Wooden Structures - Polygonal Truss Calculation

Contents

1. Source Data

3. Calculation of polygonal truss

4. Brief Instructions for Fabrication and Installation of Coating Elements

5. Measures to protect structures from rot and fire

Literature

4. Brief Instructions for Fabrication and Installation of Coating Elements

Flooring designs depend on their purpose. Depending on the material of the roof, plank or bar flooring is used in the coating. In the coatings of heated buildings, a single board flooring is used to lay insulation. Boards are connected to each other in a bottomhole or in a quarter, their thickness is determined by calculation.

Under adverse climatic conditions, it is advisable to make wooden flooring and skins from shields prepared in advance at factories. The dimensions of the latter are set depending on the pitch of the runs, the height of the building floor, transportation and installation conditions. Boards of shields are sewn with nails using strips. Against wetting during construction, it is recommended to glue the outer face of the shields with a layer of bituminous cardboard, which will serve as vapor insulation. Boards are made manually and therefore it is not advisable to recommend them for mass construction.

Runs of coatings and suspended floors are designed from boards, bars or logs in the main form of single-span beams. In the covers of buildings of large length, with a small slope of the roof, continuous runs of paired boards or plates are used.

In cantilever and continuous runs from paired elements, joints are arranged in the span in the zone of the smallest bending moments under the assumption that the time load is evenly distributed over all runs. In continuous runs from paired joint elements, they are placed in a run-down at a distance of x = 0.21l from the support, i.e. each joint of one element is covered by a whole other element. Along the length of the run board they are connected with nails arranged in staggered order after 50 cm, and nails are installed in the joint according to the calculation.

5. Measures to protect structures from rotting and fire

When designing wooden structures, structural measures are provided to protect them from biological destruction, fire, etc.

Structural measures that ensure the protection and protection of elements of wooden structures from humidification are mandatory, regardless of the life of the building or structure. In the case where the wetting of wood during operation cannot be eliminated by structural measures, antisepting should be used.

Structural measures to protect wood from rotting should ensure:

waterproofing device from ground water, drain boards and visors for protection against atmospheric precipitation, etc.

sufficient thermal insulation (on the cold side), and if necessary waterproofing (on the warm side) of enclosing structures to avoid their freezing and condensation humidification.

Systematic drying of wood in closed parts of buildings by creating a drying temperature and humidity regime.

Wooden structures should be made open, well ventilated, as far as possible accessible in all parts of the building for inspection. It is not allowed to seal belts, support and intermediate units into walls, insulated coverings and other enclosing structures of heated buildings.

Coatings with wooden structures should be designed with an external discharge of atmospheric water. In the case of upper lighting, the lighting system shall exclude the possibility of wetting wooden structures.

Wood burning is a chemical process of its thermal decomposition, accompanied by the release of gases. By connecting to the oxygen of the air, they form a flame. With rapid heating, wood is ignited at t > 300 ° C, and with long-term t > 600 ° C. As the temperature rises, flame burning and charring of the upper layer begin.

Fire safety standards for buildings and structures set minimum fire resistance limits and maximum fire propagation. Wooden slabs, floorings and slabs, as well as elements of curtain panels of walls are treated with flame retardants.

Improve fire safety of wooden structures by structural and chemical measures, and in some cases by combining them.

Constructive measures are to create conditions under which the spread of the fire is blocked and the fire resistance limit increases. This is the arrangement of fire walls or non-combustible sections of floors and coatings, the separation of hollow coatings with non-combustible diaphragms, the area between which should not exceed 54 m2, the arrangement of non-combustible preparations for chimneys and furnaces.

Chemical fire protection measures reduce the fireability of wood. This is impregnation of wooden elements with flame retardants, application of plaster-like coatings and sheet of non-combustible and difficult-to-burn materials, inorganic and organic paints on the surface.

Comprehensive protection of wood is the most promising direction, especially for glued structures of industrial manufacture.

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