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    Theory of Structure: (Portal Frames)

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    Prashant Pal
    Portal frames are low-rise structures used for industrial, commercial, and agricultural buildings. They consist of columns connected by horizontal or pitched beams. Portal frames are efficient at enclosing large spaces. They can be used for minor structures with spans of 15-20 meters and pitched roofs, or larger structures like warehouses over 50 meters wide with features like internal floors or crane supports. The document discusses various types of portal frame designs and their applications.

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    Theory of Structure: (Portal Frames)

    Uploaded by

    Prashant Pal
    731 views10 pages
    Portal frames are low-rise structures used for industrial, commercial, and agricultural buildings. They consist of columns connected by horizontal or pitched beams. Portal frames are efficient at enclosing large spaces. They can be used for minor structures with spans of 15-20 meters and pitched roofs, or larger structures like warehouses over 50 meters wide with features like internal floors or crane supports. The document discusses various types of portal frame designs and their applications.

    Original Title

    PORTAL FRAMES

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    Portal frames are low-rise structures used for industrial, commercial, and agricultural buildings. They consist of columns connected by horizontal or pitched beams. Portal frames are efficient at enclosing large spaces. They can be used for minor structures with spans of 15-20 meters and pitched roofs, or larger structures like warehouses over 50 meters wide with features like internal floors or crane supports. The document discusses various types of portal frame designs and their applications.

    Copyright:

    © All Rights Reserved
    Download as DOCX, PDF, TXT or read online from Scribd
    Download as docx, pdf, or txt
    731 views10 pages

    Theory of Structure: (Portal Frames)

    Uploaded by

    Prashant Pal
    Portal frames are low-rise structures used for industrial, commercial, and agricultural buildings. They consist of columns connected by horizontal or pitched beams. Portal frames are efficient at enclosing large spaces. They can be used for minor structures with spans of 15-20 meters and pitched roofs, or larger structures like warehouses over 50 meters wide with features like internal floors or crane supports. The document discusses various types of portal frame designs and their applications.

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    © All Rights Reserved
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    of 10

    THEORY OF STRUCTURE

    (PORTAL FRAMES)

    PRASHANT.H.PAL
    SEM 9 TH
    COLLEGE: I.I.A

    PORTAL FRAMES
    PORTAL FRAMES ARE GENERALLY LOW-RISE STRUCTURES, COMPRISING COLUMNS AND
    HORIZONTAL OR PITCHED RAFTERS, CONNECTED BY MOMENT-RESISTING CONNECTIONS. .
    THEY ARE VERY EFFICIENT FOR ENCLOSING LARGE VOLUMES; THEREFORE THEY ARE
    OFTEN USED FOR INDUSTRIAL, STORAGE, RETAIL AND COMMERCIAL APPLICATIONS AS
    WELL AS FOR AGRICULTURAL PURPOSES. 

    DIFFERENCE BETWEEN PORTAL FRAMES AND TRUSS

    THE MAIN DIFFERENCE IS THAT A PORTAL FRAME CONSISTS OF BEAMS AND COLUMNS.
    HOWEVER, TRUSS INCLUDES ONLY BAR ELEMENTS.

    AND MOSTLY TRUSSES ARE USED FOR COVERING PURPOSE.

    A TRUSS IS A STRUCTURE COMPOSED OF ROD MEMBERS ARRANGED TO FORM ONE OR


    MORE TRIANGLES. THE JOINTS ARE PINNED (DO NOT TRANSMIT MOMENTS) SO THAT THE
    MEMBERS MUST BE TRIANGULATED. A FRAME, ON THE OTHER HAND, IS A STRUCTURE
    THAT CONSISTS OF ARBITRARILY ORIENTED BEAM MEMBERS WHICH ARE CONNECTED
    RIGIDLY OR BY PINS AT JOINTS. THE MEMBERS SUPPORT BENDING AS WELL AS AXIAL
    LOADS.

