PORTAL FRAME

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PORTAL FRAMEPORTAL FRAME

Submitted by:-Submitted by:-

JAHNVI GULATIJAHNVI GULATI

B.ARCH (AR)B.ARCH (AR)

44THTH YEAR, 8 YEAR, 8THTH SEM. SEM.

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INTRODUCTIONINTRODUCTION


Portal frames are the most commonly used Portal frames are the most commonly used structural forms for single-storey structural forms for single-storey industrial structures. They are constructed industrial structures. They are constructed mainly using hot-rolled sections, supporting mainly using hot-rolled sections, supporting the roofing and side cladding via cold-formed the roofing and side cladding via cold-formed purlins and sheeting rails. They may also purlins and sheeting rails. They may also be composed of tapered stanchions and rafters be composed of tapered stanchions and rafters fabricated from plate elements. Portal frames of fabricated from plate elements. Portal frames of lattice members made of angles or tubes are lattice members made of angles or tubes are also common, especially in the case of longer also common, especially in the case of longer spans. spans. Generally, the centre-to-centre distance Generally, the centre-to-centre distance between frames is 6 to 7.5m, with eaves height between frames is 6 to 7.5m, with eaves height ranging from 6 -15 m. ranging from 6 -15 m. Normally, larger spacing of frames is used in Normally, larger spacing of frames is used in the case of taller buildings, from the point of the case of taller buildings, from the point of economy.economy.Moment-resisting connections are to be provided Moment-resisting connections are to be provided at the eaves and crown to resist lateral and at the eaves and crown to resist lateral and gravity loadings.gravity loadings.

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The stanchion bases may behave as The stanchion bases may behave as either pinned or fixed, depending upon either pinned or fixed, depending upon rotational restraint provided by the rotational restraint provided by the foundation and the connection detail foundation and the connection detail between the stanchion and foundations.between the stanchion and foundations.

Portal frames can be used in timber Portal frames can be used in timber based commercial and industrial based commercial and industrial building construction with clear spans of building construction with clear spans of 15 to 30 metres.They provide large 15 to 30 metres.They provide large clear spans and good height clearance clear spans and good height clearance for use in a range of applications, for use in a range of applications, including:including:• warehouses and factories, warehouses and factories, •commercial buildings, commercial buildings, •churches, churches, •sporting venues sporting venues •rural sheds, etcrural sheds, etc. .

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Timber portal frames are cost effective, easily Timber portal frames are cost effective, easily accommodate additional lighting, plumbing, etc accommodate additional lighting, plumbing, etc and can be erected quickly. The overall and can be erected quickly. The overall appearance is also aesthetically pleasing. appearance is also aesthetically pleasing. Timber portal frames are particularly suitable for Timber portal frames are particularly suitable for use in high visual impact applications eg use in high visual impact applications eg churches, halls, or potentially corrosive churches, halls, or potentially corrosive environments eg swimming pool enclosures, environments eg swimming pool enclosures, buildings housing chemical manufacturer and buildings housing chemical manufacturer and storage, tanneries, etc. Portal frames may be storage, tanneries, etc. Portal frames may be made from sawn timber, Glulam, LVL and made from sawn timber, Glulam, LVL and plywood webbed beams. The connections carry plywood webbed beams. The connections carry significant moments and must have both significant moments and must have both strength and stiffness to be effective.Timber strength and stiffness to be effective.Timber portal framed buildings may be clad with portal framed buildings may be clad with conventional metal, or fibre cement cladding, as conventional metal, or fibre cement cladding, as is common for warehouses and factories, or is common for warehouses and factories, or with timber products such as plywood or with timber products such as plywood or weatherboards.For other commercial weatherboards.For other commercial applications, cavity brick, brick veneer, concrete applications, cavity brick, brick veneer, concrete tilt-up or concrete block-work may be required tilt-up or concrete block-work may be required for fire isolation or compliance with local building for fire isolation or compliance with local building regulations.regulations.

