Connections of wooden structures
(1) Tooth connection
Tooth connection transmits force directly between components, so tooth connection only applies At the nodes where compression members connect to other members.
Tooth connections include single-tooth connections and double-tooth connections (Figure 11-136), which should comply with the following regulations:
(1) The pressure-bearing surface of the tooth connection should be in line with the connected The axis of the pressure rod is vertical.
(2) The single-tooth connection should make the axis of the pressure rod pass through the center of the pressure-bearing surface.
(3) The upper chord axis and the support reaction line should intersect at one point with the center line of the lower chord net section; when logs are used, they can intersect with the center line of the lower chord gross section at one point.
(4) The tooth depth of the tooth connection should not be less than 20mm for square wood; and should not be less than 30mm for logs. The tooth depth of the truss support node should not be greater than h/3 (h is the member section height in the tooth depth direction); the tooth depth of the intermediate node should not be greater than h/4. In a double-tooth connection, the tooth depth hc of the second tooth should be at least 20mm greater than the tooth depth hc1 of the first tooth. The shear surface length of the first tooth of single and double teeth
should not be less than 4.5 times the tooth depth. When made of wet wood, the shear surface length of the node tooth connection of the wooden truss support should be longer than the calculated value. 50mm.
(5) When the truss support nodes are connected by teeth, insurance bolts must be installed. The safety bolt should be perpendicular to the upper chord axis.
(2) Bolt connection and nail connection
According to the number of shear planes passing through the connected components, it can be divided into single shear connection and double shear connection (Figure 11-137).
In bolted and nailed connections, the minimum thickness of connecting timber members shall comply with the requirements of Table 11-40.
Minimum thickness of wooden members in bolted and nailed connections Table 11-40
Note: c in the table - the thickness of the middle member or the thickness of the thicker member in a single shear connection ;
a——The thickness of the edge member or the thickness of the thinner member in a single shear connection;
d——The diameter of the bolt or nail.
(a) Double shear connection; (b) Single shear connection
4. Fire protection and protection of wooden structures
(—) Fire protection of wooden structures
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1. Combustion performance and fire resistance limit of building components
The combustion performance and fire resistance limit of wood structure building components should not be lower than those specified in Table 11-41.
Note: ① The roof surface layer should be made of non-combustible materials;
② When the same wooden structure building is composed of different heights, the lower part of the roof load-bearing components must be non-combustible. The fire resistance limit should not be less than 1.00h.
2. Number of stories, length and area of ??the building
Timber-frame buildings should not exceed three stories. The allowable length and fire protection zoning area of ??buildings with different floors should not exceed the requirements in Table 11-42.
Note: For wooden structures equipped with automatic sprinkler systems, the allowable length and area of ??each floor should be doubled on the basis of Table 11-40. When set locally, the allowable length and area of ??each floor should be doubled. calculate.
3. Fire separation distance
(1) The fire separation distance between wooden structures and between wooden structures and buildings with other fire resistance levels should not be less than the requirements in Table 11-43.
Note: The fire separation distance should be calculated based on the shortest distance between the exterior walls of adjacent buildings. When the exterior wall has protruding combustible components, it should be calculated from the outer edge of the protruding part.
(2) When there are no door or window openings in the exterior walls between two wooden structures or between a wooden structure and other structural buildings, the fire separation distance shall not be less than 4.00m.
(3) When the sum of the door, window and door areas of the exterior wall between two wooden structures or between a wooden structure building and other fire-resistant buildings does not exceed 10% of the area of ??the exterior wall, the The fire separation distance should not be less than the requirements in Table 11-44.
4. Combustion performance of materials
(1) The technical indicators of the combustion performance of building materials used in wooden structures should comply with the provisions of GB 8625 "Test Methods for Flame Retardancy of Building Materials".
(2) The fire resistance of indoor decoration materials, walls, ceilings, lighting windows, floors, etc. should be no less than flame retardant level B1.
(3) Pipes and coating materials or linings:
When the fluid in the pipe can cause the temperature of the outer wall of the pipe to reach 120°C or above, the pipe and its coating materials may The lining and the adhesive used during construction must be non-combustible materials. The fire resistance of pipes and their covering materials or linings whose outer wall temperature is lower than 120oC should not be lower than flame retardancy level B1.
(4) Filling materials: When various components or spaces in the building need to be filled with sound-absorbing, heat-insulating, and thermal insulation materials, the fire resistance of these materials should not be lower than flame retardancy level B1.