    PORTAL FRAMES STRUCTURE CONSISTS OF:

     BEAM
     TRUSS
     COMBINATION OF BOTH (BEAM + TRUSS)

    FOUNDATION:

     ISOLATED FOUNDATION.
     DEPTH OF THE FOUNDTION RANGES FROM ( 0.8M – 1.8M)
     GRILLAGE FOUNDATION:
     1.8M+ DEPTH
     DOWELL BARS

    STRENGTH INTENSITY INCREASE

     LACING
     BATTEN
     LACING BARS OR BATTERN PLATES ARE NOT DESIGN AS LOAD CARRYING
    MEMBERS.
     THEY CARRY TRANSVERSE SHEAR FORCE WHICH OCCURS WHEN THE COLUMN
    DEFECTS.
     THICKNESS OF LACING (1.54CM-2.54CM).

    THERE ARE TWO TYPES OF LACING SYSTEM.

    1. SINGLE LACING SYSTEM

    2. DOUBLE LACING SYSTEM

     THE LACING SYSTEM SHOULD NOT BE VARIED THROUGHOUT THE LENGTH OF THE
    STRUT AS FAR AS PRACTICABLE.

     THE SINGLE-LACED SYSTEMS ON OPPOSITE SIDES OF THE MAIN COMPONENTS


    SHOULD PREFERABLY BE IN THE SAME DIRECTION SO THAT ONE SYSTEM IS THE
    SHADOW OF THE OTHER.

     LOW LOAD BEARING CAPACITY AS COMPARED TO DOUBLE LACED SYSTEM.

    DOUBLE LACING SYSTEM

     CROSS (EXCEPT TIE PLATES) SHOULD NOT BE PROVIDED ALONG THE LENGTH OF
    THE COLUMN WITH LACING SYSTEM, UNLESS ALL FORCES RESULTING FROM
    DEFORMATION OF COLUMN MEMBERS ARE CALCULATED AND PROVIDED FOR IN
    THE LACING AND ITS FASTENING.
     USED FOR LONG SPAN HEAVY LOAD.
    BATTENED COLUMNS:

     COMPRESSION MEMBER CAN ALSO BE BUILT UP INTERMEDIATE HORIZONTAL


    CONNECTING PLATES OR ANGLE CONNECTING TWO OR FOUR ELEMENTS OF
    COLUMN .THESE HORIZONTAL CONNECTING PLATES ARE CALLED BATTENS.
     THE BATTENS SHOULD BE PLACED OPPOSITE TO EACH END OF THE MEMBER AND
    AT POINTS WHERE THE MEMBER IS STAYED IN ITS LENGTH AND AS FAR AS
    PRACTICABLE, BE SPACED AND PROPORTIONED UNIFORMLY THROUGHOUT. 
     THE NUMBER OF BATTENS SHALL BE SUCH THAT THE MEMBER IS DIVIDED INTO
    NOT LESS THAN THREE BAYS WITHIN ITS ACTUAL LENGTH.
     THE EFFECTIVE SLENDERNESS RATIO (KL/R) C OF BATTENED COLUMNS, SHALL BE
    TAKEN AS 1.1 TIME (KL/R)O, THE MAXIMUM ACTUAL SLENDERNESS RATIO OF THE
    COLUMN, TO ACCOUNT FOR SHEAR DEFORMATION EFFECTS.
     IT IS USED FOR MINOR STRUCTURE.

    TYPES OF PORTAL FRAMES FOR MINOR STRUCTURES:

    • MONO-PITCH PORTAL FRAMES


    • PROPPED PORTAL FRAME
    • MANSARD PORTAL FRAME
    • CURVED RAFTER PORTAL FRAME
    • CELLULAR BEAM PORTAL FRAME

    MONO-PITCH PORTAL FRAMES:

    • A MONO PITCH PORTAL FRAME IS USUALLY CHOSEN FOR SMALL SPANS.


    • IT IS A SIMPLE VARIATION OF THE PITCHED ROOF PORTAL FRAME, AND TENDS TO
    BE USED FOR SMALLER BUILDINGS.
    • IT’S SPAN RANGES FROM 15 M TO 20 M.
    PROPPED PORTAL FRAME:

    • A PROPPED PORTAL FRAME CAN BE USED TO REDUCE THE RAFTER SIZE AND ALSO
    THE HORIZONTAL SHEAR AT THE FOUNDATIONS.
    • WHERE THE SPAN OF A PORTAL FRAME IS LARGE AND THERE IS NO REQUIREMENT
    TO PROVIDE A CLEAR SPAN.