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Because of these very strong and rigid joints Because of these very strong and rigid joints some of the bending moment in the rafters is some of the bending moment in the rafters is transferred to the columns. This means that the transferred to the columns. This means that the size of the rafters can be reduced or the span size of the rafters can be reduced or the span can be increased for the same size rafters. can be increased for the same size rafters. This makes portal frames a very efficient This makes portal frames a very efficient construction technique to use for wide span construction technique to use for wide span buildings.buildings. Portal frame construction is therefore typically Portal frame construction is therefore typically seen in seen in warehouses, , barns and other places and other places where large, open spaces are required at low where large, open spaces are required at low cost and a pitched roof is acceptable. cladding cost and a pitched roof is acceptable. cladding with cavity masonry work to the bottom 2m of with cavity masonry work to the bottom 2m of the wall to provide security and impact the wall to provide security and impact resistance. The lightweight cladding would be resistance. The lightweight cladding would be carried on sheeting rails spanning between the carried on sheeting rails spanning between the columns of the portal frames.columns of the portal frames.

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http://en.wikipedia.org/wiki/Warehouse

http://en.wikipedia.org/wiki/Barn

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Portal frames are made in a variety of shapes Portal frames are made in a variety of shapes and sizes. There are generally 3 types of portal and sizes. There are generally 3 types of portal frames :-frames :-•Steel portal frameSteel portal frame•Timber portal frameTimber portal frame•Concrete portal frameConcrete portal frame

They are usually made from steel, but can They are usually made from steel, but can also be made from concrete or timber. The also be made from concrete or timber. The portal structure is designed in such a way that it portal structure is designed in such a way that it has no intermediate columns, as a result large has no intermediate columns, as a result large open areas can easily be created within the open areas can easily be created within the structure. structure. Portal Frames are generally used for single Portal Frames are generally used for single storey construction which require a large storey construction which require a large unobstructed floor space.unobstructed floor space.

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TYPES OF PORTAL FRAMETYPES OF PORTAL FRAME

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STEEL PORTAL FRAMESTEEL PORTAL FRAME


The early use of the rigid portal frame coincided The early use of the rigid portal frame coincided with the introduction of a wide range of a cold with the introduction of a wide range of a cold formed, profiled steel sheets for roofing, which formed, profiled steel sheets for roofing, which could be fixed at a low pitch and be weather could be fixed at a low pitch and be weather tight. Long-span portal frames may have a pin-tight. Long-span portal frames may have a pin-joint connection at the ridge to allow some joint connection at the ridge to allow some flexure between the rafters of the frame which flexure between the rafters of the frame which are pin-jointed to foundation bases to allow are pin-jointed to foundation bases to allow flexure of posts due to spread under load.flexure of posts due to spread under load.For economy in the use of a standard section, For economy in the use of a standard section, short and medium-span steel portal frame s are short and medium-span steel portal frame s are oftn fabricated from one mild-steel I-section for oftn fabricated from one mild-steel I-section for both rafters and posts, with the rafters welded to both rafters and posts, with the rafters welded to the posts without any increase in depth at the the posts without any increase in depth at the knee. knee. Short-span portal frames may be fabricated off Short-span portal frames may be fabricated off site as one frame. Medium-spansite as one frame. Medium-span portal frames portal frames are generally fabricated in two halves for ease of are generally fabricated in two halves for ease of transport and are assembled on site with bolted transport and are assembled on site with bolted connections of the rafters at the ridge, with high connections of the rafters at the ridge, with high strength friction gripstrength friction grip..

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STEEL PORTAL FRAMESTEEL PORTAL FRAME


AdvantagesAdvantages•Speed and ease of erectionSpeed and ease of erection•Building can be quickly closed in and made Building can be quickly closed in and made water tight.water tight.•Framework prefabricated in a workshop and not Framework prefabricated in a workshop and not affected by weather.affected by weather.•Site works such as drainage, roads etc can be Site works such as drainage, roads etc can be carried out until framework is ready for erection.carried out until framework is ready for erection.•No weather hold up during erecting the No weather hold up during erecting the framework.framework.•Connected together in factories by welding and Connected together in factories by welding and site connections should be bolted.site connections should be bolted.

