conditions i.e. flooded material contents and associated impacts, test loadings, anchorage and constraint effects.

1. All structural components shall be designed to accommodate anticipated concentrated loads which shall or may be applied during the life of the plant.

Where both concentrated and uniform loads cannot act simultaneously, the structure or component shall be analyzed for both conditions of loading and shall be designed for most critical condition.

• Jet forces resulting from guillotine type pipe ruptures shall be considered in the design, if it is of high magnitude. Jet force to be considered shall be equal to the product of the pipe cross section and the internal design pressure applied on an area equal to the pipe cross section.

• Bursting force due to any accidental case shall be considered in the structure as applicable for design of structures.

d)               Wind Loading

Wind loading shall be in accordance with Indian Standard Code IS:875

(Part 3) (Latest Revision) for a basic wind speed of 265 KM/HR.. Terrain Category-2 shall be considered for all structures.

Risk coefficient (k1) shall be considered as 1.08 for all structures.

e)               Seismic Loading

The lateral forces shall be established in accordance with the recommendations of IS:1893 (Latest Revision). The site falls in Zone-III as identified in the map in IS:1893 and hence seismic forces would be considered accordingly for the structures and buildings. Importance factor shall be taken as per latest versions of IS:1893 parts.

f)                Temperature Loads

The structures shall be designed to withstand stresses due to fifty (50) percent of the total temperature variation. The total temperature variation for temperature loading should be taken as two thirds (2/3) of the average annual variation in temperature. The average maximum annual variation for this purpose shall be taken as the difference between the mean daily minimum temperature during the coldest month of the year and mean daily maximum temperature during the hottest month of the year.

Mean Daily minimum ambient temperature during coldest month of the year = 11.3°C

Mean Daily maximum ambient temperature during hottest month of the year = 45°C

Expansion and contraction due to changes of temperature of materials of a structure shall be considered and adequate provision shall be made for the effects produced as per provision in the relevant IS codes.

g)               Earth Pressure Load

Earth pressure for all underground structures shall be calculated using coefficients of earth pressure at rest, coefficient of active or passive earth pressure (whichever is applicable).

However, for the design of sub-structure of pump house and underground liquid storage tanks earth pressure at rest shall be considered with coefficient of earth pressure at rest shall not be less than 0.50.

In addition to earth pressure and ground water pressure, etc., surcharge load shall also be considered for the design of all underground structures including channels, sumps, cable & pipe trenches, etc., to take into account the vehicular traffic in the vicinity of the structure. Intensity of Surcharge Load shall be considered as 2.0 t/sq.m in general unless mentioned otherwise.

h)                 Crane Loads

Crane girders and supporting columns shall be designed for vertical and horizontal forces (including impact forces) as per crane vendor’s data. All lifting beams and monorails shall have their design loads increased for impact factor as mentioned hereinafter. For frame analysis, the lateral crane surge shall be applied on one side of the frame at a time and in either direction.

Impact Factor

Loads for cranes shall be taken as per IS:875/IS:807 (Latest Revision). The minimum impact factor to be used in design shall be as follows:

Crane loads

1. For vertical force, an impact factor of 25% of the maximum crane wheel load for crane girder 10% for column and foundation.

• A lateral crane surge of 10% of the weight of the trolley plus lifted load applied at the top of each rail.

• A horizontal surge of 5% of the maximum static wheel loads of the crane applied at the top of the rail in longitudinal direction.

j)                 Construction Loads

The integrity of the structures shall be maintained without use of temporary framing struts or ties and bracing as far as possible. However, construction or crane access considerations may dictate the use of temporary structural systems. Special studies shall be made and documented to ensure stability and integrity of the structures during any periods involving use of temporary bracing systems.

k)               Other Loads

Stresses imparted to structures due to differential settlements, variation of water table, erection and maintenance load, creep and shrinkage shall also be considered in design of all structures.

3.01.00                    Stability of Structures

Design shall be checked against buoyancy due to the ground water during construction and maintenance stages for structures like underground tanks, pits trenches, basements, etc. Minimum factor of safety of 1.25 against buoyancy shall be ensured considering empty condition inside and ignoring the superimposed loading. For purpose of calculating downward load due to any overburden, only the mass located vertically above the projected area shall be taken into consideration.

All building sub-structures including pump houses shall be checked for sliding and overturning stability during both construction and operating conditions for

various combination of loads. Factor of safety for these cases shall be taken as mentioned in IS:456 and other relevant IS codes However, following minimum factor of safety shall be followed.

1. Factor of safety against overturning due to wind, seismic or other lateral load shall be 1.5 minimum.

• Factor of safety against sliding shall be 1.5 minimum.

• Factor of safety against uplift due to hydrostatic forces shall be 1.25 and due to any other loads shall be 1.5.

Stability of the structure shall also be investigated for loading conditions during construction, repair or other temporary measures. Lower factor of safety may be used for such loading conditions as per relevant IS codes.

In case where dead load provides the restoring force, only 0.90 times characteristic dead load shall be considered. Imposed loads shall not be considered as restoring force.

Ground water table shall be considered at Plant Finished Grade Level for design of foundations and all underground structures.

