SPACE FRAMES
SPACE FRAMESByJ.C.WASON1DIFFERENCE BETWEEN A PLANE FRAME AND A SPACE FRAMEPlane Frames & Space Frames :A PLANE FRAME :
A 2D structure whose all elements lie in the same plane.
Examples :
A Portal FrameAn ordinary Roof Truss
PLANE TRUSS ( All members and All loads lie in the same Plane )
4 PLANE FRAMES : PORTAL FRAMES( All loads and All members in the same Plane )
5PLANE FRAMES :A Plane Frame can resist loads applied only in its own plane.
A Plane Frame is not stable to forces perpendicular to its plane.SPACE FRAMES :A Space Frame is a Three dimensional assembly.
A Dome is a Typical example of a Space Frame.
A Space structure can resist loads applied at any point, at any inclination to surface of structure and in any direction.
SPACE FRAMES : Thus, for a Space Frame: ( i ). Members of the Space Frame are located in Three dimensions in space.
( ii ). Loads may be applied on the structure acting in Any direction in space.
PyPzPxA MULTISTOREYED FRAMED BUILDING IS A SPACE STRUCTURE WITH MEMBERS LOCATED IN SPACE, AND SUBJECTED TO FORCE IN X, Y & Z PLANES
BEAMPzPxA MULTISTOREYED FRAMED BUILDING IS A SPACE STRUCTURE WITH MEMBERS LOCATED IN SPACE, AND SUBJECTED TO FORCES IN X, Y & Z PLANESBEAMPyPyCOLUMNZXYFORCES ACTING IN A TYPICAL FLOOR IN A MULTISTOREYED BLDG.Advantages of Space Frames :A Space Frame can :(i). Gives greater freedom of design.(ii). Span larger col. free areas.(iii). Give pleasing appearance.(iv). May lead to lower cost.
However, Analysis of Space Structures is more complex and generally needs computer analysis. SPACE STRUCTURES :Steel Space FramesRCC Space Frames(i). Single layered Space Structures :(Derive strength due to curvature)Example : Retreading Factory, Jabbalpur.
(ii). Double Layered Space Frames : (Double layered space structures)Example : Hall of 14, Pragati Maidan, New Delhi.Example : Hall of NationsHALL OF NATIONS, PRAGATI MAIDAN, NEW DELHI AN EXAMPLE OF CONCRETE SPACE STRUCTURE
13 HALL OF NATIONS, PRAGATI MAIDAN, NEW DELHI AN EXAMPLE OF CONCRETE SPACE FRAME
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CONCRETE SPACE FRAME FOR HALL OF NATIONS, NEW DELHI (INDIA)(b) HALF ELEVATION HALF SECTION39014.431035.6987654321LVL 04876.84876.84876.8731523448.4LVL .5LVL .4(c) PART PLAN; LEVELS 4 & 5(d) PYRAMID GEOMETRYLC54 44 24
HALL OF NATIONA, PRAGATI MAIDAN, NEW DELHI- TOP PLAN4876.83901473152SPACE STRUCTURES - TYPESSINGLE LAYERED
DOUBLE/MULTILAYEREDSTEEL SPACE FRAMES :Span Range : (i). Single layered = 20 30 m (ii). Double layered = 50 80 m
Uses : (i). Industrial Bldgs. (ii). Exhibition Halls (iii). Sports pavallions (iv). Gymnasiums etc.SINGLE LAYERED SPACE STRUCTURES SALIENT POINTS : (i). Single layer of Triangular network of members.
(ii). Curved, Shaped like shells to obtain space geometry.
(iii). Derive strength through space geometry (curved shape).
(iv). Joints hinged and members subjected to Axial Forces (Axial compression/axial tension).
(v). Similar to shell behavior. SINGLE LAYERED SPACE STRUCTURES Examples :Hall of Technology at Pragati Maidan, New Delhi.
2. Roof of Talkatora Indoor Stadium, New Delhi.
STEEL DOME AN EXAMPLE OF A SINGLE LAYERED SPACE STRUCTURE
STEEL DOME AN EXAMPLE OF A SINGLE LAYERED SPACE STRUCTUREADD YOUR TEXT
ELEVATION PLAN TRUSSED TRIANGULATED SINGLE LAYERED ROOF
ADD YOUR TEXT ELEVATION PLAN SIDE VIEWA TAPEZDOIDAL TRIANGULATED SINGLE LAYERED ROOF PLAN
A TRIANGULATED STEEL DOME ROOF- AN XAMPL OF A SINGLE LAYERED SPACE STRUCTURE ELEVATION
196 m Dia ( 50000 seating Capacity) Steel Dome Roof for Haris County Sports Stadium, Texas, USA DOUBLE LAYERED SPACE STRUCTURES SAILIENT FEATURES :Visualised as a 2D surface layers, (Top + Bottom), connected by verticals and diagonals.
