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COLLEGE OF ARCHITECTURE AND PLANNINGDepartment of Architecture and Building Sciences

Dr. Mohammed Ghonim

11. SPACE FRAMES CONSTRUCTION

ARCH 436Contemporary Building Construction Methods

Lecture ObjectivesUpon completion of this lecture, the student will be able to:

1. Explain the concept of space frames.

2. Discuss the advantages of space frames.

3. Classify the types of space frames.

4. Estimate the dimensions of a space frame.

5. List & describe the erection methods of space frames.

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Lecture Content

• Introduction.

• Historical Background.

• Applications of Space Frames.

• Advantages of Space Frames.

• Structural Background.

• Types of Space Frames.

• Space Frames Components.

• Types of Space Frame Connections.

• Mero Space Frame System.

• Design Considerations for Double-layer flatSpace frames.

• Space Frame Methods of Erection.

• Scaffold Method.• Block Assembly Method.• Lift-up Method.

IntroductionIn architecture and structural engineering, a space frame or space structure is a truss-like,lightweight rigid structure constructed from interlocking struts in a geometric pattern.Space frames can be used to span large areas with few interior supports. Like the truss, aspace frame is strong because of the inherent rigidity of the triangle;flexing loads (bending moments) are transmitted as tension and compression loads alongthe length of each strut.

a space frame is strongbecause of the inherentrigidity of the triangle, Thesimplest spatial unit of aspace frame is atetrahedron having fourjoints and six structuralmembers.

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IntroductionThe simplest form of space frame is a horizontal slab of interlocking squarepyramids and tetrahedra built from aluminium or tubular steel struts. In many ways thislooks like the horizontal object of a tower crane repeated many times to make it wider.A stronger form is composed of interlocking tetrahedra in which all the struts have unitlength. More technically this is referred to as an isotropic vector matrix or in a single unitwidth an octet truss. More complex variations change the lengths of the struts to curve theoverall structure or may incorporate other geometrical shapes.

The simplest form of space frame is ahorizontal slab of interlocking squarepyramids & tetrahedra

Historical BackgroundSpace frames were independently developed by Alexander Graham Bell around 1900and Buckminster Fuller in the 1950s. Bell's interest was primarily in using them to make rigidframes for nautical and aeronautical engineering, with the tetrahedral truss being one of hisinventions, however few of his designs were realized, while, Fuller's focuswas architectural structures and his work had greater influence.

Fuller’s Dome, Expo ‘67, Montreal, Canada Alexander Graham Bell Tetrahedrals

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Applications of Space Frameswe can use a space frame truss for a platform or overhead structure that spans largedistances without need for internal load bearing support.

In the past few decades, the spread of space frame was mainly due to its great structuralpotential and visual beauty. New and imaginative applications of space frames are beingdemonstrated in the total range of building types, such as sports arenas, exhibition pavilions,assembly halls, transportation terminals, airplane hangars, workshops, and warehouses.They have been used not only on long-span roofs, but also on mid- and short-spanenclosures as roofs, floors, and exterior walls. Many interesting projects have been designedand constructed all over the world using a variety of configurations.

Dammam municipality building, KSA. Al Andalus Mega Mall, Jeddah, KSA.

Advantages of Space Frames

Factor Description1. Lightweight This is mainly due to the fact that material is

distributed spatially in such a way that the loadtransfer mechanism is primarily axial; tensionor compression. Consequently, all material inany given element is utilized to its full extent.Furthermore, most space frames are nowconstructed with aluminum, which decreasesconsiderably their self-weight.

2. MassProductivity

Space frames can be built from simpleprefabricated units, which are often of standardsize and shape. Such units can be easilytransported and rapidly assembled on site bysemi-skilled labor. Consequently, space framescan be built at a lower cost.

3. Stiffness A space frame is usually sufficiently stiff inspite of its lightness. This is due to its three-dimensional character and to the fullparticipation of its constituent elements.

4. Versatility Space frames possess a versatility of shapeand form and can utilize a standard module togenerate various flat space grids, latticed shell,or even free-form shapes. Architectsappreciate the visual beauty and theimpressive simplicity of lines in space frames.

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Structural Background

A space frame Is a long-spanning three-dimensional plate Structure based on the rigidity ofthe triangle and composed of linear elements subject only to axial tension or compression,even in the case of connection by comparatively rigid joints, the influence of bending ortorsional moment is insignificant.

Visualizing compression and tension from deformed shape, loads applied only at joints.

The depth and module size of double-layer grids areusually determined by practical experience. In some of thepapers and handbooks, figures on these parameters arerecommended, and one may find that the difference isquite large. For example, the span–depth ratio varies from12.5 to 25, or even more. It is usually considered that thedepth of space frame can be relatively small whencompared with more conventional structures.

Types of Space Frames

According to curvature

1- Flat covers

These structures are composedof planar substructures. Theplane are channeled through thehorizontal bars and the shearforces are supported by thediagonals.