3.02.00                    Load Combinations

Buildings and structures shall be designed to resist the load stated in the previous section acting in the following combinations.

While designing consideration shall be given to the following load combinations:

1. DL + LL

1. DL + LL + Equip +_ TL

1. DL + LL + Equip + Cb + CtLA_+  CS +_ TL

1. DL + LL + Equip + Cb + CtLB_+  CS _+ TL

• 0.9DL  +_  EL (for DL only) +_ TL

• 0.9DL  +_  WL1 +_ TL

• 0.9DL  +_  WL2 +_ TL

• DL + *LL + Equip + Cb + Ct  +_  EL +_ TL

(* Appropriate portion of LL which is considered for working out EL shall only be taken)

1. DL + LL + Equip + Cb +Ct _+  (WL1) +_ TL

• DL + LL + Equip + Cb +Ct  _+  (WL2) +_ TL

Where the above loads are :

Appropriate impact factor shall be considered as per IS:875 (Part 2) (Latest Revision) while calculating crane loads.

In calculating wind loads, appropriate internal thrust / suction shall be considered along with external pressures as per IS:875 (Part 3) (Latest Revision). All possible load conditions considering external and internal pressures shall be considered in analysis and design for the combinations as stated above to assess worst effect on whole structure as well as its components.

Appropriate allowable increase in permissible stresses as per IS codes, may be taken only under normal loads along with wind and seismic conditions. However, members which are designed primarily to resist wind, no increase in permissible stresses shall be permitted.

Applicable load factors to be used for design of RCC structures by Limit State Method as per IS:456.

Load Combinations for Underground Structures

Following loading conditions shall be considered in addition to the loading from super structure for the design of silo, tunnel conveying structures, pump house, channels, sumps, tanks, reservoirs, trenches and other under-ground structures.

Only liquid pressure from inside and no earth pressure and ground water pressure, and surcharge pressure from outside (applicable only to the structures which are liable to be filled with water or any other liquid).

Earth pressure, surcharge pressure and ground water pressure from outside and no water pressure from inside.

Base slab of the pump house shall be designed for the condition of different combination of pump sumps being empty during maintenance stages with maximum ground water table. Intermediate dividing piers of pump sumps and partition walls in channel shall be designed considering water on one side only and the other side being empty for maintenance.

Design shall also be checked against buoyancy due to ground water during construction and operation stage. Minimum factor of safety as per IS:3370 (Latest Revision) against buoyancy shall be ensured considering empty condition ignoring superimposed loads.

3.03.00            Design Concepts

Wind and seismic forces shall not be considered to act simultaneously.

`Lifted Load’ of monorail shall not be considered during seismic condition.

For design of all underground structures/foundations, ground water table shall be considered at the Finished Ground Level.

If R.C.C. floors and roofs except those cast over metal decking are assumed to act as diaphragm transmitting lateral loads to braced bays then main beams/girders shall be provided with shear connectors. However, whenever large/more number of cutouts is provided in the floor slab, horizontal floor bracings shall be provided below slab to transfer horizontal force to columns without considering diaphragm action from slab. Shear connectors shall also be provided over beams having R.C.C. slab on one side and opening /chequered plate / grating on other side.

For R.C.C. roofs cast over metal decking, horizontal bracings must be provided below slab to transfer horizontal force to columns.

PTFE (Poly tetra Fluoroethylene) bearing shall be provided where horizontal loads not to be transferred.

For calculation of seismic load, equipment load shall be considered as Dead Load.

Whenever any structure under this contract shall carry or receive additional load from the work of any other contract, the structures under this contract shall be provided with sufficient margin to carry the above load, details of which shall be finalized during detail engineering.

Gratings / chequered plates shall not be considered as restraining members for compression flange of beams/girders. Diaphragm action shall also be not considered in design. Adequate horizontal bracings to be provided.

4.00.00                    DESIGN OF REINFORCED CONCRETE STRUCTURES BY BIDDER

1. Reinforced Concrete Structures shall be designed in accordance with the requirements of IS-456 (Latest Revision) & IS-875 (Latest Revision) or as specified in this specification for all possible combination of loads,

e.g. dead load, live load, crane/monorail loads, wind or seismic loads, soil loads and surcharge loads, etc.

The following grades of concrete as per IS-456 shall generally be used.

• Reinforcing bars shall be TMT bars of minimum grade Fe 500 conforming to IS-1786 (Latest Revision). TMT bars from manufacturer like SAIL, TATA, RINL or JINDAL shall only be used for all type of construction.

• c) Higher grade of Portland slag cement (PSC) / Sulphate resisting cement (SRC)/Sulphate resisting Portland cement (SRPC) namely Grade 43 shall be used for construction of all RCC structures and foundations. Cement from manufacturer like Ultratech/Ambuja/ACC shall only be used all type of construction.

• The design of R.C. Structures shall be carried out by limit state or working stress method as per the provisions of IS-456 (Latest Revision).

• Concrete tanks/water retaining structures shall be designed in accordance with the recommendation of IS-3370 (Latest Revision) as un-cracked section.

