Degree Lecture Notes - Building construction 2 (part 1)

TENSILE STRUCTURE & FABRIC/ MEMBRANE STRUCTURE

A tensile structure is a construction of elements carrying only tension and no compression or bending However, most tensile structures are supported by some form of compression or bending elements, such as masts (as in The O2, formerly the Millennium Dome), compression rings or beams.

Tensile membrane structures are most often used as roofs as they can economically and attractively span large distances.

Tensile membrane structures are most often used as roofs as they can economically and attractively span large distances.

TENSILE & FABRIC/ MEMBRANE STRUCTURE Suspension tensile structures • Suspension bridges • Draped cables • Cable-stayed beams or trusses • Cable trusses • Straight tensioned cables Tensile Fabric / Membrane structures • Stretched & • Curve in 2 directions

* Note: directions indicated as internal stress; as reaction to external forces/ loading

External: Tension force

External: Compression force

Internal: Tensile stress

Internal: Compressive stress

http://www.arch.mcgill.ca/prof/sijpkes/arch374/winter2002/psyisun/howtensileworks.htm

A critical problem in the design of any cable roof structure is the dynamic effect of wind, which causes an undesirable fluttering of the roof.

There are only several fundamental ways to combat flutter.

• One is to simply increase the deal load on the roof.

• Another is to provide anchoring guy cables at periodic points to tie the structure to the ground.

• To use some sort of crossed cable on double-cable system.

https://youtu.be/AN4G3ulBmnM

http://cenews.com/article/9091/a-top-down-solution

* Note: directions indicated as internal stress; as reaction to external forces/ loading

* Note: directions indicated as internal stress; as reaction to external forces/ loading

DOUBLE-CABLE (STAY) STRUCTURE Overall Length: 13.5 km (8.4 mi) Length Over Water: 8.4 km (5.2 mi) Penang Island Viaduct & Approach: 1.5 km (0.93 mi) Prai Approach: 3.6 km (2.2 mi)

Height of Tower Above Water: 101.5 m Height of Bridge Above Water: 33 m Main Span: 225 m End Span: 107.5 m Other Span: 40 m Speed limit: 80 km/h Maximum Gradient: 3.0%

SUSPENSION BRIDGE

The steel cables have 300,000 kilometres (190,000 mi) of wire: each cable is 112 cm (44 in) in diameter and contains 36,830 strands of wire.

The Akashi-Kaikyo bridge has a total of 1,737 illumination lights: 1,084 for the main cables, 116 for the main towers, 405 for the girders and 132 for the anchorages.

In compression * Note: directions indicated as external forces/ loading http://www.technologystudent.com/forcmom/dkforce2.htm

COMPRESSION

TENSION

CABLE STAYED ROOF - BUILDING

PA Technology Facility, Princeton, NJ Richard Rogers

Stockley Park, London (architect:Foster and Partners)

COMPONENTS OF TENSILE STRUCTURE •BASE PLATE Connection to concrete foundation pillar •MAST SUPPORTED BALE RING / MEMBRANE PLATE Provide a link between the membrane and structural elements. Bale rings are used at the top of conical shapes. Membrane plates accept centenary cables and pin connection hardware.

•CABLE FABRIC/ MEMBRANE STRUCTURE: •MEMBRANE Forms the enclosure of the structure. Connections can be glued or heat welded.

CABLE

• Steel Cables : The high tensile strength of steel combined with the efficiency of simple tension, makes a steel cable the ideal structural element to span large distances. • Nylon and plastics are suitable only for temporary structures, spanning small distances.

•

Cables are a construction of wire strands, laid (i.e. twisted) helically around a core to form a tension member of symmetrical cross section.

Cables have a high strength-to-weight ratio as the wire strands are drawn to high strengths and laid to share tensile loads effectively.

Mr Roy made headlines when he pulled a 42 tonne 'toy train' two and a half metres using only his ponytail

http://www.halfen.com/en/780/products/tension-rod-system/detanrod-system/introduction/

Structure outside the building envelope, Inmos, Newport (architect : Richard Rogers Partnership)

FABRIC/ MEMBRANE STRUCTURE

Russian engineer Vladimir Shukhov was one of the first to develop practical tensile structures, shells and membranes.

Shukhov designed eight tensile structures and thin-shell structures exhibition pavilions for the Nizhny Novgorod Fair of 1896, covering the area of 27,000 square meters.

TYPES OF FABRIC STRUCTURES • FRAME SUPPORT • SADDLE ROOF • MAST SUPPORTED • ARCH SUPPORTED • COMBINATIONS

FRAME SUPPORT • Most common for single curvature roof supported by a series of linear frame support. • Linear frame support is not tensile structure type; but the fabric/ membrane is considered as a tensile stressed element

FRAME SUPPORT • Most common for single curvature roof supported by a series of linear frame support. • Linear frame support is not of tensile structure; but the fabric/ membrane is considered as a tensile stressed element

• SADDLE ROOF Four or more point system when the fabric is stretched between a set of alternating high and low points (incl. hyperbolic)

• MAST SUPPORTED Tent - like structures containing one or more peaks supported by poles (masts) or a compression ring that connects the fabric to the central support.

• ARCH SUPPORTED Curved compression members are used as the main supporting elements and cross arches are used for lateral stability.

http://temembrane.com/introduction-to-tensile-fabric-structure-design-concept/ http://creatise.in/masterbuilder/2013/09/04/analysis-design-and-construction-of-fabric-structures/

Grid Shell

Examples in Kuala Lumpur? Tensile fabric concept as everyday house whole items?

