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The shell structure system
The shell structure system
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Tos syllabus

  1. 1. 1 PRE FABRICATED MODULAR STRUCTURES GUIDED BY: SOUMYA MISS ASST PROFFESSOR, UKFCET, KOLLAM PRESENTED BY: FAIZAL.A.M 7TH SEMESTER CIVIL ENGINEERING UKFCET, KOLLAM
  2. 2. Contents Introduction Features Comparison Design concept Components Types of precast system Design consideration Equipments Assembling scheduling Advantages Limitations Conclusion references 2
  3. 3. Introduction  The concept of precast structures also known as prefabricated/ modular structures.  The structural components are standardized and produced in plants in a location away from the building site.  Then transported to the site for assembly.  The components are manufactured by industrial methods based on mass production in order to build a large number of buildings in a short time at low cost. 3
  4. 4. Features The division and specialization of the human workforce.  The use of tools, machinery, and other equipment, usually automated, in the production of standard, interchangeable parts and products.  Compared to site-cast concrete, precast concrete erection is faster and less affected by adverse weather conditions.  Plant casting allows increased efficiency, high quality control and greater control on finishes. 4
  5. 5. Comparison Site-cast  no transportation  the size limitation is depending on the elevation capacity only  lower quality because directly affected by weather  proper, large free space required Precast at plant transportation and elevation capacity limits the size- higher, industrialized quality – less affected by weather  no space requirement on the site for fabrication unlimited opportunities of architectural appearance option of standardized components 5
  6. 6. Design concept for precast concrete buildings  The design concept of the precast buildings is based on  1.build ability.  2.economy 3.standardization of precast components. 6
  7. 7. Precast concrete structural elements 7 Precast slabs Precast Beam & Girders
  8. 8. 8 Precast Columns Precast Walls
  9. 9. 9 Precast stairs Precast concrete Stairs Steel plates supported on 2 steel beams
  10. 10. Design considerations  final position and loads  transportation requirements – self load and position during transportation  storing requirements – self load and position during storing – (avoid or store in the same position as it transported / built in)  lifting loads – distribution of lifting points – optimal way of lifting (selection of lifting and rigging tools)  vulnerable points (e.g. edges) – reduction of risk (e.g. rounded edges) 10
  11. 11. Types of pre cast system 1. Large-panel systems 2. Frame systems 3. Slab-column systems with walls 4. Mixed systems 11
  12. 12. box-like structure. both vertical and horizontal elements are load-bearing. one-story high wall panels (cross-wall system / longitudinal wall system / two way system). one-way or two way slabs. 12 1. Large-panel systems
  13. 13. 2. Frame systems Components are usually linear elements. The beams are seated on corbels of the pillars usually with hinged-joints (rigid connection is also an option).  Joints are filled with concrete at the site. 13
  14. 14. 3.Lift-slab systems  - partially precast in plant (pillars) / partially precast on-site (slabs).  - one or more storey high pillars (max 5).  - up to 30 storey high constructions.  - special designed joints and temporary joints.  -slabs are casted on the ground (one on top of the other) – then lifted with crane or special elevators. 14
  15. 15. Lift-slab procedure 15 1. pillars and the first package (e.g. 5 pieces) of slabs prepared at ground level 2. lifting boxes are mounted on the pillars + a single slab lifted to the first floor level 3-8. boxes are sequentially raised to higher positions to enable the slabs to be lifted to their required final position - slabs are held in a relative (temporary) positions by a pinning system
  16. 16. Planning traffic route  How long transporter vehicle is required?  What is the required load capacity of the transporter vehicle?  What is the maximum vertical extension of the shipment  Routs on the site 16 • Is route permission required?
  17. 17. Equipments cranes:  mobile crane  tower crane (above 3stories) lifting tools:  spreader beams  wire rope slings rigging tools:  eye bolt  shakles  hooks 17
  18. 18. Assembling…. 18 Column to column connection
  19. 19. Beam to column connection 19
  20. 20. Beam-slab joints 20
  21. 21. 21 Precast concrete structure consisting of solid wall panels and hollow core slabs. Wall to slab connection
  22. 22. Advantages Quick erection times Possibility of conversion, disassembling and moving to another site Possibility of erection in areas where a traditional construction practice is not possible or difficult Low labor intensivity Reduce wastage of materials Easier management of construction sites Better overall construction quality Ideal fit for simple and complex structures 22
  23. 23. Limitations  size of the units.  location of window openings has a limited variety.  joint details are predefined.  site access and storage capacity.  require high quality control.  enable interaction between design phase and production planning.  difficult to handling & transporting. 23
  24. 24. Scheduling some approximate data for installation  emplacement of hollow core floor slabs - 300 m2/day  erection of pillars/columns - 8 pieces/day  emplacement of beams - 15 pieces/day  emplacement of double tee slabs - 25 pieces/day  emplacement of walls - 15 pieces/day  construction of stair and elevator shafts - 2 floors/day 24
  25. 25. Examples…. 25 The hospital will feature multi-trade prefabricated racks in the corridors, an approach that is still new in the U.S.
  26. 26. 26 Miami Valley Hospital Dayton,OH
  27. 27. 27 Conclusion oThe use of prefabrication and preassembly is estimated to have almost doubled in the last 15 years, increasing by 86%. oThe use of precast concrete construction can significantly reduce the amount of construction waste generated on construction sites. o Reduce adverse environmental impact on sites. o Enhance quality control of concreting work. o Reduce the amount of site labour. o Increase worker safety . o Other impediments to prefabrication and preassembly are increased transportation difficulties, greater inflexibility, and more advanced procurement requirements.
  28. 28. LARGE SPAN STRUCTURES LARGE SPAN STRUCTURES
  29. 29. Large Span Systems  Large span systems are structural systems whose dimensions exceed thelimits of standardbeams and slabsand thus require changes totheir geometry, configuration, or shape.  In general, long span systems tend towards a handfull of basic types, relying on principles of bending, compression, tensionto carry roof or floor loads overlarge distances.  Large-span structures createunobstructed, column-free spaces greater than 30 m (100 feet)for avariety of functions. The mostcommon types are : or simple beam space frame gable frame foldedplates cable stayed truss pre-stressed beam suspension pneumatic arch castellated beam
  30. 30.  Large span structures are the structures that provide large column free spaces.  They are used in roofs for halls & other hall type structures.  They are composed of steel in the form of truss system.  They are quiet strong in nature  They are unique because of their aesthetic properties..  For example they are used in airport, railway station, stadium, assembly hall, godown & temple etc.
  31. 31.  Materials suitable for various forms of long span and complex structure span and complex structure  1. All reinforced concrete including precast  2. All metal (e.g. mild-steel, structural steel, stainless steel or alloyed alumimum,  3. All timber  4. Laminated timber  5. Metal/RC combined  6. Plastic-coated Textile material  7. Fiber reinforced plastic
  32. 32.  Common Structural Forms Common Structural Forms for Long Span Building Structures for Long Span Building Structures  1. Insitu RC, tensioned  2. Precast concrete, tensioned  3. Structural steel – erected on spot  4. Structural steel – prefabricated and installed on spot  5. Portal frame – insitu RC  6. Portal frame – precast  7. Portal frame – prefabricated steel
  33. 33.  Large span structures can be constructed by-  Shell structures.  Folded plate.  Trusses  Steel space frame.  Coffered slab
  34. 34. SHELL STRUCTURES  A SHELL STRUCTURE IS A THIN CURVED MEMBRANE OR SLAB USUALLY OF REINFORCED CONCRETE THAT FUNCTIONS BOTH AS STRUCTURE AND COVERING.  THE TERM “SHELL” IS USED TO DESCRIBE THE STRUCTURES WHICH POSSESS STRENGHT AND RIGIDITY DUE TO ITS THIN, NATURAL AND CURVED FORM SUCH AS SHELL OF EGG, A NUT, HUMAN SKULL, AND SHELL OF TORTISE
  35. 35.  It transmits load more than 2 directions to support.  It is highly efficient.  Shaped, proportioned & supported  It transmits load without bending or twisting.  Its thickness is small compared to its other dimension.  Deformation not large as compared to its thickness.  Consist of shearing stress which should be normal to the middle surface and should be negligible  Application: Used in fuselages of aero plane, boat hulls, roof structures. • .. SHELLS OCCURING IN NATURE
  36. 36.  Depending upon the geometry of middle surface the shells can be classified as : 1.Domes 2.Shell Barrel Arch / Vault 3.Translation shells 4.Ruled Surfaces shell
  37. 37. DOMES  Are hemispherical in shape.  Used as roof structure.  Constructed of stone , concrete & brick.  Supported on circular / regular polygon shaped walls.  Have certain height & diameter ratio.  Have very small thickness.  Can b constructed with or without lanterns.  Are of 2 types:  i. Smooth shell domes & ii Ribbed shell domes RIBBED SHELL DOMES SMOOTH SHELL DOMES
  38. 38. TYPES OF DOMES SPHERICAL DOMES TRIANGULAR DOME CYLINDERICAL DOME RECTANGULAR DOME
  39. 39. SHELL BARREL VAULT  Is an Arched form.  Used to provide a space with ceiling or roof.  Elements of barrel shell: *Curved membrane *Tension zone *Rise *Span *Width *Edge beams *End frame of diaphragm
  40. 40. TYPES OF SHELL VAULTS MULTI BARREL VAULT CANTILEVER BARREL VAULT SHORT SPAN BARREL VAULT NORTH LIGHT BARREL VAULT
  41. 41. TRANSLATION SHELL  Is a type of shell structure.  Dome set on four arches  Different from spherical dome  Easier to form than spherical dome  Obtained by moving a vertical curve parallel to itself along another vertical curve usually in plane at right angles to the plane of sliding curve.  High tension forces in the corner.  Special cases are: 1.Cylindrical shell & 2. Hyperbolic paraboloid
  42. 42. HYPERBOLIC PARABOLOID  Is a special case of translation shell.  Obtained by sliding a vertical parabola with upward curvature on another parabola with downward curvature in a plane at right angles to the plane of first.  Carries load on 2 directions.  Diagonal element sags in tension  Other element is an arch which is in compression.  Consist of saddle surface.
  43. 43. STEEL SPACE FRAMES  Are used in the form of grids of rectangular, diagonal , triangular or hexagon pattern, arches domes &other large column free areas.  Highly efficient.  Obtained by connecting the parallel trusses, not by flexible elements but by transverse trusses as rigid as the main truss.  Deflection of the truss is transmitted to the adjoining trusses & the entire roof works act more or less monothically.  Such special systems of hinged bar are called SPACE FRAMES.  Offers an economical solution to roofing of large rectangular areas.  Are stiffer than system of parallel trusses.  Shallower in depth .