• Grouting material :

Grouting shall be done with Conbextra GP-2 or equivalent for Equipment foundations and Conbextra GP-1 or equivalent for all structural column bases. For pipe-supports grouting shall be done with 1:1:2 cement-sand – 6mm down stone chips.

• For reinforcement detailing IS:5525 (Latest Revision) and SP:34 shall be followed.

• The walls shall be provided with reinforcement on both faces for sections 150 mm or more, even if not required from design consideration.

1. Liquid Retaining Structures

RCC water retaining structure shall be leak proof and designed as un- cracked section in accordance with IS:3370 (Latest Revision) by working stress method.

All water retaining / storage structures shall be designed assuming liquid up to the height of wall irrespective of provision of any over flow arrangement.

In all liquid retaining structures leak-tightness shall be ensured and guaranteed. To achieve the same, methodology in design and construction in the way of providing PVC water bars at construction/expansion joints and/or injection grouting, usage of admixture in concrete or any such method should be adopted.

All underground water retaining/conveying system structures shall have plasticizer cum waterproofing cement additives conforming to IS:9103 (Latest Revision) of any make approved by Owner. In addition, limits on permeability as given in IS:2545 (Latest Revision) shall also be met with. The concrete surface of these structures in contact with soil shall be provided with minimum two coats of bituminous painting of grade 85/25 conforming to IS:702 (Latest Revision) @ 1.7 kg/sqm (min.) for water/damp proofing. Storm water drains shall not be provided with bituminous paint and weep holes also shall not be provided in storm water drains.

5.00.00            FOUNDATION DESIGN

The design of foundation shall be carried out by Limit State or working stress method as per the provisions of IS-456 (Latest Revision) and on the basis of the soil investigation Report done by the Bidder.

Foundation shall be checked for safety against overturning, sliding and uplift. High ground water level up to final graded ground level shall be considered to take into account buoyancy effect.

RCC deck of any vibrating equipment (if any) shall be supported on vibration isolation system consisting of steel helical spring units and viscous dampers which in turn will be supported on RCC foundation system.

Pile foundation, shall be designed in accordance with IS:2911(Part-I / Sec-I, II and III) (Latest Revision).

The type, size, depth of the foundation shall be based on the approved soil investigation report of Bidder/Owner’s soil investigation report whichever is conservative.

5.01.00            Foundations

Foundations for Buildings and structures shall be designed to resist forces and moments, caused by vertical loads and by wind or seismic loads, based on static and dynamic analysis done for those structures. The foundation sections shall be sized and reinforced adequately for moments and shear stresses.

Common foundation should be provided for columns both side of the expansion joint and shall be designed for loading on both columns.

5.02.00                    Open Foundations

In case open foundations are adopted, the following shall be adhered to:

1. Minimum width of foundation shall be 1.0 m.

• Minimum depth of foundation shall be 1.0 m below NGL.

• It shall be ensured that all foundations of a particular structure/ buildings/facility shall rest on one bearing stratum, i.e. either overburden or rock.

• Wherever the intended bearing structure is weathered rock but the actual stratum encountered during foundation excavation consists of both overburden soil and weathered rock at founding level, under such cases either the foundation shall be lowered completely into the weathered rock or the overburden soil up to the weathered rock level shall be removed and built up through PCC up to designed foundation level.

• The net allowable bearing pressure values to be adopted for design upon Owner’s approval shall correspond to total permissible settlement as mentioned under para “permissible settlement of foundations” or the permissible settlement from functional requirement, whichever is more stringent.

• Permissible settlement of foundations: The total permissible settlement and differential settlement shall be governed by IS: 1904 and IS: 13063 and from functional requirements, whichever is more stringent. However, total settlement shall be restricted to the following :

1. All facilities in the Plant area, ducts,

Equipment foundation                                           – 25 mm

1. All foundations in miscellaneous building including, isolated/strip continuous/

Raft foundation                                                      – 40 mm

1. Other footings of width up to 6m                            – 40 mm

1. Other footings of width greater than 6.0 m (raft) – 75 mm

• Footings on rock (if any)                                        – 12 mm

In case the total permissible settlement is to be restricted to less than as above specified from functional requirements, then the net allowable bearing pressure shall be reduced / reviewed accordingly in consultation with Owner.

The total permissible settlement and differential settlement of the foundations shall be governed by IS:1904 (Latest Revision), IS:13063 (Latest Revision) and from functional requirements whichever is more stringent.

Maximum allowable total settlement should be restricted to 40 mm for all other foundations.

5.03.00                    Pile Foundations

In case piles are adopted, following shall be adhered to:

1. The pile foundation shall be of RCC, Cast-in-situ bored, precast/cast-in- situ driven pile as per IS: 2911 (Latest Revision). Bored piles shall be installed by using rotary hydraulic rig. Three-stage flushing of pile bore shall be ensured, by airlift technique or any other internationally accepted method duly approved by the Owner.

• The minimum diameter of pile shall be 450mm for cast-in-situ and 300mm for precast piles. The uplift and lateral load capacity shall be established by field test.

