CHOOSING A RATIONAL SCHEME OF ROOF TRUSSES WITH CURVILINEAR BELTS

Abstract

The results of a static calculation of an arched-type steel truss with curvilinear belts are given.

The rational overall parameters of steel trusses are determined depending on the size and scheme of application of loading and span, namely height in the middle of span and radii of rounding of belts; influence of rigidity of nodes and elements of the lattice on the general stress-strain state of the farm was studied; the arched-type steel farm was calculated with curved perforated belts spanning 30 m.

With the help of PC "Lyra" it is established that the most disadvantageous loading of this farm is the node application of load on the whole span. The required number of supports is determined and the rational distance between them is selected. It is found that a farm of this type works best on four supports, two of which are located at the edges and the other two at a distance of 5.45 m from the extreme supports inside the span. It is noted that such a farm works almost equally in the case of rigid and hinged joints of lattice elements with belts and with different rigidities of lattice elements.

Preliminary calculations showed that rational, in terms of steel costs, the height of the farm of this type in the middle of the span is 1.55 m. Farms with higher heights are irrational, since significantly increases the length of the belts and lattice elements, which leads to a decrease in their stability and increase the weight of the farm itself, and the forces in the belts and lattice elements with increasing the height of the farm are reduced by a small amount.

The study of the operation of such farms in the middle of the span of 1.05 m, 1.55 m and 2.05 m in the case of loading through a node with a load greater than 2 times, resulting in the fact that the forces in the belts and elements of the lattice is practically no are different compared to the boot case at each node.

The analysis of the work of farms of this type and with a smaller number of elements of the lattice, that is, the rod lattices were attached to the belts through the node compared to the previous case and the load was also 2 times greater.

The work of farms with fewer lattice elements was investigated when applying a single load to nodes and between nodes at the same time. The values of the efforts compared to the previous case were compared and stated that they are practically the same.