  44. 44. TYPES OF SPACE FRAMED SYSTEMS  BRACED BARREL VAULT STRUCTURE The braced double layer barrel vault is composed of member elements arranged on a cylindrical surface. The basic curve is a circular segment; occasionally, a parabola, ellipse or funicular line may also be used. Its structural behavior depends mainly on the type and location of supports, which can be expressed as L/R, where L is the distance between the supports in longitudinal direction and R is the radius of curvature of the transverse curve
  45. 45.  RIBBED DOME STRUCTURE Ribbed dome is the earliest type of braced dome that has been constructed . A ribbed dome consists of a number of identical meridional solid girders or trusses, interconnected at the crown by a compression ring. The ribs are also connected by concentric rings to form grids in trapezium shape. The ribbed dome is usually stiffened by a steel or reinforced concrete tension ring at its base.
  46. 46.  GEODESIC DOMED STRUCTURE The framework of these intersecting elements forms a three-way grid comprising virtually equilateral spherical triangles  HIPPED END STRUCTURE is a type of roof where all sides slope downwards to the walls, usually with a fairly gentle slope. Thus it is a house with no gables or other vertical sides to the roof. A square hip roof is shaped like a pyramid. Hip roofs on houses could have two triangular sides and two trapezoidal ones. A hip roof on a rectangular plan has four faces. They are almost always at the same pitch or slope, which makes them symmetrical about the centerlines
  47. 47.  POLYGONAL DOMED STRUCTURE ADVANTAGES OF SPACE FRAMES  One of the most important advantages of a space structure is its lightweight. This is mainly due to the fact that the material is distributed spatially in such a way that the load transfer mechanism is primarily axial — tension or compression.  Space frames can be built from simple prefabricated units, which are often of standard size and shape. Such units can be easily transported and rapidly assembled on site by semi-skilled labor. Consequently, space frames can be built at a lower cost.  A space frame is usually sufficiently stiff in spite of its lightness. This is due to its three dimensional character and to the full participation of its constituent elements.  Space frames possess a versatility of shape and form and can utilize a standard module to generate various flat space grids, latticed shell, or even free-form shapes.
  48. 48. What is the difference between truss and frame?  1. Truss is essentially a frame and is fabricated using the structural steel. 2. Truss is a flexural member and is normally used for supporting a roof. 3.Truss is composed of many triangles connected together . 4. Frames, on the other hand have right angles between different members ( such as a door fame , window frame, portal frame )  1- The joints in a truss are pinjointed whereas in case of frames rigid joints are provided by bolting or welding. In a truss, the joints are pin type joints and the members are free to rotate about the pin. As such, a truss cannot transfer moments and members are subjected to only axial forces (tensile and compression). On the other hand, members of frames are connected rigidly at joints by means of welding and bolting. Therefore the joints of frames can transfer moments in addition to the axial loads. 2- Truss memebers are designed for axial force(tensile or compression) only i.e. there is no bending moment in trusses while on the other hand frames are designed shear force and bending moment  Trusses are 2 dimensional. Space frame 3-d In a practical setting, you may see trusses with no flexibility in joints, but it is still acceptable to analyze them as a perfect truss.
  49. 49. FOLDED PLATE STRUCTURES  Consist of series of thin planer elements.  Flat plates are connected to one another along their edges.  Used in long span especially for roofs.  Give mutual support to each other.  Plates may be continuous over their supports longitudinally.  Capable of transmitting both moment & shear or only shear.  These plates carry the load from slab longitudinally to the support.  The support must be capable of resisting both horizontal & vertical forces.  Beam theory may be applied to design if the span is long.
  50. 50. TYPES OF FOLDED PLATE PRISMATIC: if they consist of rectangular plates. PYRAMIDAL: when consists of non-rectangular plates. PRISMOIDAL: triangular or trapezoidal.  FOLDED PLATE BEHAVIOR Each plate is assumed to act as a beam in its plane ,this assumption is justified when the ratio of The span “length” of the plate to its height “width” is large enough . But when this ratio is small, the plate behaves as a deep beam.
  51. 51. COFFERED SLAB STRUCTURES  A coffer in architecture is a sunken panel in the shape of a square, rectangle, or octagon in a ceiling, or vault.  A series of these sunken panels were used as decoration for a ceiling or a vault.  Also known as caissons ('boxes"), or lacunaria ("spaces, openings").  The strength of the structure is in the framework of the coffers.  The stone coffers which is cut in soft tufa-like stone reproduces a ceiling with beams and cross-beams lying on them, with flat panels fillings the lacunae.  Wooden coffers were first made by crossing the wooden beams of a ceiling.  Experimentation with the possible shapes of coffering, which solve problems of mathematical tiling, or tessellation, were a feature of Islamic as well as Renaissance architecture.  The more complicated problems of diminishing the scale of the individual coffers were presented by the requirements of curved surfaces of vaults and domes.  Example of Roman coffering, employed to lighten the weight of the dome, can be found in the ceiling of the rotunda dome.
  52. 52. TRUSSES  A truss is a structural frame based on the geometric rigidity of the triangle. Linear members are subjected only to axial tension and compression. They support load much like beams but for larger spans.  To prevent secondary shear and bending stresses from developing, the centroidalaxes of the truss members and the load at a joint should pass through a common point
  53. 53. Different types of Wooden and Steel Roof Trusses:  King Post Truss  Queen Post Truss  Howe Truss  Pratt Truss  Fan Truss  North Light Roof Truss/ SAWTOOTH TRUSS  Quadrangular Roof Truss  Tubular Steel Roof Truss  Tubular Monitor Steel Roof Truss King Post Truss •King Post Truss is a wooden truss. •It can also be built of combination of wood and steel. •It can be used for spans upto 8m.
  54. 54.  Queen Post Truss •Queen Post Truss is also a wooden truss. •It can be used for spans upto 10m.  Howe Truss •It is made of combination of wood and steel. •The vertical members or tension members are made of steel. •It can be used for spans from 6-30m.  Pratt Truss •Pratt Truss is made of steel. •These are less economical than the Fink Trusses. •Vertical members are tension and diagonal members are compression. •Fink Trusses are very economical form of roof trusses. •It can be used for spans from 6-10m.
  55. 55. Fan Truss •It is made of steel. •Fan trusses are form of Fink roof truss. •In Fan Trusses, top chords are divided into small lengths in order to provide supports for purlins which would not come at joints in Fink trusses. •It can be used for spans from 10-15m.  North Light Roof Truss •When the floor span exceeds 15m, it is generally more economical to change from a simple truss arrangement to one employing wide span lattice girders which support trusses at right angles. •In order to light up the space satisfactorily, roof lighting has to replace or supplement, side lighting provision must also be made for ventilation form the roof. •One of the oldest and economical methods of covering large areas is the North Light and Lattice girder. •This roof consists of a series of trusses fixed to girders. The short vertical side of the truss is glazed so that when the roof is used in the Northern Hemisphere, the glazed portion faces North for the best light. •It can be used for spans from 20-30m. •Used for industrial buildings, drawing rooms etc.
  56. 56.  Quadrangular roof Trusses • These trusses are used for large spans such as railway sheds and Auditoriums. LARGE SPAN TRUSSES TUBULAR STEEL ROOF TRSSES are used for large span constructions such as factories, industry worksheds, shopping malls, huge exhibition centres, multiplexes etc. They are generally used for spans as large as 25-30m.
  57. 57.  Advantages of Tubular Steel Roof Trusses • Structures designed for material handling equipments (e.g., a bridge and a tower crane) where weight savings may be very substantial economic consideration. • 30% to 40% less surface area than that of an equivalent rolled steel shape. Therefore, the cost of maintenance, cost of painting or protective coatings reduce considerably. • The moisture and dirt do not collect on the smooth external surface of the tubes. Therefore, the possibility of corrosion also reduces. • The ends of tubes are sealed. As a result of this, the interior surface is not subjected to corrosion. The interior surface do not need any protective treatment. • They have more torsional resistance than other section of the equal weight. • They have a higher frequency vibrations under dynamic loading than the other sections including the solid round one.
  58. 58. •The Vierendeel truss/girder is characterized by having only vertical members between the top and bottom chords and is a statically indeterminate structure. Hence, bending, shear and axial capacity of these members contribute to the resistance to external loads. •The use of this girder enables the footbridge to span larger distances and present an attractive outlook. •However, it suffers from the drawback that the distribution of stresses is more complicated than normal truss structures. VIERENDEEL TRUSS •Elements in Vierendeel trusses are subjected to bending, axial force and shear , unlike conventional trusses with diagonal web members where the members are primarily designed for axial loads DISADVANTAGES •Vierendeel trusses are usually more expensive than conventional trusses. •Their use limited to instances where diagonal web members are either obtrusive or undesirable •but the resulting joints are often very heavy in appearance. LOAD DISTRIBUTION Vierendeel trusses are moment resisting. Vertical members near the supports are subject to the highest moments and therefore require larger sections to be used than those at mid-span. Considerable bending moments must therefore be transferred between the verticals and the chords, which can result in expensive stiffened details. ADVANTAGES •The joints may be heavy, but the absence of diagonals makes this form suitable for storey-height construction. •Using standard computer programs, the analysis is not difficult, However the system does allow full storey-height construction without obstruction to openings. Vierendeel bridge at Grammene, Belgium
  59. 59. TENSILE STRUCTURES
  60. 60. The term ‘tensile structures’ covers a broad category of structures: •Fabric membranes •Pre-stressed cable nets •Cable beams in form of trusses and girders •Although compression, bending and shear maybe present in some of these structures, tension stress is more prominent. •Compared to bending and compression , tensile elements are more efficient as they use the material to its full capacity. •Bending elements use only half the material effectively, since bending stress varies from compression to tension with zero stress at neutral axis. •Compression elements are subjected to bucking of reduced capacity as slenderness increases. •However, the efficiency of tensile structures depends greatly on the type of support. Tensile structures are characterized by the prevalence of tension force in their structural systems and by limitation of compression Forces to a few support members. Thus These lightweight structures do not require The considerable amount of construction Material to absorb the Buckling and bending Moments in compression members. Tension Compression
  61. 61. Elements of a membrane structure: •Highly flexible fabric held under tension in order to generate stiffness in surface •One-dimensional flexible elements i.e. ties or cables to creates ridges, valleys and edge boundaries •Rigid support members sustaining compression/bending Note: Cable structures are constructed using a combination of the first two elements. Cable structures can be tensioned by applying direct axial forces to the cables or by loading free suspended cables with heavy cladding/decking.