• Only straight shaft piles shall be used. Minimum cast length of pile above cut-off level shall be 1.0 m.

• The bidder shall furnish design of piles (in terms of rated capacity, length, diameter, termination criteria to locate the founding level for construction of pile in terms of measurable parameter like (SPT &SCPT value, set criteria etc.), reinforcement for job as well as test piles, etc.) for Owner’s approval.

• The piling work shall be carried out in accordance with IS: 2911 (Relevant part) (Latest Revision) and accepted construction methodology. The construction methodology shall be submitted by the Bidder for Owner’s approval.

• Number of initial load tests to be performed for each diameter and rated capacity of pile shall be as under:

Vertical

Lateral                                     Minimum of 1 Nos. in each mode. Uplift

The initial pile load test shall be conducted with test load upto 2.5 times the estimated pile capacity. In case of compression test the method of loading shall be cyclic as per IS: 2911 (relevant part) (Latest Revision).

• Number of   routine pile load tests to   be performed for each

diameter/allowable capacity of pile shall be as under:

1. Vertical- 2.0 % of the total number of piles provided.
   1. Lateral – 2.0 % of the total number of piles provided. Iii) Uplift – 2.0 % of the total number of piles provided.

The routine tests on piles shall be conducted up to test load of one and half times the allowable pile capacity. The Owner shall approve piles for routine load tests. Routine load tests may be done by conventional method as per IS: 2911 (Part-4) (Latest Revision).

In case, routine pile load test shows that the pile has not achieved the desired capacity or pile(s) have been rejected due to any other reason, then the Bidder shall install additional pile(s) as required and the pile cap design shall accordingly be reviewed and modified, if required, without additional cost to the Owner.

• Testing of piles and interpretation of pile load test results shall be carried out as per IS: 2911 (Part-4) (Latest Revision). Bidder shall ensure that all the measuring equipment and instruments are properly calibrated at a reputed laboratory/ institute prior to their use. Additional measurement for pile movement shall also be done.

1. Low Strain Pile Integrity test shall be conducted on all test piles and job piles. This test shall be used to identify the piles for routine load test and not intended to replace the use of static load testing.

5.04.00                    Other Requirements

1. In case of high ground water table, for excavations comprehensive dewatering arrangement shall be required. Scheme for dewatering and design with all computations and back-up data of dewatering and sheet pilling shall be submitted for Owner’s information.

1. The founding level for trenches/channels shall be decided as per functional requirement. The bottom of excavation shall be properly compacted prior to casting of bottom slab of trenches/channels.

1. Excavation for open foundations shall be covered with PCC immediately after reaching the founding level. In case of any local loosening of soil at founding level during excavation, the same shall be removed and compensated by PCC of Grade M15. The foundation pits shall be maintained dry during the complete construction period by means of suitable dewatering systems.

1. Backfilling, around foundations and bottom of pipes, thrust blocks, etc. shall be carried out with approved material in layers not exceeding 30 cm thickness and each layer shall be compacted to 90% standard proctor density for cohesive soil and to 75% of relative density for non- cohesive soils.

• Excess/surplus excavated material shall be disposed of by the Bidder as per the instructions of the Owner up to a lead of about 5 km.

• CBR tests for rigid / concrete pavement design shall be carried out by Bidder after earth filling has been completed, if applicable.

5.05.00            Foundation Bolts

Foundation / Anchor bolts shall be of M.S rods conforming to IS: 432 Grade- 1

/ IS:2062 Grade A. The property class of the foundation bolts shall be minimum of 4.6.

6.00.00            GENERAL REQUIREMENTS

6.01.00            Minimum Thickness of Structural Elements

The following minimum thickness shall be followed :

Pile caps                                                                                              900 mm

Suspended floor / slab / walkways / canopy slabs, etc.                                                                                                            150 mm Ground floor slab (non-suspended)                                                                                                            150 mm

Water Retaining slabs / walls                                                               200 mm

Cable / pipe trenches / underground pits /

Launder walls and base slab                                                               150 mm

All footings (including raft foundations)                                                300 mm

Parapets                                                                                              125 mm

Sunshades at edge                                                                             75 mm

Pre-cast louvers / fins                                                                          50 mm

Pre-cast trench cover slabs / floor slabs / louvers                                100 mm

Paving                                                                                                 150 mm

Basement walls and base slab                                                                                                            250 mm Underground reservoir

Below ground                                                                                      250 mm

Above ground                                                                                      175 mm

From fire resistance point of view minimum thickness of reinforced concrete members shall be as per Fig 1 or Table 16a of IS 456 (Latest Revision) or specified above, whichever is higher.

6.02.00                    Minimum Heights for Pedestals/Encasements of Steel Columns Pedestals to Steel Columns for building structures:

In case the top of pedestal is kept at a lower level so that the column base plate together with gussets and stiffeners remain below finished floor level (FFL) the column bases as well as the column sections shall be encased in concrete above FFL as per following.

1. Open area                               :           300 mm above paved level

• Covered area                          :           300 mm above FFL

Stair and ladder pedestal shall be kept 200 mm above the finished floor level.

