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a Alternate coefficient 6r — 2.1 can also be used. b he, height of the elevated structure.

a Alternate coefficient 6r — 2.1 can also be used. b he, height of the elevated structure.

well as the geometry of members adjacent to the support, all contribute to minimizing the effect of thermal expansion. The temperature effect of a space frame may be calculated by the ordinary matrix displacement method of analysis, and most computer programs provided such a function.

For double-layer grid, if it satisfies one of the following requirements, the calculation for temperature effect may be exempted:

1. The joints on supports allow the double-layer grid to move horizontally.

2. Double-layer grids of less than 40 m span are supported along perimeters by independent reinforced concrete columns or brick pilasters.

3. The displacement at the top of the column due to a unit force is greater or equal to the value calculated according to the following formula:

where L is the span of the double-layer grid in the direction of checking temperature effect, E is the modulus of elasticity, A is the arithmetic mean value of the cross-sectional area of members in the supporting plane (top or bottom-layer), a is the coefficient of thermal expansion, Dt is the temperature difference, [s] is the allowable stress of steel, and X is a coefficient: when the chords in the supporting plane are arranged in orthogonal grids, X = 1, in diagonal grids, X = 2, and in three-way grids, X = 2.

24.4.1.5 Construction Loads

During construction, structures may be subjected to loads different from the design loads after completion, depending on the sequence of construction and method of scaffoldings. For example, a space frame may be lifted up at points different from the final supports or it may be constructed in blocks or strips. Therefore, the whole structure, or a portion of it, should be checked during various stages of construction.

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