  62. 62. Three main categories: •Boundary tensioned membranes •Pneumatic structures •Pre-stressed cable nets and beams Boundary Tensioned Membranes •Lightweight (typically 0.7–1.4 kg/m2 ), highly flexible membranes with a level of pre-tension which generates stiffness in the surface. •The overall equilibrium of the structure is provided by rigid edges and supporting members generally subjected to compression and/or bending. •Under imposed load due to snow or wind, the fabric surface undergoes large displacements and a consequent increase in the material stress, which can increase up to ten fold. For this reason a safety factor higher than four is highly recommended. •Membrane structures are basically realised with coated fabrics, with growing interest towards open mesh coated fabrics and foils. •Coating layer can be of either PVC, PTFE (polytetrafluroethlyene) or PVDF (polyvinylidine difluride)
  63. 63. Pneumatic Structures •The term pneumatic structures includes all the lightweight structures in which the load bearing capacity is achieved by means of air under pressure. •They are mainly subdivided into two categories: the buildings characterised by a single layer, stabilised by a slight difference in pressure between the inside and the outside of the structures, and the building envelopes stabilised by air under pressure enclosed between two or more membrane layers. •Air-supported structures provide a cost effective alternative for seasonal wide span coverings, nevertheless, the reduced resistance under bad weather conditions combined with high costs due to great pressure losses, reduced insulation, maintenance and the seasonal mounting and dismounting costs can progressively reduce the initial convenience over the entire life span
  64. 64. Pre-stressed Cable Nets, Beams and Domes •Cable structures are load bearing structures composed of linear flexible elements under tension, with the only exception being rigid members or supports such as rigid ring beams or masts. •They can be subdivided in cable nets, which describe three-dimensional surfaces, cable domes and their two-dimensional version represented by cable trusses. •Cable nets share the basic physical principles which regulate their equilibrium and shape with the boundary tensioned membranes described above. •Cable domes are based on a slightly different structural scheme which is generally circular in plan and based on radial trusses made of cables with the only exception of vertical compression struts. •Cable trusses mostly present a planar structure, with a top cable and a bottom cable with a considerable cross-sectional area due to their load bearing function. •The load bearing capacity of pre-stressed cable nets, domes and beams depends on the geometry chosen, the level of pre-stress and the allowable deformation and fatigue strength of each member, the higher the pre-tension the lower the deflection under external loads, but with a consequent increase in costs and material stress.
  65. 65. Cables can be of mild steel, high strength steel , stainless steel or polyester or aramid fibres. Structural cables are made of a series of small strands twisted or bound together to form a much larger cable. The tensioned members are termed as cables are group of wires, strands or ropes. A wire is a continuous length of steel that has a circular cross section. Cables do not loose strength in case of failure of one wire. The wires in the strand are zinc coated and stranded into helix whichforms a regular cross section. Cables
  66. 66. Cable Stayed Structures •Usually used in bridges. •Adaptation of suspension bridge principle. •The deck structure is supported by tension stays sloping from one or more towers. •There may be either a single plane of stays down the centre of the bridge, or two planes; one on each side of the bridge. •The towers act in compression and can have a variety of forms (A-frame, H-frame or columns). The deck girders sustain compression forces as well as bending forces. •Economic spans range from 200m to over 850m, and as such cable-stayed bridges fill the gap between large arches / trusses and small suspension bridges. •Span/depth ratio is an important design factor-A shallow depth results in great tension and compression in stays and beams respectively, a steep slope has opposite effect.
  67. 67. Cable Suspended Structures •Used for long-span roofs. •Suspended cables effectively resist gravity loads in tension burt are unstable under wind uplift and uneven loads. •Suspended Structures are those with horizontal planes i.e. floors are supported by cables (hangers) hung from the parabolic sag of large, high-strength steel cables. The strength of a suspended structure is derived from the parabolic form of the sagging high strength cable. To make this structure more efficient, the parabolic form is so designed that its shape closely follows the exact form of the moment diagrams. •The large curving cable may consist of many smaller cables which are tightly spun together. As the cables are being spun together, they are also stretched over the span and attached to the supports.
  68. 68. •Stadiums •Stages •Covered malls •Walkways •Play areas •Entrances •Atriums •Sports arenas •Airports •As fabric cladding panels
  69. 69. •Unique building medium. •Lightweight and flexible, fabric interacts with and expresses natural forces. •Fabric structures have higher strength/weight ratio than concrete or steel. Most fabrics can be A fabric structure can be designed for almost any condition, heavier fabrics and more 3 dimensional frecycled. •forms will cope with extreme wind and snow loads. •Translucency – In daylight, fabric membrane translucency offers soft diffused naturally lit spaces reducing the interior lighting costs while at night, artificial lighting creates an ambient exterior luminescence. •Low Maintenance – Tensile membrane systems are somewhat unique in that they require minimal maintenance when compared to an equivalent-sized conventional building. •Cost Benefits – Most tensile membrane structures have high sun reflectivity and low absorption of sunlight, thus resulting in less energy used within a building and ultimately reducing electrical energy costs. •Fabric structures being mainly fabric and cables have little or no rigidity and therefore must rely on their form and internal pre-stress to perform the this function. •As a rule of thumb spans greater than 15 metres should be avoided however, much greater spans can be achieved by reinforcing the fabric with webbing or cables. •Loss of tension is dangerous for the stability of the structure and if not regularly maintained will lead to failure of the structure.
  70. 70. SPACEFRAMES MBS SCHOOL OF PLANNING AND ARCHITECTURE THEORY OF STRUCTURES - SPACEFRAMES IV A ALANKRITA | DIVYA | GARIMA | KHUSHBOO | SHASHI | SHRISHTI SPACE FRAME
  71. 71. A space frame is a truss-like, lightweight rigid structure constructed from interlocking struts in a geometric pattern. • A three-dimensional structures. • The assembled linear elements are arranged to transfer the load. • Take a form of a flat surface or curve surface. • Designed with no intermediate columns to create large open area. • Space frames usually utilize a multidirectional span, and are often used to accomplish long spans with few supports. • They derive their strength from the inherent rigidity of the triangular frame; flexing loads (bending moments) are transmitted as tension and compression loads along the length of each strut. MBS SCHOOL OF PLANNING AND ARCHITECTURE THEORY OF STRUCTURES - SPACEFRAMES IV A ALANKRITA | DIVYA | GARIMA | KHUSHBOO | SHASHI | SHRISHTI • Space frames are an increasingly common architectural technique especially for large roof spans in modernist commercial and industrial buildings
  72. 72. MBS SCHOOL OF PLANNING AND ARCHITECTURE THEORY OF STRUCTURES - SPACEFRAMES IV A ALANKRITA | DIVYA | GARIMA | KHUSHBOO | SHASHI | SHRISHTI TYPES OF SPACE FRAMES According to curvature 1- Flat covers These structures are composed of planar substructures. The plane are channeled through the horizontal bars and the shear forces are supported by the diagonals. 2- Barrel vaults This type of vault has a cross section of a simple arch. Usually this type of space frame does not need to use tetrahedral modules or pyramids as a part of its backing. 3- Spherical domes These domes usually require the use of tetrahedral modules or pyramids and additional support from a skin. According to the number of grid layers 1- Single-Layer All elements are located on the surface to be approximated. 2- Double-Layer The elements are organized in two parallel layers with each other at a certain distance apart. The diagonal bars connecting the nodes of both layers in different directions in space. 3- Triple-Layer Elements are placed in three parallel layers, linked by the diagonals. They are almost always flat. This solution is to decrease the diagonal members length.
  73. 73. MBS SCHOOL OF PLANNING AND ARCHITECTURE THEORY OF STRUCTURES - SPACEFRAMES IV A ALANKRITA | DIVYA | GARIMA | KHUSHBOO | SHASHI | SHRISHTI TYPES OF SPACE FRAME 1) Two and three-way grids  Characterized as two way or three way 2) Single, Double and Triple Layered  Single layer frame has to be singly or doubly curved.  Commonly used space frames are double layered and flat.  Triple layered is practically used for a large span building. i. Skeleton (braced) frame work e.g. domes, barrel vaults, double and multiplier grids, braced plates. They are more popular. They are innumerable combinations and variation possible and follow regular geometric forms. ii. Stressed skin systems e.g. Stressed skin folded plates, stressed skin domes and barrel vaults, pneumatic structures. iii. Suspended (cable or membrane) structures e.g. Cable roofs
  74. 74. MBS SCHOOL OF PLANNING AND ARCHITECTURE THEORY OF STRUCTURES - SPACEFRAMES IV A ALANKRITA | DIVYA | GARIMA | KHUSHBOO | SHASHI | SHRISHTI COMPONENTS OF SPACE FRAME  Consists of axial members : which are tubes and connectors  TUBES 1) CIRCULAR HOLLOW SECTIONS 2) RECTANGULAR HOLLOW SECTIONS  CONNECTORS 1) Tuball Node Connector  A hollow sphere made of spheroidal graphite  The end of the circular hollow section member to be connected is fitted at its ends by welding.  Connection from inside the cup is using bolt and nut. 2) Nodus Connector • It can accept both rectangular and circular hollow sections and that the cladding can be fixed directly to the chords. • Chord connectors have to be welded to the ends of the hollow members on site.
  75. 75. MBS SCHOOL OF PLANNING AND ARCHITECTURE THEORY OF STRUCTURES - SPACEFRAMES IV A ALANKRITA | DIVYA | GARIMA | KHUSHBOO | SHASHI | SHRISHTI 3) Triodetic Connector • It consists of a hub, usually an aluminium extrusion, that has slots or key ways, which the ends of members are pressed or coined to match the slots. 4) Hemispherical Dome Connector • Usually use for double layer domes. • Has a span more than 40m. • More economical for long span. • The jointing is connect by slitting the end of the tube or rod with the joint fin. • There are 2 types of joint, pentagonal joint and hexagonal joint. Load Distribution Some space frame applications include: • Hotel/Hospital/commercial building entrances • Commercial building lobbies/atriums • Parking canopies Tension
  76. 76. MBS SCHOOL OF PLANNING AND ARCHITECTURE THEORY OF STRUCTURES - SPACEFRAMES IV A ALANKRITA | DIVYA | GARIMA | KHUSHBOO | SHASHI | SHRISHTI METHOD OF SUPPORT 1. Support along perimeters—This is the most commonly used support location. The supports of double layer grids may directly rest on the columns or on ring beams connecting the columns or exterior walls. Care should be taken that the module size of grids matches the column spacing. 2. Multi-column supports—For single-span buildings, such as a sports hall, double layer grids can be supported on four intermediate columns . Figure 13.5a For buildings such as workshops, usually multi-span columns in the form of grids . Figure 13.5b Sometimes the column grids are used in combination with supports along perimeters . Figure 13.5c Overhangs should be employed where possible in order to provide some amount of stress reversal to reduce the interior chord forces and deflections. Figure 13.6 3. Support along perimeters on three sides and free on the other side—For buildings of a rectangular shape, it is necessary to have one side open, such as in the case of an airplane hanger or for future extension.
