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Abstract— over the last half-century, there is a growing interest in the space frame structures. The need for a structure to accommodate large unobstructed areas resulted in the development of space frame structures. Also it satisfies the requirements of lightness, economy and speedy construction. There was significant progress in its development due to its great structural potential and visual beauty.

I. INTRODUCTION

Many extraordinary projects have been designed and constructed all over the world using a variety of configurations. The need for large indoor space for public interaction, human activities is one of the reason. Therefore, sport tournaments, cultural performances, mass assemblies, and exhibitions could be held under one roof by means of space frames. There is also demand for a space that has minimum interference from internal supports.They are highly statically indeterminate, but due to its complicated analysis, it is been limited. The space frame has large number of members connected together at different angles at a single point. But due to several connecting methods, it has greater efficiency. Alexander Graham Bell, the inventor of the telephone, was one of the first to appreciate the merits of space frames and apply them in actual construction. In fact, he built one of the early versions of a flying machine using a multi-layered space frame concept. Also due to its lightness and structural efficiency that would add as an advantage in aircraft structures than in buildings.

II.HISTORY

Space frames were independently developed by Alexander Graham Bell around 1900 and Buckminster Fuller in the 1950s.Bell's interest was primarily in using them to make rigid frames for nautical and aeronautical engineering, with the tetrahedral truss being one of his inventions. However few of his designs were realized. Buckminster Fuller's focus was architectural structures; his work had greater influence. Introduction of the first space grid system called MERO in 1943 in Germany initiated the use of space trusses in architecture.

III. DEFINING SPACE FRAME STRUCTURES

A Space frame is a structural system, assembled of linear elements so arranged that the loads are transferred in a three-dimensional manner. In some cases, the constituent elements may be two-dimensional. Macroscopically, a space frame often takes the form of a flat or curved surface.

A space frame is usually arranged in an array of single, double, or multiple layers of intersecting members. A single-layer space frame that has the form of a curved surface is termed as braced vault, braced dome, or latticed shell.

Figure 1: Grid pattern

A. Basic conceptThe space frame can be formed on either a flat or a curved surface. The earliest form is single-layer grid, which is formed by adding intermediate grids and including rigid connection to the joist and girder framing system. The main characteristic of grid construction is the omnidirectional spread of the load as opposed to the linear transfer of the load in an ordinary framing system. Since such load transfer is mainly by bending, for larger spans the bending stiffness is increased most efficiently by changing to a double-layer system. The load transfer mechanism of a curved surface space frame is essentially different from the grid system that is primarily membrane-like action.

IV. ADVANTAGE OF SPACE FRAMES

The space frames are light, structural efficient and use materials optimally. They are an elegant and economical means of covering large column-free spaces of hangars and

SPACE FRAMES Sheryl Susan, SEM VI student, KMEA College of Architecture

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assembly halls. They carry loads by three-dimensional action. Deflections are small because of the high inherent stiffness. Space frame are joined using precise, factory-made components, unskilled labour is adequate for their assembly and action. Services such as lighting and air conditioning can be integrated with space frames. Also these save construction time. They are light which facilitates transportation. Dead loads are very much less and there are consequent savings in columns and substructures.

V. COMPONENTS OF A SPACE FRAME

A space frame consists of axial members, which are preferably tubes, also known as circular hollow sections or rectangular hollow sections and connectors, which join the members together.

Figure 2: different connections

A. Members

The members of a space frame are either of aluminium or steel. Aluminium members are of light weight but are more expensive. The large majority of space frames use members of steel with a yield strength ranging from 210 to 450 MPa. The tubes may be electrically resistance welded or seamless.

B. Node connectors

Figure 3: Mero

C.MeroThe Mero connector, introduced some 50 years ago, proved to be extremely popular and has been used for numerous temporary and permanent buildings. Its joint consists of a node that is a spherical hot-pressed steel forging with flat facets and tapped holes. Members are circular hollow sections with cone-shaped steel forgings welded at the ends, which accommodate connecting bolts. Upto 18 members can be connected at a joint with no eccentricity.

VI. DIFFERENT TYPES OF SPACE FRAMES

A. Flat covers

These spatial structures are composed of planar substructures. Their behaviour is similar to that of a plate in which the deflections in the plane are channeled through the horizontal bars and the shear forces are supported by the diagonals.

B. Barrel vaultsThis 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.

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C.Spherical domesUsually require the use of tetrahedral modules or pyramids and additional support from a skin.

Figure 4: Plane covers

Figure 5: Barrel vault

Figure 6: Spherical dome

VII. DIFFERENT TYPES OF SPACE FRAMES ACCORDING TO THE NUMBER OF LAYERS

A. Single layerAll elements are located on the surface to be approximated.

B. Double layerThe elements are organized in two parallel layers with each other at a certain distance apart. Each of the layers form a lattice of triangles, squares or hexagons in which the projection of the nodes in a layer may overlap or be displaced relative to each other. The diagonal bars connecting the nodes of both layers in different directions in space.

C.Triple layerElements are placed in three parallel layers, linked by the diagonals. They are almost always flat.

VIII.TYPES OF ERECTION

A. Scaffold methodIndividual elements are assembled in place at actual elevationsMembers and joints or prefab subassembly elements are assembled on their final position. Full scaffoldings usually. Sometimes partial scaffolding are used if cantilever erection.Elements fabricated at the shop. Transported to the construction site, and no heavy lifting equipment is required.

B. Block assembly methodDivided on its plan into individual strips or blocks. These units fabricated on the ground level. Then hoisted upon into its final position and assembled on the temporary supports. Suitable for double layer grids.

C.Lift up methodThe whole space frame is assembled at the ground level so that most of the work can be done before hoisting. Increased efficiency and better quality.