shell structure (roofs) advanced construction material and techniques
- 1. SHELL ROOFS SUBMITTED BY - GRIMA(17072101214) HARLEEN(17072101236) ADVANCED CONSTRUCTION MATERIALSAND TECHNIQUES ARL-360
- 2. WHATARE SHELLS?? SHELLS Curved structures Capable of transmitting loads in more than two directions to supports The ideal thin shell must be capable of developing both tension and compression. SHELL STRUCTURES Keep their shape and support loads, even without a frame, or solid mass material inside Use a thin, carefully shaped, outer layer of material, to provide their strength and rigidity.
- 3. Curved Form: Shell roofs are characterized by their curved or domed shape, which can be created using various geometric forms such as parabolas, hyperbolas, ellipses, or catenaries. Single-Span Structure: They typically cover large, uninterrupted spaces without the need for internal supports, offering wide, open interiors. Load Distribution: Shell roofs distribute loads uniformly over their entire surface, minimizing stress concentrations and allowing for efficient use of materials. CHARACTERISTICS OF SHELLS
- 4. Construction Challenges: Building shell roofs often requires specialized engineering and construction techniques to achieve the desired form while ensuring structural integrity and safety. Natural Lighting and Ventilation: Depending on their design, shell roofs can incorporate openings or glazing to allow natural light and ventilation, enhancing interior comfort and energy efficiency. Structural Efficiency: Due to their inherent strength and load-bearing capacity, shell roofs require less material compared to traditional roof structures, resulting in cost savings and environmental benefits.
- 5. FUNDAMENTAL PRINCIPLES OF SHELL STRUCTURES CHOICE OF GEOMETRY A shell’s structural behaviour is derived directly from its form. This not only dictates the aesthetics, but the overall efficiency and behaviour under load of the structural system THICKNESS It has a thickness smaller as compared to other dimensions Deformations in these dimensions are not large as compared to thickness Its shape spreads forces throughout the whole structure Every part supports only a small part of the load, giving it its strength STRENGTH
- 6. Concrete Shell Structures -Often cast as monolithic dome or stressed ribbon bridge or saddle roof Lattice Shell Structures - Also called grid-shell structures Often in the form of a geodesic dome or a hyperboloid structure Membrane Structures Fabric structures and other tensile structures, cable domes, and pneumatic structures TYPESOFTHIN SHELL STRUCTURES THERE ARE MANY DIFFERENT WAYS TO CLASSIFY SHELL STRUCTURE BUT TWO WAYS ARE COMMON. THE MATERIAL WHICH THE SHELL IS MADE OF LIKE REINFORCED CONCRETE, PLYWOOD, STEEL BECAUSE EACH ONE HAVE DIFFERENT PROPERTIES THAT CAN DETERMINE THE SHAPE OF SHELL THE SHELL THICKNESS: SHELL CAN BE THICK OR THIN CLASSIFICATION OFSHELLS
- 7. CONCRETE SHELL STRUCTURES A thin shell concrete structure, is a structure composed of a relatively thin shell of concrete, usually with no interior columns or exterior buttresses. The shells are most commonly flat plates and domes, but may also take the form of ellipsoids or cylindrical sections, or some combination thereof.
- 8. DESIGN CONSIDERATIONS Structural Integrity: The primary consideration is ensuring that the shell roof can support its own weight as well as any imposed loads such as snow, wind, or equipment. Structural analysis is essential to determine the appropriate thickness, curvature, and material properties required for the shell to resist these loads. Geometry and Form: The shape and form of the shell roof not only impact its structural performance but also its architectural appearance. Designers must balance aesthetic considerations with structural efficiency to achieve an elegant and functional form. Factors such as span, curvature, and profile play a crucial role in defining the geometry of the shell. Material Selection: Choosing the right material is critical for the structural performance, durability, and aesthetic appeal of the shell roof. Common materials include reinforced concrete, steel, timber, or composite materials. Factors such as strength, durability, cost, and construction methods should be considered when selecting the material.