Derive Plate Behavior ( Two way slab actions).
Derive bending strength due to depth of system.
Unlike single layered systems, Double layered systems need not be curved in shape.
Example: HALL NO 14, PRAGATI MAIDAN, NEW DELHIDOUBLE LAYERED SPACE STRUCTURES SAILIENT FEATURES (CONTD.) :5. The surface grids could be Square or Equilateral Triangles.
6. Web members are diagonals or a combination of verticals and diagonals. Advantages of Two layered systems : 1. greater rigidity :
(i). Hence can have larger spans.
(ii). In Double layered grid systems, there is more flexibility in positioning of column supports. Supports may be widely spaced and may be ,if necessary, irregular.
(iii). High rigidity of double layered grids reduces the deflection of the structure. 2. Higher Indeterminancy : Due to high level of indeterminancy, overstressing or buckling of any individual member under any concentrated load may not lead to collapse of the structure.
The load will get distributed to other adjoining members leading to even distribution of stress under concentrated loads in several directions. 3. Space for accomodating Electric and Service conduits :Services/AC ducts may conveniently be accomodated within the double layered grid. 4. Feasibility of using standard modules and mass production : Double layered grids are usually built from simple prefabricated standard units, which can be mass produced in a factory and can be easily and rapidly assembled at site. SKELTEL SPACE STRUCTURE : Most common form of Space structures are the Skeltel Space Structures consisting of a . network of interconnected members. Such structures are appreciated due to their visual beauty and impressive simplicity. Accordingly, there is a trend to leave structural grid members exposed as part of the Architectural expression. Advantages of Skeltel Space Frames : Less self weight ( Light weight system)
( i ) Feasibility of Large Spans. ( ii ). Reduction in Cost. ( iii ). Reduced loading on Supporting Columns and Foundations. ( iv ). Less Earth quake forces.
2. . Visual beauty and ex pressive simplicity.
3 . Structural efficiency.
4. Efficient for loads acting in Any plane.
1. Less self weight ( Light weight system) :Skeltel Space Frames have : light sheeting roofing which normally does not require any terracing for drainage of rain water. Self wt of such systems is about 1 to 2 KN/m2 against self wt of 10 to 12 KN/m2 for tradition RCC roofs with Beam and slab systems. Table : Approx. weights of Space StructuresType of StructureSpan Range(m)Weight Range (Kgs/m2 )1. Conventional Trusses20 - 3020 - 262. Domes60 - 8032 - 453. Double layeredGrids20 - 3015 - 2036 ( i ) Feasility of Large Spans : Space frames of about 80m X 80 m and Steel Domes over 100 m Dia have been planned using the concepts of Skeltel Space Structures. ( ii ). Reduction in Cost :Cost of roofing with such systems is less than cost of traditional RCC systems.( iii ). Reduced loading on Supporting Columns and Foundations : Due to less self weight, loads on the supporting columns and foundations is reduced leading to Economy in design of these structural elements. ( iv ). Less E Q forces :E Q force acting on a structure is a function of mass of the structure. As Mass of such systems is comparatively small, E Q force on such structure is also small.
Due to smaller overall wt. E Q forces normally are NOT critical for their design. Such strctures are more critical for wind loads and not for E Q loads.2. Visual beauty and expressive simplicity: Due its form, such structures are visually beautiful and have bold e x pression, which is generally integrated into Architectural aesthetics and, as such, structural members are normally left e x posed for bold Architectural e x pression.( 3 ). Structural efficiency :Due to its interconnected members in space, any load applied at any point gets distributed to other distant members leading to a leading to reduction of stresses in members directly under the load and a fairly even distribution of the stresses throught the structure. This results in more efficient and economical Structural design.(4). Efficient for loads acting in Any plane :Space structures are efficient to resist loads acting in any plane.STRUCTURAL PROPORTIONING OF DOUBLE LAYERED GRID SPACE SYSTEMS :EMPIRICAL RULES FOR FIXING UP THE DOUBLE LAYERED GRID SPACE STRUCTURES ARE DISCUSSED. DOUBLE LAYERED SPACE STRUCTURES OVERALL STRUCTURAL PROPORTIONING :Typical (Span/Depth) ratios :
(i). Simply supported spans : d/L = 1/18 to 1/25 (ii). Cantilevered spans : d/L = 1/9 where : d = Depth of system L = span Optimum bay dimensions : a = 1.2d to 2.5d
DOUBLE LAYERED SPACE STRUCTURES - OVERALL PROPORTIONG (CONTD.) : Bay dimensions : are restricted to about 3 to 4m due to Buckling of compression members.