Kuala Lumpur Bird Park

ENVIRONMENTAL IMPACT

ADVANTAGES / DISADVANTAGES • Little to no rigidity

•

Longer life cycles of materials.

•

Materials can be re-used in form.

•

Most materials are completely

• Lightweight and flexible

recyclable.

• Loss of tension is dangerous for stability

•

Less impact on site.

• Environmentally sensitive

•

Less construction debris after

• High strength weight ratio

demolition.

• Skilled workers

(Fabric/ membrane as material)

http://structurflex.com/about/pvc-ptfe-and-etfe-fabric-types/ Tensile Fabric Architecture: Part One - Materials & Forms https://www.youtube.com/watch?v=f98QM_2Nje8 Tensile Fabric Architecture: Part Two – Benefits (4:29min) https://www.youtube.com/watch?v=6M2GRK3jyVE Tensile Fabric Architecture: Part Three – Practicalities (3:54min) https://www.youtube.com/watch?v=NsDc27PDLos

Tensile Fabric Architecture: Part Four – Process https://www.youtube.com/watch?v=NIEOaU0tvg0

Tensile Fabric Architecture and Design https://www.youtube.com/watch?v=xszVf7gwFRE

MEMBRANE / FABRIC Structural fabric  yarns  fibers.

There are a variety of ways to join fibers to create yarn and a number of ways to weave yarn into fabric.

MEMBRANE / FABRIC

• • •

PVC (Polyvinyl Chloride) coated polyester cloth PVDF (Polyvinyl DeneFlouride) coating PVF (Polyvinyl Flouride) [Tedlar] coated polyester

•

PTFE(Poly Tetra Fluoro Ethylene) [Teflon] coated fibreglass cloth

•

ETFE film or foil

•

Silicone coated fibreglass

•

Netting

MEMBRANE / FABRIC •PVC (Poly Vinyl Chloride) coated polyester cloth The fabric is translucent and the addition of white pigments increases its resistance to UV rays.

Additives like anti fungal treatment, UV reflector and absorber agents are used to enhance PVC properties.

For improving its durability, an extra coat of pigmented coating can be added.

Smooth and shiny coating facilitates to keep the fabric clean Polyvinyl DeneFlouride (PVDF) coating

PVF (Polyvinyl Flouride) [Tedlar] coated fabric

MEMBRANE / FABRIC (CONT’D) • PTFE(Poly Tetra Fluoro Ethylene) [Teflon] coated fiberglass cloth

PTFE is chemically inert but bleaches white when exposed to sunlight http://img.archiexpo.com/images_ae/photo-g/ptfe-architectural-fabric-fiberglass-gypsum-plaster-tensile-structures-58335-7389505.jpg It is unaffected by UV rays Has self cleaning properties making it virtually maintenance free (?)

Limited colors, but specific shades can be custom made

MEMBRANE / FABRIC (CONT’D) • ETFE ( Ethylene Tetrafluoroethylene ) film

• Double layer pillow, or • Triple layer pillow (Refer grid shell structure)

(ETFE) offers a creative and lightweight alternative to glass. It is a transparent extruded film, or foil, with similar light transmission to glass, but is just 1% of the weight.

MEMBRANE (cont’d) • Silicone coated fibreglass cloth – more brittle •Netting

http://www.precisioncoatingftb.com/fiberglass-fabrics/silicone-coated.html

Membrane Selections:

• Internal or external use • Extent of weather resistance (eg. Fabric vs netting) • Natural lighting requirement • Heat transmission factor/ Heat load (AC equipment) • Maintenance consideration (eg. cleaning, repair) • Strength of fabric; span of fabric • Life span (vs temporary structure)

• Cost

SUMMARY Structure and Architecture design • Forms • Expression of structure.

• Details.

Next Lecture …………. Shell Structure eg. Grid Shell

https://secure.ifai.com/fabarch/articles/0110_ce_connection.html http://theconstructor.org/structural-engg/cable-and-tension-structures-2/419/

http://www.birdair.com/projects

Tensile Fabric / Membrane Structure (recap) Tensile Fabric/ Membrane Structure with a thin, flexible surface (membrane) that carries loads primarily through tensile stresses; no compression or bending.

It has no flexural rigidity.

It will buckle very easily in compression, but performs well under tension supported by masts, rods and cables that keep the material in tension.

Tensile Membrane Structure Advantages

Disadvantages

• Extremely light weight.

• Poor thermal performance.

• Poor acoustic performance.

• Large span.

• Minimum amount of structure.

• The low weight of the materials makes construction easier and cheaper than standard designs.

Can be improved by using double skin construction with insulation introduced into the cavity.

Coating the outer surface with a reflective finish controls solar gain.

PNEUMATIC STRUCTURE

Pneumatic Structure Origin The word pneumatic is derived from the Greek word “pneuma�, meaning breath Pneumatic structure is any building that derives its structural integrity from the use of internal pressurized air to inflate a pliable material envelope i.e. ETFE film, frabric, membrane Pneumatic structures are considered as tensile systems: membrane (structure under tension) resists all loads in tension.

Membrane / Fabric Structure

Pneumatic Structure A i r- s u p p o r t e d S t r u c t u r e

A i r- i n f l a t e d S t r u c t u r e

• Consist of a single membrane filled with air which is maintained slightly above normal atmospheric pressure by a compressor.

• Double –skinned structures comprising of individual, inflated cells or tubes, behave more like traditional building elements such as beams and columns.

• Typically dome shaped, although a variety of forms exist.