DisadvantagesDisadvantages•Although steel is incombustible it has a poor Although steel is incombustible it has a poor resistance to fire as it bends easily when hot. resistance to fire as it bends easily when hot. •Subject to corrosionSubject to corrosion

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PRE-CAST REINFORCED CONCRETE FRAMEPRE-CAST REINFORCED CONCRETE FRAME


For several years following the end of For several years following the end of the second world war(1945) there was a the second world war(1945) there was a considerable shortage of structural steel considerable shortage of structural steel in this country and it was then that the in this country and it was then that the reinforced concrete portal frames came reinforced concrete portal frames came into common use for agricultural, into common use for agricultural, storage, factory, and other single-storage, factory, and other single-storeyed buildings.storeyed buildings. a limited range of standard, pre-cast a limited range of standard, pre-cast reinforced concrete portal frames was reinforced concrete portal frames was supplied for the economic benefit of supplied for the economic benefit of repitetive casting in standard moulds repitetive casting in standard moulds and close control of mixing, placing and and close control of mixing, placing and compaction of concrete that is possible compaction of concrete that is possible in factory conditions.in factory conditions.

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TYPES OF CONCRETE PORTAL FRAMETYPES OF CONCRETE PORTAL FRAME


Symmetrical pitch reinforced Symmetrical pitch reinforced concrete portal frame constructionconcrete portal frame construction

This the most structurally efficient and most This the most structurally efficient and most commonly used type of concrete portal frame.commonly used type of concrete portal frame. it has been used for factories, warehouses, it has been used for factories, warehouses, barns, sheds and single-storey places of barns, sheds and single-storey places of assembly.the slope of the rafters and spacing of assembly.the slope of the rafters and spacing of purlins and sheeting rails is usually arranged to purlins and sheeting rails is usually arranged to suit fibre cement or profiled steel sheeting.suit fibre cement or profiled steel sheeting.

North light pre-cast reinforced North light pre-cast reinforced concrete portal frame constructionconcrete portal frame construction

The most economical span for this profile of The most economical span for this profile of frame is up to about 9.0 to minimise the volume frame is up to about 9.0 to minimise the volume of roof space inside the frames and to avoid the of roof space inside the frames and to avoid the large sections of frame that would be necessary large sections of frame that would be necessary with greater spans. The south-facing slope is with greater spans. The south-facing slope is pitched at 22 degrees and the north-facing slope pitched at 22 degrees and the north-facing slope at 60 degrees to the horizontal.at 60 degrees to the horizontal.

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PRE-CASTREINFORCED CONCRETE FRAMEPRE-CASTREINFORCED CONCRETE FRAME


AdvantagesAdvantages•There was a ready supply of a limited range of There was a ready supply of a limited range of standard frames that could rapidly be standard frames that could rapidly be transported, erected, and finished at an transported, erected, and finished at an economic cost.economic cost.• they require no maintainance during the useful they require no maintainance during the useful life of the building.life of the building.• it has a better resistance to collapse during it has a better resistance to collapse during fires than an unprotected steel frames.fires than an unprotected steel frames.• economy of section area gained by the use of economy of section area gained by the use of the plastic method of design in the design of the plastic method of design in the design of steel frames is considerably less with reinforced steel frames is considerably less with reinforced concrete.concrete.• cover of concrete to the steel reinforcement to cover of concrete to the steel reinforcement to inhibit rust and give protection during fires.inhibit rust and give protection during fires.

DisadvantagesDisadvantages• they have to be formed in standard size they have to be formed in standard size moulds, for the sake of economy, there is only a moulds, for the sake of economy, there is only a limited range of sizes.limited range of sizes.

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TIMBER PORTAL FRAMETIMBER PORTAL FRAME


Combinations of slender timber sections Combinations of slender timber sections glued, or glued or nailed together, are glued, or glued or nailed together, are used in portal frames for medium-and used in portal frames for medium-and long-span roofs for such buildings as long-span roofs for such buildings as churches, assembly halls, sports halls churches, assembly halls, sports halls and other single-storey structures where and other single-storey structures where the timber portal frames are exposed for the timber portal frames are exposed for appearance sake.appearance sake.

