SECTION - 1 DESIGN OF BUILDING STRUCTURES

SECTION - 2 DESIGN OF CONVEYOR GALLERIES AND JUNCTION HOUSES

SECTION - 3 PIPLINE SUPPORTING STRUCTURE

SECTION - 4 STEEL CHIMNEY

SECTION - 5 STANDARISATION AND UNIFORMITY

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1.0 General

This specification shall apply to steel work in building and general structural steel work. For technological structures, additional stipulations shall be considered.

2.0 Design considerations

2.01.01 Structures shall be designed such that they are economical and safe and meet the functional and service requirement of the technological process for which they are designed. The architectural planning of the building shall be based on the guidelines and requirements given in this specification.

2.01.02 The structures shall be designed conforming to the relevant safety regulations, Factory Acts, Electricity Rules and stipulations of Statutory bodies as applicable to the project.

2.01.03 Natural ventilation shall be provided ensuring that it prevents rain water entry into the building.

2.01.04 Mild steel gutters and downpipes with gutter outlets and grating shall be provided to carry rain water from roofs of buildings to the drainage system for such building at ground level. In case access is provided to roof, gutters shall be designed walkable with 600 mm sole width.

2.01.05 Adequate facilities in the form of monorails, hoists, platforms etc. shall be provided to facilitate repair and maintenance of overhead cranes, equipment, etc. Access to these platforms shall be provided by stairs from the nearest accessible floor or platform.

2.01.06 Transverse runway beams for crane maintenance hoist of suitable capacity shall be provided near the gables. Where the number of cranes exceed two, similar beams shall also be located at intermediate places. The location of hoists shall be chosen so as not to hamper the operation in the shop.

2.01.07 Access to all floors, gangways and landings shall be by staircases. Access to roof and landing of secondary importance or where such access is used only rarely, shall be by vertical ladders with safety hoops. Stair together with operating platforms shall be provided for access to maintenance hoists.

2.01.08 Access to roof shall be generally located at gables and if required, also at appropriate intermediate locations, so that for every 150 meters length of the building, at least one access to roof is available.

2.01.09 Platforms for accesss to crane cabin shall be provided and shall preferably located in the crane maintenance bays.

2.01.10 Edges of floors, gangways, stairs and landings shall be provided with safety hand railings.

2.01.11 Roof with access shall be provided with safety handrails along the periphery of the roof.

2.01.12 At gable ends of buildings, platforms shall be provided connecting the walkways at crane gantry level.

2.01.13 Floors, gangways and landings shall be covered as follows :

a) Gangways and landings shall have chequered plate with a minimum thickness of 6mm o/p suitably stiffened to meet design load requirements.

b) Repair and operating platforms other than the above shall have chequered plate flooring or hot dip galvanised open gratings.

c)Where there is a possibility of gas or dust collection, hot dip galvanised open gratings shall be used.

2.01.14 Protective metal heat shields shall be provided for steel structures exposed to continuous heat radiation of temperature exceeding 150 °C and also where hot metal splashing on structures is likely to occur.

2.01.15 All buildings and their foundations shall be designed so that it shall be possible to extend them in the longitudinal direction at a later date without further strengthening of gable structures. Provision for transverse extension shall be made where extension is foreseen at the initial stage.

2.01.16 Sheeting on sides and gables shall generally terminate 3.5 m above floor level, sides below this level shall be generally screened by brick walls allowing sufficient air inlet to achieve natural ventilation, unless otherwise required from technological / ventilation requirements.

2.01.17 Connection by permanent bolts to structural elements subject to vibration shall be provided with lock nuts.

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a) Design of steel structures shall be done in accordance with IS:800-1984.

b)Structures subjected to fluctuating/reversal of stress (eg. Crane girders) shall be designed in accordance with IS:1024-1979.

c)Resonance in structures - Structures supporting vibratory/receprocating equipments shall be designed so as to obviate occurance of resonance. The ratio of applied frequency to natural frequency shall be beyond the limits of 0.7 to 1.5 (preferably less than 0.7).

Loads considered in design shall allow fully for all aspects of :

i) Dead weight of structures, wall, floors, equipments, wiring, machinery, pipework, cabling and any item of a permanent nature.

ii)Superimposed loads for roofs and floors plus any temporary machinary not allowed within the general superimposed loads.

iii) Crane loading.

iv) Temperature loads from process requirements because of the position of the structure relative to the heat source or from support of mains, pipes etc. subject to heat.

v) Maximum range of temperature variation for climatic conditions = ± 45°C

vi)Dust load.

vii) Dynamic loads from screens and other such reciprocating machinary.

viii) Maintenance hoists on Runway beams.

ix)Wind Loads

x) Seismic loads

xi) From future extensions.

xii) Any special erection requirements.

a) All live loads shall be considered in accordance with IS:875(Part-2)-1987. (Also refer clause 4.04)

b)Wind loads shall be in accordance with IS:875(Part-3)-1987 and any other consideration specific to the site.

c)Seismic loads shall be in accordance with IS:1893-1984.

d)Crane loading to be considered in design shall be as follows :

I. As per relevant clause of IS:800-1984.

II. IS:875(Part-2)-1987 for conditions not covered in IS:800-1984. unless more severe loads have to be considered for technological/operational conditions.

e)Crane stopper shall be designed in accordance with clause 6.1.4 of IS:875 (Part-5)-1987.

f)In absence of any suitable provision for design loads, any other recognised code of practice may be followed subject to prior approval of the purchaser.