  77. 77. MBS SCHOOL OF PLANNING AND ARCHITECTURE THEORY OF STRUCTURES - SPACEFRAMES IV A ALANKRITA | DIVYA | GARIMA | KHUSHBOO | SHASHI | SHRISHTI Advantages of space frame systems over conventional systems: • Random column placement • Column-free spaces • Minimal perimeter support • Controlled load distribution • Design freedom • Supports all types of roofing • Light • Elegant & Economical • Carry load by 3D action. • High Inherent Stiffness • Easy to construct • Save Construction Time & Cost • Services (such as lighting and air conditioning) can be integrated with space frames • Offer the architect unrestricted freedom in locating supports and planning the subdivision of the covered space.
  78. 78. MBS SCHOOL OF PLANNING AND ARCHITECTURE THEORY OF STRUCTURES - SPACEFRAMES IV A ALANKRITA | DIVYA | GARIMA | KHUSHBOO | SHASHI | SHRISHTI Advantages of Space Frames 1. Lightweight This is mainly due to the fact that material is distributed spatially in such a way that the load transfer mechanism is primarily axial; tension or compression. Consequently, all material in any given element is utilized to its full extent. Furthermore, most space frames are now constructed with aluminum, which decreases considerably their self-weight. 2. Mass Productivity Space frames can be built from simple prefabricated units, which are often of standard size and shape. Such units can be easily transported and rapidly assembled on site by semi-skilled labor. Consequently, space frames can be built at a lower cost. 3. Stiffness A space frame is usually sufficiently stiff in spite of its lightness. This is due to its three-dimensional character and to the full participation of its constituent elements. 4. Versatility Space frames possess a versatility of shape and form and can utilize a standard module to generate various flat space grids, latticed shell, or even free-form shapes. Architects appreciate the visual beauty and the impressive simplicity of lines in space frames.
  79. 79. MBS SCHOOL OF PLANNING AND ARCHITECTURE THEORY OF STRUCTURES - SPACEFRAMES IV A ALANKRITA | DIVYA | GARIMA | KHUSHBOO | SHASHI | SHRISHTI Disadvantages of Space Frames 1. Cost The main criticism of space grids is their cost, which can be high when compared with alternative structural systems. This is particularly true when space grids are used for short spans. 2. Visually busy structures Visually, space grid structures are very 'busy'. They are rarely seen in plan or in true elevation and at some viewing angles the lightweight structure can appear to be very dense. Grid size and depth as well as the grid configuration can have considerable influence on the perceived density of the structure. 3. Longer erection times The number and complexity of joints can lead to longer erection times on site. This is obviously very dependent on the system being used and the grid module chosen. 4. Large surface area When space grids are used to support floors some form of fire protection may be required. This is difficult to achieve economically due to the high number and relatively large surface area of the space grid elements
  80. 80. MBS SCHOOL OF PLANNING AND ARCHITECTURE THEORY OF STRUCTURES - SPACEFRAMES IV A ALANKRITA | DIVYA | GARIMA | KHUSHBOO | SHASHI | SHRISHTI SPACE FRAME METHODS OF ERECTION • The method chosen for erection of a space frame depends on its behavior of load transmission and constructional details, so that it will meet the overall requirements of quality, safety, speed of construction, and economy. • The scale of the structure being built, the method of jointing the individual elements, and the strength and rigidity of the space frame until its form is closed must all be considered. 1- SCAFFOLD METHOD Individual Elements are Assembled in Place at Actual Elevations, members and joints or prefabricated subassembly elements are assembled directly on their final position. Full scaffoldings are usually required for this type of erection. Sometimes only partial scaffoldings are used if cantilever erection of space frame can be executed. The elements are fabricated at the shop and transported to the construction site, and no heavy lifting equipment is required. 2. BLOCK ASSEMBLY METHOD The space frame is divided on its plan into individual strips or blocks. These units are fabricated on the ground level, then hoisted up into its final position and assembled on the temporary supports. With more work being done on the ground, the amount of assembling work at high elevation is reduced. This method is suitable for those double-layer grids where the stiffness and load-resisting behavior will not change considerably after dividing into strips or blocks, such as two-way orthogonal latticed grids, orthogonal square pyramid space grids, and the those with openings. The size of each unit will depend on the hoisting capacity available.
  81. 81. MBS SCHOOL OF PLANNING AND ARCHITECTURE THEORY OF STRUCTURES - SPACEFRAMES IV A ALANKRITA | DIVYA | GARIMA | KHUSHBOO | SHASHI | SHRISHTI EXAMPLES OF POPULAR BUILDINGS WITH SPACEFRAMES INDIAN HABITAT CENTRE , LODHI ROAD JEEVAN BHARTI BUILDING, CP HALL OF NATIONS, PRAGTI MAIDAN STANSED AIRPORT, LONDON RAILWAY STATIONS SUPPORTED BY BARREL VAULT STRUCTURE LOUVRE PYRAMID, LOUVRL PALACE, PARIS
  82. 82. MBS SCHOOL OF PLANNING AND ARCHITECTURE THEORY OF STRUCTURES - SPACEFRAMES IV A ALANKRITA | DIVYA | GARIMA | KHUSHBOO | SHASHI | SHRISHTI JOINTING SYSTEMS AND TERMINOLOGY JOINTING SYSTEMS • The jointing system is an extremely important part of a space frame design. The joints for the space frame are more important than the ordinary framing systems because more members are connected to a single joint • Also, the members are located in a three dimensional space, and hence the force transfer mechanism is more complex • The type of jointing depends primarily on the connecting technique, whether it is bolting, welding, or applying special mechanical connectors. It is also affected by the shape of the members. • This usually involves a different connecting technique depending on whether the members are circular or square hollow or rolled steel sections. • Requirements considered for designing the jointing systems :-The joints must be strong and stiff, simple structurally and mechanically, and easy to fabricate without recourse to more advanced technology and joints of space frames must be designed to allow for easy and effective maintenance • All connectors can be divided into two main categories: the purpose-made joint and the proprietary joint used in the industrialized system of construction • Purpose-made joints-usually used for long span structures where the application of standard proprietary joints is limited. Example -cruciform gusset plate for connecting rolled steel sections. • All the connection techniques can be divided into three main groups: (1) with a node (2) without a node, and (3) with prefabricated units. TERMINOLOGIES • Aspect ratio: Ratio of longer span to shorter span of a rectangular space frame. • Braced (barrel) vault: A space frame composed of member elements arranged on a cylindrical surface. • Braced dome: A space frame composed of member elements arranged on a spherical surface. • Depth: Distance between the top and bottom layer of a double layer space frame. • Double layer grids: A space frame consisting of two planar networks of members forming the top and bottom layers parallel to each other and interconnected by vertical and inclined members. • Geodesic dome: A braced dome in which the elements forming the network are lying on the great circle of a sphere. • Lamella: A unit used to form diamond shaped grids, the size being twice the length of the side of the diamond. • Latticed grids: Double layer grids consisting of intersecting vertical latticed trusses to form regular grids. • Latticed shell: A space frame consisting of curved networks of members built either in single or double layers. • Latticed structure: Astructuralsystemintheformofanetworkofelementswhoseload-carrying mechanism is three-dimensional in nature. • Local buckling: A snap-through buckling that takes place at one point. • Module: Distance between two joints in the layer of grid. • Space frame: A structural system in the form of a flat or curved surface assembled of linear elements so arranged that forces are transferred in a three-dimensional manner. • Space grids: Double layer grids consisting of a combination of square or triangular pyramids to form offset or differential grids. • Space truss: A three-dimensional structure assembled of linear elements and assumed as hinged joints in structural analysis.
  83. 83. Arunima G Prabhnoor S Raunak R Saurabh K Sudhanshu M Tanvi G Steel Trusses
  84. 84. Steel Trusses Introduction • Steel trusses were taken up as against wooden trusses because the scarcity of quality timber was increasing in manyareas. • Steel is alsoa superior buildingconstruction material when compared to wood. Unlike timber, it is a homogenous and isotropic material, i.e. it has same characteristics in all directions. • Another major advantage steel provides in roof trusses is that it is much lighter and often more economical in large roof systems. Tension
  85. 85. Steel Trusses Roof truss design The following are the conditions that influence the design of aroof truss: 1. Loads: Roof trusses are especially adapted to such buildings where they support the roof and still afford a clear space without the use of intermediate columns. They support loads of various kinds, such as the dead load, due to the weight of material used in constructing and covering the roof, the wind load, the snow load, and frequently the weight of plastered ceilings, as well as loads from attic floors and from suspended platforms and galleries. In laying out the stress diagrams, all these loads are considered, and both members and details are then proportioned to withstand the various stresses produced. Purlins, that rest on and connect the trusses at their panel points, or points at which the main rafter and the web members intersect. These purlins support the rafters of the roof, on which the wood sheathing and roofing material are placed. In iron and steel construction I beams and Z bars are generally employed. Great care should be taken to avoid, as far as possible, the accidental stresses to which trusses are so often subjected duringerection, and which can scarcely be calculated. 2. Slope of Roof: The character of the roofingmaterial must be consideredin determining the direction of the upper chord. For instance, when shingles are used, the pitch should not be less than 1 of rise to 2 of run, while with slates if the pitch is less than 1 to 3, the wind is liable to blow the rain under the slate, thereby causing leaks. A slope of 1 to 2, however, is preferable for slate, although, when occasion requires, the minimum pitch of 1 to 3 may be employed. Corrugated iron is liable to leak if laid with a pitch of less than 1 to 3, while in a gravel and tar roof, if the slope is greater than 1 to 4, the heated tar is apt to run down and collect at the lower portion of the roof, leaving the upper part exposed and unprotected, and rain falling on such a roof flows off so quickly that the pebbles are washed out of the roofing. Flat clay tile set in asphalt may be used on flat roofs, but clay and metal tile simulating corrugated or Spanish tile are usually laid with a pitchsomewhatgreater than 1 to 2.