- 9. Construction Techniques: Construction of shell roofs often requires specialized formwork and construction techniques. Designers must consider factors such as formwork stability, concrete pouring sequence, and curing methods to ensure the quality and integrity of the structure. Prefabrication and modular construction techniques may also be employed to expedite the construction process. Maintenance and Durability: Designers should anticipate future maintenance requirements and design the shell roof to facilitate access for inspection, repair, and cleaning. Materials should be selected for their durability and resistance to environmental degradation. Proper detailing and construction practices can also contribute to the long-term durability of the structure. Waterproofing and Insulation: Shell roofs are susceptible to water infiltration, especially in areas with heavy rainfall or snowfall. Adequate waterproofing measures must be incorporated into the design to prevent water ingress and protect the underlying structure. Additionally, insulation may be required to improve energy efficiency and thermal comfort within the building.
- 10. SPAN RANGE SHELL STRUCTURE CONSTRUCTIONTECHNIQUE SHORT SPAN (0-10M) FOLDED PLATE FORMWORK AND CONCRETE POURING MEDIUM SPAN (10-20M) BARREL VAULT PRE CAST CONCRETE SEGMENTS LONG SPAN (20+M) GRID SHELL MODULAR CONSTRUCTION EXTRA LONG SPAN CABLE NET STRUCTURE TENSIONING CABLES AND ACHORS SHELL STRUCTURES AS PER SPAN
- 11. TYPES OF CONCRETE SHELL STRUCTURES • Shell structures are sometimes described as single or double curvature shells. • 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.
- 12. FEATURES SURFACE OF REVOLUTION SURFACE OF TRANSLATION Generated by rotating a curve around an axis Generated by translating a curve along a straight line Basic Shapes Cones, Domes, Ellipsoids roofs Barrel Vaults, Cylinders roofs Examples Conical roofs, Dome roofs, Ellipsoidal roofs Barrel vault roofs, Cylindrical roofs Structural Properties Typically have varying thickness along the surface Typically have uniform thickness along the surface Generation Method REVOLUTION TRANSLATION
- 13. Definition Surface where both principal curvatures are concave or convex. Surface where one principal curvature is concave while the other is convex. Structural Behavior Tends to collapse inward towards its center. Tends to curve outward, creating a saddle-like shape. Examples Dome, bowl shapes Shell-like structures, saddle shapes ASPECTS SYNCLASTIC DOUBLY CURVED ANTI-CLASTIC DOUBLY CURVED
- 14. Stability Relatively stable More prone to instability due to outward curvature Construction Challenges Requires precision in shaping and supporting to prevent collapse. May require specialized techniques to maintain structural integrity and prevent buckling. Applications Architectural domes, spherical structures Shell roofs, hyperbolic paraboloid roofs ASPECTS SYNCLASTIC DOUBLY CURVED ANTI-CLASTIC DOUBLY CURVED
- 15. 1.Design: First, architects and engineers work together to design the shape and dimensions of the shell roof. They consider factors such as load-bearing capacity, material strength, and aesthetic appeal. 2. Formwork: Once the design is finalized, formwork is created. Formwork is a temporary structure made from wood, steel, or other materials that act as a mold for the concrete or steel to be poured into. It helps shape the shell structure. 3. Reinforcement: If the shell roof is made of reinforced concrete, steel reinforcement bars, also known as rebars, are placed within the formwork. These rebars provide strength and durability to the structure. CONSTRUCTION OF SHELL ROOF
- 16. 4. Concrete Pouring: Next, concrete is poured into the formwork. It is carefully placed and compacted to ensure a strong and even distribution. The concrete may be mixed with additives to enhance its properties, such as increasing its strength or reducing its weight. 5. Curing: After the concrete is poured, it needs time to cure and harden. This process usually takes several days or weeks, during which the concrete gains strength and stability. 6. Formwork Removal: Once the concrete has fully cured, the formwork is removed. This reveals the final shape of the shell roof. The formwork can be reused for future construction projects. 7. Finishing Touches: Finally, any necessary finishing touches are made, such as applying a protective coating or adding insulation to the roof.