• Only the space between the • Exterior loads acting towards the two membranes is pressurized and inside are resisted by the internal air not the internal, occupied space. pressure. The internal air pressure Loads are resisted by the internal is in return resisted in tension by pressure of the inflated element. the membrane

Pneumatic Structure There are two main types of pneumatic structures: 1. Air-supported structures 2. Air-inflated structures.

A i r- s u p p o r t e d S t r u c t u r e

• Consist of a single membrane filled with air which is maintained slightly above normal atmospheric pressure by a compressor.

• Typically dome shaped, although a variety of forms exist.

A i r- i n f l a t e d S t r u c t u r e

• Double –skinned structures comprising of individual, inflated cells or tubes, behave more like traditional building elements such as beams and columns.

• Only the space between the • Exterior loads acting towards the two membranes is pressurized and inside are resisted by the internal air not the internal, occupied space. pressure. The internal air pressure Loads are resisted by the internal is in return resisted in tension by pressure of the inflated element. the membrane

Pneumatic Structure Application The structure can be either wholly, partial, or roof-only air supported.

A fully air-supported structure can be intended to be a temporary or semi-temporary facility or permanent, whereas a structure with only an air-supported roof can be built as a permanent building.

Air-inflated membranes were first devised by Walter Bird in the late 1940s and were soon put to use as covers for swimming pools, temporary warehouses and exhibition buildings.

This type of structures are perhaps the most cost-effective type of building for its very long spans.

Air supported To maintain structural integrity, the structure must be pressurized such that the internal pressure equals or exceeds any external pressure being applied to the structure (i.e. wind pressure), by compressors or fans.

The structure does not have to be airtight to retain structural integrity— as long as the pressurization system that supplies internal pressure replaces any air leakage, the structure will remain stable.

Pneumatic Structure Membrane Material The materials used are similar to those used in tensile structures, namely synthetic fabrics such as fiberglass and polyester.

To prevent deterioration from moisture and ultraviolet radiation, these materials are coated with polymers such as PVC (PVC-coated polyester), Teflon (PTFE-coated fiberglass) or ETFE foil which is more appealing.

This ETFE foil is most commonly used nowadays compared to the other two.

It has a life span of 10-15 years, available in translucent or transparent film.

The latest type provides up to 95% light transmission, therefore, the use of lighting system inside the structure is not required during the daytime..

This material is non-combustible and does not absorb dirt. Easily washed away in heavy rain.

Depending on use and location, the structure may have inner linings made of lighter materials for insulation or acoustics.

Air-inflated Membrane Pillow Construction The membrane fabrics are permanently inflated using air pump as small pillows set into a metal frame.

Pillows can be formed in two or three layers to provide higher thermal insulation.

The supporting frames are set in a grid and are supported as required by the design.They provide support in the event collapse.

Its curved outer surface allows rainwater to run off. Proprietary systems have gutters incorporated in the fabric, secured between metal frames.

A very light wire not is often incorporated on the inner face to withstand very high snow loads.

Pneumatic Structure Advantages • Considerably lower initial cost than conventional buildings • Lower operating costs due to simplicity of design (wholly air-supported structures only) • Easy and quick to set up, dismantle, and relocate (wholly airsupported structures only) • Unobstructed open interior space, since there is no need for columns • Able to cover almost any project

Disadvantages • Continuous operation of fans to maintain pressure, often requiring redundancy or emergency power supply.

• Dome collapses when pressure lost or fabric compromised • Cannot reach the insulation values of hard-walled structures, increasing heating/cooling costs • Limited load-carrying capacity • Conventional buildings have longer lifespan

Air-supported Structure Tokyo Dome, Japan

Tokyo Dome's original nickname was "The Big Egg".

Its dome-shaped roof is an air-supported structure,a exible membrane held up by slightly pressurizing the inside of the stadium.

SHELL CONSTRUCTION

Skeletal Construction

Shell Construction

Solid Construction

Relies on vertical and horizontal members

Members are united as one homogeneous entity to form the structure and spaces

Relies on homogeneous mass

Overview Skeletal Construction

Solid Construction

Shell Construction

Relies on vertical and horizontal members

Relies on homogeneous mass

Members are united as one homogeneous entity to form the structure and spaces

Keep their shape and support loads, even without a frame, or solid mass material inside. Use a relatively thin, carefully shaped, outer layer of material, to provide their strength and rigidity. Spread forces throughout whole structure (every part of structure supports only a small part of the load). However, a tiny weakness or imperfection in parts can cause the whole structure to fail.

Members are united as one homogeneous entity to form structure and space

JFK Airport NY by Eero Saarinen [1962]

Shell House,Nagano,Japan,by Kotaro Ide

Background...

Commonly used as roof structure, with the availability of reinforced concrete to create more spacious building.

The oldest known concrete shell, the Pantheon in Rome, was completed about AD 125, and is still standing.

It has a massive concrete dome of 43m in diameter.

The coffers for the concrete dome were poured in molds, probably on the temporary scaffolding.

The oculus admits the only light.

Largest UNREINFORCED concrete roof and oldest concrete roof in Rome.

The Seattle Kingdome was the world’s ďŹ rst (and only) concretedomed multi-purpose stadium. It was completed in 1976 and demolished in 2000.

• Modern thin concrete shells, began to appear in the 1920s; made from thin steel reinforced concrete.

• Shells may be cast in place or pre-cast off site and moved into place and assembled.

KresgeAuditorium Massachusetts Institute ofTechnology

• The strongest form of shell is the monolithic shell, cast as a single unit.

• The most common monolithic form is the dome.

• A monolithic dome is a structure cast in one piece over a form, usually of concrete or similar structural material.