Pedestals to Steel Columns for Equipment structure:

1. Equipment in open area            :           as required (300mm min)

• Equipment in covered area       :           as required (150 mm min)

• Structures and equipment         :           as per vendor’s data supplied by vendor                  subject to minimum as

specified above

6.03.00            Ground floor slab-on-grade

Ground floor slab-on-grade shall be minimum M-25 grade RCC construction laid over minimum 75mm thick lean concrete. Minimum consolidated 230mm thick graded stone (63mm down size) soling with interstices filled with sand and compacted mechanically, shall be provided as sub-base below lean concrete. The sub-base shall be laid over rammed and well-compacted earth fill or hydraulically compacted sand fill as specified elsewhere in this specification unless the thickness required from design consideration is more.

The ground floor slab shall be of minimum 150 mm thick with double layer reinforcement of 8mm (minimum) dia at the rate of 200 (maximum) c/c both ways.

6.04.00            Stairs, Platforms, Handrails

All internal stairs, platforms and walkways shall either be of RCC or minimum 6mm thick chequered plate construction. All outdoor stairs, platforms and walkways shall either be of RCC or minimum 40mm thick grating.

All handrails made of MS Galvanized hand railings with 40 mm NB (medium) main posts and 32 mm NB (medium) as horizontal rails as per IS:1161(Latest Revision) with toe guard shall be provided.

7.00.00            ROADS

Roads wherever required for transportation or access to any facilities shall be constructed by the successful bidder. The roads shall be made of RCC.

Geometric design of road shall be done in accordance with Indian Road Congress Standard IRC-73. The ruling gradient for roads in longitudinal direction shall be 1 in 25. Normally roads shall have much flatter gradient. Transverse camber of 1 in 40 shall be provided.

A detailed CBR test, shall be carried out as per the procedure outlined in IS-2720 (Part-XVI)(Latest Revision). CBR test shall be carried out in remoulded soil samples under soaked condition.

Pipe, slab culverts, or RCC box culverts, as suitable, shall be provided at road crossings for drainage, pipes, cable trenches etc.

8.00.00            DRAINAGE

Open RCC rectangular drains shall be provided for storm water. The thickness of sides & bottom shall be minimum 125 mm or as per design considerations whichever is higher. RCC culverts shall be provided for road and rail crossing if any. Drains shall be provided on both sides of the roads.

Inside surface of the drain will have smooth neat cement finish over with screed concrete. Invert of the drain shall be decided in such a way that the water can easily be discharged to the recommended nearest outfall outside the plant boundary. The minimum slope of the drain shall be 1:1000 longitudinally to take care of the silting problems. It is recommended to maintain the maximum velocity within 1.2 m/sec.

9.00.00                    MISCELLANEOUS DESIGN / CONSTRUCTION CRITERIA

1. All masonry walls from ground floor shall be placed on reinforced concrete grade beams. However, light internal partitions may be placed on ground floor slab. Minimum embedment of the grade beam below grade level shall be 500 mm.

• The steel column base plate along with stiffening gusset plates shall not be protruded above floor level.

• For exposed areas the columns shall have a minimum encasing of 300 mm above paved level.

• Ramps for building entrance shall be cast in situ RCC slab and the slope of ramps shall not be more than 1 (vertical) to 6 (horizontal) or to suit at site.

• Minimum 75 mm thick lean concrete M-10 shall be provided below all underground structure, trenches etc., to provide a base for construction.

• All buildings shall have RCC/steel framed super structure. All walls shall

be non-load bearing infilled panel walls.

• Duct banks consisting of PVC/GI conduits for cables shall be provided with reinforced concrete encasing of M20 grade. The minimum depth of top of duct bank from grade level shall be 500mm.

• Angles 50 x 50 x 6 mm (min.) with lugs shall be provided for edge protection all round of cut-outs/opening in floors, edge of drains supporting grating covers, edges of RCC cable/pipe trenches, manholes supporting covers, supporting edges of pre-cast covers and any other places where breakage of corners of concrete is expected.

• Trenches located outside building shall project at least 100mm above the finished formation level so that no storm water shall enter into the trench. The bottom of the trench shall be sloped suitably for draining out the collected water into the sump pit. The pre-cast covers shall be of minimum M-20 grade and shall not weight more than 65 kg. Lifting hooks shall be provided in the pre-cast covers. The minimum drainage slope along line shall be 1 in 500.

1. For open drains concrete lining of minimum M20 grade on sides & bottom shall be provided. The thickness of lining shall be minimum 100mm or as per design consideration whichever is higher.

1. All underground concrete structure such as basement, sumps water-retaining structure shall be designed for water tightness.

1. All underground concrete structure like basements, sumps, water retaining structure etc., shall have plasticizer cum water-proofing cement additive conforming to IS-9103 (Latest Revision). In addition limit on permeability as given in IS-2645 (Latest Revision) shall also be met with. The concrete surface of these structures in contact with earth shall also be provided with two coats of bituminous painting for water/damp proofing. In case of water leakage in the above structures, injection method shall be applied for repairing the leakage.

