Technology & Engineering
Space Truss
A space truss is a structure composed of linear elements connected at joints to form a stable framework. It is commonly used in engineering and architecture to create lightweight, yet strong, structures such as bridges, roofs, and towers. The design of a space truss allows for efficient load distribution and can be tailored to specific structural requirements.
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6 Key excerpts on "Space Truss"
eBook - PDF- Aslam Kassimali(Author)
- 2021(Publication Date)
- Cengage Learning EMEA(Publisher)
In this chapter, we extend the matrix stiffness formulation, developed for plane structures, to the analysis of three-dimensional or space structures. Three types of space-framed structures are considered: Space Trusses, grids, and space frames, with methods for their analysis presented in Sections 8.1, 8.2, and 8.3, respectively. The computer programs for the analysis of space-framed structures can be conveniently adapted from those for plane structures, via relatively straight- forward modifications that should become apparent as the analysis of space structures is developed in this chapter. Therefore, the details of programming the analysis of space structures are not covered herein; they are, instead, left as exercises for the reader. 8.1 Space TrussES A Space Truss is defined as a three-dimensional assemblage of straight pris- matic members connected at their ends by frictionless ball-and-socket joints, and subjected to loads and reactions that act only at the joints. Like plane trusses, the members of Space Trusses develop only axial forces. The matrix stiffness analysis of Space Trusses is similar to that of plane trusses developed in Chapter 3 (and modified in Chapter 7). The process of developing the analytical models of Space Trusses (and numbering the degrees of freedom and restrained coordinates) is essentially the same as that for plane trusses (Chapter 3). The overall geometry of the Space Truss, and its joint loads and displacements, are described with reference to a global Cartesian or rectangular right-handed XYZ coordinate system, with three global (X, Y, and Z) coordinates now used to specify the location of each joint. Furthermore, since an unsupported joint of a Space Truss can translate in any direction in the three-dimensional space, three displacements—the translations in the X, Y, and Z directions—are needed to completely establish its deformed position.
eBook - ePub- Bjørn N. Sandaker, Arne P. Eggen, Mark R. Cruvellier(Authors)
- 2019(Publication Date)
- Routledge(Publisher)
Longer spans and heavier loads incited by the rapidly expanding railway transportation system called for efficient and reliable structures. The development of the truss, therefore, primarily took place in civil engineering structures; in architecture, both spans and loads were usually smaller and did not encourage the formal development of trusses to the same degree. Besides, tradition, style, and custom weighed more heavily on architectural practice than on that of engineering, partly explaining why truss forms in general were slow to be admitted into “high-end” architecture. A relatively early example of a systematic use of trusses as both load-bearing structure and expressive architectural element, however, can be found in the Crystal Palace built for the World’s Fair of 1851, where both wrought and cast iron trussed beams were used in a large-scale building, albeit a temporary one. (Ill. 9.6.) Illustration 9.5 Trajan’s Column, Rome, Italy (113 AD). Relief detail shows braced form of wooden frames used for railings of pontoon bridge having closely spaced boat supports. Illustration 9.6 Crystal Palace, London, UK (1851). The shorter trusses of 7.2m (24ft) span were made of cast iron, while the longest spans (21.6m or 72ft) were executed in the more bending-resistant material of wrought iron. Designer: Joseph Paxton. Structural engineer: Fox and Henderson. But just what, exactly, is this thing we call a truss? We may begin to answer this question by saying that at its most basic a truss is a structure that is made up of linear elements arranged into triangular configurations. (e.g., Fig. 9.1.) Since a triangle is a stable structural form overall – that is, the triangle will not significantly be deformed when external forces are applied to it in any direction within its plane – then such an arrangement provides a highly effective geometric framework to build upon
eBook - PDFEngineering Mechanics
Problems and Solutions
- Arshad Noor Siddiquee, Zahid A. Khan, Pankul Goel(Authors)
- 2018(Publication Date)
- Cambridge University Press(Publisher)
Chapter 6 Analysis of Trusses 6.1 Introduction Engineering structures are built by joining large number of members to support heavy loads. These are broadly classified as truss, frame and machine, depending upon loading conditions and applications. Truss is built up by joining various prismatic bars at different joints. The members may be of different cross-sections like angle section, channel section or circular section, etc. Trusses are called economic structure as these can support heavy load over the large span. The examples of trusses are mobile or electrical transmissions towers, bridges and roof truss, supporting roof of buildings and workshops, etc. 6.2 Classification of Trusses Trusses are broadly classified in two categories: a. Depending upon joining of members in planes: Two-Dimensional Truss: This type of truss is also called plane truss as its all members lie in one plane. Thus, it can be considered as a structure of coplanar members. Bridges and roof trusses are examples of this type of truss. Three-Dimensional Truss: This type of truss is also called Space Truss and its all members lie in different planes. It is a structure which consists of collection of non-coplanar mem-bers. Mobile or electrical transmission towers are examples of this type of truss. b. Depending upon quantity of members and joints: Perfect Truss: This type of truss does not change its shape under external loading. It utilizes the optimum numbers of members and joints. It is considered as just rigid truss because removal of any member can cause failure of the truss. 246 Engineering Mechanics Mathematically the condition for a perfect truss is m = (2 j − 3) Consider Fig. 6.1 where m = 9 and j = 6 (2 j − 3) = (2 × 6 − 3) = 9 As equality exist between ‘ m ’ and ‘(2 j − 3)’ it called perfect truss. Imperfect Truss: This type of truss does not retain its shape under external loading due to joining of fewer members as compare to perfect truss.