Jena Planetarium

Definition of Shell Structure A hollow structure in the form of a thin, curved slab or plate whose thickness is small compared with its other dimensions and with its radius of curvature.

Any frame work or exterior structure which is regarded as not completed or filled in.

Dictionary of architecture & construction, 2nd edition, by Cyril M. Harris, 1993

A type of structure that obtains its strength from a thin, carefully shaped outer layer of material and that requires no internal frame.

The Sage Gateshead,Gateshead,England,UK by Sir Norman Foster

Principle 1. Continuity • Uninterrupted connection or union.

2. Curvature • A bend that may be present at the particular body structure.

• The rate of change (at a point) of the angle between the curve and a tangent to the curve.

Fan-shell Beach House,Pebble Beach,California

Three types of spatial curvature:

• Invert • Indefinite curvature • Outvert

Shell Structure • Man-made shell structures used in various branches of engineering.

• There are many interesting aspects of the use of shells in engineering: the structural aspect.

• Requires specialized design, construction and material knowledge in order to enable a meaningful and successful collaboration between architects, engineers and manufacturers.

Concrete Shell Structure Advantages

Disadvantages

• The curved shapes often used

• Since concrete is a porous

•

• • • •

for concrete shells are naturally strong structures.

Wide areas can be spanned without the use of internal supports.

An open, unobstructed interior.

Concrete as a building material reduces both material cost and construction cost.

Concrete is easily cast into compound curves.

The resulting structure may be immensely strong and safe; modern monolithic dome houses have resisted hurricanes and fires, strong enough to . withstand even F5 tornadoes

material, concrete domes often have issues with sealing. If not properly treated, rainwater can seep through the roof and leak into the interior.

• The seamless construction of concrete domes prevents air from escaping, 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 dehumidifier can address condensation.

Shapes of Shell Structure • Barrel Vault Shells • Short Shell • Intersection Shells

• Domes • Translation Domes • Hyperbolic Paraboloid

• Combination of shells

Single or Double Curvature Shells

Surface of Revolution

Barrel Vault Shells • Known from Ancient Egypt, were used extensively in Roman architecture.

• Also known as a tunnel vault or a wagon vault.

• Formed by the extrusion of a single curve (or pair of curve in the case of

pointed barrel vault).

• The vector of pressure result in a downward force while the lower portions of the arches realize a lateral force pushing outwards. The sides are normally anchored or buttressed to very heavy building elements.

• More elegant method is to build two or more vaults parallel to each other; the forces of their outward thrusts will thus negate each other.

• The third and most elegant mechanism to resist the lateral thrust was to create an intersection of two barrel vaults at right angles, thus forming a groin vault (intersection shells).

• More elegant method is to build two or more vaults parallel to each other; the forces of their outward thrusts will thus negate each other. • The third and most elegant mechanism to resist the lateral thrust was to create an intersection of two barrel vaults at right angles, thus forming a groin vault (intersection shells).

Cylindrical Barrel Vault Structure

• Can span up to 150 feet with a minimum of material. • Can be formed to reduce stresses and thicknesses in the transverse direction.

Short Shells • Relatively short compared to radius.

• The element of the base of the cylinder to pick up the arch load.

• The arches or rigid frame to pick up the entire ensemble.

The Short Shell carries loads in two ways: 1. As an arch carries load to the lower elements.

2. As a curved beam to the arches.

The thickness of the shell can be quite thin due to these properties.

Office Building by Milo Ketchum

Short Shell Spaceport America Fire Station, Las Cruces, NM, USA

Intersection Shells • The surfaces that produce the shell appear to meet at an intersection.

• Any basic types may be used in this manners but the barrel vault shell is the most familiar and useful.

Umbrella Shell • The interior rib created by the intersection of the shell elements.

• The exterior rib supporting the shell, particularly in the exterior corners.

• The load is transferred down through the central column.

Intersection Shell St. Louis International Airport

Domes • One of the earliest shell structure that invested.

• A spherical surface structure having a circular plan.

• The internal stresses are tension and compression and are staticaly

determined if the proper edge conditions are fullfilled.

• A ring is required at the base of the dome to contain the forces.

• The ring stresses are compression.

• Dome technology of building monolithic concrete dome by spraying concrete to the inside of a pressurized dome shaped fabric air form, 1970.

Translation Domes • • • •

Dome set on four arches.

The shape is different from a spherical dome.

Generated by a vertical sliding along another vertical curve.

All vertical slices have the same radius.

The stresses in a translation shell: • Much like a dome at the top • Tension forces are offset by compression in the arch.

• High tension forces in the corner.

Hyperbolic Paraboloid • Thousands of possible shapes for hypars.

• The surfaces are made by sliding a line over two other lines that are at varying angles.

• This surface can be constructed with straight boards, with a slight twist depending on their width, which also known as warped surfaces.

The hypars carries loads in two directions: 1. The diagonal element that sags is in tension.

2. The arch element is in compression.

In whatever directions, the forces must be picked up by the side ribs and delivered to the supports.

Hyperbolic Paraboloid Structure St Dominic's ATHY 02

Curved Surfaces 1. Thick Concrete Shell Heavy mass that transfers both compressive and tensile loads.

2. Thin Concrete Shell Has no bending moment and perform well in tension and compression.

3. Lattice & Membranes A shell that has no flexural rigidity and buckle in compression but perform well under tension.

4. Air Inflated Structure Supported by pressurized air inflated building elements to carry loads in a traditional manner.

Concrete Shell Structure Advantages

Disadvantages

• The curved shapes often used

• Since concrete is a porous

• • •

• •

for concrete shells are naturally strong structures.

