Space Frames - Analysis.

The analysis of space frames results in the production of large sets of linear simultaneous equations which must inevitably require the use of a computer for their solution. For these equations to be formulated it is necessary to input into the  computer significant amounts of information relating to the topology of the structure and properties of the individual members. This operation can be very time- consuming unless modern pre-processing techniques which allow rapid data  generation are adopted.

The members forming double-layer space frames are principally stressed in  either axial tension or axial compression. Consequently it is usual in the analysis  of double-layer space trusses to assume that the members in the structure are  pin-jointed, irrespective of the actual joint rigidity.This assumption may lead to the overestimation of node deflections, but because only three degrees of freedom are permitted at each node this approach minimizes computer storage requirements and processing time.

Single-layer grid and barrel vault structures carry the imposed load by flexure of the members so it is important to include in the analysis the flexural, torsional and shear rigidity of the members. Linear analysis only is required  for the majority of skeletal space structures but to ensure stability of shallow domes it is essential to undertake a non-linear analysis of these structures.Large-span space structures may benefit from a full collapse analysis where the ultimate load-carrying capacity and collapse behaviour of the structure are determined.

The behaviour of both single-layer and double-layer space trusses is influenced to a great extent by the support positions of the structure. The effects of joint and overall frame rigidity also have a commanding influence and affect the buckling behaviour of the compression members within the structure. Great care must be taken in assessing the effective lengths of compression members and it is unlikely that internal and edge compression members will exhibit similar critical buckling loads.

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