1. All joints, including construction and expansion joints for the water retaining structure and others below subsoil water level shall be made water tight by using PVC ribbed water stops with central bulb. The minimum thickness of PVC water stops shall be 6 mm and minimum width shall be 230mm.

1. All mild steel parts used in the water retaining structures shall have anticorrosive epoxy based paint or equivalent.

1. Anti-termite chemical treatment shall be given to column pits, wall trenches, foundations of buildings, filling below the floors, switchyard area etc., as per IS-6313 (Latest Revision) and other relevant standards.

1. Concrete hume pipes for underground service     shall of class NP3/NP2

as per IS-458 (Latest Revision).

1. For all buildings suitable arrangements for draining out of water collected from equipments, blowdowns, leakages, floor washing, fire-fighting etc., shall be provided for each floor.

1. All walls and slabs shall have two layers of reinforcement for section having thickness 150 mm and above.

1. All gratings shall be made of 40×6 thick flat unless noted elsewhere in the specification. Stairs treads made of grating shall be provided with non-skid abrasive nosing.

• Unless stated elsewhere specifically in this specification, the finished floor level of any building shall be at least 500 MM from finished grade level.

• Sealing of joints shall be done by two part polysulphide sealant and shall be from approved manufacturer conforming to IS: 12118 (Latest Revision). Material shall consist of polysulphide polymer and a curing agent.

If any similar design criteria mentioned elsewhere in this specification contradict the above, the stringent of the criteria shall be adopted for design.

SPECIFIC DESIGN REQUIREMENT [STRUCTURAL]

CONTENTS

SPECIFIC DESIGN REQUIREMENT [STRUCTURAL]

1. STRUCTURAL STEEL DESIGN

1. Structural steel design shall be carried out as per the National Building Code with specific consultation to IS-800 (Latest Revision) unless noted otherwise.

• Lateral forces along the length of the building shall be resisted by bracings in horizontal and vertical frames.   The transverse lateral load shall be resisted by stiff jointed frame action. Additional bracing or moment connection shall be used to assure stability of the structures.

• Structural steel will conform to Grade E350 / E250 of quality (A/BR/B0), semi killed / killed as per IS: 2062 (latest) for rolled steel members or plates. All structural steel plates and sections shall be procured from any make approved by Owner.

For Crane/Monorail Steel will confirm to Grade E350 / E250 of quality C (Killed).

• Shop connections shall be all welded and field connections shall generally be bolted unless specified otherwise. Field bolts, wherever provided, shall be high tensile of 20 mm dia. or of higher diameter and of property class 8.8 as per IS-1367 (Latest Revision) for all major connections. The bolted joints shall be designed for friction type connection and the H.T. bolts shall be tightened to develop the required pretension during their installation. However, the nominal connections in the field like purlins, stairs, wall beams etc. shall be done by 16 mm dia. M.S. black bolts (minimum 4.6 grade) conforming to IS-1363 (Latest Revision) unless specified otherwise.

• Welding shall be in accordance with the recommendations of IS-816 – Code of Practice (Latest Revision) for use of metal arc welding for general construction in mild steel and IS-9595 (Latest Revision) – Recommendation for Metal Arc Welding of Carbon and Carbon Manganese Steels. Built-up members shall be fabricated using submerged arc welding procedure unless manual arc welding is specifically required. All butt welds in plate girders and columns shall be full penetration.

All butt welds shall be radiographically or ultrasonically tested as per relevant IS codes and standard practice. The bare wire electrodes for submerged arc welding shall be as follows:

Filler wire : AWS-A-5.17-EH14

Flux shall be agglomerated type of classification

AWS-A-5.17-F7A2EH14

• Galvanizing of steel structure shall be done after all fabrication work is completed. Zinc coating over galvanized surface of structural members and threaded fasteners shall not be less than 610 gm/sqm and 375 gm/sq.m of surface area respectively. However, fasteners may be tapped or re-run after galvanizing. Threads of bolts and nuts shall be capable of developing the full strength of the bolt. The spring washers shall be electro-galvanized as per IS-1573 (Latest Revision). All galvanizing shall be uniform and of standard quality and shall withstand tests in accordance with IS-2633 (Latest Revision). All galvanizing work shall be done at shop.

• All structural steel shall be painted with two primer coats of Zinc silicate 50 microns each and Two finish coats of High built epoxy finish of 90 microns each . All internal steelwork shall have Epoxy Paint two coats of 90 microns over approved primer.

• All welding electrodes shall be of Low Hydrogen type conforming to IS:814 (Latest Revision) and shall be EB5426H3JX type. All electrodes, flux, wire etc. shall be of ADOR Welding Ltd., ESAB India Ltd., D & H Secheron Electrodes Pvt. Ltd. Or any other equivalent manufacturer accepted by Buyer.

Alternatively, flux coated arc welding (FCAW) conforming to AWS- E70T-5 which is a modified procedure of MIG/CO2 (solid wire) can be used.

If submerged arc welding is used, the bare wire electrodes shall be as follows :

Filler wire          :          AWS-A-5.17-EH14

Flux                  :          agglomerated type of classification

AWS-A-5.17-F7A2EH14

1. Minimum preheat & inter pass temperatures for welding over 40mm to 63mm (thickness of the thicker part at the point of welding) shall be 66°C and for over 63mm, it shall be 110°C. However, higher preheat & inter pass temperatures may be required due to joint restraint etc. and shall be followed as per approved welding procedure.