Wide areas can be spanned without the use of internal supports.

An open, unobstructed interior.

Concrete as a building material reduces both material cost and construction cost.

Concrete is easily cast into compound curves.

The resulting structure may be immensely strong and safe; modern monolithic dome houses have resisted hurricanes and fires, strong enough to withstand even F5 tornadoes.

material, concrete domes often have issues with sealing. If not properly treated, rainwater can seep through the roof and leak into the interior.

• The seamless construction of concrete domes prevents air from escaping, 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 dehumidifier can address condensation.

Concrete Shell Structure Sydney Opera House, Sydney,Australia

The sails (roof) are made of reinforced concrete and reinforcing ribs to give added stiffness.

Concrete Shell Structure Sydney Opera House, Sydney,Australia

Concrete Shell Structure Sydney Opera House, Sydney,Australia

Concrete Shell Structure Sydney Opera House, Sydney,Australia

Concrete Shell Structure Trans World Airlines Flight Center, JFK Airport, New York

The structure consists of a shell of reinforced concrete with four segments that extend outward from a centra point.The concrete“wings” then unfold on either side of exterior,preparing for flight.Within the concrete,th structure is reinforced with a web of steel

Thin Concrete Shell Structure (Monolithic Dome) Utah Migrant Head Start Center, US Greek mono- and -lithic,meaning "one stone".

A structure cast in a one-piece form.

Forms made using air pressure supported fabric.

Concrete Shell Structure (Saddle Roof) Scotiabank Saddledome, indoor arena of Calgary,Alberta, Canada

Saddle roof is one which follows a convex curve about one axis and a concave curve about the other.

Contains at least one saddle point World record holder for the longest spanning hyperbolic paraboloid concrete shell.

Concrete Shell Structure Kresge Auditorium, Massachusetts I/8 of a sphere rising to a height of 50 feet & sliced away by vertical glass wall.

The thin-shell structure comes to earth on only 3 points.

1200 tons weight of shell roof made from composite concrete.

Concrete Shell Structure Saint Louis Abbey, Missouri

Consists of two sets of thin concrete parabolic shells on two levels, set in twenty identical bays tapering toward the center of the circular Above the shell is a 32-foot-high bell tower of concr The ribs together form a cage acting as a dome,40-feet-high inside a feet in diameter.

Concrete Shell Structure Lotus Temple, New Delhi, India

The petals,constructed of reinforced white concrete cast in place,are clad in white marble panel Nine arches provide the main support for the superstructure ring the central hall.

Lattice Shell Structure Also known as gridshell structure which derives its strength from its double curvature (in the same way that a fabric structure derives strength from double curvature), but is constructed of a grid or lattice.

The grid can be made of any . material, but is most often wood (similar to garden trellis), steel or similar material overlapped or overlaid in a regular, usually crisscross pattern.

Often in the form of a geodesic dome or a hyperboloid structure

Geodesic Domes • A spherical or partial-spherical structure based on a network of struts

arranged on great circles (geodesics) lying approximately on the surface of a sphere.

• The geodesics intersect to form triangular elements that have local triangular rigidity and also distribute the stress across the structure.

Advantages • Strong, getting stronger as they get larger.

• The basic structure can be erected very quickly from lightweight pieces by a small screw.

• The structure is Aerodynamic, withstands considerable wind loads.

Disadvantages • Numeruos drawbacks and problems as a housing system.

• The shape of a dome house makes it difficult to conform to code requirements for placement of service pipes.

Dome Structure The Montreal Biosphere, World Fair 1967

Lattice Shell Structure Savill Building, England The roof is the dominant feature of the building, over 90m in length and up to 25m wide.

The building has a 'three-domed' sinusoidal shaped gridshell roof of two layers of interlocking larch laths (50x80mm) on a one meter square grid, supported on steel quadropods and a steel tubular ring-beam.

Lattice Shell Structure Multihalle, Mannheim, Germany

Large span timber gridshells were constructed by initially laying out the main la members at in a regular square or rectangular lattice and subsequentl deforming this into the desired doubly curved form..

Lattice Shell Structure

Metropol Parasol, Seville, Spain

World’s largest wooden structure.

Series of interweaving wafe-like panels that architecturally form canopies.

Hyperbolic Paraboloid Structure The band shell on Raspberry Island

National Centre for PerformingArt,Beijing,with 200,000 sqm dome made of glass and titamium

McDonald’s Restaurant and petrol station,Batumi,Georgia,with thin faceted glass shell

Silk Leaf Stadium,Tokyo,with shell-like roof topped by retractable photo-voltaic glass elements

TheYas Hotel, Abu Dhabi,using 5800 pivoting diamond-shaped glass panels

Folded Plate Structure

Folded Plate Structure The simplest shell structure.

Folded plate structures consist of interconnected at some dihedral angle.

flat components, or plates, that are

Structures composed of rectangular plates are said to be prismatic.

Folded plates carry bending as well as tension, compression and shear forces.

Considered as a beam in the longitudinal direction.

Folding acting as support.

Folded Plate Structure

Folded Plate Structure The free edges have to be stiffened in some way.

A folded plate can be constructed with less steel and concrete compared to horizontal spanned slab. However, it is still thicker than for a barrel vault.

It can be made into folded plate dome, multi facet dome, faceted shell, hyperbolic shell, umbrella shell, short shell, intersection shell or even a combination of shells.

