Selection of the type and geometrical dimensions of the lattice trusses podstropilnyh

Podstropilnye farm projected in the vast majority of cases in the form of through-truss with parallel chords.

Only in exceptional cases, with large spans and low construction height (constrained by any production requirements, for which the plant is built) apply with a continuous vertical sheet.

Most advantageous lattice truss type for podstropilnyh, Supports one roof trusses, It is a diagonal grille with descending from the poles to the midspan braces.

With such a long grating all the elements - struts, tensile, Short same elements - racks, compressive. Since the compressed elements calculated buckling, it maybe advantageous to attach smaller length.

If are two or more trusses, triangular lattice with additional stanchions may be used, reduces the length of the compressed upper panel zone.

The choice of building height podstropilnoy farm (the distance between the belts) It is depending on the span truss.

If the building height podstropilnoy farm is not limited to any required dimensions of downstream structures or equipment, the choice of the height should be done in such a way, to get the smallest weight of metal elements in the farm podstropilnoy. Similarly,, as for the roof trusses, minimum weight of the metal takes place at a certain height, and the height is expressed in fractions of flight.

After establishing headroom and select the type of lattice produce breakdown zones on the panel. In most cases, for consistency of lattice elements and connecting strips, receiving panel equal in magnitude. Derogation from this rule is sometimes in cases, when podstropilnaya farm bears the load of the frame fachwerk walls. В этом случае, in order to avoid local bending of the lower belt, necessary to carry out the attachment of vertical elements fachwerk in knots podstropilnoy farm. Thus vertical elements fachwerk fix the position of the truss nodes, to which they are attached, and in this case, can not always be broken down into equal podstropilnoy farm panel. In any case, a symmetric breakdown about the middle of the span must be respected. number of panels are set in such a way, to the attachment points of the roof trusses necessarily coincide with the nodes of the beam podstropilnoy, and that the angle braces to belts was close to 45 ° and in any case not less than 30 °.