- 17. INNOVATION ANDTRENDS Advanced Material: Enhanced properties such as higher strength-to-weight ratios, increased durability, and improved sustainability. Carbon fiber composites, engineered timber, and bio-based materials are being explored
- 18. Biophilic Design: Incorporating natural elements into roof structures to improve well-being, such as living green roofs, natural lighting strategies, and materials inspired by nature. Digital Design and Fabrication: The integration of digital design tools, parametric modeling software, and robotic fabrication technologies is revolutionizing the design and construction of shell roofs
- 19. DESCRIPTION (Flourine based plastic) Engineered Timber (e.g., Cross-laminated timber) Sustainable and renewable material with high strength-to-weight ratio, suitable for long- span structures. ETFE (Ethylene Tetrafluoroethylene) Transparent, lightweight, and durable material used in inflatable structures, offering natural daylighting. High-strength lightweight material offering excellent structural properties and durability Carbon Fiber Reinforced Polymers (CFRP) NEW CONSTRUCTION MATERIAL
- 20. DESCRIPTION NEW CONSTRUCTION MATERIAL 3D Printed Concrete Transparent Concrete Graphene Allows for intricate and customized designs while reducing material waste and construction time Combines optical fibers and fine concrete to create translucent panels, offering unique aesthetic possibilities. Graphene is a single layer of carbon atoms arranged in a two-dimensional honeycomb lattice. properties, including unparalleled strength, electrical conductivity, and flexibility
- 21. DISADVANTAGES ADVANTAGES Used for long spans hence we get column free space Light weight Less rigid as compared to solid structures Economically viable Minimum reinforcement Simple Design More Strength Compared With Other Structures Attractive And Decorative Appearance Shell buckling is particularly nasty because shell structures are so efficient, almost no deflection occurs and then suddenly there is a total collapse. Complicated form work and cannot be reused Labour Cost is High in Shell Structure Tiny Cracks Or Scratches Cause The Whole Structure Weak Can Be Affected By Temperature Construction Can Be Slow And Difficult
- 22. Built: in 20th Century Location : Kalkaji, Delhi Designed by: Ar. Fariburz Sahba Geometry : a half open lotus flower,a float, surrounded by its leaves. The lotus has three sets of leaves or petals, all of which are made out of thin concrete shells. The outer most set of nine petal, called the 'entrance leaves' Open outwards and form the nine entrances all around the outer annular hall. LOTUS TEMPLE,NEWDELHI
- 23. ARCHITECTURAL DESIGN Inspiration: The Lotus Temple's design draws inspiration from the lotus flower, symbolizing purity, beauty, and spiritual significance in various cultures. Petals: The temple consists of 27 free-standing marble-clad "petals" arranged in clusters of three to form the lotus flower's distinctive shape. Symmetry: The design emphasizes symmetry, with each petal identical in size and shape, creating a harmonious and balanced aesthetic. Geometry: The structure embodies geometric principles, including radial symmetry and fractal geometry, enhancing its visual appeal and structural stability. Material: White marble, chosen for its elegance and durability, clads the exterior of the petals, reflecting light and accentuating the temple's ethereal beauty.
- 24. CONSTRUCTION TECHNIQUES Prefabricated Components: Many of the structural elements of the Lotus Temple were prefabricated off-site, including the concrete shells and steel components. These prefabricated elements were transported to the construction site and assembled according to the architectural plans. Cranes and Hoists: Cranes and hoists were used to lift and position the prefabricated components into place. These heavy-duty machinery helped to maneuver the large and intricate elements of the structure with precision. Formwork Installation: Formwork, typically made of wood, steel, or aluminum, was used to mold the concrete shells of the temple on-site. The formwork provided the necessary support and shape for pouring the concrete, allowing the construction team to create the curved and intricate design of the temple.
- 25. Prestressing: Once the concrete shells were in place, prestressing techniques were employed to reinforce the structure. High-strength steel tendons were inserted and tensioned within the concrete to counteract the forces of tension, enhancing the strength and stability of the temple. Detailed Assembly: Careful attention was paid to the precise assembly of the components to ensure structural integrity and aesthetic coherence. Skilled laborers and engineers worked together to align and connect the various elements of the temple according to the architectural plans. Seismic Considerations: special construction techniques were used to enhance the temple's against earthquakes. Which includes additional reinforcement and anchoring of structural components to withstand seismic forces.