Folded Plate Structure Many more shapes

Folded Plate Structure Evolution of folded plates structure

Recap Skeletal Construction

Shell Construction

Solid Construction

Relies on vertical and horizontal members

Members are united as one homogeneous entity to form the structure and spaces

Relies on homogeneous mass

Recap Skeletal Construction

Shell Construction

Solid Construction

Relies on vertical and horizontal members

Members are united as one homogeneous entity to form the structure and spaces

Relies on homogeneous mass

Surface Structure Types of Surface Structure 1. Curved Surfaces • Concrete Shell (Solid) Structure • Lattice / Grid Shell Structure • Pneumatic (Membrane) Structure SURFACE STRUCTURE

2. Folded Plates

TEN SILE STRUCTURE FABRIC STRUCTURE

SHELL STRUCTURE

FOLDED PLATES

LATTICE SHELL

GEODESIC DOME

PNEUMATIC STRUCTURE

AIR SUPPORTED

TENSILE FABRIC MEMBRANE

AIR INFLATED

SUSPENSION STRUCTURE

STRUCTURAL FUNDAMENTAL (THE FIRST THING THAT ANY BUILDING HAS TO DO IS TO STAND UP)

WHAT IS A STRUCTURE ?

A STRUCTURE IN A BUILDING ACTS AS :• DEVICE FOR CHANNELING LOADS FROM THE BUILDING TO THE GROUND

STRUCTURE FORCES LOAD

•TO UNDERSTAND THE BASIC PRINCIPLES OF STRUCTURE I.E LOADING, FORCES TO BE ABLE TO BUILD BETTER STRUCTURES •ALL STRUCTURES MUST WITHSTAND LOAD AND FORCES OR THEY WILL FALL APART

FORCES

WHY STRUCTURE ?

MASS/ BUILDING

BASIC PRINCIPLES STRUCTURES

FORCES

OF

STRUCTURAL DESIGN CRITERIA A STRUCTURAL SYSTEM IS DESIGNED ACCORDING TO THE FOLLOWING CRITERIA:• FUNCTION • What is this thing supposed to do?

• What does it support?

• How well must a structure perform its functions?

• AESTHETICS • As a Designers the incorporation of the structure into the design has to be aesthetically pleasing • SAFETY •whether the structure is safe. Normally, structures are designed with safety factor that allows the structure to withstand much larger loads than it would normally need to carry.

• COST • Bigger and stronger structure usually is more expensive . Thus a good structure design would be cost efficient with reasonable margin of safety.

• MATERIAL • properties or characteristics of the materials must match the purpose of the structure. Different materials give different structural properties

PRIMARY CLASSIFICATION | GEOMETRY IN TERMS OF BASIC GEOMETRY, THE STRUCTURAL FORMS CAN GENERALLY BE CLASSIFIED AS EITHER • LINE-FORMING ELEMENTS • LINE-FORMING ELEMENTS CAN BE FURTHER DISTINGUISHED AS STRAIGHT OR CURVED. LINE

SURFACE

• SURFACE-FORMING ELEMENTS • ARE EITHER PLANAR OR CURVE. • CURVED-SURFACE ELEMENTS CAN BE EITHER SINGLE OR DOUBLE CURVATURE

PLANAR

CURVE

PRIMARY CLASSIFICATION | RIGIDITY CHARACTERISTICS OF THE STRUCTURAL ELEMENT • RIGIDITY • WHETER THE ELEMENT IS RIGID OR FLEXIBLE • RIGID ELEMENTS • Example: TYPICAL BEAMS DO NOT UNDERGO SHAPE CHANGES UNDER THE ACTION OF A LOAD OR CHANGING LOADS. USUALLY BENT OR BOWED TO A SMALL DEGREE

BY THE ACTION OF THE LOAD

RIGID STRUCTURE

• FLEXIBLE ELEMENTS • CABLES IN WHICH THE ELEMENT ASSUMES ONE SHAPE UNDER ONE LOADING CONDITION AND CHANGES SHAPE DRASTICALLY WHEN THE NATURE OF THE LOADING CHANGES FLEXIBLE STRUCTURE

LINE-FORMING ELEMENTS AND SURFACE-FORMING ELEMENTS. RIGIDITY RIGID STRUCTURES • R.C STRUCTURES • STEEL STRUCTURES

NON - RIGID STRUCTURES • TENSILE STRUCTURES

ELEMENTS

TYPICAL ASSEMBLIES

PRIMARY CLASSIFICATION | ONE WAY AND TWO WAY SYSTEMS • DISTINGUISED ACCORDING TO THE SPATIAL ORGANIZATION OF THE SYSTEM OF SUPPORT USED AND THE RELATION OF THE STRUCTURE TO THE POINTS OF SUPPORT AVAILABLE • ONE WAY SYSTEM – POINT /CONCENTRATED LOAD •DIRECTION OF THE LOAD-TRANSFER MECHANISM OF THE STRUCTURE FOR CHANNELING LOADS TO THE GROUND ACTS IN ONE DIRECTION ONLY. • TWO-WAY SYSTEM – UNIFORM DISTRIBUTED LOAD • DIRECTION OF THE LOAD-TRASNSFER MECHANISM IS MORE COMPLEX BUT ALWAYS INVOLVES AT LEAST TWO DIRECTIONS

ONE WAY AND TWO WAY SYSTEM/ RIGID AND FLEXIBLE ELEMENT

PRIMARY CLASSIFICATION | MATERIALS COMMON CLASSIFICATION APPROACH TO STRUCTURE IS THE TYPE OF MATERIAL USED (e.g, WOOD, STEEL OR REINFORCE CONCRETE STRUCTURE) THERE IS A CLOSE RELATIONSHIP BETWEEN THE NATURE OF THE DEFORMATIONS INDUCED IN A STRUCTURE BY THE ACTION OF EXTERNAL LOADING AND THE MATERIAL AND METHOD OF CONSTRUCTION THAT IS APPROPRIATE FOR USE IN THE STRUCTURE.