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Besides technological loads, all platforms, walkways, stairs etc. shall be designed for the following live loads :

i) Walkways and Platforms : 2 KN/m²

ii)Visitor's galleries : 4 KN/m²

iii)Maintenance platforms : 4 KN/m²

including crane level

walkway.

iv)Staircase and treads : 4 KN/m²

v)Monorail walkways : 4 KN/m²

vi)Handrails : 0.75 KN/m run

(Horizontal)

vii) Ladder : 0.9 KN

at middle of

rung

viii)Dust loads ( for buildings : 0.5 KN/m² and structures located in

dusty zone)

ix) All structures supporting : Overloadingvibrating equipment by 25 % on(motors,fans etc.) unlessStatic load

specified otherwiseof Equipme-

nts.

Various design loads considered shall be combined in accordance with clause 8.0 of IS:875(Part-5)-1987 to give the most severe loading condition for design of structures.

Permissible limits of stress may be increased wherever permissible, in accordance with IS:800-1984.

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a) The deflection shall be limited in various elements of structures in accordance with IS:800-1984 (clause 3.13).

b) In addition, the following limitations in deflection shall be observed in design :

i) Monorail track beams : Span/400

ii)Main roof trusses, roof girders : Span/400

main floor beams in operating

platforms

i)Crane girders due to surge force: Span/2000

(from one crane only).

ii)Main columns at crane rail level: H/2500

in transverse direction due to

action of crane surge (for surge force consider one crane for single bay and one crane on adjacent aisles for multi-bay buildings)

iii)Open gantry for condition as in: H/4000 (ii) above.

Where H = Height of Column from bottom of base plate to crane rail level.

c) All deflections shall be calculated without dynamic factor.

Wherever excessive deformation is likely to cause operational problem or is aesthetically not agreeable, camber shall be provided to neutralise the effect of deformation due to dead load plus 50 % of imposed loads.

a) Longitudinal and transverse expansion joints shall be provided in buildings and structures in accordance with IS:800-1984 (clause 3.14).

b)Expansion joints shall be formed by providing double rows of columns, with interconnecting gantry girders, secondary roof and wall framing being detailed to allow the maximum calculated movement for the specified temperature variation.

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a) The minimum thickness of structural steel elements shall be in accordance with IS:800-1984 (clause 3.8).

b)The diameter of structural bolts shall not be less than 16 mm except for those securing roof and wall sheets, windows, doors and stiching of thin coverings. For bolted joints, at least two bolts per joint shall be provided.

c)The size of fillet welds shall not be less than 5 mm.

d) Main structural elements shall be welded continuously. Intermittent welding shall be used only on secondary members which are not exposed to weather or other corrosive influence.

e)Field connection and splices shall be made as follows :

i) by welding

ii)by permanent bolts (for secondary members such as purlins, wall runners etc.)

iii)by High Strength Friction Grip bolts (HSFG)

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5.01.01 The dimensional parameters for conveyor galleries shall conform to the provision of IPSS:2-03-001-81 (Interplant Standards : Steel Industry - Design parameters for galleries and tunnels for belt conveyors in steel plant). The structure shall be designed so as to meet functional requirements and shall provide space for operation, mainteanance and removal of machinary and give the workers good and safe environment.

5.01.02 Gallery floors shall be of precast R.C.C slabs / Chequered plates ( as required ) supported on steel beams.

5.01.03 Steps shall be provided (rise not exceeding 130 mm) along the walkways if the gallery slope exceeds 12°. In case the slope of gallery is between 6° to 12°, suitable ribs shall be provided on floor (without any sharp edges) at 250 to 300 mm intervals.

5.01.04 Provisions shall be made for emergency exit from galleries to gorund level and also for cross-over above conveyor at 150 m intervals (maximum). The width of cross over shall not be less than 600 mm.

5.01.05 Roof and side walls of conveyor galleries shall be covered with GCS/Aluminium sheets. with a provision of gap of 300 mm below roof and 150 mm from top of floor level on the side wall for ventilation.

5.01.06 Adequate provision for natural light inside conveyor gallery shall be made through side walls by providing translucent sheets (FRP sheets). Every sixth sheet on side wall shall be FRP sheet and shall be staggered on opposite wall.

5.01.07 Roof slopes of conveyor galleries shall be 1:5 (1 vertical, 5 Horizontal).

5.01.08 The level of underside of the base plate of gallery supporting trestles shall be 300 mm above the average ground level of the surrounding area.

5.01.09 Protective handrailing shall be provided along gallery walkways, open platform, stairways, landings, edges of walkways when the gallery is not enclosed, and around erection openings, if any, to ensure safety of operating personnel.