    MANSARD PORTAL FRAME:

    • A MANSARD PORTAL FRAME MAY BE USED WHERE A LARGE CLEAR HEIGHT AT


    MID-SPAN IS REQUIRED.

    • BUT THE EAVES HEIGHT OF THE BUILDING HAS TO BE MINIMISED.

    • SPAN RANGES FROM 20M TO 30M.

    CURVED RAFTER PORTAL FRAME:


    • PORTAL FRAMES MAY BE CONSTRUCTED USING CURVED RAFTERS, MAINLY FOR
    ARCHITECTURAL REASONS.
    • BECAUSE OF TRANSPORT LIMITATIONS RAFTERS LONGER THAN 20 M MAY REQUIRE
    SPLICES, WHICH SHOULD BE CAREFULLY DETAILED FOR ARCHITECTURAL
    REASONS.
    • MOSTLY USED IN WAREHOUSES FOR DRAININGOUT OF WATER.

    CELLULAR BEAM PORTAL FRAME:

    • CELLULAR BEAM IS USED.


    • SPAN 50M+
    • RAFTERS MAY BE FABRICATED FROM CELLULAR BEAMS FOR AESTHETIC REASONS
    OR WHEN PROVIDING LONG SPANS.
    • WHERE TRANSPORT LIMITATIONS IMPOSE REQUIREMENT FOR SPLICES, THEY
    SHOULD BE CAREFULLY DETAILED, TO PRESERVE THE ARCHITECTURAL FEATURES.
    TYPES OF PORTAL FRAMES FOR MEDIUM STRUCTURES:

    • PITCHED ROOF SYMMETRIC PORTAL FRAME

    • PORTAL FRAME WITH INTERNAL MEZZANINE FLOOR

    PITCHED ROOF SYMMETRIC PORTAL FRAME:

    • GENERALLY FABRICATED FROM UB SECTIONS WITH A SUBSTANTIAL EAVES


    HAUNCH SECTION.

    • WHICH MAY BE CUT FROM A ROLLED SECTION OR FABRICATED FROM PLATE.

    • 25 TO 35 M ARE THE MOST EFFICIENT SPANS.

    PORTAL FRAME WITH INTERNAL MEZZANINE FLOOR:

    • THE ASSESSMENT OF FRAME STABILITY MUST INCLUDE THE EFFECT OF THE


    MEZZANINE

    • SPAN 40M

    • MOSTLY USED IN STUDIO AND SHOWROOM PURPOSE.


    TYPES OF PORTAL FRAMES FOR HEAVY STRUCTURES:

    • CRANE PORTAL FRAMES WITH COLUMN BRACKET

    • TIED PORTAL FRAMES

    CRANE PORTAL FRAMES WITH COLUMN BRACKET:

    • WHERE A TRAVELLING CRANE OF RELATIVELY LOW CAPACITY (UP TO SAY 20


    TONES) IS REQUIRED.

    • BRACKETS CAN BE FIXED TO THE COLUMNS TO SUPPORT THE CRANE RAILS.

    •  USE OF A TIE MEMBER OR RIGID COLUMN BASES MAY BE NECESSARY TO REDUCE


    THE EAVES DEFLECTION.

    • THE SPREAD OF THE FRAME AT CRANE RAIL LEVEL MAY BE OF CRITICAL


    IMPORTANCE TO THE FUNCTIONING OF THE CRANE.

    • REQUIREMENTS SHOULD BE AGREED WITH THE CLIENT AND WITH THE CRANE
    MANUFACTURER.

    TIED PORTAL FRAMES:


    • IN A TIED PORTAL FRAME THE HORIZONTAL MOVEMENT OF THE EAVES AND THE
    BENDING MOMENTS IN THE COLUMNS AND RAFTERS ARE REDUCED.

    •  A TIE MAY BE USEFUL TO LIMIT SPREAD IN A CRANE-SUPPORTING STRUCTURE.

    • THE HIGH AXIAL FORCES INTRODUCED IN THE FRAME WHEN A TIE IS USED
    NECESSITATE THE USE OF SECOND-ORDER SOFTWARE WHEN ANALYZING THIS
    FORM OF FRAME.

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