CONCRETE WILL CRACK WHEN SUBJECTED TO FORCES THAT TEND TO ELONGATE THE MATERIAL

STEEL CAN BE USED VIRTUALLY FOR ALL CONDITIONS

REINFORCED CONCRETE WITH STEEL, CAN BE USED IN SITUATION WHERE ELONGATING FORCE ARE PRESENT

TYPES OF STRUCTURE MASS

FRAME

Solid Structure

Skeletal structure

SHELL Surface Structure

TYPES OF STRUCTURE MASS Mass Structures are solid structures which rely on their own weight to resist loads.

A single brick is a mass structure but so is a large dam.

A mass structure can be made by forming similar materials into a particular shape or design.

TYPES OF STRUCTURE FRAME Frame structures also known as skeletal structure supports the weight of the roof and covering materials.

Some frame structures are simple and consist only of a frame. Examples: ladders Some frame structures are more complex with added parts.

Examples: bicycles, bridges crane and oil rig Frame structures are made from many small parts called members and joined together to make a whole Structure.

TYPES OF STRUCTURE SHELL Shell structures are made or assembled to make one piece.

Shell Structures are objects that use a thin, carefully shaped outer layer of material to provide their strength and rigidity.

Requires no internal frame.

Example: igloo, egg.

Most shell structures are made from thin sheet material (which makes them light) and most have ridges or curves moulded into them (to make them strong).

MASS . FORCES . LOADS . STRESS

MASS The mass of an object is the measurement of the amount of matter in the object.

Mass is generally measured in grams or kilograms A Balance is the most common type of measuring instrument for mass.

Mass is a very useful property to measure because it stays the same no matter where an object is located.

Example:

FORCES Forces are stresses such as pushes or pulls A standard unit of force is called a Newton (N).

Example: 1 N is a small force, just enough to stretch a thin rubber band Gravitational Force is the force applied by gravity on an object; measured in Newton(N). This is the scientific term for the everyday term “weight�

Example: 1Kg = 10N

External Forces: Are stresses that act on a structure from outside it. E.g. kicking a soccer ball Internal Forces: Are stresses put on the materials that make up a structure. Internal forces are the result of external forces. Internal stresses can change the shape of a structure.

This change of shape is called deformation.

Force Diagram

TYPES OF INTERNAL FORCES TENSION

•Is the name given to a force which tries to pull something apart. •A structural member in tension is called a tie. A Tie resists tensile stress.

Tensile strength = measures the largest tension force the material can stand before breaking.

TYPES OF INTERNAL FORCES COMPRESSION

•Is the name given to a force which tries to squash something together(which shortens it). • A structural member in compression is called a strut. A strut resists compressive stress.

Compressive Strength: Measures the largest compression force the material can stand before losing its shape or breaking into pieces.

TYPES OF INTERNAL FORCES TORSION

• Is the name given to a turning or a twisting force.

Torsion Strength: Measures the largest torsion force the material can stand and still regain its original shape.

TYPES OF INTERNAL FORCES SHEAR

A shear force is created where two opposite forces try to cut tear or rip something in two.

Shear Strength: Measures the largest shear force the material can stand before breaking.

TYPES OF INTERNAL FORCES BENDING

•A structure which is subjected to bending is being stretched and squashed at the same time.

•a combination of tension and compression forces.

•It is a force that cause bending deformation

EXTERNAL FORCES - LOADS STATIC LOAD

Concentrated

forces caused by the weight of the structure and anything which is permanently attached to it. (dead load)

Uniform

DYNAMIC LOAD

caused by things such as wind, waves, people, and vehicles. Dynamic forces are usually much greater than static forces and are very difficult to predict, load is a changing, or nonpermanent force These are the most common reason for structural failures.

These loads are applied on a small area on the panel surface.

These loads are applied over the entire surface of the panel. A file cabinet is a typical example.

Rolling

These loads are applied by wheeled object carrying loads across the floor. These loads are defined by wheel size and hardness, weight of object and number of passes.

Impact

These loads occur when loads are accidentally dropped on the floor Impact loads are defined by weight, impact surface area and distance dropped.

TYPE OF LOADS In structural analysis three kinds of loads are generally used:

Concentrated loads that are single forces acting over a relatively small area, for example vehicle wheel loads, column loads, or the force exerted by a beam on another perpendicular beam.

Line loads that act along a line, for example :the weight of a partition resting on a floor, calculated in units of force per unit length.

Distributed (or surface) loads that act over a surface area. Most loads are distributed or are treated as such, for example wind or soil pressure, and the weight of floors and roofing materials

LOADS | CATEGORIES DEAD LOAD

A permanent force acting on a structure. This includes the weight of the structure itself.

Over time, this gravitational force can cause the structure to sag, tilt, or pull apart as the ground beneath it shifts or compresses under the load.

Dead loads (DL) are essentially constant during the life of the structure and normally consist of the weight of the structural elements.

LOADS | CATEGORIES DEAD LOAD Dead load on a structure is the result of the weight of the permanent components such as beams, floor slabs, columns and walls.

These components will produce the same constant 'dead' load during the lifespan of the building.

LOADS | CATEGORIES

SNOW LOAD The shape of the roof also plays an important part in the magnitude of the snow load. The steeper the pitch, the smaller the load. The snow falling on a flat roof will continue to build up and the load will continue to increase, but on a pitched roof a point is reached when the snow will slide off.