5.01.10 Conveyor galleries longer than 150 m shall be provided with expansion joints with twin trestles/supports. Each expansion block shall have fixed support/rigid trestle with adequate arrangement (provision of top chord and bottom chord bracing to gallery girder etc.) for transfering the transverse and longitudinal forces to the foundation.

5.01.11 Gallery girders near junction house shall be preferably supported on trestle located as close to the junction house as possible, with part of gallery girder between junction house and trestle cantilevered from the trestle. Supporting gallery girders on junction house shall be generally avoided.

5.01.12 The underside of the belt conveyor shall be fully covered with 3 mm sheet in case of conveyor is located within the boundaries of the plant. Wherever such covering is not provided (as in case of the mines area or cross country), the covering must be provided wherever the gallery crosses roads, railway lines or areas of public gatherings.

5.01.13 Conveyor gallery over hot metal track :

When underside of gallery is at less than 12m height from track level, heat shield shall be provided below gallery as well as on sides for a width of track 8 m ( i.e 4 m on either side of center line of the track).

5.01.14 When conveyor gallery crosses above or below H.T cables, a clear distance of 1.0 m between the structural elements/cladding and HT cables shall be maintained.

5.01.15 When the conveyor bridge passes over plant roads, clearence between the road surface and the lowest points of the bridges shall not be less than 4.5 m or the height needed for the passage of the largest individual components of the plant equipment, whichever is the larger.

5.01.16 The junction house shall be designed to suit the technological requirements. Number of floors, height of building etc. shall be decided accordingly.

5.01.17 In general the junction house shall be designed as framed structures on shorter span side and vertically braced on longer side to achieve stability.

5.01.18 Floor of junction houses shall be of RCC slab supported on steel beams, unless required otherwise from technological consideration.

5.01.19 Roof and side covering of junction houses shall be with GCS/Aluminium sheets as specified. Roof slope shall be 1 : 5 ( 1 Vertical : 5 Horizontal).

5.01.20 Suitable access staircase and safety handrailing shall be provided to all floors of junction houses.

5.01.21 When hydrowashing of floor of junction house is envisaged , the floor beam supporting RCC slab shall be laid to a suitable slope to achieve the same, wherever the same is not practicable to achieve through screed concrete. (Minimum slope of floor shall be 1.5%).

5.01.22 Wall sheeting shall generally start from the lowest working floor and extend upto roof level with louvres at each floor level to ensure adequate natural ventilation.

5.01.23 Monorails for maintenance hoists shall be provided for maintenance and repair of various equipments located on the floors.

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8.01 Bridges shall be provided to support pipelines of smaller diameters for which maximum permissible span is less than the distance between supporting trestles.

8.02 Trestles which are designed to transmit longitudinal loads (along the length of pipeline) to the foundation, shall be four legged construction. Other trstles which transmit only the vertical load to the foundation shall be two-legged construction.

8.03 Access stair and platforms shall be provided for maintenance of equipment installed in the pipeline (eg. valves etc.). Maintenance walkways with handrailing shall also be provided along the pipeline, wherever required. Provision of access stairs, walkways platforms, handrailing etc. shall conform to clause 3.11 of this specification.

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This specification shall apply to design of self supporting steel chimneys.

a) Lining shall be provided in chimney shell as per technological requirements. In the case of lined chimneys, checking for stress and resonance due to wind shall be done for both the conditions i.e lined and unlined.

b) Annular platforms with minimum clear width of 1200mm shall be provided at locations of environment monitoring equipments, in addition to the stipulations of IS:6533 (Part-2)-1989. Landing/resting platforms to ladders shall be provided at intervals not exceeding 10.00 M where annular platforms are provided at intervals of height greater than 10.00 M.

c) Approach to platforms shall be with ladders with safety cages. (Refer Cluase 3.11(j) of this specification.

d) Chimneys shall be provided with adequate number of Painter's trolleys for inspection and maintenance unless categorically agreed to otherwise with Purchaserby. In case where Painter's trolley is not provided, suitable alternative facility shall be provided for inspection and maintenance.

e) Chimneys shall be fitted with helical strakes of three rail system, and shall be strong enough to withstand the additional wind load from the strakes.

a) Steel chimneys shall be designed in accordance with IS:6533(Part-2)-1989.

b) Elements like platforms, hand-rails, ladders, anchor bolts etc. shall be designed in accordance with IS:800-1984.

The maximum deflection at the top due to the action of wind, without considering the dynamic factor shall not be greater than h/200, where h is the unsupported height of the chimney.

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Every endeavour shall be made to achieve standarisation and uniformity amongst the steel structures of different units of the plant.

10.1 The following items shall be kept in view in design of structures :

a) Uniform layout module shall be adopted to the extent possible consistent with economy. It is suggested to adopt a basic module of 3 m for building width and 6 m for column spacing along building length.

b)Uniform slopes of roofs matching with existing buildings unless specifically required otherwise for any particular unit.

c)Provision of expansion joints by using twin columns.

d) Uniform adoption of clearence between structures and moving parts of equipments.

e)Provision of adequate natural ventilation by using louvres (canopy like structures) at appropriate location and roof monitors/natural ventilation systems at roof.

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