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TYPES OF TIMBER PORTAL FRAMETYPES OF TIMBER PORTAL FRAME


Symmetrical-pitch glued laminated Symmetrical-pitch glued laminated timber portaltimber portalThese portal frames are usually fabricated in two These portal frames are usually fabricated in two sections for ease of transport and are bolted sections for ease of transport and are bolted together at the ridges. These comparatively together at the ridges. These comparatively expensive portal frames are spaced fairly widely expensive portal frames are spaced fairly widely apart to support timber or steel purlins which can apart to support timber or steel purlins which can be covered with any of the sheet materials, be covered with any of the sheet materials, slates or tiles.slates or tiles.

Flat glued-and-nailed timber portalFlat glued-and-nailed timber portalThe flat portal frame is designed for the most The flat portal frame is designed for the most economic use of timber glued together with the economic use of timber glued together with the top and bottom booms of glued laminate with top and bottom booms of glued laminate with web stiffners. The portal frames are widely web stiffners. The portal frames are widely spaced to support metal decking on the roof and spaced to support metal decking on the roof and profiled sheeting on the walls.profiled sheeting on the walls.

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TIMBER PORATL FRAMETIMBER PORATL FRAME


AdvantagesAdvantages• Timber has a natural resistance to fungal Timber has a natural resistance to fungal decay.decay.• insect attack can be prevented by impregnating insect attack can be prevented by impregnating timber with insecticide preservative.timber with insecticide preservative.• timber, which is a combustible material, is not timber, which is a combustible material, is not easy to ignite in the sizes usual to buildings.easy to ignite in the sizes usual to buildings.•Once ignited, timber burns very slowly and Once ignited, timber burns very slowly and forms a protective layer of charcoal on its forms a protective layer of charcoal on its surface which insulates the remainder from the surface which insulates the remainder from the worst effects of fire.worst effects of fire.• the surface of soft wood timber can be treated the surface of soft wood timber can be treated with flame retardants to achieve necessary rate with flame retardants to achieve necessary rate of flame spread.of flame spread.

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INTERNAL OUTLINE OF THE PORTAL FRAMEINTERNAL OUTLINE OF THE PORTAL FRAME


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clear unobstructed floor clear unobstructed floor area available.area available.

With single storey buildings With single storey buildings natural lighting is gained by natural lighting is gained by placing clear sheets in roof placing clear sheets in roof layout. layout.

These sheets will run from These sheets will run from eaves to ridge at suitable eaves to ridge at suitable intervals.intervals.

SHEETINGSHEETING


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A high percentage of roofs A high percentage of roofs are covered with composite are covered with composite profile metal sheets with a profile metal sheets with a coloured external skin. coloured external skin. These composite sheets These composite sheets have approximately 50mm have approximately 50mm of insulation sandwiched of insulation sandwiched between two thin metal between two thin metal sheets or aluminium sheets. sheets or aluminium sheets. Coated steel is lowest in Coated steel is lowest in cost but limited in life due to cost but limited in life due to the durability of the finish. the durability of the finish. Aluminium develops its own Aluminium develops its own protective film. Profile protective film. Profile sheets are quick to erect, sheets are quick to erect, dismantle and repair.dismantle and repair.

Wall panelsWall panels

BASE JOINTBASE JOINT


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Legs of portal frame Legs of portal frame connected with the connected with the base of foundation.base of foundation.

RIDGE JOINTRIDGE JOINT


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ridge joint or apex joint.

wedge shaped pieces called gusset pieces to strengthen and increase the bolt area.

KNEE JOINTKNEE JOINT


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knee joint must be strong to knee joint must be strong to support the roof loads andsupport the roof loads and prevent bending.prevent bending.

DIGONAL BRACINGDIGONAL BRACING


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Diagonal Diagonal bracing for bracing for strengtheningstrengthening

EXTERNAL WALL DETAILEXTERNAL WALL DETAIL


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claddingcladding

brickworkbrickwork

PORTAL FRAME

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