Truss structure

For purposes of this specification, stresses in the individual members of a latticed or trussed structure resulting from elastic deformation and rigidity of joints are defined as secondary stresses. These secondary stresses may be taken to be the difference between stresses from an analysis assuming fully rigid joints, with loads applied only at the joints, and stresses from a similar analysis with pinned joints. Stresses arising from eccentric joint connections, or from transverse loading of members between joints, or from applied moments, must be considered primary stresses. 

Derrick supported. Support is provided by a steel trussed structure that supports one or more flare risers. 

Key words cellular metals, metallic foam, open- and closed-cell foam, hollow-sphere foam, optimized truss structures, honeycomb. 

Cellular solids are a class of materials with low densities and novel physical, mechanical, thermal, electrical, and acoustic properties. Low-density cellular metals can feature a wide variety of topologies to include open-cell foam, closed-cell foam, hollow-sphere foam, periodic/optimized truss structures, and honeycomb. Metallic foams consist of air dispersed in a solid matrix, similar to polymer foams such as polystyrene or food foams such as whipped cream. Closed-cell foams feature solid faces such that each cell is independently sealed from its neighboring cells, whereas open-cell foams (also known as porous metals, metal sponges and truss-type materials) do not contain cell walls they only have cell edges. Hollow-sphere foams consist of an assembly of individual hollow spheres. 

Optimized truss structures are produced in a similar fashion to open-cell foams. Virtually any castable alloy can be used to form a trass structure (Federal... 

The relative strength of hollow-sphere foams lies between the theoretical performance of open- and closed-cell foams. The performance of optimized truss structures is similar to that of closed-cell foams and, for the Kagome truss, approaches the behavior of a Hashin-Shtrikman porous material. Honeycombs are the most efficient structures when loaded purely out-of-plane. However, plastic buckling can decrease its performance at low relative densities. Further, since honeycomb is highly anisotropic, any inplane loading results in severely reduced performance. Although the theoretical performance of closed-cell foams far exceeds that of open-cell foams, processing defects result in commercially available material that behaves similar to an open-cell material at low relative densities. Commercially available samples of other types of low-density metallic structures behave nearly as predicted. [17]... 

Tank walls are thick (t5rpically 20 mm) if the design pressure is high (non atmospheric tanks), and therefore the rigidity of the shell is significant. The deformable parts of a pressure tank subject to seismic excitation are, instead, the supporting truss structure (or the support saddles) and the contained liquid, thereby causing the whole structure to behave like a double pendulum. 

The floating roof of the full scale tank is realized through a truss structure, which sustains steel plates. In order to maintain the mass ratio, the floating roof of the mock-up has been realized with a wood structure (Figure 12b). The gasket, which in the fuU scale tank is composed by a more complex mechanism, has been here realized with a rubber tube applied along the circumference of the roof. 

Table 5.20 Axial pull-out load of a tubular FRP section in the case of a moulded joint of a truss structure.

The frame-truss structures allow uniaxial members to carry stresses in their preferred directions. Studies of reinforced plastic trussed-web girders showed that joints can reduce the strength of a composite member by over 50%. Additional areas of investigation are the interfaces between the bulkhead and strut and between the strut and bedrock. 

A typical example is found in a space truss structure proposed by the Jet Propulsion Laboratory [46]. A stacked PMN actuator was installed at each truss nodal point and operated so that unnecessary mechanical vibration was suppressed immediately. A Hubble telescope has also been proposed using multilayer PMN electrostrictive actuators to control the phase of the incident light wave in the held of optical information processing (Fig. 4.1.25) [47]. The PMN electrostrictor provided superior adjustment of the telescope image because of negligible strain hysteresis. 

Ferrotti, G., Fabbri, F., 8 September 1992. Method for production of nodes for tubular truss structures. Patent US 5,144,830. 

Osterberg, D.A., 12 September 2003. Strut and node assembly for use in a reconfigurable truss structure. Patent WO 03/074803 Al. 

Figure 11.1 (a) An example of triangulated truss structure where the wood is in compression, the steel wire is in tension, with metal brackets as transition pieces, (b) An example of triangulated truss structure, where steel mbes are in compression, and steel rods are in tension, (a) Boeing (1916) structure photo by the author, (b) Boeing B-40 (1925) structure, photo by the author. 

Luh, G.C. Chuen, C.H. 2004. Multi-Objective optimal design of truss structure with immune algorithm . Computers and Structures, 82, pp. 829-844. 

As mentioned in Sect. 5.2.2, the feedthrough term Du becomes important, for example in the case of active struts in truss structures where piezoelectric stacks are placed in series with force transducers. 

Vaillon, L. Petitjean, B. Frapard, B. and Lebihan, D. Active isolation in space truss structures from concept to implementation. Smart Mater. Struct., 8 (1999), pp. 781-790... 

Chen, G. S., Rruno, R. J., Salama, M. (1991). Optimal placement of active/passive members in truss structures using simulated annealing. AIAA Journal, 29(8), 1327-13 34. doi 10.2514/3.1073 9... 

Determination of initial dimension for the supporting structures including guide piles and truss structures... 

AQWA is ignored. The calculated external loads, occurring once in 30, 50, 100, 300, 500, 1 000, 3 000, 5 000 and 10 000 years, are shown in Table 2. This study are considered the environmental loads applied to the floater, not including seabed truss structures. As a future study, the current load applied to the seabed structures should be taken into account for the structure design. 

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