2- Barrel vaults

This type of vault has a crosssection of a simple arch. Usuallythis type of space frame doesnot need to use tetrahedralmodules or pyramids as a part ofits backing.

3- Spherical domes

These domes usually require theuse of tetrahedral modules orpyramids and additional supportfrom a skin.

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According to the number of grid layers

1- Single-Layer

All elements are located on thesurface to be approximated.

2- Double-Layer

The elements are organized intwo parallel layers with eachother at a certain distance apart.The diagonal bars connectingthe nodes of both layers indifferent directions in space.

3- Triple-Layer

Elements are placed in threeparallel layers, linked by thediagonals. They are almostalways flat. This solution is todecrease the diagonal memberslength.

Types of Space Frames

Space Frames Components

1- Members

2- JointsIn a space frame, connecting joints play animportant role, both functional and esthetic,which derives from their rationality duringconstruction and after completion. Sincejoints have a decisive effect on the strengthand stiffness of the structure and composearound 20 to 30 percent of the total weight,joint design is critical to space frameeconomy and safety.

In common, members are axial elementswith circular or rectangular sections, allmembers can only resist tension orcompression. The space grid is built ofrelatively long tension members and shortcompression members.A trend is very noticeable in which thestructural members are left exposed as apart of the architectural expression.

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1- Welded Connection 2- Bolted Connection 3- Threaded Connection

Types of Space Frame Connections

Mero Space Frame SystemThe Mero connector, introduced in 1948 by Dr. Mongeringhausen, proved to be extremelypopular and has been used for numerous temporary and permanent buildings. Its jointconsists of a node that is a spherical hot-pressed steel forging with flat facets and tappedholes. Members are circular hollow sections with cone-shaped steel forgings welded at theends, which accommodate connecting bolts.

The Mero connector was originally developed for double-layer grids. Due to the increasinguse of non-planar roof forms, it is required to construct the load-bearing space frameintegrated with the cladding element. A new type of jointing system called Mero Plus Systemwas developed so that a variety of curved and folded structures are possible.

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Design Considerations for Double-layer flat Space frames

Space Frame Methods of ErectionThe method chosen for erection of a space frame depends on its behavior of loadtransmission 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 methodof jointing the individual elements, and the strength and rigidity of the space frame until itsform is closed must all be considered.

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Space Frame Methods of Erection1- Scaffold MethodIndividual Elements are Assembled in Place atActual Elevations, members and joints orprefabricated subassembly elements areassembled directly on their final position. Fullscaffoldings are usually required for this type oferection. Sometimes only partial scaffoldingsare used if cantilever erection of space framecan be executed. The elements are fabricated atthe shop and transported to the constructionsite, and no heavy lifting equipment is required.

Space Frame Methods of Erection2. Block Assembly MethodThe space frame is divided on its plan into individual strips or blocks. These units arefabricated on the ground level, then hoisted up into its final position and assembled on thetemporary supports. With more work being done on the ground, the amount of assemblingwork at high elevation is reduced. This method is suitable for those double-layer grids wherethe stiffness and load-resisting behavior will not change considerably after dividing into stripsor 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 capacityavailable.

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Space Frame Methods of Erection3. Lift-up MethodThe whole space frame is assembled at ground level so that most of the work can be donebefore hoisting. This will result in increased efficiency and better quality. For short andmedium spans, the space frame can be hoisted up by several cranes. For long-span spaceframe, temporary posts are used as the support and electric winches as the lifting power. Thewhole space frame can be translated or rotated in the air and then seated on its final position.This method can be employed to all types of double-layer grids.

Summary• A space frame or space structure is

a truss-like, lightweight rigid structureconstructed from interlocking struts ina geometric pattern.

• Space frame truss can be used for aplatform or overhead structure thatspans large distances without need forinternal load bearing support.

• Space frames are advantageouscompared to other common structuresby their; light weight, massproduction, stiffness, and versatility.

• Space frames are classified into threetypes according to the number of gridlayers as follows; single, double, ortriple layer.

• Space frame connections can be madeby; welding, bolting, or threading.

• Space frame construction utilize threemain methods of erection; 1- scaffoldmethod, 2. block assembly Method, 3.lift-up method.

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References

Allen, Edward & Lano, Joseph (2009) Fundamentals of Building Construction: Materials andMethods, John Wiley & Sons.

Chen W.F. & Lui E.M. (2005) “Handbook of Structural Engineering”, CRC Press, USA.

Chilton, John (2000) “Space Grid Structures”, Architectural Press. Ching, Francis (2008) Building Construction Illustrated, John Wiley & Sons. Mehta, Madan et. al. (2013) “Building Construction”, Pearson, USA.

http://en.wikipedia.org http://youtube.com

Lecture ActivityEach student is required to prepare a brief but informative internet-based research about one of the topicsrelated to this lecture (Space Frames Construction); i.e., new developments, successive and local casestudies or important details. The research should be presented in only one A4 sheet.