LOADS | CATEGORIES LIVE LOAD The weight of occupants, snow and vehicles, and the forces induced by wind or earthquakes are examples of live loads.

All the movable objects/ nonpermanent objects in a building such as people, desks, cupboards and filing cabinets produce an imposed load on the structure.

This loading may come and go with the result that its intensity will vary considerably. At one moment a room may be empty, yet at another packed with people. Imagine the `extra' live load at a lively party!

LOADS | CATEGORIES WIND LOAD Wind has become a very important load in recent years due to the extensive use of lighter materials, height of building and more efficient building techniques.

A building built with heavy masonry may not be affected by the wind load, but the structural design of a modern steel clad industrial building is dominated by the wind load which will affect its strength, stability and serviceability.

Wind Tunnel Testing for high rise buildings

LOADS | CATEGORIES WIND LOAD The wind acts both on the main structure and on the individual cladding units.

The structure has to be braced to resist the horizontal load and anchored to the ground to prevent the whole building from being blown away.

If the dead weight of the building is not sufficient to hold it down. The cladding has to be securely fixed to prevent the wind from ripping it away from the structure.

MAIN STRUCTURE MAIN PARTS OF A STRUCTURE Load-bearing structural members support or transfer loads on the structure while remaining in equilibrium with each other Joints Places where members are connected to other members

MAIN STRUCTURE Horizontal members Direct support for live loads

Vertical members (pillars) High-strength columns that support horizontal members (Piers are short columns)

MAIN STRUCTURE HORIZONTAL MEMBERS(BEAM) Horizontal structural member supported at two or more points Support weight on longitudinal axis Designed to sustain loads perpendicular to its length

MAIN STRUCTURE GIRDER A smaller beam which supports other beams.

Also a horizontal member

The Crystal is built as an extension of the existing Nykredit premises in Copenhagen, Denmark. Designed by Schmidt Hammer Lassen Architects

MAIN STRUCTURE VERTICAL MEMBER (COLUMN) A support member that is under compressive force

' I -.. , ' "' '-V j

...

"Tote" by Serle Architects in Mumbai, India which consist of a banquet hall, restaurant and bar.

MAIN STRUCTURE CANTILEVERED STRUCTURE A projecting beam or slab supported at one end

Torreaguera Atresados House Designed by: Xpiral Location: Murcia, Spain

MAIN STRUCTURE CANTILEVERED STRUCTURE Beams fixed at one end are known as cantilevered

Balancing Barn Designed by: MVRDV Studio Makkink & Bey

FORCES +STRUCTURAL FAILURE In order for a structural system to perform the structure must resist forces.

However, external forces can cause internal forces in the structure.

These internal forces can cause the following types of damage: Shear Weight of building causes soil to shear and the building to collapse

Torsion Twisting can lead structures to break apart or become tangled

Compression Buckling is caused by compression

FORCES +STRUCTURAL FAILURE WIND LOAD

These forces (live loads, dead loads and wind loads) acting on buildings can cause walls to deform (known as 'racking') and/or increase the tendency to slide.

STRUCTURAL FAILURE Structures fail in many ways but can be divided into two categories: STABILITY FAILURES usually relate to structural systems STRENGTH FAILURES •relate to the members comprising a structure • Forces acting on structures can cause • them to fail to perform their function.

•Failure can occur if the force is too strong for the structure's design or if the force is acting on a vulnerable part of the structure A structure needs strength and stiffness to avoid failure.

STRUCTURAL FAILURE-R.C COLUMN COLUMN FAILURE MODE Column behavior is a function of many factors such as: Column Length: Shorter columns have larger load capacity; as the length of the column increases the column will buckle under a smaller load.

Column Stiffness: A column made of stiff material will buckle less than a column with a lower stiffness.

STRUCTURAL FAILURE-R.C COLUMN COLUMN LENGTH A long column which has a relatively large length when compared to its cross sectional dimensions, will fail by buckling or bending.

As the load on the column is increased there will be a critical limit beyond which the column will fail by buckling.

Therefore, the long column failure is a stability problem and not a strength problem

STRONG AXIS BUCKLING

WEAK AXIS BUCKLING

STRUCTURAL FAILURE-R.C COLUMN COLUMN LENGTH A short column with a relatively short length when compared to its cross sectional dimensions, will fail by crushing.

As the load is increased, the column will reach a critical limit beyond which it can not accept any more loading and will break or crush.

Crushing of a column is dependent on the strength of the material it is composed of as well as its cross sectional size.

Short column failure is a strength problem.

STRUCTURAL FAILURE-R.C BEAM BENDING

Bending is probably the most common type of failure. It is illustrated by the top figure in which the "fibers" along the bottom face of the beam are torn and those along the top face of the beam are crushed.

The top surface shortened due to compression, and the bottom surface is elongated due to tension - both as a result of bending moment

STRUCTURAL FAILURE-R.C BEAM VERTICAL SHEAR

HORIZONTAL SHEAR

This type of shear is called “transverse” shear, and occurs if there is no bending stresses present.

In this case, beams are more like a deck of cards and bending produces sliding along the horizontal planes at the interfaces of the cards

It is easy to imagine vertical shear on a beam that was made up of concrete blocks

Almost all real beams have bending stresses present.

DESIGNING WITH FORCES Designers often rely on one of these key methods to help structures withstand forces: Distribute the load throughout the structure so that no single part is carrying most of the load.

Direct the forces along angled components so that the forces hold pieces together instead of pulling them apart.

Shape the parts to withstand the specific type of force they are likely to experience.

Structures can be strengthened by using materials that are appropriate for their function