- 26. BUILDING MATERIALS Concrete: Reinforced concrete is the primary material used for the construction of the Lotus Temple's structural elements, providing strength and durability to support its intricate design. Steel: High-strength steel is utilized for reinforcement within the concrete structure, enhancing its load- bearing capacity and resilience against forces such as wind and earthquakes. Marble: White marble clads the exterior surfaces of the Lotus Temple, imparting a pristine and elegant appearance while reflecting light and creating a luminous ambiance. Glass: Transparent and translucent glass is incorporated into the temple's design to allow natural light to penetrate the interior spaces, creating a serene and uplifting atmosphere for meditation and prayer. Wood: Wood may be used for interior finishes, furnishings, and decorative elements within the temple, adding warmth and texture to the architectural design.
- 27. CHALLENGES FACED DURING CONSTRUCTION Seismic Risks: The location of the Lotus Temple in a seismic zone necessitated careful consideration of seismic risks and the implementation of measures to enhance the temple's resilience against earthquakes. Designing and constructing a structure capable of withstanding seismic forces while preserving its architectural integrity was a key challenge. SOLUTIONS Prefabrication: Prefabrication techniques were utilized to fabricate the complex structural elements off-site, allowing for greater precision and efficiency in assembly. Prestressing: Prestressing methods were employed to reinforce the concrete structure, enhancing its strength and resilience against seismic forces. CONCLUSION: By employing these methods . The construction team was able to enhance the strength, durability, and resilience of the Lotus Temple's concrete structure, ensuring its long-term stability and integrity.
- 28. Built: in 1973 Location : Sydney, Australia Designed by: Ar. John Utzon Unique Roof Geometry: Each shell has its own unique geometry, contributing to the overall complexity and beauty of the building. . SYDNEYOPERAHOUSE ,AUSTRALIA Type of building; houses multiple performance venues, including the Concert Hall, Opera Theatre, Drama Theatre, and more.
- 29. CONSTRUCTION TECHNIQUES Segmental Construction: The shells of the Opera House were constructed using a technique known as segmental construction, where precast concrete segments were assembled to form the shell structures. This allowed for greater precision and control during construction. Precast Concrete Ribs: The ribs that support the shells were also precast off-site and transported to the construction site This helped to speed up the construction process and ensure uniformity in the structure. Formwork: Complex formwork systems were used to create the molds for casting the concrete segments and ribs. These formwork systems had to be carefully designed to accommodate the unique geometry of each shell. Floating Scaffolding: Due to the curved and irregular shape of the shells, traditional scaffolding methods were not feasible. Instead, floating scaffolding platforms were used, which could be adjusted to fit the contours of the shells
- 30. BUILDING MATERIALS Concrete: Concrete is the primary building material used in the construction of the Sydney Opera House. It was used for the shells, ribs, and other structural elements of the building. The concrete used was a high-strength mix to support the unique architectural design. Ceramic Tiles: The exterior of the shells is clad with glossy white ceramic tiles, which give the Opera House its iconic appearance. These tiles were specifically designed for the project and were chosen for their durability, weather resistance, and ability to reflect sunlight. Glass: Glass was used in windows, skylights, and other openings throughout the Opera House to provide natural lighting and views of the surrounding environment. It was also used in interior partitions and decorative features. Timber: Timber was used in the interior spaces of the Opera House for flooring, paneling, and decorative elements. It adds warmth and texture to the interior design while complementing the concrete and glass materials.
- 31. PROJECT YAS Marina, Abu Dhabi ,UAE completed in 2009 OVERVIEW The iconic glazed veil visually connects two buildings located on both sides of the racetrack. It has 11900 sqm. of glazing area . 5096 unique laminated glass panels and 31390 m of aluminium extrusions, which accentuate nightly with integrated LEDs capable of 16 million different colour variations. YAS MARINA HOTEL, ABU DHABI
- 32. Its structural system is a grid shell that consists of the triangulated mega structure and the qudrangular grid. The free flowing grid shell is structurally one piece without any expansion joints and is supported vertically by V- shaped columns The glass panels have a carefully selected coating and frit pattern that balances visual transparency with light responsive properties according to different local conditions STRUCTURE
- 33. Due its size and extreme temperature changes ,the grid shell must be able to slide under temperature movements. Therefore eight out of the ten supports are able to slide in one direction, with the other two acting as fixed supports. Wind loads are transferred to concrete hotel structure by horizontal struts. Installed with approximately 5000 custom designed light fixtures , the outside of the building can be remotely programmed with vibrant lighting and media sequences that illuminate the racetrack and give the development a dramtic brand image.