Individual members: Hollow circular Tube sections are preferred due to uniform structural strength/Buckling Strength along all axis.DOUBLE LAYERED GRIDS ROOF COVERINGS : Roof claddings suitable for Space grid roofs are : ( i ). AC Sheets
( ii ). Aluminium corrugated sheets
( iii ). Precast ferrocement slabs DOUBLE LAYERED GRIDS- METHOD OF ANALYSIS : Computer based Analysis adopted. Stiffness Matrix method of Analysis is used as basis for most of the computer programmes available for analysis of Space Structures. DOUBLE LAYERED GRID - PLAN OF GRID ELEVATION OF GRID
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DOUBLE LAYERED GRID : PERSPECTIVE VIEW50
SQUARE OVER SQUARE - PLAN OF GRID ELEVATION OF GRIDaa51
(a) TWO-WAY LATTICE GRIDBASIC UNITPLANELEVATION
(c) TWO-WAY SPACE GRID WITH SQUARE PYRAMIDS (SQUARE ON SQUARE OFFSET)aa2/2
(e) TWO-WAY SPACE GRID WITH SQUARE PYRAMIDSTOP GRIDBOTTOM GRIDBRACING
ADD YOUR TEXTADD YOUR TEXT
(b) GRID EDGE PROFILESabcdCORNICEVERTICALMANSARD(a) METHODS OF SUPPORTING THE GRID
METHODS OF SUPPORTING DOUBLE-LAYERED GRIDS
(C) LOCATION OF SUPPORTS(C) METHODS OF SUPPORTING DOUBLE-LAYER GRIDS
(C) LOCATION OF SUPPORTS METHODS OF SUPPORTING DOUBLE-LAYERED GRIDS
LOCATION OF SUPPORTS(C) METHODS OF SUPPORTING DOUBLE-LAYER GRIDS
(C) LOCATION OF SUPPORTS
PLANAR TRUSSES ON LATTICE GRIDA) ONE WAY ACTION :61B) TWO WAY ACTION :
PLANAR TRUSSES ON LATTICE GRID62C) THREE WAY ACTION :
PLANAR TRUSSES ON LATTICE GRID63MULTILAYER SYSTEMS ( Double layer systems )
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KEY PLANM.S. COLUMN CAPITAL
M.S. COLUMN 300 400050011000INCLINED MEMBER 50 M.S. PIPEBOTTOM CHORD50 M.S. PIPETOP CHORD50 M.S. PIPE500500500500500500
PART PLAN AT A50 M.S. BOTTOM CHORD4 MM THICKM.S. CONNECTINGPLATE500X500 M.S.COLUMNCAPITAL50 M.S. TOP CHORD300 M.S.COLUMN
SECTIONM.S. COLUMN CAPITALDISTRIBUTERS POINTLOAD ACTING ON ITFIBRE GLASS ROOFINGM.S. ANGLE 50X50X6TOP CHORD M.S. PIPE 50 CONNECTING PLATE M.S. 4 MM THICKINCLINED MEM.30 M.S. PIPEM.S. COLUMN300 CONNECTING PLATEM.S. 4 MM THICKBOTTOM CHORD50 M.S. PIPEAjay/pentium 4/ D - DriveCONNECTIONS IN DOUBLE LAYERED SPACE STRUCTURS :A No. of members meet at a joint in a Two layered Grid Space Structures. Accordingly, jointing of these members at a joint poses problems due to congestion of members. A no. of standard methods are adopted to provide jointing. Some of the methods adopted are illustrated in the sketches that follow. Mero System - (developed in Germany in 1940) : This system consists of prefabricated tubular steel components screwed into forged spherical steel connectors known as Mero tubes and Mero balls respectively. The Mero joint enables upto18 members to be joined together without any eccentricity. The connectors do not requires any site welding and are capable of creating any shape of space structure merely by being screwed together.
KK SYSTEM (MERO)NODEHOLE FOR INSERTION OF BOLTWELDED SEAMSLEEVEDOWEL PINTUBEEND CONETHREADED BOLT
MERO JOINTING SYSTEM JOINTING DETAILS AT BOTTOM CHORD
THE TRIODETIC SYSTEMTUBEBOLTCHORD MEMBERSLOT JOINTNUTPLATE JOINT SYSTEMVIEW B BWEB MEMBERBOLTTUBETUBERETAINING WASHERCHORD MEMBERTUBEWEB MEMBERRETAINING WASHERSLOT JOINTSECTION A A
TYPICAL TRIODIC JOINT CONFIGURATIONS(1)(2)(3)(6)(5)(4)STEEL SKELTEL DOUBLE GRID SPACE FRAMES ALTERNAT JOINTING DETAILS