• Minimum tests to be carried out during fabrication and erection of structural steel shall be as follows :

Steel

Ultrasonic Test : Plates above 25mm thick shall be subjected to ultrasonic test as per ASTM-A435 or equivalent to check the presence of lamination.

Fillet weld

Dye Penetration Test : 5% of the total length, Dye penetration shall be

carried out to the root run. Butt weld :

Dye Penetration Test : 10% of the total length, Dye penetration shall be carried out to the root run after back gouging

Radiographic Test : Spot radiography shall be carried out on 100% joints in tension zone and 10% joints in compression zone. Minimum 300mm length shall be spot radiographed. When radiograph is not possible ultrasonic test shall be carried out after grinding the surface.

Ultrasonic Test : 10% of all other Butt welds except crane girder and bunker girder shall be subject to spot radiographic test and the entire balance butt weld for ultrasonic test.

• Connections

Connection of vertical bracings with connecting members and diagonal truss members shall be designed for full tensile capacity of the bracings.

Size of fillet weld for flange to web connection for built up column section shall be as follows:

• Full shear capacity for box section.

• 80% of full shear capacity or actual shear (if indicated in Sellers drawings) or 0.5 times of the web thickness which ever is more for I section. Weld will be double fillet.

• All welds will be continuous. The minimum size of fillet weld shall be as per relevant IS code.

Shear connections shall be designed for 75% of section strength for rolled sections and 80% of section strength for built up section or rolled section with cover plates. Design shear force should be more than actual shear.

Moment connections between beam and column shall be designed for 100% of moment capacity of the beam section.

All butt welds shall be full penetration butt welds.

Connection of base plate & gusset members with the columns shall be done considering that total load gets transferred through weld.

All splicing work shall be of full strength. Shop splicing for all sections other than rolled sections shall be carried out by full penetration butt welds. Shop splicing of all rolled sections shall be carried out using web and flange cover plate.

Following connections shall be provided during erection:

Welded Connection

Connection of secondary beam to main beam Connection of bracing to column

Connection of bracing to longitudinal tie beam Connection of longitudinal tie beam to column Connection of spandrel beam to column Connection of other secondary structures

HSFG Connection (Grade 8.8 bolts)

Splicing of column/transverse frame beam/ longitudinal tie beam Connection of frame beam to column

Other major connections

Bearing Type Connection (HT bolts Grade 8.8) All removable type connections

M.S. bolts (Grade 4.6)

Purlins, stairs, wall beams etc.

2.00.00                             LOADS

Loads as defined under Clause 3.00.00 of Section-II shall be applicable.

3.00.00            LOAD COMBINATIONS

While designing    consideration   shall   be   given    to   the   following                 load combinations:

ii)      DL + LL

1. DL + LL + Equip +_ TL

1. DL + LL + Equip + Cb + CtLA_+  CS +_ TL

1. DL + LL + Equip + Cb + CtLB_+  CS +_ TL

• 0.9DL  _+  EL (for DL only) +_ TL

• 0.9DL  +_  WL1 +_ TL

• 0.9DL  +_  WL2 +_ TL

• DL + *LL + Equip + Cb + Ct  +_  EL +_ TL

(* Appropriate portion of LL which is considered for working out EL shall only be taken)

1. DL + LL + Equip + Cb +Ct +_  (WL1) +_ TL

• DL + LL + Equip + Cb +Ct  +_  (WL2) +_ TL

Where the above loads are :

Limit state method to be followed for design of steel structures as per latest version of IS 800. Applicable load factors to be used for Design of Steel Structures by Limit State Method of strength & serviceability as per IS 800 (Latest).

Appropriate impact factor shall be considered as per IS:875 (Part 2) (Latest Revision) while calculating crane loads.

In calculating wind loads, appropriate internal thrust / suction shall be considered along with external pressures as per IS:875 (Part 3) (Latest Revision). All possible load conditions considering external and internal pressures shall be considered in analysis and design for each combination number (vi),(vii), (ix) & (x)) above to assess worst effect on whole structure as well as its components.

4.00.00                      PIPE / CABLE RACK STRUCTURES

The pipe / cable rack structures shall accommodate the pipes/cables with proper access and adequate working space for erection and maintenance. These shall be designed to carry safely all the loads acting on them (DL, LL, WL, EQL, forces from pipe lines etc.). The structures shall be adequately rigid to carry the forces from the pipelines at anchor points without undue deflection so that the pipelines are really anchored at the anchor points.

It is envisaged that pipe/cable rack under this Package shall have to accommodate some additional pipes and cables, which are not in the scope of

the Bidder. The Bidder shall keep reasonable margin for accommodating such additional pipes/cables in the rack structure, details of which shall be furnished to him during the detailed engineering stage.

5.00.00                                        OTHER SPECIFIC REQUIREMENTS

All steel framed structures shall be either “rigid frame“ or “simple space frames“ or a combination of two.