  86. 86. Steel Trusses Roof truss design 3. Distance between Trusses: The fact that the economyof the design is so largely dependent on the spacing of the trusses, makes it necessary that an effort be made to ascertain the distance that may most economically exist between them.This is especiallythe case when the building over which they are to be placed is of sucha character that the spacing of the trussesgoverns, or, at least, affects the exteriordesign. Often, too, the engineer is restricted by the fact that the size of the lot must be considered when determining the size of the building, and hence, the distancebetween the trusses is influencedto a certain degree, particularly when architectural effect is desired. 4. Material used: The general design of a truss is influenced by the material employed in its construction, and the choice of material is influenced by its costand availability, as well as by the span of the truss and the loadsthat come on it. When the span exceeds 80 feet, and the loads are comparativelyheavy, steel is usuallythe best material to use; but if steel is unavailable, timbermay be used for trusses having spans as great as 150 feet. When timber trusseshave as great a spanas this, they are usually arched, and built in pairs. While steelmay be used for the construction of trusses of all spans,great and small, the designer is frequentlycompelled to use timber because the costof the work is limited. 5. After the general dimensions of the roof truss have been determined, if economy is to be considered, the cost mustbe investigated. Shouldthe conditions admit a choiceof several designs, it is often desirableto estimate the cost of each, and adopt the one whose construction costs the least. In designing trussesit is generally cheaper to use stock sizes of timber or steel shapes, for by so doing,even though the membersare of a largersize than actually required, the work is usually facilitated to such an extent that the timerequired in its performance is materially reduced, whichis frequently a factorof the utmostimportance.
  87. 87. Steel Trusses System options Steelsectionsare available in many different extrusiontypes and systems, the following may be used for steel roof trusses: Angle and flat bar truss: • Small angle bars may be welded directlyonto each other forming very light trusses up to about 12 m span. • The length of the compression members mustbe reduced as muchas possible to avoid buckling.This results in trusses with a large numberof diagonalsand connections. • Examples: Fink or Polonceau Truss. Steel tube truss: • Steel tubes are readily available throughout the worldand at reasonable prices,since they are also used for steel pipes and pipingsystems. • The jointing of the round surfacesis difficult; buttand fillet welding of properly cut and shaped tubesis possiblebut slow and expensive. • When usingtubes, the number of connections per truss should be reduced as much as possible.
  88. 88. Steel Trusses System options Rolled sections truss: • Rolled sections other than angle bars used in truss designs are the channeland universal beams. • Half-section universal beams are particularly useful in truss design but are not readilyavailable. • Used in trusses of spans larger than 12 m. Rectangularhollow section truss: • • RHS providea particularly neat appearance of steel trusses. Welded connections are common thanksto the regularshapes of the RHS. • RHS are particularly expensive and are not readily available in many countries.
  89. 89. PINNED/BOLTED CONNECTIONS TYPICALLY, THE JOINT CONNECTIONS ARE FORMED BY BOLTING OR WELDING THE END MEMBERS TOGETHER TO A COMMON PLATE, CALLED A GUSSET PLATE. JOINING DETAILS Generally in steelwork construction, bolted site splices are preferred to welded splices for economy and speed of erection.
  90. 90. •CHORDS The outer members of a truss that defi ne the envelope or shape. • TOP CHORD An inclined or horizontal member that establishes the upper edge of a truss. This member is subjected to compressive and bending stresses. •BOTTOM CHORD The horizontal (and inclined, ie. scissor trusses) member defining the lower edge of a truss, carrying ceiling loads where applicable. This member is subject to tensile and bending stresses. (On a simply supported, non-cantilevered truss). •CLEAR SPAN The horizontal distance between inside faces or supports. •HEEL The joint in a pitched truss where top and bottom chords meet. •HEEL HEIGHT - The "thickness" of a truss at the end of the Bottom Chord. Measured from the bottom of the Bottom Chord (or top of top plate) to the top of the Top Chord (underside of sheathing) at the end of the truss. •JOINT The point of intersection of a chord with the web or webs, or an attachment of pieces of lumber (eg. splice) •LATERAL BRACE A permanent member connected to a web or chord member at right angle to the truss to restrain the member against a buckling failure, or the truss against overturning. •OVERHANG The extension of the top chord beyond the heel joint. •OVERALL HEIGHT - - A vertical measurement taken at the midpoint of a truss from the bottom of the Bottom Chord to the peak. •PANEL The chord segment between two adjacent joints. •PANEL POINT The point of intersection of a chord with the web or webs. •PANEL LENGTH - The horizontal distance between the centerlines of two consecutive panel points along the top or bottom chord. • PEAK Highest point on a truss where the sloped top chords meet. •SLOPE (PITCH) The units of horizontal run, in one unit of vertical rise for inclined members. (Usually expressed as 3:12, 5:12, etc.) •SPLICE POINT The location where the chord member is spliced to form one continuous member. It may occur at a panel point but is more often placed at 1/4 panel length away from the joint. •WEBS Members that join the top and bottom chords to form the triangular patterns that give truss action. The members are subject only to axial compression or tension forces (no bending) •WEDGE - THE TRIANGULAR PIECE OF LUMBER INSERTED BETWEEN THE TOP AND BOTTOM CHORDS, USUALLY TO ALLOW THE TRUSS TO CANTILEVER.
  91. 91. Metal Roof Truss – Advantages and Disadvantages of Metal Roof Truss Structures. Metal roof trusses, just like wood trusses, have their advantages and disadvantages. Some builders prefer to the metal roof truss because the building of a structure is all about precision and metal has a more precise measurement than wood. Safety is also an issue when deciding to use a metal roof truss or a wood truss system, building codes and other procedures may require certain trusses. Advantages of Metal Roof Truss Structures •Even though they are considered to be more expensive, metal roof trusses can span further than wood. •Metal roof trusses can be manufactured to exact standards. •They are much more lightweight and this allows for larger shipments. This reduces the time it takes to get to the project site. •Metal roof trusses are fire resistant. •They are compatible with almost all types of roofing systems. •No insect infestations can occur. •Chemical treatments are not necessary to maintain the trusses. •Metal roof trusses are recyclable and therefore environmentally friendly. Disadvantages of Metal Roof Truss Structures •Skilled labor is required to install metal roof trusses. •They are not energy efficient since they allow more heat to escape from the structure. •Metal roof trusses allow sound to be more easily transmitted. •Temperature fluctuations allow them to move more. •When the metal is cut, drilled, scratched or welded, rust can become a problem. •The workers have a higher risk of electrocution when installing the metal roof trusses. •Wires that are on the trusses can rub over time creating a hazard to anyone who happens to touch the metal trusses.
  92. 92. Steel Trusses Truss forms 7. King post truss: It is the simplest form of roof truss, atriangular frame consisting of two equal rafter members connected by a tie-beam. The tie beam becomes necessarywhen the outward thrust of the rafters is too great for the resistanceof the walls. In aking post truss the bending moment on the tension member, dues to its own weightand load of the ceiling, increasesas the span of the truss increases. The section required to resist both the tensileand transverse bending stresses would necessarily be large; hence, to reduce the size of this membera suspension rod is introduced. The king post is in tension, usuallysupporting the tie beam as a truss but the crownpost is supported by the tie beam and is in compression. The crown post rises to a crownplate immediately below and supporting collar beams, it does not rise to the apex like aking post. It is limitedto a spanof 24 feet.    Simple representation of aKing post truss   Representation of aKing post truss showing jointing
  93. 93. Steel Trusses Truss forms Steel roof trusses are availablein many differentforms and systems, the following may be used for steel roof trusses: 1. Fink truss: The Fink truss offers greater economy in terms of steel weight for short-span high-pitched roofs as the members are subdivided into shorter elements. There are many ways of arranging and subdividing the chords and internal members. This type of truss is commonly used to construct roofs in houses. when made of steel it is more economical for long spans than either the howe or the pratt. Most types of roofing use a“W” pattern truss. 1/3 1/3 1/3
  94. 94. USING SIMILAR TRIANGLES, THE LENGTH (X) OF THE TOP CHORD IS DETERMINED. X/42 = 13.89/12 X = (42 X 13.89) 12 = 48.615” OR 4’ ⅝”. TRUSSES ARE BUILT ON A FLAT SURFACE AND THE PIECES ARE CUT TO SUIT THE LAYOUT MARKS. USES :  FINK TRUSSES ARE USES FOR SHORT SPAN STRUCTURES MAXIMUM 9’.  TRUSSES ARE USED FOR PITCHED ROOF IN HOMES. DISADVANTAGE :  FINK TRUSSES ARE NOT USES FOR LONG SPAN (USE FOR ONLY SMALL SPAN)
  95. 95. Steel Trusses Truss forms 2. Queen post truss (Fan Truss): Principal Rafter It is useful as a rectangular space is desiredin thecenterof the room, an atticor small hall. If the span lengthis in between8 to12 meter then queen posttrusses are used. Two vertical posts are provided in 2 sides at a distance whichare termed asqueen posts. Straining beam and strainingseal is used to keep the queen postsin exact position. Top endsof two main rafters are joined with thequeen postsheads. It can be usedin longerspans when it is cross-braced in thecenter. Double Fan The fan truss has three or four members fanningout from a common pointat the bottom of the truss. The double fan has twocommon pointswheremembersfanout.       Fan truss 3.   Double-Fan truss 4. Cambered Fink  With Fink or Fan trusses having an inclination for the rafter not exceeding 30 degrees it is more economical to employ a horizontal chord or tie since it obviates bending of the laterals.  Raising the bottom chord, also materially increases the strains in the truss members, henceit increases the cost.  A truss whose bottom chord has a rise of two or three feet, presents a better appearance, however, than one with a horizontal chord, and for steep roofs, it will generally be fully as economical toraisethe bottomchordbecause of the shorteningof the members.  Trusses with raisedties are designated as“Cambered." Queen Post