5. Heating and ventilation
(1) It is strictly prohibited to use open fire heating, open fire production operations and other facilities in wooden structures.
(2) Flues and chimneys used for heating or cooking , fire pits, etc. should be made of non-metallic, non-combustible materials, and should comply with the following regulations:
The wall thickness of the parts adjacent to the wooden components shall not be less than 240mm;
The wall thickness between the The clear distance is not less than 120mm, and there is good ventilation environment around it.
6. Skylight
A wooden structure building composed of parts of different heights. The skylight on the lower part of the roof is connected to the doors and windows on the outer wall of the higher part. The minimum distance between openings should not be less than 5.00m. When one of the following conditions is met, the distance may not be restricted;
(1) The skylight is equipped with an automatic sprinkler system or is a fixed Class B fire protection system. Windows:
(2) The door on the exterior wall is a Class B fire door that automatically closes in case of fire, and the windows and openings are fixed Class B fire windows.
7. Confined spaces
In wooden structure buildings, fire isolation measures should be taken in the following parts with confined spaces:
(1) In light wooden structure buildings, when the floor height is less than or equal to 3m, It is located between the wall stud columns and at the bottom of the beams of the floor and roof; when the floor height is greater than 3m, it is located between the wall stud columns, every 3m along the wall height, and at the bottom of the beams of the floor and roof.
(2) The connection between horizontal components (including roofs and floors) and vertical components (walls).
(3) The junction between the first step of the stairs and the floor.
(2) Protection of wooden structures
1. Moisture-proof and ventilation measures should be taken for the following parts of the wooden structure:
(1) Moisture-proof layers should be installed under the supports of trusses and girders.
(2) Pillars should be set up under wooden pillars, and it is strictly forbidden to bury wooden pillars directly in the soil.
(3) The support nodes of trusses, girders or other load-bearing wooden components that must not be enclosed in walls, insulation layers or in poorly ventilated environments (Figure 11-138 and Figure 11-139).
(4) Ventilation holes should be provided for wooden structures located in hidden parts of the house.
(5) The open-air structure should be constructed to avoid the possibility of water accumulation in any part, and gaps should be left between components (except for joints).
(6) When there is a large temperature difference between indoor and outdoor, effective insulation and steam isolation measures should be taken for the building envelope (including the insulated ceiling).
2. In addition to being explained in the design drawings, anti-corrosion and insect-proof measures for wooden structures should also be required to check the construction quality during the handover of relevant construction processes. If any problems are found, they should be corrected immediately.
3. In the following situations, in addition to structural ventilation and moisture-proof measures, chemical treatment should also be carried out.
(1) Open-air structure;
(2) Support nodes of internal drainage trusses;
(3) Purlins, joists, columns and other wooden structures Parts where components are in direct contact with masonry and concrete;
(4) Wooden components used in humid environments where termites are prone to breed;
(5) Masson pine and Yunnan pine are used in load-bearing structures Pine, slash pine, birch and wood from newly utilized tree species that are susceptible to decay or insect damage.
4. Commonly used chemical formulas and treatment methods can be adopted in accordance with the current national standard "Code for Acceptance of Construction Quality of Wood Structure Engineering" (GB 50206).
Notes: (1) Pest damage mainly refers to termites, beetles, mealybugs, beetles, etc.
(2) Practice has proved that asphalt can only prevent moisture and has poor anti-corrosion effect, so it should not be used alone.
5. When treating wooden components with anti-corrosion and anti-insect chemicals, the chemical composition, formula and treatment method specified in the design should be used. When the chemicals or treatment methods need to be changed due to restrictions, the consent of the design unit must be obtained. Under no circumstances may unqualified chemicals be used.
6． Mechanical processing of wooden components (including glulam components) should be carried out before chemical treatment. After wooden components have been treated with anti-corrosion and insect repellent, re-cutting or drilling should be avoided. Due to technical reasons, when it is necessary to make local repairs, the exposed surface of the wood must be coated with sufficient chemicals of the same brand.
7. When using chemical pressure treatment for anti-corrosion and insect-proofing of wooden structures, the amount and penetration of the chemical in the wood should meet the requirements stipulated in the design documents. If there is no provision in the design, it should comply with the minimum requirements stipulated in the current national standard "Code for Acceptance of Construction Quality of Wood Structure Engineering" (GB 50206).