eBook - PDFApplications of Space Developments
Selected Papers from the XXXI International Astronautical Congress, Tokyo, 21 — 28 September 1980
- L. G. Napolitano(Author)
- 2013(Publication Date)
- Pergamon(Publisher)
KEYWORDS spacecraft 9 truss, platform, antenna, module, deployable, erectable, buckling INTRODUCTION It is anticipated that future space missions will involve spacecraft which are ex-tremely large compared to those in use today. Potential missions being considered require spacecraft ranging in size from state-of-the-art antennas to futuristic, kilometer size solar power satellites. The aerospace community faces a major challenge to devise ways to accomplish these missions. Extremely high mission complexity and resultant cost dictates that concepts be developed which permit mission accomplishment in the most efficient manner. This will require that space-craft ma88 transported to orbit be reduced to a minimum. Spacecraft must be de-signed for efficient packaging in Shuttle for transport to orbit. Mission require-ments affecting spacecraft structural design must be examined in conjunction with 179 180 H. G. Bush and W. L. Heard, Jr. Shuttle constraints to Insure that the most desirable spacecraft concept Is Iden-tified. Previous studies identified trusses as a candidate low-mass structural class which meets the requirements of many future missions. These studies encompassed trusses which were either deployed (unfolded on-orbit), erected (assembled on-orbit), space fabricated (manufactured and assembled on-orbit), or made function-al by a combination of these methods. It is desirable to understand the applica-tion limits of each concept to permit selection of the simplest technique that meets mission requirements. The purpose of this paper is to present selected re-sults from (1) recent LaRC sizing studies which Identify efficient structural proportions and application limits of deployable and erectable structure concepts, (2) supporting analytical developments which are applicable to reticulated struc-ture design in general, and (3) spacecraft assembly studies for both modular and erectable concepts.
eBook - PDFManual of Structural Design
Structural Principles - Suitable Spans - Inspiring Works
- Eberhard Möller(Author)
- 2022(Publication Date)
- DETAIL(Publisher)
The formal relationship between trusses (German: Fachwerkträger) and half-timbered houses (German: Fach- werkhäuser) is obvious. Regarding the bearing behaviour, however, there are simi- larities – for example, the stiffening effect of triangles – as well as differences. Applications Trusses have frequently proven themselves ideally suited for spanning large areas with- out the need for columns. Such buildings include halls for sports, industrial fairs and railway stations, museum exhibit spaces, storage and factory areas, airport terminals and hangars (Fig. C 1.7, C 1.9 a). Trusses are also often used in bridge structures, high-voltage power line pylons and con- struction cranes (Fig. C 1.13). However, they are not used only in the building sector. In many other engineering fields such as vehicle manufacture, aircraft construction and space travel, designers rely on these relatively lightweight, efficient structures (Fig. C 1.10). Often, in construction as well as in machine production, trusses are concealed behind cladding. Today, computer-assisted anal- ysis techniques such as the Finite Element Method (FEM) make it possible to use multiple statically indeterminate construc- tion types and structural principles that were considered computationally intracta- ble until the mid 20th century. In the mass production of vehicles, these more complex structures have now largely supplanted the analytically simple, statically determinate truss (Fig. C 1.11). Rules for forming trusses The fundamental element of the truss is the triangle. In general, planar trusses can be formed in three ways. The basic method is to connect two members to the nodes of a beam or an existing truss such that a new triangle is formed (Fig. C 1.8). A planar truss may also be built by joining two existing trusses together via a suspen- sion rod and a common hinge or via three suspension rods whose lines of action are neither all parallel nor intersect at a point.
eBook - PDFForm and Forces
Designing Efficient, Expressive Structures
- Edward Allen, Waclaw Zalewski(Authors)
- 2012(Publication Date)
- Wiley(Publisher)
Whether in two or three dimensions, each member of a truss works axially, either in tension or compression. Because of the efficiency of axially acting members, trusses can span long distances and are economical of structural material. Trusses can span farther than beams and rigid frames, but not as far as cable struc- tures and arches. The usual range of truss spans is from 20 ft to 300 ft, though spans longer than this are possible. Trusses are readily designed to carry heavy loads and unusual distributions of loads. A truss gen- erally uses less material than a beam that would do the same job. However, the cost saving on material must be weighed against the additional labor required to make a truss. An advantage of a truss over a cable or arch is its capability to sustain many different load distribution patterns without significantly changing its shape. For this reason, trusses are often used as deck structures in suspension bridges to distribute concentrated loads to the cables and to restrain the cables against changing shape as loading patterns shift. Arches are often trussed to give them increased efficiency and greater resistance to buckling and change of shape (Figure 6.10). Trusses are often custom-designed, as in our camp building example, so as to give them shapes or structural properties appropriate for particular bridges or buildings. There are also many types of standard- ized trusses available “off the shelf” for use in floors and roofs, such as open-web steel joists (also called bar joists) and steel joist girders for use in industrial, com- mercial, and institutional buildings, and wooden roof trusses and floor trusses for residential-scale buildings (Figures 6.11–6.14). Standardized trusses are almost always designed for relatively light loadings that are uniformly distributed over the span. Trusses for Bridges There are several ways to use trusses in bridges (Figure 6.15).
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