  96. 96. Steel Trusses Truss forms 6. Howe truss: The method of increasingthe number of triangles, as shown , may go on indefinitelyand the naturaloutcome is the howe truss. This truss maybe extended to very large spans by increasingthe number of panels, but it is not suitablefor steep roofs, because as the span increases,the lengthof the struts towardthe centre becomes so great as to requiretimberof large size. For long trussesthe usual rise is one- seventh of the span. With long spans, it is customaryto reduce the shear at the heel of the truss by placing the compressionmember nearest the wall more nearly vertica l. The Howe Trusswas and sometimeseven now is used in steel bridges. It's impressivestrength over long spanscontributedto its overwhelming popularityas arailroadbridge. The design of Howe truss is the oppositeto that of Pratt truss in whichthe diagonal members are slanted in the direction oppositeto that of Pratt truss (i.e. slantingaway from the middle of bridge span) and as such compressiveforces are generated in diagonal members.Hence, it is not economical to use steel members to handle compressiveforce. Simple representation of aHowe truss Representation of aHowe truss showing jointing
  97. 97. Steel Trusses Truss forms 8. Pratt truss: Pratt its similarity to the Howetruss, and the pointsof difference readilynoted. In the Pratttruss, the compression members of the web of the frame,or the struts a, a are vertical, while the tension rods b, b are oblique.In the Howe, a reversed conditionexists, for the struts are obliqueand the tension members vertical. The Pratt offers rather a betterappearance than the Howe from the fact that the oblique members, whichusually extend at differentangles, are round bars that are hardly noticeable, but in the Howethey are made of timbers, which are frequently unnecessarily heavy and far from pleasing in appearance, while the verticaltimberstruts used in the Pratt arc entirelyunobjectionable. The howe truss, however,has the advantage that the connections at c, d, and e are more conveniently made. The design uses vertical members for compression and horizontalmembers to respond to tension.   Simple representation of aPratt truss Lateral (wind) bracing Struts Sway bracing  Portal strut and bracing  Deck StringersFloor beams Representation of a Pratttruss showing jointing
  98. 98. Steel Trusses Truss forms 9.   Flat Warren truss: It is a typeof Parallel Chord truss. Warren truss containsa series of isosceles triangles or equilateral triangles. To increase the span lengthof the truss bridge, verticals are added for Warren Truss. The unique design of aWarren truss structureensures that no strut, beam or tie bends or withstands torsional straining forces but is only subject to tensionor compression. The loads on the diagonals alternate between tensionand compression,whereas the elements near the center are requiredto supportboth compression as well as tensionin response to live loads. The use of the Warrentruss design is common in prefabricated modular bridges wherein all the girders are of equal length. Warrentruss is a notchbetter than Neville truss, which has isosceles triangles filling up the entirelength of a bridgedesign. Warren TrussAdvantages - There is less material required for the constructionof aWarren truss bridge.  Simple representation of aFlat warren truss    - There is less blockage of view.  - The constituents of aWarren truss bridgecan be assembledpiece wise. Representation of a Pratttruss showing jointing
  99. 99. WARREN TRUSS ADVANTAGES - THERE IS LESS MATERIAL REQUIRED FOR THE CONSTRUCTION OF A WARREN TRUSS BRIDGE. - THERE IS LESS BLOCKAGE OF VIEW. - THE CONSTITUENTS OF A WARREN TRUSS BRIDGE CAN BE ASSEMBLED PIECE WISE. WARREN TRUSS BRIDGE DISADVANTAGES - THE MAINTENANCE OF THE JOINTS AND FITTINGS OF A WARREN TRUSS BRIDGE COULD BE EXPENSIVE. - THE CALCULATIONS TO DETERMINE THE LOAD-BEARING CAPACITY OF A WARREN TRUSS BRIDGE CAN BE HASSLING. - MANY WARREN TRUSS BRIDGES ARE NOT AESTHETICALLY APPEALING TO THE EYE. - THERE COULD BE TOO MUCH DEFLECTION FOR LONG SPANS.
  100. 100. NORTH LIGHT TRUSS  North light trusses are traditionally used for short spans in industrial workshop-type buildings. They allow maximum benefit to be gained from natural lighting by the use of glazing on the steeper pitch which generally faces north or north-east to reduce solar gain. On the steeper sloping portion of the truss, it is typical to have a truss running perpendicular to the plane of the North Light truss, to provide large column-free spaces.  The use of north lights to increase natural daylighting can reduce the operational carbon emissions of buildings although their impact should be explored using dynamic thermal modelling. Although north lights reduce the requirement for artificial lighting and can reduce the risk of overheating, by increasing the volume of the building they can also increase the demand for space heating. Further guidance is given in the Target Zero Warehouse buildings design guide .
  101. 101. SAWTOOTH TRUSS A truss made with one top chord steeper than the other, usually to add windows. A variation of the North light truss is the saw- tooth truss which is used in multi-bay buildings. Similar to the North light truss , it is typical to include a truss of the vertical face running perpendicular to the plane of the saw- tooth truss. SPAN: 5m to 8m MATERIAL : steel or timber
  102. 102.  Saw-tooth roofs may be constructed of heavy timber or steel trusses .  This is generally used in factories where more light is required. WIDELY USED TO SERVE TWO MAIN FUNCTIONS: To carry the roof load To provide horizontal stability.
  103. 103. Light fills the space from clerestory windows in the sawtooth-style roof EXAMPLES WINDOWS green house with saw tooth roof truss
  104. 104. ADVANTAGES  The major advantage of installing a saw-tooth roof truss on a structure is the uniform diffusion of light throughout the space below it.  Saw-tooth roofs prevent the influx of direct sunlight while providing northern light.  In saw-tooth design, every bay has an angled skylight. Less glare and unwanted heat also offer better working conditions, increased production  The complex design and various building materials needed will make the sawtooth roof much more expensive than other roof types.  It’s also a high maintenance roof.  Adding windows, valleys and varying slopes creates a higher chance for water leaks. For this reason, sawtooth roofs aren’t advisable in heavy snowfall areas. DISADVANTAGES APPLICATIONS o Lofts o machine shops o Warehouses o factories o Residences
  105. 105. SHELLS THEORY OF STRUCTURES GROUP MEMBERS ANJALI KOLI ANOUSHKA SHARMA KANISHKA SHARMA LIPIKA AGGARWAL SHUBHAM GUPTA TEJASVI KAUR
  106. 106.  A shell is a type of structural element which is characterized by its geometry, being a three-dimensional solid whose thickness is very small when compared with other dimensions. A shell structure is a thin, curved membrane or slab, usually of reinforced concrete, that functions both as structure and covering, the structure deriving its strength and rigidity from the curved shell forms.  Essentially, a shell can be derived from a plate by two means : by initially forming the middle surface as a singly or doubly curved surface and by applying loads which are co planar to a plate’s plane which generate significant stresses. Shell structures predominantly resist loads on them by direct compression. That is without bending or flexure.  Since most materials are more effective in compression than in bending, shell structures result in lesser thickness than flat structures TYPES:  Single curvature shells, curved on one linear axis, are part of cylindrical or cone in the form of barrel vaults and conoid shells.  Double curvature shells are either part of a sphere, as a dome, or a hyperboloid of revolution. INTRODUCTION
  107. 107. THIN CONCRETE SHELLS  The thin concrete shell structures are a lightweight construction composed of a relatively thin shell made of reinforced concrete, usually without the use of internal supports giving an open unobstructed interior. The shells are most commonly domes and flat plates, but may also take the form of ellipsoids or cylindrical sections, or some combination thereof. Most concrete shell structures are commercial and sports buildings or storage facilities. There are two important factors in the development of the thin concrete shell structures:  The first factor is the shape which was developed along the history of these constructions. Some shapes were resistant and can be erected easily. However, the designer’s incessant desire for more ambitious structures did not stop and new shapes were designed.  The second factor to be considered in the thin concrete shell structures is the thickness, which is usually less than 10 centimeters. For example, the thickness of the Hayden planetarium was 7.6 centimeters.
  108. 108. • Shells belong to the family of arches, vaulted halls and domes. We can understand that a vault is a shell with one singly curved surface and a dome is a shell with doubly curved surfaces. • A saddle shell has also doubly curved surfaces, but with a difference. If we cut a dome in two directions at right angles to one another, both cuts are convex curves. If we cut a saddle shell in the same way, one curve is convex and the other is concave. • Examples ; • Hyperbolic paraboloids and hyperboloids • Shells are generally made out of reinforced concrete : from 40m (130 ft) to 73 m in span. However, people have materialize the form of shells with space frames, lattices and membranes, allowing larger spans (up to 200 meters.)
  109. 109. The Roman Pantheon, as it stands today in the centre of the city of Rome, really is a remarkable and imposing structure. The Pantheon is a masterpiece of ancient shell construction and has withstood for almost two-thousand years. Today, the span of 43 m still impresses the engineering profession. The Pantheon, built in the early 2nd century A.C., approximately 125, is the largest unreinforced dome in the history. HISTORY
  110. 110. • The membrane behaviour of shell structures refers to the general state of stress in a shell element that consists of in-plane normal and shear stress resultants which transfer loads to the supports. In thin shells, the component of stress normal to the shell surface is negligible in comparison to the other internal stress components and therefore neglected in the classical thin shell theories. The initial curvature of the shell surface enables the shell to carry even load perpendicular to the surface by in-plane stresses only. • The carrying of load only by in-plane extensional stresses is closely related to the way in which membranes carry their load. Because the flexural rigidity is much smaller than the extensional rigidity, a membrane under external load mainly produces in-plane stresses. In case of shells, the external load also causes stretching or contraction of the shell as a membrane, without producing significant bending or local curvature changes. Hence, there is referred to the membrane behaviour of shells, described by the membrane theory. • Carrying the load by in-plane membranes stresses is far more efficient than the mechanism of bending which is often seen by other structural elements such as beams. Consequently, it is possible to construct very thin shell structures. Thin shell structures are unable to resist significant bending moments and, therefore, their design must allow and aim for a predominant membrane state. Bending stresses eventually arise when the membrane stress field is insufficient to satisfy specific equilibrium or deformation requirements. MEMBRANE BEHAVIOUR
  111. 111. Material Effects on Shell Behaviour  Reinforced concrete shells have complicated nonlinear material behaviour with strong influence on the structural behaviour. Significant tensile stresses in the shell will cause cracking and with that weakening of the shell cross-section.  Micro-cracking at the surface is caused by the evaporation of water. Due to the high amount of surface exposed the micro-cracking in the shell surface may exceed the allowable value.  Furthermore, creep of concrete will cause flattening of the shell surface, resulting in less curvature and possible bending stresses to occur. Additionally, shrinkage may lead to unwanted residual stresses.