Lateral forces shall be resisted by stiff jointed moment connections in rigid frame design. The column bases shall generally be fixed to concrete foundation pedestal by providing moment resistant base detail.

Simple space frame design utilizes single-span beam systems, vertical diagonal bracing at main column lines and horizontal bracing at the roof and major floor levels. The most of plant steel buildings shall be designed as simple space frame structures.

Concrete floors shall be considered to provide continuous lateral support to the top (compression) flange of the support beams. However wherever large cut outs (area more than 1.0 sq.m) are provided in the floor slabs horizontal floor bracing shall be provided. Grating/chequered plate floor shall neither be considered to provide lateral support to the top flange of supporting beams nor to provide a shear diaphragm. Adequate lateral support in the form of shear connector and horizontal bracing shall be provided as required.

Floors for vibrating machines of all kind together with supporting framework shall be adequately braced in both horizontal and vertical planes. Floors or structure supporting mechanical equipment shall be designed to minimize vibration, avoid resonance and maintain alignment and level.

Chequered plates shall conform to IS: 3502 (Latest Revision).

All indoor gratings shall be electro-forged type and outdoor gratings shall be welded type. Minimum thickness of grating shall be 40mm for indoor installation and outdoor installation. The opening size shall not be more than 30mm x 100mm. All gratings shall be hot dip galvanized @ 610 gm/sq.m.

Where a steel beam or member is to be connected on RCC structure, it shall be connected using an insert plate and preferably through shear connection.

For crane girders, welding between web and flange plates shall be carried out by submerged arc welding process. Full penetration of weld between web plate and top flange shall be ensured. Intermediate stiffeners shall be connected with top flange plate by full penetration butt weld. Welding across tension flange shall not be permitted. Bearing edges of crane girders shall be machined.

The working point of the bracing connection shall be the center of column and girder to which it connects, where practical. The connections of gusset

plates to column and girders shall be made to include provisions for eccentricity in connection. The double angle back-to-back with gusset plate in between shall not be used in dust-laden areas. Where double angles are not adequate, beam sections with web in the plane of bracing are used.

Permissible Deflections

The permissible deflections of various steel members under normal loading conditions shall be as specified below. For calculation of deflections in structures and individual members dynamic effects shall not be considered, unless specified otherwise. Also, no increase in deflection limits shall be allowed when wind or seismic load are acting concurrent with normal loading conditions.

Vertical Deflection

1. For beams supporting dynamic equipment     : Span / 500

• For beams supporting floors / masonry           : Span / 325

• For beams supporting pipes (pipe racks)        : Span / 400

• For roofing and cladding components             : Span / 250

• For gratings and chequered plates                 : Span / 200 subject to

a maximum of 6 mm

For crane gantries or any member subjected to working loads, the maximum deflection under dead load and live load excluding impact shall not exceed the following values:

1. For manually operated cranes & monorails :      Span / 500

• For electrically operated cranes                      :     Span / 750

Horizontal deflections

The permissible horizontal deflections shall be as per following unless specified otherwise:

1. Single storey building                        :                Height / 300

• Multistoried building                           :                Height / 500

• Pipe/cable rack columns                    :                Height / 200

• Open Structures                                :                Height / 200

Provisions of IS: 800 (Latest Revision) and relevant IS Code shall be followed for limiting deflections of structural elements not listed above.

Minimum Thickness of steel elements

The minimum thickness of various components of a structure and hot rolled sections shall be as follows. The minimum thickness of rolled shapes shall mean flange thickness regardless of web thickness. Structural steel members exposed to significantly corrosive environment (exposed to open air i.e to rain, contact with soil, Ash, contact with drained liquid or contaminated water, alkali/acid etc.) shall be increased suitably in thickness or suitably protected otherwise as per good practice and sound engineering judgment in each instance.

1. Trusses, purlins, girts and bracing                     :        8 mm

• Columns and beams                                          :        8 mm

• Gussets                                                              :        8 mm

• Stiffeners                                                            :        8 mm

• Base plates                                                        :        12 mm & above

• Chequered plates                                               :        6 mm o/p & above

• Grating flats                                                        :        6 mm

• Minimum thickness of structural members other than gratings and chequered plate directly exposed to weather and inaccessible for painting and maintenance shall be 8 mm.

Minimum Sizes of steel elements

The flange width of purlins supporting light weight concrete slab shall not be less than 65 mm and for those supporting roof sheeting and wall cladding it shall not be less than 50 mm. Width of steel rolled section connected to other member shall be at least 50 mm. The depth of beams for platform of all structures shall not be less than 125 mm.

Slenderness and Depth Ratio

The slenderness ratio of main members in tension, compression or bending shall be in accordance with IS: 800 (Latest Revision).

The following limiting ratios of depth to span shall be considered as a general guide.

1. Truss                                                                            1 / 10

• Rolled beams and girders for                                  1 / 24 Ordinary floors and rafters

• Supporting floor beams for vibrating                    1 / 15 Machinery / equipment

• Roof purlins and girts                                                   1 / 45

• Gable columns                                                            1 / 30