  112. 112. CYLINDRICAL CONICAL SHELL
  113. 113. Cylindrical Shell Conical Shell They may be of wood, steel, plastic or reinforced concrete. They may form the roof and containing walls for long span structures. Cylindrical Shell is a shell that is a structure about an axis parallel to the sides of an imaginary straight sheet. It distributes wind load equally on the structure sides. Conical Shell is a shell that is a structure about an axis non- parallel to the sides of an imaginary straight sheet. It is a stable structure for standing high pressure winds.
  114. 114. The elements of a barrel shell are: (1) The cylinder, (2) The frame or ties at the ends, including the columns, and (3) The side elements, which may be a cylindrical element, a folded plate element, columns, or all combined. For the shell shown in the sketch, the end frame is solid and the side element is a vertical beam. A barrel shell carries load longitudinally as a beam and transversally as an arch. The arch, however, is supported by internal shears, and so may be calculated. They maybe used as: (1) Long-span structures (2) Short-span structures BARREL VAULTS
  115. 115. Cylindrical shell used in the roof are also known as barrel shell or vault
  116. 116. These may be of multiple numbers joined together to increase strength
  117. 117. POSSIBLE METHODS OF JOINING CYLINDRICAL CONICAL SHELLS
  118. 118. SANGATH, AHMEDABAD DELFT UNIVERSITY LIBRARY, NETHERLANDS
  119. 119.  A dome is an architectural element that resembles the hollow upper half of a sphere. There are also a wide variety of forms and specialized terms to describe them. A dome can rest upon a rotunda or drum, and can be supported by columns or piers that transition to the dome through squinches or pendentives. A lantern may cover an oculus and may itself have another dome.  A dome is a rounded vault made of either curved segments or a shell of revolution, meaning an arch rotated around its central vertical axis.  Domes have a long architectural lineage that extends back into prehistory and they have been constructed from mud, stone, wood, brick, concrete, metal, glass, and plastic over the centuries. The symbolism associated with domes includes mortuary, celestial, and governmental traditions that have likewise developed over time.  The word "cupola" is another word for "dome", and is usually used for a small dome upon a roof or turret. "Cupola" has also been used to describe the inner side of a dome. Drums, also called tholobates, are cylindrical or polygonal walls with or without windows that support a dome. A tambour or lantern is the equivalent structure over a dome's oculus, supporting a cupola. SPHERICAL DOMES
  120. 120.  As with arches, the "springing" of a dome is the point from which the dome rises. The top of a dome is the "crown". The inner side of a dome is called the "intrados" and the outer side is called the "extrados". The "haunch" is the part of an arch that lies roughly halfway between the base and the top.  A masonry dome produces thrusts down and outward. They are thought of in terms of two kinds of forces at right angles from one another.  Meridional forces (like the meridians, or lines of longitude, on a globe) are compressive only, and increase towards the base, while hoop forces (like the lines of latitude on a globe) are in compression at the top and tension at the base, with the transition in a hemispherical dome occurring at an angle of 51.8 degrees from the top.  The thrusts generated by a dome are directly proportional to the weight of its materials. Grounded hemispherical domes generate significant horizontal thrusts at their haunches.  Concave from below, they can reflect sound and create echoes. A dome may have a "whispering gallery" at its base that at certain places transmits distinct sound to other distant places in the gallery.The half-domes over the apses of Byzantine churches helped to project the chants of the clergy. BEHAVIOUR
  121. 121.  When the base of the dome does not match the plan of the supporting walls beneath it (for example, a dome's circular base over a square bay), techniques are employed to transition between the two. The simplest technique used is diagonal lintels across the corners of the walls to create an octagonal base.  Another is to use arches to span the corners, which can support more weight. A variety of these techniques use what are called "squinches". A squinch can be a single arch or a set of multiple projecting nested arches placed diagonally over an internal corner. Squinches can take a variety of other forms, as well, including trumpet arches and niche heads, or half-domes.  The earliest domes were built with mud-brick and then with baked brick and stone. Domes of wood were allowed for wide spans due to the relatively light and flexible nature of the material and were the normal method for domed churches by the 7th century.  Wooden domes were protected from the weather by roofing, such as copper or lead sheeting. Domes of cut stone were more expensive and never as large, and timber was used for large spans where brick was unavailable. Brick dome was the favoured choice for large space monumental coverings until the Industrial Age, due to their convenience and dependability. TECHNIQUES & MATERIALS
  122. 122.  A grid shell is a structure which derives its strength from its double curvature but is constructed of a grid or lattice.  The grid can be made of any material, but is most often wood or steel.  Grid shells were pioneered in the 1896 by Russian engineer Vladimir Shukhov in constructions of exhibition pavilions of the All-Russia industrial and art exhibition 1896 in Nizhny Novgorod. GRID SHELL DOME
  123. 123.  Louisiana Superdome, New Orleans  Architect: Curtis and Davis  Engineer: Sverdrup and Parcel  With a 680 ft diameter the Louisiana Superdome is the largest dome in existence.  Designed for 75,000 spectators, the multipurpose arena serves many functions from various sports events to rock concerts and political conventions.  The patented lamella dome structure features a peripheral tension ring truss. A Tension ring B Radial ribs C Diagonal struts, parallel to radial ribs D Hoop rings, combined with diagonal struts, form a diamond bracing grid E Roof joists F Metal deck G Single-ply water proof membrane EXAMPLE
  124. 124.  Walter Bauersfeld built the first geodesic dome in 1922 for a planetarium in Jena, Germany. Buckminster Fuller developed his geodesic dome for low-cost housing 1942.  A basic geodesic sphere, referred to as single frequency, consists of 20 spherical triangles that form pentagons. Dividing single frequency into more units forms hexagons. Frequencies: 1 2 3 4 GEODESIC DOME 1 Single frequency dome: 10 triangles forming pentagons 2 Single frequency dome of 10 spherical triangles 3 Two-frequency sphere 4 Two-frequency hemisphere dome 5 Four-frequency hemisphere dome 6 Football of 10 hexagons, 12 pentagons
  125. 125.  US pavilion Expo 67 Montreal  Architect: Buckminster Fuller & Shoji Sadao  The 250 feet diameter by 200 feet high dome roughly presents a three-quarter sphere, while geodesic domes before 1967 were hemispherical. The dome consists of steel pipes and 1,900 acrylic panels. To keep the indoor temperature acceptable, the design included mobile triangular panels that would move over the inner surface following the sun. Although brilliant on paper, this feature was too advanced for its time and never worked. Instead valves in the centre of acrylic panels enabled ventilation. EXAMPLE
  126. 126.  Climatron, Missouri Botanical Gardens, St Louis (1959)  Architect: Murphey & Mackey  Engineer: Paul Londe  The dome of 175 feet diameter and 70 feet height permits tall palm trees to tower above tropical streams, waterfalls and 1,200 species of exotic trees and plants.  Temperature ranges 64 to 74 degrees and average humidity is 85 percent. EXAMPLE
  127. 127. • Spruce Goose dome, Long Beach, USA • Architect: R. Duell and Associates • Engineer/builder: Temcor • This aluminium dome for Hugh’s Spruce Goose(at 415 ft diameter among the largest geodesic domes). The dome of 15 geodesic frequencies weighs < 3 psf. • The design had to provide a temporary opening for the plane of 320 ft wing-span to pass through. A Aluminium cover plate with silicone seal B Aluminium gusset plates, bolted to struts C Aluminium batten secure silicone gaskets D Triangular aluminium panels E Wide-flange aluminium struts F Stainless steel bolts EXAMPLE
  128. 128. HPR dome, Walla Walla, USA Architect: Environmental Concern, Inc. Engineer/builder: Temcor Aluminum dome of 206’ diameter and 42 ft depth (span/depth ratio 4.9), weighs less than 3 psf. EXAMPLE
  129. 129. HYPERBOLIC PARABOLOID  Formed by sweeping a convex parabola along a concave parabola or by sweeping a straight line over a straight path at one end and another straight path not parallel to the first. Structural behaviours  Depending on the shape of the shell relative to the curvature, theere will be different stresses.  Shell roofs, have compression stresses following the convex curvature and the tension stresses following concave curvate.
  130. 130. PROPERTIES  Hyperboloid structures are superior in stability towards outside forces compared to "straight" buildings, but have shapes often creating large amounts of unusable volume (low space efficiency) and therefore are more commonly used in purpose-driven structures, such as water towers (to support a large mass), cooling towers, and aesthetic features. Water tank hyperbolical concrete shell structure
  131. 131. MIAMI MARINE STADIUM  Preserving the Miami Marine Stadium is a cast-in-place concrete 100-meter long building with an eight-section hyperbolic paraboloid roof  It is 33-meter wide with a cantilever of 20 meter over the stands; one third of the structure is built on piers into the water.  Used for motorboat racing and various types of concerts on a floating stage.
  132. 132. CONCRETE SHELL  The material most suited for construction of shell structure is CONCRETE because it is a highly plastic material when first mixed with water that can take up any shape on centering or inside formwork.  Small sections or reinforcement bars can readily be bent to follow the curvature or shells.  Once cement has set and the concrete has hardened the R.C.C membrane or slab acts a strong, rigid shell which serves as both structure and covering to the building. RCC & STEEL STRUCTURE
  133. 133. TYPES AND FORMS Folded plates Barrel shells Domes Translation shell
  134. 134. CENTERING OF SHELL  Centering is the term used to describe the necessary temporary support on which the curved R.C.C. Shell structure is cast.  The centering of a barrel vault which is a part of a cylinder with same curvature along its length , is less complex.  The centering of concoid, dome and hyperboloid of revolution is more complex due to additional labour and wasteful cutting of materials to form support for shapes that are not of uniform linear curvature.
  135. 135. CONCRETE SHELL CONSTRUCTION  Shells may be cast in place, or pre-cast off site and moved into place and assembled. The strongest form of shell is the monolithic shell, which is cast as a single unit.  Geodesic domes may be constructed from concrete sections, or may be constructed of a lightweight foam with a layer of concrete applied over the top. The advantage of this method is that each section of the dome is small and easily handled. The layer of concrete applied to the outside bonds the dome into a semi-monolithic structure.  Monolithic domes are cast in one piece out of reinforced concrete and date back to the 1960s. It is cost-effective and durable structures, especially suitable for areas prone to natural disasters. Monolithic domes can be built as homes, office buildings, or for other purposes. Monolithic dome in Alaska
  136. 136.  Completed in 1963, the University of Illinois Assembly Hall, located in Champaign, Illinois was and is the first ever concrete-domed arena. The design of the new building, by Max Abramovitz, called for the construction of one of the world’s largest edge-supported structures.  The Seattle Kingdome was the world's first (and only) concrete-domed multi- purpose stadium. It was completed in 1976 and demolished in 2000. The Kingdome was constructed of triangular segments of reinforced concrete that were cast in place. Thick ribs provide additional support.
  137. 137. • Concrete shells are naturally strong structures, allowing wide areas to be spanned without the use of internal supports, giving an open, unobstructed interior. • The use of concrete as a building material reduces both materials cost and a construction cost, as concrete is relatively inexpensive and easily cast into compound curves. • The resulting structure may be immensely strong and safe; modern monolithic dome houses, for example, have resisted hurricanes and fires, and are widely considered to be strong enough to withstand even F5 tornadoes. • Very light form of construction, to span 30m shell thickness required is 60mm. • Dead load can be reduced economizing foundation and supporting system. • Aesthetically it looks good over other forms of construction. ADVANTAGES
  138. 138.  Since concrete is porous material, concrete domes often have issues with sealing. If not treated, rainwater can seep through the roof and leak into the interior of the building.  On the other hand, the seamless construction of concrete domes prevents air from escaping, and can lead to buildup of condensation on the inside of the shell. Shingling or sealants are common solutions to the problem of exterior moisture, and dehumidifiers or ventilation can address condensation.  Shuttering problem  Greater accuracy in formwork is required  Good labour and supervision is necessary  Rise of roof may be a disadvantage. DISADVANTAGES
  139. 139. The Market Hall in Leipzig, Germany (1929) by Franz Dischinger
  140. 140. Petroleum Coke Bulk Storage - Pittsburg, California OPAC Consulting Engineers
  141. 141. FOLDED PLATES Nikhita Khurana Pulkit Chawla Tanvi Yadav Dhruv Khurana
  142. 142. INTRODUCTION • FOLDED PLATES is one of the simplest shell structure. • They are more adaptable to smaller areas than curved surfaces which require multiple use of forms for maximum economy. • A folded plate may be formed for about the same cost as a horizontal slab and has much less steel and concrete for the same spans. • Folded plates are not adapted to as wide bay spacings as barrel vaults. SHELL STRUCTURE FOLDED PLATE STRUCTURE BAY WIDTH OF FOLDED PLATES BAY WIDTH OF BARREL VAULT
  143. 143. BEHAVIOUR  Each plate is assumed to act as a beam in its own plane, this assumption is justified when the ratio of the span "length“ of the plate to its height“ width“ is large enough. But when this ratio is small, the plate behaves as a deep beam. • When the folded plate is that with simple joint , which mean that no more than 2 elements are connected to the joint. • But when more than 2 elements are connected to the joint, it can be named as multiple joint. The width of any plate should not be larger than 0.25 its length to be considered to act as beam. • Actions of Folded plate due to loads : 1) SLAB ACTION : loads are transmitted to ridges by the bending of plates normal to their planes. 2) BEAM ACTION : Loads are transmitted through plates in their planes to diaphragms. RIDGE
  144. 144. COMPONENTS • The principle components in a folded plate structure are illustrated in the sketch below. They consist of, 1) the inclined plates, 2) edge plates which must be used to stiffen the wide plates, 3) stiffeners to carry the loads to the supports and to hold the plates in line, and 4) columns to support the structure in the air. • A strip across a folded plate is called a slab element because the plate is designed as a slab in that direction. • The span of the structure is the greater distance between columns and the bay width is the distance between similar structural units. • If several units were placed side by side, the edge plates should be omitted except for the first and last plate. • If the edge plate is not omitted on inside edges, the form should be called a two segment folded plate with a common edge plate. • The structure may have a simple span or multiple spans of varying length, or the folded plate may cantilever from the supports without a stiffener at the end. TAPERED FOLDED PLATES Inclined plates Edge plates Stiffeners Columns Span
  145. 145. THE PRINCIPLE OF FOLDING STRUCTURAL BEHAVIOUR OF FOLDING • The inner load transfer of a folding structure happens through the twisted plane, either through the structural condition of the plate (load perpendicular to the centre plane) or through the structural condition of the slab (load parallel to the plane). • At first, the external forces are transferred due to the structural condition of the plate to the shorter edge of one folding element. • There, the reaction as an axial force is divided between the adjacent elements which results in a strain of the structural condition of the slabs. This leads to the transmission of forces to the bearing.
  146. 146. FORMS OF FOLDED PLATE STRUCTURES• By using folded structures different spatial forms can be made. • The straight elements forming a folded construction can be of various shapes: rectangular, trapezoidal or triangular. • By combining these elements we get different forms resulting in a variety of shapes and remarkable architectural expression. • Folded structures in the plane are the structures in which all the highest points of the elements and all the elements of the lowest points of the folded structure belong to two parallel planes. • Frame folded structures represent constructional set in which the elements of each segment of the folds mutually occupy a frame spatial form. This type of folded structure is spatial organization of two or more folds in the plane. • Spatial folded structures are the type of a structure in which a spatial constructive set is formed by combining mutually the elements of a folded structure.
  147. 147. FORMS OF FOLDED PLATE STRUCTURES • The shape of folded structures affects the transmission of load and direction of relying of folded structures. Based on these parameters, folded plate systems are further classified into : 1. linear folded plate structure 2. radial folded plate structure 3. spatial folded plate structure LINEAR FOLDED PLATE STRUCTURE RADIAL FOLDED PLATE STRUCTURE SPATIAL FOLDED PLATE STRUCTURE • Combined folded constructions are carried out over the complex geometric basis, formed by the combination of simple geometric figures, rectangles and semicircles on one side or both sides. • This type of folded structure can be derived in the plane or as a frame (cylindrical) structure, and represents a combination of folded structure above the rectangular base and ½ of the radial construction. EXAMPLE OF A COMBINED FOLDED STRUCTURE FORMED BY A CYLINDRICAL FOLDED STRUCTURE AND HALF OF DOME STRUCTURE
  148. 148. TYPES OF FOLDED PLATE STRUCTURES  LONGITUDINAL/ PRISMATIC FOLDING • Longitudinal folding is characterized through uninterrupted and linked folding edges where parallel and skew up folds and down folds alternate. • Single-layered longitudinal folding corresponds in their load bearing structure to a linear load bearing system whereas a double-layered folding with different directions of their folds can create the structural condition of the plate.  SPOT OR FACET FOLDING • Also called spot or facet folding, requires that several folds intersect like a bunch in one single spot. This results in pyramidal folds with crystalline or facet-like planes. • Facet folding can either be based on a triangular shape or on a quadrangular shape. • A single or double-layered facet folding resembles the load bearing structure of a plate and can be compared to space frameworks SKETCH PYRAMIDAL FOLDING SKETCH LONGITUDINAL FOLDING
  149. 149. •Reinforced Cement Concrete •Steel Plate •Mixture of Concrete and lightweight terracotta tiles •Polymer mixture of concrete and fibreglass •Scored laminated timber sheets •Prestressed concrete folded plates •Extremely light with concrete thickness of 200mm •An existing hangar at Santa Cruz Airport, Mumbai (Bombay), India, has been extended to accommodate additional aircraft and engineering facilities. •Contains 8 folds •62 m long cantilever of the new folded-plate roof • Measure152 x 60 m in plan, and is symmetrically divided by a longitudinal expansion joint •The 152 m length consists of two cantilevered roofs, each 62.3 m long, and a central roof 27.4 m long over the maintenance building. •Highest point of roof is 32.3m above ground •The transverse section of the folded plate consists of eight 7.6 m wide modules, each having a corrugated plate arrangement, with horizontal top and bottom plates inclined at 45° between the webs.
  150. 150. EXAMPLE: THE CHURCH OF NOTRE DAME, THE CITY OF ROYAN •Walls can be designed and carried out as folded structures, since by folding we get a solid construction that can accept large vertical and horizontal impacts, which enables exceptional height of the wall fabric. •This type of folded structures, due to their geometry, provides an economical solution and the rational use of material when compared to the height of the building. •Walls made as folded structures can be materialized in reinforced concrete. •Facility constructed with this structure is the church of Notre Dame, the city of Royan, France, 1958, with the walls built in the form of folded in "V" shape of reinforced concrete. •Viable galleries, which have a constructive role of the diaphragm, are built on them
  151. 151. • since they are of concrete, such roofs have inherent resistance to fire, deterioration and to atmospheric corrosion. • They allow large spans to be achieved in structural concrete. This allows flexibility of planning and mobility beneath. • Where ground conditions require expensive piled foundations the reduced number of supporting columns can be an economic advantage. • The plates are required to be thicker than the shells, and there are more firms who will tackle constructing them without excessive prices, increasing competition and sometimes making the cost more competitive than for cylindrical shells.  DISADVANTAGES • Skilled labor is required in the construction of curved shuttering. • Since concrete is porous material, concrete domes often have issues with sealing. If not treated, rainwater can seep through the roof and leak into the interior of the building • Labor skilled in curved shuttering are very expensive • Skilled labor for folded plates are hard to find  ADVANTAGES •Storage buildings •Swimming pools •Gyms •Airports etc.  USES
  152. 152. APPLICATION • Folded structures have found the application in architectural buildings and engineering structures. • Based on the position in the architectural structure, this type of construction can be divided into: roof, floor and wall folded constructions. • The largest number of examples of folded structures are roof structures. • The need for acquiring the larger range and more cost effective structure led to the emergence of this type of structure. • The largest application of folded structures is in the formation of trapezoidal sheet. • This type of folded structure can absorb and receive the load without introducing additional structure. • Application of trapezoidal sheet, except as roofing, is in making the thermal insulation of roof and wall sandwich panels.
  153. 153. HIGH RISE BUILDINGS PRESENTED BY : •KARTIK KUMAR •PAYAL GUPTA •PRACHI ARORA •MEGHA KASHYAP •NEETU SHARMA •ARJUN •MOHIT GUPTA
  154. 154. INTRODUCTION AND DEFINITION High rise is defined differently by different bodies. Emporis standards- “A multi-story structure between 35- 100 meters tall, or a building of unknown height from 12-39 floors is termed as high rise. Building code of Hyderabad,India- A high-rise building is one with four floors or more, or one 15 meters or more in height. The International Conference on Fire Safety – "any structure where the height can have a serious impact on evacuation“ U.S., the National Fire Protection Association A high-rise as being higher than 75 feet (23 meters), or about 7 stories

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